KR20090104319A - Organic Light Emitting Diode Pixel Circuit having Optical Sensing Function, And Display Device having Pixel Circuit - Google Patents

Abstract

PURPOSE: An organic light emitting diode pixel circuit having an optical sensing function, and a display device having pixel circuit are provided to reduce the number of a device which is added to an AMOLED pixel circuit. CONSTITUTION: In an organic light emitting diode pixel circuit having an optical sensing function, a pixel(40) of an organic light-emitting diode has an optical detection function by combining a scanning line and a data line. The pixel of the organic light emitting diode is operated by a current corresponding to a voltage of the image signal transmitted through a data line. A forward bias is supplied to a pixel unit of the organic light-emitting diode in response to a first control signal.

Description

Organic light emitting diode (OLED) pixel circuit having a light sensing function, and a display device comprising the same {Organic Light Emitting Diode Pixel Circuit having Optical Sensing Function, And Display Device having Pixel Circuit}

The present invention relates to a pixel circuit of an organic light emitting diode (OLED), and more particularly to a pixel circuit of an organic light emitting diode (OLED) having a light sensing function, and a method of operating a display device having a light sensing function including the same. will be.

Recently, as the demand for portable electronic devices increases, efforts have been made to include various functions other than displays in the portable electronic devices. Among them, research is being conducted to realize various functions using an optical sensor that detects external light or light of the display itself.

Typically, the ambient light detection circuit that adjusts the brightness of the display by detecting light around the display, the touch panel circuit that detects the area covered by the hand using the light around the display or the light of the display itself, and the light of the display itself on the document. Optical scanners, such as reflecting and detecting them, use optical sensors for multifunctional displays.

The light sensor receives the light signal from the optical sensor and converts it into an electrical signal. A light-receiving element such as a photodiode is recently used. Research and development are underway.

1 is a circuit diagram of a conventional AMOLED (Active Matrix Organic Light Emitting Diode) pixel circuit. FIG. 2 is an operation timing diagram of the AMOLED pixel circuit of FIG. 1.

Referring to FIG. 1, a conventional AMOLED pixel circuit includes an OLED light emitting device, five transistors T1, T2, T3, T4, and T5, and two capacitors C1 and C2.

When n-1 scan line signal scan [n-1] is selected as 'low', T3 and T2 are turned on so that T1 has a diode-connected structure, and the voltage at the right node of C2 is charged to VDD-Vth, T1. The voltage at the left node is charged to VDD so that C2 stores Vth, T1. If the n-th scan line signal scan [n] is selected as 'low', T5 is turned on and the voltage of the image signal transmitted through the data line is applied to the left node of C2. At the same time, due to the coupling effect of C2, the gate node voltage of T1 is also changed to VDD-Vth, T1-ΔV to compensate for the threshold voltage deviation, thereby driving the current source T1.

The change in the characteristics of the threshold voltage and the like of the driving transistor operating as the current source affects the brightness and uniformity of the AMOLED panel. Accordingly, in the conventional AMOLED pixel circuit, an additional circuit element is used to compensate for the threshold voltage deviation of the driving transistor T1 which causes a current to flow through the OLED light emitting element to emit the OLED light emitting element.

When AMOLED (Active Matrix Organic Light Emitting Diode) pixel circuits are manufactured using poly-Si (Thin Film Transistor) TFTs, the AMOLED pixel circuit is composed of a circuit that compensates for the characteristics of the poly-Si TFT. The number of TFTs and capacitors is larger than in the active matrix liquid crystal display (AMLCD) pixel circuit. Therefore, adding a separate TFT and a control signal line in the AMOLED pixel circuit to form a pixel circuit including a readout circuit such as a source follower is very burdensome in terms of integration degree and aperture ratio.

Accordingly, a first object of the present invention is to provide a pixel circuit of an organic light emitting diode (OLED) having a light sensing function capable of reducing the number of elements added to the AMOLED pixel circuit.

In addition, a second object of the present invention is to provide a display device including the pixel circuit.

A pixel circuit of an organic light emitting diode (OLED) having a light sensing function coupled to a scan line and a data line according to an aspect of the present invention for achieving the first object of the present invention is an image transferred through the data line An organic light emitting diode (OLED) pixel unit configured to emit an organic light emitting diode (OLED) based on a current corresponding to a voltage of a signal, and a forward direction in the organic light emitting diode (OLED) pixel unit upon forward bias in response to a first control signal A light-receiving element for providing a bias voltage and flowing a photo-leakage current during reverse biasing, and a first output-out operation from the organic light emitting diode (OLED) pixel portion to the data line in response to a second control signal in a sensing mode operation; It includes a switching unit. The pixel circuit may further include a second switching unit electrically connecting the organic light emitting diode (OLED) pixel unit to the light receiving element in response to a fourth control signal when the pixel circuit is operated in the sensing mode. The organic light emitting diode (OLED) pixel unit provides an organic light emitting diode (OLED) and a current corresponding to a voltage of an image signal provided through the data line to the organic light emitting diode (OLED), thereby providing the organic light emitting diode (OLED). A diode coupled to the driving transistor in response to a first scan line signal, a first switching element providing a voltage of the image signal to a control electrode of the driving transistor in response to a first scan line signal, and a second transistor in response to a second scan line signal A second switching element operated in a structure, a first capacitor storing a voltage of the image signal, a second capacitor providing a voltage of the image signal to a control electrode of the driving transistor by a coupling effect, and the driving A coupling coupled between a transistor and the organic light emitting diode (OLED) and switched in response to a third control signal It may include three switching elements. In the sensing mode operation, the third control signal may be maintained in an active state to turn off the third switching device to block light emission of the organic light emitting diode OLED. The first switching unit, the second switching unit, the first switching element, the second switching element, the third switching element, and the driving transistor are P-type thin film transistors (TFTs), and receive the light. The device may be a p-intrinsic-metal diode.

In addition, the pixel circuit of the organic light emitting diode OLED having the light sensing function coupled to the scan line and the data line according to another aspect of the present invention for achieving the first object of the present invention is organic A light emitting diode (OLED), a first switching element coupled to the data line to provide a voltage of an image signal provided through the data line in response to a first scan line signal, and one end of the first switching element and the second A first capacitor coupled to a power supply voltage to store the voltage of the image signal, a second capacitor having one end coupled to one end of the first capacitor, a control electrode coupled with the other end of the second capacitor, and a first electrode The current is coupled to the second power supply voltage to provide the current corresponding to the voltage of the image signal provided through the data line to the organic light emitting diode OLED. A driving transistor configured to emit a light emitting diode (OLED), a control electrode of the driving transistor, and a second electrode of the driving transistor to operate the driving transistor in a diode connection structure in response to the second scan line signal; A second switching element, a third switching element coupled between the second electrode of the driving transistor and the organic light emitting diode (OLED) and switched in response to a third control signal, and a forward bias or reverse direction in response to the first control signal A first switching unit coupled to a light receiving device reversely biased, coupled to the data line and a second electrode of the driving transistor, and configured to perform a readout operation in response to a second control signal during a sensing mode operation; It is coupled between the other end and the light receiving element and turned on in response to a fourth control signal when operating in a sensing mode. And a second switching unit for maintaining a state. The first switching unit, the second switching unit, the first switching element, the second switching element, the third switching element, and the driving transistor are P-type thin film transistors (TFTs), and receive the light. The device may be a p-intrinsic-metal diode.

In addition, a display device having a light sensing function according to an aspect of the present invention for achieving the second object of the present invention is a scan line for transmitting a scan line signal, a data line for transmitting an image signal, and the scan line A scan driver for generating a scan line signal for driving, a data driver for driving the data line, an organic light emitting diode (OLED) pixel electrically coupled to the scan line and the data line, and having a light sensing function A pixel circuit of the organic light emitting diode OLED, wherein the pixel circuit of the organic light emitting diode OLED emits the organic light emitting diode OLED based on a current corresponding to a voltage of an image signal transmitted through the data line. And forward bias in the organic light emitting diode (OLED) pixel portion when forward biased in response to a first control signal. A light-receiving element that provides a voltage and supplies an optical leakage current during reverse bias, and a first switching to perform a readout operation from the organic light emitting diode (OLED) pixel unit to the data line in response to a second control signal in a sensing mode operation; Contains wealth. The display device having the light sensing function may further include a second switching unit electrically connecting the organic light emitting diode (OLED) pixel unit and the light receiving element in response to a fourth control signal when the display device operates in the sensing mode. .

 As described above, according to the present invention, the pixel circuit itself may perform the readout circuit function by minimizing the number of elements added to the existing AMOLED pixel. Therefore, the present invention can be applied to an AMOLED application field having a sensing function such as an image scanner or a touch screen.

In addition, the transistors of the pixel circuit are all implemented by p-type TFTs, and the light receiving element of the sensing pixel circuit is implemented by p-i-m (p-intrinsic-metal) diode, thereby reducing the process cost.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the drawings, similar reference numerals are used for similar elements.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component. The term and / or includes a combination of a plurality of related items or any item of a plurality of related items.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, the same reference numerals will be used for the same means regardless of the reference numerals in order to facilitate the overall understanding.

3A illustrates a pixel circuit having a light sensing function according to an embodiment of the present invention. 13 is a block diagram illustrating a flat panel display having a light sensing function according to an embodiment of the present invention.

Referring to FIG. 13, a flat panel display having an optical sensing function according to an embodiment of the present invention includes a scan driver 200, a data driver 300, a timing controller 400, and a pixel unit 500.

The timing controller 400 generates a scan control signal to control the scan driver 200, and generates a data control signal to control the data driver 300.

The scan driver 200 includes a plurality of scan line signals scan1,..., Scan N for selecting at least one of the plurality of scan lines, and a plurality of control signals em1, read1, Vref1 for controlling a sensing operation. , ..., em N, read N, Vref N) are provided to the pixel unit 500.

The data driver 300 provides an image signal to the pixel unit 500 through a plurality of data lines data1, data2,..., Data M-1, and data M.

The pixel unit 500 is composed of a plurality of pixel circuits 100.

FIG. 3A representatively illustrates one of N X M pixels constituting an organic light emitting diode (OLED) pixel unit of a flat panel display having a light sensing function according to an embodiment of the present invention.

Referring to FIG. 3A, a pixel circuit 100 having a light sensing function according to an embodiment of the present invention may include a light receiving element 10, a first switching unit 30, a second switching unit 20, and an organic light emitting diode. (OLED) pixel portion 40 is included.

The organic light emitting diode (OLED) pixel unit 40 includes four transistors P1, P2, P3, and P4, two capacitors C1 and C2, and an OLED cell E. The transistor of the organic light emitting diode (OLED) pixel unit 40 may be implemented with a P-type thin film transistor (TFT).

The first switching device 30 is turned on in response to the control signal read to perform a readout operation in the sensing mode. In detail, when the control signal read becomes 'low', the first switching device 20 is turned on to perform a readout operation in the sensing mode. The first switching element 30 may be implemented with a transistor P6. The first switching element 30 may be implemented with, for example, a p-type thin film transistor (TFT).

When the second switching unit 20 operates in the sensing mode, the second switching unit 20 maintains a turn-on state in response to the control signal int to electrically connect the organic light emitting diode (OLED) pixel unit 40 to the light receiving element 10. The second switching element 20 may be implemented with a transistor P5. The second switching element 20 may be implemented by, for example, a p-type thin film transistor (TFT).

The light receiving element 10 may be made of a diode D.

In order to reduce process costs, the transistors of the pixel circuit 100 may be implemented as p-type TFTs. In addition, to reduce the process cost, the diode D of the pixel circuit 100 may be implemented as a p-i-m (p-intrinsic-metal) diode.

The pixel circuit 100 may be formed one per unit pixel for each of an R (Red) OLED pixel, a G (Green) OLED pixel, and a B (Blue) OLED pixel. The pixel circuit 100 may be formed on a transparent insulating substrate.

4 and 5 are conceptual views illustrating a case in which the pixel circuit of FIG. 3A operates in a display mode, and FIGS. 6 to 8 are conceptual views illustrating a case where the pixel circuit of FIG. 3A operates in a sensing mode. . 9A is a timing diagram illustrating a display mode and a sensing mode operation of the pixel circuit of FIG. 3A.

Hereinafter, an operation of the pixel circuit according to an exemplary embodiment of the present invention will be described with reference to FIGS. 3A and 4 to 9.

When the pixel circuit according to the exemplary embodiment of the present invention operates in the display mode, first, the n-1 th scan line signal is 'low', the control signal em is 'high', the control signal int is 'low', and the control signal. When Vref becomes 'high', as shown in FIG. 4, transistor P5 is turned on, P2 is turned on, and driving transistor P1 is diode-connected.

Next, when the n th scan line becomes 'low', the n-1 th scan line signal becomes 'high', the control signal em becomes 'high', and the control signal int becomes 'high', as shown in FIG. 5. As described above, the transistor P3 is turned on, and a voltage corresponding to the image signal is applied to one side of the capacitor C1 through the data line, and a voltage corresponding to the image signal is applied to the gate of the transistor P1 via the capacitor C1. Thereafter, when the n th scan line signal becomes 'high' and the control signal em becomes 'low', the switching transistor P3 is turned off, the switching transistor P4 is turned on, and the voltage charged in the capacitor C1 is applied to the gate of the driving transistor P1. A current corresponding to the voltage applied to the gate flows from the drain of the driving transistor P1 to the source. The same forward current as that flowing through the driving transistor P1 flows through the organic light emitting diode OLED, and light of intensity corresponding to the current emits light.

When the control signal em is 'high', the switching transistor P4 is turned off so that no current flows in the organic light emitting diode OLED, so light does not emit from the organic light emitting diode OLED.

When the pixel circuit according to the exemplary embodiment of the present invention operates in the sensing mode, the n th scan line signal scan [n] is initially 'high' and the n-1 th scan line signal scan [n-1] is 'low'. "is selected as the control signal em is' low when", Vref is' raised to high ', a, by a forward bias V of pim diode as shown in Figure 6 (Vref-V _{oN, pim)} to the left of C1 It is applied to the node N2, the transistor P2 is turned on to form a diode connection structure, and the right node N1 of the capacitor C1 is charged to VDD-Vth, P1. As with the display mode, capacitor C2 stores the voltage of VREF- (VDD-Vth, P1).

The control signal Vref is then changed to a 'low' voltage to apply a reverse bias to the p-i-m diode D. When the n-th scan line signal scan [n] is selected as 'low', transistor P3 is turned on as shown in FIG. 7 so that a voltage for writing a reference current of transistor P1 as a current source is applied from the data line. Due to the coupling effect of the capacitor C1, the gate node voltage of the driving transistor P1 is also lowered, and the current flowing through the transistor P1 becomes the reference current by the gate node voltage.

With the reverse bias applied to the pim diode D, the left node N2 voltage of the capacitor C1 is discharged by the light leakage current flowing through the pim diode D during the integration period, and the right node N1 voltage is similarly coupled to the capacitor C1. Reduced by effect. The magnitude of the reduced voltage may be determined by the intensity of the external light, the integration time, and the size of the capacitor C2.

After about one frame time, when the n-3 th scan line signal scan [n-3] is selected as 'low', the control signal int is also selected as 'low' and as shown in bold solid lines in FIG. 8, the transistors P1, A readout operation is performed through the data line (readout line) via P6. In response to the voltage reduced by the photo-leakage current of the p-i-m diode D, the reference current flowing in the transistor P1 increases inversely and flows through the data line to the external circuit.

When the pixel circuit according to the exemplary embodiment of the present invention operates in the sensing mode, the control signal em is kept high to keep the transistor P4 off.

In the sensing mode, the pixel circuit according to an embodiment of the present invention performs an image scanner operation. The intensity of light reflected from a document placed on the flat panel display surface is determined by the gray level of the image on the document. The pixel circuit detects the intensity of the reflected light. Accordingly, the pixel circuit according to an exemplary embodiment of the present invention may perform not only a display operation through light emission but also a sensing operation for detecting reflected light at the same time.

FIG. 10 is a conceptual diagram illustrating a display operation and a sensing operation performed for each scan line of the pixel circuit of FIG. 3A. Hereinafter, it is assumed that the nth scan line is an even scan line.

As shown in FIG. 10, even-numbered scan lines (..., scan [n + 2], scan [n], scan [n-2], ...) perform sensing operations, and odd-numbered scans Lines (..., scan [n + 1], scan [n-1], scan [n-3], ...) perform a luminous operation for the display.

That is, in the pixel circuit according to the exemplary embodiment of the present invention, the pixels on the odd horizontal lines may emit light with the strongest light, and the pixels on the even horizontal lines may perform the sensing operation. Alternatively, the pixel circuit according to the embodiment of the present invention is formed on a transparent insulating substrate such that pixels on odd-numbered horizontal lines perform display operations, and pixels on even-numbered horizontal lines perform sensing operations. Can be used as a touch screen.

As shown in FIG. 10, the pixel circuit connected to the n-th scan line includes a threshold voltage Vth compensation of the driving transistor P1 shown in FIG. 6, a reset operation shown in FIG. 7, and FIG. 8. The integration and readout operations shown in FIG. 1 are sequentially performed.

Since the data line is used when the reset operation or the readout operation of FIG. 7 is performed in the sensing mode, as illustrated in FIG. 8, the pixel connected to the even-numbered scan line operating in the sensing mode is reset or readout operation (FIG. In the case of performing block B of FIG. 8, it is preferable to design such that a pixel connected to an odd-numbered scan line operating in the display mode does not perform an operation such as block A of FIG. 8, which writes data to the data line. .

The pixel circuit of the present invention may be implemented with a PMOS transistor as shown in FIG. 3A or may be implemented with an NMOS transistor.

3B illustrates a pixel circuit according to another embodiment of the present invention. 3B is a circuit diagram illustrating an example in which a pixel circuit is implemented using an NMOS transistor. When the pixel circuit is implemented using an NMOS transistor, a p-i-m diode or a p-i-n diode may be used as the light receiving device.

In the pixel circuit according to another exemplary embodiment of the present invention, when the scan line [n-1] becomes 'high' to compensate for the threshold voltage deviation of the driving transistor N1, the transistor N2 is turned on to have a diode connection structure.

The switching transistor N6 is turned on when the control signal read becomes 'high' to perform a readout operation in the sensing mode.

FIG. 9B is a timing diagram illustrating a display mode and a sensing mode operation of a pixel circuit implemented with the NMOS transistor of FIG. 3B.

In the display mode operation and the sensing mode operation of the pixel circuit implemented with the NMOS transistor of FIG. 9B, the voltage states of high or low levels of scan [n], scan [n-1], control path int, read, em, and Vref are shown in FIG. 9A. Since the operation is the same except that the operation timing diagram of the pixel circuit is opposite to that in FIG.

A pixel circuit according to an embodiment of the present invention is formed one for each sub-pixel of R (Red), G (Green), and B (Blue), or a unit pixel consisting of R, G, and B. one pixel per pixel).

3C is a circuit diagram illustrating a pixel circuit according to another exemplary embodiment of the present invention.

3C shows an example in which one pixel circuit is formed for a unit pixel consisting of R, G, and B. Referring to FIG.

Referring to FIG. 3C, a pixel circuit according to another exemplary embodiment of the present invention may be implemented by using one p-i-m diode commonly used for R, G, and B pixels.

11 and 12 are graphs illustrating simulation results of the pixel circuit of FIG. 3A, according to an exemplary embodiment. The sensing output current of the pixel circuit is represented by the vertical axis, and the optical leakage current I _PIM is represented by the horizontal axis.

11 and 12 illustrate the light leakage current flowing through the pim diode to 0.6, 2.6, 12.0, and 52.0 pA in order to verify the operation of the pixel circuit of the designed AMOLED pixel. This is obtained by simulating sensing output current.

0.7 Volt, 이동도가

10 % 씩 각각 변하여도 72 nA이내의 오차를 갖고 0.35 내지 1.33 μA의 출력 전류 범위를 갖는다는 것을 확인할 수 있다. Referring to FIG. 11, the threshold voltage of transistor P1 as a current source is

0.7 Volt, mobility

It can be seen that even with each change of 10%, it has an error within 72 nA and an output current range of 0.35 to 1.33 μA.

0.7 Volt, 이동도가

20 % 씩 각각 변하여도 196 nA이내의 오차를 갖고 0.35 ~ 1.42 μA의 출력 전류 범위를 갖는다는 것을 확인할 수 있다.Referring to FIG. 12, the threshold voltage of transistor P1 as a current source is

0.7 Volt, mobility

It can be seen that even with each change of 20%, it has an error within 196 nA and an output current range of 0.35 to 1.42 μA.

Through the above performance verification, the pixel circuit according to the embodiments of the present invention can be applied to an AMOLED application field having a sensing function by performing a readout circuit function by minimizing the number of additional elements. .

The pixel circuit according to embodiments of the present invention can be applied to an image scanner having an OLED pixel. In addition, the pixel circuit according to embodiments of the present invention may be applied to an image scanner having an OLED pixel or a touch screen having an OLED pixel.

Preferred embodiments of the present invention described above are disclosed for purposes of illustration, and those skilled in the art will be able to make various modifications, changes, and additions within the spirit and scope of the present invention. Additions should be considered to be within the scope of the following claims.

1 is a circuit diagram of a conventional AMOLED (Active Matrix Organic Light Emitting Diode) pixel circuit.

FIG. 2 is an operation timing diagram of the AMOLED pixel circuit of FIG. 1.

3A illustrates a pixel circuit having a light sensing function according to an embodiment of the present invention.

3B illustrates a pixel circuit according to another embodiment of the present invention.

3C is a circuit diagram illustrating a pixel circuit according to another exemplary embodiment of the present invention.

4 and 5 are conceptual views illustrating a case in which the pixel circuit of FIG. 3A operates in a display mode.

6 to 8 are conceptual diagrams for describing a case in which the pixel circuit of FIG. 3A operates in a sensing mode.

9A is a timing diagram illustrating a display mode and a sensing mode operation of the pixel circuit of FIG. 3A.

FIG. 9B is a timing diagram illustrating a display mode and a sensing mode operation of a pixel circuit implemented with the NMOS transistor of FIG. 3B.

FIG. 10 is a conceptual diagram illustrating a display operation and a sensing operation performed for each scan line of the pixel circuit of FIG. 3A.

11 and 12 are graphs showing simulation results of the pixel circuit of FIG. 3A, according to an exemplary embodiment. The sensing output current of the pixel circuit is represented by the vertical axis, and the optical leakage current I _PIM is represented by the horizontal axis.

13 is a block diagram illustrating a flat panel display having a light sensing function according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

10: light receiving element 20: second switching unit

30: first switching unit 40: organic light emitting diode (OLED) pixel unit

Claims (11)

In a pixel circuit of an organic light emitting diode (OLED) having a light sensing function coupled to a scan line and a data line, An organic light emitting diode (OLED) pixel unit configured to emit an organic light emitting diode (OLED) based on a current corresponding to a voltage of the image signal transmitted through the data line; A light receiving device configured to provide a forward bias voltage to the organic light emitting diode (OLED) pixel unit in a forward bias in response to a first control signal, and to flow a photo leakage current in a reverse bias; And An organic light emitting diode having a light sensing function, the first switching unit performing a readout operation from the OLED pixel unit to the data line in response to a second control signal; OLED) pixel circuit. The optical device of claim 1, further comprising a second switching unit electrically connecting the organic light emitting diode (OLED) pixel unit to the light receiving element in response to a fourth control signal in the sensing mode. Pixel circuit of organic light emitting diode (OLED) having a sensing function. The organic light emitting diode (OLED) pixel unit of claim 2, wherein the organic light emitting diode (OLED) pixel unit Organic light emitting diodes (OLED); A driving transistor configured to emit the organic light emitting diode OLED by providing a current corresponding to the voltage of the image signal provided through the data line to the organic light emitting diode OLED; A first switching element providing a voltage of the image signal to a control electrode of the driving transistor in response to a first scan line signal; A second switching element configured to operate the driving transistor in a diode connection structure in response to a second scan line signal; A first capacitor for storing a voltage of the image signal; A second capacitor configured to provide a voltage of the image signal to a control electrode of the driving transistor by a coupling effect; And And a third switching device coupled between the driving transistor and the organic light emitting diode (OLED) and switched in response to a third control signal. The light sensing function of claim 3, wherein the light emitting function of the organic light emitting diode is blocked by keeping the third control signal active while the sensing mode is operated to turn off the third switching device. Pixel circuit of organic light emitting diode (OLED). 4. The TFT of claim 3, wherein the first switching unit, the second switching unit, the first switching element, the second switching element, the third switching element, and the driving transistor are P-type TFTs. A pixel circuit of an organic light emitting diode (OLED) having a light sensing function, wherein the light receiving element is a pim (p-intrinsic-metal) diode. In a pixel circuit of an organic light emitting diode (OLED) having a light sensing function coupled to a scan line and a data line, An organic light emitting diode (OLED) coupled to the first power supply voltage; A first switching element coupled to the data line to provide a voltage of an image signal provided through the data line in response to a first scan line signal; A first capacitor having one end coupled to the first switching element and a second power supply voltage to store a voltage of the image signal; A second capacitor having one end coupled to one end of the first capacitor; And A control electrode is coupled to the other end of the second capacitor, and a first electrode is coupled to the second power supply voltage to provide a current corresponding to the voltage of the image signal provided through the data line to the organic light emitting diode OLED. A driving transistor for emitting the organic light emitting diode OLED; A second switching element coupled to a control electrode of the driving transistor and a second electrode of the driving transistor to operate the driving transistor in a diode-connected structure in response to the second scan line signal; A third switching element coupled between the second electrode of the driving transistor and the organic light emitting diode (OLED) and switched in response to a third control signal; A light receiving element that is forward biased or reversely reverse biased in response to the first control signal; A first switching unit coupled to the data line and the second electrode of the driving transistor to perform a read out operation in response to a second control signal in a sensing mode operation; And A second switching unit coupled between the other end of the second capacitor and the light receiving element to maintain a turn-on state in response to a fourth control signal when operating in a sensing mode; The pixel circuit of the organic light emitting diode (OLED) having a light sensing function comprising a. The TFT of claim 6, wherein the first switching unit, the second switching unit, the first switching element, the second switching element, the third switching element, and the driving transistor are P-type TFTs. A pixel circuit of an organic light emitting diode (OLED) having a light sensing function, wherein the light receiving element is a pim (p-intrinsic-metal) diode. A scan line transferring a scan line signal; A data line carrying an image signal; A scan driver to generate a scan line signal for driving the scan line; A data driver for driving the data line; And A pixel circuit of an organic light emitting diode (OLED) electrically coupled to the scan line and the data line and having a light sensing function, wherein the pixel circuit of the organic light emitting diode (OLED) An organic light emitting diode (OLED) pixel unit configured to emit an organic light emitting diode (OLED) based on a current corresponding to a voltage of the image signal transmitted through the data line; A light receiving device configured to provide a forward bias voltage to the organic light emitting diode (OLED) pixel unit in a forward bias in response to a first control signal, and to flow a photo leakage current in a reverse bias; And And a first switching unit configured to perform a readout operation from the organic light emitting diode (OLED) pixel unit to the data line in response to a second control signal during a sensing mode operation. The optical device of claim 8, further comprising a second switching unit electrically connecting the organic light emitting diode (OLED) pixel unit to the light receiving element in response to a fourth control signal when the sensing mode is operated. Display device having a sensing function. The method of claim 9, wherein the organic light emitting diode (OLED) pixel unit Organic light emitting diodes (OLED); A driving transistor configured to emit the organic light emitting diode OLED by providing a current corresponding to the voltage of the image signal provided through the data line to the organic light emitting diode OLED; A first switching element providing a voltage of the image signal to a control electrode of the driving transistor in response to a first scan line signal; A second switching element configured to operate the driving transistor in a diode connection structure in response to a second scan line signal; A first capacitor for storing a voltage of the image signal; A second capacitor configured to provide a voltage of the image signal to a control electrode of the driving transistor by a coupling effect; And And a third switching element coupled between the driving transistor and the organic light emitting diode (OLED) and switched in response to a third control signal. The TFT of claim 10, wherein the first switching unit, the second switching unit, the first switching element, the second switching element, the third switching element, and the driving transistor are P-type TFTs. And a light receiving element is a pim (p-intrinsic-metal) diode.

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