Capacitive touch sensor architecture with unique sensor bar addressing

Capacitive touch sensor architecture with unique sensor strip addressing

FIELD OF THE INVENTION The present invention relates to capacitive touch sensor architectures. More specifically, the present invention relates to a capacitive touch sensor capable of providing a fairly accurate control signal indicating where the screen or sensor is touched.

BACKGROUND OF THE INVENTION Touch screens are used together with various displays including cathode ray tubes (such as CRT) and liquid crystal displays (such as LCD screens) as a device for inputting information to a computer system. When placed on the display screen, the touch screen allows the user to select the displayed icon or element by touching the screen position corresponding to the desired icon or element. As computers and other electronic devices become more and more popular, touch screens are becoming more and more common data input interfaces. For example, nowadays, touch screens can be found in workshops, warehouses, production equipment, restaurants, handheld personal digital assistants, automatic teller machines, and playground game machines.

One type of touch screen, the capacitive touch screen, includes a capacitive sensor circuit having a plurality of sensor bars, each sensor bar generating an electric field. Usually, but not necessarily, an optically transparent protective material such as window glass is used to laminate the sensor circuit. Touches adjacent to one or more sensor bars modulate the electric field and generate a signal. A lead line network that electrically connects the sensor circuit to the controller is used to transmit this signal from the sensor strip to the controller. The controller parses the signal to determine the position of the touch screen. The XY coordinates of the position can then be transmitted to another processor for further processing, for example, to a computer for inputting an order for displaying and selecting items on the screen.

The traditional capacitive touch sensor architecture affects the ability to accurately resolve the touch position. Traditionally, each lead connecting the sensor bar to the controller is connected to multiple sensor bars. For this reason, the signal on a certain lead may indicate a touch on more than one single sensor strip. The layout used in the traditional contact sensor design is to compare the signal appearing on the lead at one end with the signal appearing on the lead at the other end. The comparison enables the controller to resolve which of the plurality of sensor bars actually experienced the touch. In other words, a traditional touch sensor couples a different set of leads to each end of the sensor bar, so that the signal present on one end of the touch sensor and the signal present on the other end together uniquely define each sensor bar.

The problem faced by designers of touch screens is to design and manufacture touch screens and sensor circuits that are economical and can accurately establish touch positions.

SUMMARY OF THE INVENTION The present invention is directed to an apparatus and method for providing an improved capacitive touch screen. The present invention includes multiple parallel sensor strips configured for deployment on the screen. In one aspect, the present invention provides a symmetrical architecture in which each sensing bar is connected to a unique pair of leads, one end of the sensing bar is connected to one of the pair of leads, and the other One end is connected to the other lead of the pair of leads.

In another aspect, the present invention can be configured to reduce the space occupied by the leads on each end of the contact sensor. The present invention configures the leads so that the sum of the leads arranged along the two opposite sides of the sensor is approximately equal to the number of sensor bars.

In yet another aspect, the number of leads in the first set of leads is substantially equal to the number of leads in the second set of leads. The sensor bar of the touch sensor is oriented parallel to the tail circuit. By routing the leads from one end of the sensor bar along both sides of the contact sensor, the amount of space required on both sides of the contact sensor is reduced, so that the main device can be made smaller without reducing the size of the contact sensor. Or the contact sensor can be made slightly larger without affecting the size of the main device.

BRIEF DESCRIPTION OF THE DRAWINGS When combined with schematic but not to scale drawings, by referring to the following detailed description, it will be easier to understand the above aspects of the present invention and many of the accompanying advantages. In the drawings: Figure 1 is an illustration A schematic diagram of an exemplary system overview; FIG. 2 is a schematic diagram of an exemplary capacitive touch sensor according to the present invention; FIG. 3 is a schematic diagram of an embodiment of a part of a touch sensor according to the present invention; FIGS. 4a and 4b are according to the present invention A schematic view of a part of the contact sensor of an alternative embodiment;

Fig. 5 is a schematic diagram of a touch on a sensor bar in a touch sensor; Figs. 6a-6c are schematic diagrams showing signal amplitude plots for four adjacent sensor bars.

Detailed Description of Preferred Embodiments In the following detailed description of exemplary embodiments of the present invention, reference is made to the accompanying drawings constituting a part of the present invention. The detailed description and accompanying drawings illustrate specific exemplary embodiments in which the invention may be implemented. The detailed description of these embodiments is sufficient to enable those skilled in the art to implement the present invention. It is to be understood that other embodiments may be adopted, and other changes may be made without departing from the spirit and scope of the present invention. Therefore, the following detailed description should not be construed as restrictive, and the scope of the present invention is defined only by the appended claims.

Throughout the specification and claims, unless clearly indicated otherwise, the following terms adopt the meanings clearly associated with them. The meanings of "one (one)" and "the" include plural references. The meaning of "in" includes "in" and "on". Regarding the drawings, the same reference numerals denote the same parts throughout the drawings. In addition, unless otherwise indicated or unless inconsistent with the disclosure herein, references to the singular number include references to the plural number.

In short, the present invention relates to a capacitive touch sensor architecture with separate lead connections to each of a plurality of sensor strips. The present invention can accurately analyze the touch position. The coordinates along the sensor bar are determined by the ratio of the left signal and the right signal received from the touched sensor bar. The imbalance in electrical characteristics between the left and right parts of the sensor bar and its leads may cause inaccuracies in the ratio, which may adversely affect the determination of the touch position. The touch sensor architecture of the present invention provides symmetrical or balanced electrical characteristics of the sensor bar and its leads by connecting each sensor bar to a unique pair of leads. The electrical signal from the touched sensor strip and its only lead can be used by the controller to determine the touch position according to any appropriate method.

Fig. 1 is a schematic diagram illustrating the general operating principle of a capacitive touch sensor. In FIG. 1, the touch screen system 100 includes a touch sensor 101, a controller 122, and a computer 126. In this particular embodiment, in addition to the standard glass layer, the touch sensor 101 also includes a capacitive touch sensing layer, such as a capacitive touch sensing layer constructed in accordance with the present invention.

In operation, the controller 122 provides an excitation waveform to the capacitive touch sensing layer of the touch sensor 101 to generate an electric field in the capacitive sensing layer. When the touch sensor 101 is touched or very close, a detectable change or modulation occurs in the electric field due to the capacitive coupling between the fingertip and the touch sensing layer. This change or modulation in the electric field produces a signal proportional to the proximity and position of the object to the contact sensor 101. The controller 122 senses a signal reflecting the change in the electric field. The controller 122 parses the touch by one of several methods, and obtains a set of Cartesian coordinates representing the touch position. The position map 140 is a graphical representation of the actual touch position on the touch sensor 101. The coordinates of the touched position are provided to another device, such as the computer 126, to execute commands displayed and touched on the screen. Throughout this specification, claims, and drawings, when an object approaches the touch sensor 101 to cause capacitive coupling to occur, thereby causing electric field modulation, it is considered that a "touch" has occurred. No actual contact needs to occur. The object can be any electrically conductive object, such as a body part (usually a finger) or a non-biological object (usually a stylus).

Figure 2 is an isometric view illustrating a capacitive touch sensor according to one embodiment of the present invention. In this embodiment, the touch screen 200 includes a contact sensor circuit 218, a sensor circuit portion circuit (tail) 220, a first element 212, a second element 216, and an adhesive 214.

The touch screen 220 may include several layers. The first element 212 and the second element 216 represent a protective substrate for the contact sensor circuit 218. These two elements can generally be any non-conductive material, and can be made of chemically strengthened glass plates, tempered glass plates or other transparent materials with similar properties. In applications where optical transparency is not necessary, such as a touch panel application, the first element 212 and the second element 216 need not be optically transparent or glass. Any suitable material can be used, such as plastic or other non-conductive materials. In addition, in some implementations, it is desirable to fabricate the first element 212 and the second element 216 with a flexible material such as a polyester material to realize a deformable or bendable contact sensor.

The adhesive 214 is placed between the first element 212 and the second element 216. The contact sensor circuit 218 is disposed on the second element 216 and communicates with other circuits through the sensor circuit tail circuit 220. The elements form a sandwich structure 210 suitable for use with LCD screens, CRT screens, touch panels, and any other devices whether visible or not. In an alternative embodiment, the contact sensor circuit 218 can be fixed or directly applied to the viewing surface of an LCD screen, a CRT screen, or other similar visual devices, without the second element 216.

In operation, the contact sensor circuit 218 receives the electrical signal from the controller, and then generates an electric field, receives the touch to the first element 212, and generates a signal output by the circuit 220 at the end of the sensor circuit, indicating that the sensor is touched and touched. The capacitive coupling between circuits 218 results in a modulated signal of the electric field.

The advantages brought by the present invention increase the flexibility of the touch screen designer. For example, the increased accuracy of the sensor circuit allows the use of thicker protective elements (such as the first element 212) on the contact sensor circuit 218, while still maintaining the same analytical accuracy. To this end, various embodiments of the present invention may utilize replaceable or removable protection elements that are larger than non-replaceable protection elements. Such an implementation has particular applicability in outdoor public telephone booths and other places, where weather or deliberate sabotage often causes damage to the outer protective element of the touch screen. The present invention provides a replaceable protective element covering the contact sensor at a lower cost and more feasible, without any significant performance degradation.

FIG. 3 is a schematic diagram showing one embodiment of the present invention for an exemplary touch sensor circuit 300 for a touch-sensitive screen. In FIG. 3, the contact sensor circuit 300 includes a plurality of sensor bars 310, a set of "a" terminal leads 340 including independent "a" terminal leads 321a-329a, and one including independent "b" terminal leads 321b-329b. Group "b" terminal lead 345, and viewing surface periphery 360.

More specifically, the touch sensor circuit 300 includes a number of touch-sensitive sensor bars 310 ("strips") spanning from one side of the viewing surface periphery 360 to the other side. In an alternative embodiment, each sensor strip of the plurality of sensor strips 310 is substantially parallel, or in other words is oriented in the length direction or arranged in a single direction. The sensor strip 310 preferably has electrical characteristics that are substantially linear over the length of the sensor strip. They are preferably constructed of indium tin oxide (ITO) for optically transparent applications, but can also be constructed of any suitable conductive material. The number of sensor strips used in any application can be changed according to the design parameters of that particular application. Figure 3 illustrates an embodiment with 9 sensor strips 321-329.

In an alternative embodiment, in addition to being rectangular, the sensor bars of the sensor bar 310 may have various configurations and shapes, and the conductive material is uniformly deposited in the periphery. For example, each sensor strip may include a conductive perimeter and a non-conductive area located within the conductive perimeter. The sensor bar may be any shape capable of establishing an input signal representing a touch position in response to a touch.

According to the present invention, each sensor strip 310 is connected to its own unique pair of conductive leads. The leads can be wires, traces, or other circuits or systems suitable for connecting the sensor strip to the controller (122, Figure 1). For example, the sensor strip 324 is connected to the lead 324a at its first end and to the lead 324b at its second end. The leads 324a and 324b are then connected to a controller, such as the controller 122 of FIG. 1. In one embodiment, the "a" terminal leads 321a-329a and the "b" terminal leads 321b-321b may be concentrated in the sensor circuit tail circuit 220, which has a conductive connector connected to the controller. Although shown concentrated in the sensor circuit tail circuit 220 in FIG. 2, any means is sufficient to connect the wiring to the controller (not shown). Generally speaking, the circuit can be made of virtually any conductive material, such as copper, silver, gold and so on. If the circuit is printed on the film, it is desirable that the film does not react with the conductive material.

For ease of description, the leads connected to each end of any particular sensor strip have the same label. The "a terminal lead 340 is located at one end of the contact sensor circuit 300, and the "b terminal lead 345 is located at the other end of FIG. 3. Each sensor bar 321-329 is connected to the controller through its own unique pair of leads. For example, the two ends of the sensor bar 324 are connected to the controller through leads 324a and 324b. No other sensor strip is connected to the lead 324a or 324b. This feature of the present invention allows each sensor bar to be uniquely addressed, and the signal appearing on a pair of leads can be immediately resolved to the specific sensor bar that has experienced a touch. FIG. 3 illustrates that the sensor bars 310 and their only leads are arranged symmetrically, and the "a" end leads and "b" end leads of each pair of leads are connected to each of the opposite ends of the same sensor bar. For this description, the sensor strips that are adjacent to each other are defined as "neighbors." The spacing and size of the sensor bars 310 are selected so that a touch on any sensor bar produces reasonable signals on the closest first and second neighbors of that sensor bar.

In operation, the leads 340 and 345 receive the excitation waveform from the controller and provide it to the sensor bar 310, which then generates an electric field. The contact sensor circuit 300 receives a touch on one or more sensor bars 310, and in response, generates a signal on one or more pairs of unique leads 340 and 345. The signal represents the change in the electric field due to the capacitive coupling between the touch and one or more sensor bars 310.

Since each sensor strip and its leads are not connected to any other sensor strips or leads, a touch on a touch-sensitive screen in the area of a certain sensor strip, such as the touch 346 close to the sensor strip 328, will be connected to the sensor. Signals are generated on a pair of leads of the strip (such as leads 328a and 328b), regardless of any other sensor strips or leads. In addition, touch 346 may be coupled to adjacent sensor bars (327 and 329). In this case, the touch will generate a unique signal on each line (327a-b, 329a-b) connected to it, and each signal is completely independent of any other sensor strips or leads. A touch to the screen using the contact sensor circuit 300 should produce a peak signal on the touched sensor bar, and a smaller or reduced signal on the neighboring neighbors of the touched sensor bar. Thus, any touch to the screen should result in a pattern of unique independent signals on several lines connected to the sensor strips adjacent to the touch.

As will be apparent later, since the symmetrical architecture provides a unique pair of leads for each sensor bar, the present invention also provides the ability to accurately resolve the location of the touch that occurs on the X axis. The present invention provides high accuracy in the X and Y directions. The present invention also provides the ability to identify the touched sensor bar and the adjacent sensor bar in the area where the touch occurs by analyzing the signal, and analyze the position of the touch occurring on the Y axis. A further advantage of the present invention is that the leads can be formed in a single step because there are no crossovers or multiple connections. Figure 3 provides an example of a sensor circuit built in accordance with the teachings of the present invention.

4A and 4B are schematic diagrams of a part of a touch sensor according to an alternative embodiment of the present invention. FIG. 4a is a schematic diagram of an embodiment of a touch screen system 400. As shown in FIG. This embodiment is implemented in a handheld device 420 having a surface 405, buttons 407, side areas 430 and 435, and a touch screen. The touch screen consists of a touch sensor 401 with a capacitive touch sensor strip 410 (detailed in FIG. 4B) with a touch sensor circuit 450. The touch sensor 401 is configured to operate in a substantially similar manner to the touch screen system 100 illustrated in FIG. 1.

The handheld device 420 may have the properties of a personal digital assistant (PDA) and other devices, in which the side areas 430 and 435 between the touch sensor 401 and the periphery of the device are small due to design limitations. It should be understood that, for ease of description, the size of the side regions 430 and 435 is exaggerated in the figure, and it may be expressed that the side regions 430 and 435 are relatively small relative to the size of the handheld device 420. In the embodiment illustrated in FIG. 4a, the touch sensor circuit is oriented with a vertical touch sensor strip 410, that is, the sensor strips approximately parallel to the side areas 430 and 435.

FIG. 4B illustrates other details about the touch sensor 401 illustrated in FIG. 4A. The touch sensor 450 includes a plurality of sensor bars 410, "a" terminal leads 421a-426a, "b" terminal leads 421b-426b, sensor bars 421-426, a viewing surface periphery 460 (shown in a dashed frame), a first group Leads 470 and the second set of leads 480.

More specifically, the touch sensor circuit 450 includes a plurality of sensor bars 421-426 spanning the touch sensor 401 illustrated by the periphery 460. The sensor bars 410 may be substantially parallel. In an alternative embodiment, the sensor strip 410 may be oriented in a length direction or arranged in a single direction, rather than being substantially parallel. The configuration of the contact sensor circuit 450 is basically similar to the contact sensor circuit 300 of FIG. 3, except that the leads 421 b-426 b are combined into a first set of leads 470 and a second set of leads 480. The first set of leads 470 and the second set of leads 480 are routed such that (i) they are substantially parallel to the sensor bar 410; (ii) they are located at opposite ends (first end and second end) of the screen periphery 460; and ( iii) The total number of leads of the first set of leads 470 and the second set of leads 480 is approximately equal to the number of sensors 410.

In one embodiment, the number of leads of the first group of leads 470 is substantially the same as the number of leads of the second group of leads 480. By orienting the sensor bars 421-426 perpendicular to the direction of the handheld device 420, and by routing the leads from one end of the sensor bar 410 along both ends of the contact sensor 401, the necessary side areas 430 and 435 are reduced. Therefore, the handheld device 420 can be made smaller without reducing the size of the contact sensor 401, or the contact sensor 401 can be slightly enlarged without affecting the size of the handheld device 420. In other words, this lead configuration reduces the side areas 430 and 435, and allows the touch sensor 401 to occupy more of the width of the handheld device 420.

The configurations illustrated in Figures 4B and 4C have particular applicability in entertainment activities where it is desired to detect more than a single touch. For example, a gaming device can be constructed using the embodiment of the touch sensor circuit 450 illustrated in FIG. 4B. The gaming device can provide separate user input areas on different parts of the touch screen. For example, the gaming device can use separate side-by-side gaming areas to support two-player games. In this case, since the touch will generate a signal on the sensor bar with a unique lead, two separate simultaneous touches (touches in each game area) can be easily detected, so that there is no ambiguity.

As an alternative, the configuration illustrated in Figure 4C can be used in applications similar to those described above. In this example, a touch sensor 490 with two input areas (493, 494) is provided. In this embodiment, each input area (493, 494) includes six discretely addressed sensor bars, each sensor bar being connected to a unique pair of leads. The sensor bar of the left input area 495 is connected to the first set of lead pairs 497 in the manner described above. Similarly, the sensor bar of the right input area 494 is connected to the second set of lead pairs 498. The leads of each input area can be connected to the same controller or separate controllers. Each input area (493, 494) may even be a separately assembled contact sensor unit, installed side by side to form a single contact sensor 492 in appearance. In this configuration, two independent touches (such as touch 495 and touch 496) can occur simultaneously, but can still be distinguished from each other. This configuration makes the touch sensor 490 of FIG. 4C particularly suitable for applications where multiple touches to the touch sensor 490 may occur simultaneously, such as a multi-user game environment. These are just some of the many specific implementations that can be implemented by the present invention.

Figure 5 illustrates an aspect of the present invention, in which the controller working with the present invention can resolve the X-axis coordinates from the signal generated by the touch. The configuration and operation of the touch sensor 500 are basically similar to the touch sensor 300 illustrated in FIG. 3. FIG. 5 is a schematic diagram illustrating that the touch T1 occurs on or near a sensor, and the other two touches T2 and T3 occur near the periphery of the sensor circuit.

In order to understand the coordinate analysis method provided by the present invention, it is important to realize that due to the difference in the distance from the touch, a touch produces a peak signal on a given sensor bar, while a weaker signal is produced in its vicinity. Since the strength of the signals decreases as a function of the distance from the touch, when drawn in the same order as the sensor bars, the graphical representation of these signals has a certain shape. In FIG. 5, touches T1-T3 represent the touches of the touch sensor 500 by a part of the human body, a stylus or other suitable devices. The touch T1 is roughly located between the sensor bars 323 and 324. The touch T2 is generally located on the sensor bar 329 on the periphery of the sensor circuit 500. The touch T3 is generally located between the sensor bars 321 and 322 near the periphery of the sensor circuit 500.

The X coordinate is determined by the ratio of the left signal and the right signal. The symmetrical nature of the touch sensor architecture provides advantages when resolving the X coordinate. At the physical midpoint (half the distance from one end of the sensor bar to the other end), the impedance of the "a" end of the sensor bar and its lead is approximately equal to the impedance of the "b" end of the sensor bar and its lead. Therefore, the X coordinate position of the touch can be determined by estimating the relative signal strength of the signal on the lead at one end of the sensor with respect to the signal on the lead at the other end.

Any acceptable algorithm may be executed to determine the X coordinate, for example, by specifying the X coordinate based on a comparison of the relative strengths of signals appearing on the lines connected to the two ends of the sensor strip receiving the touch. For example, the X coordinate of touch T1 can be determined by implementing the following formula in the software in the controller:Among them, the first end signal is equivalent to the value related to the signal from the sensor 324 sensed on the line 324a, and the second end signal is equivalent to the value related to the signal from the sensor 324a sensed on the line 324b. The X span refers to the distance in the X direction from one end of the touch screen to the other end. Alternatively, the first terminal signal and the second terminal signal may be values generated from the sum of the strongest signals of a predetermined number of sensor bars 310. Optionally, the first end signal and the second end signal may be any other value equal to or derived from one or more of the strongest signals. It will be understood that the above formula actually calculates the weighting factor as the first end signal to the total signal, and applies the weighting factor to the total distance across the touch screen to calculate the X coordinate. Other techniques known in the art can be used to calculate the X coordinate.

Determine the Y coordinate in different ways. 6a-6c are schematic diagrams showing the signal amplitude plots of the touch illustrated in FIG. 5 for four adjacent sensor bars. Figure 6 illustrates an aspect of the present invention, in which the controller working together with the touch sensor recognizes the sensor strips subject to touch and analyzes the strongest signal on one or more lines (up to a predetermined number of lines) , To resolve the Y coordinate. The controller identifies the group of lines with the strongest signal. The relevant signals on the lines in the set of lines enable the controller to determine which sensor strip was initially touched.

Referring to Figure 6a, since the outermost neighbor is weak and the touched sensor bar is strong, the graphical representation of signal strength or amplitude looks like a "bump" pattern. First, the Y coordinate is roughly determined by identifying the sensor bar carrying the peak signal, and the Y coordinate is fine-tuned by interpolating between the peak signal and other signals. More specifically, as shown in FIG. 6a, as illustrated in FIG. 5, the touch T1 occurs closest to the sensor bar 324. This contact also produces a weaker signal on the two adjacent sensor bars 322 and 323. Finally, the other sensor bar 325 also feels a weaker signal. It will be understood that the signal pattern generated by the touch T1 may deviate slightly from that shown in FIG. 6a, but in general it should have a "bumped" appearance pattern, and the signal amplitude decreases from the sensor bar with the strongest signal. For example, the sensor strip connected to line 324 may have the strongest signal, followed by 323, then 322, and then 325. Many other combinations will also become obvious. Similarly, it is possible that two sensor bars have the same signal amplitude, for example a touch occurs exactly between the two sensor bars.

Similarly, on the sensor strips on the periphery of the sensor circuit 500 (the uppermost and lowermost sensor strips shown in Figure 5), the signal may be at the sensor strips on the edge of the screen (the sensor strips 321 or 321 shown in Figure 5). 329) is the strongest and decreases as a function of the distance from the sensor strip undergoing the touch. For example, the signal amplitude presented on each sensor strip in a group may give a rising signal pattern (Figure 6b) or a falling signal pattern (Figure 6c), depending on whether the contact (respectively) occurs at the top or bottom of the screen . For example, touching T2 may result in the signal pattern illustrated in FIG. 6b, and touching T3 may result in the signal pattern illustrated in FIG. 6c.

The following examples, instructions, and guidelines provide a description of the method of using the sensor circuit according to the present invention to resolve the touch position. It should be noted that the examples, descriptions, and guidelines described here are merely illustrative, and there may be deviations in certain metrics without departing from the spirit and scope of the present invention.

The 7-inch touch screen was successfully manufactured by using the present invention. It provides higher X coordinate accuracy than existing contact sensor designs. The present invention is particularly suitable for medium to small touch screens, such as those less than about 9 inches, but it can be used in any application where high-precision resolution is desired. It will be understood that the present invention uses an increased number of leads compared to existing touch sensor designs, especially near-field imaging designs. However, the increased area required to route additional leads is a design consideration, which can be improved by certain techniques that have been described before, or can be simply seen as a compromise for increased accuracy.

The above description, examples and data provide a complete description of the manufacture and use of the composition of the invention. Since many embodiments of the present invention can be made without departing from the spirit and scope of the present invention, the essence of the present invention lies in the appended claims.