Display system having electrode modulation to alter a state of an electro-optic layer

Display system with an electrode module to change the state of an electro-optic layer

Background of the invention

The present invention is a continuation of U.S. Patent Application No. 08/770,223 jointly filed by the same applicant on December 19, 1996, and its name is "Display System with Common Electrode Modulation". This application requests this earlier filing date in accordance with 35U.SC§120.

The present invention generally relates to a display system, such as a liquid crystal display system. The present invention also relates to a system for providing electronic driving of electrodes of a display system. More particularly, the present invention relates to a system that can electronically drive the electrodes of a display system in a controlled phase relationship with the update of pixel data.

One type of display system operates by electronically addressing a thin, interposed layer of optoelectronic material (such as a liquid crystal) between two substrates. In these display systems, it is important to obtain good display characteristics. Such characteristics include: color purity, high contrast, high brightness and fast response.

The high independence of the frame or sub-frame can eliminate the coupling of intensity values from one frame to the next under a given pixel. For example, if a pixel is set to its brightest gray during the first frame, and then set to the darkest gray during the next frame, a high degree of independence can ensure this possibility, and Low independence will make the pixel appear brighter than the darkest gray during the second frame. This coupling can cause problems such as smearing of motions. Regardless of whether the display is color or black and white (monochrome) or a gray scale display, high frame-frame independence is very important.

The available contrast level is determined by the intensity range between the brightest grayscale and the darkest grayscale of a given pixel within a given frame or sub-frame.

In addition to contrast, it is also hoped that the display can display bright images, because brighter images are considered to be of higher quality for users.

Finally, the display speed is determined by its ability to display one frame after another at a high rate. In the case of displaying visible actions, only a way to display a full-color frame at a rate of at least 30 Hz, preferably at a rate of 60 Hz or faster, can avoid flickering and other problems.

If a pixel position of the display does not contain a red, green, and blue pixel (in other words, the red, green and blue sub-pixels of each pixel position), but only a single color, the speed requirement becomes even greater. It's important. One type of this type of display is as discussed in Sayyah, Forber and Efrom in SID Digest (1995) pages 520-523 "Projector-based color sequential silicon crystal LCLV for consumer HDTV" Color sequential LCD display. In this type of display, if a display requires sequential display of red, green and blue sub-pixels, these sub-frames must be displayed at a rate higher than 90 Hz, preferably higher than 180 Hz, to avoid flicker. For color sequential displays, if you want to display images with good color purity, you should require high frame or sub-frame independence.

Any display system that operates by electronically addressing a thin, intervening layer of optoelectronic material (such as a liquid crystal) placed between two substrates has the following characteristics. At least one pair of light among the two substrates is transparent or semi-transparent, and one substrate includes many pixel electrodes. Each pixel electrode corresponds to a pixel (or a sub-pixel) of the display, and each pixel electrode can be independently driven to a certain voltage, so that an image can be displayed on the photoelectric layer of the display. To control the interpolated photovoltaic layer. Sometimes, each pixel may also include a three-color element of the pixel electrode. The second substrate in the above-mentioned conventional display system has a single electrode (known as a common electrode or a cover glass electrode), and its function is to provide a reference voltage so that the pixel electrode can pass through the interpolated layer of the optoelectronic material. And developed on an electric field.

An example of such a system is a thin film transistor (TFT) liquid crystal display. These displays have been used in many notebook-sized portable computers. In these displays, the color generation method is achieved by using three elements of RGB pixels (where each pixel of the three elements controls the amount of light passing through its corresponding red, green, or blue filter). These color filters are one of the most expensive components in a TFT display.

The main disadvantage of the above-mentioned type of display system is that the result of duplicating pixel electrodes, data lines and thin film transistors on each color pixel increases its cost, reduces light transmission, and requires more surrounding background light to make electricity. Increased consumption.

And as the display rate increases, the frame-to-frame high independence, high contrast, and other keys to brightness become more and more difficult.

Many methods have been implemented to improve the display characteristics of the above-mentioned types of displays. One of the most common methods is to use a common electrode drive circuit and drive the common electrode with a long drive voltage of the common electrode that is as flat as possible. Because of this, the voltage across the liquid crystal portion of the pixel is more fixed, and thus an improved contrast and pixel brightness are obtained.

For example, U.S. Patent No. 5,537,129 discloses a display system with a common electrode, hoping to obtain a flat elongated common electrode driving voltage. Referring to FIG. 2 of the patent, a common electrode 24 is connected to its driving circuit 20 via a resistor 3b. In this way, the impedance loss at 3a and the capacitive coupling from the pixel and data line to the common electrode can be corrected. It can make sure that a detection element 21 with a high input impedance can be used for this correction, so that the output voltage appears more like a rectangle. Figures 5, 9b, 11(c) and 11(d) of the US patent all show the required rectangular waveforms.

Another example is shown in US Patent No. 5,561,442, which discloses that when the previous gate line voltage Vs(t) is matched with the current gate line voltage Vg(t), the common electrode voltage Vc(t) is appropriately applied. Available in LCD (C_LC) Generates a flat rectangular voltage V(t)-Vc(t). This method involves a complicated modulation scheme, which must correlate the modulation voltage of the gate line with the voltage modulation on the common electrode to obtain the required flat long voltage modulation on the liquid crystal.

The present invention provides a variety of methods and devices for controlling the voltage on an electrode used to change the state of a photoelectric material (such as a liquid crystal layer), so that even if the pixel electrode contains pixel data, the displayed data cannot be seen. The control voltage is generally provided in a controlled phase relationship with the update of the pixel data, so that it can be obtained even when displaying at a high rate (at least in some embodiments of the present invention). Independence of the box.

In an embodiment of the present invention, a display system includes a first substrate having a plurality of first pixel electrodes to receive a plurality of first pixel data values representing a first image to be displayed, the display system It also includes a photoelectric layer operably coupled with the pixel electrode and an electrode operably coupled with the photoelectric layer. The display system displays the first image, and then applies a first control voltage to the electrode to change the state of the photoelectric layer so that the first image is substantially invisible and therefore not displayed, and then the display After the electrode receives a second control voltage, the system displays a second image represented by a plurality of second pixel data. Generally, in at least some embodiments of the present invention, the photovoltaic layer is a liquid crystal layer, and the electrode is a common cover glass electrode. The common cover glass electrode and the first substrate form a structure surrounding the liquid crystal layer, so that the first substrate is located under the liquid crystal layer, and the common cover glass electrode is located above the liquid crystal layer. At least in some embodiments, the first control voltage causes the liquid crystal layer to change its light change state, so that the display turns "dark", even if the pixel data on the pixel electrodes still exists or the display is not black or white or white. The same is true for certain other colors. After the display keeps the first image invisible, the display system displays the second image by causing an electrode to receive a second control voltage. The second control voltage causes the liquid crystal material to display substantially no data. Release in a visible state.

The present invention includes many modified embodiments. For example, the cover glass electrode can exist in separate sections, and these sections can be separately controlled so that when one section is displaying a part of an image, another section is loaded for the same image The other part of the pixel data, at the same time, the other part of the image does not display data, because the control electrode in this interval is making the liquid crystal material in this interval block the data, making it invisible.

The present invention can be used in a time-series color system or a color system in which three pixel elements are used once for each pixel. In addition, the present invention can also use or not use the frame buffer to buffer the next frame when displaying the current frame, and the frame buffer can be arranged on the same substrate including the pixel electrode. In addition, the present invention can also be used in a reflective liquid crystal display device or in a transmission type liquid crystal display element. Furthermore, the electrode modulation of the present invention can be applied to a system in which the modulation is performed (so that the liquid crystal can be driven into a state in which the display data is essentially invisible), and the electrodes are placed in the same matrix as the pixel electrodes. middle. Some embodiments of the present invention may further include compensation electrodes placed in the same substrate as the pixel electrodes to compensate for the actions of the control electrodes that make the display invisible according to certain embodiments of the present invention.

At least certain embodiments of the present invention provide several advantages that will be described below. However, it should be understood that certain embodiments of the present invention may only provide some (or one) of these advantages. For example, the present invention can be used to provide a display system in which when the frame buffer is not used, the pixel output on the display is updated at the same time as new data appears, instead of being updated row by row. In addition, the present invention can be used to provide a display system with high frame-to-frame independence (even at a high frame rate frequency). Another advantage of the present invention (at least in some embodiments of the present invention) is that because the voltage driving the control electrode and the voltage driving the pixel electrode are changed simultaneously, a larger average can be obtained on the optoelectronic material layer. The voltage difference improves the brightness. In other embodiments of the present invention, a voltage greater than the maximum and minimum voltages allowed to drive the pixel electrode can be used as the control voltage signal to be applied to the control electrode. This advantage is useful when the critical value of the photoelectric effect of the liquid crystal is lower than the critical value when no photoelectric effect occurs. In some embodiments, another advantage of the present invention is that if the control voltage is modulated at a relatively high frequency oscillating burst, it can quickly drive a dual-frequency liquid crystal display.

Different embodiments of the present invention will be described in detail with reference to the drawings, in which similar reference numbers indicate similar elements.

FIG. 1A shows a cross-sectional view and FIG. 1B shows a three-dimensional view of an image display system according to an embodiment of the present invention.

2A shows a block diagram of an embodiment according to the present invention; this embodiment is a reflective liquid crystal display system, but it should be understood that according to the present invention, a transmission type liquid crystal display can also be used.

Figure 2B shows the photoelectric curve of an example of a liquid crystal that is usually white.

Figure 2C shows the modulation curve of a cover glass according to the present invention, which is a graph of intensity and time, which shows the liquid crystal material under the control of the cover glass waveform as shown in Figure 2C behavior.

Fig. 2D shows a more detailed part of a graph of the intensity and time of a liquid crystal under the control of a cover glass electrode or other electrodes modulated according to the present invention.

3A and 3B are a flow chart illustrating that a sequential liquid crystal display system of the present invention does not require frame buffering of new pixel data when old pixels are displayed.

4A and 4B are flowcharts illustrating an embodiment of the present invention using sequential color subframes with frame buffering.

FIG. 5 is a diagram of an embodiment of the present invention using a spatial color display, in which each pixel includes three sub-pixels, each of which displays a specific light component.

FIG. 6A is a diagram illustrating an embodiment of a pixel circuit that can be used in the present invention.

FIG. 6B illustrates an embodiment diagram of a pixel circuit that can also be used in the embodiment of the present invention. FIG. 6C illustrates another embodiment of a pixel circuit that can also be used in the embodiment of the present invention. Fig. 6D illustrates a pixel circuit with a pixel buffer that can store new pixel data values when the old pixel data values are displayed; the above circuit can store an analog ratio value in the pixel buffer, and It should be understood that a plurality of such pixel circuits can be arranged in an array to provide an analog frame buffer.

FIG. 7A shows the effect of modulating the electrode value with a signal with a non-rectangular waveform according to an embodiment of the present invention. The upper panel shows the time-dependent electrode voltage and pixel electrode voltage when an overdrive pulse is applied. , The middle panel shows the voltage on the photoelectric layer (liquid crystal layer) when the above-mentioned electrode modulation is done, and the lower panel shows the voltage from pixel A when the overdrive pulse is used (solid line) and when the overdrive pulse is not used (dashed line) The intensity output.

FIG. 7B shows a modulation waveform of an electrode that can be used to drive the photoelectric layer to a state where the display data is invisible. The waveform uses a reset pulse instead of a long pulse. FIG. 7C illustrates a waveform diagram of voltage modulation that can be used to make the photovoltaic layer into a state in which display data is invisible according to the present invention.

Figures 8A and 8B show waveforms of electrode modulation including bursts of relatively high frequency oscillations.

The waveform diagram in FIG. 9A illustrates the waveform diagram of electrode modulation voltage and pixel electrode voltage and time when a frame buffer system is used; the electrode modulation shown in FIG. 9A includes a reset pulse wave, which is designed to make the photoelectric layer Be in a state where the display data on the pixel electrode is not visible. FIG. 9A also shows the relationship between the intensity and time of some pixels and its relationship with the waveform of FIG. 9A.

Figure 9B shows a number of waveforms related to intensity and time, which can illustrate the behavior of pixels in a sequential color display system of the present invention. The system uses electrode modulation to make the photoelectric layer placed in the state where the display data is invisible. Next time.

FIG. 10A illustrates a modified embodiment of a cover glass electrode that has been segmented according to an embodiment of the present invention; other similar embodiments include using the control electrode of the segment in the same substrate with the pixel electrode.

The flowcharts of FIGS. 10B and 10C show a sequential color system with interval control electrodes (such as interval cover glass electrodes).

Figure 11 shows multiple waveform diagrams of a sequential color system with interval control electrodes.

Figure 12 illustrates in more detail a sequential color system with interval control electrodes to modulate portions of the photoelectric layer.

13A, 13B, and 13C are waveform diagrams illustrating the relationship between intensity and time of different embodiments using interval electrodes to control a part of the photovoltaic layer.

Figure 14 is a diagram of another embodiment that uses interval electrodes and illuminating pulse waves instead of continuous illumination.

Fig. 15 is a diagram showing another embodiment of the interval control electrode used as an illuminating pulse wave.

FIG. 16A shows a pixel circuit according to an embodiment of the present invention using compensation type electrodes.

FIG. 16B shows a top view of a circuit configuration of a pixel circuit according to an embodiment of the present invention. In this embodiment, a compensation electrode is provided on the same substrate as the pixel electrode in the pixel circuit.

16C shows a graph of voltage and time, which illustrates the waveform diagram of the voltage of the pixel electrode and the control electrode. The control electrode voltage is used to modulate the photoelectric layer to drive it to a state in which the display data is not visible. Down.

FIG. 16D illustrates the effect of a compensation electrode by showing the different relationship diagrams between the pixel electrode and the compensation electrode and for modulating the photoelectric layer.

FIG. 16E shows a graph of voltage and time and a graph of pixel intensity and time related to time according to an embodiment of the present invention.

Figure 17 illustrates the use of a circuit as shown in Figure 6D for control electrode modulation in a display system with frame buffering.

Figure 18 illustrates a waveform diagram of the voltage and time of an electrode modulation signal. The signal uses a cutoff to affect the photoelectric layer of the present invention. This embodiment can be used with an analog frame buffer or other frame buffers. It can Allow new pixel data to be stored on the same substrate with pixel electrodes that display old pixel data.

Detailed description

The following description provides several examples of the present invention. However, it should be understood that other examples of the present invention will become very obvious to those skilled in the art after reading this description. Therefore, the description and drawings of the present invention are for illustration only, and cannot be used to limit the present invention.

FIG. 1A shows a cross-sectional view of a display system 12 according to an embodiment of the present invention, in which a photoelectric layer 22 is placed between a first substrate 20 and a second substrate 24. The first substrate 20 has a single control electrode, such as a known common electrode 26 or a covered glass electrode 26. The second substrate has a number of pixel electrodes 28, each of which periodically obtains updated image data in an independent manner. Each of the pixel electrodes 28 retains the required image data for a given time period or period, and after that, the acquired image data is replaced by new image data. The voltage related to the voltage applied to each pixel electrode and the common electrode 26 will cause a voltage to appear on the liquid crystal material (V_LC), and then control the light change characteristics of the liquid crystal so that the liquid crystal can be selectively placed in at least two light change states. Typically, these states include allowing light to pass through the display system or not allowing light to pass through the display system. At least one pair of light of the first substrate 20 and the second substrate 24 is transparent or translucent. According to an embodiment of the present invention, the photoelectric layer 22 may include a liquid crystal material, and the display system 12 may include a liquid crystal display. It should be understood that other layers may also be present in the structure of the display system 12, such as an alignment layer or an optical coating (such as an anti-reflective coating), and other layers may also be used with the display system 12, such as a polarization layer or Multi-polarization layer. Fig. 1B shows an external view of the same display system of Fig. 1A. The display system 12 may be a thin film transistor (TFT) system, which may be a transmission type liquid crystal display device or a reflection type liquid crystal display device, such as the liquid crystal on a silicon substrate described in US Patent No. 5,426,526.

FIG. 2A shows a display system 101 according to an embodiment of the invention. This embodiment uses a reflective liquid crystal on a silicon display system, which includes pixel driver logic 112, a pixel electrode 104, a liquid crystal layer 106, and a cover glass electrode 108. The system further includes timing control logic 112, an electrode control driver 110, and illuminator 114 and illuminator control logic 116.

In the system 101, the illuminator 114 can provide white light in the case of a spatial color display system, or it can provide three different colored lights (ie, red light) in a time-controlled sequence (controlled time sequence). , Then green light, then blue light, the light system is provided individually). The illuminator 114 provides the light 118 through the control of the lighting control logic 116 receiving a timing signal or a control signal from the timing control logic 112. The timing control logic 112 further controls the electrode control driver 110 to provide an appropriate modulated control signal waveform to the cover glass electrode 108. At the same time, the control timing logic 112 also provides timing signals to the pixel driver logic 102, or it can receive signals from the pixel driver logic 102 to coordinate the voltage signal applied to the cover glass electrode and the voltage signal carried by the pixel electrode 104 Controlled phase relationship between input and display pixel data. The different operation modes of the system 101 will be described as follows according to different embodiments of the present invention.

Figure 2B shows a graph of intensity and voltage, which shows the photoelectric curve for a normal white liquid crystal cell structure. The curve 125 has the maximum intensity at the lowest voltage (ie, zero voltage). In other words, the light change state of this type of liquid crystal is such that the maximum amount of light is transmitted through the liquid crystal under its lowest voltage state. When the voltage passing through the liquid crystal increases, the intensity of the light transmitted through the liquid crystal will decrease to the point where no light will be transmitted at the voltage point 127. This point is considered to be maintained at the black voltage or V_B127. According to the present invention, an electrode (such as the cover glass electrode) can be applied with voltages related to different pixel electrodes, so that the voltage passing through the liquid crystal layer or at least part of it will be equal to or exceed V_B. According to some embodiments of the present invention, the voltage applied to the control electrode can make the voltage across the liquid crystal be the voltage at point 129, where the voltage is an overdrive voltage or V_OD. The overdrive voltage can be used to quickly drive the liquid crystal display material into a state in which light does not pass through it. Therefore, even if the display data is stored on the pixel electrode, the display data is still invisible .

2C shows two time-related graphs, which indicate the relationship between the control voltage applied to the control electrode (such as the cover glass electrode) and the intensity of the pixel in the liquid crystal display of the present invention. The voltage waveform 151 of FIG. 2C represents the corresponding intensity waveform at the corresponding time. At time t₀When the voltage applied to the electrode (for example, the V_CG, At this time, the electrode is a covered glass electrode) will ramp up to a point where the voltage across the liquid crystal is at least V_B, Which causes the intensity of the pixel to drop rapidly, as shown by the pixel intensity curve 153. Then at time t₀And t₁In between, the display data of the next pixel will be loaded onto the pixel electrode, and because of the voltage applied to the control electrode, the display will be maintained in a state where the display data is invisible, so that the liquid crystal ( V_LC) The voltage is or exceeds V_B. Time t₁When the voltage on the control electrode decreases, as shown by the voltage waveform 151, the voltage across the liquid crystal is less than V_B. At this time, because the pixel electrode can now control the state of the liquid crystal, it is possible to display and see the pixel data. By time t₁At this initial point, the liquid crystal begins to return to the light change state as shown by the pixel intensity curve 154. Generally speaking, the liquid crystal material will be released into a light change state, allowing more light to pass through. As shown by the pixel intensity curve 154, the liquid crystal is in the whole time period t₁To t₂During this period, it will be released continuously, and will not "stay" or reach a stable state. This result will be discussed in further detail below, but it is true that because of the present invention, because all such pixels will produce the same result, and the observer can still see the different gradual changes in color or gray in the image, it is not Will inevitably produce shortcomings. At time t₂At time, the first control voltage is again applied to the control electrode such as the cover glass electrode, and the liquid crystal material is quickly driven to a state in which the display data is invisible, such as at time t₂And t₃Between those shown by the waveform 152. At time t₃When the voltage on the control electrode is changed from the first control voltage to the second control voltage, the display data can be seen, such as time t₃And t₄The pixel intensity curve between 155 is shown. It should be understood that the control voltage waveform 151 applied to the control electrode is a DC balanced signal (near certain levels), and it is averaged to the DC level over the entire time. It should be understood that the present invention can be used with or without the DC balance control signal, but the use of the DC balance control signal has its advantages.

Figure 2D shows the frame or subframe of the method of the present invention in more detail. In particular, the pixel waveform 160 shown in FIG. 2D has three parts or curves 161, 162, and 163. Curve 161 illustrates that when a control voltage is applied to the control electrode, it can be quickly driven to the black part of the liquid crystal material, so that the voltage passing through the liquid crystal is approximately equal to V_B. During the application of the control voltage to the control electrode, the pixel intensity is at its lowest value, as shown by the curve 162. It should be understood that the liquid crystal can be driven to a dark state instead of driving the liquid crystal to completely black, so that the image is almost unrecognizable. In this modified embodiment, driving the liquid crystal state so that the display material is essentially invisible still has its advantages, because it can obtain frame-frame independence. At time t₀And t₁During the period, the next pixel data can be loaded on the pixel electrode, such as time T_LShown. During this period, it is better to maintain the voltage across the liquid crystal to be V_BOr V_BThe above method keeps the display in its dark state. At time t₁When the voltage of the control electrode is released to a second control voltage, the voltage passing through the liquid crystal is changed, thereby allowing the liquid crystal to be released to the next light change state, which makes the displayed data visible, which is shown by the curve 163. 163 indicates when the TLC (occurs at time t₁And t₃When the liquid crystal is continuously released during the release period shown in (between), the intensity of the pixel will increase. According to different embodiments of the present invention, it is expected that the entire t₂To t₃Illumination is provided during the period of time or only during that period of time (as shown in Figure 2D). Especially Figure 2D shows that only at time t₂To t₃Illuminate the pixels only when. In another embodiment, at time t₂To t₃Can provide light pulse waves instead of at time t₂To t₃During this period, the display is continuously illuminated. When the first control voltage is applied to the control electrode again, the frame or sub-frame cycle ends, so that the voltage passing through the liquid crystal is essentially V_B(Or preferably V_BOr V_Babove).

3A and 3B show a specific method of the present invention. The method is used in a time-series color display system that does not have any frame buffer on the same substrate as the pixel electrode in the pixel buffer. Figures 4A and 4B show a similar system, but with this type of frame buffer. The method of FIGS. 3A and 3B will be described first.

The method 200 can be regarded as starting from step 202, where the "old" pixel data can be displayed in the last subframe of the previous display data frame. Then after the display time is over, in step 204, a first control voltage is applied to the cover glass electrode to set the electrode to change the state of the liquid crystal so that the old pixel data is essentially invisible, even if some The pixel data is still stored in the pixel electrode as well. Generally speaking, the first control voltage applied to the control electrode of, for example, a cover glass electrode will cause the pixel electrode voltage to be at least V_BThe voltage passes through the liquid crystal. In step 206, the next pixel data is loaded onto the pixel electrode of the first color sub-frame of the current frame, and the voltage of the control electrode is still maintained at a voltage that can essentially pass the liquid crystal At least V_BVoltage. In this way, the pixel electrode is loaded with new data, and the display is kept in an essentially dark state. It should be understood that basically the data is loaded row by row of pixel electrodes, and the pixel electrodes correspond to the rows of the display, one row at a time. Then in step 208, the voltage on the control electrode is changed to release the state of the liquid crystal, so that the loaded next data for the first color subframe (which was loaded in step 206) is now Can be seen on the monitor. If all the columns of the display have been loaded before the voltage of the control electrode is released, the display updates the entire frame at the same time. Then in step 210, the first color subframe is displayed for a period of time. One of the advantages of the aforementioned sequence of steps is that there is a period of darkness between the old frame and the new frame, so the frame now has a higher frame-frame independence, and therefore the performance of the image is more important to the user In terms of better. In addition, even if the pixel data is loaded on the electrodes in a row by row instead of loading the electrodes in the same frame at the same time, the display is still updated in the entire frame at the same time. This is because the voltage of the control electrode will be released once. The liquid crystal can suddenly change its "pixel" state for the entire liquid crystal layer in the entire frame at the same time. The simultaneity characteristic of the liquid crystal response provides a major advantage because it means that the liquid crystal does not need to be converted (from a previous light change state to a new light change state) before it is illuminated. Therefore, before the liquid crystal completes the conversion (or completes its track), the display system can be illuminated, and the display on the display will still appear uniform.

Next, in step 212, set the voltage of the control electrode again (for example, by applying the first control voltage) to change the state of the liquid crystal so that the data used for the first color sub-frame is essentially invisible (vertical The data used in the first color subframe is stored in some pixel electrodes). Then in step 214, the next pixel data is loaded on the pixel electrode of the second color frame used in the current frame, but the voltage of the control electrode is still maintained, so that the voltage through the liquid crystal is substantially equal to or close to V_B. In step 216, the second control voltage is applied to the control electrode to allow the liquid crystal to be released, so that the loaded data for the second color sub-frame is visible on the display. Then in step 218, the second color subframe is displayed for a certain period of time. Basically, this will include illuminating the display in continuous illumination or in pulsed illumination as described herein. In step 220, the liquid crystal is again driven to a state in which the pixel data is not visible. In this case, the data used for the second color sub-frame is designed to be essentially invisible, even if the pixel data of the second color sub-frame is still stored in some pixel electrodes. Then in step 222, the next data is loaded onto the pixel electrode of the third color sub-frame for the current frame, but the voltage on the control electrode is still maintained, so that the voltage through the liquid crystal is substantially V_B. In step 224, the voltage on the control electrode is released (for example, a second control voltage is applied) to change the state of the liquid crystal, so that the data for the third color sub-frame of the current frame is loaded It can now be seen on the monitor. Following step 226, the third color sub-frame is displayed and the display system is illuminated. It should be understood that a similar lighting step can also be used at step 210. In step 228, the method repeats steps 204-226 for the next display frame. When the data is provided to the system, the process continues to process each frame.

The method 425 shown in FIGS. 4A and 4B is similar to the method 200, except that the system of this embodiment uses a pixel frame buffer to store the next frame of pixel data when displaying the current pixel data. That is to say, when the display step is performed, the pixel buffer used to store the next pixel data is loaded during the current frame display period. Generally, this can be implemented in a system where the pixel buffer for a particular pixel electrode is essentially loaded under the pixel mirror electrode. The method is further described in U.S. Patent No. 5,426,526. The special pixel circuit used to execute pixel-by-pixel in a pixel buffer associated with its individual pixel electrode is shown in FIG. 6D herein.

The method 425 starts at step 427, in which the old pixel data from the last frame of the previous frame of the display data is displayed; and when the old pixel data is displayed, the first color frame of the next frame is used The data is loaded into a pixel frame for each pixel. According to an embodiment of the present invention, the pixel buffer stores analog pixel information, and the circuit of FIG. 6D can be used for this purpose. In step 429, the control electrode (such as the cover glass electrode) is set to a voltage that changes the state of the liquid crystal (such as by applying a first control voltage) so that the old pixel data (used in the previous frame The last frame) is essentially invisible. At the same time, during step 429, for each pixel, the buffer data stored in each pixel buffer for the first color subframe is loaded onto the pixel electrode by the pixel buffer. In step 431, the voltage on the control electrode is changed so that the state of the liquid crystal is released, thereby allowing the loaded pixel data for the first color subframe to be visible on the display. If all the columns of the display have been loaded before the voltage of the control electrode is released by applying the second control electrode, the display updates the entire frame at the same time. Generally speaking, because the system described herein has the ability of frame buffering, it usually loads all the columns of the display, although this is not necessary for some embodiments of the present invention. In step 433, the first color subframe is displayed, and when the first color subframe is displayed, the data for the second color subframe is loaded into a pixel buffer for each pixel middle. In step 435, the control electrode (such as the cover glass electrode) receives a first control voltage, which changes the state of the liquid crystal so that the data used for the first color sub-frame is essentially invisible; at the same time, in step 435 In the meantime, the buffer data for the second color subframe that has been loaded into the pixel buffer is now loaded onto the pixel electrode by the pixel buffer. In step 437, the voltage on the control electrode is changed to "release" the liquid crystal state maintained in step 435 Out so that the loaded data for the second color frame can be displayed on the display. In step 439, the second color sub-frame is displayed, and when this second color sub-frame is displayed, the data for the third color sub-frame is loaded into the pixel buffer for each pixel middle. In step 441, a first control voltage is applied to the control electrode (such as a cover glass electrode) to change the state of the liquid crystal so that the data used for the second color sub-frame is essentially invisible; at the same time In step 441, the pixel data for the third color frame is loaded from the pixel buffer of each pixel onto the corresponding pixel electrode of each pixel. In step 443, the voltage on the control electrode is changed (for example, achieved by applying a second control voltage) to change the state of the liquid crystal so that the loaded data for the third color sub-frame of the current frame can be Shown on the display. Then in step 445, the third color sub-frame is displayed, and when the third color sub-frame of the current frame is displayed, the data for the first color sub-frame of the next frame is loaded into each One pixel in one pixel buffer. In step 447, the method repeats steps 429-445 to proceed to the next display frame, and this method continues to be used for each display frame received by the display system of the present invention.

FIG. 5 shows a method 500 according to another embodiment of the invention. This embodiment uses a system with a spatial color first matrix, in which each pixel has three sub-pixels to provide three signals for the three primary colors (such as red, green, and blue). This type of spatial color system is known to those skilled in the art. The present invention provides the advantage of these systems that they can be updated at the same time, and can provide frame-frame independence without merging a pixel buffer for each pixel, so that it can be on the same substrate as the pixel electrode Provide a frame buffer. The method 500 starts at step 502, where the "old" pixel data from the previous frame of the display data is displayed on the display system. Then in step 504, the control electrode receives a control voltage that changes the state of the liquid crystal so that the old pixel data is essentially invisible, even if the pixel data is stored on at least some of the pixel electrodes. Therefore, basically in most embodiments of the present invention, the display frame will be driven to be dark instantaneously. In step 506, the next data for each pixel is now loaded into the pixel electrode in a row-by-row method for the current frame in the previous art, but the voltage on the control electrode is still substantially maintained at V_BOr V_Babove. Next, in step 508, the voltage on the control voltage is changed to the second control voltage, thereby allowing the liquid crystal to change its state, so that the next data used for the loading of the current frame (loaded in step 506 ) Can now be seen on the monitor. If all the columns of the display have been loaded before the voltage of the control electrode is released, the display will be updated for the entire frame at the same time, even if the pixel electrode has only been updated for each column at the same time in the past. Then in step 510, the current frame is displayed for a certain period of time. Step 512 repeats steps 504-510 for the next display frame. In this way, a spatial color display system can obtain improved frame-frame independence. At the same time, the entire frame can be updated at the same time. There is no need to set a frame buffer on the same substrate as the pixel electrode.

6A, 6B, 6C, and 6D show different pixel circuit diagrams that can be implemented in the present invention. For example, the circuits of FIGS. 6A, 6B, and 6C can be used in situations where there is no need to provide a frame buffer on the pixel electrode substrate. Each of these circuits includes at least one pixel electrode, such as pixel electrodes 651, 661, and 671, and also includes a control transistor for selectively loading the pixel electrode. These control transistors are FET652 shown in FIG. 6A, 662 and 663 shown in FIG. 6B, and 674 shown in FIG. 6C. The operation of these pixel circuits is known in the art, and it should be understood that there are arrays of such circuits, where the array includes a plurality of pixel circuit columns, and each column includes a plurality of pixel circuit rows.

FIG. 6D shows a pixel circuit that can be used in some embodiments of the present invention that requires the pixel buffer to be provided on the same substrate as the pixel electrode in the pixel buffer. The pixel circuit of FIG. 6D includes a conventional column selection line 687 and a data or row line 686, and includes a control or pass transistor 685. The pixel circuit further includes a pull-up FET682, a pull-down FET683 and a voltage follower FET684. The pixel circuit of FIG. 6D operates in the following manner: when the old pixel data value is maintained and stored in the pixel electrode 681 (the pull-down signal 688 is maintained at a low state, so that the FET683 is turned off), a new pixel data The value is loaded into the pixel circuit or cell by applying a high column selection signal on the column selection line 687 and simultaneously applying the pixel data value on the data line 686. In this case, FET685 sends the pixel data value (the value is preferably an analog pixel data value) to the gate of FET684. The FET684 should not be in a conductive state at this time, because the pull-up signal is maintained at Low so that no current flows through the source/drain of FET682 or FET684. After the next pixel data is loaded into the gate of the FET 684, the FET 685 will be turned off because the column selection line 687 is driven low. In this way, the new pixel data value will be kept stored on the gate of FET684, and the data line 686 will apply another new pixel data value to the pixel cell in the same row but not in the same row. Then, when the display of the old pixel value close to the pixel electrode 681 ends, the pull-down signal 688 is set to high, thus turning on the FET 683, and then any charge on the pixel electrode 681 is discharged. Next, the pull-down signal 688 is turned low again to turn off the FET 683, and then the pull-up signal is set high to turn on the FET 682. In this way, the FET 684 pulls up its source node coupled with the pixel electrode 681 to within a critical point of the pixel data value (preferably an analog pixel data value). After this pull-up occurs, the pull-up signal is set to a low value again, so that no current flows through FETs 682 and 684, thus allowing the value stored in the pixel electrode 681 to control the display state of the liquid crystal close to the pixel electrode 681 . It should be understood that in one embodiment, the pixel circuit array (column and row) as shown in FIG. 6D can provide an analog frame buffer on the same integrated circuit (single crystalline silicon) substrate as the pixel electrode. . In addition, each such pixel circuit is manufactured in such a way that the circuit can be placed in each

Fig. 7 shows an example of a liquid crystal pixel that switches between a gray level and a color level. This figure illustrates the light response of a single pixel (pixel A) when it is switched between three frames. In this example, the liquid crystal is driven to a bright state by increasing the voltage, and the DC balance is based on the way the frame is connected to the frame. This figure shows the effect of the common electrode voltage modulation with a pulse wave modulation, which is designed to change the light change state of the liquid crystal so that the displayed data will not be seen. In this case, the display will not be driven to become darker, but will be driven to become whiter, and the displayed data will not be seen because the entire display will be driven to be brighter. It should be understood that in general, it is best not to illuminate or watch the display during the state when the display is driven to be whiter by the pulse wave 401.

Referring to FIG. 7A, the upper part of the figure shows the relationship between the voltage on the control electrode or the common electrode and the pixel voltage and time when the pulse wave 401 is applied. The middle part of Fig. 7A shows the voltage passing through the liquid crystal when the common electrode voltage is modulated, and the lower part of Fig. 7A shows the intensity output of pixel A when there is a pulse wave 401 and when there is no pulse wave 401 (there is no pulse wave The response of 401 is represented by a dashed line). The pulse wave 401 does not need to be limited to a flat pulse wave, and it can be positive or negative with respect to the ground, and it can even be switched between positive and negative, as shown in FIG. 7A. It should be understood that this pulse is similar to the time t that occurred in Figure 2C₀And t₁Between the voltage waveform 151 on the pulse wave.

The size and duration of the pulse wave at the beginning of a frame period in FIG. 7A are selected so that the pulse wave will instantly make the liquid crystal below the target gray value. In order to display the sequence as described above, the duration of the pulse wave can be from a fraction of one microsecond to more than one microsecond, and its magnitude can be any size that makes a voltage level V_LCThe value of the pulse wave 405 passing through the liquid crystal is large enough to generate an intensity spike 409 in the pixel A. Of course, in a variant embodiment, the liquid crystal can be driven dark instead of being driven white. Since the pulse wave 401 is applied to all the pixels of the common electrode, it will cause the transition time between a gray level and a lower gray level to increase. Its advantage is that the time transition between a gray level and a slightly increased gray level is not limited by the observed delay, and makes the response in this case slower (this can be determined by the dashed line in Figure 7A Express). In fact, the time limit spent on any conversion is now limited by the release time after the pulse wave. One result of this pulse wave is that the voltage across the liquid crystal layer (depending on its priority order) can increase or decrease instantaneously (temporarily) after the pulse wave. In one embodiment, this additional or added pulse wave can be temporarily updated or acquired as similar to the image data on the pixel electrode.

FIG. 7B shows another method of modulating the control electrode (such as a common cover glass electrode) used in a sequential display device, which uses a pulse whose voltage spike decays exponentially. This pulse wave can be added at, for example, close to the time when all pixels are updated.

FIG. 7C shows another variation embodiment for adjusting the voltage on the control electrode. The modulation pattern 461 has a voltage waveform, which includes several elements shown in such voltage and time graphs. At time t₀At the beginning of a frame cycle, in which the voltage on the control electrode is ramped to a high enough to make V_LCBe driven close to V_ODVoltage (see Figure 2B). This voltage state is at time t₀To t₁The period remains unchanged. This allows the liquid crystal to be quickly driven to a state where the display data is invisible. Then at time t₁To t₂During the period, the voltage on the control electrode changes so that it is maintained at V_BUnder the voltage below (see Figure 2B), instead of over-driving the liquid crystal layer. By time t₀To t₂The time can be used by the display system to load the new display data for the current frame into all the pixel electrodes (and effectively eliminate the old display data), and then at time t₂When the pixel data can be displayed. Generally speaking, all the pixel electrodes at time t₂It is already loaded at the beginning, so all the liquid crystals can start to change from t₀To t₂The change state that exists during the period is converted to a release state. The release of this liquid crystal may be allowed to occur at time t₂And t₃In between, this period is also the period when the image data starts to be displayed in at least a part of this period. Usually, t₂To t₃The period of time includes the time to illuminate the display, if not all the time is at least part of the time. In addition, the illuminating pulse wave can be applied instead of continuously illuminating at least part of the period from t2 to t3. The modulation scheme shown in FIG. 7C therefore has the advantage of rapidly driving the liquid crystal to a changing state in which the display data is invisible, while maintaining it in a visible state when it is released. This can increase the response time of the device, thereby allowing the frame rate of the display device to be driven at a higher frequency, which is determined by the amount of time it takes to load the control electrode. By time t₃The initial cycle continues, except that the signal priority is changed due to the fact that the control voltage signal applied to the control electrode is DC-balanced near a certain DC level (such as a certain non-zero level). It should be understood that the purpose of performing the above-mentioned DC balance is to provide a DC balance signal to the liquid crystal so that the DC balance level of the liquid crystal is close to zero voltage.

8A and 8B illustrate another embodiment of the present invention, in which the control voltage applied to the control electrode is modulated with a relatively high frequency oscillation burst (for example, 5 kHz to 100 kHz). This plan is useful for driving dual-frequency liquid crystal materials in the following types of displays: below the crossver frequency, the liquid crystal material has a positive dielectric anisotropy (anistropy), and above the cross-talk frequency , It has negative dielectric anisotropy.

When describing the usefulness of the features of a display system, consider the following example: an image is written into a display system 12 by applying a voltage pattern to the pixel electrode array 28. The common electrode 26 is modulated according to an embodiment of the present invention as shown above, or in another way, it can be clamped to a given voltage, and each pixel of the photoelectric layer 22 is converted to a specific voltage. The required state. Then, after seeing the image, I hope to quickly reset each pixel of the photoelectric layer 22 to a closed state, so as to prepare to obtain the next set of image data, so that the old image data is invisible, and the new one is obtained. The image data group or the acquired ones can be separated from the previous frame by temporarily blanking the display. This can be achieved by using a dual-frequency photoelectric liquid crystal material and performing the reset, or by applying a short period of high frequency voltage signal to the common electrode 26 to drive to the off function. It should be understood that if an AC signal is used to maintain the liquid crystal in a state where the display (pixel) data is substantially invisible (such as a "dark" state), it is best to make the phase of the AC signal and the pixel data written The phases of each column of the pixel electrodes are synchronized, so that the effect of the capacitive coupling between the control electrode (such as the common electrode) and the pixel electrode is equal.

In the basic principle of the electrode modulation of the present invention, there should be a plurality of variables related to the modulation characteristics, and there is a nearly temporary relationship between the electrode voltage and the update of the image data to the pixel electrode. For example, in one embodiment of the present invention, a relatively short pulse wave can be applied to a control electrode voltage other than DC. The modulation referred to here can be composed of pulse waves that are shorter than the period of the image data on the pixels. According to another embodiment of the control electrode voltage modulation principle of the present invention, the period of the pulse wave applied to the control electrode can be longer than the period of the image data on the pixel. In the latter example, the time that the image data remains on the pixel is shorter than the update period.

According to another embodiment of the present invention, the control electrode voltage modulation may include a relatively high frequency alternating current (AC) modulation cluster.

As shown in FIG. 9A, according to another embodiment of the present invention, the common electrode voltage can be modulated by a pulse wave, so that the photoelectric material or liquid crystal can be quickly "driven to dark", although during the driving dark state Any pixel data is still stored in the pixel electrode. It is also possible to design certain liquid crystal cell structures that are white under normal conditions and need to be addressed by driving the liquid crystal cell with a voltage to make it dark. According to this embodiment, the voltage addressing can be achieved by driving the common electrode to a voltage different from the pixel voltage, and driving it to dark quickly. Next, the grayscale or chromaticity is established in a way that allows the liquid crystal to be released back, and different grayscale or chromaticity is generated according to the voltage on the pixel electrode. It should be understood that grayscale can be regarded as a color for the purpose of the present invention. The embodiment shown in FIG. 9A also uses a pixel frame buffer to store the next pixel data in a pixel buffer when the current pixel data is being displayed.

The common electrode voltage can be overdriven to obtain the optoelectronic material very quickly by using a voltage higher than the voltage maintained in a dark state.

An example of a photoelectric response suitable for this embodiment is shown in FIG. 2B. The intensity output from a pixel decreases with the voltage applied to the photovoltaic layer. The photoelectric curve shown here will show a saturated response when the voltage increases above the "black sustain voltage", which also means that the output remains dark at a higher voltage. The present invention also uses liquid crystals with different photoelectric curves, such as the liquid crystals similar to those shown in Figure 2B. The only difference is that the curve 125 is at a certain point after the point 127 (which may be V_ODBefore) will rise again, rather than remain flat. In this case, V_ODNot all are applied to this type of liquid crystal. Another variation is that a thick liquid crystal layer with a more complex curve can be used, and curve 125 can be regarded as part of the complex curve; in the case of a thick liquid crystal, the useful part of curve 125 can be used, and It is not necessary to completely release the liquid crystal onto other parts of the complete and complicated curve. It should also be understood that for some liquid crystals, different colors may have different electro-optical (EO) curves (for example, a liquid crystal may have a first EO curve (V_BV of EO1_B) And a second EO curve for another color (V_BV of EO2_B)). In this case, it should be desirable to coordinate the control voltage applied to the control electrode with the color, while matching the control voltage with the color and the EO curve. At this time, care should be taken to ensure that the voltage V generated by the electrode passes through the liquid crystal_BIt is sufficient to make the previous pixel data invisible until the next pixel data is to be displayed.

The release of the gray scale ratio occurs through a related curve family, and the release effect allows the gray scale or chromaticity to be seen even if the material slows down due to the temperature drop. Since the photoelectric material between each image will be completely reset, the following images are independent of each other.

Longer viewing time can be obtained in a system that uses time-sequential color lighting or time-sequential color filtering. This is because resetting the frequency makes the color sub-frames independent of each other, so for a frame in a dark state, even if The material is close to the final grayscale or chromaticity, and the device can still be seen. Visible pixels even during a quick reset will help to get more light output. A color sequential principle is shown in Figure 9B.

In particular, FIG. 9B shows the result of driving to dark quickly after each color subframe. Each color sub-frame can have a period of about 5ms, in which it is continuously illuminated during the entire period, or is continuously illuminated only during a part of the period, or only non-existent during the period. Continuous lighting pulse wave lighting. Then, a red sub-frame, a green sub-frame, and a blue sub-frame are sequentially displayed within a period of about 15 ms. These times are just examples of achieving visual integration as disclosed in U.S. Patent Application Nos. 08/505,654 and 08/605,999, and the contents of the aforementioned patent applications have been incorporated into this case for reference. However, it should be understood that other times can also achieve the above purpose, including the display period of the subframe less than 5ms, and even a display period of 10ms or more.

Referring to FIGS. 9A and 9B, a reset pulse 600 is applied to the pixel electrode for a small part (referred to herein as 1ms) during the sub-frame period (referred to herein as 5ms). Assume that there are four pixels 601, 602, 603, and 604, each with initial intensities I1, I2, I3, and I4, and each with intensities of 1-4. Once the reset pulse 600 appears in pixels 601-604, their intensity will drop from 1-4 to zero, that is, they are at time t₁Will be driven to dark quickly. Note that the display will not display visible data, even if there are pixel data values on the pixel electrodes. Please also note that all the pixel electrodes will simultaneously receive the updated pixel data values (as indicated by the intermediate and full changes of the pulse wave 600 and the pulse wave 609 at the beginning). This is because the display system of FIG. 9A uses pixel buffers. Generally speaking, this system includes a pixel buffer (such as an analog pixel buffer) on each pixel electrode. Then the intensities 1-4 are increased to their individual gray levels after the reset pulse ceases. As described above, the pixel 604 is driven to the brightest gray or color level. The brightness of each pixel seen by the observer should be proportional to the area covered by each curve 1-4. The next reset pulse 609 drives pixels 601-604 to dark at t2, and then releases to grayscale or color with a lower intensity-to-time conversion method. This phenomenon can occur when pixels 601-504 are cold. when. As you can see, the independence of the frame (secondary frame) can be obtained even when the frame pixels 601-604 are cold. It should be understood that the use of the frame buffer (shown in Figure 9A) of the present invention can potentially allow the application of a short reset pulse (making the previous frame substantially invisible) without having to be loaded on the pixel electrode. Keep the reset pulse at that time. Since a load signal (such as the pull-up and pull-down signals described in the pixel circuit of Figure 6D) can be applied to all pixels, the entire frame of the pixel data can be made from the frame buffer (pixel buffer). Therefore, the time required to load the pixel electrode is much shorter than the time required to load one column (or two columns) at a time without a frame buffer. Therefore, a shorter reset pulse (or a longer sustain pulse is not needed to load the pixel electrode) can be used to obtain frame-to-frame independence.

Liquid crystal structures are generally considered unsuitable for certain applications. For example, a thick liquid crystal cell is easier to manufacture but its response may be too slow. When the liquid crystal cell is released, overdrive to quickly reset to dark, and then see the grayscale or chromaticity, you can get good performance, even if the liquid crystal cell will never reach its final state at the address voltage. And because of independence, reset makes it possible.

This embodiment can be used together with different types of DC balance. Frame-based, behavior-based, column-based, or even pixel-to-pixel DC balance can all be used to make the common electrode embedded as (V_max-V_min)/2, and make sure that the pulse wave that is driven to be dark is implemented in AC polarity. In this case, only the data driven dark is the pixel electrode so that the liquid crystal is DC balanced.

The DC balance of the frame inversion can also be used in the principle of modulating the common electrode voltage. An example of this approach is shown in Figure 9A. Generally, this driving to dark method can ensure that the pixel electrode data is updated to arrange a pulse sequence for driving to dark, so that during many update cycles, the voltage of the photoelectric layer is averaged to a value close to zero to maintain DC balance. .

The pixel electrodes can be embedded to some known voltage during the reset period, or they can be kept in an arbitrary state if the common electrode is driven to a sufficiently high voltage.

As shown in Figures 9A and 9B, the initial reset causes all pixels to become zero volts. The photoelectric device (such as a liquid crystal device) makes all the pixels become dark quickly. Then the pixels are all set to their grayscale or chromaticity voltages, and the liquid crystal display starts to release the grayscale and chromaticity corresponding to these voltages. The device can be seen during the entire release period (and the next reset period) because the image is not contaminated by the previous image. The following reset causes the pixel to be set to its highest voltage, and the common electrode is driven negative. The next image appears when the common electrode is set to its maximum pixel voltage and the pixel electrode is below the maximum pixel electrode. Therefore, in this particular example, the DC balance can be obtained on a frame-to-frame basis.

It is important to note that in this embodiment of the present invention, even if the pixels cannot update their electrodes with new data at the same time, it is still possible to drive the optical output of a large group of pixels to dark at the same time. In addition, with the present invention, it is possible to make the pixel have the ability to update the electrode voltage at the same time.

FIG. 10A shows an interval display 800 composed of an array of pixels, in which the electrode voltage is updated one column at a time (or two columns at a time in a suitable array configuration). The pixels 802 and 803 labeled "A" and "B" are in the first column 804 of an interval 809 of the array 812, and the pixels 814 and 815 labeled "C" and "D" are located in the last column of the interval 809 806 in. The second and third intervals 810 and 811 of the array 812 are also shown in this figure. It should be understood that the design of any section of the array 812 (including pixel electrodes and other pixel grid circuits) is such that the final section has only one pixel or some pixels, and these pixels can be arranged in one or more columns. No matter what the interval of the array 812 is, the electrodes are also separated by the interval. For example, the configuration of the electrode sections 831, 832, and 833 corresponds to the first, second, and third sections 809, 810, and 811 (with three pixel electrode groups) of the display array 812.

10B and 10C show an embodiment of the method of the present invention, which uses interval control electrodes in the time-series color display system of the present invention. The method starts at step 1001. In the preferred embodiment, three steps normally occur at the same time. It should be understood that these three steps do not actually need to occur at the same time, and their time can partially overlap. However, in order to achieve the many benefits of this method, it is best to perform these three steps in essentially the same period. The three steps include loading the next pixel data in the second color component (for example, a red component) in the first section of the control electrode into the pixel electrode of the first section. It also includes setting the control electrode of the first interval to a voltage at which the related liquid crystal material does not allow the pixel data to be seen and resets the first interval to dark. At the same time, the pixel data in the second interval is displayed with the first light component (such as blue light component). In step 1003, according to the preferred embodiment of the present invention, generally three steps are essentially processed at the same time. This step 1003 includes adding the second color component (such as red pixel data) used in the second interval. One pixel data is loaded into the pixel electrode in the second interval. Step 1003 further includes resetting the second interval to dark by applying an appropriate voltage to the control electrode of the second interval. At the same time, the pixel data in the first interval is displayed with the second light component (such as red light). Then in step 1005, the system continues to display the first section of the image with the second light component, and starts to display the first section of the image with the second light component (red light as shown in FIG. 11) in the second section. The processing flow executed in step 1001 occurs at time t shown in FIG. 11₀To t₁between. The processing performed in step 1003 is at the time t of the waveform in FIG. 11₁To t₂Between. The two processes in step 1005 are performed between time t2 and t3 in FIG. 11.

Fig. 11 is a diagram illustrating the action and timing of the method according to the five different components of the system of the present invention shown in Figs. 10B and 10C. In particular, the graphic 1101 shows the relationship between the voltage of the pixel electrode and the time and the relationship between loading data into the pixel electrode and the time to illustrate the actions taken in relation to the pixel and the time. The graph 1103 shows the relationship between the voltage and time of the control electrode with two separate sections, so that different parts of the liquid crystal layer are reset to dark. The graph 1104 displays a graph of the relationship between the intensity of a pixel in the first interval of the liquid crystal and the time. The graph 1105 shows three different light illuminators and time-related operation conditions related to the operation of the other components of the system as shown in FIG. 11. The graph 1106 shows the relationship between the intensity of the liquid crystal and the time in the interval 2 of the liquid crystal layer.

Now continuing with the description of FIGS. 10B and 10C, step 1007 includes three operations that are generally performed substantially simultaneously. These operations occurred at time t in Figure 11₃And t₄between. Next, in step 1009, these three operations are performed substantially simultaneously between t4 and t5 in FIG. 11. Then in step 1011, the system continues to display the first interval with the third light component (such as green light), and starts to display the second interval with the third light component (such as green light), which happens as shown in Figure 11. Show time t₅And t₆between. It should be noted that staggering different intervals related to a specific light component (such as a red light component) does not affect the overall appearance of the display, because each interval receives the same amount of display time and the same amount of illumination. One advantage of this method is that when the time for the liquid crystal to change from one light-changing state to another light-changing state is maintained at the same amount, the time required to load pixel data can be nearly doubled, thus allowing the designer to freely Design the driving electronic circuit related to the load pixel electrode. For example, a cheaper and slower electronic circuit can be used instead of a faster and more expensive driver electronic circuit.

The method shown in Figures 10B and 10C continues with steps 1013, 1015, 1017, and finally 1019, as shown in these figures. Step 1013 occurs in the time frame t of Figure 11₆And t₇Between, and step 1015 occurs in the time frame t of Figure 11₇And t₈Between, step 1107 at time t₈The start of the above and next frame (may be time t₀) Happened before.

The methods shown in FIGS. 10B, 10C, and 11 assume that two intervals of equal size are used, one of which displays half of an image, and the other displays the other half of the image. It can be seen that a two-zone display has certain advantages, so it is best used for flood lighting. For example, this type of display takes the longest time to appear, allowing the loading of pixel data while maintaining the same time required for liquid crystal switching, such as that required by a single common control electrode (such as a cover glass electrode). Universal lighting generally uses a light source (such as a primary color in a time series system or "white" light in a spatial color system) to illuminate the entire display device (all sections), rather than some forms of structure Illumination, like a scanning light source, illuminates only a portion at a time, while the light source scans the entire display. A display system using interval filters or structured lighting may require more than two intervals of electricity.

FIG. 12 shows the actions of four different pixels related to the control voltage applied to the control electrode (in the implementation of FIG. 11, an interval or segment electrode). The pixels A, B, C, and D in FIG. 12 are the same as the pixels A, B, C, and D shown in FIG. 10A. But note that in Figure 12, during the reset period when the pixel data is not visible, the pixel electrodes for pixels A and B are essentially updated at the same time at the beginning of the reset-to-dark period, because these pixels are in the interval 804 In the first column of, and because the control voltage is applied to the control electrode as described above, it will not affect the display, as shown in the bottom part of FIG. 12. Please also note that the pixel electrodes for pixels C and D are updated near the end of the reset to dark state.

The sequence shown in FIG. 12 starts with pixels "A", "B", "C", and "D", which all have electrode voltages corresponding to an image that has been seen and is about to be updated. The voltage of the common electrode in the first interval on the first interval 831 of the common electrode 820 is modulated to a high voltage to quickly drive all the pixels to a dark state, which has nothing to do with the voltage on the pixels. Then, the pixel electrodes for the pixels 802, 803, and 815 are updated to their new voltages in the known addressing method one column at a time. After all the rows in the interval have been updated, the common electrode is set to the next value displayed by the image. In Figure 12, this value is shown as zero volts, but this value depends on the choice of the DC balance method used. Furthermore, in order to drive the liquid crystal, the dark pulse wave may vary between positive and negative pulse waves to maintain DC balance. Note that all the pixels will be driven to a dark state quickly and simultaneously, and all the pixels will start their tracks toward a gray level at the same time, even if the pixels are updated one column at a time. Please also note that in the system of FIG. 12, because the pixel electrodes are not updated at the same time, the method of pixel frame buffering (such as a pixel circuit array with pixel buffers) is not used. At the same time, it should be understood that FIG. 12 also illustrates the operation of a display system in which the control electrodes are not partitioned.

A display system with a segmented control electrode can be used to update all pixels in the segment at the same time. This principle can be used, for example, in a system where an interval color filter is placed on the display, or in a system that uses a structured lighting form (such as scanning lighting for non-universal lighting) to generate time series color. Furthermore, this principle can also be used in a form of universal lighting, and this universal lighting can be used continuously during a frame or a frame, or a non-continuous lighting pulse can be applied during a frame or a frame. Wave. This will be further illustrated in FIGS. 13A, 13B, 13C, 14 and 15.

Before discussing the lighting part, it should be noted that the present invention provides a multi-section control electrode with more than two sections. This is shown, for example, in FIG. 13A, which has three sections, which are loaded into the pixel electrode separately, and then displayed after releasing the appropriate control electrode for that section. The embodiment shown in FIG. 13A shows a graph of the intensity and time of three different pixels in three different intervals of the present display system. In particular, the graphic 1301 shows a liquid crystal transition time t_LC1, Which is used for the intensity curve of a pixel in the first interval. This pixel is represented by time t at time 1303₁During loading. The pixel intensity curve 1305 indicates that the₁A pixel in the second interval loaded after the end. Finally, the pixel intensity curve 1306 represents the intensity of a pixel in the third interval.

FIG. 13B is actually the union of a part of the figure 1104 of FIG. 11 and a part of the figure 1106 during a specific color subframe period, in which the two figures 1104 and 1106 have moved. The graph 1310 shown in FIG. 13B includes a pixel intensity curve 1318 for a pixel in the first interval and a pixel intensity curve 1320 for a pixel in the second interval. The two intervals are at their respective pixel load times. The periods 1314 and 1316 have been loaded into their individual pixel electrodes. As shown in the figure, the lighting time is a continuous lighting 1312. Note that in the embodiment shown in FIG. 13B, the loading time t₁Equal to load time t₂, And the liquid crystal conversion time is T frame-t₁. The T frame is indicated by a thick line. The two LCD track-illuminated displays can ensure that the two sections have the same brightness and the same behavior under temperature changes.

FIG. 13C illustrates an embodiment using a control electrode interval, in which the loading time has become slower, so that t₁And t₂Got longer. The slowest possible load time is at t₁=t₂= t frame/2, this system is shown in Figure 13C. This example makes the liquid crystal tracks in the upper and lower half of the array (the liquid crystals are released to their last light changing state) completely separated in time. You can also use time T frame lighting as before. However, it is more advantageous to illuminate the pulse wave near the end of the track. In this way, only the brightest part of the curve of the bright pixel can be illuminated to obtain the maximum cognitive contrast. Depending on the characteristics of the illuminator, the brightness of the illuminator can also be increased. This slowest addressing principle can be viewed as the bottom half of the image can be seen when the top half is loaded, and then the top half of the image can be seen when the bottom half is loaded.

In a time-series system, the principle of pulse wave illumination using two pulse waves in each frame is shown in Figure 14, where there is a pulse wave at the end of the display close to the first interval, and the display close to the second interval There is a pulse at the end. The principle 1401 shown in FIG. 14 shows the liquid crystal track of a pixel 1404 after loading a pixel during time 1402, and it is displayed at time t₂(As shown at time 1408) during a certain period of time, the liquid crystal track of a pixel 1410 is loaded after that pixel. The illumination pulse is not continuous and separated by darkness.

Figure 15 shows an example where more than two pulse waves can be used in each color subframe. In the example shown in Figure 15, t₁And t₂Shorter than t in Figure 14₁And t₂. For example, t₁1502 can be equal to t₂1506, as shown in the embodiment of FIG. 11. Therefore, it is possible to allow the liquid crystal material to advance upward along its transition curve for a longer period of time before it is reset by the interval control electrode. Compared with the method that uses sampling (average method) to convert a better part of the liquid crystal, pulse wave illumination (according to the characteristics of the light device) has its advantages again. The placement and timing of this pulse will be described below. The rightmost pulse wave 1516 is placed in such a way that the illuminable curve 1510 corresponds to the brightest part of the lower section. In order to maintain the symmetry between the two parts of the image, the corresponding part of the curve 1504 used for the right part of the array is also illuminated by the pulse wave 1514. In this discussion, because it assumes universal lighting, the pulse wave will also illuminate the liquid crystals in the lower half of the array before it reaches its optimal state. Once again, in order to maintain symmetry, we need to illuminate a portion of the trajectory of the liquid crystal in the upper half of the array, which is represented by curve 1504, which determines the time of the earlier pulse 1512. Finally, to complete the symmetry, pulse 1506 is used again. Now curves 1504 and 1510 are illuminated in exactly the same way, in this example four pulse waves are taken. Note that in both cases, the lowest contrast part of these curves is not illuminated.

It should be noted that a typical embodiment may use control electrodes in which the sections are completely electrically separated from each other. In a variant embodiment, the control electrode section may be coupled by a high impedance. For example, in the case of using a cover glass electrode, the manufacturing process of the cover glass electrode is to first generate a common electrode with one section, and then to etch or separate the two sections to make the electrode produce two sections ; However, this separation is incomplete, even a high-impedance connection between the two sections. It should be noted that a spatial color system can also use the multiple control electrode sections provided by the present invention. That is to say, in addition to using time-series color, one aspect of the present invention can use a spatial color system defined by the plurality of control electrode intervals (each pixel has three different color sub-pixels and a corresponding structure ).

An advantage of most embodiments of the present invention is that a simple pixel circuit can update their optical output at the same time, even if the pixel electrodes are not updated at the same time. One such pixel circuit is shown in Figure 6A, which uses a signal transistor to load data into a capacitor. Usually a capacitance is formed between the pixel electrode and the control electrode (it usually refers to a common cover glass electrode), plus additional capacitance that can be obtained in many ways, such as between the pixel electrode and an adjacent column selection line This is shown in Figure 16A with other capacitors 1604. The method of forming other capacitors depends on the structural details of the pixel array. For example, if the pixel array is formed on a single silicon substrate or wafer using a commercially available CMOS process, there are typically several interconnection layers, and these interconnection layers can be metal or polysilicon. These layers can be configured when designing the pixel array to provide additional capacitance that is beneficial for preventing image delay. Another way to form additional capacitance in this process is to define a thin oxide region between the conductive layer (usually referred to as the polysilicon layer) and the host material that can be doped. This thin oxide capacitor provides a higher capacitance per unit area than other configurable capacitors. In this way, the simple pixel circuit shown in Figure 16A uses capacitive storage to maintain the electrode voltage on the pixel electrode Until it is refreshed. The part of the capacitor is between the pixel electrode and the common electrode. Therefore, when the common electrode voltage is changed to release the liquid crystal from the aforementioned dark state after the pixel has been loaded with data, the capacitive coupling between the common electrode voltage and the pixel electrode will cause the pixel electrode to change. Need a little compensation. This change is shown in FIG. 16C, which illustrates that the common electrode voltage waveform 1619 has a reset portion 1619a and a release portion 1619b in the same time, and four different pixel electrode voltages 1621a-1621d. Note that at the release point 1625, because the voltage of the common electrode changes, the voltage of the pixel electrode also changes.

The magnitude of the change in the pixel electrode voltage is determined by the magnitude of the change in the common electrode voltage and the ratio of the capacitor (including the capacitor 1604 and the capacitance to the common electrode) shown in FIG. 16A. Certain couplings between the pixel electrode and the common electrode (or the interval electrode in the case of using an interval electrode) may not be absolutely disadvantageous. If all pixels have the same capacitive coupling and the same additional capacitance to the cover glass electrode, they all exhibit the same displacement, but they will not lose their uniformity. The above coupling will weaken the effect of the control electrode modulation of the present invention, so it needs to be converted in a larger voltage range. Another possible problem is related to the situation where the pixel array is manufactured in a single silicon CMOS process, and if the pixel is addressed using a single in-channel transistor, the electrode is located at and The reverse biased PN junction on the FET terminal to which the pixel electrode is connected is insulated. If the voltage on the pixel electrode is pulled low enough to make the junction become forward biased, then charging is performed next to embed the voltage of the pixel. This will limit the useful voltage range that can be used on the pixel electrode.

One way to do this is to make the extra capacitor configuration as shown in FIG. 16A larger than the capacitance between the pixel electrode and the common electrode. If there is enough capacitance, this method can allow the voltage on the electrode to move small enough to avoid adverse effects. Another method is to use a pixel circuit with a buffer to drive the pixel electrode, as shown in (for example) FIG. 6D. Another method is to configure one of the additional capacitors as shown in FIG. 16A to connect to a signal that can be switched with respect to the common electrode or the control electrode. This additional electrode can be regarded as a compensation electrode, which receives a compensation signal. If the pixel array is implemented in a CMOS process, the data line can be a first level metal, the gate line can be a second level metal, and the pixel electrode can be a third level metal. This is shown in FIG. 16B, where the pixel electrode 1632 is placed on the compensation electrode 1630, and the compensation electrode is placed on the metal 1 (ie, 1634). The gate line 1626 uses metal 2 and therefore has the same level as the compensation electrode 1630. As shown in FIG. 16A, the transistor 1605 has a gate 1620, a source 1622, and a drain 1624; it should be understood that the source 1622 and the drain 1624 are located in the matrix. It is possible to use a combination of many layers to create additional capacitance, as shown in Figure 16B. It should be understood that the compensation electrode 1630 will be coupled to a driver circuit to drive a compensation electrode voltage 1627 in a manner opposite to the common electrode voltage waveform 1619 shown in FIG. 16D. At the same time, as shown in FIG. 16D, the effect of the compensation electrode voltage is to make the pixel electrode voltage approximately not affected by the conversion of the common electrode voltage. The overlap area between the gate line 1626 and the pixel electrode 1632 can be selected so that the electrical volume between the pixel electrode and the common electrode (using the common electrode to convert the voltage) is approximately equal to the electrical volume between the pixel electrode and the compensation electrode, and this The line voltage is switched in the opposite way to the common electrode switching. It should be understood that if the control electrode (in one embodiment, the electrode is a common electrode) is actually interval, the compensation electrode 1630 should also be correspondingly interval on the display.

In another aspect of the present invention, the compensation electrode can be used as a level displacement control, so that the liquid crystal material can be reset to a state in which the display data is invisible (as described above). This also means that instead of using a cover glass electrode as a common electrode or using multiple electrode sections, an electrode similar to the electrode 1630 of FIG. 16B can also be used to modulate the liquid crystal layer, as shown in FIG. 2C. The method described is reset or released on the liquid crystal layer. In this way, according to the present invention, the interval of the control electrode that can be used to reset and release the liquid crystal layer becomes easier, because it is performed on the same substrate containing the pixel electrode instead of a common cover glass Intervals are generated on the electrodes. The pixel circuit shown in FIG. 16B can also be used to provide such a control electrode as the electrode 1630, which receives similar control signals as the cover glass electrode described above.

An example of using a control electrode in the same substrate as the pixel electrode (such as electrode 1630) is as shown in FIG. 16E. The example in Figure 16E assumes that the covered glass electrode is fixed to V_dd/2 (as indicated by signal 1651), and the pixel electrode can be set to zero and V_ddAny value in between. The control electrode in the matrix with the pixel electrode is in a state (at V_dd(Place) and another state (when V=1), as shown in waveform 1653. During the state of one of the control electrodes in a frame, the display data is essentially invisible, as shown by waveform 1655. During the release state of the control electrode, the display data is visible, as shown by the rising track of waveform 1655. The pixel value is loaded on the pixel electrode during the reset state of the control electrode, and the display is maintained in a dark state, and when entering the released state, the capacitive coupling between the control electrode and the pixel electrode will also be simultaneously Move the voltage of these pixel electrodes as shown by the pixel electrode waveform 1657. The principle of Figure 16E is to use a time series color, each frame has three sub-frames, and DC balance is used between the frames. Therefore, the reset state of the control electrode in frame 1659 occurs when the control electrode is maintained at V_dd, And the release state in block 1659 occurs when the control electrode is at zero volts. Similarly, the reset state of the control electrode in frame 1661 occurs when the control electrode is maintained at zero volts, and its release state occurs when the control electrode is V_ddTime.

Some liquid crystal display systems use a frame sequential DC balance principle, in which data is written so that the image sequence is staggered to write positive polarity and then negative polarity to balance the liquid crystal DC. Assuming that any pixel electrode of the display substrate can be driven to V_maxAnd V_minWithin the voltage range, if the common electrode is fixed at V_maxAnd V_minIf the voltage is within half of the range, the maximum DC balance signal that can be applied to the liquid crystal can be in the form of a sequence of frames at +(V_max-V_min)/2 and -(V_max-V_min)/2 alternates between, so (V_max-V_min)/2 RMS voltage.

According to different embodiments of the present invention, several different types of common voltage modulation can be implemented. Referring to FIG. 17, according to an embodiment of the present invention using a pixel buffer with pixel electrodes (on the same substrate, as shown in FIG. 6D), the voltage of the common electrode 26 of the display system 12 can be at V_maxAnd V_minModulation between. By driving the common electrode 26 to V during the "positive" frame period of this type of electronic addressing principle_minAnd drive to V during the "negative" frame_maxThe voltage of the maximum DC balanced RMS signal appearing in the photoelectric layer is (V_max-V_min)/2 to (V_max-V_min) Between the doubles.

For example, during the "positive" frame period, a pixel driven to a bright state is assumed to have a high voltage at the pixel electrode. (But please note that the opposite is also possible, that is, the high voltage of the common electrode 26 can also drive a pixel to a dark state, depending on the structure of the photoelectric layer or the liquid crystal used.) According to the present invention, sharing The electrode can be driven to V during the "positive" frame_min. Therefore, the range of voltage that can appear in the photovoltaic layer 22 is determined by V_min-V_minTo V_max-V_min, And the same as the voltage range available on a pixel electrode 28.

Under the "negative" frame, the common electrode is driven to V_max, And a bright state can be obtained by driving the pixel electrode to a low voltage, so as to maximize the voltage passing through the photoelectric layer 22. At this time, the voltage range that can pass through the photoelectric layer 22 is determined by V_max-V_maxTo V_max-V_minbetween. In the example shown in FIG. 17, the pixel electrode is driven in such a way that the voltage passing through the photoelectric layer is approximately 2/3 of the maximum available voltage. The next level of the display system allows the pixel electrodes to be updated with data corresponding to a new image at the same time. This type of display system is as described in US Patent Application No. 08/505,654, the content of which is incorporated herein for reference, and will be regarded as a frame (sub-frame) sequential display system. Since the pixels in this type of display are updated at the same time, according to an embodiment of the present invention, when the common electrode is modulated, the pixel electrode does not need to be driven to a voltage other than its data voltage (and its DC-balanced Inverted) voltage value, so its driving circuit has to be simplified.

The above is different from the way that the pixel electrodes are updated one column at a time. One method of doing this update in an active matrix display is to drive the reference plane of the pixel data storage capacitor through a voltage sequence that mimics the common electrode voltage modulation. This can be achieved by driving all the column gate lines in synchronization with the common electrode, but the complexity and power consumption increase, see the content of US Patent No. 5,561,422, which is incorporated herein by reference.

According to another embodiment of the present invention, the common electrode is driven to V_maxAnd V_minThe voltage. For example, as shown in FIG. 18, the common electrode 26 can be driven to be less than V during the "positive" frame._min(E.g. V_min-V_offset), and is driven to be greater than V during the "negative" frame_max(E.g. V_max+V_offset). The result of this principle is that the voltage range that can be applied to the photoelectric layer 22 is now shifted to V at the minimum address voltage._offset, And shift to V at the maximum address voltage_offset+(V_max-V_min)。

An embodiment of the present invention illustrated in FIG. 18 can be applied in the following situations (for example): when the minimum threshold voltage of the photoelectric effect of the liquid crystal is lower than the minimum threshold when no photoelectric effect occurs. Choose V by adopting some or all of the cut-off methods_offsetTherefore, a complete voltage range can be obtained on the pixel electrode to facilitate photoelectric modulation.

The content of the parent application US Application No. 08/770,233 filed on December 19, 1996 is incorporated in this article for reference.