JP5081020B2 - Liquid crystal display with built-in optical sensor - Google Patents

Abstract

An optical sensor liquid crystal display improving the detection degree of touch input to a display panel is provided to calculate the difference between reflecting light about fingers built in the liquid crystal display. A plurality of optical sensors(23) detects peripheral light which is income from the outside and reflection light by the touch input of a display panel(21). A driver circuit operates the pixel of the display panel. A timing controller(1) includes an image data output unit(14) controlling the operation of the driver circuit. According to the output signal from a plurality of optical sensors, a touch input detector(3) detects the touch input. A gamma change circuit changes image data into image data in which the luminance is higher than image data which is input to the timing controller.

Description

  The present invention relates to a photosensor built-in liquid crystal display device that detects a touch input to a display panel using a photosensor.

  A conventional liquid crystal display device includes a display panel in which a plurality of pixels are arranged in a matrix, and a plurality of photodetector circuits arranged in a matrix in the display panel. Each photodetection circuit has a photosensor (photosensor) that converts incident light into a photocurrent corresponding to the light intensity of the incident light. This liquid crystal display device detects a touch input to the display panel based on an output from a photosensor (see, for example, Patent Document 1).

FIG. 6 is a cross-sectional view showing an excerpt of the liquid crystal display 50 of the conventional liquid crystal display device disclosed in Patent Document 1, for example.
In FIG. 6, a liquid crystal display 50 includes a display panel 51 formed by filling a liquid crystal between two transparent substrates, and a backlight 52 that emits light (see broken line arrows) from the back side of the display panel 51. And a plurality of photosensors 53 arranged in the display panel 51. Further, the liquid crystal display 50 includes a display control unit that controls an image displayed on the display panel 51 and a touch input detection unit that processes an output signal from the photosensor 53 and detects a touch input (see FIG. (Not shown).

Here, for example, when the user puts a finger on the display panel 51, ambient light (refer to a two-dot chain line arrow) incident on the photosensor 53 is blocked at the portion corresponding to the finger or the backlight 52. Is reflected and is incident on the photosensor 53.
As a result, the luminance level of the output signal from the photosensor 53 in the portion corresponding to the finger varies as compared with the luminance level of the output signal in the other portion. The touch input detection unit detects a touch input to the display panel 51 based on the luminance level variation of the output signal.

For example, when the surroundings are bright, the touch input detection unit detects a portion where ambient light that should be incident on the photosensor 53 is blocked by a finger and becomes a shadow, that is, a portion where the luminance level of the output signal is lower than other portions. The touch input to the display panel 51 is detected.
FIG. 7 shows an image of the output signal from the photosensor 53 when the surroundings are bright, and the luminance level of the output signal in a cross section obtained by cutting the image with a line shown in the image.
FIG. 7 shows that the user's finger appears as a shadow. Also, it can be seen that the luminance level of the output signal changes greatly in the portion corresponding to the finger.

In addition, when the surroundings are dark, for example, the touch input detection unit displays a portion where the light from the backlight 52 is reflected by the finger, that is, a portion where the luminance level of the output signal is higher than the other portions. The touch input is detected.
FIG. 8 shows an image of the output signal from the photosensor 53 when the surroundings are dark, and the luminance level of the output signal in a cross section obtained by cutting the image with the lines shown in the image.
From FIG. 8, it can be seen that the light from the backlight 52 is reflected on the user's finger and becomes brighter. Also, it can be seen that the luminance level of the output signal changes greatly in the portion corresponding to the finger.

JP 2007-94606 A

However, the prior art has the following problems.
That is, when the user places a finger on the display panel, if there is no difference between the ambient light and the reflected light from the finger, for example, a bright image is displayed when the surrounding is bright, or a dark image is displayed when the surrounding is dark Is displayed, there is a region where neither shadow nor reflection can be determined. In such a region, there is a problem that it is impossible to detect a touch input to the display panel.

A graph showing the output signal from the photosensor when there is no difference between the ambient light and the reflected light from the finger, and the luminance level of the output signal in the cross section obtained by cutting the image with the line shown in the image 9 shows.
From FIG. 9, the user's finger cannot be recognized as a shadow or a reflection. In addition, there is no portion in which the luminance level of the output signal is greatly changed, and the touch input cannot be detected.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a liquid crystal display device with a built-in optical sensor that can improve the detection accuracy of touch input to the display panel. It is in.

  An optical sensor built-in liquid crystal display device according to the present invention is arranged in a display panel, drives a plurality of optical sensors that detect ambient light incident from the outside and reflected light by touch input to the display panel, and pixels of the display panel And a timing controller having an image data output means for controlling the operation of the driver circuit, and a touch input detection means for detecting a touch input based on output signals from a plurality of optical sensors. The controller multiplies the clock frequency of the image data input to the timing controller by N (N is an integer equal to or greater than 2) to generate an N-times clock frequency, and writes the image data to the frame memory and N-times clock The image data written in the frame memory is read N times repeatedly according to the frequency. The N-speed circuit and the N-speed circuit from the N-speed circuit to the timing controller while maintaining the luminance when combining the N image data of at least two pieces of image data. The image data output means further includes a gamma change circuit that changes the image data to a higher brightness and lower brightness than the input image data and outputs the changed N image data. The N image data after the change from the change circuit is output to the driver circuit at a desired output timing, and the touch input detection means detects the touch input using the N image data after the change. is there.

According to the photosensor built-in liquid crystal display device of the present invention, the N × speed circuit repeatedly reads and outputs the image data written in the frame memory N times at the N × clock frequency. In addition, the gamma changing circuit outputs at least two pieces of image data out of the same N pieces of image data from the N-times speed circuit as image data having higher brightness and lower brightness than the image data input to the timing controller. Change to image data. At this time, the luminance when N pieces of image data are combined is equal to the luminance of the image data input to the timing controller. The touch input detection means detects touch input using image data having higher brightness and image data having lower brightness than the image data input to the timing controller.
Here, by using image data with high brightness, for example, reflected light reflected by a user's finger can be strengthened. Further, by using image data with low brightness, the shadow of the user's finger can be increased.
Therefore, it is possible to provide a difference between the ambient light when the user places the finger on the display panel and the reflected light by the finger without changing the luminance that is visible to the user. Detection accuracy can be improved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts will be described with the same reference numerals.
In the following embodiments, a case where image data is input to the timing controller at a clock frequency of 60 Hz will be described as an example, but the clock frequency is not limited to this value.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a photosensor built-in liquid crystal display device according to Embodiment 1 of the present invention.
In FIG. 1, the optical sensor built-in liquid crystal display device includes a timing controller 1, a liquid crystal display 2, and a touch input detection unit 3 (touch input detection means).
Here, image data is input to the timing controller 1 at a clock frequency of 60 Hz.

First, the configuration of the timing controller 1 will be described.
The timing controller 1 includes a PLL (Phase Locked Loop) circuit 11, a double speed circuit 12 (N double speed circuit), a gamma change circuit 13, an image data output unit 14 (image data output means), and a frame memory 15. Contains.
The frame memory 15 may be provided outside the timing controller 1.

Next, the function of the timing controller 1 will be described.
The PLL circuit 11 doubles the clock frequency of the image data input to the timing controller 1 to generate a double clock frequency. Specifically, a clock frequency of 120 Hz, which is twice 60 Hz, is generated.
The double speed circuit 12 once writes the image data input to the timing controller 1 in the frame memory 15. The double speed circuit 12 repeatedly reads the image data written in the frame memory 15 twice with the double clock frequency (120 Hz) generated by the PLL circuit 11 and outputs the image data to the gamma change circuit 13.

  The gamma changing circuit 13 selects one of the two identical image data from the double speed circuit 12 as image data having a higher luminance than the image data input to the timing controller 1 (hereinafter “bright”). (Referred to as “image data”). Further, the gamma changing circuit 13 changes the other image data to image data having a lower luminance than the image data input to the timing controller 1 (hereinafter referred to as “dark image data”).

Here, the gamma changing circuit 13 has a look-up table, and adds or divides a predetermined luminance according to the luminance of the input image data, and the input image data is converted into a bright image data and a dark image. Change to data.
At this time, the brightness of the bright image data and the dark image data is changed so that the brightness when the bright image data and the dark image data are combined is equal to the brightness of the image data input to the timing controller 1.
The gamma changing circuit 13 outputs the bright image data and the dark image data to the image data output unit 14 at a double clock frequency (120 Hz).
The image data output unit 14 outputs bright image data and dark image data to the liquid crystal display 2 as drive control signals at a desired timing.

Next, the configuration of the liquid crystal display 2 will be described.
The liquid crystal display 2 includes a display panel 21 that is formed by filling a liquid crystal between two transparent substrates, a backlight 22 that emits light (see broken line arrows) from the back side of the display panel 21, and a display panel. And a plurality of photosensors 23 (photosensors) arranged in 21.

The display panel 21 has a plurality of pixels arranged in a matrix. The photosensors 23 are arranged in a matrix in the display panel 21. Note that the number of photosensors 23 may be the same as the plurality of pixels or may be smaller than the plurality of pixels.
The liquid crystal display 2 is provided with a gate driver (driver circuit) and a source driver (driver circuit) (not shown) for driving a plurality of pixels arranged on the display panel 21.

Next, functions of the liquid crystal display 2 will be described.
The display panel 21 displays an image corresponding to bright image data and dark image data in accordance with drive control signals input from the timing controller 1 to the gate driver and source driver.
At this time, since the bright image data and the dark image data are output at the double clock frequency (120 Hz), an image is displayed with the same brightness as the brightness of the image data input to the timing controller 1 to the user's eyes. Looks like it has been.

  Further, as described above, for example, when the user places a finger on the display panel 21, ambient light (see a two-dot chain line arrow) incident on the photosensor 23 is blocked at a portion corresponding to the finger, or The light from the backlight 22 is reflected and incident on the photosensor 23. At this time, the photosensor 23 converts the incident light into a current corresponding to the light intensity of the incident light, and outputs an output signal to the timing controller 1.

  The touch input detection unit 3 detects touch input to the display panel 21 of the liquid crystal display 2 based on output signals from a plurality of photosensors 23 provided on the liquid crystal display 2, and outputs, for example, touch coordinates. The touch input detection by the touch input detection unit 3 is executed by the same process as the touch input detection unit described in the background art.

Here, when the user places a finger on the display panel 21, the inventor changes the image data to bright image data and dark image data when there is no difference between ambient light and reflected light from the finger. An experiment to detect touch input was conducted.
The experimental method is as follows.

First, on the uniform luminance screen (hereinafter referred to as “background 128/255 solid screen”) in which the brightness of the image data is set at the 128th step in 256 steps (0 to 255), the ambient illuminance is adjusted, and touch input is performed. The illuminance is set so that the touch cannot be detected.
FIG. 2 shows an output signal from the photosensor 23 on the background 128/255 solid screen as an image and the luminance level of the output signal in a cross section obtained by cutting the image along the line shown in the image.
From FIG. 2, the user's finger cannot be recognized as a shadow or a reflection. In addition, there is no portion in which the luminance level of the output signal is greatly changed, and the touch input cannot be detected.

Subsequently, under the same illuminance conditions, the brightness of the image data was made higher than that of the background 128/255 solid screen and changed to the background 255/255 solid screen (bright image data).
FIG. 3 shows an output signal from the photosensor 23 on the background 255/255 solid screen as an image and the luminance level of the output signal in a cross section obtained by cutting the image along the line shown in the image.
FIG. 3 shows that the light from the backlight 22 is reflected on the user's finger and becomes brighter. In addition, it can be seen that the luminance level of the output signal changes greatly in the portion corresponding to the finger (see circle).

Next, under the same illuminance conditions, the brightness of the image data was made lower than that of the background 128/255 solid screen and changed to the background 0/255 solid screen (dark image data).
FIG. 4 shows an output signal from the photosensor 23 on the background 0/255 solid screen as an image and the luminance level of the output signal in a cross section obtained by cutting the image along the line shown in the image.
From FIG. 4, it can be seen that the user's finger appears as a shadow. In addition, it can be seen that the luminance level of the output signal changes greatly in the portion corresponding to the finger (see circle).

The result of this experiment is schematically shown in FIG.
In FIG. 5, the image data of 60 Hz indicates a background 128/255 solid screen. The 120 Hz bright image data and dark image data indicate a background 255/255 solid screen and a background 0/255 solid screen, respectively.

  As shown in FIG. 5, when the ambient illuminance is set to the touch undetectable illuminance on the background 128/255 solid screen, the luminance level of the output signal is flat and the touch input cannot be detected. In addition, when the background 128/255 solid screen is changed to a 255/255 solid screen and a background 0/255 solid screen under the same illuminance conditions, a change occurs in the luminance level of the output signal, and touch input can be detected. it can.

  That is, by changing the image data input at a clock frequency of 60 Hz to bright image data and dark image data and outputting the image data at a clock frequency of 120 Hz, touch input is detected without changing the luminance visible to the user. be able to.

According to the optical sensor built-in liquid crystal display device according to the first embodiment of the present invention, the double speed circuit 12 repeatedly reads and outputs the image data written in the frame memory 15 at the double clock frequency. The gamma changing circuit 13 changes one of the two identical image data from the double speed circuit 12 to bright image data having higher luminance than the image data input to the timing controller 1. Further, the gamma changing circuit 13 changes the other image data to dark image data having lower luminance than the image data input to the timing controller 1. At this time, the brightness of the bright image data and the dark image data is changed so that the brightness when the bright image data and the dark image data are combined is equal to the brightness of the image data input to the timing controller 1. The touch input detection unit 3 detects touch input using the bright image data and the dark image data.
Here, by using the bright image data, the reflected light reflected by the user's finger can be strengthened. Further, by using the dark image data, it is possible to darken the shadow by the user's finger.
Therefore, it is possible to provide a difference between the ambient light when the user places the finger on the display panel 21 and the reflected light by the finger without changing the luminance visible to the user. Input detection accuracy can be improved.

In the first embodiment, the case where the clock frequency is doubled in the PLL circuit 11 has been described. However, the present invention is not limited to this.
The PLL circuit 11 may increase the clock frequency by three times or more. At this time, the image data written in the frame memory 15 is repeatedly read according to the clock frequency that has been tripled or more and output to the gamma changing circuit 13.
Further, the gamma changing circuit 13 changes at least two pieces of image data among the plurality of inputted same image data to bright image data and dark image data. Specifically, for example, when the clock frequency is tripled, the gamma changing circuit 13 changes one image data to bright image data, and the other image data to dark image data. The remaining image data is output as it is without changing the luminance.
When the PLL circuit 11 increases the clock frequency by three times or more, the display on the display panel 21 can be switched without changing the luminance visible to the user.

It is a block diagram which shows the liquid crystal display device with a built-in optical sensor which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the output signal from the photo sensor in the background 128/255 solid screen, and the luminance level of an output signal. It is explanatory drawing which shows the output signal from the photosensor in the background 255/255 solid screen, and the luminance level of an output signal. It is explanatory drawing which shows the output signal from the photo sensor in the background 0/255 solid screen, and the luminance level of an output signal. It is a schematic diagram which shows the result of having implemented the experiment which changes image data into bright image data and dark image data, and detects a touch input. It is sectional drawing which extracts and shows the liquid crystal display of the conventional liquid crystal display device. It is explanatory drawing which shows the luminance level of the output signal from a photosensor in case the periphery is bright, and an output signal. It is explanatory drawing which shows the luminance level of the output signal from a photosensor in case the periphery is dark, and an output signal. It is explanatory drawing which shows the output signal from a photosensor in case there is no difference with ambient light and the reflected light by a finger | toe, and the luminance level of an output signal.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Timing controller, 2 Liquid crystal display, 3 Touch input detection part (touch input detection means), 11 PLL circuit, 12 Double speed circuit (N speed circuit), 13 Gamma change circuit, 14 Image data output part (Image data output means) , 15 frame memory, 21 display panel, 22 backlight, 23 photosensor (light sensor).

Claims (3)

A plurality of optical sensors arranged in the display panel for detecting ambient light incident from the outside and reflected light by touch input to the display panel;
A driver circuit for driving the pixels of the display panel;
A timing controller having image data output means for controlling the operation of the driver circuit;
Touch input detection means for detecting the touch input based on output signals from the plurality of optical sensors,
The timing controller is
A PLL circuit that generates N times the clock frequency by multiplying the clock frequency of the image data input to the timing controller by N (N is an integer of 2 or more);
Writing the image data into the frame memory, and N-times speed circuit for repeatedly reading and outputting the image data written in the frame memory N times at the N-times clock frequency;
Among the N pieces of the same image data from the N double speed circuit, at least two pieces of image data are input to the timing controller while maintaining the brightness when the N pieces of image data are combined. A gamma change circuit that changes the image data to be higher and lower in brightness than the image data, and outputs the changed image data as N pieces of image data.
The image data output means outputs the N pieces of image data after the change from the gamma change circuit to the driver circuit at a desired output timing,
The liquid crystal display device with a built-in optical sensor, wherein the touch input detection means detects the touch input using the N pieces of image data after the change.   The liquid crystal display device with a built-in optical sensor according to claim 1, wherein the optical sensor is a photosensor that converts the ambient light and the reflected light into a current corresponding to light intensity.   3. The liquid crystal display device with a built-in optical sensor according to claim 1, wherein the N is two.

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