JP2003242493A - Image reader and sensitivity setting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reader and its sensitivity adjusting method, capable of eliminating influence of abnormal pixel data detected by an abnormal pixel and setting suitable image reading sensitivity to obtain a good object image in the regular image reading operation. <P>SOLUTION: A controller 150 has a function of setting an image read sensitivity for performing the operation (sensitivity adjusting read operation) of reading an image for adjusting the sensitivity in an arbitrary timing prior to the regular image reading operation to read the object image at optimum, and a function of eliminating specified pixel data (specified data eliminating operation) to prevent or restrain the influence of abnormal pixel data due to foreign matter (dust) adhering to the detecting surface or an element defect existing in a photo sensor array from the pixel data read in the sensitivity adjusting read operation. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus and a sensitivity setting method thereof, and more particularly, to a sensor array in which a plurality of sensors are arranged in a matrix or a line,
The present invention relates to an image reading device for reading an image pattern of a subject by scanning and driving the sensor array, and a sensitivity setting method thereof.

[0002]

2. Description of the Related Art Conventionally, as a technique for reading a two-dimensional image pattern such as a printed matter, a photograph, or a fine concavo-convex shape such as a fingerprint, a sensor such as a photoelectric conversion element (photosensor) is arranged in a matrix or a line. 2. Description of the Related Art There is known an image reading device that scans and drives a sensor array that is arranged in a manner described above to read an image pattern of a subject placed and contacted on a predetermined detection surface.

Such an image reading apparatus has a fingerprint authentication system (fingerprint collation apparatus) or the like in response to the recent increasing social demand for management and protection of personal information, company information, etc., or security such as crime prevention. Has been actively researched and developed for application of the personal authentication to the technical field.

Here, as a sensor array applied to an image reading apparatus, a CCD (Charge Coupled Dev) is generally used.
Solid-state imaging devices such as ice) are used. CCD
As is well known, has a configuration in which a plurality of photosensors such as photodiodes and thin film transistors (TFTs) are arrayed, and an electron-positive voltage generated corresponding to the amount of light emitted to the light receiving portion of each photosensor. The horizontal scanning circuit and the vertical scanning circuit detect the charge amount of the pair of holes to detect the brightness of the irradiation light.

However, a photo sensor system to which such a CCD is applied (a main part of the image reading apparatus including a sensor array, a horizontal scanning circuit, a vertical scanning circuit, etc .;
(Details will be described later), the basic technology has been established, and although it has the advantage that it can be easily applied to actual products such as image reading devices, each scanned element has the structure of the photo sensor array. Since it is necessary to individually provide a selection transistor for bringing the photosensor into a selected state, if the number of pixels forming the sensor array is increased in order to improve the reading accuracy (high definition) of the subject image, the system is accordingly changed. There was a problem that the size itself increased.

Therefore, in recent years, as a structure for solving such a problem, a thin film transistor having a so-called double gate structure (hereinafter, referred to as "a thin film transistor") in which a photo sensor itself has a photo sensing function and a selection transistor function is provided. An attempt has been made to reduce the size of the system and increase the density of pixels by applying a “double gate type photo sensor” to a photo sensor system.

In such a photo sensor system, roughly, a double gate type photo sensor having a top gate electrode and a bottom gate electrode is formed in a matrix on one surface side of a glass substrate or the like to form a photo sensor array,
For example, a two-dimensional image of a subject placed on one side of the glass substrate (above the photosensor array) (subject image; Reflected light according to the fingerprint pattern, etc.)
The double-gate type photo sensor detects light and dark information to read the subject image.

Here, the image reading operation by the photosensor array is performed in each charge accumulation period from the end of initialization by the application of the reset pulse to the double gate type photosensor for each row to the application of the read pulse. Output voltage (drain voltage) corresponding to the amount of carriers (holes) accumulated in each gate type photosensor
By reading out, the subject image is read by a series of operation steps for detecting light and dark information (reset operation → charge accumulation operation → precharge operation → readout operation).

Note that such a series of operation steps are
The same operation steps are executed not only in the case of applying the double gate type photosensor described above but also in a photosensor system using a well-known photodiode, phototransistor or the like as a photosensor. In addition, specific configurations and operations of the above-described double-gate photosensor and the photosensor array will be described in detail in the embodiments of the invention described later.

By the way, in a photosensor system to which various photosensors such as the above-mentioned double gate type photosensor are applied, there are various external factors such as indoor and outdoor use environment and brightness of the subject itself. Regardless, in order to satisfactorily read the subject image, it is necessary to appropriately adjust and set the reading sensitivity of the photosensor (in the double gate type photosensor, the charge accumulation period) according to the environment or the like.

The appropriate reading sensitivity in the photo sensor is
Conventionally, a standard sample placed on the detection surface before starting a normal scan operation or providing a circuit for detecting the ambient illuminance separately depends on the ambient conditions such as the ambient illuminance. Is performed by changing the reading sensitivity in multiple steps (hereinafter referred to as “sensitivity adjustment reading operation”), and based on the detection results and reading results, the optimum reading according to the ambient conditions such as environmental illuminance. The method of obtaining the reading sensitivity was adopted.

Here, as a method for setting the optimum reading sensitivity by the reading operation for sensitivity adjustment, for example, Japanese Patent No. 311
No. 6950 discloses a photosensor array in which photosensors (double-gate photosensors) are arranged in a matrix, and reading sensitivity is set to be different (changed) step by step for each row, and a predetermined subject image is set. Based on the data range (difference between the maximum pixel value and the minimum pixel value; dynamic range) calculated from the brightness data detected for each row (that is, for each reading sensitivity), the optimum image reading state is obtained. A method is described in which a row (row having the maximum dynamic range) is determined, and the reading sensitivity (charge accumulation period) set in the row is set as the optimum sensitivity and the sensitivity when reading a regular subject image. .

[0013]

However, the above-mentioned conventional techniques have the following problems. In other words, abnormal pixel data such as bright spots or dark spots in the sensitivity adjustment reading operation due to element defects or element characteristic variations of the photosensors forming the photosensor array, or adhesion of foreign matter to the detection surface may occur. If there is a pixel to be detected, if the pixel data (brightness data) for each row obtained by the read operation for sensitivity adjustment is used as it is, the dynamic range originally calculated based on the appropriate pixel data will be the maximum. Since the dynamic range is maximized in a row different from the row, an inappropriate image reading sensitivity may be set, which may cause a significant deterioration in the image quality of the subject image acquired by the regular image reading operation. Had a problem. Therefore, for example, when an image reading device equipped with such a photo sensor array is applied to a fingerprint collation device, it is not possible to obtain a subject image with good image quality, which may cause malfunction in the fingerprint collation processing. Had.

Further, in order to prevent such problems from occurring, manufacturers of image reading devices and photosensor devices manufacture photosensor arrays that have no element defects or have very few element defects. As described above, the quality control in the manufacturing process must be strictly performed, and therefore, it has been desired to realize a promising and appropriate technique or method capable of improving the manufacturing yield.

In view of the above-mentioned problems, the present invention has a photosensor array including a plurality of photosensors, and executes a sensitivity adjustment reading operation separately from a regular image reading operation. At
An image reading apparatus capable of removing an influence of abnormal pixel data detected by an abnormal pixel or the like, setting an appropriate image reading sensitivity, and obtaining a good subject image in a normal image reading operation, and its sensitivity adjustment The purpose is to provide a method.

[0016]

An image reading apparatus according to claim 1, comprising a photosensor array including a plurality of photosensors, and an image of a subject placed on a detection surface on the photosensor array. In the reading device, in the sensitivity adjustment reading operation for setting the image reading sensitivity applied to the regular image reading operation for the subject, the image reading sensitivity is changed for each pixel data group to obtain a predetermined image for sensitivity adjustment. And a specific data removing unit for removing specific pixel data from the pixel data group for each image reading sensitivity related to the image pattern of the predetermined image read by the sensitivity adjusting reading unit. , An image reading sensitivity suitable for a normal reading operation of the subject image based on the pixel data group excluding the specific pixel data. It is characterized by comprising a reading sensitivity setting means for performing the reading sensitivity setting operation to a constant, a.

An image reading apparatus according to a second aspect is the image reading apparatus according to the first aspect.
In the image reading device described above, the reading sensitivity setting means compares at least the magnitude relation between the pixel data belonging to the pixel data group from which the specific pixel data has been removed by the specific data removing means, Data comparison means for extracting pixel data having a maximum value and a minimum value from the pixel data group, and the image reading sensitivity based on at least the maximum value and the minimum value of the pixel data extracted by the data comparison means. Data calculation means for calculating the data range of the pixel data group for each image, and the image having the maximum data range of the data range of the pixel data group for each image reading sensitivity calculated by the data calculation means A reading sensitivity extracting means for extracting the reading sensitivity, and the extracted image reading sensitivity is a regular image for the subject. Is characterized by having a reading sensitivity determining means for determining an image reading sensitivity in the preparative operation, the.

An image reading apparatus according to a third aspect of the present invention is the image reading apparatus according to the first aspect.
In the image reading device described above, the specific data removing unit removes at least the maximum or minimum pixel data from the pixel data group obtained for each image reading sensitivity by the sensitivity adjustment reading operation. It is characterized by that. The image reading device according to claim 4 is the image reading device according to claim 3, wherein the specific data removing unit includes a pixel data group obtained for each of the image reading sensitivities by the sensitivity adjusting reading operation. It is characterized in that a plurality of the pixel data are removed in descending order from the maximum value.

An image reading apparatus according to a fifth aspect is the image reading apparatus according to the third aspect.
In the image reading device described above, the specific data removing unit, among the pixel data group obtained for each image reading sensitivity by the reading operation for sensitivity adjustment, a plurality of the pixel data in ascending order from the minimum value. It is characterized by removing. The image reading device according to claim 6 is the image reading device according to any one of claims 1 to 5, wherein the sensitivity adjustment reading means is configured to perform a predetermined row of the photosensor array in the sensitivity adjustment reading operation. It is characterized in that different image reading sensitivities are set stepwise for each number and the predetermined image for sensitivity adjustment is read only once.

An image reading apparatus according to a seventh aspect is the image reading apparatus according to the first aspect.
7. In the image reading device according to any one of 6 to 6, the sensitivity adjusting reading unit, in the sensitivity adjusting reading operation, displays a predetermined image for the sensitivity adjusting for the entire effective reading area of the photosensor array. It is characterized by reading. The image reading apparatus according to claim 8 is the image reading apparatus according to any one of claims 1 to 7, wherein the sensitivity adjusting reading unit is an effective reading area of the photosensor array in the sensitivity adjusting reading operation. It is characterized in that the predetermined image for sensitivity adjustment is read only in the detection area set in advance.

An image reading apparatus according to a ninth aspect is the image reading apparatus according to the eighth aspect, wherein in the detection area, at least the reading sensitivity setting means is provided in the pixel data group excluding the specific pixel data. The read sensitivity setting operation is set in an area where a minimum number of pixel data can be normally executed. An image reading apparatus according to claim 10 is the image reading apparatus according to any one of claims 1 to 9, wherein the pixel data is lightness data corresponding to an image pattern of the predetermined image. .

An image reading apparatus according to an eleventh aspect is the image reading apparatus according to any one of the first to tenth aspects,
The photo sensor includes a source electrode and a drain electrode formed with a channel region made of a semiconductor layer interposed therebetween, and a first gate electrode and a second electrode formed at least above and below the channel region with an insulating film interposed therebetween. Of the first gate electrode or the second gate electrode as the light irradiation side, and the amount of light irradiated from the light irradiation side during a predetermined charge accumulation period. It is characterized in that a corresponding charge is generated and accumulated in the channel region, and the pixel data is generated based on the amount of the accumulated charge. The image reading device according to claim 12 is the image reading device according to any one of claims 1 to 11, wherein the reading sensitivity setting means controls a charge accumulation period in the photosensor in the reading sensitivity setting operation. Thus, the image reading sensitivity is arbitrarily adjusted.

According to a thirteenth aspect of the present invention, there is provided a method for setting a sensitivity of an image reading apparatus, comprising a photosensor array including a plurality of photosensors, and reading an image of a subject placed on a detection surface on the photosensor array. In the sensitivity setting method, the procedure for reading a predetermined image for sensitivity adjustment by changing the image reading sensitivity in a plurality of steps for each photo sensor forming the photo sensor array, and reading for each image reading sensitivity Based on the procedure of removing specific pixel data from the pixel data group related to the image pattern of the predetermined image, and the pixel data group from which the specific pixel data has been removed, a normal image of the subject image is obtained. Procedure to set the image reading sensitivity suitable for reading operation,
It is characterized by including.

According to a fourteenth aspect of the present invention, there is provided a sensitivity setting method for an image reading apparatus according to the thirteenth aspect, wherein the procedure for removing the specific pixel data is obtained for each image reading sensitivity. The pixel data having at least the maximum value or the minimum value is removed from the pixel data group. The sensitivity setting method of the image reading device according to claim 15 is the method of setting the sensitivity of the image reading device according to claim 13 or 14, wherein the procedure for removing the specific pixel data is obtained for each of the image reading sensitivities. All pixel data included in the pixel data group are compared with each other in size relation, the pixel data is rearranged in order, and a predetermined number of pixels are arranged from an arbitrary end in the rearranged pixel data array. And a process of removing the pixel data.

According to a sixteenth aspect of the present invention, there is provided a method for setting the sensitivity of the image reading apparatus according to the thirteenth or fourteenth aspect, wherein the procedure for removing the specific pixel data is obtained for each of the image reading sensitivities. It is characterized in that the process of comparing the magnitude relations with respect to all the pixel data included in the pixel data group, and extracting and removing the pixel data having the maximum value or the minimum value is repeated a predetermined number of times. There is.

That is, the image reading apparatus and the sensitivity setting method according to the present invention are a regular image reading operation for reading an image of a subject in a photo sensor system having a photo sensor array configured by arranging a plurality of photo sensors. Pixel data obtained from each photosensor that constitutes the photosensor array during the sensitivity adjustment reading operation that is performed independently (at a separate timing) or prior to the regular image reading operation ( It is configured such that a predetermined number of pixel data satisfying a predetermined lightness condition is removed from the lightness data), and an optimum image reading sensitivity setting process is executed based on the pixel data after the removal process.

Specifically, of the pixel data obtained from each photosensor, the pixel data having the maximum or minimum brightness data value is removed, or one pixel data is acquired in the order of increasing or decreasing brightness data value. Alternatively, a plurality of pixel data are uniquely removed. As a result, pixel data detected as an abnormal value such as a bright spot or a dark spot is removed in advance for sensitivity adjustment even when there is an element defect or dust is attached to the detection surface. Since the pixel data corresponding to the original pattern of the image to be read (or the image of the subject to be read in the regular image) can be obtained, the influence of abnormal pixel data can be eliminated and appropriate It is possible to extract and set various image reading sensitivities by a relatively simple processing operation.

Therefore, in the normal reading operation of the object, it is possible to obtain the object image of good image quality with appropriate image reading sensitivity, so that it is possible to suppress the occurrence of malfunction in the fingerprint matching process and improve the matching accuracy. Therefore, it is possible to realize a highly reliable image reading apparatus. In other words, in other words, when the photosensor array has a certain number of element defects,
This means that good image reading sensitivity can be set even if the detection surface is contaminated to some extent. Therefore, it is possible to improve the yield of devices such as the image reading device and the sensor array, and reduce maintenance work.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a photosensor system and a drive control method thereof according to the present invention will be described in detail below. It should be noted that, in the embodiments described below, a case where a double gate type photosensor is applied to the photosensor system according to the present invention will be specifically described, but the present invention is not limited to this and the above-described well-known The photo sensor including the photodiode or the thin film transistor may be applied.

<Double Gate Photo Sensor> First, the basic structure of the double gate photo sensor will be specifically described with reference to the drawings. FIG. 1 is a sectional structural view showing a schematic configuration of a double gate type photo sensor. Figure 1
As shown in (a), the double-gate photosensor 10
Are excited by electrons (in this case, visible light) when excited by light.
A semiconductor layer (channel layer) 11 such as amorphous silicon in which hole pairs are generated, and impurity layers 17 and 18 made of n ⁺ silicon provided at both ends of the semiconductor layer 11 respectively.
And a source electrode 12 and a drain electrode 13 which are selected from chromium, a chromium alloy, aluminum, an aluminum alloy and the like formed on the impurity layers 17 and 18 and which are opaque to visible light,
The block insulating film 14 is provided above the semiconductor layer 11 (above the drawing).
And a transparent conductive layer such as ITO (Indium-Tin-Oxide) formed via the upper (top) gate insulating film 15 to form a top gate electrode (transparent to visible light). The first gate electrode) 21 and chromium (chromium alloy), aluminum, aluminum alloy, or the like formed below the semiconductor layer 11 (below the drawing) via the lower (bottom) gate insulating film 16 and exposed to visible light. And an opaque bottom gate electrode (second gate electrode) 22. The double-gate photosensor 10 having such a configuration is formed on a transparent insulating substrate 19 such as a glass substrate.

Here, in FIG. 1A, the top gate insulating film 15, the block insulating film 14, the bottom gate insulating film 16, and the protective insulating film 20 provided on the top gate electrode 21 are all semiconductor layers. By a material having a high transmittance for visible light that excites 11, such as silicon nitride or silicon oxide,
It has a structure for detecting only light incident from above the drawing.

That is, the double gate type photo sensor 1
0 is an upper MOS transistor formed by the semiconductor layer 11, the source electrode 12, the drain electrode 13 and the top gate electrode 21 with the semiconductor layer 11 as a common channel region, and the semiconductor layer 11, the source electrode 12, the drain electrode 13 and Lower M formed by bottom gate electrode 22
A structure in which two MOS transistors composed of an OS transistor are combined is formed on a transparent insulating substrate 19 such as a glass substrate.

The double gate type photo sensor 10 is generally represented by an equivalent circuit as shown in FIG. Here, TG is the top gate electrode 21.
A bottom gate terminal electrically connected to the bottom gate electrode 22, S a source terminal electrically connected to the source electrode 12, and D a drain electrode 13 Drain terminal that is electrically connected.

Next, a drive control method of the above-mentioned double gate type photo sensor will be described with reference to the drawings. FIG. 2 is a timing chart showing an example of a basic drive control method of the double gate type photo sensor, FIG. 3 is an operation conceptual diagram of the double gate type photo sensor, and FIG. 4 is a double gate type photo sensor. It is a figure which shows the optical response characteristic of the output voltage of. Here, description will be given with reference to the configuration of the above-described double-gate photosensor (FIG. 1) as appropriate.

First, in the reset operation, as shown in FIGS. 2 and 3 (a), the double gate type photo sensor 1 is used.
A pulse voltage (hereinafter referred to as “reset pulse”; for example, a high level of Vtg = + 15V) φT is applied to the top gate terminal TG of 0 to connect the semiconductor layer 11 and the semiconductor layer 11 in the block insulating film 14. The carriers (here, holes) accumulated near the interface are released (reset period Trst).

Next, in the charge accumulation operation, as shown in FIG.
As shown in FIG. 3B, a bias voltage φT of low level (for example, Vtg = −15V) is applied to the top gate terminal TG.
By applying, the reset operation is completed and the charge accumulation period Ta by the carrier accumulation operation (charge accumulation operation) is started. In the charge accumulation period Ta, the semiconductor layer 11 is changed according to the amount of light incident from the top gate electrode 21 side.
Of electrons in the effective incident area of
Hole pairs are generated, near the interface between the semiconductor layer 11 and the semiconductor layer 11 in the block insulating film 14, that is,
Holes are accumulated around the channel region.

In the precharge operation, as shown in FIGS. 2 and 3C, a predetermined voltage (precharge) is applied to the drain terminal D in parallel with the charge accumulation period Ta based on the precharge pulse φpg. Voltage) Vpg is applied to hold the charge in the drain electrode 13 (precharge period Tprch). Next, in the read operation, as shown in FIGS. 2 and 3D, after the precharge period Tprch has passed, the bottom gate terminal BG is set to a high level (for example,
Vbg = + 10V bias voltage (read selection signal;
A double gate type photo sensor 10 is provided by applying φB (hereinafter referred to as “readout pulse”) (selected state).
Is turned on (reading period Tread).

Here, in the read period Tread,
Carriers (holes) accumulated in the channel region act in the direction of relaxing Vtg (-15V) applied to the top gate terminal TG having the opposite polarity, and thus Vbg of the bottom gate terminal BG.
(+ 15V) forms an n-channel, and the voltage of the drain terminal D (drain voltage) VD according to the drain current.
Shows a tendency of gradually decreasing from the precharge voltage Vpg with time, as shown in FIG.

That is, when the charge storage state in the charge storage period Ta is the bright state, as shown in FIG. 3D, carriers (holes) corresponding to the amount of incident light are incident on the channel region.
Is captured, it acts to cancel the negative bias of the top gate terminal TG, and the positive bias of the bottom gate terminal BG causes the double gate type photosensor 10 to be turned on. Then, according to the ON resistance corresponding to the incident light amount, the drain voltage VD is lowered as shown in FIG.

On the other hand, when the charge storage state is dark and no carriers (holes) are stored in the channel region,
As shown in FIG. 3E, by applying a negative bias to the top gate terminal TG, the positive bias of the bottom gate terminal BG is canceled, the double gate type photo sensor 10 is turned off, and as shown in FIG. As shown, the drain voltage (voltage of the drain line 103) VD is maintained almost as it is.

Therefore, as shown in FIG.
The change tendency of the drain voltage VD depends on the top gate terminal TG.
From the end of the reset operation by applying the reset pulse φT to the bottom gate terminal BG.
It is closely related to the amount of light received during the time until B is applied (charge accumulation period Ta), and when there are many accumulated carriers (bright state), it tends to sharply decrease. When it is small (dark state), it tends to decrease gradually. Therefore, the drain voltage VD (=
By detecting Vrd) or by detecting the time until the voltage reaches a predetermined threshold voltage as a reference, the amount of light (irradiation light) incident on the double-gate photosensor 10 is detected. Is converted.

In the timing chart shown in FIG. 2, after the precharge period Tprch has elapsed, the timing chart shown in FIG.
As shown in (f) and (g), if the low level (for example, Vbg = 0V) is applied to the bottom gate terminal BG (non-selected state), the double gate photosensor 10 is kept in the OFF state. Then, as shown in FIG.
The drain voltage VD holds a voltage close to the precharge voltage Vpg. In this way, the selection function of switching the reading state of the double-gate photosensor 10 to the selected / non-selected state is realized depending on the state of the voltage applied to the bottom gate terminal BG.

<Photo Sensor System> Next, a photo sensor system including a photo sensor array configured by two-dimensionally arranging the above-mentioned double gate type photo sensors will be described with reference to the drawings. FIG. 5 is a schematic configuration diagram of a photosensor system including a photosensor array configured by arranging double-gate photosensors two-dimensionally.

As shown in FIG. 5, the photosensor system is roughly classified into a large number of double gate photosensors 10.
Are arranged in a matrix of, for example, n rows × m columns (n and m are arbitrary natural numbers), and the top gate terminal T of each double gate type photosensor 10.
G (top gate electrode 21) and bottom gate terminal BG
A top gate line 101 and a bottom gate line 102 that extend by connecting (bottom gate electrodes 22) in the row direction, and a drain that connects the drain terminal D (drain electrode 13) of each double-gate photosensor 10 in the column direction. Line (data line) 103 and source terminal S
The source line (common line) 104 connected to the source electrode 12 in the column direction and connected to the ground potential
A top gate driver 110 connected to the top gate line 101, a bottom gate driver 120 connected to the bottom gate line 102, a column switch 131, a precharge switch 132, and an amplifier 133 connected to the drain line 103. And a drain driver 130.

Here, the top gate line 101 is integrally formed of a transparent conductive layer such as ITO together with the top gate electrode 21 shown in FIG.
02, drain line 103 and source line 104
Are bottom gate electrode 22, source electrode 12,
The drain electrode 13 and the drain electrode 13 are integrally formed of a material that is opaque to the same excitation light. In addition, the source line 104 has
A constant voltage Vss set according to a precharge voltage Vpg described later is applied, but it may be a ground potential (GND).

In FIG. 5, .phi.tg is a pulse signal .phi.T1, .phi.T2, ... .phi.Tk, ... .phi.T that is selectively output as either the reset voltage or the photocarrier accumulation voltage.
φbg is a control signal for generating n, and φbg is a pulse signal φB1, φB2, ... φBk, ... φBn selectively output as either a read voltage or a non-read voltage.
Φpg is a precharge pulse for controlling the timing of applying the precharge voltage Vpg.

In such a structure, from the top gate driver 110 through the top gate line 101,
By applying a signal φTk (k is an arbitrary natural number; k = 1, 2, ... N) to the top gate terminal TG, a photo sense function is realized, and the bottom gate driver 12
The signal φBk is applied to the bottom gate terminal BG from 0 through the bottom gate line 102, and the drain line 10
The detection signal is taken into the drain driver 130 via the output signal V and the output voltage V of the serial data or parallel data is output.
By outputting as out, the selective reading function is realized.

The drive control method of the photosensor system described above is basically a matrix row forming a photosensor array using the drive control method of the double gate photosensor (see FIG. 2) described above as one processing cycle. This can be realized by repeating for several minutes serially (in time series). For example, if the photo sensor array is highly densified in order to improve the reading accuracy, the time required to read the subject image increases. However, it is not preferable in terms of practical application of the photo sensor system. Therefore, in a photo sensor system using a double gate type photo sensor, for example, as described in Japanese Patent Application Laid-Open No. 2001-148807, the following drive control method is applied to read. The time required can be greatly reduced.

FIG. 6 is a timing chart showing an example of the drive control method of the above-mentioned photosensor system.
Here, the drive control method will be described with reference to the configuration of the photo sensor system shown in FIG. 5 as appropriate. As shown in FIG. 6, first, a reset pulse φT is passed from the top gate driver 110 through the top gate line 101.
1, φT2, ... φTk-1, φTk, ... φTn are sequentially applied to start the reset period Trst, and the double gate photosensor 10 for each row is initialized.

Next, reset pulses φT1, φT2,
.. .phi.Tk-1, .phi.Tk, ... .phi.Tn sequentially fall and the reset period Trst ends, so that the charge accumulation period T
When a starts, charges (holes) are generated and accumulated in the channel region according to the amount of light incident on the double-gate photosensor 10 for each row. Here, as shown in FIG. 6, by applying the precharge pulse φpg to the drain driver 130 in parallel during the charge accumulation period Ta, the precharge period Tprch is started and the precharge voltage Vpg is applied to the drain line 103. Is applied to perform a precharge operation for holding a predetermined voltage on the drain electrode of the double-gate photosensor 10 for each row.

Next, the double-gate type photosensor 1 in which the charge accumulation period Ta and the precharge period Tprch are finished.
0 from the bottom gate driver 120 to the bottom gate line 102 in each row at a timing that does not temporally overlap with the application timing of each signal for the reset operation, the precharge operation, and the read operation in the other row.
Read pulse φB1, φB2, ... φBk-
1, φBk, ... φBn are sequentially applied, and the read period Tr is
Starting ead, the drain voltage VD corresponding to the charges accumulated in the double-gate photosensor 10 for each row
Changes in 1, VD2, VD3, ... VDm are simultaneously detected by the drain driver 130 via each drain line 103 and read as an output voltage Vout composed of serial data or parallel data.

Here, in the present drive control method, reset pulses φT1, φT2, φT3, ... φT for each row.
n, read pulse φB1, φB2, φB3, ... φB
n and the interval (Tdelay) of the application timing of the precharge pulse φpg are as shown in the following formula (1): a reset period Trst by a reset pulse, a read period Tread by a read pulse, and a precharge pulse by a precharge pulse. It is set to a total time of the charging period Tprch or more. Tdelay = Trst + Tprch + Tread (1)

As a result, the reset operation, the precharge operation, and the read operation do not overlap with each other in terms of time, and furthermore, a part of the processing cycle for each row can be overlapped in time. The read operation can be performed before the reset operation in all rows is completed, and the read required time can be significantly shortened while the two-dimensional image read operation is performed well.

<Image Reading Apparatus> Next, an embodiment of the image reading apparatus according to the present invention will be described with reference to the drawings. In the embodiments described below, the above-described double-gate photosensor is applied as the photosensor, and a voltage (reset pulse) is applied with the top gate electrode as the first gate electrode, thereby performing the photosensing function. In addition to the realization, a voltage (readout pulse) is applied with the bottom gate electrode as the second gate electrode to realize the function of reading out the amount of charges accumulated in the channel region.

FIG. 7 is a block diagram showing the overall structure of the image reading apparatus according to the present invention. Here, in FIG.
Description will be given with reference to the configurations of the double-gate photosensor and the photosensor system shown in FIG. 5 as appropriate. The same components as those of the photo sensor system shown in FIG. 5 are designated by the same reference numerals, and the description thereof will be simplified or omitted.

As shown in FIG. 7, the image reading apparatus according to the present embodiment is roughly divided into two-dimensionally arrayed double gate type photosensors 10 like the photosensor system shown in FIG. The top gate terminal TG of the photo sensor array 100 and the double gate type photo sensor 10
Top gate driver 110 that applies a predetermined top gate voltage (reset pulse) to the
And a bottom gate driver 1 for applying a predetermined bottom gate voltage (readout pulse) to the bottom gate terminal BG of the double gate type photo sensor 10 at a predetermined timing.
20, a drain driver 130 including a column switch 131 for applying a precharge voltage to the double-gate photosensor 10 and reading a drain voltage, a precharge switch 132, and an amplifier 133, and a read drain voltage (analog signal ) Is converted into an image output signal (image data) consisting of a digital signal.
Digital converter (hereinafter referred to as "A / D converter")
140 exchanges data with the external function unit 200 that executes predetermined processing such as reading operation control of a subject image by the photo sensor array 100, collation of image data, and processing, and the overall operation of the image reading apparatus. A controller having a function of controlling and executing the above-described image reading operation, and a sensitivity adjusting reading operation and a reading sensitivity setting operation (that is, the sensitivity setting method of the image reading apparatus according to the present invention) described later (sensitivity). It is used as a work area for the adjusting reading unit and reading sensitivity setting unit) 150 and the controller 150, and temporarily stores (stores) acquired image data (pixel data), processing data related to image reading sensitivity setting, and the like. RAM 160, and a ROM 170 for holding the control program of the controller 150 and various control data. And it is configured to have. here,
Photosensor array 100, top gate driver 11
0, bottom gate driver 120, drain driver 1
Since 30 has the same structure and function as the photo sensor system shown in FIG. 5, detailed description thereof will be omitted.

The controller 150 outputs the control signals φtg and φbg to the top gate driver 110 and the bottom gate driver 120, so that each of the top gate driver 110 and the bottom gate driver 120 is output as shown in FIGS. 2 and 6. From the photo sensor array 10
A predetermined signal voltage (reset pulse φTk, read pulse φB is applied to the top gate terminal TG and the bottom gate terminal BG of each double gate type photo sensor 10 that configures 0.
Control the action of applying k).

The controller 150 also controls the precharge switch 132 in the operation of reading the subject image.
By outputting the precharge pulse φpg to the double gate type photosensors 10, the precharge voltage Vpg is applied to the drain terminal D of each double gate type photosensor 10, and the double gate type photosensors 10 corresponding to the read image pattern of the subject.
The column switch 131 detects the drain voltage (data line voltage) VD according to the amount of charge accumulated in
It is converted into a digital signal through the amplifier 133 and the A / D converter 140 and input as image data (image output signal). The controller 150 performs predetermined image processing on the image data, and the RAM 160
The external function unit 200 that performs writing and reading to and from the image processing unit and executes predetermined processing such as collation and processing of image data.
It also has a function as an interface to.

Further, as will be described later, the controller 150 changes and controls the control signals to be output to the top gate driver 110 and the bottom gate driver 120, so that the controller 150 can precede the normal image reading operation or at any timing. An image reading sensitivity that can independently read the image for sensitivity adjustment (reading operation for sensitivity adjustment) and optimally read the subject image according to the surrounding environment such as the state of the subject and the illuminance of external light. That is, the function of setting the optimum charge storage time Ta of the double-gate photosensor 10 (reading sensitivity setting operation) and the reading operation for sensitivity adjustment described above are performed in correspondence with the image pattern of the image for sensitivity adjustment. From the pixel data (brightness data or brightness data; referred to as “brightness data” in this application) to the detection surface. It has a function to remove specific pixel data (specific data removal operation) in order to prevent or suppress the influence of abnormal pixel data caused by foreign matter (dust etc.) that has adhered and element defects existing in the photo sensor array. ing.

<Controller> Next, a specific configuration and operation of the controller applied to the photosensor system according to the present embodiment will be described in more detail with reference to the drawings. First, a specific device configuration of the controller will be described. FIG. 8 is a conceptual configuration diagram showing a configuration example of a controller applied to the photo sensor system according to the present embodiment.

As shown in FIG. 8, the controller 150 according to this embodiment includes a top gate driver 110, a bottom gate driver 120, and a precharge switch 13.
Device controller 151 for controlling the operation in FIG.
And a data controller 152 for writing / reading data to / from the RAM 160 or ROM 170 to manage various data, and these controllers 151,
The main controller 15 that controls the 152 in accordance with a predetermined control program, and also serves as an interface with the external function unit 200 and the like to exchange control signals.
3 and 3.

Further, based on the image data (image output signal) input as a digital signal from the photo sensor array 100 via the A / D converter 140, the controller 150 sets the initial pixel data (image output signal) included in the image data. Hereinafter, for the sake of convenience, the original pixel data will be referred to as "original pixel data") or pixel data after the specific pixel data is removed by the operation of removing the specific pixel data according to the present invention (hereinafter, "after processing" for convenience. (Also referred to as “pixel data”) data for comparing maximum values with each other to extract maximum and minimum values, and for extracting the maximum value of the dynamic range (data range of pixel data group) calculated by the adder 155 described later. A comparator (data comparing means, reading sensitivity extracting means) 154 and a maximum of the processed pixel data extracted by the data comparator 154. Adder for calculating a dynamic range from the difference value and the minimum value (data calculating means) 15
5, the A / D converter 140, the data comparator 154,
The image data and the processed data processed through the adder 155 are input, and these data are stored in a RAM as necessary.
From the data controller 152 and the data selector 156, which controls switching of writing and reading to 160, re-inputting to the data comparator 154 and the adder 155, output to the external function unit 200 via the data controller 152, and the like. The control signal φtg output from the device controller 151 to the top gate driver 110 and the bottom gate driver 120 so as to optimize the image reading sensitivity of the photosensor array 100 based on the control signal of
Sensitivity setting register 15 for setting and controlling the timing of φbg
7 and.

Here, the above-mentioned main controller 15
Reference numeral 3 denotes only specific pixel data based on a predetermined condition extracted by the data comparator 154, for example, only the remaining pixel data group excluding the pixel data having the maximum value or the minimum value of the original pixel data, By writing the data in a predetermined storage area of the RAM 160 via the data selector 156, it is possible to generate a pixel data group (post-processing pixel data) excluding the pixel data having the maximum value or the minimum value. It has a function as a specific data removing unit according to. The operation of removing the specific pixel data by the controller 150 (main controller 153) will be described in detail later.

The optimum image reading sensitivity setting method (reading sensitivity setting operation) set in the photosensor array 100, the top gate driver 110 and the bottom gate driver 120 by the sensitivity setting register 157 is also as follows.
Although details will be described later, for example, the above-described data comparator 1
54 and the adder 155 are used to include the processed pixel data group after specific pixel data is removed from the image data (original pixel data) input from the photosensor array 100 for each reading sensitivity. The maximum value and the minimum value in the reading sensitivity are extracted by comparing the magnitude relationship between pixel data, and the dynamic range (that is, the data range of the lightness data is calculated based on the difference between the maximum value and the minimum value). ), Or the difference between the dynamic ranges for each reading sensitivity (ie,
The minimum value is extracted from the first-order differential value), and the main controller 153 described above uses the image data having a good contrast corresponding to the image pattern of the subject to obtain the reading sensitivity having the dynamic range of the maximum value or the minimum value. Image read sensitivity (charge accumulation period)
Is determined as the optimum value, and the data controller 152 is controlled to output a predetermined control signal to the sensitivity setting register. Therefore, the main controller is
It also has a function as a reading sensitivity determining unit according to the present invention.

<Outline of processing operation in controller>
Next, a schematic processing operation (sensitivity setting method of the image reading apparatus according to the present invention) of the controller having the above-described configuration will be described with reference to the drawings. FIG. 9 is a flowchart showing an example of processing operations realized by the controller applied to the image reading apparatus according to this embodiment. Note that the description will be given here with reference to the configuration of the two-dimensional image reading apparatus shown in FIGS. 7 and 8 as appropriate.

As described above, the controller 150 according to the present embodiment has the following configuration, prior to the regular image reading operation for the subject, or at any timing independent of the regular image reading operation. Each component of the image reading device (photosensor system) is controlled so that the sensitivity adjustment reading operation and the reading sensitivity setting operation are sequentially executed. Here, the series of processing procedures described below are performed by the controller 150, for example, in the ROM 17
The control program previously stored in 0 is the RAM 16
It is realized by being loaded into 0 and executed.

Specifically, as shown in FIG. 9, the processing operation of the controller according to the present embodiment is as follows. First, the main controller 153 performs the sensitivity adjustment reading operation at an arbitrary timing prior to the normal reading operation of the subject. Then, the image reading sensitivity for the reading operation for sensitivity adjustment is set in the sensitivity setting register 157 via the data controller 152, and the image sensor is placed on the detection surface provided on one surface side of the photo sensor array 100. An operation of reading an image for sensitivity adjustment (for example, it may be an image of a subject to be read in a regular image reading operation) is executed (S
101).

Here, the image reading sensitivity set in the sensitivity setting register 157 (that is, the photo sensor array 10).
The charge accumulation period set in each photosensor 10 constituting 0) is, for example, for each row of the photosensor array 100, for each predetermined plurality of rows, or for each screen of the sensitivity adjustment image. Are sequentially controlled to be different, and similarly to the above-described image reading operation (see FIG. 6), the photosensors 10 are sequentially driven for each row, so that a single sensitivity adjustment image is converted into a plurality of different image reading sensitivities. The read operation for sensitivity adjustment is performed. A specific example of the sensitivity adjustment reading operation will be described later in detail. Then, the image data of the sensitivity adjustment image obtained by such a sensitivity adjustment reading operation is temporarily stored in the RAM 160 via the data selector 156 or directly input to the data comparator 154, for example. It

Next, the above step S101 is performed by the data controller 152 via the data selector 156.
Original pixels obtained from each photosensor 10 for each reading sensitivity (that is, for each row, or for each of a plurality of predetermined rows, or for each screen of the sensitivity adjustment image) in the image data obtained by The data (brightness data) is extracted and read into the data comparator 154 (S102).

Next, the data comparator 154 compares the read-out original pixel data with each other to determine whether they are specific pixel data satisfying a predetermined condition, that is, the pixel data having the maximum lightness data value or the lightness. A plurality of pixel data groups (not shown in the figure) are extracted in descending order of data value (S103). Then, for example, the data selector 15
From among the original pixel data group subjected to the comparison processing by the data comparator 154 via 6, the pixel data having the maximum value extracted in this step S103 or only a predetermined number of pixel data groups including the maximum value are excluded. By designating and storing the remaining pixel data group in a predetermined storage area of the RAM 160, a pixel data group (processed pixel data) obtained by removing specific pixel data from the original pixel data group is generated (S
104). A specific example of the specific pixel data removing operation will be described later in detail.

Next, the above-mentioned step S104 is performed by the data controller 152 via the data selector 156.
From the maximum value or the processed pixel data group from which a predetermined number of pixel data groups including the maximum value have been removed, the processed pixel data at a predetermined image reading sensitivity is extracted and read into the data comparator 154 (S105). ), By comparing the magnitude relationship between the processed pixel data for each reading sensitivity, the pixel data having the maximum brightness data value (the brightness data of the pixel having the brightest gradation) and the pixel data having the minimum brightness data ( The brightness data of the pixel having the darkest gradation is extracted (S106).

Then, the adder 155 controlled by the data controller 152 calculates the difference between the maximum value and the minimum value of the pixel data (brightness data) extracted for each reading sensitivity, that is, the dynamic range (data range). Then, the result is sent to RA through the data selector 156.
It is temporarily stored in M160 (S107). Such dynamic range calculation processing is executed for the above-described processed pixel data generated for each reading sensitivity.

Next, the data selector 156 determines the dynamic range for each reading sensitivity stored in the RAM 160.
Via the data comparator 154, and the maximum value that maximizes the dynamic range is extracted from the changing tendency of the dynamic range with respect to the image reading sensitivity (S10).
8) The image reading sensitivity corresponding to the maximum value is extracted and specified. As a result, the main controller 153 sets the specified image reading sensitivity to the optimum image reading sensitivity capable of obtaining a good contrast corresponding to the image pattern of the sensitivity adjustment image (or the regular subject image). To judge. And the main controller 153
Outputs a predetermined control signal to the sensitivity setting register 157 via the data controller 152, rewrites the charge accumulation period corresponding to the optimum image reading sensitivity, and ends the reading sensitivity setting operation. A specific example of the optimum reading sensitivity extraction and setting operation will be described later in detail.

<Reading Operation for Sensitivity Adjustment> Next, the reading operation for sensitivity adjustment (step S101) applied to the processing operation of the above-described controller will be specifically described with reference to the drawings. FIG. 10 is a conceptual diagram showing a specific example of a target area and its reading operation in the sensitivity adjusting reading operation according to the present embodiment, and FIG. 11 is a diagram showing the sensitivity adjusting reading operation according to the present embodiment. FIG. 7 is a conceptual diagram showing another specific example of a target area and its reading operation.

Specifically, the read operation for sensitivity adjustment applied to this embodiment is performed from the device controller 151 to the top gate driver 110 and the bottom gate driver 12.
0, based on each control signal output and set to the precharge switch 132 and the image reading sensitivity (charge accumulation period), similarly to the above-described image reading operation of the photosensor array (see FIGS. 5 and 6). An image for sensitivity adjustment placed on the surface is displayed on the effective reading surface (effective reading area) 30 of the photosensor array 100 as shown in FIG. 10 or in the effective reading surface 30 as shown in FIG. The detection area (detection area) 40 including a predetermined area (row range and column range) set in advance is read.

Here, the image reading sensitivity (that is, the charge accumulation period) set for each photosensor 10 constituting the photosensor array 100 is, for example, for each photosensor group that is simultaneously driven in the reading operation (that is, for each photosensor group).
It may be set so as to be sequentially different for each row), or may be set so as to be sequentially different for each of a predetermined plurality of rows, or the entire effective reading surface 30. Alternatively, it may be set to be different for each entire area of the read image (that is, for each screen) like the entire area of the detection area 40.

A specific method of driving the photosensor 10 in the sensitivity adjustment reading operation is, for example, as shown in FIG.
As shown in FIG. 10A, all the rows in the photosensor array 100 including 256 rows × 196 columns of pixels (that is, 256 × 196 photosensors) may be sequentially read, or FIG. As shown in b), specific rows every plural rows (every 10 rows in this case) such as the 10th row, the 20th row, ... 180th row, 190th row, ... It may be read.

As another specific example of the driving method of the photo sensor 10, an image for sensitivity adjustment is displayed, for example, in FIG.
As shown in (a), the detection area 4 including the row range of the 64th to 191st rows and the column range of the 67th to 130th columns
It is possible to sequentially read all the rows of 0, or as shown in FIG. 11B, the 70th row, the 80th row,
The specific rows of every plural rows (every 10 rows in this case) such as the 180th and 190th rows may be sequentially read.

In the present embodiment, as the area (effective reading surface 30, detection area 40) to be read by the sensitivity adjustment reading operation, the area to be read in the normal image reading operation of the subject is left unchanged. The detection area 40 may be set, and at least the processing operation can be favorably performed in the specific pixel data removing operation and the optimum reading sensitivity setting operation applied to the present embodiment. The number of pixels included in the region (row range and column range) may be set so as to have the necessary minimum (minimum) number of pixel data or more. This allows
The area that is the target of the sensitivity adjustment reading operation according to the present embodiment is the setting area of the above-described detection area 40 (64th line to 1st row).
It is not limited to the 128th row up to the 91st row and the 64th column from the 67th column to the 130th column), and sets a region including a more limited row range (having a small number of pixels) and a column range. May be The minimum necessary area setting that can be set as the detection area will be described later in detail with reference to a specific verification example.

Therefore, in the sensitivity adjusting reading operation according to the present embodiment, the following image reading sensitivity setting operation can be favorably applied. FIG. 12 is a timing chart showing an example of an image reading sensitivity (charge accumulation period) setting operation applicable to the sensitivity adjusting reading operation according to the present embodiment, and FIG. 7 is a timing chart showing another example of an image reading sensitivity (charge accumulation period) setting operation applicable to the reading operation. Here, description will be given with reference to the configuration of the photo sensor system shown in FIGS. 1 and 5 as appropriate.

That is, in the method of driving the photosensor 10 shown in FIGS. 10 and 11, as a method for gradually setting different image reading sensitivities for all rows or a specific row of the photosensor array or the detection area, 12
As shown in FIG. 1, first, with respect to each of the double-gate type photosensors 10 constituting the photosensor array 100,
Reset pulse φT1, φT2, ... φT all at once
n is applied to execute the reset operation to simultaneously start the charge accumulation periods T ₁ , T ₂ , ... T _n-1 , T _n of the double-gate photosensors 10 in all rows,
Precharge signal φpg and read pulses φB1 and φ applied to the double-gate photosensor 10 for each row
B2, ... φBn at a predetermined time interval (delay time Tdelay)
By gradually changing the timings of the precharge operation and the read operation in the double-gate photosensor 10 for each row, the charge accumulation periods T ₁ , T ₂ , ... T set for each row are set. _n-1 , T _n
Are controlled so as to mutually change at the time interval (Tdelay).

As a result, in the sensitivity adjustment reading operation, each row as the object of the reading operation (see FIGS. 10 and 1 above).
As shown in FIG. 1, all the rows may be read, or a specific row may be read. It can be acquired by the reading operation of the sensitivity adjustment image (subject image) (for one screen).

Further, as another method of setting the image reading sensitivity according to the present embodiment, as shown in FIG. 13, first, for the double gate type photosensor 10 for each row forming the photosensor array 100, sequentially reset pulse φT1 at a predetermined time interval in the forward direction of the n-th row from the first row (delay time Tdelay), .phi.T2, with reset operation by applying a ... .phi.Tn, the charge accumulation period TA _1, TA _2, … T
After starting A _n-1 and TA _n , the precharge signal φpg and the read pulses φBn and φBn− are reversed at a predetermined time interval (delay time Tdelay) from the nth row to the first row.
1, ... .phi.B2, by sequentially applying .phi.B1, charge accumulation period is set for each line _TA 1, _TA 2, ... _TA
n-1 and TA _n are set to a predetermined time interval (the delay time Tde
It is controlled so as to change each other at a time twice the lay).

As a result, the delay time Tde is set for each row as the target of the reading operation (may be all rows as shown in FIGS. 10 and 11 or may be a specific row).
Image data read at different image reading sensitivities having a time interval twice as long as lay can be acquired by one reading operation of the image for sensitivity adjustment, and compared with the method shown in FIG. Image data read with a sensitivity setting width equal to or more than the number of read lines can be acquired.

The method of setting the image reading sensitivity (charge accumulation period) applied to the image reading apparatus according to the present invention is not limited to the method shown in each of the specific examples described above.
If the image for sensitivity adjustment or the subject image can be read with different reading sensitivities and the image data can be acquired, for example,
After reading one screen of the sensitivity adjustment image with a single reading sensitivity, the operation of changing the reading sensitivity and reading the one screen of the sensitivity adjustment image again is repeated a plurality of times to obtain image data with different reading sensitivities. Needless to say, it may be obtained by any other method.

<Specific Pixel Data Removal Operation> Next, the specific pixel data removal operation (steps S103 and S104) applied to the above-described processing operation of the controller will be described by showing a specific example. Among the specific pixel data removal operations applied to the present embodiment, the following method may be applied particularly as the operation of extracting one or more pixel data in descending order of lightness data value. it can. Specifically, first, step S as described above.
In 103, a data comparator 154 is provided for each reading sensitivity.
The magnitude relationship of the brightness data values of the original pixel data read in is compared with each other, and the original pixel data is stored in the RAM 160 via the data selector 156 so as to be sorted in the descending order of the brightness data value.

Then, in steps S104 to S106, the RAM 160 is used to calculate the dynamic range.
When the pixel data stored in the data comparator 154 is read into the data comparator 154 again, the i-th order (i is an arbitrary natural number) from the arrangement of the rearranged original pixel data group for each reading sensitivity in descending order of lightness data value. Up to a predetermined number of pixel data are uniquely excluded and designated, and the pixel data having the maximum lightness data value in the array of the remaining pixel data group (corresponding to the processed pixel data) (that is, The pixel data located next to the pixel data specified to be excluded) and the pixel data having the smallest brightness data value in the array (that is, the pixel data located at the end of the array) are respectively the maximum value and the minimum value. The value is read out via the data selector 156, and the adder 155 calculates the difference between the maximum value and the minimum value of the pixel data (that is, the dynamic range).

According to this, by comparing the pixel data with each other and rearranging the pixel data based on the size relationship, the original pixel data group
Pixel data with the maximum brightness value (the highest brightness) or a predetermined number of pixel data from the one with the largest brightness data value is uniquely excluded, and the maximum and minimum values from the processed pixel data group Pixel data that becomes

FIG. 14 is a conceptual diagram showing another method of the specific pixel data removing operation applied to this embodiment.
Note that, here, a case where a different image reading sensitivity is set for each row will be described. Another method of the specific pixel data removing operation applied to this embodiment is as follows. First, in step S103 as described above, the original pixel data read by the data comparator 154 for each row (for each reading sensitivity). Comparing the size relationship of the pixel data of pixels (photosensors) arranged adjacent to each other on the photosensor array to the group, for example, by sequentially extracting larger pixel data from the first pixel of the row. To do.

Specifically, as shown in FIGS. 14A and 14B, in the pixel data group (m pieces) for one row, the pixel data of the first pixel (first pixel data) and the two pixels Pixel data having a larger (higher lightness) lightness data value is extracted by comparing with the pixel data of the eye (second pixel data), and then the extracted pixel data and the pixel data of the third pixel ( The third pixel data) is further compared to extract the pixel data having the larger lightness data value until the m-th pixel data in the row.

According to this, by comparing the pixel data of each adjacent pixel, only the pixel data having the larger lightness data value is always extracted and becomes the target on the one side in the next comparison process. Minute pixel data group, by sequentially repeating the above comparison and extraction processing,
Only the pixel data having the maximum lightness data value (the highest lightness) is extracted.

On the other hand, as shown in FIGS. 14C and 14D, in the above-described comparison and extraction processing, the pixel data having the smaller lightness data value (lower lightness) is extracted, for example, the data selector. The pixel data group is sequentially stored in a predetermined storage area of the RAM 160 via the 156, and after the pixel data extraction processing that maximizes the brightness data value is finished, the pixel data group is read again to the data comparator 154 to perform the above-described comparison. Similarly to the extraction processing, the first pixel data (the pixel data with lower lightness obtained by comparing the first pixel data and the second pixel data) and the second pixel data (the first pixel data and the second pixel data Among them, the pixel data having the higher lightness and the pixel data having the lower lightness obtained by comparing the third pixel data) are compared with each other to extract the pixel data having the higher lightness data value (higher lightness). And, then, the process of extracting the larger of the pixel data of the brightness signal value by further comparing the pixel data and third pixel data the extracted,
The (m-1) th pixel data of the row is executed.

According to this, from the remaining pixel data group from which the pixel data having the maximum lightness data value (the highest lightness) is extracted, the one having a larger lightness data value is always compared by comparing the pixel data with each other. Since the processing of extracting only the pixel data of 1 is sequentially and repeatedly executed, only the pixel data having the second highest brightness data value in the reading sensitivity (row) is extracted. Then, such comparison and extraction processing of pixel data are performed i times (i
Is an arbitrary natural number), and the i-th predetermined number of pixel data are extracted in descending order of lightness data value.

Here, when only one pixel data having the maximum lightness data value is set to be removed from the original pixel data group for each reading sensitivity, the element defect of the photo sensor forming the photo sensor array is detected. This is effective in eliminating the influence of abnormal pixel data that is caused. That is, according to the verification by the inventor of the present application, the number of occurrences of element defects at the actual product level in the photosensor system applicable to the present embodiment is approximately one per row forming the photosensor array. Since there is almost no element defect in one row, it is possible to favorably apply the simple method of removing only the pixel data having the maximum brightness data value.

On the other hand, a method in which a predetermined number (plurality) of pixel data are removed from the original pixel data group for each reading sensitivity from the one having the highest lightness data value is set on the detection surface on the photosensor array. Relatively large foreign matter that adheres,
It can be effectively applied when eliminating the influence of abnormal pixel data due to an element defect that occurs across a plurality of pixels.

In each method applied to the above-described operation of removing the specific pixel data, element defects or element characteristics of the photosensors constituting the photosensor array may vary, or foreign matter may adhere to the detection surface. , When there is an abnormal pixel (bright spot defect) that becomes a bright spot, pixel data having the maximum brightness data value from the original pixel data group, or a predetermined number of pixel data groups having a large brightness data value including the maximum value Although only the method of uniquely extracting and removing is described, the present invention is not limited to this.
It is also possible to uniquely exclude only pixel data having a minimum brightness data value or a predetermined number of pixel data groups having a small brightness data value including the minimum value.

According to this, even when a defect point defect in which a foreign substance attached to the detection surface is detected to be relatively dark (black) with respect to the surrounding image pattern, an abnormal pixel is detected. Pixel data can be uniquely removed before the optimum reading sensitivity extraction and setting operation is started to prevent or suppress the image reading sensitivity from being set in a direction higher than the originally appropriate state. Therefore, it is possible to obtain a subject image with good image quality in a regular image reading operation.

Further, as described above, when the minimum required number of pixel data for appropriately executing the extraction and setting operation of the optimum reading sensitivity can be secured, a predetermined number of the lightness data values are arranged in descending order. It is also possible to exclude both the pixel data group and the predetermined number of pixel data groups in ascending order of lightness data values, thereby eliminating the effects of both the bright spot defect and the dark spot defect.

<Detection Area Region Setting Conditions> Here, the number of removable specific pixel data in the above-described specific pixel data removing operation and the detection area region setting in the sensitivity adjustment reading operation will be specifically verified. To do. As described above, in the operation of removing the specific pixel data according to the present embodiment, a predetermined number (a plurality of) of which the brightness data value is maximum or minimum is selected from the pixel data group (original pixel data group) for each reading sensitivity. However, in order to shorten the reading operation time in the above-described sensitivity adjustment reading operation, the target area (that is, the detection area 40) is made small without any conditions or restrictions (the number of pixels). If the setting is set to (less), a plurality of pixel data are uniquely removed by the above specific pixel data removal operation, and the number of pixel data after processing is reduced, so that the optimum reading sensitivity extraction and setting operation is normal. May not be executed.

Therefore, in the area to be subjected to the sensitivity adjustment reading operation, even if the predetermined number of pixel data are removed in the removal operation of the specific pixel data, the extraction and setting operation of the optimum reading sensitivity is satisfactorily performed. It is necessary to set the necessary minimum number of pixels (or row range and column range) in advance so that the number of pixel data can be executed.

Specifically, according to the verification by the inventor of the present application, when the image reading apparatus according to the present embodiment is applied to a fingerprint reading apparatus, in general, the interval between light and dark stripes (bright and dark patterns) of an adult fingerprint is It is known that the distance is about 300 μm. On the other hand, in the photo sensor array applied to the image reading apparatus according to the present embodiment, the interval between pixels (double gate type photo sensor) is reduced to about 50 μm. Therefore, approximately 6 pixels are required to detect one bright and dark fringe of the fingerprint image.

On the other hand, in the operation of extracting and setting the optimum reading sensitivity as described above, in order to ensure the accuracy of extracting the more optimum image reading sensitivity, at least a number corresponding to at least about 8 light and dark stripes (generally A pixel data group of about 48 pixels) is required. Therefore, by removing the specific pixel data as described above, in order to eliminate the influence of abnormal pixel data due to element defects and the adhesion of foreign matter to the detection surface,
For example, when the condition is set to remove about 10 pieces of pixel data, at least about 10 bright and dark stripes are set for each image reading sensitivity (for example, for each row) as a target area of the sensitivity adjustment reading operation. By setting the number of pixels corresponding to the above (about 60 pixels),
Even when 0 pixels are removed as pixel data having a large lightness data value, a pixel data group having the number of pixels (approximately 50 pixels) that can sufficiently secure the extraction accuracy of the optimum image reading sensitivity may remain. it can.

As described above, the detection area in the above-described read operation for sensitivity adjustment should ensure sufficient extraction accuracy of the optimum image reading sensitivity based on the image pattern of the subject in the operation of extracting and setting the optimum reading sensitivity. The minimum number of pixels that can be removed and the specific pixel data removal operation based on the frequency of element defects that occur in the photo sensor array and the size of foreign matter that adheres to the detection surface in the specific pixel data removal operation. The number of pixels (or row range and column range) included in the area is set using the number and the like as parameters. It should be noted that the present verification example shows only one example when the image reading device according to the present embodiment is applied to the fingerprint reading device, and the present invention is not limited to this, and the above-described subject It goes without saying that it is appropriately set according to the image pattern, the manufacturing accuracy of the photo sensor, the usage environment of the image reading apparatus, and the like.

Next, the effectiveness of the above-described image reading apparatus according to the present invention when applied to a fingerprint reading apparatus will be described by showing some experimental data while comparing it with the conventional method. Note that, here, with reference to the sensitivity setting operation (FIG. 9) of the image reading apparatus shown in the above-described embodiment, the optimum reading sensitivity extraction and setting operation (step S10).
6 to S109) will also be described.

FIG. 15 shows that in the image reading apparatus according to the present embodiment, a reading operation for sensitivity adjustment is performed by a photosensor array having an abnormal pixel due to an element defect (bright spot defect) or the like, and a subject image (sensitivity) is detected. 16 is an experimental image showing an image pattern of a fingerprint when the adjustment image) is read.
FIG. 17 is a schematic diagram showing changes in pixel data (brightness data) in an arbitrary row of the fingerprint image obtained by the sensitivity adjustment reading operation, and FIG. 17 is a fingerprint image obtained by the sensitivity adjustment reading operation. It is a figure which shows the change of the dynamic range based on the pixel data (lightness data) obtained from, and the correspondence table of a line number, a dynamic range, and image reading sensitivity (charge accumulation period).

FIG. 18 shows the fingerprint image pattern when the image reading sensitivity is set using the photosensor array having abnormal pixels and the sensitivity setting method of the image reading apparatus according to the present embodiment. 3 is an experimental image showing the image pattern of the fingerprint of FIG. Then, FIG. 19 is a schematic diagram showing changes in pixel data (brightness data) obtained by the specific pixel data removal operation according to the present embodiment, and FIG.
Is the change in the dynamic range based on the pixel data (brightness data) obtained by the specific pixel data removal operation according to the present embodiment, and the row number and the dynamic range,
It is a figure which shows the correspondence table with image reading sensitivity (charge accumulation period).

First, as shown in FIG. 15A, an image pattern (fingerprint) of a finger FG, which is a subject in a normal image reading operation, is used as an image for sensitivity adjustment, and at least 256 rows × 196 columns of pixels are used. Line range (128 lines) preset from the 64th line to the 191st line within the effective reading surface 30 of the photosensor array 100 including (photosensors)
And the image area of the finger FG by sequentially setting different charge accumulation periods in the photosensor group for each row as described above with respect to the detection area 40 including the column range of the 67th column to the 130th column (64 columns). By executing the sensitivity adjustment reading operation for reading, a fingerprint image in which the image reading sensitivity is gradually different for each row is obtained by the image reading operation for one screen, as shown in FIG. 15B. Here, the photo sensor array 100 shown in FIG. 15A has an element defect (not shown), and as shown in FIG. 15B, it is abnormally high in the fingerprint image in the detection area 40. A bright spot defect IL indicating a lightness data value has occurred.

In such a fingerprint image, as shown in FIG. 16, for example, 256 gradations are set between the light state (observed as white) and the dark state (observed as black) of the lightness data value. When setting and verifying the change of the brightness data value in each pixel of any row (image reading sensitivity), for example,
As shown in FIG. 16B, pixel data having an abnormally high lightness data value is observed in the 104th row and column number Rp corresponding to the position where the bright spot defect IL shown in FIG. 15B occurs. It was In addition, in FIG. 16, as an arbitrary line in the detection area 40, for convenience sake, the 80th line, the 104th line, and the 128th line.
The change tendency of the lightness data value for each column is shown for the rows, the 152nd row and the 176th row.

Here, in the above-described sensitivity setting method in the prior art, irrespective of the presence / absence of abnormal pixels (bright spot defects IL) as shown in FIGS. 15 and 16, each row (each image reading sensitivity). Since the maximum value and the minimum value of the brightness data value are extracted and the dynamic range is calculated from the difference between them, the brightness data value of the pixel is saturated by the bright spot defect IL existing on the 104th line. By indicating the maximum value, as shown in FIGS. 17A and 17B, the apparent maximum value MA2 appears on the 104th line where the dynamic range is originally different from the line number RCa indicating the maximum value MA1. to, the maximum value 104 line to set image reading sensitivity showing a MA2 (i.e., charge accumulation period T ₁₀₄ of the _photosensor) to determine incorrectly that the optimal image reading sensitivity I had a problem.

Then, as shown in FIG.
When the image reading sensitivity of the fourth line is set lower than the optimum image reading sensitivity (the charge accumulation period is short), the erroneous image reading sensitivity is set and the normal image reading sensitivity is set. When the image reading operation is executed, as shown in FIG. 18A, it is possible to obtain a subject image that is dark and has a low image quality. In the fingerprint collation processing for authentication, there is a possibility that a malfunction may occur and the collation accuracy may deteriorate.

On the other hand, in the image reading device and the sensitivity setting method according to the present invention, as shown in FIG. 15B, the fingerprint image is bright due to the element defect existing in the photosensor array. When the point defect IL occurs, the specific pixel data removal operation as described above causes the pixel data group for each image reading sensitivity (for each row) to have a larger lightness data value, as shown in FIG. By performing a process of uniquely removing one or more (in FIG. 19, one case is shown; the position of the removed pixel data for each row is indicated by an arrow) uniquely, FIG. ), At least the pixel data of the column number Rp for which the lightness data value is observed to be abnormally high will always be removed.

Here, in the operation of removing the specific pixel data according to the present invention, as shown in FIGS. Also, the pixel data having the maximum brightness data value is removed, but as shown in FIG. 20A, the dynamic range change tendency in each row does not change significantly, so that the dynamic range is originally , The row number RCa indicating the maximum value MA1 is specified well, and FIG.
As shown in (b), the image reading sensitivity (charge accumulation period T ₁₇₆ ) set for the row (for example, the 176th row) can be extracted and set as the optimum image reading sensitivity.

Therefore, when the normal image reading operation is executed with such an optimum image reading sensitivity, as shown in FIG. 18B, the contrast of the light and dark of the image pattern is generally good, and the object of high image quality is obtained. Since an image is obtained, it is possible to prevent or suppress the occurrence of malfunction in the fingerprint matching process. This means that good image reading sensitivity can be set even if the photosensor array has a certain number of element defects or the detection surface has some dirt. In other words, it means that it is possible to provide an effective technique capable of improving the yield of devices such as an image reading device and a sensor array and reducing maintenance work.

In the removal operation of the specific pixel data described above, even when a plurality of pixels are removed in the order of increasing brightness data value, the dynamic range of each row to be the target of the operation of extracting the optimum reading sensitivity is different. As in the case shown in FIG. 20 (a), the changing tendency does not change significantly. Therefore, similarly to the case described above, the row number RCa at which the dynamic range shows the maximum value is satisfactorily specified and optimized. It is possible to set various image reading sensitivities.

[0115]

As described above, according to the photo sensor system and the drive control method thereof according to the present invention, in the photo sensor system including the photo sensor array configured by arranging a plurality of photo sensors, Pixels obtained from each photosensor that constitutes a photosensor array during a sensitivity adjustment reading operation that is performed independently of a normal image reading operation for reading an image or prior to the above-mentioned normal image reading operation. Pixel data having the maximum or minimum brightness data value is removed from the data (brightness data), or one or a plurality of pixel data is uniquely removed from the pixel data in the descending order of brightness data value. Since the setting processing of the optimum image reading sensitivity is executed based on the pixel data after the removal processing, Even when there are element defects in the photo sensor array or dust on the detection surface, the influence of abnormal pixel data such as bright spots or dark spots is eliminated, and appropriate image reading sensitivity is obtained. Can be set by a relatively simple processing operation.

Therefore, in the normal reading operation of the subject, it is possible to obtain the subject image of good image quality with appropriate image reading sensitivity, so that it is possible to suppress the occurrence of malfunctions in the fingerprint matching process and improve the matching accuracy. Therefore, it is possible to realize a highly reliable image reading apparatus. Also, from this, it is necessary to set a good image reading sensitivity even when the photo sensor array has a certain number of element defects or the detection surface has some dirt. Therefore, it is possible to improve the yield of devices such as the image reading device and the sensor array, and reduce maintenance work.

[Brief description of drawings]

FIG. 1 is a cross-sectional structural view showing a schematic configuration of a double-gate type photosensor applicable to an image reading apparatus according to the present invention.

FIG. 2 is a timing chart showing an example of a basic drive control method of a double gate type photo sensor.

FIG. 3 is an operation conceptual diagram of a double gate type photo sensor.

FIG. 4 is a diagram showing an optical response characteristic of an output voltage of a double gate type photo sensor.

FIG. 5 is a schematic configuration diagram of a photosensor system including a photosensor array configured by arranging double-gate photosensors two-dimensionally.

6 is a timing chart showing an example of a drive control method of the photo sensor system shown in FIG.

FIG. 7 is a block diagram showing the overall configuration of an image reading apparatus according to the present invention.

FIG. 8 is a conceptual configuration diagram showing a configuration example of a controller applied to the photo sensor system according to the embodiment.

FIG. 9 is a flowchart showing an example of processing operation realized by a controller applied to the image reading apparatus according to the present embodiment.

FIG. 10 is a conceptual diagram showing a specific example of a target area and a reading operation in the sensitivity adjusting reading operation according to the present embodiment.

FIG. 11 is a conceptual diagram showing another specific example of the target area and the reading operation in the sensitivity adjusting reading operation according to the present embodiment.

FIG. 12 is a timing chart showing an example of an image reading sensitivity (charge accumulation period) setting operation applicable to the sensitivity adjustment reading operation according to the present embodiment.

FIG. 13 is a timing chart showing another example of an image reading sensitivity (charge accumulation period) setting operation applicable to the sensitivity adjustment reading operation according to the present embodiment.

FIG. 14 is a conceptual diagram showing another method of a specific pixel data removal operation applied to this embodiment.

FIG. 15 is an experimental image showing an image pattern of a fingerprint when a subject image (image for sensitivity adjustment) is read by a photo sensor array having abnormal pixels.

FIG. 16 is a schematic diagram showing changes in pixel data (brightness data) in an arbitrary row of the fingerprint image obtained by the sensitivity adjustment reading operation.

FIG. 17 shows a change in dynamic range based on pixel data (brightness data) obtained from a fingerprint image obtained by the above-described read operation for sensitivity adjustment, and line number and dynamic range, and image reading sensitivity (charge accumulation period). It is a figure which shows the correspondence table of.

FIG. 18 is an image pattern of a fingerprint when the image reading sensitivity is set using a photo sensor array having abnormal pixels and a fingerprint image pattern when the sensitivity setting method of the image reading apparatus according to the present embodiment is applied. It is an experimental image showing.

FIG. 19 is a schematic diagram showing changes in pixel data (brightness data) obtained by the specific pixel data removal operation according to the present embodiment.

FIG. 20 shows changes in the dynamic range based on the pixel data (brightness data) obtained by the specific pixel data removal operation according to the present embodiment, and the line number, the dynamic range, and the image reading sensitivity (charge accumulation period). It is a figure which shows a correspondence table.

[Explanation of symbols]

10 Double gate type photo sensor 30 Effective reading surface 40 detection areas 100 photo sensor array 150 controller 153 Main controller 154 Data comparator 155 adder 157 Sensitivity setting register

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 1/19 H04N 1/04 103Z 5/335 G01B 11/24 K F H01L 27/14 C F term (reference) 2F065 AA54 CC16 FF04 JJ03 JJ26 QQ29 QQ31 UU05 4M118 AA06 AB01 BA05 CA11 CB06 FB03 FB09 FB13 5B047 AA25 AB02 BA02 BB04 CB05 CB12 DA06 DC02 DC09 5C024 CX11 CX26 GY31 HX02 HX20 HX28 A06A08 FB02 AFB06 A0806 AFB06 AFB06 FA02 FB02 AFB06A02

Claims (16)

[Claims] 1. An image reading device, comprising a photo sensor array including a plurality of photo sensors, for reading an image of an object placed on a detection surface of the photo sensor array, the image reading device being applied to a normal image reading operation for the object. In the sensitivity adjustment reading operation for setting the image reading sensitivity, the sensitivity adjusting reading unit that changes the image reading sensitivity for each pixel data group to read a predetermined image for sensitivity adjustment, and the sensitivity adjusting reading unit. Specific data removing means for removing specific pixel data from the pixel data group for each of the image reading sensitivities associated with the image pattern of the predetermined image read by means, and the pixel data group excluding the specific pixel data Based on the above, a reading sensitivity setting operation for performing the reading sensitivity setting operation for setting the image reading sensitivity suitable for the regular reading operation of the subject image. An image reading apparatus comprising: a step. 2. The reading sensitivity setting means at least compares the pixel data belonging to the pixel data group from which the specific pixel data has been removed by the specific data removing means with each other, and compares the pixel data with each other. Data comparing means for extracting pixel data having a maximum value and a minimum value from the group, and at least based on the maximum value and the minimum value of the pixel data extracted by the data comparing means, for each of the image reading sensitivities. Data calculation means for calculating a data range of the pixel data group, and the image reading sensitivity having a maximum data range of the data ranges of the pixel data group for each image reading sensitivity calculated by the data calculation means And a reading sensitivity extracting means for extracting the image reading sensitivity, the extracted image reading sensitivity during the regular image reading operation for the subject. The image reading apparatus according to claim 1, characterized in that it has a reading sensitivity determining means for determining an image reading sensitivity, and. 3. The specific data removing means removes at least the maximum or minimum pixel data from the pixel data group obtained for each image reading sensitivity by the sensitivity adjustment reading operation. The image reading apparatus according to claim 1, wherein 4. The specific data removing unit removes a plurality of the pixel data from the maximum value in the descending order of the pixel data group obtained for each of the image reading sensitivities by the sensitivity adjusting reading operation. The image reading apparatus according to claim 3, wherein 5. The specific data removing means removes a plurality of the pixel data from the smallest value in the pixel data group obtained for each image reading sensitivity by the sensitivity adjustment reading operation. The image reading apparatus according to claim 3, wherein 6. The reading means for sensitivity adjustment, in the reading operation for sensitivity adjustment, sets different image reading sensitivities stepwise for each predetermined number of rows of the photosensor array,
The image reading apparatus according to claim 1, wherein the predetermined image for adjusting the sensitivity is read only once. 7. The sensitivity adjusting reading means, in the sensitivity adjusting reading operation, reads the predetermined image for sensitivity adjusting in the entire effective reading area of the photosensor array. 7. The image reading device according to any one of 1 to 6. 8. The sensitivity adjustment reading means reads the predetermined image for sensitivity adjustment only in a detection area preset in an effective reading area of the photosensor array in the sensitivity adjustment reading operation. The image reading device according to any one of claims 1 to 7, wherein 9. In the detection area, at least the minimum number of pixel data by which the reading sensitivity setting operation by the reading sensitivity setting unit can be normally performed is included in the pixel data group excluding the specific pixel data. The image reading apparatus according to claim 8, wherein the image reading apparatus is set in an obtained area. 10. The image reading apparatus according to claim 1, wherein the pixel data is brightness data corresponding to an image pattern of the predetermined image. 11. The photosensor comprises a source electrode and a drain electrode formed by sandwiching a channel region made of a semiconductor layer, and a first electrode formed at least above and below the channel region with an insulating film interposed therebetween. A gate electrode and a second gate electrode are provided, and one of the first gate electrode and the second gate electrode is a light irradiation side, and the light is irradiated from the light irradiation side during a predetermined charge accumulation period. 11. The structure according to claim 1, wherein charges corresponding to the amount of the generated light are generated and accumulated in the channel region, and the pixel data is generated based on the amount of the accumulated charges. The image reading device according to any one of 1. 12. The read sensitivity setting means arbitrarily adjusts the image read sensitivity by controlling a charge accumulation period in the photosensor in the read sensitivity setting operation. 11. The image reading device according to any one of 11. 13. A photosensor array comprising a photosensor array comprising a plurality of photosensors, wherein the photosensor array is configured in a sensitivity setting method for reading an image of a subject placed on a detection surface of the photosensor array. The procedure of changing the image reading sensitivity in a plurality of steps for each photosensor to read a predetermined image for sensitivity adjustment, and the image pattern of the predetermined image read for each image reading sensitivity. A procedure of removing specific pixel data from the pixel data group, and a procedure of setting an image reading sensitivity suitable for a regular reading operation of the subject image based on the pixel data group from which the specific pixel data is removed. And a sensitivity setting method for an image reading apparatus. 14. The procedure of removing the specific pixel data is to remove at least the maximum or minimum value of the pixel data from the pixel data group obtained for each image reading sensitivity. Item 14. A method for setting the sensitivity of the image reading apparatus according to Item 13. 15. The procedure of removing the specific pixel data is performed by comparing the size of all the pixel data included in the pixel data group obtained for each of the image reading sensitivities and comparing the pixel data with each other. 15. The image according to claim 13 or 14, further comprising: a process of rearranging in order, and a process of removing a predetermined number of the pixel data from an arbitrary end in the rearranged array of the pixel data. How to set the sensitivity of the reader. 16. The procedure of removing the specific pixel data is performed by comparing the magnitude relationship with all pixel data included in the pixel data group obtained for each image reading sensitivity, and comparing the maximum value or 15. The sensitivity setting method for an image reading apparatus according to claim 13, wherein the process of extracting and removing the pixel data having the minimum value is repeated a predetermined number of times.