TWI416390B - Photo detector and display panel having the same - Google Patents

Abstract

The present invention provides a photo detector, which comprises a photo sensor device, a storage capacitor, a first TFT and a second TFT. The photo sensor device is controlled to reset the voltage of a node to a first voltage level. The storage capacitor is electrically connected to the node and controlled to discharge the voltage of the node to a second voltage level during a frame, according to the illuminance of the photo sensor device. The second voltage level decides a connecting voltage of the first TFT, and the second TFT outputs a readout voltage based on the connecting voltage.

Description

Light sensing device and display having the same

The present invention relates to a light sensing device, and more particularly to a light sensing device capable of increasing the aperture ratio of a display; the present invention further relates to a display having the above light sensing device.

With the rapid development of technology, internet, and communication, electronic products must seek direct interaction with users in addition to the novelty of technology to meet the needs of users in terms of convenience and interactivity. Therefore, many touch-sensitive products and interfaces have been introduced, such as ATMs, Personal Digital Assistants (PDAs), mobile phones or notebook computers. The touch-type product allows the direct interaction between the user and the electronic product by the user to approach or press the touch panel to complete the transmission, access and update of the data, thereby increasing the efficiency of the input.

In the prior art, the touch panel is integrated in a liquid crystal display (LCD), and a light sensing device is embedded in a thin-film transistor (TFT) array structure of the liquid crystal display. When the user approaches or presses the display panel with a finger, a stylus or other object, some or all of the light sources of the light sensing device in the panel are shielded, so the light sensing device can capture the finger by sensing the change of the light. , the image of the stylus or other object on the touch panel and its coordinate position.

The prior art discloses an optical sensing device that includes a plurality of sensing pixel circuits; each of the sensing pixel circuits includes a phototransistor transistor and a plurality of read film transistors; The thin film electro-crystal system is read as a reset, so that its gate must be electrically connected to a reset signal to read a first reset voltage. In addition, in order to reflect the electrical signal result of the pixel circuit at different shading levels, a second reset voltage is required, and a voltage level is formed between the second reset voltage and the first reset voltage. difference. Since these conventional techniques require additional control signals in addition to the existing circuits of the pixel unit, the circuit architecture is complicated. However, an overly complex circuit architecture will increase the wiring difficulty of the thin film transistor and increase the cost.

Moreover, since the light sensing signal is usually quite weak, if a complicated control circuit is additionally added to obtain a strong signal under the original circuit structure of the pixel unit, the aperture ratio of the display will be lowered. Therefore, it is conventionally difficult to balance the optical signal strength and the complexity of the sensing device when designing the optical sensor embedded in the display.

In view of this, an object of the present invention is to provide a light sensing device that uses the original circuit structure of the pixel unit without additional control signals, thereby simplifying the circuit structure and simplifying the layout.

Another object of the present invention is to provide a display comprising a plurality of the above-mentioned light sensing devices. Since the circuit structures of the light sensing devices are simple, the aperture ratio of the display is not reduced.

In an embodiment of the invention, a light sensing device is provided, comprising a light sensing component, a storage capacitor, a first thin film transistor, and a second thin film transistor. The light sensing component can reset the voltage of a node to a first voltage level, and the storage capacitor is electrically connected to the node, and according to the illuminance of the light sensing component, the image is The node is discharged to a second voltage level. The second voltage level controls a turn-on voltage of the first thin film transistor, and the second thin film transistor system outputs a read voltage according to the turn-on voltage.

In another embodiment of the present invention, a display includes a first substrate, a second substrate, a liquid crystal layer disposed between the first substrate and the second substrate, and a plurality of light sensing The effective display area is disposed on the second substrate. Each of the light sensing areas may be provided with a light sensing device, and the light sensing device includes a plurality of the above-mentioned light sensing devices.

The following description and examples are presented to explain the details of the invention. However, those skilled in the art should readily appreciate that the embodiments described herein are susceptible to variations and modifications. Therefore, the embodiments described below are not intended to limit the scope of the invention.

Please refer to the first figure, which is a system block diagram of a display according to an embodiment of the invention. The display comprises an effective display area 1, a gate line driver 2, an output controller 3, and a data line driver 4. In the effective display area 1, a plurality of gate lines and a plurality of output lines are insulated from each other to define a plurality of light sensing regions 10. In the first figure, the gate lines are indicated by G(i), and the output lines are indicated by out(j), where i and j represent index numbers, and the total number of i and j is not necessarily equal. . In each of the light sensing regions 10, a light sensing device 11 is electrically connected to an adjacent two gate lines and an output line, and outputs a read voltage.

Wherein, the gate line driver 2 sequentially applies a plurality of gate pulses to the gate lines G(i), except for turning on the transistors in each pixel, and also using To trigger the light sensing device 11 in each of the light sensing regions, for the pixel to be described later; and the output controller 3 is configured to capture the read voltage of each of the light sensing devices 11 and perform the required Signal processing or conversion. The data line driver 4 controls a plurality of data lines data for writing image data to a plurality of pixel units (displayed in the second A picture and the second B picture).

Please refer to FIG. 2A, which shows a schematic view of a first embodiment of the light sensing device of the present invention. Each of the light sensing devices 11 of the present invention is electrically connected to an adjacent first gate line G(n), a second gate line G(n+1), and an output line out; The measuring device 11 includes a photo sensing element P, a storage capacitor Cst, a first thin film transistor T1 and a second thin film transistor T2. Wherein, one end of the photo sensing element P is electrically connected to the second gate line G(n+1), and the other end defines a node X; the photo sensing element P can convert any optical signal into A component of an electrical signal, such as a photodiodes or photo thin film transistors. As shown in the first embodiment shown in FIG. 2A, the photo sensing element P can be a phototransistor transistor, one of its gate and source/drain and the second scan line G(n+1). Electrically connected, and another source/drain is used to define the node X. The following descriptions and the scope of application for patents use "source/bungee" in many places, which is synonymous with "source or bungee".

One end of the storage capacitor Cst is electrically connected to the node X, and the other end is electrically connected to a common voltage Vcom. The gate of the first thin film transistor T1 is electrically connected to the node X, and one of the source/drain electrodes is electrically connected to the first gate line G(n); the voltage level of the node X is used for controlling The on or off of the first thin film transistor T1 determines the magnitude of a turn-on voltage when the first thin film transistor T1 is turned on; the gate of the second thin film transistor T2 and the first gate The pole line G(n) is electrically connected, one of the source/drain electrodes is electrically connected to the output line out, and the other source/drain of the second thin film transistor T2 is different from the first thin film transistor T1. A source/drain is electrically connected.

The second A picture also shows a sub-pixel unit 12, the sub-pixel unit 12 is contained in a pixel unit, and each of the pixel units includes three sub-pixel units of red, green and blue. The second A diagram illustrates only one of the sub-pixel units 12, and the present invention is not limited to the sub-pixel unit 12 circuit shown. For the purpose of drawing the sub-pixel unit 12, only the circuit signal of the light sensing device 11 of the present invention can be used together with the pixel unit, so that no additional circuit signals need to be added, so that the circuit structure of the present invention is relatively simple.

Please refer to FIG. 2B, which shows a second embodiment of the light sensing device of the present invention, wherein the data line data and the output line out are shared, so that the light sensing device and the pixel unit are integrated, and the circuit structure is more simplify.

The third drawing shows a laminated structure of an embodiment of the display of the present invention. For the sake of simplicity, the structural drawing is only partially shown and simplified, and is not drawn to scale. As shown in the third figure, the display of the present invention includes a first substrate 41, a second substrate 42, and a liquid crystal layer 43 disposed between the first substrate 41 and the second substrate 42. The first substrate 41 forms a light shielding layer 44 on one side of the second substrate 42. The light shielding layer 44 defines a non-light transmitting region. In an embodiment, the light shielding layer 44 can be a black matrix. The third display shows that the effective display area 1 of the present invention is disposed on the second substrate 42 and defines the light sensing areas 10 in the effective display area 1. Each of the light sensing areas 10 can set the light perception. Measuring device 11. For convenience of display, the third figure only shows that one of the light sensing devices 11 is formed on the second substrate 42.

The light shielding layer 44 corresponds to the light sensing element P, and is provided with an opening 45. When the external object 46 shields the opening 45, an illuminance of the light sensing element P is changed, and the light sensing element P is based on the illuminance. The electrical signal is converted into an electrical signal of leakage current, and the illuminance is positively correlated with the magnitude of the leakage current.

The fourth figure is a voltage timing diagram of the present invention, which displays a plurality of preset periods 30. Each of the preset periods 30 includes a reset period 31, an integration period 32, and a read out period 33. The preset period 30 can be a frame time, for example 1/60 s.

Please refer to the second A diagram or the second B diagram. In the reset period 31 shown in the fourth figure, the gate line driver 2 (see the first figure) applies a pulse to the second gate. The pole line G(n+1) enables the second gate line G(n+1) to be enabled, thereby conducting light sensing electrically connected to the second gate line G(n+1) The component P resets the node X voltage of the photo sensing element P to a first voltage level.

Then, during the integration period, the first gate line G(n) and the second gate line G(n+1) adjacent to the photo sensing element P are all disabled, and are stored in the The charge of the storage capacitor Cst is continuously released via the photo-sensing element P, and the amount of charge released from the storage capacitor Cst is related to the illuminance of the photo-sensing element P, such as the photo-sensing element P being shielded by the external object 46. The illuminance will be lowered, thus causing the leakage current of the photo sensing element P to decrease, and the storage capacitance Cst will also reduce the discharge amplitude of the node X. Please refer to Figure 5A, which shows the difference in discharge amplitude of node X at two illuminances of high light and low light.

Please return to the fourth figure again. Then during the read period 33, the gate line driver 2 applies another pulse to the first gate line G(n) to make the first gate line G(n). ) becomes enabled, and the second thin film transistor T2 is turned on. Since one of the source/drain of the first thin film transistor T1 is electrically connected to the first gate line G(n), and the gate is electrically connected to the node X, the first thin film transistor T1 is also turned on. .

During the entire preset period 30, the node X continues to discharge according to the illuminance of the light sensing element P, to the end of the preset period 30 (ie, the last of the reading period 33) via the light sensing element P. , the node X is discharged to a second voltage level. The second voltage level controls the conduction degree of the first thin film transistor T1 such that the first thin film transistor T1 and the second thin film transistor have an on-voltage. Further, the second voltage level is related to the on-voltage. If the second voltage level is larger, the conduction degree of the first thin film transistor T1 is also increased, so that a large on-voltage is present. The turn-on voltage determines a read voltage of one of the second thin film transistors T2 via the turned-on second thin film transistor T2, and outputs the read voltage to the output line.

During a preset period 30 (or a picture time), all of the gate lines G(i) are sequentially scanned to obtain all of the read voltages of the light sensing device 11 in the light sensing region 10. Because the read voltage is related to the turn-on voltage, the turn-on voltage is determined by the second voltage level of the node X. Further, the second voltage level is related to the illuminance of the light sensing element P, and the illuminance is determined by the extent to which the external object 46 shields the light sensing element P. Figure 5B shows the difference in voltage amplitude between the high and low illumination levels of the read voltage. In this case, the reading voltage of all the light sensing regions 10 can be extracted, and the instantaneous image of the external object 46 and its coordinate position can be analyzed. If the pixel unit of the display or other devices and components are used together, the chroma can be generated or It is another function and will not be described here.

The light sensing device of the present invention uses the original circuit structure of the pixel unit, and does not need to add other control signals, so the circuit structure is simplified and the layout is simple. Moreover, by adjusting the preset period 30, the discharge amplitude of the node X can be increased, and the difference in the read voltage of the output is increased, thereby facilitating analysis and comparison of the illuminance.

The present invention has been disclosed in an embodiment as described above, but it is not intended to be limiting. Any and all such modifications and variations can be made without departing from the spirit and scope of the invention, and the scope of the invention is defined by the scope of the appended claims.

1‧‧‧effective display area
2‧‧ ‧ gate line driver
3‧‧‧Output controller
4‧‧‧Data line driver
10‧‧‧Light Sensing Area
11‧‧‧Light sensing device
T1‧‧‧ first film transistor
T2‧‧‧second film transistor
P‧‧‧Light sensing components
Cst‧‧‧ storage capacitor
X‧‧‧ node
12‧‧‧Subpixel Element
Data‧‧‧ data line
G(n)‧‧‧first gate line
G(n+1)‧‧‧second gate line
Out‧‧‧output line
Vcom‧‧‧Common voltage
30‧‧‧Preset period
31‧‧‧Reset period
32‧‧ During the period
33‧‧‧Reading period
41‧‧‧First substrate
42‧‧‧second substrate
43‧‧‧Liquid layer
44‧‧‧Lighting layer
45‧‧‧ openings
46‧‧‧ Foreign objects

The above and other objects, features, advantages and embodiments of the present invention will become more readily understood.

The first figure is a system block diagram of a display according to an embodiment of the invention;

2A is a schematic view showing a first embodiment of the light sensing device of the present invention;

2B is a schematic view showing a second embodiment of the light sensing device of the present invention;

3 is a simplified diagram of a cross-sectional laminated structure of an embodiment of the display of the present invention;

The fourth figure shows the timing diagram of the voltage signal of the present invention;

Figure 5A shows the difference in discharge amplitude of node X at two illuminances of high light and low light;

Figure 5B shows the difference in voltage amplitude between the high and low illumination levels of the read voltage.

11‧‧‧Light sensing device

T1‧‧‧ first film transistor

T2‧‧‧second film transistor

P‧‧‧Light sensing components

Cst‧‧‧ storage capacitor

X‧‧‧ node

12‧‧‧Subpixel Element

Data‧‧‧ data line

G(n)‧‧‧first gate line

G(n+1)‧‧‧second gate line

Out‧‧‧output line

Vcom‧‧‧Common voltage

Claims (7)

A light sensing device comprising:
a light sensing component capable of resetting a node voltage to a first voltage level;
a storage capacitor electrically connected to the node; the storage capacitor discharges the node to a second voltage level via the light sensing element according to an illuminance of the light sensing element in a predetermined period;
a first thin film transistor, the second voltage level controlling a turn-on voltage of the first thin film transistor;
a second thin film transistor electrically connected to the first thin film transistor;
The second thin film transistor is turned on during a reading period, and outputs a read voltage according to the turn-on voltage of the first thin film transistor. The light sensing device of claim 1, wherein the preset period is a frame time. The photo sensing device of claim 1, wherein the photo sensing element is a phototransistor transistor. A light sensing device comprising:
a photoelectric thin film transistor, a gate of the photoelectric thin film transistor is electrically connected to one of the source/drain electrodes and a second gate line, and the other source/drain is electrically connected to a node;
a storage capacitor, one end of the storage capacitor is electrically connected to the node, and the other end is electrically connected to a common voltage;
a first thin film transistor, the gate of the first thin film transistor is electrically connected to the node, and one of the source/drain electrodes is electrically connected to a first gate line;
a second thin film transistor, the gate of the second thin film transistor is electrically connected to the first gate line, and one of the source/drain electrodes is electrically connected to an output line, and the second thin film transistor is electrically connected Another source/drain is electrically connected to another source/drain of the first thin film transistor;
Wherein, the photo-transistor transistor enables the second gate line to be enabled during a reset period, and resets the voltage of the node to a first voltage level; the storage capacitor is based on the photo-transistor transistor Illuminating the node to a second voltage level via the photo-transistor transistor during one frame time; and enabling the first gate line during a read period to turn on the The second thin film transistor is configured to output a read voltage according to the second voltage level of the first thin film transistor gate. A display comprising:
a first substrate and a second substrate, the first substrate being disposed corresponding to the second substrate;
a liquid crystal layer disposed between the first substrate and the second substrate;
An effective display area is disposed on the second substrate; a plurality of light sensing areas are defined in the effective display area, and each of the light sensing areas can be provided with a light sensing device; the light sensing device includes:
a light sensing component capable of resetting a node voltage to a first voltage level;
a storage capacitor electrically connected to the node; the storage capacitor discharges the node to a second voltage level via the light sensing element according to an illuminance of the light sensing element in a predetermined period;
a first thin film transistor, the second voltage level controlling a turn-on voltage of the first thin film transistor;
a second thin film transistor electrically connected to the first thin film transistor;
The second thin film transistor is turned on during a reading period, and outputs a read voltage according to the turn-on voltage of the first thin film transistor. The display of claim 5, wherein the preset period is a picture time. The display device of claim 5, wherein a light shielding layer is formed on one side of the first substrate corresponding to the second substrate, and the light shielding layer is provided with an opening corresponding to the light sensing element.