JP2005269273A - Photoelectric conversion amount detecting method, photoelectric converter, and information output apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric converter having a simple configuration, capable of detecting photoelectric conversion amount with high accuracy. <P>SOLUTION: A sensor board 20 as a pixel section is provided with an auxiliary capacitor 17 for charging electric charges produced from a photosensitive semiconductor layer 12, receiving light of a TFT 7 in a nonconductive state and connected to the drain electrode D of the TFT 7. A detection IC 25 as a detection section is provided with an integrating amplifier 33 and a feedback capacitor 39 for detecting a photoelectric conversion amount on the basis of electric charges charged in the auxiliary capacitor 17. The TFT 7 is turned on, before the light reception and once releases the electric charges by the operation of the integration amplifier 33. Then, when light is received, while the TFT 7 is nonconductive, the auxiliary capacitor 17 charges the generated electric charges and the detection IC 25 brings the charged electric charges to the feedback capacitor 39, to obtain the photoelectric conversion amount. Thus, the photoelectric conversion amount can be detected with high accuracy by using a simple configuration. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a photoelectric conversion amount detection method for detecting a photoelectric conversion amount of a photoelectric conversion element, a photoelectric conversion device that realizes the method, and an information output device including the device.

  2. Description of the Related Art Conventionally, when inputting an image into a personal computer (PC), a facsimile machine or the like, an image reading apparatus (for example, a scanner) that can read a document as an image is often used.

  There are various types of image reading apparatuses. Among them is a one-dimensional image sensor. When reading an image using this one-dimensional image sensor, it is necessary to scan the document by moving the one-dimensional image sensor relative to the document or by moving the document relative to the one-dimensional image sensor. There is.

  Accordingly, since it is necessary to scan the original by mechanically moving the one-dimensional image sensor or the original, the image reading speed is slow, and downsizing and weight reduction of the apparatus are limited.

  Various types of contact-type two-dimensional image sensors (image reading devices) that do not require mechanical scanning have been proposed. The two-dimensional image sensor is used in a flatbed scanner or the like and can read the entire original image at a time.

  Some two-dimensional image sensors use thin film transistors (TFTs), and many of them are pixel selection transistors (switching elements; thin film transistors, etc.) and photosensors (photodetection elements; phototransistors, photodiodes, etc.). ) And 1 pixel are formed, and each pixel is arranged in a two-dimensional matrix. Note that the pixel selection transistor is provided to prevent crosstalk.

  Generally, in the two-dimensional image sensor, charges generated according to the amount of light applied to each photosensor are accumulated in each pixel, and the pixel selection transistor is electronically scanned to sequentially turn on the charge amount from each pixel. Image information is obtained by reading.

  FIG. 12 is a schematic explanatory diagram of a circuit of a conventional photosensor. The photosensor 100 is roughly divided into a pixel unit 101 and a detection unit 102 in terms of configuration. The pixel unit 101 and the detection unit 102 illustrated in FIG. 12 correspond to one pixel. Actually, however, the pixel unit 101 is arranged in a matrix for the number of pixels of the photosensor, and the detection unit 102 is configured in a matrix. Are arranged in a peripheral portion of the pixel portion 101 arranged in the array.

In the pixel portion 101, the photodiode 103 is irradiated with light, charges generated thereby are accumulated in the auxiliary capacitor 104, and passed through a thin film transistor 106 (hereinafter referred to as a TFT 106) as a switching element that is turned on by application of a gate voltage 105. Accumulated in the auxiliary capacitor 107. The auxiliary capacitor 107 has a role of converting the charge accumulated in the auxiliary capacitor 104 into a voltage.
In the detection unit 102, the integrating amplifier 108 obtains the photoelectric conversion amount by the photodiode 103 based on the voltage applied to the auxiliary capacitor 107.

  As shown in the figure, the auxiliary capacitors (charge storage capacitors) 104 and 107 are connected to both the source side and the drain side of the TFT 102. In addition, the photodiode 103 that emits light to generate a photocurrent is disposed outside the TFT 106 (Non-patent Document 1).

For the purpose of increasing the density of pixels, proposals have been made to integrate a pixel selection transistor and a photosensor. That is, the pixel area is reduced by providing the photosensor itself with a photosensor function and a pixel selection function (Patent Documents 1 and 2).
Japanese Laid-Open Patent Publication No. Hei 2-27963636 (released on October 2, 1990) JP 6-3019632 A (published on May 13, 1994) Television Society Technical Report Vol. 17, No16, pp25-30 (released March 4, 1993)

  However, a contact-type two-dimensional image sensor that does not require mechanical scanning can be read at high speed and can be reduced in weight and thickness. Therefore, many proposals have been made, but it has not yet been put into practical use.

  The main factor is the complexity of the pixel structure and array structure provided in the two-dimensional image sensor. That is, the pixel structure and the array structure of the two-dimensional image sensor are more complicated than the TFT array used in the active matrix type liquid crystal display currently mass-produced.

Conventionally, the amount of photoelectric conversion was detected by detecting the current value and voltage value, but with this method it is very difficult to accumulate current and voltage, and the circuit configuration for measuring the current value and voltage value Becomes complicated. Specifically, as shown in FIG. 12, in order to obtain the photoelectric conversion amount, it is necessary to convert the electric charge stored in the auxiliary capacitor 104 into a voltage. It is necessary to provide auxiliary capacitors 104 and 107 on the side. As a result, since the two auxiliary capacitors 104 and 107 must be provided in the pixel portion 101, the structure of the pixel portion 101 becomes complicated.
For this reason, the manufacturing process for forming the photosensor 100 increases, the pixel area further increases, and it is difficult to increase the resolution.

  In addition, a structure in which the photosensor itself has a photosensor function and a pixel selection function (for example, a combination of an inverted staggered thin film transistor and a coplanar thin film transistor with a single semiconductor layer) has a complicated structure and is manufactured. There was a problem that the process became complicated.

  Furthermore, when the structure of the two-dimensional image sensor is simplified, there is a problem that a method for obtaining the photoelectric conversion amount becomes complicated and it is difficult to obtain the photoelectric conversion amount with high accuracy.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to enable high resolution while simplifying the pixel structure constituting the photosensor and to simplify the manufacturing process. Another object is to provide a photoelectric conversion amount detection method, a photoelectric conversion device, and an information output device.

  In order to solve the above problems, a photoelectric conversion amount detection method of the present invention is a photoelectric conversion amount detection method for detecting a photoelectric conversion amount of a photoelectric conversion element including a thin film transistor having a photosensitive semiconductor layer. The charge of the auxiliary capacitor connected to is opened before light reception, and the thin film transistor is turned off to charge the auxiliary capacitor with the charge generated when the photosensitive semiconductor layer receives the light. And a photoelectric conversion amount detection step of detecting the photoelectric conversion amount based on the charge of the auxiliary capacitor after the charging step.

  According to the above configuration, when the photosensitive semiconductor layer of the thin film transistor that is in a non-conductive state receives light, a drain current corresponding to the off-resistance of the thin film transistor flows between the drain electrode and the source electrode of the thin film transistor. The auxiliary capacitor connected to the drain electrode of the thin film transistor is charged with a charge corresponding to the generated drain current. The charge charged here is equal to the amount of drain current (photocurrent) (hereinafter referred to as photoelectric conversion amount).

  Therefore, if the charge of the auxiliary capacitor is released and set to 0 before receiving light as in the charging step of the present invention, only the charge generated by receiving light is charged in the auxiliary capacitor. Therefore, in the photoelectric conversion amount detection step, the photoelectric conversion amount can be accurately detected based on the electric charge charged in the auxiliary capacitor.

  Further, since the photoelectric conversion amount can be detected by detecting the charge charged in the auxiliary capacitor in this way, it is only necessary to provide one auxiliary capacitor for accumulating the charge on the drain side of the thin film transistor. Therefore, the circuit structure for detecting the photoelectric conversion amount can be simplified. This effect is remarkable when compared with the case where, for example, the photocurrent itself generated during light irradiation is detected.

  In addition, since the auxiliary capacitor is connected to the drain electrode of the thin film transistor, it can be manufactured by using a thin film transistor manufacturing process.

  In this manner, by simplifying the configuration of the photoelectric conversion element, the photoelectric conversion element can be reduced, and the photosensor itself including the photoelectric conversion element can be reduced. Further, since the pixel structure in which the photoelectric conversion elements are arranged one-dimensionally or two-dimensionally can be reduced, high resolution can be achieved by reducing the pixels.

  In order to solve the above problems, a photoelectric conversion device of the present invention includes a pixel portion in which photoelectric conversion elements including a thin film transistor having a photosensitive semiconductor layer are arranged one-dimensionally or two-dimensionally, and a photoelectric conversion element of the photoelectric conversion element. In the photoelectric conversion device in which the detection unit for detecting the conversion amount is provided outside the pixel unit, the pixel unit is charged with electric charges generated when the photosensitive semiconductor layer of the thin film transistor in the non-conductive state receives light. An auxiliary capacitor is provided connected to the drain electrode of the thin film transistor, and the detection unit is provided with a photoelectric conversion amount detection means for detecting the photoelectric conversion amount based on the charge charged in the auxiliary capacitor. It is characterized by being.

  The photoelectric conversion device used in the present invention is included in light from the photoelectric conversion amount of each photoelectric conversion element when light is irradiated to a pixel portion in which the photoelectric conversion elements are arranged one-dimensionally or two-dimensionally. Image information is acquired. The thin film transistor included in the photoelectric conversion element has both a function as a switch for selecting a photoelectric conversion element for obtaining a photoelectric conversion amount and a photoelectric conversion function by including a photosensitive semiconductor layer. This point contributes to downsizing of the photoelectric conversion element.

  In addition, in addition to the thin film transistor having the photosensitive semiconductor layer, the pixel portion only has an auxiliary capacitor for charging the charge generated when the photosensitive semiconductor layer receives light. Therefore, the structure of the pixel portion can be simplified. In addition, since the auxiliary capacitor is connected to the drain electrode of the thin film transistor, a photosensor can be manufactured using a manufacturing process of the thin film transistor.

  Therefore, the configuration of the photoelectric conversion device of the present invention can simplify the manufacturing process. Further, the fact that the structure of the pixel portion can be simplified and the effect of reducing the size and increasing the resolution of the photosensor provided with the photoelectric conversion element is as described above for the photoelectric conversion amount detection method.

  The photoelectric conversion device of the present invention may be provided outside the pixel portion with an opening means for releasing the charge of the auxiliary capacitor in advance in preparation for the photosensitive semiconductor layer to receive light.

  According to the above configuration, when the photosensitive semiconductor layer of the thin film transistor that is in a non-conductive state receives light, a drain current corresponding to the off-resistance of the thin film transistor flows between the drain electrode and the source electrode of the thin film transistor. The auxiliary capacitor connected to the drain electrode of the thin film transistor is charged with a charge corresponding to the generated drain current. The charge charged here is equal to the amount of drain current (photocurrent) (hereinafter referred to as photoelectric conversion amount).

  Therefore, if the charge of the auxiliary capacitor is opened in advance and set to 0 in preparation for light reception by the opening means, only the charge generated by the light reception is charged in the auxiliary capacitor. Therefore, the photoelectric conversion amount detection means can accurately detect the photoelectric conversion amount based on the charge charged in the auxiliary capacitor.

  Further, since the opening means is provided outside the pixel portion, the structure of the pixel portion is not complicated.

  Furthermore, since the charge related to the previous detection information does not remain by releasing the charge, an appropriate photoelectric conversion amount can be detected even if the detection operation is repeatedly performed. That is, there is an effect that it becomes possible to perform a repetitive operation (detection of photoelectric conversion amount).

  In the photoelectric conversion device of the present invention, a potential difference generating means for generating a potential difference between the source electrode and the drain electrode of the thin film transistor when the photosensitive semiconductor layer receives light may be provided outside the pixel portion.

  After the thin film transistor is turned off, a potential difference is generated between the drain electrode and the source electrode of the thin film transistor by the potential difference generating means. At this time, when the photosensitive semiconductor layer of the thin film transistor which has been turned off receives light, a drain current flows between the drain electrode and the source electrode of the thin film transistor, and charge according to the amount of received light is reliably charged to the auxiliary capacitor. be able to.

  In addition, since the potential difference generating means is provided outside the pixel portion, the structure of the pixel portion is not complicated.

  In the photoelectric conversion device of the present invention, the potential difference generating means generates a potential difference by applying a voltage to an electrode opposite to the electrode connected to the drain electrode of the thin film transistor among the electrodes constituting the auxiliary capacitor. The 1st voltage application means to make may be provided.

  In this case, since the charge is charged by applying a voltage to the electrode directly connected to the auxiliary capacitor by the first voltage applying means, the amount of charge filling the auxiliary capacitor depending on the magnitude of the applied voltage. It becomes easy to adjust. As a result, the amount of charge accumulated by photoelectric conversion can be accurately detected, so that the detection accuracy of the photoelectric conversion amount can be improved.

  In the photoelectric conversion device of the present invention, the potential difference generating means may include second voltage applying means for generating the potential difference by changing the voltage of the source electrode of the thin film transistor.

  In addition, the potential difference generating means applies first voltage applying means for applying a voltage to an electrode on the opposite side to the electrode connected to the drain electrode of the thin film transistor among the electrodes constituting the auxiliary capacitor, and the source electrode of the thin film transistor Second voltage applying means for changing the voltage of the first voltage applying means, and the potential difference may be generated by the cooperation of the first voltage applying means and the second voltage applying means.

  In the photoelectric conversion device of the present invention, a driving circuit for controlling on / off of the thin film transistor is further provided outside the pixel portion, and the photoelectric conversion amount detecting unit is configured to detect the above when the driving circuit turns on the thin film transistor. A capacitor that temporarily captures the charge accumulated in the auxiliary capacitor; and a detection circuit that detects the photoelectric conversion amount based on the charge of the capacitor. The detection circuit and the capacitor also serve as the opening means. It may be a configuration.

  According to the above configuration, when the photosensitive semiconductor layer receives light, the driving circuit can turn off the thin film transistor to be in the non-conductive state. Further, when the driving circuit turns on the thin film transistor while the charge is charged in the auxiliary capacitor, the charge of the auxiliary capacitor can be captured by the capacitor of the photoelectric conversion amount detecting means. A detection circuit detects the photoelectric conversion amount based on the trapped charges.

  On the other hand, since the detection circuit and the capacitor also serve as the opening means, if the driving circuit turns on the thin film transistor before the photosensitive semiconductor layer receives light, the charge remaining in the auxiliary capacitor is photoelectrically converted. The capacity of the conversion amount detecting means can be captured. Therefore, the charge of the auxiliary capacitor can be set to 0 when receiving light.

  In addition, the configuration of the photoelectric conversion device can be simplified by having the constituent elements of the photoelectric conversion amount detection means also serve as the opening means.

  In the photoelectric conversion device of the present invention, a driving circuit that causes the thin film transistor during light reception to be in the non-conductive state by applying a negative voltage to the gate electrode of the thin film transistor may be provided outside the pixel portion.

  When the thin film transistor is irradiated with light, a photocurrent is induced in the photosensitive semiconductor layer, and the number of electron holes induced by the irradiation light between the source electrode and the drain electrode, that is, according to the amount of irradiation light. A drain current flows. Further, the drain current is extremely small when light is not irradiated. Further, the drain current during light irradiation and the drain current during non-light irradiation both decrease as the negative voltage is increased in the gate electrode, and eventually become saturated.

  Therefore, the difference between the drain current at the time of light irradiation and the drain current at the time of no light irradiation also increases as the negative voltage is increased at the gate electrode, and eventually becomes saturated.

  After all, when a negative voltage is applied to the gate electrode of the thin film transistor and the drain current during light irradiation is accumulated for a predetermined time, the difference becomes large when the photoelectric conversion amount due to the accumulation of drain current during non-light irradiation is used as a reference. can do. Thereby, a photoelectric conversion device having a large dynamic range can be obtained.

  The photoelectric conversion device of the present invention further includes a light source that emits light that includes image information received by the photosensitive semiconductor layer, and a period during which the photoelectric conversion amount detection unit detects the photoelectric conversion amount. And control means for stopping the light emission of the light source.

  According to the above configuration, the control unit stops the light emission of the light source while detecting the photoelectric conversion amount of the photoelectric conversion element, so that the photoelectric conversion elements arranged one-dimensionally or two-dimensionally receive light. There is nothing.

  Thereby, in a photoelectric conversion element other than the photoelectric conversion element that is the detection target of the photoelectric conversion amount detection means, it is possible to prevent a phenomenon in which the off-resistance of the thin film transistor decreases due to light reception and a leak current is generated. Therefore, even if the configuration in which the source electrodes of the plurality of thin film transistors arranged one-dimensionally or two-dimensionally are connected to the photoelectric conversion amount detection means, the leakage current is not detected. Misdetection of the photoelectric conversion amount can be eliminated.

  An information output device of the present invention includes the above-described photoelectric conversion device, and generates and outputs a signal corresponding to image information included in light irradiated on the photoelectric conversion device based on a photoelectric conversion amount detected by the photoelectric conversion device. It is characterized by doing.

  Thereby, it is possible to provide an information output device having the above-described various effects (miniaturization, simplification of the manufacturing process, high resolution, etc.) obtained by the configuration of the photoelectric conversion device. The information output device includes a line sensor, a two-dimensional image sensor, a scanner, and the like that output image information to various information processing devices such as a personal computer, a facsimile device, and an image forming device.

  According to the photoelectric conversion amount detection method of the present invention, the charge of the auxiliary capacitor connected to the drain electrode of the thin film transistor having the photosensitive semiconductor layer is released before receiving light, and the thin film transistor is made non-conductive to make the photosensitive semiconductor A charging step of charging the auxiliary capacitor with a charge generated when the layer receives the light, and a photoelectric conversion amount detecting step of detecting the photoelectric conversion amount based on the charge of the auxiliary capacitor after the charging step; It is equipped with.

  As a result, the charge of the auxiliary capacitor is released and set to 0 before the light is received, so that only the charge generated by the light reception is charged in the auxiliary capacitor. Therefore, in the photoelectric conversion amount detection step, the photoelectric conversion amount can be accurately detected based on the electric charge charged in the auxiliary capacitor.

  Further, since the photoelectric conversion amount can be detected by detecting the charge charged in the auxiliary capacitor in this way, it is only necessary to provide one auxiliary capacitor for accumulating the charge on the drain side of the thin film transistor. Therefore, the circuit structure for detecting the photoelectric conversion amount can be simplified.

  In addition, since the auxiliary capacitor is connected to the drain electrode of the thin film transistor, it can be manufactured by using a thin film transistor manufacturing process.

  In this manner, by simplifying the configuration of the photoelectric conversion element, the photoelectric conversion element can be reduced, and the photosensor itself including the photoelectric conversion element can be reduced. Further, since the pixel structure in which the photoelectric conversion elements are arranged one-dimensionally or two-dimensionally can be reduced, high resolution can be achieved by reducing the pixels.

  The photoelectric conversion device of the present invention includes a pixel unit in which photoelectric conversion elements including a thin film transistor having a photosensitive semiconductor layer are arranged one-dimensionally or two-dimensionally, and a detection unit that detects the photoelectric conversion amount of the photoelectric conversion element. In the photoelectric conversion device provided outside the pixel portion, the pixel portion includes an auxiliary capacitor that charges a charge generated when the photosensitive semiconductor layer of the thin film transistor in a non-conductive state receives light. The detection unit is provided with a photoelectric conversion amount detection unit that detects the photoelectric conversion amount based on the electric charge charged in the auxiliary capacitor.

  As a result, in addition to the thin film transistor provided with the photosensitive semiconductor layer, the pixel portion only needs to be provided with an auxiliary capacitor for charging the charge generated when the photosensitive semiconductor layer receives light. Therefore, the structure of the pixel portion can be simplified. Further, since the structure of the pixel portion is the same as that of the display TFT panel, a photosensor can be manufactured by using a display TFT panel manufacturing process.

  Therefore, the configuration of the photoelectric conversion device of the present invention can simplify the manufacturing process. Furthermore, as already described with respect to the photoelectric conversion amount detection method, by simplifying the structure of the pixel portion, it is possible to obtain the effect of downsizing and increasing the resolution of the photosensor including the photoelectric conversion element.

  Note that since the auxiliary capacitor is connected to the drain electrode of the thin film transistor, a photosensor can be manufactured using a manufacturing process of the thin film transistor.

[Embodiment 1]
An embodiment of the present invention will be described with reference to FIGS. 1 to 6 as follows. The photoelectric conversion device of the present invention can be incorporated into a two-dimensional image sensor (information output device) by two-dimensionally arranging photoelectric conversion elements (photosensors) described later. The two-dimensional image sensor is used for inputting an image of a document to a personal computer or a facsimile machine without requiring mechanical scanning of the document. Hereinafter, in this embodiment, a photoelectric conversion device used for a two-dimensional image sensor will be specifically described.

  FIG. 2 is a block diagram showing a schematic configuration of a two-dimensional image sensor (hereinafter referred to as “this apparatus”), and FIG. 3 is a perspective view showing an outline of this apparatus.

  As shown in FIG. 2, the apparatus includes a sensor substrate (a pixel unit described in claims) 20 as a photoelectric conversion unit, a control / communication unit 24 (a control unit described in claims), a driving unit. 28, a detection unit (detection unit described in claims) 29 is included.

The sensor substrate 20 has a plurality of pixels (not shown) arranged in a matrix on an insulating substrate 9 (FIG. 4) to be described later such as a glass substrate. Note that the structure of a pixel in which one photoelectric conversion element (photosensor) is formed in one pixel will be described later with reference to FIG.
A plurality of drive ICs 19 (drive circuit described in claims) and a plurality of detection ICs (photoelectric conversion amount detection means described in claims) 25 are connected to the outer periphery of the sensor substrate 20. ing.

  The drive IC 19 drives a photoelectric conversion element (TFT 7 described later) provided on the sensor substrate 20 for each pixel, and is connected to gate lines 22 provided on the sensor substrate 20. The number of gate lines 22... Is several hundred to several thousand lines depending on the size of the sensor substrate 20 and the pixel pitch, and these gate lines 22 are shared by a plurality of drive ICs 19. . In this case, the number of outputs of one drive IC 19 is, for example, several hundred.

  Each of these drive ICs 19 is mounted on a drive printed circuit board 21, and each drive IC 19 and the drive printed circuit board 21 constitute a drive unit 28.

  The drive printed circuit board 21 is connected to a control / communication unit (light irradiation control means) 24 and has a circuit for controlling the drive IC 19 and interfacing with the control / communication unit 24.

  On the other hand, the detection IC 25 detects an output from the sensor substrate 20 obtained as a result of driving the TFT 7 provided on the sensor substrate 20. Each detection IC 25 is connected to the data lines 23 of the sensor substrate 20. The number of data lines 23 is also several hundred to several thousand lines depending on the size of the sensor substrate 20 and the pixel pitch, and the detection of the output from the data lines 23 is shared by a plurality of detection ICs 25. doing. The number of inputs of one detection IC 25 is, for example, several hundred.

  Each of these detection ICs 25 is mounted on a detection printed circuit board (image information output means) 26, and each detection IC 25 and the detection printed circuit board 26 constitute a detection unit (detection means) 29.

  The detection printed circuit board 26 is connected to the control / communication unit 24 and has a circuit for controlling the detection IC 25 and interfacing with the control / communication unit 24.

  The control / communication unit 24 includes a circuit that handles signals that are not synchronized with the line readout scanning and frame period of the sensor substrate 20 such as a CPU and a memory. Control is performed.

  Further, as shown in FIG. 4, the sensor substrate 20 has a backlight unit 18 disposed on the surface of the insulating substrate 9 opposite to the surface having the pixels. The backlight unit 18 includes an LED, a light guide plate, and a light diffusion plate. The LED lighting / extinguishing is controlled by the control / communication unit 24.

  As shown in FIG. 3, the apparatus having the above-described configuration is provided such that the drive printed board 21 and the detection printed board 26 enter the surface of the backlight unit 18 opposite to the sensor board 20. In this case, the drive IC 19 and the detection IC 25 are formed in a substantially U-shaped cross section with respect to the integrated side surface of the sensor substrate 20 and the backlight unit 18. By adopting such a configuration, the apparatus is miniaturized.

  Further, in the present apparatus, the transparent protective film 3 is formed in a predetermined region of the sensor substrate 20 serving as a sensor portion, so that the surface of the sensor substrate 20 is protected.

FIG. 1 shows a circuit configuration of one pixel in the photoelectric conversion device of the present invention.
This circuit configuration is roughly divided into a sensor substrate 20 and a detection IC 25. However, the detection IC 25 is not provided for each pixel, but is provided in common for a plurality of pixels arranged in one column, as shown in FIGS. Further, although the backlight unit 18 is located below the sensor substrate 20, in this drawing, it is illustrated at a position away from the sensor substrate 20 for convenience of explanation.

  As will be described in detail later, the TFT 7 has a configuration in which a pixel selection transistor and a photosensor are integrated, and functions as the photoelectric conversion element. The source electrode S of the TFT 7 is connected to the data line 23, the drain electrode D is connected to the auxiliary capacitor 17, and the gate is connected to the gate line 22.

  Of the electrodes constituting the auxiliary capacitor 17 provided on the sensor substrate 20, the electrode opposite to the electrode connected to the drain electrode D of the TFT 7 has a CS electrode driving unit (the first voltage described in the claims). Application means) 40 is connected. The CS electrode driver 40 applies a voltage to the drain side of the TFT 7 and Vref the source side voltage, thereby providing a potential difference between the source and drain of the TFT 7, and the auxiliary capacitor 17 through the off-resistance when the TFT 7 receives light. Charge the battery.

  The TFT 7 is turned on when a gate drive signal generated by the drive IC 19 for controlling on / off of the TFT 7 is applied to the gate of the TFT 7 through the gate line 22. When the TFT 7 is turned on, the electric charge accumulated in the auxiliary capacitor 17 is input to the detection IC 25 through the data line 23.

The detection IC 25 includes an integration amplifier 33, a low-pass filter 34, an amplification amplifier 35, a sample hold circuit 36, and the like for the number of lines detected by the detection IC 25. One D (analog / digital) conversion circuit 38 and one control unit 31 are provided. The analog multiplexer 37 and the A / D conversion circuit 38 may be provided with a set for every several tens of lines in consideration of A / D conversion speed up, cost reduction, and the like.
In addition, the detection IC 25 performs double correlation sampling in order to remove the offset and noise of each component circuit.

  In the detection IC 25 having such a configuration, the charge of the auxiliary capacitor 17 input to the detection IC 25 through the data line 23 is first input to the integration amplifier 33 as a negative input. A potential proportional to the generated charge is output. Note that a reference voltage unit (second voltage applying means described in claims) 32 that outputs a reference voltage (Vref) is connected to the positive input of the integrating amplifier 33. The output of the integrating amplifier 33 is input to the amplification amplifier 35 through a low-pass filter 34 provided to reduce noise, and is amplified by a predetermined factor and output.

  The output of the amplification amplifier 35 is input to the sample hold circuit 36 and temporarily held, and the held value is output to one input of a plurality of inputs of the analog multiplexer 37. The output of the analog multiplexer 37 is converted from analog data to digital data by the A / D conversion circuit 38 in the next stage, and is output as image data to the detection printed board 26 via the control unit 31. The control unit 31 controls the detection IC 25 and interfaces with the detection printed circuit board 26.

  A feedback capacitor 39 that temporarily holds the charge of the auxiliary capacitor 17 is connected between the output of the integrating amplifier 33 and the negative input. A reset switch 30 is provided in parallel with the feedback capacitor 39, and the reset switch 30 is ON / OFF controlled by the output of the control unit 31 of the detection IC 25. The integration amplifier 33 and the feedback capacitor 39 also serve as an opening means for releasing the charge of the auxiliary capacitor 17 as will be described in detail later.

  FIG. 4 is a schematic cross-sectional view showing the configuration of the TFT 7 (thin film transistor described in claims) provided for each pixel of the sensor substrate 20. The TFT 7 basically has a configuration of an inverted staggered thin film transistor (TFT). However, a configuration of a staggered thin film transistor in which the upper gate electrode is formed of a light transmissive material may be employed for the TFT 7.

  In the TFT 7 shown in FIG. 4, a bottom gate electrode (hereinafter referred to as a gate electrode) 11 made of chromium (Cr) or the like is formed on an insulating substrate (transparent substrate) 9 made of glass or the like. A bottom gate insulating film (protective layer) 13 made of silicon nitride (SiN) is formed so as to cover 11 and the insulating substrate 9.

  On the gate electrode 11, a photosensitive semiconductor layer formed of i-type amorphous silicon (ia-Si) at a position facing the gate electrode 11 (the photosensitive semiconductor layer according to the claims. The source electrode 10 and the drain electrode 15 are formed on the semiconductor layer 12 so as to face each other with a predetermined interval across the semiconductor layer 12. ing.

  The source electrode 10 and the drain electrode 15 are each connected to the semiconductor layer 12 via the n + silicon layer 4. Further, an insulating protective film (insulating film) 14 is formed on the source electrode 10 and the drain electrode 15. Thus, the TFT 7 is formed.

  Further, an auxiliary capacitor (auxiliary capacitor described in claims) 17 is formed on the drain electrode 15 side of the TFT 7 so that the TFT 7 and the insulating substrate 9 are shared. In the auxiliary capacitor 17, similarly to the gate electrode 11, a lower electrode 16 a made of chromium (Cr) or the like is formed on the insulating substrate 9 and covered with the bottom gate insulating film 13. An upper electrode 16 b is formed at a position opposite to the charge storage capacitor electrode 16 a through the bottom gate insulating film 13 and connected to the drain electrode 15. The upper electrode 16b is also covered with the insulating protective film 14.

  Between the TFT 7 and the auxiliary capacitor 17, the bottom gate insulating film 13, the drain electrode 15, and the insulating protective film 14 have openings as regions that transmit the light 2 (irradiation light) emitted from the backlight unit 18. Part 6 is provided. The opening 6 is a region where there is no opaque metal wiring or metal electrode, and is transparent.

  The insulating protective film 5 is formed on the insulating protective film 14 so as to further cover the TFT 7 and the auxiliary capacitor 17. A sensor substrate 20 (photoelectric conversion unit) is formed from the insulating substrate 9 to the insulating protective film 5. Further, the protective film 3 is formed so as to cover the sensor substrate 20. The original 1 to be irradiated with the light 2 from the backlight unit 18 is placed in close contact with the surface of the protective film 3 opposite to the sensor substrate 20.

  In the operation of the apparatus having the above configuration, as shown in FIGS. 1 and 4, the light 2 is emitted from the backlight unit 18, and the light 2 passes through the opening 6 and is reflected by the document 1. The light enters the semiconductor layer 12 having photosensitivity provided in the TFT 7.

  The TFT 7 can control the conduction state and the non-conduction state by controlling the voltage applied to the gate electrode 11 by the drive IC 19. For example, when a positive voltage is applied to the gate electrode 11 of the TFT 7, an n-channel is formed in the semiconductor layer 12. When a voltage is applied between the source electrode 10 and the drain electrode 15, the voltage between the source electrode 10 and the drain electrode 15 is applied. Current flows.

  Here, FIG. 6 shows how the drain current changes depending on the change of the gate voltage, using a curve I1 during light irradiation and a curve I2 during non-light irradiation. However, the TFT 7 is in a non-conductive state (a state where a negative voltage is applied to the gate electrode).

As shown by the curve I1, when the TFT 7 is irradiated with light in a non-conducting state, a photocurrent is induced in the semiconductor layer 12, and the number of electron holes induced by the irradiation light between the source electrode 10 and the drain electrode 15; That is, a drain current corresponding to the amount of irradiation light flows. At this time, the drain current exceeds, for example, 10 ⁻¹¹ A (ampere). On the other hand, when light is not irradiated, the drain current is extremely small as shown by the curve I2, and can be set to about 10 ^-14 A, for example.

  Both the drain current (I1) at the time of light irradiation and the drain current (I2) at the time of no light irradiation decrease as the negative voltage is increased to the gate electrode and eventually become saturated. Therefore, the difference between the drain current at the time of light irradiation and the drain current at the time of no light irradiation also increases as the negative voltage is increased at the gate electrode, and eventually becomes saturated.

  After all, when a negative voltage is applied to the gate electrode of the thin film transistor and the drain current during light irradiation is accumulated for a predetermined time, the difference becomes large when the photoelectric conversion amount due to the accumulation of drain current during non-light irradiation is used as a reference. can do. Thereby, a photoelectric conversion device having a large dynamic range can be obtained.

  More specifically, the charge of the auxiliary capacitor 17 is once released, and the charge is charged from the source side to the auxiliary capacitor 17 for a predetermined time by the drain current at the time of light irradiation and the drain current at the time of non-light irradiation. By detecting the charge of the auxiliary capacitor 17 with the detection IC 25, the difference can be made larger and a photoelectric conversion device having a large dynamic range can be obtained.

  Next, with reference to FIG. 1 and FIG. 5, the operation of each part of the apparatus having the above configuration will be described with time. FIG. 5 shows time charts of respective parts in the present apparatus by waveforms A to H. Here, in this time chart, in order to explain that the photoelectric conversion amount can be obtained by a simple and repetitive method, and in order to explain the connection between the operation and the operation in an easy-to-understand manner, the two operations will be described separately in sections.

In this time chart, for convenience of explanation, it is assumed that there is no charge in the auxiliary capacitor 17 before the time t1 of the section 1, the CS electrode drive voltage of the waveform D is V2, and the drain voltage of the TFT 7 of the waveform E is Vref. ing.
(1) Time t1 to t3 in section 1
As shown in the waveform B, the reset switch 30 of the integration amplifier 33 is turned off from the on state at time t1 in the section 1, and the reset of the integration amplifier 33 is released.

  As shown in the waveform C, when the gate drive signal is turned on at time t2 and the TFT 7 is turned on, a feedthrough phenomenon occurs in which charge leaks from the gate to the drain D and source S, and the leaked charge (holes) causes As shown by the waveform F, the output of the integrating amplifier 33 falls. In the TFT 7, the TFT 7 has a portion overlapping the gate (see FIG. 4) between the gate and the drain D and between the gate and the source S, and the parasitic capacitance 41 exists in the overlapping portion. It happens because you are.

  As indicated by the waveform F, the output of the integrating amplifier 33 is lower by the value W1 than at time t1 at time t3 because of the effect of the feedthrough phenomenon. At this time, the output of the integrating amplifier 33 is delayed in falling due to the time constant of the data line 23 of the sensor substrate 20.

  As shown by the waveform G, the output of the low-pass filter 34 to which the output of the integration amplifier 33 is input falls from the time t2 toward the output value of the integration amplifier 33 with a time constant. This descending width finally becomes the value W1.

  As shown by the waveform H, the output of the amplification amplifier 35 to which the output of the low-pass filter 34 is input decreases toward the output value of the integrating amplifier 33 × G (gain). This descending width finally becomes the value W1 × G, and this value is sampled and held at time t3 (pulse output timing in the sample hold signal shown in waveform A). This value W1 × G is a feedthrough signal component. The reason why the sample-and-hold is also performed in the section 1 in this way is that it is assumed that the circuit operates at the same timing as the section 2 described later.

  Further, as shown in the waveform D, the voltage of the CS electrode driving unit 40 takes a binary voltage (V2, V3) in this embodiment, but takes a value V2 from t1 to t3. The relationship between V2 and V3 is V2> V3. These V2 and V3 are connected to the drain D of the TFT 7 by capacitive coupling of the auxiliary capacitor 17, and when the CS electrode drive voltage is lowered from V2 to V3 as shown at time t6 of the waveform D when the TFT 7 is turned off. As shown at time t6 to t1 ′ of the waveform E, the TFT drain voltage is also relatively lowered by the potential difference (W3) of V2-V3.

  Note that the magnitude relationship between Vref and V2 and V3 is not necessarily V2> Vref> V3. This is because this is capacitive coupling by a capacitor, that is, the potential difference of Vref is created by the potential difference between V2 and V3, and the magnitude relationship is determined by the amount of charge to the auxiliary capacitor, the operating voltage of the LSI, and the like.

(2) Time t4 to t6 in section 1
As shown in the waveform B, when the reset switch 30 of the integration amplifier 33 is turned on from the OFF at the time t4 in the interval 1, the feedback capacitor 39 of the integration amplifier 33 is short-circuited, and the output of the integration amplifier 33 is shown in the waveform F. Becomes the reference voltage (Vref). For this reason, as shown in the waveform G and the waveform H, the outputs of the low-pass filter 34 and the amplification amplifier 35 are also Vref. Note that, as shown by the waveform E, the drain voltage of the TFT 7 also maintains Vref.

  Further, before the time t4, the integration amplifier 33 pulls all of the charge to the feedback capacitor 39 by its action (virtual short circuit) while the gate drive signal is on, so that the charge is released from the auxiliary capacitor 17. The state (charge is 0 with respect to the voltage vref). Therefore, the integrating amplifier 33 and the feedback capacitor 39 function as an opening unit that releases the charge of the auxiliary capacitor 17 before the light irradiation. The reason why the drain voltage of the TFT 7 is Vref as described above is that all the charges generated on the drain side of the TFT 7 move to the feedback capacitor 39 of the integrating amplifier 33.

  The integrating amplifier 33 operates so as to pull the charge on the input terminal to the feedback capacitor 39 regardless of whether the reset switch 30 is on or off. However, in order to reduce the charge of the feedback capacitor 39 to 0, the reset switch 30 is turned on.

  For convenience of explanation, it is assumed that there is no charge in the auxiliary capacitor 17 before the time t1 of the section 1. However, as described above, even if there is a charge in the auxiliary capacitor 17, the gate drive signal is turned on. In this state, the charge of the auxiliary capacitor 17 can be reduced to zero by turning the reset switch 30 from OFF to ON at time t4.

  As shown in the waveform C, when the gate drive signal of the TFT 7 is turned off at time t5, the charge (electrons) is converted into an integrating amplifier due to the feedthrough phenomenon due to the parasitic capacitance 41 mainly between the gate and the source S of the TFT 7. However, since the integrating amplifier 33 is in the reset state (ON state) as shown in the waveform B, the electric charge that has flowed in disappears. On the other hand, charge (electrons) flows into the auxiliary capacitor 17 due to the feedthrough phenomenon caused mainly by the parasitic capacitance 41 between the gate and the drain D of the TFT 7, and the drain voltage of the TFT 7 is Move down by W2. Further, since the gate drive signal is in the off state, the charge of the auxiliary capacitor 17 is not pulled by the integrating amplifier 33.

  Next, as shown in the waveform D, at time t6, the voltage of the CS electrode driving unit (first voltage applying unit described in claims) 40 changes from V2 to V3 (change in voltage described in claims). When the voltage is stepped down, the potential of the drain D decreases accordingly.

  At time t6, when the TFT 2 is irradiated with the light 2 from the backlight (light source described in claims) 18 for a predetermined time, a charge flows from the source S side of the TFT 7 to the auxiliary capacitor 17 due to photocurrent. Charge is accumulated in the capacitor 17 (charging process described in the claims; the amount of charge varies depending on the amount of light received). Along with this, the drain voltage of the TFT 7 increases (from t6 in section 1 to t1 in section 2 (broken line in waveform E)). In addition, since no photocurrent is generated in the TFT 7 not irradiated with the light 2, no charge flows into the auxiliary capacitor 17, and the drain voltage of the TFT 7 does not change (from t6 in section 1 to t1 ′ in section 2 (solid line of waveform E). ).

  The charge of the auxiliary capacitor 17 by the photocurrent described above is performed by changing the voltage on the drain side of the TFT 7 from Vref, and by the voltage difference generated between the source S and the drain D of the TFT 7, the OFF resistance when the TFT 7 receives light. Through this, the auxiliary capacitor 17 is charged with electric charges.

  When the potential difference between V2 and V3 is increased, the potential difference between the drain D and the source S of the TFT 7 is also increased, and the amount of charge flowing through the TFT 7 can be increased when the light 2 is irradiated. Thereby, the difference in charging amount (charging difference) between the pixel irradiated with the light 2 and the pixel not irradiated with the light 2 can be further increased. Furthermore, by increasing the potential difference of V2-V3, it is possible to shorten the irradiation time of the light 2 required to make a certain amount of charge difference between the pixel not irradiated with the light 2 and the pixel irradiated with the light 2. I can do it.

(3) Time t1 ′ to t3 ′ of section 2
As shown in the waveform B, the reset switch 30 of the integration amplifier 33 is turned off from on at time t1 ′ in the interval 2, and the integration amplifier 33 is reset in preparation for pulling the charge accumulated in the auxiliary capacitor 17 to the feedback capacitor 39. Canceled. Further, when the CS electrode drive voltage is boosted from V3 to V2, the voltage of the auxiliary capacitor 17 increases by the value W3.

  Further, as shown in the waveform C, when the gate drive signal is turned on at time t2 ′ and the TFT 7 is turned on, a feedthrough phenomenon occurs in which charge leaks from the gate to the drain D and source S, and the leaked charge (positive Hole), the output of the integrating amplifier 33 drops as shown in the waveform F. At this time, the charge (electrons) injected into the auxiliary capacitor 17 from the time t5 in the section 1 and from t6 in the section 1 to t1 'in the section 2 also flows to the source S side and is pulled and accumulated in the feedback capacitor 39.

  At this time t2 ', the drain voltage of the TFT 7 becomes Vref and the charge of the auxiliary capacitor 17 is released in preparation for the next light irradiation. In other words, the integration amplifier 33 pulls all the charges (electrons) accumulated in the auxiliary capacitor 17 to the feedback capacitor 39 so that the drain voltage of the TFT 7 becomes Vref.

Here, as shown by the waveform F at time t2 ′ to t5 ′, the output decrease width of the integrating amplifier 33 is different between the TFT 7 (pixel) to which the light 2 hits and the TFT 7 (pixel) to which the light 2 does not hit. This is because the amount of charge injected into the auxiliary capacitor 17 at time t5 in section 1 and from t6 in section 1 to t1 ′ in section 2 varies depending on the state of irradiation of light 2 onto the TFT 7.
Specifically, in the case of the TFT 7 that is not exposed to light 2, only charges (electrons at t5 and holes at t2 ′) due to the feedthrough phenomenon are pulled and accumulated in the feedback capacitor 39. In the case of the TFT 7 exposed to light 2, the charge (electrons at t5 and holes at t2 ′) due to the feedthrough phenomenon and the charges (holes) injected into the auxiliary capacitor 17 by the photocurrent are added together Therefore, a difference occurs in the amount of charge accumulated in the feedback capacitor 39.

  As a result, the output of the integrating amplifier 33 slightly falls from Vref so as to show the output of the integrating amplifier 33 connected to the TFT 7 that does not receive the light 2 in the solid line at time t2 ′ to t5 ′ of the waveform F. On the other hand, as indicated by the broken line, the output of the integrating amplifier 33 connected to the TFT 7 to which the light 2 strikes is further lowered by W4. That is, there is a difference of W4 (t3 ′) between the output of the integrating amplifier 33 of the TFT 7 that was exposed to the light 2 and the output of the integrating amplifier 33 of the TFT 7 that was not exposed to the light 2.

  Since the integrating amplifier 33 is an inverting amplifier circuit, the waveform E of the higher drain voltage of the TFT 7 (broken line) from t6 to t1 ′ is the lower output (broken line) of the output of the integrating amplifier 33 from t2 ′ to t5 ′. ) Waveform F.

  As shown in the waveform H, this fall finally becomes the value W4 × G as the output of the amplification amplifier 35, and this value is sampled and held at time t3 ′ (pulse output timing in the sample hold signal shown in the waveform A). Sample and hold by the circuit 36 (photoelectric conversion amount detection means). This sampled and held value is the difference between the detection values of the pixel irradiated with the light 2 and the pixel not irradiated with the light 2. This value is output as a photoelectric conversion amount via the analog multiplexer 37, the A / D conversion circuit 38, and the control unit 31.

(4) Time t4 ′ to t5 ′ of section 2
As shown in the waveform B, when the reset switch 30 of the integration amplifier 33 is turned on from OFF at time t4 ′ in the interval 2, the feedback capacitor 39 of the integration amplifier 33 is short-circuited, and the feedback capacitor 39 is prepared for the next light irradiation. To zero. Along with this, the output of the integrating amplifier 33 returns to the reference voltage (Vref). For this reason, as shown by the waveform G and the waveform H, the outputs of the low-pass filter 34 and the amplification amplifier 35 are also restored to Vref.

  Next, as shown in the waveform C, when the gate drive signal is turned off at time t5 ′, the charge (electrons) is mainly caused by the feedthrough phenomenon due to the parasitic capacitance 41 between the gate and the source S of the TFT 7. Although it flows into the feedback capacitor 39 of the integrating amplifier 33, since the integrating amplifier 33 is in a reset state, the charge that has flowed in disappears.

  On the other hand, charge (electrons) flows into the auxiliary capacitor 17 due to the feedthrough phenomenon caused mainly by the parasitic capacitance 41 between the gate and the drain D of the TFT 7, and as shown in the waveform E, the TFT drain voltage is Move down by W2. Next, as shown in the waveform D, when the CS electrode drive voltage is stepped down from V2 to V3 at time t6 ', the potential of the drain D is lowered along with the whole of W3.

  As described above, when the TFT 2 is irradiated with the light 2 for a predetermined time at the time t6 ′ when the charge release of the auxiliary capacitor 17 and the reset of the feedback capacitor 39 are completed, the source S of the TFT 7 is supplied to the auxiliary capacitor 17 by the photocurrent. Charge flows from the side, and the drain voltage of the TFT 7 rises accordingly (from t6 ′ in section 2 to (broken line in waveform E)). Further, since no photocurrent is generated in the TFT 7 not irradiated with light, no charge flows into the auxiliary capacitor 17 and the drain voltage of the TFT 7 does not change (from t6 'in section 2 (solid line of waveform E)).

  As described above, by performing the operation from the section 1 to the section 2 once, the photoelectric conversion amount can be detected once at the time t3 ′ of the section 2. In actual driving, the above-described detection operation is repeated by repeating the operations in the sections 2 to 2, and the photoelectric conversion amount can be continuously detected at time t3 '.

  During the period (time t1 ′ to t6 ′) in which the photoelectric conversion amount is detected based on the value sampled and held at time t3 ′, the backlight 18 is controlled by the control / communication unit 24 and the light 2 is emitted. Don't break. This is due to the following reasons.

  As shown in FIG. 11, when detecting the photoelectric conversion amount of a certain line (the uppermost line in FIG. 11), the integration amplifier 33 is turned on from the auxiliary capacitor 17 by turning on the gate drive signal of that line. At this time, if light is also applied to the off-state TFT 7 of another line, the off-resistance of the TFT 7 is lowered and a leak current is generated. The integrating amplifier 33 also pulls the charge of this leakage current to the feedback capacitor 39, so that the correct photoelectric conversion amount cannot be detected. Therefore, the light is stopped when the photoelectric conversion amount is detected.

  As described above, in the present embodiment, as shown in FIG. 5, the charge is charged in the auxiliary capacitor 17 by setting the CS electrode drive voltage to the low level at time t6 and the high level at time t1 ′. Conversely, the auxiliary capacitor 17 can be charged even by driving in the reverse direction such that the CS electrode drive voltage is set to the high level at time t6 and is set to the low level at time t1. However, in this case, charge is opposite to the feedthrough signal component due to the gate drive signal being turned off at time t5, and the amount of charge charged in the auxiliary capacitor 17 is smaller than in the case of FIG.

[Embodiment 2]
Another embodiment of the present invention will be described below. For convenience of explanation, members having the same functions as those shown in the above embodiment are given the same reference numerals, and the explanation thereof is omitted.

The circuit configuration for one pixel in the two-dimensional image sensor (this device) according to the present embodiment is the same as that of the first embodiment (FIG. 1).
As shown in FIG. 7, the difference from the first embodiment is that the voltage of the reference voltage unit 32 takes a binary value (Vref and V1), and the CS electrode driving voltage applied to the auxiliary capacitor 17 by the CS electrode driving unit 40. Is constant and unchanging.

  In this embodiment, the voltage on the source side of the TFT 7 is changed from Vref, and the auxiliary capacitor 17 is charged through the off-resistance at the time of light reception of the TFT 7 due to the voltage difference generated between the source and drain of the TFT 7. Yes.

  Hereinafter, the operation of each part of the apparatus will be described with time, with reference to the time chart of FIG. FIG. 8 shows a time chart of each part in this apparatus by waveforms I to P. In this time chart, for the sake of convenience of explanation, it is assumed that there is no charge in the auxiliary capacitor 17 before the time t1 of the section 1.

(1) Time t1 to t4 of section 1
As shown in the waveform J, the reset switch 30 of the integration amplifier 33 is turned off from the on state at time t1 in the section 1, and the reset of the integration amplifier 33 is released.

  As shown in the waveform K, when the gate drive signal is turned on at time t2 and the TFT 7 is turned on, a feedthrough phenomenon occurs in which charges leak from the gate to the drain D and the source S, and the leaked charges (holes) As shown by the waveform N, the output of the integrating amplifier 33 falls. In the TFT 7, the TFT 7 has a portion overlapping the gate (see FIG. 4) between the gate and the drain D and between the gate and the source S, and the parasitic capacitance 41 exists in the overlapping portion. It happens because you are.

  As indicated by the waveform N, the output of the integrating amplifier 33 is lower by the value W5 at time t3 than at time t1, because of the feedthrough phenomenon. At this time, the output of the integrating amplifier 33 is delayed in falling due to the time constant of the data line 23 of the sensor substrate 20.

  As shown by the waveform O, the output of the low-pass filter 34 to which the output of the integration amplifier 33 is input falls from the time t2 toward the output value of the integration amplifier 33 with a time constant. This descending width finally becomes the value W5.

  As shown by the waveform P, the output of the amplification amplifier 35 to which the output of the low-pass filter 34 is input decreases toward the output value × G (gain) of the integration amplifier. This descending width finally becomes the value W5 × G, and this value is sampled and held at time t3 (pulse output timing in the sample and hold signal shown in waveform I). This sampled and held value is a feedthrough signal component from the parasitic capacitance 41 and the auxiliary capacitance 17 of the TFT 7.

  Next, when the reset switch 30 of the integration amplifier 33 is turned on from time OFF at time t4, the feedback capacitor 39 of the amplifier 33 is short-circuited as indicated by the waveform N, and the output of the integration amplifier 33 is indicated as indicated by the waveform N. Becomes the reference voltage (Vref). For this reason, as shown in the waveform O and the waveform P, the outputs of the low-pass filter 34 and the amplification amplifier 35 are also Vref. As shown by the waveform M, the drain voltage of the TFT 7 also maintains Vref.

(2) Time t5 to t6 in section 1
As shown in the waveform K, when the gate drive signal is turned off at time t 5, the charge (electrons) is caused to flow through the integration amplifier 33 due to the feedthrough phenomenon caused mainly by the parasitic capacitance 41 between the gate and source S of the TFT 7. Although it flows into the feedback capacitor 39, since the integrating amplifier 33 is in a reset state, the charge that has flowed in disappears. On the other hand, charge (electrons) flows into the auxiliary capacitor 17 mainly due to the feedthrough phenomenon due to the parasitic capacitance 41 between the gate and the drain D of the TFT 7, and the drain voltage of the TFT 7 is , The value is decreased by W6.

  Next, as shown in the waveform L, the voltage of the reference voltage unit 32 is driven to V1 higher than Vref at time t6. As a result, as shown by the waveform N, the waveform O, and the waveform P, the outputs of the waveform integration amplifier 33, the low-pass filter 34, and the amplification amplifier 35 are boosted to V1.

  At this time, when the TFT 7 is irradiated with light, a charge flows from the source side of the TFT 7 to the auxiliary capacitor 17 due to the photocurrent, and as a result, the TFT drain voltage rises as shown by the broken line of the waveform M ( T6 in section 1 to t1 ′ in section 2). That is, the voltage on the source side of the TFT 7 is increased from Vref to V1, and the auxiliary capacitor 17 is charged through the off-resistance at the time of light reception of the TFT 7 due to the voltage difference generated between the source and drain of the TFT 7 (drain voltage is smaller than Vref). To do.

  Further, since no photocurrent is generated in the TFT 7 that is not irradiated with light, the charge of the auxiliary capacitor 17 is held, and the TFT drain voltage does not change as indicated by the solid line of the waveform M (from t6 in section 1 to section 2). t1 ′).

(3) Time t1 ′ to t7 ′ of section 2
As shown by the waveform L, the voltage of the reference voltage unit 32 is driven so as to drop from V1 to Vref at time t1 ′ in section 2. As a result, as shown by the waveform N, the waveform O, and the waveform P, the outputs of the integrating amplifier 33, the low-pass filter 34, and the amplification amplifier 35 are returned to Vref.

  Next, as shown in the waveform J, the reset switch 30 of the integration amplifier 33 is turned off from time ON at time t2 ′, and the integration amplifier 33 is reset in preparation for pulling the charge accumulated in the auxiliary capacitor 17 to the feedback capacitor 39. Canceled. Subsequently, as shown in the waveform K, when the gate drive signal is turned on at time t3 ′ and the TFT 7 is turned on, a feedthrough phenomenon occurs in which charge leaks from the gate to the drain D and source S, and the leaked charge ( As a result, the output of the integrating amplifier 33 drops as shown by the waveform N. At this time, from time t6 in section 1 to t1 'in section 2, the charge (holes) injected into the auxiliary capacitor 17 also flows to the source S side and is pulled and accumulated in the feedback capacitor 39.

  After this time t3 ', the drain voltage of the TFT 7 becomes Vref, and the charge of the auxiliary capacitor 17 is released in preparation for the next light irradiation. In other words, the integration amplifier 33 pulls all the charges (electrons) accumulated in the auxiliary capacitor 17 to the feedback capacitor 39 so that the drain voltage of the TFT 7 becomes Vref.

  Here, as indicated by the waveform N at times t3 'to t5', the output decrease width of the integrating amplifier 33 is different between the TFT 7 (pixel) to which the light 2 hits and the TFT 7 (pixel) to which the light 2 does not hit. This is because the amount of charge injected into the auxiliary capacitor 17 from t5 in section 1 and from t6 in section 1 to t1 'in section 2 differs depending on the state of irradiation of the light 2 to the TFT7. Specifically, in the case of the TFT 7 that does not receive the light 2, only charges (electrons at t 5 and holes at t 3 ′) caused by the feedthrough phenomenon are pulled and accumulated in the feedback capacitor 39. In the case of the TFT 7 exposed to light 2, the charge (electrons at t5 and the holes at t3 ′) due to the feedthrough phenomenon and the charge (holes) injected into the auxiliary capacitor 17 by the photocurrent are added together. Therefore, a difference occurs in the amount of charge accumulated in the feedback capacitor 39.

As a result, the output of the integrating amplifier 33 slightly decreases from Vref so as to show the output of the integrating amplifier 33 connected to the TFT 7 that does not receive the light 2 in the solid line at time t3 ′ to t5 ′ of the waveform N. On the other hand, as indicated by the broken line, the output of the integrating amplifier 33 connected to the TFT 7 to which the light 2 hits is further lowered by W7.
That is, there is a difference of W7 (t4 ′) between the output of the integrating amplifier 33 of the TFT 7 that has been exposed to the light 2 and the output of the integrating amplifier 33 of the TFT 7 that has not been exposed to the light 2.

  As shown in the waveform P, this decrease finally becomes the value W3 × G at the output of the amplification amplifier 35, and this value is sampled and held at time t4 ′ (timing of pulse output in the sample and hold signal shown in waveform I). To do. This sampled and held value is the difference between the detection value of the pixel irradiated with light and the pixel not irradiated.

  Subsequently, as shown in the waveform J, when the reset switch 30 of the integrating amplifier 33 is turned on from time OFF at time t5 ′, the feedback capacitor 39 of the amplifier 33 is short-circuited, and the feedback capacitor 39 of the feedback capacitor 39 is prepared for the next light irradiation. Charge is reduced to zero. As a result, the output of the integrating amplifier 33 returns to the reference voltage (Vref) as shown by the waveform N. For this reason, as shown in the waveform O and the waveform P, the outputs of the low-pass filter 34 and the amplification amplifier 35 are also restored to Vref.

  Next, as shown in the waveform K, when the gate drive signal is turned off at time t6 ′, the charge (electrons) is mainly caused by the feedthrough phenomenon due to the parasitic capacitance 41 between the gate and the source S of the TFT 7. Although it flows into the feedback capacitor 39 of the integrating amplifier 33, since the integrating amplifier 33 is in a reset state, the flowed-in charge disappears.

  On the other hand, charge (electrons) flows into the auxiliary capacitor 17 due to the feedthrough phenomenon caused mainly by the parasitic capacitance 41 between the gate and the drain D of the TFT 7, and the drain voltage of the TFT 7 is , Move down by W6.

  Next, as shown in the waveform N, when the voltage of the reference electrode unit 32 is driven to V1 higher than Vref at time t7 ′, the output of the integrating amplifier 33 is accordingly accompanied by the waveforms N, O, and P. The output of the low-pass filter 34 and the output of the amplification amplifier 35 also rise to V1.

  As described above, when the TFT 2 is irradiated with the light 2 at the time t7 ′ when the charge release of the auxiliary capacitor 17 and the reset of the feedback capacitor 39 are completed, a charge is applied to the auxiliary capacitor 17 from the source side of the TFT 7 by a photocurrent. As a result, the drain voltage of the TFT 7 rises as indicated by a broken line in the waveform M (same as t6 in section 1 to t1 ′ in section 2). Further, since no photocurrent is generated in the TFT 7 not irradiated with the light 2, the charge of the auxiliary capacitor 17 is held, and the drain voltage of the TFT 7 does not change (same as t <b> 6 in section 1 to t <b> 1 ′ in section 2).

  As described above, by performing the operation from the section 1 to the section 2 once, the photoelectric conversion amount can be detected once at the time t4 'of the section 2. Further, in actual driving, the above-described detection operation is repeated by repeating the operations in section 2 to section 2, and the photoelectric conversion amount can be continuously detected at time t4 '.

  In the present embodiment, as shown in FIG. 8, the integration capacitor reference voltage is set to high level at time t6 in section 1 and is set to low level at time t1 in section 2, so that the auxiliary capacitor 17 is charged. However, it is possible to charge the auxiliary capacitor 17 even if driving in the reverse direction is performed such that the integration amplifier reference voltage is set to low level at time t6 in section 1 and is set to high level at time t1 in section 2. it can. However, in this case, charging is performed at a voltage in the same direction as the feedthrough signal component by turning off the gate signal at time t6, and the amount of charge charged in the auxiliary capacitor 17 is smaller than that in the case shown in FIG.

  Further, in the present embodiment, in the block diagram shown in FIG. 7, the reference voltage unit 32 is driven with a binary voltage, but the voltage of the reference voltage unit 32 is set to a constant voltage, A similar function can be obtained by switching between the reference voltage and the charging voltage.

[Embodiment 3]
Still another embodiment of the present invention will be described below. For convenience of explanation, members having the same functions as those shown in the above embodiment are given the same reference numerals, and the explanation thereof is omitted.

  The circuit configuration for one pixel in the two-dimensional image sensor (this device) according to the present embodiment is the same as that of the first embodiment (FIG. 1). The difference from the first and second embodiments is that the voltage of the reference voltage unit 32 takes a binary value (Vref and V1), and the CS electrode driving voltage applied to the auxiliary capacitor 17 by the CS electrode driving unit 40 also has a binary value (V2). , V3). That is, the driving method of the reference voltage and the CS electrode driving voltage is a combination of the first embodiment and the second embodiment. In other words, as shown in FIG. 9, the two-dimensional image sensor (photosensor) of the present embodiment uses the voltage (constant) of the CS electrode driver 40 in FIG. 7 as the voltage of the CS electrode driver 40 in FIG. The configuration is changed to (V2, V3; variable).

  Therefore, in the present embodiment, by changing the source S and drain D of the TFT 7 to voltages in opposite directions around the reference voltage (Vref), the auxiliary capacitor 17 is charged through the off-resistance when the TFT 7 receives light. To do.

  Hereinafter, the operation of each part of the apparatus will be described with time, with reference to the time chart of FIG. FIG. 10 shows the time chart of each part in this apparatus by waveforms Q to Y. In this time chart, for the sake of convenience of explanation, it is assumed that there is no charge in the auxiliary capacitor 17 before the time t1 of the section 1.

(1) Time t1 to t6 of section 1
The operation of each part at time t1 to t5 in section 1 is basically the same as the waveforms A to H shown in FIG. 5 in the first embodiment, as shown by waveforms Q to Y. At time t3, the value W8 × G is sampled and held as the feedthrough signal component from the parasitic capacitance 41 and the auxiliary capacitance 17 of the TFT 7. When the gate drive signal of the TFT 7 is turned off at time t5, electric charges (electrons) flow into the auxiliary capacitor 17 due to a feedthrough phenomenon caused mainly by the parasitic capacitance 41 between the gate and the drain D of the TFT 7, and the waveform As indicated by V, the drain voltage of the TFT 7 decreases by W9.

  Next, as shown in the waveform T, the reference voltage of the reference voltage unit 32 is driven to V1 higher than Vref at time t6. As a result, as shown by the waveform W, the waveform X, and the waveform Y, the outputs of the integrating amplifier 33, the low-pass filter 34, and the amplification amplifier 35 become V1. Further, as shown in the waveform U, the CS electrode drive voltage is lowered from V2 to V3 at the same time when the reference voltage is boosted, and accordingly, the drain D voltage is lowered by W10 as shown in the waveform V.

  At this time t6, when the TFT 2 is irradiated with the light 2, a charge flows from the source S side of the TFT 7 to the auxiliary capacitor 17 due to the photocurrent, and as a result, the TFT drain voltage becomes as shown by the broken line of the waveform V. Ascending (t6 in section 1 to t1 ′ in section 2). That is, by changing the source S and drain D of the TFT 7 to voltages in opposite directions around the reference voltage (Vref), the auxiliary capacitor 17 is charged through the off-resistance when the TFT 7 receives light. .

  Further, since no photocurrent is generated in the TFT 7 that is not irradiated with the light 2, the charge of the auxiliary capacitor 17 is retained, and the TFT drain voltage does not change as indicated by the solid line of the waveform V (from t 6 to Section 2 in the section 1). t1 ′).

(3) Time t1 ′ to t5 ′ of section 2
As shown in the waveform T, the voltage of the reference voltage unit 32 of the integrating amplifier 33 is driven to Vref lower than V1 at time t1 ′ in the section 2. As a result, as shown by the waveform W, the waveform X, and the waveform Y, the outputs of the integrating amplifier 33, the low-pass filter 34, and the amplification amplifier 35 become Vref. Further, as shown in the waveform U, when the CS electrode drive voltage is increased from V3 to V2, the voltage of the auxiliary capacitor 17 increases by the value W3.

  Next, as shown in the waveform R, the reset switch 30 of the integration amplifier 33 is turned off from on at time t2 ′, and the integration amplifier 33 is reset as preparation before pulling the charge accumulated in the auxiliary capacitor 17 to the feedback capacitor 39. Canceled. Subsequently, as shown in the waveform S, when the gate drive signal is turned on at the next time t3 ′ and the TFT 7 is turned on, a feed-through phenomenon in which electric charge leaks from the gate to the drain D and the source S occurs and leaks. Due to the charge (holes), the output of the integrating amplifier 33 falls. Furthermore, from time t6 in section 1 to time t1 'in section 2, the charge (holes) injected into the auxiliary capacitor 17 also flows to the source S side and is pulled and accumulated in the feedback capacitor 39.

  After this time t3 ', the drain voltage of the TFT 7 becomes Vref, and the charge of the auxiliary capacitor 17 is released in preparation for the next light irradiation. In other words, the integration amplifier 33 pulls all the charges (electrons) accumulated in the auxiliary capacitor 17 to the feedback capacitor 39 so that the drain voltage of the TFT 7 becomes Vref.

  The difference between the TFT (pixel) 7 that receives the light 2 and the TFT 7 that does not receive the light 2 and the output of the amplification amplifier 35 finally results in a value of W11 × G. About the operation | movement detected as quantity, it is not different from Embodiment 1 * 2.

  In the present embodiment, as shown in FIG. 10, the reference voltage of the integrating amplifier 33 is set to the high level at the time t6 in the section 1, the CS electrode driving voltage is set to the low level, and the integrating amplifier 33 is set to the low level at the time t1 ′ in the section 2. The auxiliary capacitor 17 is charged by setting the reference voltage to the low level and the CS electrode drive voltage to the high level, but at the time t6 in section 1, the reference voltage of the integrating amplifier 33 is set to the low level and the CS electrode is charged. The auxiliary capacitor 17 is charged even when the driving voltage is set to the high level, the reference voltage of the integrating amplifier 33 is set to the high level at the time t1 ′ of the interval 2, and the CS electrode driving voltage is set to the low level. Can be charged.

  However, in this case, the charge-through signal component is canceled by turning off the TFT gate drive signal at time t5 in the section 1, and the charge amount charged in the auxiliary capacitor 17 is smaller than that in the case shown in FIG.

  As described above, in the photoelectric conversion device of the present invention, the photoelectric conversion element itself has a photosensor function and a pixel selection function (switching function), and the charge of the auxiliary capacitor 17 is released before light irradiation. The amount of charge obtained by accumulating the photocurrent in the auxiliary capacitor 17 for a predetermined time is defined as the photoelectric conversion amount.

  Thereby, a photosensor part can be made small, the density of pixels can be increased, and a photosensor with a simple structure can be realized. In addition, the photoelectric conversion device having a large dynamic range can be obtained.

  In the photoelectric conversion device of the present invention, the CS electrode driving unit 40 may be used as a method of charging the auxiliary capacitor 17 with electric charges. Thereby, a complicated structure is not required, it is possible to drive at a simple timing, and an effect that a photosensor having a large dynamic range can be realized.

  In the photoelectric conversion device of the present invention, the amount of charge obtained by subtracting the charge accumulated in the photocurrent for a predetermined time from the charge charged in the auxiliary capacitor 17 may be used as the amount of photoelectric conversion. As a method for charging the auxiliary capacitor 17 with a predetermined charge, an external circuit connected to the data line 23 can be used. Accordingly, there is an effect that it is possible to realize a photosensor that can be driven at a simple timing without requiring a complicated structure and that has a large dynamic range.

  In the photoelectric conversion device of the present invention, an external circuit connected to the data line 23 and the CS electrode driving unit 40 can also be used as a method of charging the auxiliary capacitor 17 with electric charges. Thereby, a complicated structure is not required, it is possible to drive at a simple timing, and an effect that a photosensor having a large dynamic range can be realized.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The photoelectric conversion device of the present invention can be applied to a one-dimensional image sensor in addition to the above-described two-dimensional image sensor.

  The present invention can also be applied to PDA (Personal Digital Assistants). In this case, it is conceivable that the two-dimensional image sensor of the present invention is provided on the surface opposite to the display screen of the PDA, so that the original is taken in as it is or an arbitrary portion of the original is enlarged.

  Further, the photoelectric conversion device of the present invention is a photoelectric conversion device comprising a plurality of photoelectric conversion elements, wherein the photoelectric conversion element includes a gate electrode, a source electrode, a drain electrode, a gate insulating film, a thin film transistor having a photosensitive semiconductor layer, A thin film transistor comprising an auxiliary capacitor connected to the drain electrode of the thin film transistor and a photoelectric conversion amount detecting means connected to the source electrode, and bringing the thin film transistor into a conductive state to release the charge from the auxiliary capacitor and irradiating light after the release. Is turned off for a predetermined time and a voltage is applied between the drain and the source to charge the auxiliary capacitor, and after a predetermined time, the thin film transistor is turned on, so that the photoelectric conversion amount detecting means It may be detected.

  Further, the photoelectric conversion device of the present invention is a photoelectric conversion device comprising a plurality of photoelectric conversion elements, wherein the photoelectric conversion element includes a gate electrode, a source electrode, a drain electrode, a gate insulating film, a thin film transistor having a photosensitive semiconductor layer, It consists of an auxiliary capacitor connected to the drain electrode of the thin film transistor and a photoelectric conversion amount detecting means connected to the source electrode side. The photoelectric conversion amount detecting means detects the photoelectric conversion amount by making the thin film transistor conductive. Thereafter, the charge of the auxiliary capacitor is released, and after the release, a voltage is applied between the drain and source of the thin film transistor, and the thin film transistor is turned off for a predetermined time while irradiating light. It is good also as detecting the continuous photoelectric change amount by repeating the operation | movement at the time of the said conduction | electrical_connection and the non-conduction operation | movement of the said thin-film transistor after predetermined time.

  The method of applying a voltage between the drain and source of the thin film transistor may change the voltage of the electrode on the side opposite to the thin film transistor drain side of the auxiliary capacitor.

  A voltage may be applied between the source and drain of the thin film transistor by applying a predetermined voltage from an external circuit connected to the source electrode of the thin film transistor.

  A voltage is applied between the source and drain of the thin film transistor by applying a predetermined voltage from an external circuit connected to the source electrode of the thin film transistor and changing the voltage of the electrode on the side opposite to the thin film transistor drain side of the auxiliary capacitor. Also good.

  A two-dimensional image sensor of the present invention includes a plurality of data lines, a plurality of scanning lines, a thin film transistor having a photosensitive semiconductor layer provided at an intersection of the data lines and the scanning line, and a storage connected to the thin film transistor. A capacitor, a signal detection circuit connected to the data line, a scanning line driving circuit for supplying a scanning signal to the scanning line, an auxiliary capacitor charging means for charging the auxiliary capacitor with a predetermined charge, and the data line Data line driving means for holding at a predetermined potential may be provided.

  After the charge of all the auxiliary capacitors is released, the thin film transistors are sequentially turned on by the scanning line driving circuit after a predetermined time, and the amount of charge input from the auxiliary capacitor to the signal detection circuit through the data line is determined. It may be detected.

  A thin film transistor having a plurality of data lines, a plurality of scanning lines, a photosensitive semiconductor layer provided at an intersection of the data lines and the scanning lines, and a storage capacitor connected to the thin film transistors are formed over a transparent substrate. Also good.

  A transparent protective layer may be provided on the surface of the transparent substrate on which the thin film transistor is formed.

  A backlight may be provided on the surface of the transparent substrate opposite to the surface on which the thin film transistor is formed.

  A backlight and the backlight control means are provided, all the auxiliary capacitors are opened, the backlight is turned on for a certain time while a voltage is applied between the source and drain of the thin film transistor, and the scanning line is driven after the backlight is erased. The thin film transistors may be sequentially turned on by a circuit to detect the amount of charge input from the auxiliary capacitor to the signal detection circuit via the data line.

  In the two-dimensional image sensor, the data line, the scanning line, the thin film transistor, and the auxiliary capacitor may be formed on a transparent substrate.

  A transparent protective layer may be formed on the surface of the transparent substrate on the side where the thin film transistor is formed.

  A light irradiation means for irradiating light to the thin film transistor through the transparent substrate may be provided on the surface of the transparent substrate opposite to the surface on which the thin film transistor is formed.

  The light irradiation control means controls the light irradiation of the light irradiation means, and the light irradiation control means controls the light irradiation means to emit light for a predetermined time after the charge of the auxiliary capacitor is discharged. The photoelectric conversion amount detection means may stop the light irradiation after the light irradiation by the light irradiation means for a certain time, and detect the photoelectric conversion amount by the thin film transistor based on the charge of the auxiliary capacitor. .

  In the driving method of the two-dimensional image sensor having the above-described configuration, after all the auxiliary capacitors connected to the thin film transistors are charged, the scanning lines are driven to sequentially turn the thin film transistors into a conductive state. The photoelectric conversion amount of the thin film transistor may be detected based on the amount of charges.

  In the driving method of the two-dimensional image sensor having the above configuration, after the electric charge is discharged to all the auxiliary capacitors connected to each thin film transistor, the light irradiation unit performs light irradiation for a predetermined time, and then performs light irradiation. The thin film transistors may be sequentially turned on by stopping and driving the scanning lines, and the photoelectric conversion amount of the thin film transistors may be detected based on the charge amount of the auxiliary capacitor.

  In the photoelectric conversion amount detection method for detecting the photoelectric conversion amount of a photoelectric conversion element including a thin film transistor having a photosensitive semiconductor layer, the charge of the auxiliary capacitor connected to the drain electrode of the thin film transistor is released, and the thin film transistor is made non-conductive. In this state, while applying a voltage between the source and drain of the thin film transistor, the photosensitive semiconductor layer is irradiated with light for a predetermined time, and the photoelectric conversion amount of the photoelectric conversion element is based on the charge charged in the auxiliary capacitor. May be detected.

  As a result, all the charge of the auxiliary capacitor is released in advance, and the charge is charged in the auxiliary capacitor by light irradiation, so that the photoelectric conversion amount can be determined from the charge of the auxiliary capacitor.

  By detecting the charge charged in the auxiliary capacitor in this way, the circuit structure can be simplified by detecting the photoelectric conversion amount as compared with the case where the photocurrent itself generated at the time of light irradiation is detected. it can.

  In this manner, by simplifying the pixel structure that constitutes the photosensor, the photosensor itself can be reduced, and as a result, high resolution can be achieved. In addition, since the pixel structure of the photosensor is simplified, it is possible to simplify the manufacturing process of the photoelectric conversion device using the photosensor.

  In addition, since the charge is charged after all the charge of the auxiliary capacitor is released, if the charge is charged by light irradiation after the charge is discharged, the charge remaining in the auxiliary capacitor shows an accurate photoelectric conversion amount. As a result, the detection accuracy of the photoelectric conversion amount can be improved.

  In addition, since the charge accumulated in the auxiliary capacitor is released before the auxiliary capacitor is charged, that is, before the photoelectric conversion amount is detected, the charge related to the previous detection information does not remain. . For this reason, it is possible to detect an appropriate photoelectric conversion amount even if the detection operation is repeatedly performed. That is, there is an effect that it is possible to perform a repeated detection operation.

  A photoelectric conversion element having a thin film transistor having a photosensitive semiconductor layer; an auxiliary capacitor connected to a drain electrode of the thin film transistor; and a photoelectric conversion amount detected by the photoelectric conversion element connected to a source electrode of the thin film transistor. And a photoelectric conversion amount detecting means for applying a voltage between a source and a drain of the thin film transistor when the charge of the auxiliary capacitor is released and the thin film transistor is in a non-conductive state, and to the photosensitive semiconductor layer. The photoelectric conversion amount detecting means may be configured to detect the photoelectric conversion amount of the photoelectric conversion element based on the charge of the auxiliary capacitor.

  Thus, if the charge of the auxiliary capacitor is released in advance, the charge is charged in the auxiliary capacitor by light irradiation, and the photoelectric conversion amount can be found from the charge of the auxiliary capacitor.

  Thus, by detecting the charge of the auxiliary capacitor, the structure of the circuit can be simplified by detecting the photoelectric conversion amount as compared with the case of detecting the photocurrent itself generated during light irradiation.

  In this manner, by simplifying the pixel structure that constitutes the photosensor, the photosensor itself can be reduced, and as a result, high resolution can be achieved. In addition, since the pixel structure of the photosensor is simplified, it is possible to simplify the manufacturing process of the photoelectric conversion device using the photosensor.

  The photoelectric conversion amount detection means may include an amplifier circuit that amplifies the charge transferred from the auxiliary capacitor.

  In this case, since the charge can be amplified even if the amount of the charge remaining in the auxiliary capacitor is small, there is an effect that the photoelectric conversion amount can be accurately detected.

  Further, in the image input method for inputting, as image information, a photocurrent generated by reflected light from an original image converted by a photoelectric conversion element including a thin film transistor having a photosensitive semiconductor layer, an auxiliary capacitor connected to the drain electrode of the thin film transistor The photosensitive semiconductor layer is irradiated with light for a predetermined time while a voltage is applied between the source and drain of the thin film transistor, and the light is applied to the photosensitive semiconductor layer for a predetermined time. After the time irradiation, the configuration may be such that the photoelectric conversion amount of the photoelectric conversion element is detected based on the charge charged in the auxiliary capacitor, and the detection result is input as image information.

  Thus, after the charge is released in advance to the auxiliary capacitor, the charge due to light irradiation is charged. Therefore, if the charge amount of the auxiliary capacitor is finally obtained, the accumulated charge amount (photoelectric conversion amount) Can be detected.

  If the amount of charge detected in this way is the photoelectric conversion amount, it is possible to appropriately detect the photocurrent. Therefore, if this photoelectric conversion amount is the image information, accurate image information can be input. There is an effect that can be.

  A plurality of photoelectric conversion devices having the above-described configuration are arranged corresponding to the document image, and an image information output unit that outputs the photoelectric conversion amount of the photoelectric conversion element detected by each photoelectric conversion device as input image information of the document image May be provided.

  In this case, an image input device with high resolution can be realized by using the photoelectric conversion device having the above-described configuration, so that the image information output unit can output high-definition input image information.

  In the image input device, the photoelectric conversion device may be arranged one-dimensionally or two-dimensionally.

  When the photoelectric conversion device is arranged one-dimensionally, there is an effect that the photoelectric conversion device can be suitably used for a portable image input device such as a handy scanner used in a home facsimile machine.

  Further, when the photoelectric conversion device is two-dimensionally arranged, it is preferably used for a flat head scanner or the like. In this case, the entire original image can be read at once.

  The two-dimensional image sensor realized by using the photoelectric conversion device having the above configuration includes a plurality of data lines, a plurality of scanning lines intersecting with the data lines, and photosensitivity provided at intersections of the data lines and the scanning lines. A photoelectric conversion element including a thin film transistor having a semiconductor layer, an auxiliary capacitor connected to the drain electrode of the thin film transistor and charged with electric charge, and a photoelectric sensor connected to the source electrode of the thin film transistor and detecting the photoelectric conversion amount by the thin film transistor. A conversion amount detection unit; and an image information output unit that outputs a result detected by the photoelectric conversion amount detection unit as image information. The auxiliary capacitor is free of electric charge, and the thin film transistor is in a non-conductive state. To the photosensitive semiconductor layer while applying a voltage between the source and drain of the thin film transistor. Charge is charged by light irradiation, and the photoelectric conversion amount detection means detects the photoelectric conversion amount of the photoelectric conversion element based on the charge charged in the auxiliary capacitor after the light irradiation to the photosensitive semiconductor layer is completed. It may be configured to.

  As a result, it is possible to read a two-dimensional image with a simple configuration.

  In the two-dimensional image sensor, the data line, the scanning line, the thin film transistor, and the auxiliary capacitor may be formed on a transparent substrate.

  A transparent protective layer may be formed on the surface of the transparent substrate on the side where the thin film transistor is formed.

  A light irradiation means for irradiating light to the thin film transistor through the transparent substrate may be provided on the surface of the transparent substrate opposite to the surface on which the thin film transistor is formed.

  A light irradiation control unit configured to control light irradiation of the light irradiation unit, and the light irradiation control unit performs the light irradiation so as to perform light irradiation for a predetermined time after a predetermined amount of charge is released to the auxiliary capacitor; And the photoelectric conversion amount detection means stops the light irradiation after the light irradiation by the light irradiation means for a certain period of time, and detects the photoelectric conversion amount by the thin film transistor based on the charge of the auxiliary capacitor. May be.

  In the driving method of the two-dimensional image sensor having the above-described configuration, a voltage is applied between the source and the drain of the thin film transistor when the charge of all the auxiliary capacitors connected to each thin film transistor is released and the thin film transistor is non-conductive. After the charge is charged by irradiating the photosensitive semiconductor layer, the thin film transistors are sequentially turned on by driving the scanning line, and the photoelectric conversion amount of the thin film transistor is determined based on the charge amount of the auxiliary capacitor. You may make it detect.

  In the driving method of the two-dimensional image sensor having the above-described configuration, after the charge of all the auxiliary capacitors connected to each of the thin film transistors is released, the light irradiation unit performs light irradiation for a certain period of time, and then performs light irradiation. The thin film transistors may be sequentially turned on by stopping and driving the scanning lines, and the photoelectric conversion amount of the thin film transistors may be detected based on the charge amount of the auxiliary capacitor.

  In any of the above driving methods, there is an effect that the photoelectric conversion amount can be accurately detected.

  The image input method of the present invention is the image input method for inputting, as image information, a photocurrent generated by reflected light from an original image converted by a photoelectric conversion element including a thin film transistor having a photosensitive semiconductor layer. The charge of the auxiliary capacitor connected to is released, and after the charge release of the auxiliary capacitor is completed, the thin film transistor is turned off to irradiate the photosensitive semiconductor layer with light for a predetermined time, and the photosensitive semiconductor layer is irradiated with light. After a predetermined time, the photoelectric conversion amount of the photoelectric conversion element is detected based on the charge of the auxiliary capacitor, and the detection result is input as image information.

  According to the above configuration, the photoelectric conversion amount can be obtained by appropriately detecting the photocurrent. Therefore, if this photoelectric conversion amount is used as image information, accurate image information is transmitted to an information processing apparatus such as a computer. Can be entered.

  The image input apparatus according to the present invention includes a plurality of photoelectric conversion apparatuses having the above-described configuration corresponding to a document image, and the photoelectric conversion amount of the photoelectric conversion element detected by each photoelectric conversion apparatus is input to the input image of the document image. Image information output means for outputting information is provided.

  In this case, an image input device with high resolution can be realized by using the photoelectric conversion device having the above-described configuration, so that the image information output unit can output high-definition input image information.

  In the image input device, the photoelectric conversion device may be arranged one-dimensionally or two-dimensionally.

  When the photoelectric conversion device is arranged one-dimensionally, the photoelectric conversion device can be suitably used for a portable image input device such as a handy scanner used in a home facsimile machine.

  Further, when the photoelectric conversion device is two-dimensionally arranged, it is suitably used for a flat bed scanner or the like. In this case, the entire document image can be read at once.

  The two-dimensional image sensor realized by using the photoelectric conversion device having the above configuration includes a plurality of data lines, a plurality of scanning lines intersecting with the data lines, and photosensitivity provided at intersections of the data lines and the scanning lines. A thin film transistor having a semiconductor layer, an auxiliary capacitor connected to the drain electrode of the thin film transistor and charged with charge, a photoelectric conversion amount detecting means connected to the source electrode of the thin film transistor and detecting the photoelectric conversion amount by the thin film transistor; Image information output means for outputting the result detected by the photoelectric conversion amount detection means as image information, and the auxiliary capacitor has the photosensitivity when the electric charge is discharged and the thin film transistor is in a non-conductive state. Charges are charged by light irradiation to the semiconductor layer, and the photoelectric conversion amount detection means is provided on the photosensitive semiconductor layer. Based on the charge of the auxiliary capacitor after irradiation completion may be configured to detect a photoelectric conversion of the photoelectric conversion element.

  INDUSTRIAL APPLICABILITY The photoelectric conversion amount detection method and photoelectric conversion apparatus of the present invention can be used in an apparatus that outputs an image to an information processing apparatus such as a personal computer or a facsimile, and obtains image information from the original by irradiating the original with light. It can utilize suitably also for.

It is a schematic block diagram which shows the principal part structure of the photoelectric conversion apparatus of this invention, and is a schematic block diagram which shows the structure for 1 pixel of the photoelectric conversion apparatus with which the voltage of the electrode connected to the drain side of TFT is variable. It is a schematic block diagram which shows the structure of the two-dimensional image sensor using the photoelectric conversion apparatus shown in FIG. 1 as a photosensor. It is a schematic perspective view which shows the external appearance of the two-dimensional image sensor shown in FIG. It is sectional drawing which shows schematically the pixel structure of the photoelectric conversion element of this invention. 2 is a timing chart illustrating an operation of the photoelectric conversion device illustrated in FIG. 1. It is a graph which shows the gate voltage-drain current characteristic of the thin-film transistor provided with the slow-release semiconductor layer shown in FIG. It is a schematic block diagram which shows the principal part structure of the other photoelectric conversion apparatus of this invention, and is a schematic block diagram which shows the structure for 1 pixel of the photoelectric conversion apparatus with which the voltage of the electrode connected to the source side of TFT is variable. . 8 is a timing chart illustrating an operation of the photoelectric conversion device illustrated in FIG. 7. It is a schematic block diagram which shows the principal part structure of the further another photoelectric conversion apparatus of this invention, and is a schematic block diagram which shows the structure for 1 pixel of the photoelectric conversion apparatus with which the voltage of both the source side and drain side of TFT is variable. . 10 is a timing chart illustrating an operation of the photoelectric conversion apparatus illustrated in FIG. 9. It is explanatory drawing which shows more specifically the circuit structure of the photoelectric conversion apparatus shown in FIG. It is a circuit diagram which shows the structure of the conventional photosensor.

Explanation of symbols

2 Irradiation light (light)
7 TFT (Thin Film Transistor)
10 Source electrode 11 Bottom gate electrode (gate electrode)
12 Semiconductor layer (photosensitive semiconductor layer)
15 Drain electrode 17 Auxiliary capacitor 18 Backlight unit (light source)
19 Drive IC (Drive circuit)
20 Sensor substrate (pixel unit)
21 Driving Printed Circuit Board 22 Gate Line 23 Data Line 24 Control / Communication Unit (Control Unit)
25 Detection IC (photoelectric conversion amount detection means)
28 drive unit 29 detection unit 31 control unit 32 reference electrode unit (potential difference generation means, second voltage application means)
33 Integration amplifier (opening means, detection circuit)
35 Amplification amplifier 39 Feedback capacity (opening means, capacity)
40 CS electrode driver (potential difference generating means, first voltage applying means)
S source electrode D drain electrode

Claims (11)

In a photoelectric conversion amount detection method for detecting a photoelectric conversion amount of a photoelectric conversion element including a thin film transistor having a photosensitive semiconductor layer,
The charge of the auxiliary capacitor connected to the drain electrode of the thin film transistor is released before light is received, and the charge generated when the photosensitive semiconductor layer receives the light is made nonconductive with the thin film transistor being in the auxiliary state. Charging process to charge the capacity;
After the charging step, a photoelectric conversion amount detection step for detecting the photoelectric conversion amount based on the charge of the auxiliary capacitor;
A photoelectric conversion amount detection method comprising: A photoelectric conversion element in which photoelectric conversion elements including a thin film transistor having a photosensitive semiconductor layer are arranged one-dimensionally or two-dimensionally, and a detection unit that detects a photoelectric conversion amount of the photoelectric conversion element is provided outside the pixel part. In the conversion device,
In the pixel portion, an auxiliary capacitor for charging a charge generated when the photosensitive semiconductor layer of the thin film transistor in a non-conductive state receives light is connected to the drain electrode of the thin film transistor,
The photoelectric conversion device, wherein the detection unit is provided with photoelectric conversion amount detection means for detecting the photoelectric conversion amount based on the charge charged in the auxiliary capacitor.   3. The photoelectric conversion device according to claim 2, wherein an opening means for previously releasing the charge of the auxiliary capacitor is provided outside the pixel portion in preparation for the photosensitive semiconductor layer to receive light. .   3. The photoelectric device according to claim 2, wherein a potential difference generating means for generating a potential difference between a source electrode and a drain electrode of the thin film transistor when the photosensitive semiconductor layer receives light is provided outside the pixel portion. Conversion device.   The potential difference generating means includes first voltage applying means for generating a potential difference by applying a voltage to an electrode opposite to an electrode connected to a drain electrode of the thin film transistor among electrodes constituting the auxiliary capacitor. The photoelectric conversion device according to claim 4, wherein   5. The photoelectric conversion device according to claim 4, wherein the potential difference generating means includes second voltage applying means for generating the potential difference by changing a voltage of a source electrode of the thin film transistor.   The potential difference generating means includes a first voltage applying means for applying a voltage to an electrode opposite to an electrode connected to the drain electrode of the thin film transistor among electrodes constituting the auxiliary capacitor, and a voltage of the source electrode of the thin film transistor. 5. The photoelectric conversion device according to claim 4, further comprising a second voltage applying unit that changes the potential difference, wherein the potential difference is generated by the cooperation of the first voltage applying unit and the second voltage applying unit. Further, a driving circuit for controlling on / off of the thin film transistor is provided outside the pixel portion,
The photoelectric conversion amount detection means detects the photoelectric conversion amount based on a capacitor that temporarily captures the charge accumulated in the auxiliary capacitor when the driving circuit turns on the thin film transistor, and the charge of the capacitor. 4. The photoelectric conversion device according to claim 3, wherein the detection circuit and the capacitor also serve as the opening means.   3. The photoelectric conversion device according to claim 2, further comprising a driving circuit provided outside the pixel portion for applying a negative voltage to the gate electrode of the thin film transistor so that the thin film transistor is turned off when receiving light. Furthermore, a light source that emits light that is a source of light including image information received by the photosensitive semiconductor layer;
Control means for stopping light emission of the light source while the photoelectric conversion amount detection means detects the photoelectric conversion amount;
The photoelectric conversion device according to claim 2, further comprising:   A photoelectric conversion device according to any one of claims 2 to 10, comprising: a signal corresponding to image information contained in light irradiated on the photoelectric conversion device, based on a photoelectric conversion amount detected by the photoelectric conversion device. An information output device characterized by generating and outputting.

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