CN101587254B - Touch sensing liquid crystal display - Google Patents

Abstract

Systems, methods, and techniques for integrating touch sensing functionality into a liquid crystal display are described. In a particular implementation, light-sensitive detectors are positioned on a backlight panel to detect changes in light incident on the backlight panel in response to a physical touch on the surface of the LCD display screen. Then, based on the signals received from the light sensing detectors, a location of the physical touch can be estimated. And a lookup table storing comparison results of signal strengths detected by the detector for each touch position in the prediction process, each set of comparison results corresponding to an ID of a corresponding touch position, the ID of the touch position stored in the lookup table being looked up at least partially according to the comparison results of signal strengths detected by the current touch sensitive light detector, and the touch position being identified.

Description

Touch Sensitive LCD Display

technical field

The invention relates to a liquid crystal display with touch sensing function.

Background technique

Liquid crystal displays (LCDs) have been widely implemented in many display applications such as computer monitors, personal digital assistants (PDAs), public kiosks, cell phone displays, and the like. Touch-sensitive displays allow users to select specific areas on the screen using various input devices by simply touching that area of the display or bringing an object such as a finger, stylus, or pen into or near that area. OK.

One approach to integrating touch-sensing functionality into an LCD display involves integrating an array of photosensors into the thin-film field-effect transistor (TFT) backplane of the LCD display. The light sensor array can sense one or more objects, such as a finger, on the display screen by detecting the shadow of the object blocking the background light or the reflected light of the object. Such photosensor arrays may have different structures and contain different materials than the LCD TFT backplane. Integrating these sensor arrays into a TFT backplane, then, typically adds fabrication process steps. This increases the manufacturing cost and complexity of the display, and also reduces the yield of the display. In addition, this photosensor array will reduce the aperture ratio of pixels in the LCD display, affecting the performance of the display. To date, this approach has been limited to small-sized LCD displays due to manufacturing difficulties.

Therefore, it is desirable to have an LCD display with touch sensing function, which does not significantly increase the cost and does not affect the performance of the display.

Contents of the invention

In order to solve the problems of the technologies described above, the present invention proposes the following technical solutions:

A touch-sensitive display including:

An LCD display with a light guide on one side and an LCD backlight on the other;

The LCD backlight panel includes at least one visible light source and at least one touch-sensitive photodetector, the at least one visible light source is configured to emit visible light through the LCD display screen, the at least one touch-sensitive photodetector is disposed on the above the backlight to detect the touch-sensing light,

wherein in response to a touch on the surface of the light guide plate, the at least one touch-sensitive light detector is configured to detect a change in touch-sensitive light incident on the backlight plate,

a lookup table storing the comparison results of the signal strength detected by the detector for each touch position during the prediction process, each set of comparison results corresponds to an ID of a corresponding touch position,

The touch location is identified by looking up the ID of the touch location stored in the lookup table based at least in part on the comparison of signal strengths detected by the current touch-sensitive photodetector.

A method of operating a touch-sensitive LCD, comprising:

Visible light from at least one visible light source disposed on a backlight passes through the LCD display;

receiving one or more signals from at least one touch-sensitive photodetector disposed on said backlight in response to a touch on said LCD display surface; and

processing said received signals to calculate the location of said touch on said surface of said LCD display, wherein a look-up table stores signals detected by detectors for each touch location during prediction Intensity comparison results, each set of comparison results corresponding to a corresponding touch position ID, at least in part based on the comparison results of the signal strength detected by the current touch-sensitive photodetector, look up the ID of the touch position stored in the lookup table, and identify the touch Location.

Description of drawings

Non-limiting and non-exclusive features of the invention will be described with reference to the following drawings, wherein like reference numerals designate like parts throughout the various drawings, in which:

FIG. 1 is a schematic cross-sectional view of a touch-sensitive LCD according to one embodiment;

Figure 2 is a schematic diagram of a touch-sensitive LCD of one embodiment;

3 is a schematic cross-sectional view of a touch-sensitive LCD including a pressure transfer film of one embodiment;

Fig. 4 is a schematic cross-sectional view of an LCD display screen of an embodiment;

5A and 5B are plan views of an alternative embodiment of a backlight unit with touch-sensitive photodetectors and visible light sources mounted thereon;

FIG. 6 is a flowchart illustrating processing signals from touch-sensitive photodetectors to estimate the location of a physical touch on the surface of an LCD display, according to one embodiment;

FIG. 7 depicts a particular technique for obtaining estimates of physical touch on an LCD display using a lookup table, according to one embodiment; and

FIG. 8 is a flowchart describing aspects of providing an estimate of the location of a touch on an LCD display surface, according to one embodiment.

Detailed ways

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In addition, in order to describe the present invention clearly, methods, devices or systems known to those skilled in the art will not be described in detail.

Throughout the specification, "one embodiment" means that a particular feature, result or characteristic described in connection with a particular embodiment may be included in at least one embodiment of the invention. Thus, the appearances of "in one embodiment" in various places in the specification are not necessarily referring to the same embodiment or any one particular embodiment described. Furthermore, it is to be understood that the particular features, structures or characteristics described may be combined in various ways in one or more embodiments. In general, these or other issues may of course vary with the particular context of use. Therefore, a description of a specific context or use of these terms can help to understand the context.

According to particular embodiments, in order to provide an LCD display with touch-sensing functionality without significantly increasing the cost and complexity, the backlight unit of an LCD display may include fixed photodetectors or sensors capable of detecting touch-induced incident respond to changes in light. The signals received from the photodetectors can be processed to calculate the location of the touch on the surface of the LCD display. By placing the photodetectors on the backlight unit, the complexity and cost associated with integrating the photosensor array into the TFTs of the LCD display backplane can be avoided.

1 is a cross-sectional view of an embodiment of a touch-sensitive LCD 100, comprising: an optical light guide plate 101 with at least one touch-sensitive light source 104 disposed at its edge; an LCD display 102 and a backlight unit 103.

The optical light guide plate 101 can be a uniform transparent plate, such as an acrylic plate or a plexiglass plate, and its refractive index is greater than 1.0. The thickness of the optical light guide plate 101 may be in the range of 4.0mm to 20.0mm. However, it should be understood that different thicknesses and materials may be used. The touch-sensitive light source 104 can emit non-visible light, such as near-infrared light with a wavelength range of 750nm to 1000nm, through the edge surface of the light guide plate 101 and into the optical light guide plate 101 . However, it should be understood that different wavelengths of light may be used. It is well known that when light passes from a medium with a higher refractive index n ₁ to another medium with a lower refractive index n ₂ , if the incident angle on the boundary is greater than a critical angle θ _c , total internal reflection will occur. The critical angle θ _c can be calculated by using the formula n ₁ *sin(θ _c )=n ₂ of Snell's law. For example, in this example, if the light guide plate 101 is an acrylic plate with a refractive index of about n ₁ =1.5, and the other material is air with a refractive index of about n ₂ =1.0, then the critical angle can be determined to be about 41.8 °. Therefore, on the boundary between the light guide plate 101 and the air, if the light incident angle is greater than 41.8°, the light can be completely reflected and confined in the light guide plate 101, and reflected and propagated between the upper surface and the lower surface. Light confined within the light guide plate 101 is regarded as touch-sensitive light 110 . Once an object, such as a finger, touches the surface of the optical light guide plate 101, the internal reflection is interrupted because the light is no longer confined within the optical light guide plate 101, but spills out of the light guide plate 101 in response to the touch. These overflow lights are indicated as 109 in FIG. 1 .

In order to make a more uniform response to touching objects of different materials and sizes, a pressure transfer film can be placed above the optical light guide plate 101 . As shown in FIG. 3 , the pressure transfer film 330 is placed close to the light guide plate 101 . There is a small air gap between the pressure transmission film 330 and the light guide plate 101 so that internal reflection can be maintained when the surface of the pressure transmission film 330 is not touched. In one particular implementation, the pressure transmission membrane 330 can be transparent and flexible. In response to the pressure applied by the touching object, the touched local portion of the pressure transmission film 330 is dented to contact the light guide plate 101 , thereby interrupting internal reflection in the light guide plate 101 to allow light to overflow, as described above. Here, the pressure transfer film 330 is deformed due to the touch, thereby contacting the surface of the light guide plate 101 , and causing interruption of total internal reflection of light within the light guide plate 101 . As a result, part of the light 109 overflows the light guide plate from the contact position. In particular, the thickness of the pressure transfer film 330 may be in the range of 0.2 mm to 5.0 mm.

According to one embodiment, the touch-sensitive light source 104 may be an infrared light-emitting diode (LED) with a peak emission wavelength greater than 850 nm but less than 1000 nm. High power emitting LEDs in this wavelength range do not interfere with the image displayed on the LCD display 102 . The touch-sensitive light source 104 may be fixed to a printed circuit board (PCB, not shown in the figure) by soldering, and is positioned on the edge of the light guide plate 101 as shown. The touch-sensitive light source driving circuit 204 can control the light intensity of the light source 104 according to the signals and/or instructions from the touch-sensitive LCD control unit 220 . In order to effectively couple the emitted light into the light guide plate 101, if the light guide plate 101 is an acrylic plate or a plexiglass plate, the touch-sensitive light source 104 may have a half-intensity angle less than 40°. In this context, the half-intensity angle is the angle at which the intensity of light from a light source is reduced to half of its maximum luminous intensity. Here, the touch-sensitive light source 104 can be arranged at a certain angle relative to the edge of the light guide plate 101 .

In a particular implementation, LCD display 102 may comprise a multilayer structure as shown in FIG. 4 . Two glass substrates 403 and 404 have polarizers 401 and 402 adhered to one side, respectively. Red 405 , green 406 and blue 407 color filter layers are fabricated on the glass substrate 403 . Each filter layer allows the corresponding visible light to pass through. For example, red filter layer 406 only allows visible light at red wavelengths to pass through. On these filter films, a transparent conductive layer 408 is disposed as a common electrode of the LC (for example, multiple pixels share a common electrode on a pixel array). The pixel electrodes 409 are insulated from each other. The pixel electrode 409 can be driven and/or applied with a voltage by the pixel TFT 410 alone. The liquid crystal layer 411 is sandwiched between the common electrode 408 and the pixel electrode 409 . In the liquid crystal layer 411, according to the voltage applied on the pixel electrode 409, the liquid crystal molecules can be aligned to control the transmission of light through the associated pixel. For example, according to the command signal from the touch-sensitive LCD control unit 220, the LCD pixel driving circuit 202 can apply an appropriate voltage to the pixel electrode 409 through the pixel TFT 410.

Although the light transmission through a pixel can be varied by adjusting the voltage applied to an associated pixel electrode 409, this adjustable light transmission through an LCD pixel is not suitable for infrared light with wavelengths greater than 850 nm because polarizers cannot polarize electromagnetic waves greater than 850 nm . In addition, the filter film has no effect on infrared light (ie, infrared light can pass through the color filter film). It has been verified by tests that when a dark image is displayed, about 70% of infrared light (maximum luminous wavelength 880nm) can pass through the LCD display. Therefore, the overflowing light 109 can pass through the LCD display screen 102 to the backlight unit 103 .

The backlight unit 103 includes a backlight light source 105 that emits visible light to illuminate images on the LCD display 102 so that a user can see the images displayed on the LCD display 102 . Backlight light sources 105 may be red, green and blue LEDs, white LEDs or fluorescent lights, just to name a few examples. The backlight unit 103 may comprise a backlight panel with one or more light sources on it. For example, such a backlight board may include a visible light source (not shown) soldered to the PCB, and the luminous intensity is controlled by the backlight source driving circuit 205 according to signals and/or instructions from the touch-sensitive LCD control unit 220 .

The backlight unit 103 also includes a light detector 106 for detecting light overflowing from the light guide plate 101 . Detector 106 includes a photodiode, a phototransistor, a CCD, or a CMOS image sensor, to name a few examples. The detector 106 may also be covered with a filter that matches the output of the touch-sensitive light source 104 . The detector 106 may be soldered to a PCB (not shown in the figure) of the backlight unit 103 , which may be the same PCB connected to the visible light source 105 .

5A and 5B are plan views of a white LED light source 105 and photodetector 106 configuration, in accordance with a particular embodiment. The detectors 106 are uniformly distributed among the backlight light sources 105 in a grid pattern. The spacing between any two detectors 106 can be selected based on factors such as cost and touch resolution or accuracy. Smaller pitches mean more detectors are needed, resulting in higher costs. If the separation between two detectors is large, some detector signals may not be strong enough to accurately estimate the touch location. In one example, the distance between the two detectors is set to be close to the distance between the LCD display and the backlight (eg about 40mm). For a touch-sensitive LCD with a diagonal size of 32 inches, 144 detectors can be used, which is far less than the number of detectors usually integrated in an LCD display, which is usually compared with the number of LCD display pixels. The number is the same. Fewer detectors also allow the use of fewer signal processing resources. As shown in FIG. 2 , an inductive light signal detection circuit 206 may be used to receive and process the signal from the light detector 106 .

The output signal of the light detector 106 may be in the form of an analog signal, which is converted into a digital signal by an analog-to-digital conversion (ADC) device (not shown in the figure), and the analog-to-digital conversion device is integrated in the sensing signal detection circuit 206 . These digital signals are then analyzed by a digital signal processing circuit (not shown in the figure) to determine the coordinates of a touch object, and the digital signal processing circuit is also integrated in the signal detection circuit 206 . However, other combinations of programmed processors, software and/or hardware may be used to process digital signals. The flowchart shown in FIG. 6 describes how digital signals are processed to calculate the location of a physical touch in accordance with a particular embodiment.

Because the spectrum of the ambient light overlaps at least partially with the spectrum of the touch light, and because the ambient light varies with different environments and operating conditions, the ambient light can add background noise and cause detection failures. In order to reduce this noise effect caused by ambient light, the detection process can be divided into two cycles. Here, the touch-sensitive light source 104 may be turned on during a first period and turned off during a second period. First, the digital signal processing circuit of the signal induction detection circuit 206 detects the received signals during the first time interval of the detection cycle (block 601), and then stores the values related to these signals in a memory, which can be obtained from the signal Handles circuit digital access. Next, at block 602, the signal processing circuit detects the received signal during a second time interval of the detection cycle. Next, the module 603 subtracts the signal value detected in the second period from the signal value detected in the first period to obtain a signal value used for calculating the touch position. Using the process described above, background noise from ambient light can be reduced or reduced.

The signal obtained from the subtraction at block 603 can be processed to estimate a physical touch location on the LCD display 102 . Calibration values for the photosensitive detectors 106 may be based on white noise levels and non-uniform sensitivities of individual detectors 106 previously stored in a memory of the digital signal processing circuit. These calibration values can be obtained by measuring the signal values of the detector 106 in a completely dark environment and in an environment illuminated by uniform light. At block 604, the values obtained from the subtraction may be compared to their corresponding calibration values to correct for non-uniform response characteristics of the detector 106, such as sensitivity and white noise. In block 605, the value obtained in block 604 may also be compared with a threshold previously stored in the digital signal processing circuit, and a signal whose value is greater than the threshold is extracted.

According to one embodiment, the strength of the signal received on the light-sensing detector 106 in response to a touch on the surface of the LCD display 102 varies with the distance between the light-sensing detector 106 and the location of the touch on the surface of the LCD display 102. varies with the distance function. Thus, touch-sensitive photodetectors 106 that are laterally closer to the touching object 107 are more likely to receive a stronger optical signal (i.e. Light 109 escaping from the optical light guide plate 101). Therefore, in response to a touch on the surface of LCD display 102, touch-sensitive light detector 106 is used to detect changes in touch-sensitive light (eg, from overflow light 109) incident on the backlight panel. However, it should be understood that this is only one change in touch-sensing light that may be detected in accordance with a particular embodiment, and that other types of changes in such incident touch-sensing light may be detected without departing from the invention. If the photosensitive detectors 106 are configured as shown in FIG. 5 , the location or point of touch is within the area defined by the four detectors 106 . Here, the signals received by these four detectors 106 are greater than the signals received by the other detectors 106 .

Unlike photodetectors integrated in LCD displays, where the distance between two adjacent detectors may be only a few hundred micrometers, a touch can be accurately located by the maximum signal value in an area. As mentioned before, in the example where the detector 106 is integrated into the backlight unit 103, in order to use fewer detectors (for example, based on cost considerations), the distance between the two detectors may be about 10 mm or more . In a specific implementation, in order to accurately estimate a touch position on the LCD display screen 102, the signal intensity received by four detectors (such as surrounding an area containing the touch position) and the distribution of light intensity on the backlight panel can be combined Condition. For example, this light intensity distribution may characterize a lateral distance between the location of the touch and the location of the detector 106 where the signal is suspected to be obtained. In an optional implementation, a lookup table may be used to locate the touch location within the area bounded by the detector 106 based at least in part on the signal strength values obtained from the detector 106 .

As an example, a lookup table can be set up by the method described below. The detector array on the backlight panel can be divided into multiple blocks, each block includes four detectors and an area bounded by these four detectors (106.1, 106.2, 106.3 and 106.4), as shown in Figure 7, the bounded area It is evenly divided into a plurality of sub-regions 701 . Each sub-region 701 represents a candidate touch location or point. The data stored in the lookup table to identify a touch location 707 may be obtained by experimental measurements and then calculated using the measurement results. For example, directly above location 707 , touching the touchable surface, four detectors around location 707 receive signal strengths labeled S ₁ , S ₂ , S ₃ , and S ₄ , respectively. The data used to identify touch location 707 is a comparison of these four signal values. The comparison result may be (a, b, c), where a=S ₂ /S ₁ , b=S ₃ /S ₁ and c=S ₄ /S ₁ . The same process can be used for other touch positions to obtain a corresponding data for position recognition. Each touch location is then assigned an identification (ID) data.

By comparing the obtained signals at step 606 and mapping the result of the comparison to the ID of the touch location stored in the lookup table, the touch location can be identified (step 607). Then, at block 608 , an identified touch location is sent to the touch-sensitive LCD control unit 220 . According to the determined touch location, the control unit 220 may provide a response signal and/or instruction to update the image displayed on the LCD display.

The flowchart of FIG. 8 describes the implementation process of the touch-sensitive LCD 100. As previously mentioned, at block 801, a touch sensitive LCD 100 is provided which includes an LCD display 102 with a light guide plate 101 on one side and a backlight unit 103 on the other side. Next, the touch-sensitive light source 104 is placed on one edge of the light guide plate 101, and the backlight light source and touch-sensitive light detector are placed in the backlight unit (blocks 802A and 802B). Here, blocks 801, 802A, and 802B describe the process of making a touch-sensitive display according to one particular implementation. During execution, the control unit 220 may output an image signal to the LCD pixel driving circuit 202 to change the light transmittance of the LCD pixel according to the image signal (block 803B). At the same time, the control unit 220 can send a signal and/or instruct the backlight driving circuit 205 to turn on the visible light source 105, so that the image displayed on the LCD screen is illuminated and can be seen by the user (block 803C). The control unit 220 may first instruct the touch-sensing light source driving circuit 204 to turn on the touch-sensing light source 104, so as to guide the touch-sensing light 110 into the light guide plate 101 (block 803A). In response to the touch object 107 contacting the surface of the light guide plate 101, some touch-sensitive light escapes from the light guide plate 101 by reflection or refraction (block 804). The spilled light 109 passes through the LCD display 102 and is detected by the detector 106 located on the backlight unit 103 (block 805). The sensing signal detection circuit 206 collects the detection result of the touch-sensitive light on the light-sensing detector 106, and sends coordinate information representing the estimated position of the touch to the control unit 220 (block 806). Next, in response to the touch request, the control unit updates the image displayed on the LCD (block 807).

The methods described herein can be implemented in various ways, depending on the application in accordance with particular features and/or examples. For example, such methods may be implemented in hardware, firmware, software, and/or a combination thereof. For example, in a hardware implementation, the processing unit may be one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable Gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, electronic devices, other device units that can perform the functions described herein, and/or combinations thereof.

In this disclosure, "a", "one or more", "at least one" are considered equivalent. For example, if the disclosure describes one, it will be read that similar teachings or concepts apply to more than one.

While exemplary embodiments of the present invention have been described in detail, it will be understood by those skilled in the art that various modifications and equivalents may be made without departing from the invention. In addition, many modifications may be made without departing from the teachings of the present invention without departing from the central concept described herein. Therefore, the invention is not intended to be limited to the particular embodiments described herein, but the invention may include all embodiments falling within the scope of the appended claims and their equivalents.

Claims (18)

1. touch sensitive dis-play comprises:

A LCD display, one side have a light guide plate, and opposite side has a LCD backlight;

Described LCD backlight, comprise at least one visible light source and at least one touch sensible photo-detector, this at least one visible light source is configured to and sends visible light and pass described LCD display, this at least one touch sensible photo-detector is positioned on the described backlight with the detecting touch induction light

Wherein be the lip-deep touch of the described light guide plate of response, described at least one touch sensible photo-detector is used to survey the variation of the touch sensible light that incides on the described backlight,

A lookup table is stored in the forecasting process comparative result of the signal intensity that is detected by detector at each touch location, the ID of every group of corresponding corresponding touch location of comparative result,

The comparative result of the signal intensity of being surveyed according to current touch sensible photo-detector is searched the ID that is stored in touch location in the lookup table at least in part, identifies touch location.

2. light guide plate according to claim 1, it comprises that at least one touch sensible radiant is positioned on its at least one side.

3. touch sensitive dis-play according to claim 1 also comprises a controller, and it is used to calculate the position of described touch.

4. touch sensitive dis-play according to claim 1, wherein said backlight comprise a substrate, and at least one visible light source is installed on it, and wherein said at least one touch sensible photo-detector is fixedly attached to described substrate.

5. touch sensitive dis-play according to claim 4, wherein said at least one touch sensible photo-detector is fixedly attached to described substrate by welding.

6. touch sensitive dis-play according to claim 1, also comprise a pressure transport membranes that is positioned in described LCD display surface, for the physics of response on described pressure transport membranes touches, wherein said at least one touch sensible photo-detector is used to survey the variation of the touch-sensing light that incides on the described backlight.

7. the operation method of a touch sensible LCD comprises:

The visible light that sends from least one visible light source that is placed on the backlight passes LCD display;

For responding, receive one or more signals from least one the touch sensible photo-detector that is placed on the described backlight in the lip-deep touch of described LCD display; With

Handle the described signal that receives and calculate position in the described lip-deep described touch of described LCD display, wherein, lookup table has been stored in forecasting process the comparative result of the signal intensity that is detected by detector at each touch location, the ID of every group of corresponding corresponding touch location of comparative result, the comparative result of the signal intensity of being surveyed according to current touch sensible photo-detector at least in part, search the ID that is stored in touch location in the lookup table, identify touch location.

8. method according to claim 7, the described signal that receives of wherein said processing also comprises: be based, at least in part, on the signal value that obtains from described at least one touch sensible photo-detector under the dark condition, the numerical value of calibration and the described signal correction that receives.

9. method according to claim 7, also comprise: pass light guide plate from touch sensible light to the small part that at least one touch sensible radiant on described light guide plate sends, the variation of the touch sensible light on described at least one touch sensible photo-detector is incided in the wherein said signal representative that receives.

10. method according to claim 9, the described variation of wherein inciding the described touch sensible light on described at least one touch sensible photo-detector are that the corresponding at least a portion touch sensible light that is caused by described touch overflows from described light guide plate.

11. method according to claim 7, the described signal that receives of wherein said processing also comprises:

From the described signal of a part that comprises ambient light noise, pick out the described signal that receives of at least a portion and the corresponding variation of inciding the touch sensible light on described at least one touch sensible photo-detector.

12. method according to claim 11, wherein said touch sensible light comprises non-visible light.

13. method according to claim 11, wherein from the described signal of a part that comprises ambient light noise, pick out the described signal that receives of at least a portion and the corresponding variation of inciding on described at least one touch sensible photo-detector of touching quick light, also comprise:

In the very first time interval of a detect cycle, also during the touch sensible radiant is unlocked, from described at least one touch sensible photo-detector received signal;

In second time interval of a detect cycle, also be during the touch sensible radiant is pent, from described at least one touch sensible photo-detector received signal; With

From the described signal of at least a portion that receives at interval in the described very first time, deduct the described signal of at least a portion that receives in described second time interval.

14. method according to claim 7, the described signal that receives of wherein said processing estimates that described position also comprises:

At least in part according to the signal value that receives from least two touch sensible photo-detectors,, and determine the position of described estimation at least in part according to one or more numerical value of in lookup table, selecting.

15. method according to claim 13 also comprises from a plurality of touch sensible photo-detector received signals, the described signal that receives of wherein said processing and calculate described touch location and also comprise:

At least in part according to the signal value that receives from described a plurality of touch sensible photo-detectors, according to one or more numerical value of in lookup table, selecting, in the zone that is surrounded by described a plurality of touch sensible photo-detectors, determine the position of described touch at least in part.

16. method according to claim 14 is wherein calculated according to the signal of measuring touch sensible photo-detector gained at least in part, obtains to be stored in the described numerical value in the described lookup table.

17. method according to claim 15 also comprises:

The signal value that receives from described touch sensible photo-detector relatively; With

Selection provides a plurality of touch sensible photo-detectors of highest signal value, determines the zone that is surrounded by described a plurality of touch sensible photo-detectors.

18. method according to claim 7 also comprises: at least in part according to the described calculating location of described touch, and on described LCD display the update displayed image.

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