Projection-type image display device

The present invention relates to a projection type image display device such as a liquid crystal projector. In particular, the focal state is detected by projecting light onto the projection surface and receiving the reflected light, and the detected light is the reflected light derived from the image projection light itself of the projection type image display device. Regarding the focus detection technology of the configuration.

Conventionally, the AF (autofocus = automatic focus adjustment) method of a projector is an active method that AFs based on the principle of triangular optical focus detection using infrared light, or a pair of light receiving line sensors that read the contrast of brightness on the screen. A passive method for driving a lens by obtaining a distance by obtaining a correlation value of the pixel output of the above is known.

Of these AF methods, the above passive method is roughly divided into two methods. So-called two-image correlation (or deviation detection) AF in which a contrast image such as an AF chart to be detected in focus is imaged on a plurality of photoelectric sensors arranged at a predetermined baseline length to acquire and compare image information. An image to be detected in focus is formed on a multi-pixel optical sensor having a method (see Patent Document 1) and a one-dimensional or two-dimensional pixel arrangement, and the image sharpness (= contrast) is detected from the image information. This is a method of finding the best state (mountain climbing) by driving the focal position of the lens that is forming an image on the sensor.

In addition to these, a technology is proposed that uses the characteristic that the projector itself projects an image, captures the projected specific image with a camera, and detects the focus by comparing the projected original image data with the captured image data. (See Patent Document 2).

When such a projector's own projected light is used for focus adjustment, the focus detection operation is unnecessarily erroneous by processing the same as the favorable brightness conditions, regardless of the brightness that is disadvantageous to passive AF. There is a possibility of doing.

For this reason, many techniques have been proposed for changing the determination algorithm, focus detection operation, method, and the like according to the brightness of the target object and the environment when performing focus detection (see Patent Documents 3 and 4).

Patent Document 3 describes a light emitting means that emits light projected onto an object, a light emitting output controlling means that controls the light emitting output of the light emitting means, and a light receiving light reflected from the object, and the object is received from the light receiving position. The first detecting means for measuring the distance to an object and the determining means for determining the variation of the distance measured a plurality of times in the first detecting means are provided, and the light emitting output controlling means is determined by the determining means. A focus detection device configured to increase the light emission output of the light emitting means when the variation is equal to or more than a predetermined value has been proposed.

Further, Patent Document 4 is a distance measuring device that measures the distance to a target object by projecting light and receiving the reflected light from the target object, and is a means for detecting the light receiving intensity level of the reflected light. A ranging device has been proposed in which the number of times of light emission and reception is determined according to the detected light reception intensity level, and the light reception and reception are controlled so as to repeat the number of times. In this device, the lower the light receiving intensity level, the greater the number of times the light is projected and received. In addition, the measurement result data is calculated by performing an average processing calculation based on the data obtained by receiving and receiving a plurality of times.<patcit num="1"><text>Japanese Patent No. 3120526 (paragraphs 0015 to 0017, Fig. 3, etc.)</text></patcit><patcit num="2"><text>Japanese Unexamined Patent Publication No. 2000-28901 (paragraphs 0022 to 0025, Fig. 2, etc.)</text></patcit><patcit num="3"><text>Japanese Patent No. 3272429 (paragraphs 0010 to 0013, Fig. 1, etc.)</text></patcit><patcit num="4"><text>Japanese Unexamined Patent Publication No. 2001-317935 (paragraphs 0013 to 0014, FIG. 2, etc.)</text></patcit>

<p> However, each of the above techniques assumes an infrared LED as a light source and a battery-powered device, and is suitable as a distance measuring or focus detecting method used in a projection type image display device such as a liquid crystal projector. , No technology has been proposed for improving AF accuracy.</p><p> Specifically, as proposed in Patent Document 3, when the light emitting output of the light emitting means is increased during AF, a projection type image display device such as a liquid crystal display illuminates an image forming element such as a liquid crystal panel. It is necessary to use a lamp corresponding to such output control, which causes problems such as cost increase, which is not realistic.</p><p> Further, as described above, in the projection type image display device, the reflected light from the projection screen is imaged on the sensor, and the AF of the projection optical system is performed based on the signal from the sensor. Even if it is high, if the original screen brightness (environmental brightness: the brightness of the area outside the projection screen during image projection) is high when the image is not projected, distance measurement (or distance measurement (or)) is performed on the screen. Contrast suitable for focus detection) cannot be obtained.</p><p> Therefore, the distance measuring device proposed in Patent Document 4 is applied to the projection type image display device, and the number of times and distance measurement according to the light receiving intensity level of the light (the sum of the projected light and the ambient light) from the projection screen are applied. (Or focus detection) may not be enough to obtain a contrast image suitable for distance measurement (or focus detection) on the sensor, and AF accuracy cannot be reliably improved.</p><p> The present invention provides a projection-type image display device that employs an AF method suitable for the usage conditions of the projection-type image display device and can suppress a problem that the AF accuracy deteriorates even in a bright environment. I am aiming.</p>

<p> In order to achieve the above object, in the present invention, the image forming means illuminated by the light from the light source, the projection optical system for projecting the light modulated by the image forming means onto the projection surface, and the distance to the projection surface. In a projection type image display device having a first detection means for detecting a light source or a focused state with respect to a projection surface of a projection optical system, the first detection means projects light projected through the projection optical system. It has a light receiving means that receives the reflected light from the surface and a light receiving level detecting means that detects the light receiving intensity level in the light receiving means, and determines the conditions of the detection operation according to the detection result by the light receiving level detecting means. Under that condition, the detection operation is performed.</p><p> Further, in the present invention, the image forming means illuminated by the light from the light source, the projection optical system that projects the light modulated by the image forming means onto the projection surface, and the light from the projection surface are received by the light receiving means. In a projection type image display device having a first detection means for detecting a distance to a projection surface or a focal state with respect to a projection surface of a projection optical system according to a signal from a light receiving means, the first detection means is The number of focus detection operations is determined according to the light source intensity level detected by the light receiving intensity level detecting means, and the focus detection operation is performed the number of times.</p><p> Further, in the present invention, light is projected onto a predetermined projection region on the projection surface, the reflected light from the projection surface is received by the light receiving means, and the distance to the projection surface is determined according to the signal from the light receiving means. In a projection type image display device having a first detection means for detecting or detecting a focal state with respect to a projection surface of a projection optical system, the first detection means is a light receiving level detecting means for detecting the light receiving intensity level of the reflected light. And an ambient light detecting means for detecting the intensity level of the ambient light, and the conditions of the detection operation are determined according to the detected intensity level of the ambient light or the difference between the intensity level of the ambient light and the intensity level of the reflected light. Under that condition, the detection operation is performed.</p><p> Further, in the present invention, light is continuously projected onto a predetermined projection region on the projection surface during one or a plurality of detection operations, and the reflected light from the projection surface is received by the light receiving means. In a projection type image display device having a first detection means that detects a distance to a projection surface or a focal state with respect to a projection surface body of a projection optical system in response to a signal from a light receiving means, the first detection means is described above. It has a light receiving level detecting means for detecting the light receiving intensity level of the reflected light and an ambient light detecting means for detecting the intensity level of the ambient light, and the detected ambient light intensity level or the ambient light and reflected light intensity level. The number of times of the focus detection operation is determined according to the difference between the two, and the detection operation is performed the number of times.</p><p> Further, in the present invention, light is projected onto a predetermined projection region on the projection surface, the light from the projection surface is received by the light receiving means, and the distance to the projection surface is detected according to the signal from the light receiving means. Alternatively, in a projection type image display device having a first detection means for detecting the focal state with respect to the projection surface of the projection optical system, the light receiving means sets the predetermined projection region and the non-projection region as the light receiving range, and at least each of them. It has a plurality of regions for individually obtaining the brightness information in the regions, and the first detection means operates the detection operation based on the brightness information of at least one region of the plurality of regions or the brightness information of both regions. A condition is determined, and the detection operation is performed under that condition.</p><p> Further, in the present invention, light is continuously projected onto a predetermined projection region on the projection surface during one or a plurality of focus detection operations, and the light from the projection surface is received by the light receiving means, and the light is received by the light receiving means. In a projection type image display device having a first detection means that detects a distance to a projection surface or a focal state with respect to a projection surface of a projection optical system in response to a signal from the light receiving means, the light receiving means is the above-mentioned predetermined projection. The region and the non-projection region are set as the light receiving range, and at least a plurality of regions for individually obtaining brightness information in each region are provided. Then, the first detection means determines the number of focus detection operations based on the brightness information of at least one region of the plurality of regions or the brightness information of both regions, and performs the focus detection operation the number of times.</p><p> Further, in the present invention, the image forming element that forms the original image, the projection optical system that projects the light from the image forming element onto the projection surface, and the distance or projection optical system to the projection surface using the light from the projection surface. A control means that detects the focal state of the projection surface and controls the drive of the focus lens included in the projection optical system according to the detection result, and receives light from the projection surface according to the light reception intensity level. It has a light receiving means for outputting a signal. Then, the control means obtains information on the brightness of the projected light with respect to the brightness of the ambient light on the projection surface based on the signal from the light receiving means, and determines the conditions for performing the detection operation based on the brightness information. , The detection operation is performed under the determined conditions.</p><p> Further, in the present invention, the image forming element that forms the original image, the projection optical system that projects the light from the image forming element onto the projection surface, and the distance to the projection surface using the light from the projection surface or the focal point of the projection optical system. A control means that performs a state detection operation and drives a focus lens included in the projection optical system according to the detection result of the detection operation, and a signal that receives light from the projection surface and corresponds to the light reception intensity level. It has a light receiving means for outputting. Then, the control means obtains information on the brightness of the projected light with respect to the brightness of the ambient light on the projection surface based on the signal from the light receiving means, determines the number of times to perform the detection operation based on the brightness information, and determines the number of times to perform the detection operation. The above detection operation is performed a determined number of times.</p><p> Further, in the present invention, the image forming element that forms the original image, the projection optical system that projects the light from the image forming element onto the projection surface, and the distance or projection optical system with respect to the projection surface using the light from the projection surface. A control means for detecting the focal state of the projection surface and controlling the drive of the focus lens included in the projection optical system according to the detection result, and light from the projection region and the non-projection region of the light on the projection surface. Each has a light receiving means for receiving light. Then, the control means determines the conditions for performing the detection operation based on the light receiving intensity level of the light received from the projection region and the light receiving region outside the projection by the light receiving means, and performs the detection operation under the determined conditions. A projection type image display device characterized by.</p><p> Further, in the present invention, the image forming element that forms the original image, the projection optical system that projects the light from the image forming element onto the projection surface, and the distance or projection optical system to the projection surface using the light from the projection surface. A control means for detecting the focal state of the projection surface and controlling the drive of the focus lens included in the projection optical system according to the detection result, and light from the projection region and the non-projection region of the light on the projection surface. Each has a light receiving means for receiving light. Then, the control means determines the number of times to perform the detection operation based on the light receiving intensity level of the light received from the projection region and the light receiving outside region received by the light receiving means, and performs the determined number of times and the detection operation.</p>

<p> As described above, according to the present invention, in the projection type image display device, high focus adjustment accuracy can be maintained even in a bright environment.</p><p> In particular, by obtaining the brightness of the projected light with respect to the ambient light and setting the conditions (number of times) for distance detection or focus detection according to the brightness, appropriate distance detection or focus detection for various usage conditions is performed. The movement can be performed and the focus adjustment accuracy can be ensured.</p><p> When the light receiving intensity level detected by the light receiving level detecting means or the brightness information by the projected light with respect to the ambient light is within a predetermined range, the number of detections as a condition of the detection operation is set to the minimum number of times. As a result, it is possible to quickly obtain the focus on the projection surface. Further, when the light receiving intensity level or the brightness information is out of the predetermined range, the farther away from the predetermined range, the more the number of detections as a condition of the detection operation is increased, or the light receiving accumulation time for detection is determined by the brightness information. By making the accumulation time shorter than the accumulation time when it is within the range and increasing the signal gain, or by increasing the number of bits when A / D conversion of the detected output signal is made than the number of bits when the brightness information is within the predetermined range. The amount and accuracy of the detected signal can be increased, and the focus adjustment accuracy can be improved regardless of the light receiving intensity level or the brightness information.</p>

Hereinafter, examples of the present invention will be described.

FIG. 1 shows the configuration of a three-panel liquid crystal projector (projection type image display device) with AF, which is the first embodiment of the present invention.

In FIG. 1, 100 is a liquid crystal projector. 110 is a light source, 120 is a transmissive liquid crystal display panel, 130 is a cross dichroic prism, 140 is a zoom projection lens (projection optical system), 150 is a motor driver, 160 is a microcomputer (hereinafter referred to as a microcomputer: control means), 170 is. Operation panel, 180 is an image signal supply device such as a personal computer (PC), video, DVD player, TV tuner, 190 is an image processing circuit, 200 is a screen, 300 is a passive AF sensor (first detection means, light receiving means) Is.

The basic configuration of the projector 10 is a general configuration as a three-panel liquid crystal projector. That is, three transmissive liquid crystal display panels 120 (only one channel is displayed in the figure) are used, and a dichroic mirror (not shown) is used from a light source (high-pressure mercury lamp, metal halide lamp, xenon lamp, etc.) 110. The illumination light is separated into three channels of color light components of red R, green G, and blue B, and the three liquid crystal display panels 120 are illuminated respectively.

The liquid crystal display panel 120 is driven by the LCD driver 121 based on the image signal supplied from the image signal supply device 180, and displays the original image for each channel corresponding to the image signal. Then, when the separated color light components are incident on the liquid crystal display panel 120, these light components are modulated according to the original image and emitted from the liquid crystal display panel 120.

The color light components transmitted through each liquid crystal display panel 120 are color-synthesized by the cross dichroic prism 130 so that the optical axes match, and are magnified and projected onto the screen 200 by the projection lens 140.

The optical axis 102 of the projection lens 140 is shifted (rise) upward with respect to the optical axis 101 of the illumination system as shown by reference numeral 145. By arranging the lens optical axis 102 by shifting it in this way, the image projected on the screen 200 is projected upward with respect to the lens optical axis 102, and when the projector is placed on a desk and projected, the screen by the desk is projected. You can reduce the eclipse.

The projection lens 140 is a zoom lens, and the projection angle of view changes as indicated by an arrow on the screen 200 during zooming. Since the distance from the optical axis 102 of the projection lens 140 to the screen edge is proportionally enlarged or reduced by the zoom variable magnification, the movement of the screen edge is relatively small at the lower side near the optical axis 102.

A focus operation ring 146 and a zoom operation ring 147 having an outer peripheral gear portion are provided on the outer periphery of the projection lens 140, and the focus lens 148 and the variable magnification lens (not shown) are driven by rotation thereof, respectively. Adjust the focus and angle of view.

The output pinion gears of the focus motor 141 and the zoom motor 143, which are geared motors integrated in the reduction unit for electric drive, are meshed with these two operation rings 146,147, and the electric drive is performed by the output of the motors 141, 143. Be struck. It is also possible to perform zooming and focusing by manually operating the focus operation ring 146 and the zoom operation ring 147.

Potentiometer type rotary encoders 142,144 are connected to the outer gears of the operation rings 146,147 via pinion gears in order to detect the absolute position (indirectly the absolute position of the lens). A signal indicating the position of the focus lens 148 and the position of the variable magnification lens is output to the microcomputer 160.

The focus motor 141 and the zoom motor 142 are driven and controlled by the microcomputer 160 via the motor driver 150.

The image projected by the projector 100 is used for an image based on the image signal from the image signal supply device 180 described above and an OSD (on-screen display) display such as an operation mode that is often installed in recent projectors. The switching circuit 6 selects from either an image based on an image signal from the character generator 7 or an image based on an image signal in a memory (not shown). The selected image signal is subjected to resolution conversion, gamma processing, non-tarrace processing, etc. by the image processing circuit 190 according to the type of the image signal, and is displayed on the liquid crystal display panel 120 via the LCD driver 121 for each RGB channel.

The operation panel 170 is arranged on the outer surface of the projector 100, and power ON / OFF, selection of the source of the projected image (that is, the original image), electric zoom operation, electric focus operation, autofocus ON / OFF operation, various mode settings. The switches that perform the above are centrally arranged.

FIG. 2 shows a schematic configuration of the passive AF sensor 300 in this embodiment. The passive AF sensor 300 is from the lower side of the area (projection area) on which the image is projected on the screen 200, that is, from both ranges (fields of view) including the boundary between the projection area and the non-projection area where the image is not projected. Receives reflected light.

The passive AF sensor 300 captures the reflected light through a pair of lenses 31 and 32 arranged at a predetermined distance as a baseline length, and captures two light beams incident from each lens into a pair of mirrors 33 and 34 and a prism. It is configured to reflect light on each of the pair of 35 reflecting surfaces and guide it to the pair of line sensors 36 and 37 to receive light.

The passive AF sensor 300 is arranged in the vicinity of the projection lens 140, and the base line length direction extends in the vertical direction so that the field of view extends over a part of the lower side of the image projection area on the screen 200. The center axis of the field of view is arranged so as to be substantially parallel to the optical axis 102 of the projection lens 140.

By arranging the passive AF sensor 300 in this way, there is very little waste in terms of space efficiency in arranging the AF sensor unit, which is generally configured in a substantially square columnar shape, in the projector 100.

FIG. 3 shows a circuit configuration (first detection means) related to AF control performed by the projector 100 of this embodiment.

The microcomputer 160 controls the entire projector 100 and also controls the AF. In addition to the CPU 41, the microcomputer 160 has a memory A42, a memory B43, a shift register 44, and a ROM 44 (the microcomputer 160 and the passive AF sensor 300 correspond to the first detection means of the claim).

The output (for example, voltage value) of each pixel of the line sensors 36 and 37 (plural pixels of each of the line sensors 36 and 37 shown in FIG. 2) is, for example, an 8-bit digital signal (for example, an 8-bit digital signal) by an A / D converter (not shown). Information) is converted. By changing the storage time in each pixel or the gain according to the signal level output by each pixel, the saturation of the storage of each pixel is prevented and the dynamic range of the signal is expanded.

Here, the memory A42 and the memory B43 individually store the image signals (the above-mentioned digital signals) photoelectrically converted by the line sensors 36 and 37 of the above-mentioned passive AF sensor 300.

For example, the image data of the memory A42 is input to the shift register 44, and the shift register 44 operates so as to sequentially shift the input data. Then, the CPU 41 compares the data in the shift register 44 with the data in the memory B43 to detect a match between the two data, collates the shift amount at this time with the contents of the ROM 45, obtains the distance to the screen 200, and focuses. Send the output to drive the lens 148 (see Figure 1) to the motor driver 150.

The ROM 45 here stores the relationship between the shift amount of the shift register 44 and the distance to the screen 200 as table data. In addition, a plurality of these table data are prepared to enable table selection using temperature as a parameter, and a temperature sensor (not shown) is added near the passive AF sensor 300 in the projector 100 to drive the focus fluctuation due to temperature by the lens. It can also be configured to be reduced by selecting a quantity calculation table or a drive amount calculation coefficient table.

As a result, good AF accuracy can be ensured in a projector in which the temperature tends to rise.

Reference numeral 5 is an AF switch, which is provided on the operation panel 170. The operation of the AF switch 5 is sent to the switching circuit 6 via the microcomputer 160. In response to the operation of the AF switch 5, the switching circuit 6 projects an image signal that is the source of the original image displayed on the liquid crystal display panel 120 from the video signal using the hardware background generation function of the character generator 7. I am trying to switch to a signal for displaying an image.

In this case, the character generator 7 sends an image signal indicating an all-white image, an all-ash image, or an AF detection image equivalent thereto having no pattern for displaying non-background characters to the LCD driver 121 according to the instruction of the microcomputer 160. A detection original image corresponding to the AF detection image is displayed on the liquid crystal display panel 120.

Next, the AF operation in the projector 100 configured as described above will be described. It is desirable that this AF operation be performed prior to the projection display of a normal video image.

First, when the AF switch 5 provided on the operation panel 170 is operated, the output of the character generator 7 is selected by the switching circuit 6, and the microcomputer 160 sends the output contents of the character generator 7 to the LCD driver 121. As a result, the above-mentioned original image for AF detection is displayed on the liquid crystal display panel 120, and the image for AF detection is projected on the screen 200.

Here, the optical axis 102 of the projection lens 140 is shifted to a position where the ratio of 1 upward and 19 downward in the vertical dimension of the effective display range of the liquid crystal display panel 120. Therefore, the projected image on the screen 200 is shifted so as to have a ratio of 19 upward and 1 downward with respect to the optical axis 102 of the projection lens 140, and is projected with an apparent elevation angle so as not to be distorted. To.

The viewing angle of the passive AF sensor 300 is set to about 10 degrees in the baseline length direction, and the lower side of the projected image is included in the field of view.

At the boundary between the projection (in-screen) area and the outside-projection (out-of-screen) area of the image on the screen 200, for example, an all-white image and a black-level image with the highest brightness that can be projected were projected. The off-screen area with lower brightness than the case will be adjacent.

Here, the black level image becomes brighter than the off-screen area because it is a general characteristic of the transmissive liquid crystal display panel 120 used in this embodiment, and leakage light is always present even in a completely shaded state. Is. In addition, the flare of the projection lens 140 and the leaked light around the dichroic prism 130 inevitably brighten the black level image on the screen.

Contrast reduction factors caused by these optical systems are any of display elements other than transmissive liquid crystal display elements, such as reflective micromirror drive elements, reflective liquid crystal display elements such as LCOS, and self-luminous image display elements such as EL elements. The same applies to the image display element of. Therefore, in a projector using these image display elements, in general, the black level portion in the screen is always brighter than the outside of the screen.

On the other hand, since the lower side of the projected image is located close to the lens optical axis 102, there is no drop in peripheral illumination, and it is also a place where the brightest white display can be easily obtained in the entire projection screen.

Therefore, by putting this position in the sensor field of view and obtaining the sensor output, the boundary shows the highest contrast that can be created by the projection of the projector. Even when the projected image is an all-gray image, the brightness of the non-projected region is low, so that a sufficiently high contrast can be obtained in the visual field.

Further, even if the projection lens 140 is zoomed between the telephoto end and the wide end, the position fluctuation of the lower side of the screen is small as described above, and the center of the sensor field of view in the baseline length direction (optical axis) is moved up and down. The boundary is always included in the sensor field of view, even if it is not adjusted to.

The reflected light from the sensor field of view incident on the passive AF sensor 300 is received by the line sensors 36 and 37 via the lenses 31, 32, mirrors 33, 34 and prism 35 described above, respectively.

Then, the image signals photoelectrically converted by the pixels of the line sensors 36 and 37 are stored in the memory A42 and the memory B43 of the microcomputer 160, respectively.

FIG. 4 shows a two-image correlation ranging method using the correlation of two images formed on the line sensor 36 and the line sensor 37.

Images in the field of view are formed on the line sensor 36 and the line sensor 37 as shown in FIGS. 4 (a) and 4 (b), respectively. The signal shown in d) is output. Image data as shown in FIGS. 4 (e) and 4 (f) corresponding to the output signals shown in FIGS. 4 (c) and 4 (d) are stored in the memory A42 and the memory B43, respectively.

Then, as shown in FIG. 6G, the data of the memory A42 is input to the shift register 44, and the contents of the shift register 44 are sequentially shifted in the direction of the arrow in the figure.

In this state, the CPU 41 compares the data pattern of the shift register 44 with the data pattern of the memory B43 (see FIG. 4 (h)), minimizes the known difference (= OR-AND), and maximizes the AND. When a match between both data patterns is detected by a determination method such as minimizing OR, the shift amount at this time is collated with the stored contents of the ROM 45, and the distance to the screen 200 is obtained.

If necessary, the accuracy of the optical ranging used in this embodiment is improved by performing the correlation comparison processing (differential processing) after taking the difference amount of each adjacent pixel data as the data to be collated and compared. To do.

The data for which the difference is to be taken may be the difference of one skip or the difference of n skips instead of the adjacent data. Further, the correlation comparison process may be performed after calculating a data group obtained by adding a plurality of consecutive data at a predetermined interval (inside).

Further, by outputting the obtained distance data to the motor driver 150, the focus lens 148 (see FIG. 1) is driven and focusing (focus adjustment) is performed.

In this way, by selecting an image generated by the hardware in advance and projecting this image on the screen 200 to enable AF control, the accuracy of focus adjustment (focus adjustment accuracy () without using extra memory. Focusing accuracy) can be significantly improved, and the cost burden can be reduced.

In this embodiment, the case where the hardware-generated image by the character generator 7 for OSD (on-screen display), which is standardly equipped as a projector function for AF detection, is projected to perform AF control has been described. AF control can also be performed in the same manner when a DVD moving image or a computer monitor image based on an image signal from the image signal supply device 180 such as a normal video image is projected.

FIG. 5 is a flowchart showing the AF operation in this embodiment. Hereinafter, the operations related to the AF operation of the microcomputer 160 (CPU41) will be described with reference to this figure.

In FIG. 5, when the power switch of the operation panel 170 is turned on (powered on) (step (hereinafter referred to as S) 101), the microcomputer 160 is initialized (S102), and then a light source control circuit (not shown) is used. Is activated, a ballast (not shown) is operated to generate a high voltage required to light the light source 110 (here, a high-voltage mercury lamp), and the voltage is applied to the electrodes of the light source 110. As a result, the lighting of the light source 110 is started (S103).

After the light source 110 is turned on, during the period of the steps shown in FIG. 5, the all-white image by the function of the character generator 7 is projected on the screen 200 until the switching circuit 6 switches to the external input image. A character indicating that the initial mode such as "preparing" is projected outside the field of view of the passive AF sensor 300 with an all-white image as a background.

The projected image (initial projected image) at this time is automatically executed according to this flowchart by a known timer circuit. It detects the passage of a predetermined time after the completion of the first AF drive and increases the brightness of the light source 110. FIG. 3 shows automatically when the monitor detects that the predetermined brightness has been reached, or optionally by the user operating an input selection button (not shown) provided on the operation panel 170. When an image signal from the outside (image signal supply device 180) is input by the switching circuit 6, the external input image is switched to.

By making it possible to switch images by accepting such user operations, we would like to confirm the contents of the projected image as soon as possible when the projector 100 is fixedly installed in a conference room or the like and initial installation preparation is not required. It is possible to respond to the user's intention.

Further, as described with reference to FIG. 2, when the AF switch 5 provided on the operation panel 170 is operated at any time, the output of the character generator 7 is selected again by the switching circuit 6, and the microcomputer 160 is the character generator 7. Send the output contents to the LCD driver 121.

By this interrupt treatment, the above-mentioned original image for AF detection is displayed on the liquid crystal display panel 120, the image for AF detection is projected on the screen 200, and even in that case, the operation is performed by looping to S104 described later.

In S104, the passive AF sensor shown in FIGS. 1 and 2 (here, the line CCD type is assumed) 300 has the lower side of the area (projection area) on which the image is projected on the screen 200, that is, the projection area. The reflected light is received from both regions (fields) including the boundary with the non-projection region where the image is not projected, and the charge accumulation for each pixel of at least one of the line sensor 36 and the line sensor 37 and the A of the charge are received. The / D conversion is performed, and the brightness inside / outside the screen is determined from the A / D conversion value (light receiving intensity level) (S105). That is, in this embodiment, the passive AF sensor 300 is also used as the light receiving means for determining the brightness.

Here, on the line sensor, disk because where the light from the light and the projection outside the region of the projection region within the field of view set on the lean 200 is incident, from the A / D conversion value for each said pixel, Brightness of the projection area on the screen 200 (brightness of the sum of the projection light from the projection lens 140 and the ambient light existing in the projection environment of the screen 200 and its surroundings other than the projection light) and the brightness of the non-projection region. (Brightness due to ambient light) can be detected. Then, in this embodiment, the brightness ratio information indicating the relationship between the brightness due to the ambient light and the brightness due to the projected light on the screen 200 is obtained from the detected brightness.

For example, if the brightness of the projection area (illuminance in this case) is 2000lx and the brightness of the non-projection area is 500lx, the brightness of the projection light is 1500lx (= 2000-500lx) and the brightness of the ambient light is It is 500lx. Therefore, the brightness ratio = brightness due to projected light: brightness due to ambient light is 3: 1.

The brightness ratio obtained here may indicate the ratio between the brightness of the projection region (brightness due to the projected light + ambient light) and the brightness of the outside region (brightness due to the ambient light). In the case of the above specific example, the brightness of the projection area: the brightness of the non-projection area is 4: 1.

Then, the obtained brightness ratio (for example, 3: 1) is compared with the determination threshold table stored in the memory (ROM45) of the microcomputer 160.

Here, FIG. 6 shows a conceptual diagram of the determination threshold table. A in the figure is a detectable region in which 2: 1 is the lower limit value and the predetermined ratio is the upper limit value in the range in which the brightness ratio can be taken, and a contrast suitable for the above-mentioned distance measurement operation can be obtained. The area.

The lower limit value referred to here is only an example, and may be another value. Further, the lower limit value and the upper limit value may be variable. When the brightness ratio is obtained as the ratio between the brightness of the projection region and the brightness of the non-projection region, for example, 4: 1 may be set as the lower limit value.

Then, when the obtained brightness ratio is within the detectable region A (for example, when the brightness ratio is 3: 1), the process proceeds to S111 as a good brightness ratio, and the minimum distance measurement is performed. The above-mentioned distance measurement operation is performed only once, which is the number of times (that is, the number of distance measurement is determined to be one). Then, the distance to the screen 200 is calculated using the distance measurement result (S112).

On the other hand, when the brightness ratio is outside the detectable region A (for example, when the brightness ratio is 1.5: 1), the brightness ratio proceeds to S106 as an unfavorable brightness ratio, and the smaller the brightness ratio (that is, the smaller the brightness ratio). The number of distance measurements is determined to be larger (the farther away from the detectable region A or the higher the light receiving intensity level of the ambient light in the non-projection region). In this step, a counter (not shown) in the microcomputer 160 that counts the number of distance measurements is initialized (set to 0).

The number of times of distance measurement is determined by using the number of times table shown in FIG. 6 stored in the memory (ROM45) of the microcomputer 160. This number of times table shows the relationship between the brightness ratio outside the detectable area A and the number of distance measurements, and the number of distance measurements is determined by reading the number of distance measurements according to the brightness ratio from this number of times table. To do.

As a result, for example, the smaller the brightness ratio exceeds 2: 1, the greater the number of distance measurements is determined, such as 3 times, 5 times, and so on.

This is because the brightness due to the projected light is insufficient with respect to the brightness due to the ambient light, and the brightness ratio is less than 2: 1. If the brightness on the screen 200 due to the projected light becomes darker than 250 lx and the brightness due to the projected light cannot be detected, the distance measurement accuracy will decrease, so the number of distance measurements will be increased. Is what you do.

If the brightness ratio exceeds a predetermined ratio (upper limit value), distance measurement is not performed as a brightness ratio state that cannot normally occur.

Further, the minimum number of distance measurement and the number of distance measurement to be increased described above are both examples, and may be other times or may be variable.

When the number of distance measurement is determined in S106, the process proceeds to S107 and the distance measurement operation described above is performed. Each time the distance measurement operation is performed, the distance measurement value is stored in a RAM (not shown) in the microcomputer 160, the counter value (remaining distance measurement) is decremented by 1 (S108), and the counter value becomes 0 in S109. The distance measurement operation, storage of the distance measurement value (S107), and decrementing of the counter value (S108) are repeated until.

When the counter value becomes 0 in S109, the average processing of the distance measurement values stored in the RAM in S110 is performed by a known method, and the distance to the screen 200 is calculated based on the average processing distance measurement data. (S112).

From S112, proceed to S113, calculate the motor drive amount based on the distance to the screen 200 calculated in S112 and the current position information of the focus lens 148 detected by the focus encoder 142, and determine the drive amount. (S114).

When the drive amount is zero, the focus is already in focus, and the process proceeds to the next step (for example, switching the switching circuit 6 to capture the image signal from the image signal supply device 180) (S116). When the drive amount is not zero, the focus motor 141 is driven to adjust the focus while monitoring the position of the focus lens 148 detected by the focus encoder 142 (S115). Then, return to S104.

In this embodiment, the detection of the distance to the screen 200 by the output from the passive AF sensor 300 has been described as "distance measurement", but the phase difference detection method is used by the two-image correlation calculation by the passive AF sensor 300. It is also possible to detect the defocus amount (focus state) of the projection lens 140. Then, based on this defocus amount, it is possible to calculate the drive amount of the focus lens 148 for obtaining focus. Therefore, by setting the "distance measurement" in FIG. 5 to "focus state detection (focus detection)", the AF operation by the so-called phase difference detection method can be performed.

Further, in this embodiment, AF of a so-called contrast detection method (mountain climbing method) can be performed. In this case, while driving the focus lens 148, the position of the focus lens 148 where the maximum peak value of the high frequency component of the output signal from the passive AF sensor 300 can be obtained is searched for and the focus is obtained, and this maximum peak value can be obtained. The position search operation of the focus lens 148 is performed once when the brightness ratio is in the intermediate region. On the other hand, when it is outside the intermediate region, it may be performed a plurality of times (more as the distance from the intermediate region increases), and the average position of each memorized search position may be set as the final focusing position.

FIG. 7 shows the configuration of a three-panel liquid crystal projector (projection type image display device) with AF, which is the second embodiment of the present invention.

In the first embodiment, the case where the passive AF sensor for distance measurement (or focus detection) is also used as the sensor for detecting the brightness of the projection region and the non-projection region has been described, but in this embodiment, the dedicated brightness is used. You are using a detection sensor.

In FIG. 7, 400 is a projector, 440 is a projection lens, and 300 is a passive AF sensor similar to that described in Example 1.

300a is the field of view of the passive AF sensor 300, and C is the AF chart projected from the projection lens 440 so that the field of view 300a includes a part of the field of view.

Reference numeral 410 denotes a projection region light receiving intensity sensor (light receiving means) that receives the reflected light from the projection region P of the image by the projection lens 440 on the screen 200 and outputs a signal according to the brightness (light receiving intensity level). 410a is the field of view of the projection region light receiving intensity sensor 410 (the range on the screen 200 where the light received by the sensor 410 is reflected). In this embodiment, the image is projected on the screen 200 so that the AF chart C is displayed near the optical axis position of the projection lens 440 against the background of the white image. The field of view 410a of the projection area light receiving intensity sensor 410 is set in the vicinity of the side of the AF chart C (the range not including the AF chart C) in the projection area P.

Further, 420 is an extra-projection region light-receiving intensity sensor (light-receiving means) that receives reflected light from the non-projection region (the region outside the projection region P) and outputs a signal according to the brightness (light-receiving intensity level). .. 420a is the field of view of the light receiving intensity sensor 420 outside the projection region (in this embodiment, the screen 200 on which the light received by the sensor 420 is reflected and the range outside the screen).

In this embodiment, the relationship (brightness) of the brightness due to the projected light from the projection lens 440 with respect to the brightness due to the ambient light from the output from the projection region light receiving intensity sensor 410 and the output from the projection outside region light receiving intensity sensor 420. The ratio) is obtained, and the number of distance measurements (or focus detection) is determined based on the brightness ratio by the same method as in Example 1.

FIG. 8 shows the configuration of the 3-panel LCD projector (projection type image display device) 400'with AF, which is the third embodiment of the present invention.

In this embodiment, a sharpness detection method (so-called blur method or contrast detection method) is adopted as the AF method, and the sharpness detection type is used instead of the two-image correlation detection type passive AF sensor 300 shown in the third embodiment. AF sensor 500 is used.

Reference numeral 500a is a field of view of the AF sensor 500, and the field of view 500a is set so as to include a part of the AF chart C projected from the projection lens 440.

Then, apart from the AF sensor 500, the projection region light receiving intensity sensor 410 and the non-projection region light receiving intensity sensor 420 described in the third embodiment are used. The same elements as in the third embodiment are designated by the same reference numerals as those in the third embodiment, and the description is substituted.

The operation according to the present invention on the projector 400'of the present embodiment is as described in the first embodiment.

(Example 4) In Examples 1 to 3 above, the brightness of the projection area and the brightness of the non-projection area of the image are detected, and the relationship between the brightness due to the projected light and the brightness due to the ambient light (brightness) is obtained from these detection results. Although the case of obtaining the ratio) has been described, it is possible to obtain the above-mentioned brightness ratio without necessarily detecting the brightness of the non-projection region. This will be described below.

FIG. 9 is an explanatory diagram of the projection brightness of the projector. It is shown that the normal projection distance in a small projector having a projection brightness of 1000 ANSilm is limited to a very limited distance due to the projection brightness and the screen size. Specifically, the practical brightness projection range is a 40 to 100 inch screen, and the brightness due to projection is 2000 lx to 250 lx when considered in a limited way.

Therefore, when the brightness detected in the projected screen of the white screen is equivalent to 4000 lx, the brightness due to the projected light at the normal distance is at most half of that, and the brightness due to the ambient light is more than half. Become.

Further, when the ambient light becomes brighter, the contrast becomes lower, so that the number of distance measurement (focus detection) is increased. In this case, a warning indicating that the surrounding environment is too bright may be displayed or sounded.

The determination of the maximum brightness environment can be performed only by detecting the brightness in the screen. In this case, the black-and-white contrast on the screen is lower than 2: 1.

Also, if the detected brightness is 2000 to 4000 lx, there are various possibilities for ambient light from zero to 3750 lx. Furthermore, if the detected brightness is 250 to 2000 lx, there are various possibilities for ambient light from zero to 2000 lx.

In these ranges, ambient light is removed and judged by measuring the brightness inside and outside the screen. If the brightness ratio is 2: 1 or more, it is considered to be within the detectable area A, and the minimum number of times and distance measurement (focus). Detect). When the brightness ratio is less than 2: 1 and when the detected brightness becomes a darker value at 250 lx or less, the detection accuracy is further lowered, so the number of distance measurement (focus detection) is increased. At this time, a warning to the user that the projection is a long distance may be displayed or sounded.

As explained above, when the projector is in use, the brightness of the screen during image projection = the brightness of the projected light at the normal operating distance + the brightness of the ambient light that does not interfere with the image projection is within the specified range. .. Then, when the projected image is a chart in which a part of the black pattern is arranged on the entire white surface or a white background, which is the maximum brightness by the projector, the projected brightness is further limited to a limited value, so that the predetermined range becomes narrower.

Therefore, by evaluating the absolute value of brightness, if brightness that is bright like a window in the daytime and cannot be reached without ambient light above a predetermined level is detected, low contrast is detected even before distance measurement (focus detection). Therefore, it is possible to increase the number of distance measurement (focus detection) and improve the focusing accuracy.

Further, when a brightness range (detectable range A) that is darker than the above predetermined range and is greater than or equal to the brightness obtained by the projector at a normal operating distance in a dark room environment is detected, the projection distance is suitable for image projection ( Assuming that it is a normal distance (which can be expected to be used under the condition that the user thinks "let's project an image" at least), the ambient light is in a good condition that is advantageous for distance measurement (focus detection). Know in advance. Therefore, it can be expected that the contrast is likely to be good, the number of times of light reception and distance measurement (focus detection) can be reduced, and the distance measurement operation can be completed quickly.

Further, when the detected brightness ratio is smaller than the above-mentioned detectable range A, the brightness is such that the screen becomes dark when the room is in a dark room with almost no ambient light and the projected light is dark. It is possible to specify that it is a screen projection, and in this case as well, the focusing accuracy can be improved by increasing the number of distance measurement (focus detection).

By adopting such a mechanism in a video projector or an AV system including the video projector, it is possible to speed up the focus adjustment operation while maintaining high focusing accuracy during use. Therefore, the performance of the entire system is improved, it is easy for beginners to handle, and the commercial value is enhanced.

In each of the above-described embodiments, the case where the number of distance measurement is changed according to the light receiving intensity level has been described, but the configuration is not limited to this as a configuration for improving the distance measurement and the detection accuracy of the focal state. For example, depending on the light receiving intensity level, i) the higher the light receiving intensity level (brighter), the shorter the accumulation time in each pixel of the line sensors 36 and 37, and the higher the gain to prevent saturation of the accumulation of each pixel. Configuration to improve the accuracy of the output signal, ii) The higher the light receiving intensity level (brighter), the more A / D conversion when converting the output signal (analog signal) from multiple pixels of the line sensors 36 and 37 into a digital signal. Configuration that improves the accuracy (information amount) of the output signal by increasing the number of conversion bits in the device (for example, changing 8 bits to 16 bits) to increase the amount of information in the digital signal, iii) Line sensors 36, 37 A line sensor having a plurality of pixels obtained by further dividing the pixel pitch of the above may be used, and the number of output signals from the line sensor may be increased to improve the accuracy of the output information.

<figref num="1">The figure which shows the structure of the AF liquid crystal projector which is Example 1 of this invention.</figref><figref num="2">The figure which shows the structure of the AF sensor part of Example 1.</figref><figref num="3">The figure which shows the schematic structure of the AF circuit of Example 1.</figref><figref num="4">Explanatory drawing of the two-image correlation distance measurement method.</figref><figref num="5">The flowchart which shows the operation of Example 1.</figref><figref num="6">The conceptual diagram which shows the distance measurement number setting of Example 1.</figref><figref num="7">The figure which shows the structure of the AF liquid crystal projector which is Example 2 of this invention.</figref><figref num="8">The figure which shows the structure of the AF liquid crystal projector which is Example 3 of this invention.</figref><figref num="9">Explanatory drawing of the brightness of the screen of the projector.</figref>

Code description

100 LCD projector 101 Optical axis of lighting system 102 Optical axis of projection lens 110 Light source 120 Transmissive liquid crystal display panel 130 Cross dichroic prism 140 Zoom projection lens (projection optical system) 150 Motor driver 160 Microcomputer 170 Operation panel 180 Image signal supply device 190 Image processing circuit 200 Screen 300 Passive AF sensor