JP2001211389A - Photosensor system and sensitivity setting method thereof - Google Patents

Abstract

(57) [Problem] To provide a photo sensor system and a sensitivity setting method thereof, in a two-dimensional sensor system, which can appropriately set an optimum sensitivity for properly reading a subject image under various environments. . SOLUTION: An image reading sensitivity of a photo sensor array 100 is changed for each row, a pre-reading operation for reading a subject image is executed, and the read image data is changed to an abnormal value removing unit 12.
4 to remove high-frequency components (outliers) by the Fourier transform, and based on the measured data from which the outliers have been removed, the data comparator 124 and the adder 125 determine the dynamic range of the brightness data of each row and its primary range. The differential value is calculated, and the image reading sensitivity set in the row where the dynamic range is maximized and the primary differential value of the dynamic range is the minimum is extracted and set as the reading sensitivity in the normal image reading operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photosensor system and a sensitivity setting method thereof, and more particularly, to a photosensor having a photosensor array formed by two-dimensionally arranging photosensors using thin film transistors having a so-called double gate structure. The present invention relates to a sensor system and a sensitivity setting method thereof.

[0002]

2. Description of the Related Art Conventionally, as a two-dimensional image reading device for reading the shape of a fine unevenness such as a printed matter, a photograph, or a fingerprint, a photo-sensor constituted by arranging photoelectric conversion elements (photo sensors) in a matrix. There is a structure having a sensor array. As such a photo sensor array,
Generally, a solid-state imaging device such as a CCD (Charge Coupled Device) is used. CCD is, as is well known,
Photodiodes and thin film transistors (TFT: ThinFi
lm Transistor) are arranged in a matrix, and the charge amount of electron-hole pairs generated corresponding to the amount of light applied to the light receiving portion of each photo sensor is determined by a horizontal scanning circuit and a vertical scanning circuit. The luminance of the irradiation light is detected by the scanning circuit.

In a photosensor system using such a CCD, it is necessary to separately provide a selection transistor for setting each scanned photosensor to a selected state. However, there is a problem that the size is increased. In recent years, as a configuration for solving such a problem, a thin film transistor having a so-called double gate structure (hereinafter, referred to as a double gate type photo sensor) in which a photo sensor itself has a photo sensing function and a selection transistor function. Attempts have been made to apply) to a photosensor system to reduce the size of the system and increase the density of pixels.

[0004] Such a photosensor system generally forms a photosensor array by forming a double-gate photosensor having a top gate electrode and a bottom gate electrode on one side of a glass substrate in a matrix. Irradiates light from a light source provided on the back side of the glass substrate, and reflects reflected light corresponding to an image pattern of a two-dimensional image such as a fingerprint placed above the photosensor array to a double-gate photosensor. , And detects two-dimensional images as light / dark information. Here, the image reading operation by the photosensor array is performed by the carrier (positive) accumulated for each double gate photosensor during the light accumulation period from the end of the initialization by the application of the reset pulse to the application of the read pulse. Brightness information is detected based on the accumulated amount of holes. The specific configuration and operation of the double-gate transistor and the photosensor array will be described later.

[0005]

However, the prior art as described above has the following problems. That is, in a sensor system to which a double-gate photosensor is applied, an image is read based on the amount of carriers (holes) accumulated for each photosensor during the light accumulation period. In order to read (two-dimensional images) satisfactorily, it is necessary to appropriately set the light accumulation period (that is, equivalent to the reading sensitivity). Here, the appropriate light accumulation period is
Conventionally, a circuit for detecting the ambient illuminance is provided separately, or a standard sample is placed on the detection surface before the normal scanning operation is started, since it differs depending on the surrounding conditions such as the ambient illuminance. Then, a reading operation (so-called pre-reading operation) is performed by changing the light accumulation period into a plurality of stages, and based on the detection result and the reading result, an optimum light accumulation period according to surrounding conditions such as environmental illuminance is obtained. Technique was adopted.

However, a sensitivity setting method for uniquely and satisfactorily setting an appropriate light accumulation period based on a reading result for each light accumulation period obtained by such a pre-read operation has not yet been developed. Was. In particular, in a case where a change in ambient light or a change in the characteristics of the photosensor has occurred, or in a case where a foreign substance has adhered to the detection surface or an element defect has occurred in the photosensor, it is obtained by the pre-read operation. If the reading result for each light accumulation period is used as it is, an appropriate light accumulation period will not be set, which hinders a good reading operation of the subject image. For example, when the photosensor system is applied to a fingerprint reading device However, there is a problem that a malfunction occurs in the fingerprint recognition processing.

Accordingly, the present invention solves the above-described problems, and in a two-dimensional sensor system, a photosensor system and a photosensor system capable of appropriately setting the optimum sensitivity for reading a subject image satisfactorily under various environments. It is an object to provide a sensitivity setting method.

[0008]

According to a first aspect of the present invention, there is provided a photo sensor system comprising a photo sensor array configured by two-dimensionally arranging photo sensors, and changing the image reading sensitivity for setting the image reading sensitivity. In a photo sensor system that performs a pre-reading operation while reading a subject image, an abnormal value that deviates from a main change tendency of the measured value among predetermined measurement amounts related to the image pattern of the subject image at each of the image reading sensitivities. An abnormal value removing means for removing the image reading sensitivity based on the measured value from which the abnormal value has been removed; and an image reading sensitivity extracting means for extracting the image reading sensitivity suitable for the reading operation of the subject image. Reading sensitivity setting means for setting the sensitivity during a normal reading operation of the subject image.

According to a second aspect of the present invention, there is provided a photo sensor system comprising:
2. The photosensor system according to claim 1, wherein the reading sensitivity extracting means has a maximum data range of the measured value from which the abnormal value has been removed, and a minimum displacement of the data range between the image reading sensitivities. The image reading sensitivity is extracted as follows. Claim 3
The photosensor system according to claim 1, wherein in the photosensor system according to claim 1, the abnormal value removing unit performs a Fourier transform on the predetermined measurement amount, and converts a predetermined high-frequency component from the frequency-converted measurement amount. It is characterized in that the abnormal value is removed by removing.
The photosensor system according to claim 4 is the photosensor system according to claim 1, wherein the pre-reading operation of the subject image includes an image reading sensitivity that varies stepwise for each row of the subject image to the photosensor array. It is set and executed.

[0010] The photosensor system according to claim 5 is
2. The photo sensor system according to claim 1, wherein the predetermined measurement amount is brightness data corresponding to an image pattern of the subject image. According to a sixth aspect of the present invention, in the photo sensor system according to the first aspect, the image reading sensitivity of the photo sensor array is set and controlled by adjusting a light accumulation period of the photo sensor. I have. The photosensor system according to claim 7 is a photosensor system according to claim 1.
6. The photosensor system according to any one of claims 1 to 5, wherein the photosensor system applies a first signal voltage for optimizing an effective voltage applied to a first electrode in the photosensor array. And an effective voltage adjusting means for applying a second signal voltage for setting an effective voltage applied to a second electrode in the photosensor array to an optimum value.

[0011] The photosensor system according to claim 8 is
7. The photosensor system according to claim 1, wherein the photosensor has a source electrode and a drain electrode formed with a channel region made of a semiconductor layer interposed therebetween, and at least above and below the channel region. 8. A top gate electrode and a bottom gate electrode formed through an insulating film, and having one of the top gate electrode or the bottom gate electrode as a light irradiation side, and light emitted from the light irradiation side. It is characterized in that a charge corresponding to the amount is generated and accumulated in the channel region. A sensitivity setting method for a photo sensor system according to a ninth aspect includes a photo sensor array configured by two-dimensionally arranging photo sensors, and reads a subject image while changing the image reading sensitivity for setting the image reading sensitivity. In the sensitivity setting method of the photo sensor system performing the pre-reading operation, in a predetermined measurement amount related to the image pattern of the subject image at each of the image reading sensitivities, an abnormal value deviating from a main change tendency of the measurement value is determined. A removing step, a step of extracting the image reading sensitivity suitable for the reading operation of the subject image based on the measurement value from which the abnormal value is removed, and a step of extracting the extracted image reading sensitivity of the subject image. And setting at the time of a regular reading operation.

According to a tenth aspect of the present invention, in the sensitivity setting method for the photosensor system according to the ninth aspect, the step of extracting the image reading sensitivity comprises the step of extracting the image reading sensitivity. This is performed by extracting the image reading sensitivity at which the value data range becomes maximum and the displacement between the image reading sensitivities of the data range becomes minimum. The sensitivity setting method of the photosensor system according to claim 11,
9. The sensitivity setting method for a photo sensor system according to claim 8, wherein the step of removing an abnormal value from the predetermined measurement amount includes performing a Fourier transform on the predetermined measurement amount and performing a predetermined conversion from the frequency-converted measurement amount. , By removing the high-frequency components of

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a photosensor system and a sensitivity setting method thereof according to the present invention will be described in detail. First, a double-gate transistor applied to a photosensor system according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view showing the structure of a double-gate transistor. FIG.
(A) As shown in FIG.
Is a semiconductor layer (channel layer) 11 made of amorphous silicon or the like in which electron-hole pairs are generated when visible light is incident.
If, respectively ^{n +} silicon layers 17 and 18 provided at both ends of the semiconductor layer 11, a source electrode 12 and drain electrode 13 formed on the ^{n +} silicon layers 17 and 18, the upper (drawing above the semiconductor layer 11 ), A top gate electrode 21 formed via a block insulating film 14 and an upper (top) gate insulating film 15, and a lower (bottom) gate insulating film 16 below (below the drawing) the semiconductor layer 11. And a bottom gate electrode 22.

In FIG. 1A, the top gate electrode 21, the top gate insulating film 15, the bottom gate insulating film 16, and the protective insulating film 20 provided on the top gate electrode 21 are all semiconductor layers 11 The bottom gate electrode 22 is made of a material that blocks transmission of visible light, so that only the incident light from above is detected. The structure has That is, the double-gate photosensor 10 uses the semiconductor layer 11 as a common channel region, the upper MOS transistor formed by the semiconductor layer 11, the source electrode 12, the drain electrode 13, and the top gate electrode 21, the semiconductor layer 11, the source Electrode 12, drain electrode 13, and bottom gate electrode 22
Consisting of a lower MOS transistor formed by
A structure in which two MOS transistors are combined is formed on a transparent insulating substrate 19 such as a glass substrate. And such a double gate type photo sensor 10 is:
Generally, it is represented by an equivalent circuit as shown in FIG. Here, TG is a top gate terminal, BG is a bottom gate terminal, S is a source terminal, and D is a drain terminal.

Next, a photo sensor system configured by two-dimensionally arranging the above-described double gate type photo sensors will be briefly described with reference to the drawings. FIG. 2 is a schematic configuration diagram of a photosensor system configured by two-dimensionally arranging double-gate photosensors. As shown in FIG. 2, the photosensor system is roughly divided into a photosensor array 100 in which a large number of double-gate photosensors 10 are arranged in a matrix of, for example, n rows × m columns.
A top gate line 101 and a bottom gate line 10 in which the top gate terminal TG and the bottom gate terminal BG of each double gate type photosensor 10 are connected in the row direction, respectively.
2 and a top gate driver 111 connected to the top gate line 101 and the bottom gate line 102, respectively.
And a bottom gate driver 112, a data line 103 connecting the drain terminals D of the respective double-gate photosensors in the column direction, and an output circuit unit 113 connected to the data line 103. Where φtg
And φbg are reset pulses φT1, φT2,
... ΦTn,... ΦTn, and readout pulses φB1, φB
Control signals for generating B2,... ΦBi,.
φpg is a precharge signal for controlling the timing of applying the precharge voltage Vpg.

In such a configuration, a photo sensing function is realized by applying a voltage from the top gate driver 111 to the top gate terminal TG, and a voltage is applied from the bottom gate driver 112 to the bottom gate terminal BG, and the data line 103 is applied. The detection signal is taken into the output circuit unit 113 via the
t) implements the selective read function.

Next, a drive control method of the above-described photo sensor system will be described with reference to the drawings. FIG.
FIG. 4 is a timing chart showing an example of a drive control method of the photo sensor system. FIG. 4 is a conceptual diagram of the operation of the double gate type photo sensor, and FIG. 5 shows the optical response characteristics of the output voltage of the photo sensor system. FIG. First, in the reset operation, as shown in FIGS. 3 and 4A, a pulse voltage (reset pulse; for example, a high level of Vtg = + 15 V) φTi is applied to the top gate line 101 of the i-th row, Carriers (holes) accumulated in the semiconductor layer of each double gate photosensor 10
(Reset period Treset).

Next, in the light accumulation operation, as shown in FIGS. 3 and 4B, a low level (for example, Vtg = −15 V) bias voltage φT is applied to the top gate line 101.
By applying i, the reset operation ends, and the light accumulation period Ta due to the carrier accumulation operation starts. In the light accumulation period Ta, carriers are accumulated in the channel region according to the amount of light incident from the top gate electrode side. 3 and 4 in the precharge operation.
As shown in (c), a predetermined voltage (precharge voltage) Vpg is applied to the data line 103 based on the precharge signal φpg in parallel with the light accumulation period Ta to cause the drain electrode 13 to hold a charge ( Precharge period Tprc
h).

Next, in the read operation, FIG.
As shown in FIG. 4D, after a precharge period Tprch has elapsed, a high-level (for example, Vbg = + 10 V) bias voltage (read selection signal; hereinafter, referred to as a read pulse) φBi is applied to the bottom gate line 102. As a result, the double gate photosensor 10 is turned on (readout period Tread). Here, in the read period Tread, the carriers (holes) accumulated in the channel region act in a direction of relaxing Vtg (−15 V) applied to the top gate terminal TG having the opposite polarity, so that the bottom gate terminal BG has Vbg forms an n-channel, and the data line voltage VD of the data line 103 tends to gradually decrease from the precharge voltage Vpg over time as shown in FIG. 5A according to the drain current.

That is, when the light accumulation state during the light accumulation period Ta is a dark state and no carriers (holes) are accumulated in the channel region, as shown in FIGS. 4 (e) and 5 (a). By applying a negative bias to the top gate TG, the positive bias of the bottom gate BG is canceled, the double gate type photosensor 10 is turned off, and the drain voltage, that is, the voltage VD of the data line 103 is held almost as it is. Will be. on the other hand,
When the light accumulation state is a bright state, FIGS.
As shown in (a), since carriers (holes) corresponding to the amount of incident light are trapped in the channel region, they act to cancel the negative bias of the top gate TG, and the bottom gate BG is reduced by the amount of the cancellation. The positive bias of
The double gate type photo sensor 10 is turned on. Then, the voltage VD of the data line 103 decreases in accordance with the ON resistance according to the amount of incident light.

Therefore, as shown in FIG.
The change tendency of the voltage VD of the data line 103 is determined by the time from the end of the reset operation due to the application of the reset pulse φTi to the top gate TG to the application of the read pulse φBi to the bottom gate BG (light accumulation period Ta).
In the case where the amount of accumulated carriers is small, the amount tends to decrease gradually, and when the amount of accumulated carriers is large, the amount tends to decrease sharply. Therefore, by detecting the voltage VD of the data line 103 after a predetermined time has elapsed after the start of the read period Tread, or detecting the time until the voltage reaches the voltage with reference to a predetermined threshold voltage. By doing so, the amount of irradiation light is converted.

The above-described series of image reading operations is defined as one cycle, and the same processing procedure is repeated for the double-gate photosensor 10 in the (i + 1) -th row, thereby making the double-gate photosensor 10 a two-dimensional sensor system. Can work. In the timing chart shown in FIG. 3, the precharge period Tprch
After a lapse of time, as shown in FIGS. 4F and 4G, when a state where a low level (for example, Vbg = 0 V) is applied to the bottom gate line 102 is continued, the double gate type photosensor 10 keeps the OFF state. Then, as shown in FIG. 5B, the voltage VD of the data line 103 holds the precharge voltage Vpg. Thus, the bottom gate line 1
The selection function of selecting the read state of the double-gate photosensor 10 is realized by the application state of the voltage 02.

Next, an embodiment of a photosensor system according to the present invention will be described with reference to the drawings. In the embodiment described below, the above-described double-gate photosensor is applied as the photosensor, and a voltage is applied using the top gate electrode as the first electrode, thereby realizing a photosense function, and The description will be made on the assumption that a function of reading out the amount of charge accumulated in the channel region by applying a voltage using the gate electrode as a second electrode is realized. FIG. 6 is a schematic configuration diagram illustrating an example of a two-dimensional image reading device to which the photo sensor system according to the present invention is applied. Note that here, description will be made with reference to the configurations of the double-gate photosensor and the photosensor system shown in FIGS. 1 and 2 as appropriate. Also,
The same components as those of the photo sensor system shown in FIG. 2 will be described with the same reference numerals.

As shown in FIG. 6, a two-dimensional image reading apparatus according to the present embodiment comprises a photo sensor array 100 in which the double gate type photo sensor 10 shown in FIG. A top gate driver 111 that applies a predetermined top gate voltage (reset pulse) to the top gate terminal TG of the photosensor 10 at a predetermined timing, and a bottom gate terminal BG of the double gate photosensor 10 at a predetermined timing. A bottom gate driver 112 for applying a predetermined bottom gate voltage (read pulse);
An output circuit unit 113 including a column switch 114, a precharge switch 115, and an amplifier 116 for applying a precharge voltage to 0 and reading a data line voltage.
An analog-to-digital converter (hereinafter referred to as an A / D converter) 117 for converting the read data voltage (analog signal) into image data composed of a digital signal;
In addition to controlling the reading operation of the subject image by the photosensor array 100 (image reading operation), exchanging data with the external function unit 200 for executing predetermined processing such as collation and processing of image data, etc. A controller 120 having a function of controlling execution of a removing operation, a reading sensitivity setting operation, and an effective voltage adjusting operation; and a RAM 130 for storing read image data, reading sensitivity setting, data related to effective voltage adjustment, and the like. It is configured to have.

Here, the photo sensor array 100, the top gate driver 111, and the bottom gate driver 11
2. The configuration including the output circuit unit 113 (the column switch 114, the precharge switch 115, and the amplifier 116) has substantially the same configuration and function as those of the photosensor system shown in FIG. Is omitted. The controller 120 is provided with the top gate driver 11
Control signals φtg, φ
By outputting bg, the top gate driver 111
And the bottom gate driver 112, the top gate terminal TG and the bottom gate terminal BG of each double gate type photo sensor constituting the photo sensor array 100.
A pre-charge voltage Vpg is applied to the data line by applying a predetermined signal voltage (reset pulse φTi, read-out pulse φBi) to the precharge switch 115 and outputting a control signal φpg to the data line. Control the execution of

The data line voltage VD read from the double gate type photo sensor 10 via the column switch 114 is supplied to the controller 120 by the amplifier 11.
6 and converted into a digital signal via the A / D converter 117 and input as image data. The controller 120 performs predetermined image processing on the image data, writes and reads the image data to and from the RAM 130, and performs a predetermined process such as collation and processing of the image data on the external function unit 200. It also has an interface function. Further, the controller 120
Is a control signal φtg output to the top gate driver 111 and the bottom gate driver 112, as will be described later.
By setting and controlling φbg, a reading sensitivity capable of optimally reading a subject image corresponding to environmental illuminance such as external light, that is, a function of setting an optimal light accumulation period Ta of the double-gate type photosensor 10, Further, it has a function of adjusting the bias of the effective voltage applied to the top gate TG and the bottom gate BG of the double gate photosensor 10 to an optimum value. Therefore, the controller 120
Constitutes an abnormal value removing unit, a reading sensitivity extracting unit, a reading sensitivity setting unit, and an effective voltage adjusting unit.

The configuration and operation of the controller applied to the photo sensor system according to the present invention will be described below.
This will be described in more detail with reference to the drawings. First, a specific device configuration of the controller will be described. FIG.
It is a block diagram showing an example of 1 composition of a controller applied to a photo sensor system concerning the present invention. As shown in FIG. 7, a controller 120 according to the present embodiment includes a device controller 121 that controls a gate driver 111A and switches 113A, and a data controller 122 that manages various data such as image data and writing and reading to and from a RAM 130. , These controllers 1
And a main controller 123 that supervises 21 and 122 and that interfaces with the external function unit 200.

Further, the controller 120 performs a Fourier transform section 124a for performing a Fourier transform on specific measurement data (measurement amount) based on image data input as a digital signal from the photo sensor array 100 via the A / D converter 117. A filter unit 124b for removing a high-frequency component corresponding to an abnormal value from the Fourier-transformed measurement data, and an inverse Fourier transform unit 124c for performing an inverse Fourier transform on the measurement data from which the high-frequency component has been removed. Unit (abnormal value removing means) 124 compares the magnitude of the measured data from which the abnormal value has been removed to extract the maximum value and the minimum value, and furthermore, a dynamic range (data of the measured data) calculated by an adder 126 described later. Data for extracting the maximum value of the range) and the minimum value of the displacement of the dynamic range. Comparator (reading sensitivity extraction means) 125
An adder 126 that calculates a dynamic range from a difference between the maximum value and the minimum value of the measurement data and calculates a difference between the dynamic ranges, that is, a first derivative (displacement of a data range); Converter 1
17, the measured data processed via the abnormal value removing unit 124, the data comparator 125, and the adder 126 are input, and these data are written to or read from the RAM as necessary, or the data comparator 125, A data selector 1 that controls switching of re-input to the adder 126, output to the external function unit 200 via the data controller 122, and the like.
27 and a control signal output from the device controller 121 to the top gate driver 111 and the bottom gate driver 112 so as to optimize the reading sensitivity of the photosensor array 100 based on the control signal from the data controller 122. And a sensitivity setting register (reading sensitivity setting means) 128.

Next, a method for setting the sensitivity of the photo sensor system according to the present invention will be described with reference to the drawings. FIG. 8 is a flowchart showing one processing procedure of the sensitivity setting method of the photo sensor system according to the present invention, and FIG.
4 is a timing chart illustrating an example of a sensitivity setting method of the photo sensor system according to the present invention. Here, FIG.
The sensitivity setting procedure will be described with reference to the configuration of the photosensor system shown in FIGS. 6 and 7 as appropriate. As shown in FIGS. 8 and 9, the sensitivity setting method of the photosensor system according to the present embodiment includes a reading sensitivity setting operation, an image reading operation, and an effective voltage adjustment operation. Controls each operation. Hereinafter, each processing operation will be specifically described.

<Reading Sensitivity Setting Operation> As shown in FIGS. 8 and 9, the reading sensitivity setting operation in this embodiment
Prior to the normal reading operation of the subject image, the main controller 123 controls via the data controller 122 to set the image reading sensitivity for the pre-reading operation in the sensitivity setting register 128, and performs the pre-reading operation of the subject image. Is started (procedure S101). In the pre-reading operation, similarly to the normal image reading operation, a series of processes of a reset operation, a light accumulation operation, a precharge operation, and a read operation is performed on each of the double-gate photosensors 10 constituting the photosensor array 100. It is performed by executing. In particular, in the present embodiment, for each of the top gate lines 101 connecting the top gate terminals TG of the double gate type photosensor 10 in the row direction,
... ΦTn are sequentially applied at time intervals of a predetermined delay time Tdly to reset the reset period Trs.
Start t and initialize the double-gate photosensor 10 for each row. Here, reset pulses φT1, φ
T2,... ΦTn are pulse signals having a high level of the signal voltage Vtgh and a low level of the signal voltage Vtgl, and have a low-level signal voltage except for the timing at which the high-level Vtgh reset pulses φT1, φT2,. Vtgl is being applied.

[0031] Then, when the reset period Trst ends, the light accumulating period _{TA 1, TA 2, ... TA} n is sequentially started, the channel region in accordance with the amount of light entering the double-gate photo-sensor 10 in each row Electric charges (holes) are generated and accumulated. Next, a precharge signal φpg and readout pulses φBn,... ΦB2, φB1 are sequentially applied to each of the data line 103 and the bottom gate line 102 at a time interval of a predetermined delay time Tdly.
The light accumulation periods TA ₁ , TA ₂ ,... TA _n set for each row
The voltage change VD corresponding to the electric charge accumulated in the RAM is read out via the output circuit unit 113 and sequentially stored in the RAM. Here, the read pulses φB1, φB2,.
Is a pulse signal with the high level being the signal voltage Vbgh and the low level being the signal voltage Vbgl. The low level signal voltage Vbgh is applied except at the timing when the high level Vbgh readout pulses φB1, φB2,. It is in the state where it was.

That is, the image reading sensitivity for the pre-reading operation is changed by changing the image reading sensitivity (that is, the light accumulation period of the double gate type photosensor 10) step by step for each row of the subject image to obtain a plurality of different sensitivities. Is set so that one image of the subject can be read. In particular, according to the pre-read operation shown in the present embodiment, the light accumulation periods TA ₁ , TA ₂ ,..., TA _n set for each row are different from each other by a predetermined delay time Tdly of two.
Since the image data is increased at double time intervals, image data read with a reading sensitivity set with a sensitivity adjustment width equal to or more than the number of lines by a reading operation of one screen can be obtained. The image reading sensitivity for each row is associated with the row number, for example, in a table format (row number-image reading sensitivity correspondence table).
It is stored in M130. Next, the image data read by the above-described pre-read operation is supplied to the amplifier 115 and A
The signal is converted into a digital signal via the / D converter 116 (step S102), and is input to the abnormal value removing unit 124 as brightness data corresponding to the brightness pattern of the subject image.

The brightness data (predetermined measurement amount) input to the abnormal value removing unit 124 is first subjected to Fourier transform in the Fourier transform unit 124a based on the contrast (data range) of the brightness data for each row. Then, a frequency distribution representing the variation width (amplitude) of the brightness data for each row number is obtained (step S103). Next, high frequency components equal to or higher than a predetermined value are removed from the converted frequency distribution. Specifically, for example, a predetermined high-frequency component is removed by passing through a filter unit 124b configured by a low-pass filter (step S104). Further, the frequency distribution from which the high-frequency component has been removed is subjected to inverse Fourier transform by the inverse Fourier transform unit 124c, whereby the contrast for each row number is obtained again (step S105). By such a series of abnormal value removing operations by the abnormal value removing unit 124, an abnormal value having a high frequency component from the original brightness data, that is, having a steep fluctuation and deviating from a main change tendency of the brightness data, is removed. Only components that change smoothly with respect to the row number (major change tendency) are extracted. The brightness data from which the abnormal value has been removed is input to the data comparator 125.

Next, from the brightness data from which the abnormal value has been removed, the maximum value and the minimum value are extracted for each row by the data comparator 125 and output to the adder 126 (step S1).
06). Here, in the extraction processing of the maximum value and the minimum value of the brightness data, specifically, the interval between white and black in the brightness pattern of the subject image is divided and set to, for example, 256 gradations, and the maximum value included in each row is set. This is performed by extracting brightness data indicating the value (pixels having the lightest gradation) and brightness data indicating the minimum value (pixels having the darkest gradation). Then, the adder 126 calculates the difference between the maximum value and the minimum value of the brightness data of each row, that is, the dynamic range, and outputs the result via the data selector 127.
The information is temporarily stored in the RAM 130. Such dynamic range calculation processing is executed for all rows (procedure S
107). Next, the dynamic range of each row stored in the RAM 130 is read out via the data selector 127 and input to the adder 126 again to calculate the difference (first-order differential value) of the dynamic range between adjacent rows. This result is output via the data selector 127 to the RA
It is stored in M130 (procedure S108).

The data group of the dynamic range for each row stored in the RAM 130 and the data group of the primary differential value of the dynamic range are stored in the data selector 12.
7 and input to the data comparator 125,
A row number at which the dynamic range is maximum and the first derivative of the dynamic range is minimum, that is, 0 or the row number closest to 0 is extracted (step S109). And
Based on the extracted line number, refer to the line number-image reading sensitivity correspondence table stored in the RAM 130,
The image reading sensitivity set in the row, that is, the light accumulation period of the double gate type photo sensor is extracted (step S110). Next, the main controller 123 sends the sensitivity setting register 12 via the data controller 122.
8 to control the image reading sensitivity extracted from the line number-image reading sensitivity correspondence table, thereby terminating the sensitivity setting process based on the pre-reading operation (step S111).

<Image Reading Operation> Next, a normal image reading operation of the subject image is executed using the optimum light accumulation time Ta determined by the above-described reading sensitivity setting operation (step S112). That is, as shown in FIG. 9, the top gate terminal TG of the double gate type photo sensor 10
, .Phi.Tn are sequentially applied to each of the top gate lines 101 connecting in the row direction, and the reset period Trst is started to initialize the double-gate photosensor 10 for each row. Here, the reset pulses φT1, φT2,..., ΦTn are pulse signals of the signal voltage Vtgh at the high level, the signal voltage Vtgl at the low level, and the reset pulses φT1, φT2 of the high level Vtgh, as in the above-described pre-read operation. , ... φTn
Is applied, the low-level signal voltage Vtgl is applied.

Next, reset pulses φT1, φT2,
... The falling of φTn and the end of the reset period Trst sequentially start the optimum light accumulation period Ta for each row, according to the amount of light incident from the top gate electrode side of the double gate type photosensor 10. As a result, charges (holes) are generated and accumulated in the channel region. Here, as shown in FIG. 9, the precharge period Tprch is started by applying the precharge signal φpg in parallel with the light accumulation period Ta, and the precharge voltage Vprch is applied to the data line 103. A precharge operation for holding a predetermined voltage at the drain electrode of the double-gate photosensor 10 is performed.

Then, the bottom gate line 102 is provided for each row with respect to the double gate type photosensor 10 in which the optimal light accumulation period Ta and the precharge period Tprch have been completed.
, ΦBn are sequentially applied to start the readout period Trd, and a voltage change VD corresponding to the electric charge accumulated in the double-gate photosensor 10 is output from the output circuit 113 via the data line 103. Read. Here, read pulses φB1, φB
2,... ΦBn are pulse signals of the signal voltage Vbgh at a high level and the signal voltage Vbgl at a low level, and read pulses φB1, φB2,. At the timing, the low-level signal voltage Vbgh is applied.

<Effective Voltage Adjustment Operation> Next, when the above-described image reading operation is completed in all rows (n),
In the reading sensitivity setting operation and the image reading operation, an effective voltage adjusting operation for adjusting the bias of the effective voltage of the signal applied to each gate electrode and optimizing the bias is executed (step S11).
3). That is, as shown in FIG. 9, in each operation described above, the average value of the signal voltage applied to the top gate line 101 (top gate terminal TG) of the double gate photosensor 10 by the reset pulse, that is, the effective voltage is A signal (first signal voltage) having a predetermined effective voltage that can be adjusted to an optimum value Vte set in advance according to the sensitivity characteristics of the double-gate photosensor 10
Is applied to the top gate line 101 of each row. Similarly, the bottom gate line 102 (bottom gate terminal B) of the double gate
G) A signal having a predetermined effective voltage that can adjust the average value of the signal voltages applied to G), that is, the effective voltage to an optimum value Vbe previously set according to the sensitivity characteristics of the double-gate photosensor 10. (Second signal voltage)
It is applied to the bottom gate line 102 of each row.

Here, the double gate type photo sensor 10
The effective voltage of the signal applied to the top gate TG and the bottom gate BG will be briefly described. As is clear from FIG. 9, in each reset operation in the reading sensitivity setting operation and the image reading operation, the top gate TG
On the other hand, the high-level signal voltage Vtgh is applied only for an extremely short time (Trst), and the low-level signal voltage Vtgl is applied for other relatively long periods. Therefore, during the reading sensitivity setting operation and the image reading operation, the effective voltage applied to the top gate TG is largely biased toward the low level. Further, the optimal light accumulation period Tb set for the image reading operation is changed and set each time in accordance with the environmental illuminance and the like by the reading sensitivity setting operation, so that the effective voltage applied to the top gate TG becomes Inevitably fluctuates.

On the other hand, also in the reading operation in the reading sensitivity setting operation and the image reading operation, the bottom gate B
For G, the high-level signal voltage Vbgh is applied only for an extremely short time (Trd), and the low-level signal voltage Vtgl is applied for other relatively long periods. Therefore, during the reading sensitivity setting operation and the image reading operation, the effective voltage applied to the bottom gate BG is also largely biased toward the low level. Further, the optimal light accumulation period Ta set in the image reading operation is changed and set each time in accordance with the environmental illuminance or the like by the reading sensitivity setting operation. Therefore, the effective voltage applied to the bottom gate TG is: Inevitably fluctuates. For this reason, if such a voltage biased to the voltage side of a specific polarity continues to be applied to the gate electrode, holes are trapped in the gate electrode, and the element characteristics of the double-gate photosensor are deteriorated and the sensitivity is lowered. There is a problem that the characteristics change.

Therefore, in the present embodiment, the voltage waveform applied in the processing cycle of the reading sensitivity setting operation and the image reading operation and in the processing cycle of the effective voltage adjustment operation to be executed from now on is, for example, a double gate type. With reference to the optimum value Vte of the effective voltage on the top gate and the optimum value Vbe of the effective voltage on the bottom gate, which are set according to the sensitivity characteristics of the photosensor, In order to make the absolute value equal to the absolute value of the time integration value on the low level side, an adjustment pulse having predetermined signal widths Ttp and Tbp is supplied to the top gate line of the double-gate photosensor during the effective voltage adjustment operation, and , By applying to the bottom gate line,
By suppressing the change in sensitivity characteristics due to the deterioration of the device characteristics,
The reliability of the photo sensor system can be improved.

<Specific Example> Next, a specific example in which the configuration and operation of the photosensor system described above are applied to a fingerprint reader will be described with reference to the drawings. FIG.
FIG. 11 is a diagram illustrating an example of image data when the image reading sensitivity is changed step by step for each row of the subject image in the pre-reading operation, and FIG. 11 illustrates a specific row in a specific row obtained by the pre-reading operation. FIG. 12 is a graph showing a change in brightness data for each pixel, and FIG. 12 shows a relationship between a change in a dynamic range (difference between maximum and minimum brightness data) for each row and a change in a primary differential value of the dynamic range. FIG. 13 is a graph showing the relationship between the first derivative of the dynamic range obtained by the pre-read operation and the row number-image reading sensitivity correspondence table.

In FIG. 10, the fingerprint image data is
For example, it is read out in a matrix of 256 rows × 196 columns,
The image data when the image reading sensitivity is set to be higher (the light accumulation period is longer) as the line number is larger is shown. Therefore, as the row number increases, the image reading sensitivity increases, and the uneven pattern PNA of the fingerprint is read (faded) by the influence of external light or the like, so as to be blurred (fading) or to be invisible (FIG. 10). Above). On the other hand, as the row number becomes smaller, the image reading sensitivity becomes lower (light accumulation period becomes shorter), and the fingerprint is read as a dark image such that the concave / convex pattern PNA becomes dark or invisible (lower part in FIG. 10). In such image data, it is preferable from the viewpoint of image processing that the sensitivity determination target range used for extracting a row having the optimum sensitivity is limited to a region having a good contrast corresponding to the concave and convex pattern PNA of the fingerprint. Here, as an example, lines 64 to 191 and 67 to 13
The sensitivity setting process when the row / column range in the 0th column is set as the sensitivity determination target range will be described.

In the sensitivity determination target range shown in FIG. 10, for example, when the change of the brightness data on lines 64, 96, 160, and 191 is extracted and graphed, as shown in FIG. , Line 191 (shown by a broken line in the figure) and line 160 (shown by a thin line in the figure)
Since the sensitivity is set to be high, the brightness data converges to a high value (approximately 220 to 225), and there is no information (brightness / darkness pattern) as image data. In the 96th row (indicated by a bold line in the figure), the brightness data does not converge at the upper limit or the lower limit in all the columns and has a relatively large vertical displacement corresponding to the brightness pattern of the image data. ing. In addition, 64
In the line (indicated by a dashed line in the figure), the sensitivity is set low, so that the brightness data has a substantially low value (about 3).
(About 5), and there is no information as image data. Here, the larger the brightness data value, the brighter the image data, and the smaller the brightness data value, the darker the image data.

Next, according to the above-described abnormal value removing operation, the distribution of the brightness data of each row is Fourier-transformed to obtain a frequency distribution corresponding to the row number, and an abnormal value or a high frequency component corresponding to noise is removed. Only the brightness data indicating the main change tendency in the distribution of the brightness data for each is extracted. Then, the maximum value and the minimum value are extracted from the distribution of the brightness data for each row from which the abnormal value has been removed, and the difference between them is calculated to obtain the dynamic range (data range). As shown, a distribution having a local maximum MA in a given row is obtained. further,
When the first derivative of the distribution of the dynamic range is calculated and the tendency of the change is obtained, as shown in FIG. 12B, the first derivative is 0 (or minimum; FIG. 12B) in the row indicating the maximum value MA. Medium, indicated by MB). At this time, the brightness data of the row in which the dynamic range shows the maximum and the first derivative thereof is the minimum is image data having a good contrast corresponding to the concave and convex pattern of the fingerprint. Can be determined to be set.

Then, as shown in FIG. 13A, the dynamic range shows a maximum (for example, R _{k in} the figure) and the first-order derivative thereof is minimum (for example, D _{k-1 in the} figure).
(B) in the row (L _k−1 , L _k ) in FIG.
By referring to the row number-image reading sensitivity correspondence table shown in FIG. 2, the image reading sensitivity set in the rows L _k−1 and L _k , that is, the light accumulation period T _k− of the double gate type photosensor. ₁ , _Tk is extracted and determined as the optimal value. Here, the above-described sensitivity setting register 128 includes:
As the optimum image reading sensitivity, a set value determined based on the two extracted light accumulation periods T _k−1 and T _k , for example, an average value of the light accumulation periods T _k−1 and T _k is set. Rewriting is controlled as follows. In the dynamic range and the distribution of the first derivative shown in FIGS. 12A and 12B,
Although the case where the primary differential value of the row in which the dynamic range has the maximum value MA is 0 (MB) has been described, there is actually no row in which the primary differential value becomes 0, so the optimal sensitivity is set. It is desirable to extract a row in which a dynamic range shows a maximum and a first-order derivative thereof becomes minimum (that is, a row showing a value closest to 0).

Here, in the above-described image reading sensitivity setting process, an operation process in the case where there is an abnormal pixel due to a foreign substance included in a subject image or a defect of a sensor element constituting a photo sensor array, etc., will be described with reference to the drawings. It will be described with reference to FIG. FIG. 14 is a diagram illustrating another example of image data when the image reading sensitivity is changed stepwise for each row of the subject image and read in the pre-reading operation.
5 is a graph showing the contrast distribution of the brightness data of each row when a foreign substance or the like is present in the subject image, and the contrast distribution of the brightness data of each row after the abnormal value removal operation. As shown in FIG. 14, similarly to the case described above, 64 to 19
In the case where the row / column range of the first row and the 67th to 130th columns is set as the sensitivity determination target range, foreign matter adhering to the fingerprint reading surface (detection surface), element defect of the double gate type photosensor, image If an abnormal pixel IL spans a plurality of pixels within the sensitivity determination range due to noise or the like included in the data, the brightness data of the abnormal pixel IL continuously protrudes over a plurality of rows with respect to the surrounding pixel data. May indicate a value. For example, when a black point exists on a white background, or when a white point exists on a black background,
In particular, as shown in FIG. 15 (a), the variation width and contrast of the brightness data vary discretely for each row,
This is a case where abnormal pixel data MC due to a foreign substance or element defect attached to the detection surface exists over a plurality of rows.

In such a case, without performing the above-described abnormal value removing operation (steps S103 to S105 in FIG. 8), the dynamic range distribution calculated based on the maximum value and the minimum value of the lightness data can be used. When the process of obtaining the optimum value of the reading sensitivity (steps S106 to S110 in FIG. 8) is executed, the dynamic range of the row in which the abnormal pixel IL continuously exists over a plurality of rows is changed from the entire main distribution tendency (change tendency). Since it largely deviates and appears as a continuous change with respect to the main distribution tendency, the abnormality is recognized as a part of the change tendency of the dynamic range distribution, and has no relation to the original maximum value MA. The dynamic range of the row where the pixel IL exists is extracted as the maximum value, and the image reading feeling set for the row having the dynamic range is determined. It is mistaken as the optimum value. In this case, an inappropriate image reading sensitivity (for example, a light accumulation time longer than the optimum value) is set in the photo sensor system, and the subject image may be overexposed in a normal reading operation. There is.

On the other hand, in the method for setting the sensitivity of the photosensor system according to the present invention, Fourier transform is performed prior to the processing for obtaining the optimum value of the reading sensitivity based on the dynamic range of the brightness data, and abnormal values and noise are eliminated. By removing the corresponding high-frequency component, an abnormal value included in the brightness data can be removed in advance.
As shown in (b), an abnormal value which largely deviates from the distribution tendency of the contrast of the brightness data with respect to the line number is eliminated, and the smoothed brightness data M indicating the main distribution tendency is removed.
Only D is extracted. Therefore, due to noise components that discretely vary depending on the measurement data, relatively large foreign substances attached to the fingerprint reading surface, element defects of the double-gate photosensor, etc., abnormal pixels (or Even if IL is included, it is possible to reliably extract a row having a good contrast corresponding to the concave and convex pattern of the fingerprint and determine the optimal light accumulation time. It is possible to provide a fingerprint reader that can read a complex fingerprint image, has less malfunction, and has high reliability.

As described above, according to the photo sensor system and the sensitivity setting method according to the present embodiment, the pre-read operation is performed on the subject image by changing the image reading sensitivity step by step for each row, and the brightness data is mainly stored. After performing an abnormal value removal operation that removes abnormal values that deviate from the change tendency, the line in the optimal image reading state is easily and accurately determined based on the first derivative of the dynamic range for the brightness data of each line. As a result, the image reading sensitivity (light accumulation period) set for the row can be set as the optimum sensitivity, so that an extraordinary pixel due to a foreign substance adhering to the fingerprint reading surface or an element defect of the double gate type photo sensor can be set. The normal image reading operation of the subject image can be read with appropriate sensitivity without being affected. In addition, prior to the normal image reading operation, the sensitivity setting process can be performed using the actual subject. Therefore, even when the brightness of the subject changes due to a change in the environmental illuminance, each time, Optimum image reading sensitivity can be set, and there is no need to install a dedicated circuit or the like for detecting environmental illuminance.

Further, even when the characteristics of the double-gate photosensor change, the processing for obtaining the optimum sensitivity based on the image data obtained by the double-gate photosensor is performed. The effect of the fluctuation can be greatly suppressed. In addition, since the optimum sensitivity can be set using the subject itself, the sensitivity setting process can be performed extremely easily without preparing a standard sample in the sensitivity setting process. In the present embodiment, the sensitivity determination target range is
The case where the sensitivity setting process is executed only for the row / column ranges of the 64th to 191st rows and the 67th to 130th rows has been described. However, the present invention is not limited to this, and the sensitivity determination target range is limited at all. Needless to say, even when the sensitivity setting processing is executed for the entire area of the image data, the sensitivity setting processing can be applied.

Next, image reading sensitivity (light accumulation period) applicable to the pre-reading operation of each of the above-described embodiments.
Another setting method will be described with reference to the drawings. FIG. 16 is a timing chart showing another example of a method for setting the image reading sensitivity (light accumulation period) that can be favorably applied to the photosensor system according to the present invention. Here, a description will be given with reference to the configuration of the photosensor system shown in FIGS. 2, 6, and 7 as appropriate. As shown in FIG. 16, the sensitivity setting method of the photo sensor system according to the present embodiment firstly sets the top gate terminal TG of the double gate type photo sensor 10 to each of the top gate lines 101 connecting in the row direction. At the same time, reset pulse φT1,
.. φTn are applied to simultaneously start the reset period Trst, and the double gate type photo sensor 1
Initialize 0.

Next, reset pulses φT1, φT2,
... ΦTn simultaneously fall and the reset period Trst ends, so that the light accumulation periods TB ₁ , TB ₂ ,.
And started all at once B _n-1, TB n, charges (holes) generated in the channel region in accordance with the amount of light entering from the top gate electrode side of the double-gate photo-sensor 10 for each row is accumulated You. Here, the light accumulation periods TB ₁ , TB ₂ ,..., TB _n−1 , TB _n set for each row are changed stepwise by a predetermined delay time Tdly for each row, as shown in FIG. Thus, the precharge signal φpg and the read pulses φB1, φB2,... ΦBn are applied. Therefore, in the pre-reading operation performed prior to the sensitivity setting processing as described in the above-described embodiment, an image read at a different reading sensitivity for each row constituting the subject image (that is, different reading sensitivity for the number of rows). Data can be acquired by reading a subject image (one screen) once.

Note that the method of setting the image reading sensitivity (light accumulation period) applied to the sensitivity setting process according to the present invention is not limited to the above-described respective examples. For example, a series of processing cycles of performing a reset operation, a light accumulation operation, a precharge operation, and a read operation for an entire normal screen is repeated a plurality of times while sequentially changing the read sensitivity. Needless to say, a plurality of image data with different reading sensitivities may be obtained, or another method may be used. In each of the embodiments described above, a case is described in which a double-gate photosensor is applied as a photosensor constituting a photosensor array, but the present invention is not limited to this. In short, as long as the photosensors constituting the photosensor array have a configuration in which the reading sensitivity setting operation is performed prior to the image reading operation, the configuration and sensitivity setting method of the photosensor system according to the present invention are satisfactory. Can be applied to

[0056]

According to the invention as set forth in claim 1, 2, 9 or 10, a photo sensor array comprising photo sensors two-dimensionally arranged is provided, and the image reading sensitivity is set for setting the image reading sensitivity. In a photo sensor system that performs a pre-reading operation of reading a subject image while changing it, among predetermined measurement amounts related to the image pattern of the subject image at each image reading sensitivity, an abnormality deviating from a main change tendency of the measured value. After the value is removed, the image reading sensitivity in the optimum image reading state is extracted and set based on the data range of the measured value and the displacement of the data range between the image reading sensitivities, and a normal reading operation is performed. It is possible to set an appropriate image reading sensitivity without being affected by continuous abnormal pixels and discretely varying noise components contained in the subject image. Rukoto can.

Since the sensitivity setting process is performed using the actual subject prior to the normal image reading operation, even if the brightness of the subject changes due to a change in ambient light, each time, The optimum image reading sensitivity can be set, and there is no need to install a dedicated circuit or the like for detecting environmental light. Further, even when the characteristics of the photosensor change, the processing for obtaining the optimum sensitivity based on the image data obtained by the photosensor is performed. Can be. In addition, since the optimum sensitivity can be set using the subject itself, the sensitivity setting process can be performed extremely easily without preparing a standard sample in the sensitivity setting process.

According to the third or eleventh aspect of the present invention, the abnormal value removing operation includes performing a Fourier transform on a predetermined measured amount and removing a predetermined high-frequency component from the frequency-converted measured amount. Since the measurement is performed, by passing the frequency-converted measurement amount through a simple configuration such as a low-pass filter, abnormal values included in the measurement amount can be removed satisfactorily, and only the measurement value indicating a main change tendency is obtained. To extract the optimum image reading sensitivity. According to the fourth aspect of the present invention, the pre-reading operation is performed by setting a different image reading sensitivity to the photosensor array step by step for each row of the subject image. Image data read with different reading sensitivities can be acquired by reading the subject image (one screen) once, shortening the time required for the sensitivity setting process and quickly setting an appropriate image reading sensitivity. can do.

According to the fifth aspect of the present invention, the brightness data corresponding to the image pattern of the subject image is measured and the sensitivity setting process is performed as the predetermined measurement amount, so that the contrast of the brightness data is Fourier transformed. By converting the frequency component into a high-frequency component and removing the high-frequency component, abnormal values included in the brightness data can be satisfactorily eliminated, and by calculating the dynamic range of the brightness data and its first derivative, It is possible to appropriately extract a row in which a light and dark pattern of a subject image is obtained well, and it is possible to easily and appropriately set an optimum image reading sensitivity. According to the sixth aspect of the invention, the image reading sensitivity of the photo sensor array is set and controlled by adjusting the light accumulation period in the photo sensor. A time element (pulse timing) of a light accumulation period in which a dynamic range of a measurement amount for each image reading sensitivity from which an abnormal value has been removed and an image reading sensitivity extracted based on a first derivative thereof are set in a photo sensor. It is possible to provide a photo sensor system that can easily perform setting control only by using only it, suppress the influence of environmental light such as external light, and can read a proper subject image satisfactorily.

According to the seventh aspect of the present invention, after the normal reading operation of the subject image is completed, the first signal voltage for setting the effective voltage applied to the first electrode in the photo sensor array to an optimum value. And the second signal voltage for making the effective voltage applied to the second electrode in the photosensor array an optimum value, so that the reading sensitivity setting operation and the image reading operation can be performed in the reading sensitivity setting operation and the image reading operation. The bias of the effective voltage due to the signal voltage applied to the sensor can be optimized, the deterioration of the element characteristics of the photosensor and the change of the sensitivity characteristics can be suppressed, and a highly reliable photosensor system can be provided. .

According to the invention described in claim 8, the photosensor has a source electrode and a drain electrode formed with a channel region made of a semiconductor layer interposed therebetween, and at least above and below the channel region via an insulating film. Having a top gate electrode and a bottom gate electrode formed by using one of the top gate electrode and the bottom gate electrode as a light irradiation side, and the charge corresponding to the amount of light irradiated from the light irradiation side is the above. Since it is constituted by a so-called double gate type photo sensor generated and accumulated in a channel region, a photo sensor device constituting a photo sensor array is thinned, and a two-dimensional image reading apparatus to which a photo sensor system is applied is provided. It is possible to reduce the size and read the subject image with high definition by increasing the density of the read pixels. .

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a structure of a double-gate photosensor applied to an image reading apparatus according to the present invention.

FIG. 2 is a schematic configuration diagram of a photosensor system configured by two-dimensionally arranging double-gate photosensors.

FIG. 3 is a timing chart showing a general drive control method of the photo sensor system.

FIG. 4 is an operation conceptual diagram of a double gate type photo sensor.

FIG. 5 is a diagram showing a light response characteristic of an output voltage of the photo sensor system.

FIG. 6 is a schematic configuration diagram illustrating an example of a two-dimensional image reading apparatus to which the photo sensor system according to the present invention is applied.

FIG. 7 is a block diagram illustrating a configuration example of a controller applied to the photo sensor system according to the present invention.

FIG. 8 is a flowchart showing one processing procedure of a sensitivity setting method of the photo sensor system according to the present invention.

FIG. 9 is a timing chart showing an example of a sensitivity setting method of the photo sensor system according to the present invention.

FIG. 10 is a diagram showing an example of image data when the image reading sensitivity is changed stepwise for each row of the subject image and read in the pre-reading operation of the photosensor system according to the present invention.

FIG. 11 is a graph showing a change in brightness data for each pixel in a specific row obtained by a pre-read operation of the photo sensor system according to the present invention.

FIG. 12 shows a relationship between a change in a dynamic range (difference between maximum and minimum brightness data) for each row and a change in a primary differential value of the dynamic range obtained by a pre-read operation of the photosensor system according to the present invention. It is a graph shown.

FIG. 13 is a diagram showing a relationship between a primary differential value of a dynamic range obtained by a pre-read operation of the photo sensor system according to the present invention and a row number-image reading sensitivity correspondence table.

FIG. 14 is a diagram showing another example of the image data when the image reading sensitivity is changed step by step in each row of the subject image in the pre-reading operation of the photo sensor system according to the present invention.

FIG. 15 illustrates a distribution of contrast of brightness data of each row when a foreign object or the like is present in a subject image obtained by a pre-read operation of the photo sensor system according to the present invention, and a distribution of brightness data of each row after an abnormal value removing operation. It is a graph which shows distribution of contrast of brightness data.

FIG. 16 is a timing chart showing another example of a method of setting an image reading sensitivity (light accumulation period) that can be favorably applied to the photo sensor system according to the present invention.

[Explanation of symbols]

 Reference Signs List 10 double gate type photo sensor 100 photo sensor array 111 top gate driver 112 bottom gate driver 113 output circuit 114 column switch 115 precharge switch 116 amplifier 117 A / D converter 120 controller 121 device controller 122 data controller 123 main controller 124 abnormal value removal Unit 124a Fourier transform unit 124b Filter unit 124c Inverse Fourier transform unit 125 Data comparator 126 Adder 127 Data selector 128 Sensitivity setting register 130 RAM 200 External function unit

Claims (11)

[Claims] 1. A photosensor system comprising a photosensor array configured by two-dimensionally arranging photosensors and performing a pre-read operation for reading a subject image while changing the image reading sensitivity for setting the image reading sensitivity. An abnormal value removing unit that removes an abnormal value that deviates from a main change tendency of the measured value among predetermined measured amounts related to the image pattern of the subject image at each of the image reading sensitivities; Reading sensitivity extracting means for extracting the image reading sensitivity suitable for the reading operation of the subject image based on the measured value thus obtained; and setting the extracted image reading sensitivity at the time of the normal reading operation of the subject image. And a reading sensitivity setting unit. 2. The image reading apparatus according to claim 1, wherein the reading sensitivity extracting unit is configured to read out the image in which the data range of the measurement value from which the abnormal value has been removed is maximized, and the displacement of the data range between the image reading sensitivities is minimized. The photosensor system according to claim 1, wherein sensitivity is extracted. 3. The abnormal value removing unit removes the abnormal value by performing a Fourier transform on the predetermined measured amount and removing a predetermined high-frequency component from the frequency-converted measured amount. The photosensor system according to claim 1, wherein: 4. The pre-reading operation of the subject image includes the steps of:
2. The photo sensor system according to claim 1, wherein the photo sensor system is set and executed in the photo sensor array. 5. The photosensor system according to claim 1, wherein the predetermined measurement amount is brightness data corresponding to an image pattern of the subject image. 6. The photosensor system according to claim 1, wherein the image reading sensitivity of the photosensor array is set and controlled by adjusting a light accumulation period in the photosensor. 7. The photo sensor system applies a first signal voltage for optimizing an effective voltage applied to a first electrode in the photo sensor array and a second signal voltage in the photo sensor array. 6. The photosensor system according to claim 1, further comprising an effective voltage adjusting unit that applies a second signal voltage for setting an effective voltage applied to the electrodes to an optimum value. 8. The photosensor includes a source electrode and a drain electrode formed with a channel region made of a semiconductor layer interposed therebetween, and a top gate electrode formed at least above and below the channel region with an insulating film interposed therebetween. And a bottom gate electrode, wherein one of the top gate electrode and the bottom gate electrode is used as a light irradiation side, and a charge corresponding to the amount of light irradiated from the light irradiation side is generated in the channel region. The photosensor system according to any one of claims 1 to 6, wherein the photosensor system has a configuration for storing. 9. A photosensor system comprising: a photosensor array configured by two-dimensionally arranging photosensors; and performing a pre-read operation for reading a subject image while changing the image reading sensitivity for setting the image reading sensitivity. In the sensitivity setting method, a step of removing an abnormal value deviating from a main change tendency of the measured value among predetermined measurement amounts related to the image pattern of the subject image at each of the image reading sensitivities; A step of extracting the image reading sensitivity suitable for the reading operation of the subject image based on the removed measurement value; and a step of setting the extracted image reading sensitivity at the time of the normal reading operation of the subject image. And a sensitivity setting method for a photosensor system. 10. The procedure for extracting the image reading sensitivity is as follows:
The measurement is performed by extracting the image reading sensitivity at which the data range of the measurement value from which the abnormal value has been removed is maximized and the displacement between the image reading sensitivities of the data range is minimized. The sensitivity setting method for a photosensor system according to claim 9. 11. The step of removing an abnormal value from the predetermined measurement amount is performed by performing a Fourier transform on the predetermined measurement amount and removing a predetermined high-frequency component from the frequency-converted measurement amount. The method for setting sensitivity of a photosensor system according to claim 9, wherein: