JP2003256820A - Image reading device and its sensitivity setting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading device and its sensitivity adjusting method capable of setting proper image reading sensitivity by removing the influence of any abnormal pixel data detected due to any abnormal pixel or the like, and obtaining a satisfactory subject image by a specific image reading operation. <P>SOLUTION: A controller 150 is provided with a function (reading sensitivity setting operation) for performing an operation (reading operation for adjusting sensitivity) for reading an image for adjusting sensitivity in an arbitrary timing prior to a specific image reading operation, and for optimally reading the subject image, for setting image reading sensitivity, and a function for setting the optimal image reading sensitivity by reading a prescribed image several number of times under different sensitivity conditions, and comparing pixel data (lightness data) obtained under each sensitivity condition, and detecting any abnormal pixel existing in a photo-sensor array (abnormal pixel detecting operation), and removing the influence of the pixels (abnormal pixel removing 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
A subject image is read by executing a series of operation steps (reset operation → charge accumulation operation → precharge operation → readout operation) for reading out to detect light and dark information.

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 the photosensor system to which various photosensors such as the double gate type photosensor are applied, as described above, the subject is detected based on the amount of electric charge generated according to the image pattern of the subject. Since the image is read, it is easily affected by various external fluctuation factors such as the environmental illuminance at the place of use such as indoors and outdoors and the brightness of the subject itself. Therefore, 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) in accordance with the situation of the above-mentioned fluctuation factors.

The appropriate reading sensitivity in the photo sensor is
Conventionally, a standard sample placed on the detection surface before the normal scan operation is provided or a circuit for detecting the ambient illuminance is provided separately because it differs depending on the ambient conditions such as the ambient illuminance. The reading operation is performed by changing the reading sensitivity in multiple stages (hereinafter referred to as "sensitivity reading operation"), and based on the detection result and the reading result, the optimum reading according to the fluctuation factors such as environmental illuminance. The method of seeking 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 the 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 (the difference between the maximum value and the minimum value of the brightness data; dynamic range) calculated from the brightness data detected for each line (that is, for each reading sensitivity) of reading, the optimum image reading state is obtained. A method is to extract a certain row (row that maximizes the dynamic range) and set the reading sensitivity (charge accumulation period) set in that row as the optimum sensitivity as the reading sensitivity during the normal image reading operation of the subject. Have been described.

[0013]

However, the above-mentioned conventional techniques have the following problems. That is, abnormal pixel data (such as bright spots or dark spots) in the sensitivity adjustment reading operation due to element defects of the photosensors constituting the photosensor array, variations in element characteristics, or adhesion of foreign matter to the detection surface ( When there is a pixel (brightness data) for which the brightness data) is detected, if the pixel data for each row obtained by the sensitivity adjustment reading operation is used as is, the dynamic range originally calculated based on appropriate pixel data Since the dynamic range is maximized in a row different from the row in which is maximized, there is a problem that inappropriate image reading sensitivity is extracted and set. Therefore, the image quality of the subject image acquired by the regular image reading operation is deteriorated,
For example, when an image reading device equipped with such a photo sensor array is applied to a fingerprint collation device, there is a possibility of causing malfunction in the fingerprint collation processing.

Here, in order to avoid the problem that the inappropriate image reading sensitivity is set by the abnormal pixel, it is conceivable to perform the data processing of extracting and removing the lightness data detected by the abnormal pixel. However, even in this case, in the method of the related art as described above, in order to uniquely extract the optimum image reading sensitivity from the row having the maximum dynamic range, each row and the row are set. Since the relationship with the image reading sensitivity is fixedly defined, if there is an abnormal pixel in the row that originally shows the optimum image reading sensitivity (that is, the row with the maximum dynamic range), the pixel data of that row will be displayed. Is removed by the above data processing, and the optimum image reading sensitivity is not set (the image reading sensitivity that is deviated from the optimum image reading sensitivity is set)
There was a possibility.

Further, when data processing for extracting and removing such abnormal pixel data is performed, the sensitivity setting operation becomes complicated and it is necessary to provide a processing circuit for the data processing. There is a problem that the time required for the sensitivity setting operation including the above becomes long, the related peripheral circuits become complicated, the circuit configuration becomes large, and the product cost rises.

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 normal 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 and setting an appropriate image reading sensitivity, thereby obtaining a good subject image in a normal image reading operation, and the same. It is an object to provide a sensitivity adjustment method.

[0017]

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, a plurality of different sensitivity conditions are set for a predetermined reading target area of the photo sensor array, and a predetermined target image is read for each of the sensitivity conditions and belongs to the first pixel data group. An abnormal pixel detecting means for detecting an abnormal pixel based on a comparison of pixel data for each of the sensitivity conditions in a specific pixel, and the predetermined target image are read to obtain the influence of the abnormal pixel. Reading sensitivity setting means for setting an image reading sensitivity suitable for a normal reading operation of the subject image based on the second pixel data group,
It is characterized by having.

An image reading apparatus according to a second aspect of the present invention is the image reading apparatus according to the first aspect.
In the image reading apparatus described above, the abnormal pixel detection means compares the pixel data obtained for each of the sensitivity conditions, and detects a pixel in which the pixel data match each other as an abnormal pixel. The image reading device according to claim 3 is the image reading device according to claim 1 or 2, wherein the abnormal pixel detection means sets a single image reading sensitivity with respect to the predetermined reading target area. Is characterized in that the predetermined target image is read.

An image reading apparatus according to a fourth aspect is the image reading apparatus according to the first aspect.
Alternatively, in the image reading device according to the second aspect, the abnormal pixel detection unit sets the predetermined target image under a sensitivity condition in which the predetermined read target area is set with a stepwise different image read sensitivity for each predetermined number of rows. It is characterized by reading. An image reading apparatus according to claim 5 is the image reading apparatus according to any one of claims 1 to 4, wherein the reading sensitivity setting unit changes the image reading sensitivity in at least a plurality of stages to adjust the sensitivity. It is characterized in that it is provided with a sensitivity adjusting reading means for reading a predetermined image.

An image reading apparatus according to a sixth aspect of the present invention is the image reading apparatus according to the fifth aspect.
In the image reading device described above, the sensitivity adjusting reading means sets different image reading sensitivities stepwise for each predetermined number of rows of the photosensor array, and reads the predetermined image for sensitivity adjustment. It has a feature. The image reading device according to claim 7 is the image reading device according to claim 5 or 6, wherein the sensitivity adjusting reading means is configured to perform a predetermined image for the sensitivity adjustment on the entire effective reading area of the photosensor array. It is characterized by reading.

The image reading device according to claim 8 is the image reading device according to claim 5.
Alternatively, in the image reading device according to the sixth aspect, the sensitivity adjustment reading unit reads the predetermined image for sensitivity adjustment only in a detection area preset in an effective reading area of the photosensor array. There is. The image reading device according to claim 9 is the image reading device according to any one of claims 5 to 8, wherein the sensitivity adjusting reading means performs an operation of reading the predetermined target image in the abnormal pixel detecting means. It is characterized in that the first pixel data group is obtained by performing the reading operation of a predetermined image in unison and reading the predetermined image for sensitivity adjustment a plurality of times under different sensitivity conditions.

An image reading apparatus according to a tenth aspect of the present invention is the image reading apparatus according to any one of the fifth to eighth aspects, wherein the sensitivity adjusting reading means is detected based on the first pixel data group. 12. The image reading apparatus according to claim 11, wherein the second pixel data group is obtained by eliminating the influence of abnormal pixels and reading the predetermined image for sensitivity adjustment. The image reading apparatus further includes an abnormal pixel excluding unit that uniquely removes pixel data relating to the abnormal pixel from the first pixel data group to generate the second pixel data group. Is characterized by.

An image reading apparatus according to a twelfth aspect is the image reading apparatus according to the eighth aspect, wherein the image reading apparatus is
It is characterized by further comprising abnormal pixel eliminating means for changing and setting the arrangement area of the detection area so as to avoid the abnormal pixel detected based on the first pixel data group. The image reading apparatus according to claim 13,
The image reading apparatus according to claim 1, wherein the image reading apparatus further includes an abnormal pixel eliminating unit that drives and controls a predetermined notifying unit when the abnormal pixel detecting unit detects the abnormal pixel. It is characterized by that.

An image reading device according to a fourteenth aspect is the image reading device according to any one of the first to thirteenth aspects,
The reading sensitivity setting means has the largest data range among the data ranges calculated based on the maximum value and the minimum value of the pixel data for each image reading sensitivity in the second pixel data group. It is characterized in that the sensitivity is extracted and set as the optimum image reading sensitivity in the regular image reading operation for the subject.

An image reading apparatus according to a fifteenth aspect is the image reading apparatus according to any one of the first to thirteenth aspects,
The reading sensitivity setting means has a maximum difference absolute value among the maximum difference absolute values calculated based on pixel data of adjacent pixels for each image reading sensitivity in the second pixel data group. The image reading sensitivity is extracted and set as an optimum image reading sensitivity in a regular image reading operation for the subject. The image reading device according to claim 16 is the image reading device according to any one of claims 1 to 1.
5. The image reading device described in any one of 5 above is characterized in that the pixel data is lightness data corresponding to an image pattern of the predetermined image.

An image reading apparatus according to a seventeenth aspect is the image reading apparatus according to any one of the first to sixteenth 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 18 is the image reading device according to any one of claims 5 to 17, wherein the sensitivity adjusting reading means controls the charge accumulation period in the photo sensor to read the image. The feature is that sensitivity is adjusted arbitrarily.

According to a nineteenth aspect of the present invention, there is provided a method for setting the sensitivity of an image reading apparatus, comprising a photosensor array including a plurality of photosensors, and a regular reading for reading an image of a subject placed on a detection surface on the photosensor array. In a sensitivity setting method of an image reading apparatus for executing a reading sensitivity setting operation for setting an image reading sensitivity suitable for the regular reading operation at an arbitrary timing prior to the operation, a predetermined reading target area of the photosensor array is set. A plurality of different sensitivity conditions are set, a predetermined target image is read a plurality of times for each sensitivity condition, and the first pixel data group obtained by reading the target image for each sensitivity condition is A procedure of detecting a pixel in which pixel data for each sensitivity condition match each other as an abnormal pixel, and a procedure of eliminating the influence of the detected abnormal pixel The read predetermined object image, based on the second pixel data group obtained by eliminating the influence of the abnormal pixel is characterized in that it comprises, a step of executing the reading sensitivity setting operation.

A sensitivity setting method for an image reading apparatus according to a twentieth aspect is the sensitivity setting method for an image reading apparatus according to the nineteenth aspect, wherein the procedure for reading the target image is a single step for the predetermined reading target area. It is characterized in that the predetermined target image is read under a sensitivity condition that sets one image reading sensitivity. A sensitivity setting method for an image reading apparatus according to claim 21, wherein in the sensitivity setting method for an image reading apparatus according to claim 19, the procedure for reading the target image in order to obtain the first pixel data group is the photo sensor. By setting different image reading sensitivity for each predetermined number of rows in the array,
It is characterized in that the read operation for sensitivity adjustment for reading a predetermined image for sensitivity adjustment is performed in unison.

A sensitivity setting method for an image reading apparatus according to a twenty-second aspect is the sensitivity setting method for an image reading apparatus according to the nineteenth aspect. 24. The sensitivity setting method for an image reading apparatus according to claim 23, wherein the pixel data relating to the abnormal pixel is uniquely removed to generate the second pixel data group. In the sensitivity setting method of the reading device, the procedure for eliminating the influence of the abnormal pixel is to change and set the reading target area so as to avoid the abnormal pixel detected based on the first pixel data group. Is characterized by.

That is, the image reading apparatus and the sensitivity setting method thereof 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. In the reading sensitivity setting operation that is executed at an arbitrary timing prior to, the reading target area of the predetermined target image (or the sensitivity adjustment image or the regular subject image) is read multiple times under different sensitivity conditions. Of a plurality of pixel data groups (first pixel data group) obtained by the operation, the pixel data corresponding to the change in the sensitivity condition is the pixel data that does not change and the pixel data corresponding to each sensitivity condition does not change. It is determined as an abnormal pixel that is not detected, and the pixel data related to the abnormal pixel is removed from the pixel data group or for sensitivity adjustment. Pixel data group obtained by executing an abnormal pixel remover such as to be excluded from the reading of the abnormal pixel in the preparative operation (second pixel data groups)
Based on the above, the optimum image reading sensitivity extraction and setting processing is executed.

As a result, even if the photosensor array has an element defect or dust is attached to the detection surface, the image reading sensitivity can be improved before the optimum image reading sensitivity is extracted and set. Regardless of whether or not there is an abnormal pixel whose pixel data does not change, for example, the process of excluding the pixel data of the abnormal pixel, the process of changing the setting so that the reading target area does not include the abnormal pixel, or the abnormal pixel The process of notifying the user of the image reading apparatus to remove the foreign matter that causes the noise is eliminated by the relatively simple processing operation to eliminate the influence of abnormal pixels, and the sensitivity adjustment image (subject image) Since only normal pixel data (second pixel data group) corresponding to the image pattern of is obtained, in the operation of extracting and setting the optimum image reading sensitivity,
It is possible to prevent setting of an incorrect image reading sensitivity different from the original optimum sensitivity due to the abnormal pixel.

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. 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.

Here, a sensitivity condition having a single (constant) image reading sensitivity is set for the entire reading target area of the target image (or the subject image), and the target image reading operation is executed. Presence or absence of an abnormal pixel by detecting an abnormal pixel based on the first pixel data group obtained by performing the sensitivity adjustment reading operation so as to eliminate the abnormal pixel, and obtaining the second pixel data group. And its pixel position can be detected and grasped at an early stage, and a pixel data group consisting of only normal pixel data can be obtained by performing a single sensitivity adjustment reading operation by excluding an abnormal pixel from the reading target with a simple process. Therefore, the pixel data group can be directly applied to the extraction and setting operation of the optimum reading sensitivity. As a result, the time required to set the optimum reading sensitivity can be shortened and the processing load on the controller can be reduced.

The target image (or subject image)
For the entire reading target area, for example, by setting a sensitivity condition consisting of image reading sensitivities that differ stepwise for each predetermined number of rows, the target image reading operation is executed jointly with the sensitivity adjustment reading operation. By doing so, it is possible to generate the second pixel data group by a simple process of excluding abnormal pixels detected based on the first pixel data group from the first pixel data group. It is possible to reduce the processing load on the controller by reducing the number of times the subject image is read.

[0035]

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 photosensor 10 uses the semiconductor layer 11 as a common channel region.
1, an upper MOS transistor formed of a source electrode 12, a drain electrode 13 and a top gate electrode 21, a semiconductor layer 11, a source electrode 12 and a drain electrode 13
And a lower MOS formed by the bottom gate electrode 22
A structure in which two MOS transistors each including a transistor are combined is a transparent insulating substrate 1 such as a glass substrate.
9 is formed.

The double gate type photosensor 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 3A, the double gate type photo sensor 1
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, carriers (holes) corresponding to the amount of incident light are trapped in the channel region as shown in FIG. It acts so as to cancel the negative bias of the terminal TG, and the bottom gate terminal B is canceled by this cancellation.
With the positive bias of G, the double gate type photo sensor 10 is 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 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, φtg is a pulse signal φT1, φT2, ... φTk, ...
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 of rows forming a photosensor array with one drive cycle of the drive control method of the double gate type photosensor (see FIG. 2). 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 photo sensor 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 in time, and a part of the processing cycle for each row overlaps in time. Therefore, the read operation can be performed before the reset operation in all the rows is completed, and the read required time can be significantly shortened while the read operation of the two-dimensional image is favorably performed. .

<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 double-gate type photosensors 10 arranged two-dimensionally 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 the subject image by the photo sensor array 100, pixel data matching, and processing, and the overall operation of the image reading apparatus. A function to control and execute the above-mentioned image reading operation, and a sensitivity adjusting reading operation, an abnormal pixel detecting operation, and a reading sensitivity setting operation (that is, a sensitivity setting method of the image reading apparatus according to the present invention) described later. Controller provided (reading means for sensitivity adjustment, abnormal pixel detection means, reading sensitivity setting means)
RA used as a work area for the controller 150 and the controller 150, and temporarily stores (stores) acquired pixel data, processing data related to setting of image reading sensitivity, and the like.
The M160 and the ROM 170 that holds the control program of the controller 150 and various control data are configured. Here, the photo sensor array 100, the top gate driver 110, and the bottom gate driver 12
0 and the drain driver 130 have the same configuration and function as the photo sensor system shown in FIG.
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. 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 via the amplifier 133 and the A / D converter 140 and input as an image output signal (image data). The controller 150 performs predetermined image processing on the image data, and the RAM 160
An external function unit 200 that performs writing and reading to and from the pixel data and executes predetermined processing such as matching and processing of pixel 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 output to the top gate driver 110 and the bottom gate driver 120, so as to precede the normal image reading operation or at an arbitrary timing. Performing an operation (reading operation for sensitivity adjustment) that independently reads an image for sensitivity adjustment (which may be the image of the subject that is the subject of the regular image reading operation) to determine the state of the subject, the illuminance of outside light, etc. Image reading sensitivity (optimum image reading sensitivity) capable of optimally reading the subject image in accordance with the surrounding environment of (2), that is, a function of setting the charge accumulation period Ta of the double gate photosensor 10 (reading sensitivity setting operation) , And a predetermined image (which may be a sensitivity adjustment image or a regular subject image) is read multiple times under different sensitivity conditions. By comparing pixel data (brightness data or brightness data; referred to as “brightness data” in the present application) acquired in correspondence with the image pattern of the predetermined image for each sensitivity condition. An abnormal pixel indicating abnormal pixel data caused by an element defect existing in the array or a foreign substance (dust etc.) attached to the detection surface is detected (abnormal pixel detection operation), and the influence of the pixel is removed ( (Abnormal pixel elimination operation), and a function to enable setting of the optimum image reading sensitivity.

<Controller> Next, the 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 that writes / reads data to / from the RAM 160, the ROM 170, and the external function unit 200 to manage various data, and controls these controllers 151 and 152 according to a predetermined control program. It has an interface with the external function unit 200 and the like, and has a main controller 153 for exchanging control signals.

The controller 150 is included in the image data based on the image output signal (image data) input as a digital signal from the photosensor array 100 through the A / D converter 140 for each sensitivity condition. The brightness data values of the original pixel data groups (first pixel data group; hereinafter also referred to as “original pixel data” for convenience) are compared with each other, and further, by the abnormal pixel detection / exclusion operation according to the present invention. Calculated by an adder 155, which will be described later, based on the pixel data group after the abnormal pixel data is removed or eliminated (second pixel data group; hereinafter also referred to as “processed pixel data” for convenience). Data comparator 1 for extracting the maximum value of the dynamic range (data range), or the maximum value of the representative difference value (maximum difference absolute value) of pixel data between pixels. 4, the pixel data and the processed data processed through the adder 155 that calculates the dynamic range or the absolute difference value from the processed pixel data, the A / D converter 140, the data comparator 154, and the adder 155. Is input, and these data are written to or read from the RAM 160 as necessary, re-input to the data comparator 154 or the adder 155, output to the external function unit 200 via the data controller 152, and the like. Based on the control signal from the data selector 156 for switching control and the data controller 152, the device controller 151 causes the top gate driver 1 to optimize the image reading sensitivity of the photo sensor array 100.
10, a sensitivity setting register 157 for setting and controlling the timing of each control signal φtg, φbg, φpg output to the bottom gate driver 120 and the precharge switch 132,
have.

Here, the above-mentioned main controller 15
In the present embodiment, 3 is at least based on the change (presence or absence of change) of the pixel data in the same pixel acquired by the data comparator 154 under different sensitivity conditions (whether the pixel is a normal pixel, In addition to the function of determining whether it is an abnormal pixel (abnormal pixel detection operation), for example, based on this determination result, the pixel data determined to be an abnormal pixel from the image data acquired by the sensitivity adjustment reading operation By specifying exclusion, and storing the remaining pixel data group in the RAM 160 via the data selector 156, the above-described processed pixel data from which abnormal pixel data has been removed is generated, or an informing means (not shown) is driven. The detection state of the abnormal pixel is notified to the user of the image reading apparatus to prompt appropriate measures, or the sensitivity adjustment reading operation is performed. It is also provided with the ability to adjust the placement area of the detection area in the normal image reading operation (reset) (abnormal pixel remover). The controller 150
The operation of detecting and removing the abnormal pixel by the (main controller 153) will be described in detail later.

Further, the photosensor array 100 (top gate driver 110,
A method of setting the optimum image reading sensitivity (reading sensitivity setting operation) set in the bottom gate driver 120 and the precharge switch 132) will be described later in detail, but the main controller 153, for example, in the reading operation for sensitivity adjustment, A processed pixel in which the influence of pixel data in the detected abnormal pixel is eliminated from the image data (original pixel data) input from the photo sensor array 100 by using the above-described data comparator 154 and adder 155. Control is performed so that data is generated, the reading sensitivity that is the maximum value of the dynamic range and the representative difference value is extracted from the processed pixel data, and the reading sensitivity is set in the sensitivity setting register 157.

<First Embodiment of Processing Operation> Next, a first embodiment of the 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. It will be described with reference to FIG. As described above, the controller 150 according to the present embodiment detects abnormal pixels as described below prior to the regular image reading operation on the subject or at any timing independent of the regular image reading operation. Each configuration of the image reading device (photo sensor system) is controlled so as to execute the operation and the abnormal pixel elimination operation, the sensitivity adjustment reading operation, and the reading sensitivity setting operation. Here, the series of processing procedures described below are performed by the controller 150, for example,
It is realized by loading a control program previously stored in the ROM 170 into the RAM 160 and executing it.

<Abnormal Pixel Detection Operation> FIG. 9 is a flow chart showing an example of an abnormal pixel detection operation applied to the sensitivity setting method of the image reading apparatus according to this embodiment. Note that the description will be given here with reference to the configuration of the image reading apparatus illustrated in FIGS. 7 and 8 as appropriate. In the processing operation (abnormal pixel detection operation) of the controller according to this embodiment, as shown in FIG. 9, first, the abnormal pixel detection operation is started by the main controller 153 at an arbitrary timing prior to the regular reading operation of the subject. The image reading sensitivity based on a predetermined sensitivity condition (initial value) is set in the sensitivity setting register 157 via the data controller 152, and the abnormality is placed on the detection surface provided on one surface side of the photosensor array 100. The operation of reading a predetermined target image for pixel detection (which may be an image for sensitivity adjustment described later, or an image of a subject to be read in a normal image reading operation) is performed multiple times.

Specifically, the main controller 153 sets the sensitivity condition to an initial value via the data controller 152 (S101), and based on the sensitivity condition, the entire effective reading surface of the photosensor array 100, or , A single image reading sensitivity (that is, a charge accumulation period set in each photosensor 10 constituting the photosensor array 100) is set for the entire predetermined detection area set within the effective reading surface. The sensitivity setting register 157 is controlled as described above.

Then, similarly to the above-described image reading operation (see FIG. 6), by sequentially driving the photosensor 10 for each row, the area to be read (the entire effective reading surface or the detection area). The first read operation of reading the target image is performed for the entire area (S102).
The image data of the target image obtained by such a reading operation of the target image is temporarily stored in the RAM 160 via the data selector 156, for example.

Then, after the first reading operation of the target image is completed, the main controller 153 is operated.
Is another single image reading sensitivity (charge accumulation period) based on another sensitivity condition that is different from the initial value by changing the sensitivity condition.
Is set (S103), and the second reading operation for reading the target image is executed again (S104). The image data obtained by the second reading operation of the target image is also
Similar to the above, for example, it is stored in a predetermined storage area of the RAM 160. In this way, the main controller 153
Indicates a predetermined target image reading operation related to the abnormal pixel detection operation, which is set a predetermined number of times (two or more arbitrary times).
By repeating (processing steps S101 to S10
4) Obtain a plurality of image data read for the same target image based on different sensitivity conditions. In addition,
The setting of the reading target area in the reading operation of the target image and a specific example of the reading method in the reading target area will be described in detail later.

Next, of the image data obtained by the processing steps S101 to S104 by the data controller 152, for example, pixel data (lightness data) for two times detected by each pixel (photosensor) for each sensitivity condition is used. ) From the RAM 160 to the data selector 1
The data is extracted via 56, taken into the data comparator 154 (S105), and the pixel data are compared with each other for each pixel (S106) to determine whether or not there is a change (change in lightness data value). Here, the main controller 153 determines, for example, whether or not the pixel data has changed, for example,
It is set so that a flag is set (set to "1") for each pixel.

In the comparison process by the data comparator 154, if the pixel data (brightness data values) in the same pixel under different sensitivity conditions are the same or equivalent (S107), at least the pixel (photosensor). ) Does not detect the pixel data (brightness data value) corresponding to (dependent on) the change in the sensitivity condition, the pixel is determined to be an abnormal pixel (S108). At this time, the flag set for the pixel is held as it is (“1”).

On the other hand, in the comparison process (S106), if the pixel data (brightness data value) of the same pixel under different sensitivity conditions are different (S107), at least the pixel (photosensor) changes in sensitivity condition. It is determined that the pixel data (lightness data value) corresponding to (dependent on) is normally detected, and the pixel is determined to be a normal pixel (S109). At this time, the main controller 153 controls so that the flag set for the pixel is lowered (“1” → “0”).

The quality determination processing (processing steps S105 to S109) for each pixel is repeated, for example, for all the pixels included in the image data acquired for the predetermined target image or for a specific pixel. To be executed. Regarding the process of judging whether each pixel is normal or abnormal,
A detailed example will be described later. Through the series of abnormal pixel detection operations described above, it is possible to easily detect whether or not an abnormal pixel exists in the photo sensor array 100 and the position where the abnormal pixel is generated, based on the flag setting state of each pixel. , Based on such detection results,
An abnormal pixel elimination operation, a sensitivity adjustment reading operation, and a reading sensitivity setting operation, which will be described later, are executed.

(Target Image Reading Operation) Next, a specific example of the target image reading operation (processing steps S101 to S104) executed in the above-described abnormal pixel detection operation will be specifically described with reference to the drawings. .. FIG. 10 is a conceptual diagram showing a specific example of a reading target area and a reading method in the reading target area in the reading operation of the target image according to the present embodiment, and FIG. 11 is a reading of the target image according to the present embodiment. It is a conceptual diagram which shows the read target area | region in operation | movement, and the other specific example of the reading method in this read target area | region.

Specifically, the operation of reading the target image 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). As shown in FIG. 10, the predetermined target image placed on the surface is displayed on the entire effective reading surface (effective reading area) 30 of the photosensor array 100, or as shown in FIG.
A 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 in each photo sensor 10 constituting the photo sensor array 100 is the image reading sensitivity based on the sensitivity condition in the first reading operation and the second reading operation. The image reading sensitivity based on the sensitivity condition in 1) is set to be different from each other.

A specific method of driving the photosensor 10 in the operation of reading the target image is, for example, as shown in FIG.
As shown in (a), all the rows forming the effective reading surface 30 of the photosensor array 100, which is composed of pixels of 256 rows × 196 columns (that is, 256 × 196 photosensors), are sequentially read. Good, fig 1
As shown in 0 (b), the 10th line, the 20th line, ... 1
It is also possible to sequentially read a specific row or a plurality of rows (every 10 rows in this case) such as the 80th row, the 190th row, ...

As described above, the effective reading surface 30 of the photosensor array 100 is used as the reading target area, and the reading operation of the target image is executed for all rows or a specific row, whereby the photosensor array 100 is read. Since it is possible to detect the presence or absence of abnormal pixels over almost the entire area, it is possible to provide the detection area 40 as described above,
It is possible to provide an image reading apparatus that is effective when reading images of subjects having various sizes and characteristics.

As another specific example of the method of driving the photosensor 10, the target image is displayed in the row range from the 64th row to the 191st row and from the 67th column as shown in FIG. It is also possible to sequentially read all the rows of the detection area 40 formed by the column range of the 130th column, as shown in FIG.
As shown in 1 (b), the 70th line, the 80th line, ... 1
Every plural lines like 80th line and 190th line (here,
It is also possible to sequentially read a specific row (every 10 rows) or a plurality of rows.

As described above, the detection area set in a relatively small area in the effective reading surface 30 of the photosensor array 100 is set as the reading target area, and all rows or a specific row or a plurality of rows are described above. By executing the reading operation of the target image, it is possible to reduce the number of pixels that are the targets of detection of abnormal pixels, reduce the processing time in the operation of detecting abnormal pixels, and reduce the probability of detecting abnormal pixels. The processing load in the detection operation can be reduced.

<Abnormal Pixel Exclusion Operation / Sensitivity Adjustment Reading Operation> Next, the abnormal pixel elimination operation and the sensitivity adjustment reading operation realized by the controller applied to the image reading apparatus according to the present embodiment will be described with reference to the drawings. Then, it will be specifically described. FIG. 12 is a flowchart showing an example of the abnormal pixel elimination operation and the sensitivity adjustment reading operation realized by the controller applied to the image reading apparatus according to this embodiment, and FIG. 13 is related to this embodiment. 9 is a flowchart showing another embodiment of the abnormal pixel elimination operation and the sensitivity adjustment reading operation realized by the controller applied to the image reading apparatus. Note that the description will be given here with reference to the configuration of the image reading apparatus illustrated in FIGS. 7 and 8 as appropriate.

The first specific example of the processing operation (abnormal pixel elimination operation and sensitivity adjustment reading operation) of the controller according to the present embodiment is the abnormal pixel detection in the reading target area by the series of abnormal pixel detection operations described above. After it is determined whether or not there is an abnormal pixel, whether or not there is an abnormal pixel in the target area based on the determination result (that is, a flag is set (“1”) as shown in FIG. ) State pixel) is determined (S111), and when it is determined that an abnormal pixel exists, a predetermined abnormal pixel elimination process for preventing or suppressing the influence of the abnormal pixel is executed. (S1
12).

Here, as the abnormal pixel elimination processing, for example, a user of the image reading apparatus according to the present embodiment is driven by driving a notifying means such as a warning lamp and a display device which are not shown in FIGS. 7 and 8. Or notify the administrator or the like to urge them to take appropriate measures (maintenance, etc.) such as repair or adjustment of the device, or removal of foreign matter adhering to the detection surface, or Pixel data detected by the abnormal pixel is specified to be excluded, and processing is performed so that pixel data from the abnormal pixel is not taken in (excluded) in the sensitivity adjustment reading operation and the normal image reading operation of the subject described later. In addition, a predetermined data interpolation process is performed on the pixels from which the pixel data acquisition is excluded, for example, based on the pixel data of the peripheral pixels. It may be. Further, in the sensitivity adjustment reading operation and the normal image reading operation of the subject, when a predetermined detection area is set in advance as a reading target area, the arrangement area of the detection area is set to an area not including the abnormal pixel. It may be set again so as to be changed. An example of the abnormal pixel excluding process will be described in detail in a specific example described later.

Then, in the normal image reading operation of the object, the object is provided with good contrast in the photo sensor array set to exclude the pixel data from the abnormal pixel by the above-mentioned abnormal pixel exclusion processing. A sensitivity adjustment reading operation for setting an optimum image reading sensitivity with which an image can be read is executed. That is, the control signals output from the device controller 151 to the top gate driver 110, the bottom gate driver 120, and the precharge switch 132 cause the image reading sensitivity (charge accumulation) for each photosensor 10 included in the photosensor array 100. The period is set to be different stepwise (S113).

Specifically, for example, it may be set so as to be sequentially different stepwise for each photosensor group (that is, for each row) that is simultaneously driven in the image reading operation, or a predetermined value may be set. It may be set so as to be sequentially different for each of a plurality of rows, or different for each entire area of the read image (that is, for each screen) like the entire effective reading surface 30 and the entire detection area 40. It may be set as follows.

Then, based on the image reading sensitivity, the image reading operation of the photosensor array described above (see FIG. 5,
Similar to (see FIG. 6), an image for sensitivity adjustment (which may be an image of a subject to be read in a normal image reading operation) placed on the detection surface is displayed as shown in FIG.
For all rows or a specific row of the effective reading surface 30 of the photosensor array 100, or as shown in FIG. 11, all rows of the detection area set in a predetermined arrangement area in the effective reading surface 30 or A sensitivity adjustment reading operation for sequentially reading a specific row is executed (S114). Next, in the sensitivity adjustment reading operation, the optimum sensitivity extraction and setting operation is executed based on the pixel data group (corresponding to the processed pixel data) acquired in the state where the pixel data from the abnormal pixel is excluded. (S115).

In the second specific example of the processing operation (abnormal pixel elimination operation and sensitivity adjustment reading operation) of the controller according to the present embodiment, a series of abnormal pixel detection operations as described above are performed to the read target area. After determining whether or not there is an abnormal pixel, as shown in FIG. 13, a sensitivity adjustment reading operation for setting the optimum image reading sensitivity is executed. That is, the image reading sensitivity (charge accumulation period) is set to be different stepwise for each photo sensor 10 constituting the photo sensor array 100 (S121), and the image reading sensitivity (charge accumulation period) is set on the detection surface based on the image reading sensitivity. An image for sensitivity adjustment is placed on all rows or a specific row of the effective reading surface 30 of the photosensor array 100, or all of the detection areas set in a predetermined arrangement area on the effective reading surface 30. A sensitivity adjustment reading operation for sequentially reading rows or a specific row is executed (S122).

Then, based on the above-described result of the determination regarding the abnormal pixel, whether or not the abnormal pixel exists in the target area (that is, whether there is a pixel in a flag ("1") state). Whether or not) is determined (S123), and when it is determined that an abnormal pixel exists, a predetermined abnormal pixel elimination process for preventing or suppressing the influence of the abnormal pixel is executed (S124).

Here, as the abnormal pixel elimination processing, similar to the above-described first specific example, the notification means such as a warning lamp and a display device is driven to notify the user or manager of the image reading device. Alternatively, the pixel data detected by the abnormal pixel may be excluded and designated, and the pixel data resulting from the abnormal pixel may be extracted from the pixel data group acquired in the sensitivity adjustment reading operation described above. It may be processed so as to be removed, or further, predetermined data interpolation processing may be executed for the pixel from which the pixel data is removed. In addition, in the case of presetting a predetermined detection area as the reading target area in the regular image reading operation of the subject, the arrangement area of the detection area is set again so as to be changed to an area not including the abnormal pixel. It may be one that does. Then, by the abnormal pixel elimination processing, a pixel data group (processed pixel data) generated by removing pixel data due to an abnormal pixel from the pixel data group (original pixel data) acquired in the sensitivity adjustment reading operation. Based on the above, the operation of extracting and setting the optimum sensitivity is executed (S125).

According to the series of processing operations described above, the reading operation of the target image for detecting the abnormal pixel is performed.
By executing it prior to the sensitivity adjustment reading operation, the presence or absence of an abnormal pixel and its pixel position can be detected and grasped at an early stage, so pixel data detected by the abnormal pixel in the sensitivity adjustment reading operation is eliminated. By doing so, a pixel data group consisting of only normal pixel data can be easily obtained and applied to the extraction and setting operation of the optimum reading sensitivity as it is, and the time required to set the optimum reading sensitivity is shortened. In addition, the processing load on the controller can be reduced.

Here, in the above-mentioned sensitivity adjusting reading operation, the following image reading sensitivity setting operation can be applied satisfactorily. FIG. 14 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. 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 reading method of the photosensor 10 shown in FIGS. 10 and 11, as a method of setting different image reading sensitivities stepwise for all rows or a specific row of the photosensor array or the detection area, 14
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 adjusting reading operation, each row to be read by 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).

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 the above-mentioned specific example, and the image for sensitivity adjustment or If the object image can be read at different reading sensitivities and the image data can be acquired, for example, one screen of the image for sensitivity adjustment is read by a single reading sensitivity, and then the reading sensitivity is changed to adjust the sensitivity. Needless to say, the operation of re-reading one screen image may be repeated a plurality of times to acquire image data with different reading sensitivities, or another method may be used. .

(Execution Timing of Abnormal Pixel Detection Operation and Sensitivity Adjustment Reading Operation) Therefore, for the abnormal pixel detection operation and the sensitivity adjustment reading operation according to the present embodiment, the execution timings shown below should be applied appropriately. You can
FIG. 15 is a conceptual diagram showing an example of control of execution timing applicable to the abnormal pixel detection operation and the sensitivity adjustment reading operation according to the present embodiment. Here, at least as a target image reading operation for abnormal pixel detection performed prior to the sensitivity adjustment reading operation, an image is displayed only for a specific row in the detection area set in the effective reading surface of the photosensor array. A case of reading data (see FIG. 11B) will be described, but the present invention is not limited to this, and is executed for all rows of the effective reading surface or a specific row or all rows of the detection area. It goes without saying that it may be one. Further, the sensitivity adjusting reading operation may be similarly controlled.

As for the execution timing of the abnormal pixel detection operation and the sensitivity adjustment reading operation described above, for example, as shown in FIG. 15, first, in the image reading operation shown in FIG.
Charge accumulation period (reading sensitivity) based on the initial sensitivity condition
TP1 is set, and as shown in FIG. 11B, a reset pulse φTn is sequentially applied and initialized only for a specific row belonging to the detection area 40, and the charge accumulation period T
After the elapse of P1, the read pulse φBn is applied to perform the first target image reading operation of reading the drain voltage corresponding to the image pattern of the target image, and then the charge accumulation based on another sensitivity condition different from the initial state. The second target image reading in which the period (reading sensitivity) TP2 is set and the drain voltage corresponding to the image pattern of the target image is read out only for a specific row belonging to the detection area 40 as in the first target image reading operation. Take action.

Next, based on the image data obtained by the first and second target image reading operations, as shown in FIG. 9, after determining the presence or absence of abnormality in each pixel, the pixel belongs to at least the detection area 40. For each row, as shown in FIG. 14, the charge accumulation period Tn is sequentially changed and set for each row, and a sensitivity adjustment reading operation for reading the drain voltage corresponding to the image pattern of the sensitivity adjustment image is performed. .

As a result, the presence or absence of abnormal pixels in the photosensor array is detected prior to the sensitivity adjustment reading operation.
For example, since the pixel data of the abnormal pixel can be excluded or the foreign matter that causes the abnormal pixel can be removed, the influence of the abnormal pixel on the image data acquired by the sensitivity adjustment reading operation can be suppressed or prevented. Therefore, it is possible to prevent an erroneous image reading sensitivity different from the original optimum sensitivity from being set in the extraction and setting operation of the optimum image reading sensitivity described later.

(Specific Example of Application to Fingerprint Reading Device) Next, a specific example of applying the above-described image reading device according to the present invention to a fingerprint reading device will be described with reference to the drawings. The abnormal pixel detection operation, the abnormal pixel elimination operation, and the sensitivity adjustment reading operation (FIGS. 9, 12, 13, and 15) shown in the above-described embodiment will be described with reference to the description. The operation of extracting and setting the optimum reading sensitivity (processing steps S115 and S125) will also be described.

FIG. 16 is a schematic view showing the placement state of the subject (finger) and the arrangement area of the detection area when the image reading apparatus according to this embodiment is applied to the fingerprint reading apparatus.
FIG. 7 is a schematic diagram showing a fingerprint image obtained when the target image reading operation is executed by using the photosensor array in which the abnormal pixel which becomes the bright spot defect exists in the image reading apparatus according to the present embodiment. . 18 is a diagram showing an example of the abnormal pixel eliminating operation according to the present embodiment, and FIG.
FIG. 9 is a diagram showing another example of the abnormal pixel excluding operation according to the present embodiment.

First, as shown in FIG. 16, an image pattern (fingerprint) of a finger FG, which is a subject in a normal image reading operation, is used as a target image for abnormal pixel detection, and at least 256 rows × 196 columns of pixels are used. A preset line range of the 64th line to the 191st line (128) in the effective reading surface 30 of the photosensor array 100 including (photosensors).
(Row) and the column range of 67th to 130th columns (64 columns) as the detection area 40.
As described above, a single charge accumulation period (first reading sensitivity) TP1 based on the sensitivity condition in the initial state is set for the photosensor group of a specific row belonging to the above, and the image pattern of the finger FG is read. The first target image reading operation is executed.

As a result, as shown in FIG.
It is read with the image reading sensitivity specified by the very short single charge accumulation period TP1, and the overall brightness is low (dark).
Obtain a fingerprint image with a dark image pattern. Here, in the photo sensor array 100 shown in FIG. 16, there are abnormal pixels due to element defects (not shown), adhesion of foreign matter, etc.
As shown in FIG. 17A, it is assumed that a bright spot defect ILA showing an abnormally high lightness data value has occurred in the fingerprint image (row position Lp, column position Rp) in the detection area 40.

Then, as in the first target image reading operation, a single charge accumulation period based on another sensitivity condition different from the initial state is set in the photosensor group of a specific row belonging to the detection area 40. TP2 (for example, charge accumulation period TP
(Charge accumulation period longer than 1) is set, and the second target image reading operation for reading the image pattern of the finger FG is executed. As a result, as shown in FIG. 17B, the image is read with the image reading sensitivity defined by the single charge accumulation period TP2 that is longer and relatively shorter than the charge accumulation period TP1, and the overall brightness is relatively high. A fingerprint image with a high (bright) image pattern is obtained. Even in this case, FIG.
As shown in (b), a relatively high lightness data value is detected at the pixel position (row position Lp, column position Rp) where the bright spot defect ILA has occurred.

Regarding pixel data obtained from such a fingerprint image (FIG. 17), as shown in FIG. 18, a light state (observed as white) and a dark state (observed as black) of the brightness data value. For example, when the gradation data is set to 256 gradations and the change in the brightness data value in each pixel of an arbitrary row (for example, the row Lp in which the bright spot defect ILA is generated) is shown in FIG. ), As shown in FIG.
Different image read sensitivities (charge accumulation period TP
Even when the same target image was read in 1) and TP2), pixel data having an unusually high lightness data value and substantially the same numerical value was observed.

Therefore, in the operation of detecting an abnormal pixel applied to the present invention, as described above, a pixel showing a constant lightness data value (no change in the lightness data value) is unique regardless of the image reading sensitivity. The processing principle of determining abnormal pixels is adopted. Then, in the abnormal pixel eliminating operation applied to the present invention, as shown in FIG. 18A, the abnormal pixel (brightness) (Point defect ILA)
When it is determined that there is an abnormal pixel in the photo sensor array 100, the presence or absence of
As shown in FIG. 8B, the pixel data (brightness data value) at the pixel position (row position Lp, column position Rp) where the brightness data value does not change is uniquely removed or excluded.

As a result, by the processing operation of executing the predetermined exclusion operation only on the abnormal pixels detected by the abnormal pixel detection operation, the abnormal pixel of the pixel data group acquired in the sensitivity adjustment reading operation is detected. Since only normal pixel data can be simply and accurately excluded and other normal pixel data can be directly applied to the extraction and setting operation of the optimum reading sensitivity, a series of processing related to abnormal pixel detection operation and optimum sensitivity setting operation It is possible to reduce the burden and the product cost.

As another example of the abnormal pixel eliminating operation applied to the present invention, as shown in FIG.
The presence / absence of an abnormal pixel and its pixel position (row position Lp, column position Rp) are detected from the presence / absence of a change in the lightness data value for each pixel read with different image reading sensitivities, and, for example, FIG.
As shown in FIG. 4, the arrangement area of the detection area 40 that is set in advance in the target image reading operation is moved (avoided) in at least one of the row direction and the column direction like the detection area 40A to avoid the abnormal pixel. Pixel position (row position L
p, column position Rp) is reset so that it is not included.

As a result, it is possible to set at least a detection area consisting of normal pixels that do not include the abnormal pixels detected by the above-described abnormal pixel detection operation.
The pixel data group acquired in the sensitivity adjustment reading operation and the regular image reading operation can be directly applied to the extraction and setting operation of the optimum reading sensitivity and a predetermined image processing operation such as fingerprint matching, and a series of optimum sensitivity settings. It is possible to provide a highly reliable image reading apparatus in which the erroneous setting of the image reading sensitivity is improved while significantly reducing the processing load related to the operation and the regular image reading operation. Therefore, by the above-described abnormal pixel detection / exclusion operation, the pixel data group in which the pixel data due to the abnormal pixel is removed or eliminated in the sensitivity adjustment reading operation (that is, corresponding to the processed pixel data) is obtained. The optimum reading sensitivity extraction and setting operation is executed based on such a pixel data group.

(Application Example of Reading Sensitivity Setting Operation) Here, as the operation of extracting and setting the optimum reading sensitivity (reading sensitivity setting operation) applied to this embodiment, for example, the applicant of the present application has already filed and published. It is possible to satisfactorily apply the following method described in the published publication. Needless to say, the method of extracting and setting the optimum reading sensitivity described below is merely an example applicable to the present invention and does not limit the present invention.

(1) Japanese Patent Laid-Open Publication No. 3116950 The image reading sensitivity adjusting method described in this publication constitutes the photosensor array shown in the same as the above-mentioned reading operation for sensitivity adjustment (see FIG. 14). A different image reading sensitivity (charge accumulation period) is set for each row, the image for sensitivity adjustment (or the subject image that is the target of the regular image reading operation) is read, and for each row (for each image reading sensitivity),
The dynamic range (data range) defined by the difference between the maximum value and the minimum value of the pixel data (brightness data) detected by each pixel (photo sensor) is calculated, and the row having the maximum dynamic range is extracted. Then, a series of processing procedures for setting the image reading sensitivity (charge accumulation period) set in the row as the optimum sensitivity in the regular image reading operation is included. According to this, based on the pixel data group in which the pixel data due to the abnormal pixel is removed by the above-described abnormal pixel detection / exclusion operation, the optimum image reading sensitivity corresponding to the state of the subject is calculated by a simple comparison process or arithmetic process. Can be set more accurately and uniquely.

(2) Patent Publication No. 2001-14502
No. 3, the image reading sensitivity adjustment method described in (3) above sets a different image reading sensitivity for each row, as in the processing procedure shown in (1) above, and sets the image for sensitivity adjustment (or
The subject image) is read, the maximum absolute value (representative difference value) of the difference between pixel data (brightness data) of adjacent pixels is calculated for each row, and the row having the maximum representative difference value is extracted. It has a series of processing procedures for setting the image reading sensitivity (charge accumulation period) set for each row as the optimum sensitivity in the regular image reading operation.

According to this, similarly to the method described in (1) above, it is possible to suppress or prevent the influence of the abnormal pixel in the extraction and setting operation of the optimum sensitivity, and the pixel of the adjacent pixel in the specific row. Since the optimum reading sensitivity can be extracted and set based only on the absolute value of the data difference, the processing load can be reduced by extracting the optimum sensitivity and reducing the amount of data to be processed in the setting operation. Furthermore, even when the subject is placed with a deviation from the normal placement position (for example, the detection area), it is possible to set an appropriate image reading sensitivity corresponding to the image pattern of the subject.

In the reading sensitivity setting method according to the present embodiment, the lightness data value is caused by element defects and element characteristic variations of the photosensors constituting the photosensor array, or foreign matter adhering to the detection surface. Is high, and the abnormal pixel detection and elimination operation in the case where abnormal pixels that are bright spot defects that exhibit a constant value regardless of the image reading sensitivity have occurred have been described, but the present invention is not limited to this. Instead, it may be an abnormal pixel having a low lightness data value and a constant value regardless of the image reading sensitivity, which is a defect defect. In short, one or a plurality of pixels that do not show the lightness data value corresponding (dependent) to the change in the image reading sensitivity,
Any pixel that is uniquely determined to be an abnormal pixel and is removed or eliminated may be used.

<Second Embodiment of Processing Operation> Next, a second embodiment of the 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. It will be described with reference to FIG. Here, the processing procedure and the like equivalent to those of the first embodiment of the processing operation described above will be described by simplifying the description. <Abnormal Pixel Detection Operation / Sensitivity Adjustment Reading Operation> FIG.
FIG. 21 is a flowchart showing an example of an abnormal pixel detection operation and a sensitivity adjustment reading operation applied to the sensitivity setting method of the image reading apparatus according to the present embodiment, and FIG. 21 is a sensitivity adjustment reading operation according to the present embodiment. 5 is a conceptual diagram showing an example of control of execution timing of FIG. Here, description will be given with reference to the configuration of the image reading apparatus shown in FIGS. 7 and 8 as appropriate.

The processing operation (abnormal pixel detection operation and sensitivity adjustment reading operation) of the controller according to this embodiment is shown in FIG.
As shown in 0, first, the main controller 153 is set at an arbitrary timing prior to the regular reading operation of the subject.
The sensitivity adjustment reading operation is started by the above, and the image reading sensitivity based on a predetermined sensitivity condition (initial value) is set in the sensitivity setting register 157 via the data controller 152 and is provided on the one surface side of the photo sensor array 100. The operation for reading the sensitivity adjustment image (which may be the image of the subject to be read in the regular image reading operation) placed on the detection surface is performed a plurality of times.

Specifically, the sensitivity condition is set to an initial value by the main controller 153 (S201), and based on the sensitivity condition, for example, the effective reading surface of the photosensor array 100 or the effective reading surface is previously set. For each set predetermined detection area (see FIGS. 10 and 11), for each row,
Alternatively, different image reading sensitivities (first reading sensitivities) are set step by step for each predetermined plurality of lines,
The sensitivity setting register 157 is controlled (S202).

Then, similarly to the above-mentioned image reading operation (see FIG. 6), by sequentially driving the photosensors 10 for each row, as shown in FIG. 21, the effective reading surface or the detection area of the photosensor array 100 is detected. With respect to the sequentially set different image reading sensitivities (charge accumulation period TA
In n), the first sensitivity adjustment reading operation for reading a single sensitivity adjustment image is executed (S203). The image data of the sensitivity adjustment image obtained by such a sensitivity adjustment reading operation is once read through the data selector 156, for example.
It is stored in the AM 160.

Then, for the second sensitivity adjustment reading operation, the sensitivity condition is changed by the main controller 153 (S204) as in the above-described processing procedure, and the above-mentioned effective operation is performed based on the changed sensitivity condition. For the reading surface or the detection area, different image reading sensitivities (second reading sensitivities) are set step by step for each row or for each predetermined plurality of rows (S205), and as shown in FIG. The second sensitivity adjustment reading operation for reading the single sensitivity adjustment image is executed again at the image reading sensitivity (charge accumulation period TBn) (S206). Here, the second reading sensitivity is set so as to have a charge accumulation period different from that of the first reading sensitivity (TAn ≠ TBn and TBn>
TAn). The image data obtained by the second read operation for sensitivity adjustment is, for example, R
It is stored in a predetermined storage area of the AM 160. In this manner, the main controller 153 repeats the sensitivity adjusting reading operation a predetermined number of times (an arbitrary plurality of times of two or more) (processing steps S201 to S2).
06), for the same sensitivity adjustment image, a plurality of image data read based on different sensitivity conditions are acquired.

Here, the read image acquired by the above-described sensitivity adjusting read operation will be described with reference to a specific example. 22 is a schematic diagram showing a read image (fingerprint image) when the image reading device according to the present embodiment is applied to a fingerprint reading device and the series of the above-described read operation for sensitivity adjustment is executed. 22A is a fingerprint image read by the first sensitivity adjustment reading operation (charge accumulation period TAn), and FIG. 22B is a second sensitivity adjustment reading operation (charge accumulation period TBn). It is the fingerprint image obtained. In FIG. 22, the photo sensor array 1
Detection area 40 set within the effective reading surface 30 of 00
It is assumed that an abnormal pixel indicating a defect dot ILB exists at (row position Lq, column position Rq).

As shown in FIGS. 22 (a) and 22 (b), when the image of the subject is read by sequentially changing the reading sensitivity (charge accumulation period) for each row, depending on the length of the charge accumulation period, It is possible to obtain a read image that sequentially changes from a dark state to a bright and faint state in the line number direction (1st line → 256th line direction). Further, in the first sensitivity adjustment reading operation in which the charge accumulation period is set to be relatively short, as shown in FIG. 22A, a fingerprint image with a low image brightness (dark) and a dark image pattern is obtained as a whole. In the second sensitivity adjustment reading operation in which the charge accumulation period is set to be relatively long,
As shown in (b), a fingerprint image having a high brightness (brightness) and a thin image pattern is obtained as a whole.

Next, the main controller 153 starts the abnormal pixel detection operation, and the data controller 15
2, the sensitivity adjustment reading operation (processing step S2
01-S206), for example, pixel data for two times detected by each pixel (photosensor) for each sensitivity condition (that is, for each row or for each predetermined plurality of rows) ( Lightness data) is taken into the data comparator 154 (S207), pixel data for each pixel are compared (S208), and it is determined whether or not there is a change (change in lightness data value).

Then, in the comparison processing by the data comparator 154, as in the case shown in FIG. 18, the pixel data (brightness data values) under the different sensitivity conditions (image reading sensitivity) in the same pixel are the same or equivalent. If it is (S209), the pixel is determined to be an abnormal pixel (S21).
0), if the pixel data are different from each other (S20
9), determine that the pixel is a normal pixel (S211).
Here, as a method of determining whether or not there is a change in the pixel data, the main controller 153 holds flags set in advance for all pixels in accordance with the result of the comparison process, as in the first embodiment described above. Alternatively, it may be set so as to be changed, so that the presence or absence of an abnormal pixel may be determined based on the setting state of the flag in a processing step described later.

The quality determination processing (processing steps S207 to S211) for each pixel is repeatedly executed for all pixels or specific pixels included in the image data acquired for the predetermined target image, for example. It
That is, in the present embodiment, the reading operation of the target image, which is executed in the abnormal pixel detection operation shown in the first embodiment of the above-described processing operation, is performed in unison with the sensitivity adjustment reading operation. Controlled.

Therefore, the abnormal pixel removing operation and the read sensitivity setting operation executed subsequently to the above-described abnormal pixel detecting operation and sensitivity adjusting reading operation are, for example, as shown in FIG. It is determined based on the state of the flag set for each pixel whether or not there is an abnormal pixel in the image data (pixel data group) acquired in step S22 (S22).
1) If it is determined that an abnormal pixel exists, a predetermined abnormal pixel elimination process for preventing or suppressing the influence of the abnormal pixel is executed (S222), and then the optimum sensitivity extraction and setting operation is executed. On the other hand, if it is determined that the abnormal pixel does not exist (S223), the optimum sensitivity extraction and setting operation is executed using the pixel data group read from the RAM 160 as it is (S223).

Here, as the abnormal pixel elimination processing, similar to the above-described first embodiment, the notification means such as the warning lamp and the display device is driven to notify the user or manager of the image reading device. Alternatively, the pixel data detected by the abnormal pixel may be specified to be excluded, and the pixel data may be removed and used for the optimum sensitivity extraction and setting operation, as in the process shown in FIG. Alternatively, the detection area arrangement area may be reset to an area that does not include the abnormal pixel, and the pixel data group in the area may be read to extract and set the optimum sensitivity. May be used for. Also in this embodiment, the method of extracting and setting the optimum reading sensitivity as shown in the above-described first embodiment can be favorably applied.

According to the series of processing operations described above, the reading operation of the target image for detecting the abnormal pixel can be executed collectively with the sensitivity adjusting reading operation, and the reading operation can be performed. Since it can be realized by simple processing control that only changes the charge accumulation period, abnormal pixels can be accurately detected by a simple processing operation, and the number of times the subject image is read until the optimum reading sensitivity is set. Can be reduced to reduce the processing load on the controller.

[0129]

As described above, according to the image reading apparatus and the sensitivity adjusting method for the same according to the present invention, in the photo sensor system having the photo sensor array configured by arranging a plurality of photo sensors, During the reading sensitivity setting operation that is executed at an arbitrary timing prior to the regular image reading operation, the reading target area of the predetermined target image (or the sensitivity adjustment image or the regular subject image) is changed to
Reading a plurality of times under different sensitivity conditions, determining a pixel in which pixel data for each sensitivity condition does not change as an abnormal pixel, and removing pixel data related to the abnormal pixel, or
By performing an abnormal pixel elimination operation such as excluding the abnormal pixel from the reading target, even if an abnormal pixel is caused in the photo sensor array due to an element defect or adhesion of inspection dust, comparison is performed. Since the abnormal pixel can be detected by a relatively simple processing operation and the influence thereof can be eliminated, it is possible to easily obtain a pixel data group consisting of only normal pixel data in the sensitivity adjustment reading operation, which is the optimum The image reading sensitivity can be extracted and set. 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 malfunction in the fingerprint matching process and improve the matching accuracy. Therefore, it is possible to realize a highly reliable image reading apparatus.

[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 an abnormal pixel detection operation applied to the sensitivity setting method of the image reading apparatus according to the first embodiment.

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

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

FIG. 12 is a flowchart illustrating an example of an abnormal pixel elimination operation and a sensitivity adjustment reading operation applied to the sensitivity setting method of the image reading apparatus according to the first embodiment.

FIG. 13 is a flowchart illustrating another example of the abnormal pixel elimination operation and the sensitivity adjustment reading operation applied to the sensitivity setting method of the image reading apparatus according to the first embodiment.

FIG. 14 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 first embodiment.

FIG. 15 is a conceptual diagram showing an example of control of execution timing applicable to the abnormal pixel detection operation and the sensitivity adjustment reading operation according to the first embodiment.

FIG. 16 is a schematic diagram illustrating a placement state of a subject (finger) and an arrangement region of a detection area when the image reading device according to the first embodiment is applied to a fingerprint reading device.

FIG. 17 is a schematic diagram showing a fingerprint image obtained when a target image reading operation is executed in the image reading apparatus according to the first embodiment.

FIG. 18 is a diagram showing an example of an abnormal pixel eliminating operation applied to the sensitivity setting method of the image reading apparatus according to the first embodiment.

FIG. 19 is a diagram showing another example of the abnormal pixel eliminating operation applied to the sensitivity setting method of the image reading apparatus according to the first embodiment.

FIG. 20 is a flowchart illustrating an example of an abnormal pixel detection operation and a sensitivity adjustment reading operation applied to the sensitivity setting method of the image reading apparatus according to the second embodiment.

FIG. 21 is a conceptual diagram showing a control example of execution timing of a sensitivity adjustment reading operation according to the second embodiment.

FIG. 22 is a schematic diagram showing a read image (fingerprint image) when the image reading device according to the second embodiment is applied to a fingerprint reading device and a series of reading operations for sensitivity adjustment are executed.

FIG. 23 is a flowchart illustrating an example of an abnormal pixel eliminating operation and a reading sensitivity setting operation applied to the sensitivity setting method of the image reading apparatus according to the second embodiment.

[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

Claims (23)

[Claims] 1. An image reading device comprising a photosensor array including a plurality of photosensors, the image reading device reading an image of a subject placed on a detection surface of the photosensor array, wherein a predetermined reading target area of the photosensor array is provided. A plurality of different sensitivity conditions with respect to each other, and the pixel data for each sensitivity condition in a specific pixel belonging to the first pixel data group obtained by reading a predetermined target image for each sensitivity condition are compared with each other. An abnormal pixel detecting unit for detecting an abnormal pixel based on the second pixel data group obtained by reading the predetermined target image and eliminating the influence of the abnormal pixel. An image reading apparatus comprising: a reading sensitivity setting unit that sets an image reading sensitivity suitable for a regular reading operation. 2. The abnormal pixel detecting means compares pixel data obtained for each of the sensitivity conditions, and detects a pixel in which the pixel data match each other as an abnormal pixel. Image reading device. 3. The abnormal pixel detection means reads the predetermined target image under a sensitivity condition for setting a single image reading sensitivity with respect to the predetermined read target area. 2. The image reading device described in 2. 4. The abnormal pixel detection means may read the predetermined target image under a sensitivity condition in which image read sensitivities that differ stepwise for a predetermined number of rows are set in the predetermined read target area. The image reading apparatus according to claim 1 or 2, characterized in that 5. The reading sensitivity setting means is at least
The image reading apparatus according to claim 1, further comprising a sensitivity adjustment reading unit that changes the image reading sensitivity in a plurality of steps to read a predetermined image for sensitivity adjustment. 6. The sensitivity adjusting reading means sets different image reading sensitivities stepwise for each predetermined number of rows of the photosensor array, and reads the predetermined image for sensitivity adjustment. The image reading device according to claim 5. 7. The image reading apparatus according to claim 5, wherein the sensitivity adjustment reading unit reads the predetermined image for sensitivity adjustment over the entire effective reading area of the photosensor array. . 8. The sensitivity adjusting reading means reads the predetermined image for sensitivity adjustment only in a detection area preset in an effective reading area of the photosensor array. Or the image reading device described in item 6. 9. The sensitivity adjusting reading unit executes the operation of reading the predetermined target image in unison with the reading operation of the predetermined image in the abnormal pixel detecting unit to obtain a predetermined sensitivity adjustment reading. 9. The image reading apparatus according to claim 5, wherein the first pixel data group is obtained by reading an image a plurality of times under different sensitivity conditions. 10. The reading means for sensitivity adjustment is the first
6. The second pixel data group is obtained by eliminating the influence of the abnormal pixel detected based on the pixel data group of 1. and reading the predetermined image for sensitivity adjustment. 8. The image reading device according to any one of 8. 11. The image reading device includes an abnormal pixel excluding unit that uniquely removes pixel data relating to the abnormal pixel from the first pixel data group to generate the second pixel data group, The image reading apparatus according to claim 1, further comprising: 12. The image reading device further includes abnormal pixel eliminating means for changing and setting the arrangement area of the detection area so as to avoid the abnormal pixel detected based on the first pixel data group. The image reading apparatus according to claim 8, further comprising: 13. The image reading apparatus further comprises abnormal pixel eliminating means for driving and controlling a predetermined notifying means when the abnormal pixel is detected by the abnormal pixel detecting means. The image reading apparatus according to claim 1. 14. The read sensitivity setting means has a maximum data range out of a data range calculated based on a maximum value and a minimum value of pixel data for each image reading sensitivity in the second pixel data group. 14. The image reading apparatus according to claim 1, wherein the image reading sensitivity having the above is extracted and set as an optimum image reading sensitivity in a regular image reading operation for the subject. 15. The reading sensitivity setting means is the maximum of the maximum values of the absolute difference values calculated based on the pixel data of the adjacent pixels for each of the image reading sensitivities in the second pixel data group. 14. The image reading apparatus according to claim 1, wherein the image reading sensitivity having a difference absolute value is extracted and set as an optimum image reading sensitivity in a regular image reading operation for the subject. . 16. The image reading device according to claim 1, wherein the pixel data is lightness data corresponding to an image pattern of the predetermined image. 17. 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. 17. A structure in which 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. 18. The sensitivity adjusting reading means controls a charge accumulation period in the photosensor,
The image reading apparatus according to claim 5, wherein the image reading sensitivity is arbitrarily adjusted. 19. A regular reading operation comprising a photo sensor array comprising a plurality of photo sensors, the regular reading operation being performed at an arbitrary timing prior to a regular reading operation for reading an image of a subject placed on a detection surface of the photo sensor array. In a sensitivity setting method of an image reading apparatus that executes a reading sensitivity setting operation for setting an image reading sensitivity suitable for an operation, a plurality of different sensitivity conditions are set for a predetermined reading target area of the photosensor array, and the sensitivity is set. A procedure of reading a predetermined target image for each condition a plurality of times, and a pixel in which the pixel data for each sensitivity condition in the first pixel data group obtained by reading the target image for each sensitivity condition are matched Detecting the abnormal pixels, removing the influence of the detected abnormal pixels, reading the predetermined target image, Based on the second pixel data group obtained by eliminating the influence of the unit, the sensitivity setting method of the image reading apparatus characterized by comprising, a step of executing the reading sensitivity setting operation. 20. The procedure of reading the target image is to read the predetermined target image under a sensitivity condition for setting a single image reading sensitivity with respect to the predetermined read target area. A method for setting the sensitivity of the image reading apparatus described. 21. A procedure for reading the target image in order to obtain the first pixel data group is such that stepwise different image reading sensitivities are set for each predetermined number of rows of the photosensor array for sensitivity adjustment. 20. The sensitivity setting method for an image reading apparatus according to claim 19, wherein the sensitivity setting reading operation for reading the predetermined image is performed in unison. 22. The procedure for eliminating the influence of the abnormal pixel is to uniquely remove pixel data relating to the abnormal pixel from the first pixel data group to generate the second pixel data group. 20. The sensitivity setting method for an image reading apparatus according to claim 19. 23. The procedure of eliminating the influence of the abnormal pixel is to change and set the reading target area so as to avoid the abnormal pixel detected based on the first pixel data group. 20. The sensitivity setting method for an image reading apparatus according to claim 19.