WO2008102996A1

WO2008102996A1 - Device for detecting pixel state of display element array substrate

Info

Publication number: WO2008102996A1
Application number: PCT/KR2008/001019
Authority: WO
Inventors: Jin Kook Jun; Hyung Il Jeon; Young Hoon Kim; Young Shik Park; Young Ryong Yoon; Myung Gi Seo
Original assignee: Okins Electronics Co., Ltd.
Priority date: 2007-02-22
Filing date: 2008-02-21
Publication date: 2008-08-28

Abstract

The present invention provides a detecting device detecting pixel state. The detecting device detecting pixel state may include a lower electrode, an optical-conductive layer, an upper electrode deposited in sequential, a charge collecting electrode formed on a surface of the upper electrode corresponding to a position of a object pixel, a capacitor electrically connected to an end portion of the charge collecting electrode, and a transistor electrically connected to the charge collecting electrode. According to the present invention, as well as a pixel defection, a line defection of a flat display device, a fine pixel defect such as a low-brightness point, a low- flickering point and a spot are easily detected, and the defected flat display device is prevented to proceed in a following process such as module assembling. Thus, a cost for assembling inferior goods may be reduced.

Description

DEVICE FOR DETECTING PIXEL STATE OF DISPLAY ELEMENT ARRAY SUBSTRATE

Technical Field

[1] The present invention is related to a device for detecting pixel state of a display element array substrate, and to a device for detecting pixel state of a display element array substrate to test electrical failure of a pixel substrate of a display device. Background Art

[2] In conventional times, after a thin film transistor ("TFT") liquid crystal display

("LCD") cell process is completed, an inspector lighten a backlight of a panel and inspects each pixel of the panel in eyes in a quality assurance.

[3] Thus, the inspector easily decides when a pixel failure or a line failure is shown dis- tinguishingly, but the panel defect caused by spots (mura) according to characteristics of the panel is hard to be detected by naked eyes.

[4] The inspector can not detect surely the panel defection according to the spots according to the characteristics of the panel in a conventional method, so that such defection is not detected.

[5] Moreover, the position of a failed pixel has to be detected and repaired by manual even when the inspector detects the failed pixel at the inspected panel by naked eyes.

[6] FIGS. 1 and 2 are cross-sectional views illustrating operating logics of polymer dispersed liquid crystal ("PDLC"), and an electrode 100, a dispersed liquid crystal 102, a reflection layer 104, a polymer medium 106 and a transparent electrode (ITO; indium-tin oxide) 108 are sequentially deposited.

[7] In the PDLC, a low polymer of a liquid crystal is dispersed into a high polymer, and a refraction difference between the high polymer and the liquid crystal is caused, and the refraction ratio is controlled by an intensity of an electrical field, and light trans- mis sivity is controlled, so that an alignment layer and a polarizer are not needed.

[8] When an electrical field is not applied to the electrodes 100 and 108 as illustrated in

FIG. 1, a small liquid crystal 102 drop is arranged at random. A light course is interfered by refraction between the liquid crystal 102 drop and the high polymer, thereby light scattered.

[9] When an electrical field is applied to the electrodes 100 and 108 as illustrated in

FIG. 2, the small liquid crystal 102 drop is arranged at a line, a refraction difference is reduced, and the light course is formed as a line, so that light passes through as one line, and the light is reflected by the reflection layer 104.

[10] FIG. 3 is a cross-sectional view illustrating an exemplary embodiment of the con- ventional detecting device for pixel state of a liquid crystal device array substrate. A mirrored pellicle 200, a liquid crystal 202, a transparent electrode (ITO on mylar) 204, an epoxy 206 and a glass substrate 208 are sequentially deposited.

[11] Such conventional detecting device for pixel state of the liquid crystal device applies the PDLC, and includes a mylar, which is an enhanced polyester film, and an ITO transparent electrode coated on the mylar.

[12] Moreover, a multi-layer dielectric substance thin film reflection layer 200, which reflects light having wavelength of only light source, is coated at the lowest layer, and is attached by the glass 208 and the epoxy 206 to support and adjust planarization and evenness.

[13]

[14]

[15] *FIG. 4 is a concept view illustrating an exemplary use of the conventional detecting device for pixel state of the liquid crystal device array substrate. The conventional detecting device for pixel state of the liquid crystal device array substrate includes an array substrate 300, normal pixels 302 and 306, a defected pixel 304, an electrical field 308, a detecting device for pixel state of a liquid crystal device array substrate 310, a power 312, a light source 314, a beam splitter 316, a telecentric lens 318, a charged-coupled device camera 320 and an image processor 322.

[16] Transmissivity characteristic of the PDLC is changed by an electrical field of an electro-optical method. With using the PDLC, the changes of an electro-optical characteristics is measured by a CCD camera, which is able to transfer the changes into electrical signals, and the electrical signals are image processed to detect an electrical defection.

[17] Such detection method is called as a voltage imaging. The embodiment in FIG. 3 uses the voltage imaging method. In FIG. 3, the power 312 is applied to the detecting device 310 and the array substrate 300, and a TFT formed at the array substrate 300 is driven, and the detecting device 310 is approached at a surface of the array substrate 300 by a distance of about 20 um.

[18] The voltage difference between a voltage applied to a pixel formed at the array substrate 300 and a voltage applied to the detecting device 310 makes an electrical field, and the voltage difference for the electrical field of the normal pixels 302 and 306 is different from the voltage difference for the electrical field of the defected pixel 304 having electrical defection.

[19] The voltage difference is formed differently from each other, and difference of the optical transmissivity of the PDLC is caused. Thus, light amounts passing through the beam splitter 316 according to the normal pixels 302 and 306 and the light amounts passing through the beam splitter 316 according to the defected pixel 304 are different from each other. The beam splitter 316 reflects light provided from the light source 314 toward the detecting device 310, and transmits light provided from the detecting device 310 toward the telecentric lens 318.

[20] The lights having different light amounts passing through the PDLC are reflects by the multi-layer dielectric thin film reflective layer 200, and are provided to the CCD camera 320 through the telecentric lens 318.

[21] The image processor 322 processes digital signals provided from the CCD camera

320 by a voltage image process, and detects an electrically defected pixel if the value of the digital signals are over a predetermined value of a program.

[22] In the conventional detecting device for the pixel state of the liquid crystal display array substrate, detecting sensitivity of the detecting device is bad for detecting an electrical defect of the device formed at the liquid crystal display array substrate. A gap between the array substrate and the detecting device is small in the conventional detecting device. The detecting device may be damaged by a particle on the surface of the liquid crystal array substrate.

[23] The conventional detecting device requires an optical system including the CCD camera, so that a size of the detecting device is limited.

[24] Since the optical is used as illustrated in FIG. 4, the signal is distorted and reduced by refraction, scattering and reduce of the light passing through the light source, and the equipments are expensive, and the effectiveness of the signal is bad because the detected signal is not read/out directly.

[25]

Disclosure of Invention Technical Problem

[26] The technical purpose of the present invention provides a detecting device for detecting pixel state of a display device array substrate, which detects an electrical defect of a device formed at a display device array substrate at high sensitivity.

[27] The another technical purpose of the present invention provides a detecting device for detecting pixel state of a flat display device by checking each brightness of a plurality of pixels formed at the flat display device and displaying at a screen, so that an inspector inspects the defect of the pixels through the screen.

[28]

Technical Solution

[29] The present invention may provide a detecting device detecting pixel state. The detecting device detecting pixel state may include a lower electrode, an optical- conductive layer, an upper electrode deposited in sequential, a charge collecting electrode formed on a surface of the upper electrode corresponding to a position of a object pixel, a capacitor electrically connected to an end portion of the charge collecting electrode, and a transistor electrically connected to the charge collecting electrode.

[30] The transistor may be a thin film transistor (TFT). The optical-conductive layer may include a-Se or poly-silicon. A drain electrode of the transistor may be electrically connected to the charge collecting electrode.

[31] In an exemplary embodiment of the present invention, the detecting device detecting pixel state includes a lower polarizer, a lower glass, a lower alignment liquid crystal, an upper alignment layer, a transparent electrode, an upper glass, an upper polarizer, a lower blocking layer, an optical-conductive layer, an upper blocking layer deposited in sequential, a charge collecting electrode formed on a surface of the upper blocking layer corresponding to a position of a object pixel, a capacitor electrically connected to an end portion of the charge collecting electrode, and a transistor electrically connected to the charge collecting electrode.

[32] The transistor may be a thin film transistor (TFT).

[33] The upper glass may be Eagle2000 0.5t glass.

[34] The transparent electrode may be ITO.

[35] The thickness of the transparent electrode may be 400 .

[36] The upper and lower alignment layer may be PΙ(Polyimide).

[37] The gap of the upper and lower glass may be 4 m.

[38] The liquid crystal may be TNLC.

[39] The optical-conductive layer may be a-Se.

[40] The thickness of the optical-conductive may be less than 50 m.

[41] The present invention provides a detecting device detecting pixel state including a pixel state detecting part. The device may include the pixel state detecting part receiving light emitted at a pixel formed in the flat display device, and outputting a signal corresponding to brightness of the light, an image processing part receiving the signal corresponding to the brightness of the light from the pixel state detecting part, and processing an image to form the image corresponding to the brightness of the light, and a displaying part receiving a image-processed signal provided from the image processing part, and displaying an image corresponding to the brightness of the light.

[42] The present invention stores the image-processed signal of the detecting object pixel as a raw data file. Later, the raw data is read out, and respective address information for defect pixel, defect line may be obtained from the image-processed data.

[43]

Advantageous Effects

[44] According to the present invention, as well as a pixel defection, a line defection of a flat display device, a fine pixel defect such as a low-brightness point, a low-flickering point and a spot are easily detected, and the defected flat display device is prevented to proceed in a following process such as module assembling. Thus, a cost for assembling inferior goods may be reduced.

[45] Moreover, an image processing part stores an image-processed signal of a detecting object pixel as a raw data file in a storage part. The raw data file is read out, respective address information of the defected pixel or the defected line is obtained from the image-processed data, so that the defected cell may be easily repaired.

[46] Damages of the detecting device by a particle on a surface may be preventable.

[47] The detecting device of the present invention may directly read out a signal using optical-electronic characteristic of the optical conductive material. Thus, a size of the detecting device may be manufactured larger, so that an inspecting time may be reduced.

[48] Since the equipment for inspecting pixel state of a display device array substrate, which applies the device for detecting pixel state of the display device array substrate, does not apply an optical system, signal distortion and signal reduce by light refraction, scattering and reduce by the light passing through the light course are not generated, and the equipment manufacture is simple and low-cost, and the detected signal is directly read/out, so that a signal effectiveness is better.

[49] [BRIEF DESCRIPTION FOR THE DRAWNGS]

[50] FIG. 1 and FIG. 2 are cross-sectional views showing a driving principle of a PDLC.

[51] FIG. 3 is a cross-sectional view illustrating a conventional detecting part for pixel state of a liquid crystal display device.

[52] FIG. 4 is a concept view showing a conventional detecting device for pixel state of a liquid crystal display device.

[53] FIG. 5 is a concept view illustrating a detecting device for pixel state of a flat display device in accordance with a first embodiment of the present invention.

[54] FIG. 6 is a concept view illustrating a detecting part for pixel state in accordance with the first embodiment of the present invention.

[55] FIG. 7 is a plan view showing a screen of a displaying part of the detecting device for pixel state in accordance with the first embodiment of the present invention.

[56] FIG. 8 is a detecting device for pixel state of a display device array substrate in accordance with a second embodiment of the present invention.

[57] FIG. 9 and FIG. 10 are views illustrating a driving principle of the detecting device for pixel state of the display device array substrate in accordance with the second embodiment of the present invention.

[58]

[59] < Descriptions for main references in drawings > [60] 10 : upper glass 12 : transparent electrode

[61] 14 : lower glass 16 : upper alignment layer

[62] 18 : lower alignment layer20 : liquid crystal

[63] 22, 24 : sealant26 : upper polarizer

[64] 28 : lower polarizer30 : lower blocking layer

[65] 32 : optical-conductive Iayer33 : upper blocking layer

[66] 34, 36 : first, second charge collecting electrode

[67]

[68] *38, 40 : first, second charge amplifier

[69] 50 : array substrate

[70] 110 : backlightl 12 : flat display device

[71] 114, 118 : normal pixell lό : defected pixel

[72] 120 : pixel state detecting partl22 : image processing part

[73] 124 : storage partl26 : displaying part

[74] 130 : lower electrode 132 : optical-conductive layer

[75] 134 : upper electrode

[76] 136, 138 : first, second charge collecting electrode

[77] Cl, C2 : first, second capacitorQl, Q2 : first, second TFT

[78]

Best Mode for Carrying Out the Invention

[79] FIG. 5 is a concept view illustrating a detecting device for pixel state of a flat display device of the present invention. The detecting device includes a backlight 10, a flat display device 12, normal pixels 14, 18, a defected pixel 16, a detecting part for pixel state 20, an image processing part 22, a storage part 24 and a displaying part 26.

[80] FIG. 6 is a concept view illustrating a detecting part for pixel state of the present invention.

[81] Referring to FIG. 6, a direct-current voltage is applied to the optical-conductive layer 32 in the detecting part for pixel state 20 through the upper and lower electrodes 30, 34. The direct-current voltage may be changed, and a proper alternative-current voltage may be applied.

[82] An optical-conductive effect is defined by that a carrier density in a semiconductor is increased and conductivity is increased. By the optical-conductive effect, the semiconductor is close to an insulation material in a dark place, and the semiconductor has conductivity when light incomes. The optical-conductive layer 32 may include CdS, PbS, TIPb2, HgI2, PbI2, a-Se and poly-silicon.

[83] The backlight 10 is lightened, and uniform light is supplied to a lower portion of the flat display device 12 by the backlight 10. In the present invention, the TFT LCD cell arranged as a matrix shape at the flat display device 12 is an example as an inspecting object. A flat display device applying an OLED (Organic Light Emitting Diode) may be the inspecting object. Moreover, a flat display device applying PDP (Plasma Display Panel) cell may be the inspecting object.

[84] A condition for detecting pixel state of the flat display device 12 is set, and pixels

14, 16, 18 formed at the flat display device 12 output light toward the detecting part for pixel stats 20 in accordance with respective driving of the liquid crystals. The pixels 14, 18 emit normal light toward the detecting part for pixel state 20 when the liquid crystals corresponding to the pixels 14, 18 drive normally. However, the pixel 16 emits dark light toward the detecting part for pixel state 20 for abnormal example when the liquid crystal corresponding to the pixel 16 does not drive normally. According to whether the liquid crystals corresponding to each of the pixels 14, 16, 18 drive normally, each of the pixels 14, 16, 18 may be divided into normal pixels 14, 18 and a defected pixel 16.

[85] The optical-conductive layer 32 in the detecting part for pixel state 20 has different electron movement for each part corresponding to light brightness of the each of the pixels 14, 16, 18. The electron movement, to which the bright light (the normal pixel area) is provided, is increased. The electron movement, to which the dark light (the defected pixel area) is provided, is reduced. Electrons are formed by an applied voltage at the optical-conductive layer 32, the electrons are arranged according to each brightness of light emitted from each of the pixels 14, 16, 18 to the optical-conductive layer. Thus, more electrons are arranged at which light is brighter.

[86] The first, second charge collecting electrodes 36, 38 are formed at a surface of the upper electrode 34 to correspond to a position of the detecting object pixel. The first and second charge collecting electrode 36, 38 collect corresponding charges, and provide the charges to the first, second capacitors Cl, C2.

[87] The first, second capacitors Cl, C2 accumulate the charges provided from the first, second charge collecting electrodes 36, 38.

[88] Drain electrodes of the first, second TFT Ql, Q2 are electrically connected to the first, second charge collecting electrodes 36, 38. A channel is formed between the drain electrode and the source electrode as a driving signal is applied to a gate. The charges accumulated at the first, second capacitors C 1 , C2 are provided to the image processing part 22, respectively. Bigger electrical current is flowed as the accumulated charges are more.

[89] The image processing part 22 receives signals corresponding the light brightness from each of the source electrodes of the first, second TFT Ql, Q2 in the detecting part for pixel state 20. The image processing part 22 processes the signal to form an image corresponding to the light brightness. The image processing part 22 provides the image-processed signal to the displaying part 26.

[90] The displaying part 26 receives the image-processed signal provided from the image processing part 22. The displaying part 26 displays the image corresponding to the light brightness to a screen such as a TFT LCD monitor as illustrated in FIG. 7. For example, a pixel defect, a line defect, and a spot are illustrated in FIG. 7.

[91] The storage part 24 receives and stores the image-processed signal provided from the image processing part 22. The image processing part 22 stores the image-processed signal as a raw data file at the storage part 24. A raw data may easily read out. For example, address information of the defected pixel and the defected line may be obtained from the image-processed data, and the defected cell may be repaired.

[92] FIG. 8 is a detecting device for pixel state of a display device array substrate in accordance with a second embodiment of the present invention.

[93] A transparent electrode (Indium- Tin Oxide; ITO) is deposited at 400 on a lower surface of the upper glass 111 (Eagle 2000 0.5t glass).

[94] A PI provides an alignment force to a liquid crystal 120 at an area except for a portion of both sides of a surface of the transparent electrode 113 and an upper surface of the lower glass 114. The PI is coated to form the upper and the lower alignment layers 116 and 118. The liquid crystal 120 will be sealed at portions of the areas of both sides.

[95] The upper and the lower glasses 111, 114 are adhered at a cell gap of 4 m to face to the upper and the lower alignment layers 116, 118, respectively.

[96] The liquid crystal 120 is injected between the upper and the lower alignment layers

116, 118. The liquid crystal 120 applies a TNLC, which drives with a low voltage.

[97] The lower glass 114 is slimmed as slight as possible. A slimming method includes a wet etching, a lapping and a polishing. The lapping and the polishing are applied to the present embodiment. The slimming of the glass 144 is important to be as slight as possible, but the lower glass is slimmed at a thickness of about 80 m because of damage of the lower glass 114 and a manufacturing deviation of the lower glass 114.

[98] An upper and a lower polarizes 126, 128 are coated to be parallel to each other at an upper surface of the upper glass 111 and a lower surface of the lower glass 114 (Normally Black Mode). The coating of the lower polarizer 128 for detecting a signal may be as slight as possible.

[99] A lower blocking layer 130, an optical-conductive layer (a-Se, thickness of less than 50 m ) 132 and an upper blocking layer 133 are formed sequentially at the upper surface of upper polarizer 126. The a-Se is sensitive to a visible light, and electron-hole pairs are effectively generated. An "a" of the a-Se means "amorphous".

[100] A plurality of charge collecting electrodes 134, 136 are formed selectively at an upper surface of the upper blocking layer 133 to respectively correspond to positions of a plurality of detecting object pixels.

[101] A plurality of capacitors Cl, C2 is electrically connected to a plurality of the charge collecting electrodes 134, 136. A plurality of TFTs Ql, Q2 electrically connected to each drain electrode is formed at the charge collecting electrodes 134, 136. A plurality of the charge collecting electrode 134, 136 collects a hole generated at the optical- conductive layer 132. A plurality of the charge collecting electrodes 134, 136 is formed large to collect holes as much as possible.

[102] For example, a plurality of charge amplifiers 138, 140 may be formed, and the charge amplifiers 138, 140 are electrically connected to source electrode of the TFTs Ql, Q2 via input terminals of the charge amplifiers 138, 140.

[103] FIG. 9 and FIG. 10 are views illustrating a driving principle of the detecting device for pixel state of the display device array substrate in FIG. 8.

[104] As a driving principle of a TNLC (Twisted- Nematic Liquid Crystal), a glass plate is arranged in one axis along a face of the glass plate, and the glass plates cross to each other in a perpendicular direction. When the liquid crystal is inserted between the two glass plates, an arrangement of the liquid crystal molecule is twisted. When a voltage is applied to the liquid crystal, the liquid crystal molecule is arranged in a direction of an electrical field.

[105] Polarizer axes of the polarizing plates are arranged in perpendicular to each other at both faces of the liquid crystal as illustrated in FIG. 9. The polarized light is twisted along a molecule axis of the liquid crystal, and passes through the liquid crystal when the voltage is off. The polarized light does not pass through the liquid crystal when the voltage is on.

[106] However, when the polarizing axes of the polarizing plates are arranged in parallel to each other, the light does not pass through in a voltage-off, and the light pass through in a voltage-on.

[107] Such principle controls light amount by controlling an intensity of the electrical field.

[108] FIG. 10 is a view illustrating a light absorption of the optical-conductive material

(a-Se) 404 in the driving principle of the detecting device for detecting the display device array substrate illustrated in FIG. 8. This means effectiveness for generating electron-hole pair is greater in a visible-light wavelength.

[109]

[110] *The driving of the detecting device for detecting pixel states of the present invention is as follows.

[I l l] A circuit of the array substrate 150, which is detected for detecting a defect pixel, is driven to apply a signal to each pixel 152 and 154. A backlight (not shown) is driven. The backlight is disposed under the array substrate 150 and emits uniform light. [112]

[113] *An electrical field is formed between pixel electrodes of the array substrate 150 by applying a pulse wave 100 [V] through a transparent electrode 112 to a liquid crystal 120. In order to prevent from deterioration of the liquid crystal 120, the pulse wave, which reverses polarity at a constant period, is used. Different voltages are formed at a normal pixel 152 and a defect pixel 154, and voltage difference from an upper portion 100 [V] of the liquid crystal 120 is different from each other. A twist of the liquid crystal 120 according to the electrical field is changed, so that uniform light brightness emitted through the liquid crystal 120 into each areas of the defect pixel 154 and the normal pixel 152 become different from each other.

[114] The incident lights having different brightness, which are toward the light conductive layer 132, form different electron hole pairs at each area of the light conductive layer 132. The different electron hole pairs are separated from each other by high voltage applied to the light conductive layer 132, and each hole is moved toward the first, the second charge collecting electrodes 134 and 136 and collected, and the holes are accumulated at each capacitor Cl and C2, respectively. Each hole accumulated at each capacitor Cl and C2 is read out along a data line through channels, which are formed at each TFT Ql and Ql when gate electrodes of each TFT Ql and Q2 are turned on.

[115] The pulse wave signals, which are read out corresponding to the normal pixel 152 and the defect pixel 152, become to have differences. Since the signals are small analog signals, the signals are amplified and converted into digital signals by each charge amplifiers 138 and 140 and A/D (Analog/Digital) converter (not shown). The digital signal is image-processed, so that the defect pixel 154 of the array substrate 150 is detected.

[116] The detecting device for pixel state of the array substrate of display device of the present invention detects electrical failure of each devices of the TFT substrate in manufacturing process of the active matrix liquid crystal display device, and also detects electrical failure of the devices of a diode substrate in the manufacturing process of the active matrix liquid crystal display device. Thus, the electrical failures for each device on the substrate in the active matrix liquid crystal display device may be detected.

[117]

[118]

[119]

[120]

[121]

[122]

Claims

[1] A detecting device detecting pixel state comprising: a lower electrode, an optical-conductive layer, an upper electrode deposited in sequential; a charge collecting electrode formed on a surface of the upper electrode corresponding to a position of an object pixel; a capacitor electrically connected to an end portion of the charge collecting electr ode; and a transistor electrically connected to the charge collecting electrode. [2] In claim 1, the detecting device of the flat display device, wherein a drain electrode of the transistor is electrically connected to the charge collecting electrode. [3] A detecting device detecting pixel state comprising: a lower polarizer, a lower glass, a lower alignment liquid crystal, an upper alignment layer, a transparent electrode, an upper glass, an upper polarizer, a lower blocking layer, an optical-conductive layer, an upper blocking layer deposited in sequential; a charge collecting electrode formed on a surface of the upper blocking layer corresponding to a position of an object pixel; a capacitor electrically connected to an end portion of the charge collecting electrode; and a transistor electrically connected to the charge collecting electrode. [4] In claim 3, the detecting device of the flat display device further comprising a charge amplifier, an input terminal of the charge amplifier electrically connected to a source electrode of the transistor. [5] In claim 3 or claim 4, the detecting device of the flat display device wherein the transparent electrode comprises an ITO. [6] In claim 3 or claim 4, the detecting device of the flat display device wherein the liquid crystal comprises a TNLC. [7] In claim 3 or claim 4, the detecting device of the flat display device wherein the optical-conductive layer comprises an a-Se. [8] As a detecting device of a flat display device, a pixel state detecting part receiving light emitted at a pixel formed in the flat display device, and outputting a signal corresponding to brightness of the light; an image processing part receiving the signal corresponding to the brightness of the light from the pixel state detecting part, and processing an image to form the image corresponding to the brightness of the light; and a displaying part receiving a image-processed signal provided from the image processing part, and displaying an image corresponding to the brightness of the light. [9] In claim 8, the detecting device of the flat display device further comprising a storage part saving the image-processed signal. [10] In claim 8 or claim 9, the detecting device of the flat display device wherein the pixel state detecting part comprising: a lower electrode, an optical-conductive layer, an upper electrode deposited in sequential; a charge collecting electrode formed on a surface of the upper electrode corresponding to a position of a object pixel; a capacitor electrically connected to an end portion of the charge collecting electrode; and a transistor electrically connected to the charge collecting electrode. [11] In claim 10, the detecting device of the flat display device wherein a drain electrode of the transistor is electrically connected to the charge collecting electrode. [12] In claim 8 or claim 9, the detecting device of the flat display device wherein the optical-conductive layer comprises an a-Se. [13] In claim 8 or claim 9, the detecting device of the flat display device wherein the optical-conductive layer comprises poly-silicon.