KR100526297B1 - Photosensor system and drive control method thereof - Google Patents

Abstract

The optical sensor system performs a sensitivity-adjusted reading operation on the subject image, changing the image reading sensitivity step by step for each row of the photosensor array or for a particular row. The dynamic range of the luminance data in the read subject image is checked to see how the luminance in the subject image is distributed in relation to the image reading sensitivities. Based on this distribution, the image reading sensitivity which is helpful for the optimum image reading state is extracted as the optimum image reading sensitivity.

Description

Photo sensor system and drive control method

The present invention relates to an optical sensor system having an optical sensor arrangement constituted by a plurality of optical sensors arranged in two dimensions, and a driving control method thereof.

Imaging devices such as electronic still cameras, video cameras, etc. have become very widely used. Such an imaging apparatus adopts a solid state imaging apparatus such as a charge coupled device (CCD), which serves as a photoelectric conversion politics for converting an image of a photographed subject into an image signal. As is well known, a CCD has a structure in which light sensors (light receiving members) such as photodiodes or thin film transistors (TFTs) are arranged in a matrix, and correspond to the amount of light entering through the light receiving portions of each sensor. The generated pair of electric charges (charge amount) is detected by a horizontal scan circuit and a vertical scan circuit for detecting the luminance of the light to be irradiated.

In an optical sensor system using such a CCD, it is necessary to provide each of the selected optical transistors in the scanned optical sensor in order to make the scanned optical sensor selected. In place of the combination of the optical sensor and the selective transistor, an optical sensor (hereinafter referred to as a double-gate photo sensor) has begun to develop, which is formed of a thin film transistor called a double-gate structure, and has a photo sensor function and a selectivity function. Have both.

11A is a cross-sectional view showing the structure of the double-gate optical sensor 10. 11B is a circuit block diagram showing an equivalent circuit of the double-gate optical sensor 10.

The double-gate optical sensor 10 includes a source electrode 12 formed on each of the semiconductor thin film 11, n + silicon layers 17 and 18, and n + silicon layers 17 and 18 formed by amorphous silicon or the like. A top gate electrode 21 formed on the semiconductor thin film 11 through the drain electrode 13, the block insulating film 14, and the top gate insulating film 15, and a protective insulating film provided on the top gate electrode 21. 20 and a bottom gate electrode 22 provided below the semiconductor thin film 11 through the lower gate insulating film 16. The double-gate optical sensor 10 is provided on a transparent insulating substrate 19 made of glass or the like.

In other words, the double-gate photosensor 10 is composed of a semiconductor thin film 11, a source electrode 12, a drain electrode 13, and a top gate electrode 21, and a bottom MOS transistor, and a bottom MOS transistor. Is composed of a semiconductor thin film 11, a source electrode 12, a drain electrode 13, and a bottom gate electrode 22. As shown in the equivalent circuit of FIG. 11B, the double-gate optical sensor 10 includes a common channel region formed of the semiconductor thin film 11, TG (top gate terminal), BG (bottom gate terminal), and S (source terminal). ), And two MOS transistors with D (drain terminal).

The protective insulating film 20, the top gate electrode 21, the upper gate insulating film 15, the block insulating film 14, and the lower gate insulating film 16 are all visible light for activating the semiconductor thin film 11. Made of a material with a high transmittance of the line. Light entering through the sensor from the top gate electrode 21 passes through the top gate electrode 21, the top gate insulating film 15 and the block insulating film 14, and then enters the semiconductor thin film 11. It generates and accumulates charges (anode holes) in the channel region.

FIG. 12 is a schematic diagram illustrating an optical sensor system configured by the dual-gate optical sensor 10 being two-dimensionally arranged. As shown in this figure, the optical sensor system comprises a sensor array 100 consisting of a large number of optical sensors 10 arranged in an n × m matrix, the top terminal TG of the double-gate optical sensor 10. ) And top and bottom gate lines 101 and 102 connected in a row direction to the bottom gate terminal BG and top and bottom gate drivers 111 and 112 respectively connected to the top and bottom gate lines 101 and 102, respectively. And a data line 103 longitudinally connected to the drain terminal D of the gate optical sensor 10 and an output circuit 113 connected to the data line 103.

φtg and φbg represent control signals for generating reset pulses φTi and read pulses φBi, respectively, which will be described later, and φpg is a precharge pulse for controlling the timing at which the preliminary charging voltage Vpg is applied. Indicates.

In the structure described above, as will be described later, the light sensing function is realized by applying a predetermined voltage from the top gate driver 111 to the top gate terminal TG. On the other hand, the read function applies a predetermined voltage from the bottom gate driver 112 to the bottom gate terminal BG, and transmits the output voltage of the optical sensor 10 to the output circuit unit 113 through the data line 103. This is achieved by outputting serial data Vout.

13A to 13D are timing charts showing the control method of the optical sensor system, and show detection periods (process cycles in the i-th row) in the i-th row of the sensor array 100. First, the high level pulse voltage (reset pulse; i.e., Vtg = + 15V) (φTi) shown in FIG. 13A is applied to the top gate line 101 of the i-th row, and during the reset period (Treset) A reset operation for discharging the double-gate photo sensor 10 in the -th row is performed.

As a result, the bias voltage phi Ti at low level (i.e., Vtg = -15V) is applied to the top gate line 101 of the i-th row, thereby terminating the reset period (Treset) and charging the channel region. The charge accumulation period Ta that begins is started. During the charge accumulation period Ta, charges (anode holes) corresponding to the amount of light entering the respective sensors from the uppermost gate electrode side are accumulated in the channel region.

The preliminary charging pulse? Pg shown in FIG. 13C together with the preliminary charging voltage Vpg is applied to the data line 103 during the charge accumulation period Ta, and the charge is maintained at the drain electrode 13. After the preliminary charging period Tprch, a bias voltage (read pulse? Bi) of high level (i.e., Vbg = + 10V) shown in Fig. 13B is applied to the bottom gate line 102 of the i-th row. At this moment, the double-gate photosensor 10 in the i-th row is turned on to start the read period Tread.

During the read period Tread, the charge accumulated in the channel region has a polarity opposite to that of the charge accumulated in the channel region and regulates a low level voltage (ie, Vtg = -15V) applied to each top gate terminal TG. It plays a role. Accordingly, an n-type channel is formed at each bottom gate terminal BG by the voltage Vbg, and the voltage VD at the data line 103 is formed after the preliminary charging voltage Vpg is applied. It gradually decreases in response to the drain current. More specifically, when the charge accumulation period Ta is constant, the change tendency of the voltage VD on the data line 103 depends on the amount of received light. As shown in Fig. 13D, when the incident light is dark, that is, when a small amount of light enters, the voltage VD tends to decrease gradually, so that only a small charge is accumulated. On the other hand, when the incident light is bright, that is, when a large amount of light enters, the voltage VD tends to decrease suddenly, and thus a lot of charge is accumulated. The amount of light emitted may be calculated by detecting the voltage VD for a predetermined period after the read period Tread is started on the data line 103 or by detecting a period required until the voltage VD reaches a predetermined threshold voltage. It is understood that there is. The image read sensitivity corresponds to the charge accumulation period Ta. Assuming that the amount of light is constant, as the amount of accumulated charge increases, the image reading sensitivity also increases as the charge accumulation period Ta increases. Similarly, if the accumulated charge amount decreases, the image reading sensitivity also decreases as the charge accumulation period Ta decreases.

Image reading is achieved by sequentially performing the above-described drive-control on each of the lines of the sensor array 100 and by executing control on each of the lines in parallel at different timings at which the drive pulses do not overlap.

Although the case where the double-gate optical sensor is used as the optical sensor has been described above, in the case of the optical sensor system using a photodiode or phototransistor as the optical sensor: reset operation → charge accumulation operation → precharge operation → read operation Has the operating steps, and uses a similar driving sequence. The conventional optical sensor system described above has the following problems.

(1) In order to read the subject image in various use environments with the optical sensor system using the optical sensor described above, the image reading sensitivity (charge accumulation cycle) must be appropriately adjusted. Appropriate image reading sensitivity varies with ambient conditions, such as the brightness of external light, in the environment of use, and changes when the characteristics of the light sensor change. Therefore, in the prior art, a circuit for detecting the brightness of external light had to be additionally arranged. Optionally, the subject image is read at a different image reading sensitivity, for example, before the start of the normal reading operation of the subject image, and an optimum image reading sensitivity is determined based on the reading result. However, a read sensitivity setting method has not yet been developed which unconditionally and automatically sets an appropriate image reading sensitivity based on the reading result for all image reading sensitivity obtained by an operation performed at a different image reading sensitivity.

(2) If the reading sensitivity is set based on the result of the sensitivity adjustment reading operation, a foreign material may adhere to the sensing surface of the optical sensor or a defect occurs in the optical sensor member, and the reading obtained for each image reading sensitivity obtained in the reading operation. If the result is used directly, abnormal values are included in the readout, setting an appropriate image readout sensitivity fails, and prevents the correct reading operation of the subject image. For example, when such an optical sensor system is applied to a fingerprint reading device, the device causes an error in the fingerprint recognition process.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, are incorporated in the general description above and the detailed description of the embodiments given below, and serve to explain the subject matter of the invention. Do it.

1 is a block diagram showing an arrangement of an optical sensor system according to the present invention;

2 is a block diagram showing the arrangement of a controller applied to the optical sensor system according to the present invention;

3 is a flowchart showing operation of the first embodiment;

4 shows a specific row portion in which the sensitivity adjustment reading operation is performed according to the first embodiment of the photosensor arrangement, in which the specific row portion appears in association with the subject image;

5A to 5E are graphs showing changes in luminance data at specific row portions obtained by the sensitivity adjustment read operation in the first embodiment, respectively, with respect to the number of times a read operation has been performed;

6 is a graph showing how the dynamic range changes in the first embodiment with respect to the number of times a read operation is performed;

7 is a flowchart showing operation of the second embodiment;

Fig. 8 shows a specific row portion in which the sensitivity adjustment reading operation is performed according to the second embodiment of the photosensor arrangement, in which the specific row portion appears in association with the subject image;

9A to 9E are graphs showing how luminance data changes in a particular row portion obtained by the sensitivity adjustment read operation in the second embodiment, with respect to the number of times the read operation is performed;

10A to 10L are timing charts showing an embodiment of an image read sensitivity setting method applied to a sensitivity adjustment read operation performed in the first and second embodiments, respectively;

11A is a cross-sectional view showing the structure of a conventional double-gate optical sensor;

11B is an equivalent circuit diagram illustrating a double-gate photosensor;

12 is a schematic diagram illustrating an optical sensor system made up of two-dimensionally arranged double-gate optical sensors;

13A-13D are timing charts illustrating a conventional driving method for a dual-gate photosensor system.

It is an object of the present invention to provide a read sensitivity setting method capable of unconditionally and automatically setting an appropriate image reading sensitivity in order to accurately read a subject image in a changing use environment in an optical sensor system. The present invention is characterized in that all errors can be prevented when setting the image reading sensitivity even when foreign matters are on the sensing surface or the optical sensor member is defective.

In order to achieve the above features, an optical sensor system according to the present invention comprises: an optical sensor arrangement comprising a plurality of optical sensors arranged in two dimensions; Image reading means for reading a subject image using the optical sensor array; Sensitivity adjustment reading means for reading out the subject image while sequentially changing the image reading sensitivity of the photosensor of the specific row portion of the photosensor array; Optimum image reading sensitivity extraction means for extracting an optimum image reading sensitivity consistent with the image reading operation based on a predetermined measurement amount on the image pattern of the subject image read by the sensitivity adjusting reading means; And reading sensitivity setting means for setting an optimum image reading sensitivity to the reading sensitivity of the image reading means.

In such a system, the optimum image reading sensitivity extraction means extracts image reading sensitivity allowing a dynamic range of each image reading sensitivity measurement amount. The reading sensitivity setting means sets the extracted image reading sensitivity to an optimum image reading sensitivity. Therefore, the time required for the sensitivity adjustment reading operation is reduced, the amount of data made in the extraction process of the optimum image reading sensitivity is reduced, and thus the time required is reduced.

In this case, to determine whether there are any abnormal pixels in a particular row portion by checking whether the measurement amount belonging to a particular row portion and each corresponding row portion changes when the image reading sensitivity is switched from which to another. Abnormal pixel determination means is provided. Sensitivity adjustment read control means are also provided to perform a sensitivity adjustment read operation for a specific row portion other than the specific row portion for which abnormal pixels are determined to be present. With this structure, although the abnormal pixel exists in the specific row portion where the sensitivity adjustment read operation is performed, another specific row portion is selected to avoid the adverse effect of the abnormal pixel.

Additional objects and features of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be taught by practice of the invention. The objects and features of the present invention will be realized and attained by means and combinations particularly pointed out hereinafter.

The control method of the optical sensor system according to the present invention will be described in detail with reference to the accompanying drawings in various respects. In the embodiments described below, although the double-gate optical sensor is applied as an optical sensor, the present invention is not limited to the dual-gate optical sensor, but of course can be applied to an optical sensor system using another type of optical sensor. have.

1 is a block diagram showing an arrangement of an optical sensor system according to the present invention. The double-gate photosensor shown in FIG. 11A is used and is referenced when the arrangement of the photosensor system shown in FIG. 12 is required. Like reference numerals used in the optical sensor system shown in FIG. 12 denote like parts.

As shown in FIG. 1, an optical sensor system according to an embodiment includes an optical sensor array 100 that is two-dimensionally arranged and includes a double-gate optical sensor 10 shown in FIG. 11A, each at a predetermined timing. A top gate driver 111 for applying a predetermined reset pulse to the top gate terminal TG of the double-gate photosensor 10, and a bottom gate terminal BG of each double-gate photosensor 10 at a predetermined timing A bottom gate driver 111, an amplifier 116, a row switch 114, and a precharge switch 115 for applying a predetermined read pulse to the circuit. An output circuit 113 for applying to the optical sensor 10 respectively, and an analog / digital converter (hereinafter referred to as an A / D converter) 117 for converting a data voltage read as an analog signal into image data, which is a digital signal. , Optical sensor array (100) The controller 120 is adapted to control the reading operation of the subject image and to exchange data with the external function unit 200, and to control the sensitivity setting in the present invention, and for example, the read image data. RAM 130 for storing data related to the read sensitivity setting to be described.

The structure including the photosensor array 100, the top gate driver 111, the bottom gate driver 112 and the output circuit 113 is the same and has the same function as the photosensor system shown in FIG. In addition to this structure, the present embodiment adopts the A / D converter 117, the controller 120, and the RAM 130 to enable various controls to be described below.

The controller 120 outputs control signals φtg, φbg to the top and bottom gate drivers 111, 112, respectively, which sequentially drive each of the double-gate photosensors 10 of the photosensor array 100. A predetermined voltage (reset pulse and read pulse) is output to the top gate terminal TG and the bottom gate terminal BG. The controller 120 also outputs a control signal φpg to the preliminary charging switch 115 to control the reading operation of the subject image. The data line voltage read from the photosensor array 100 via the row switch 114 and the amplifier 116 is converted into a digital signal by the A / D converter 117 and provided as image data. The controller 120 also has a function of executing predetermined image processing on the image data, and writing or reading image data to or from the RAM 130. The controller 120 serves as an interface with the external function unit 200 that executes a predetermined process such as identification and correction of image data.

Top and bottom gate drivers 111 and 112 to set the optimum read sensitivity for reading the subject image according to the surrounding environment such as the brightness of the external light, i.e., the optimum charge accumulation period for each double-gate optical sensor 10. It also has another function to control the control signal outputted by).

As will be described below, the drive control method of the optical sensor system according to an embodiment of the present invention is based on the arrangement of the optical sensor system.

<First Embodiment>

A first embodiment of an optical sensor system sphere control method according to the present invention will be described with reference to various aspects of the accompanying drawings.

The first embodiment is characterized in that the image reading sensitivity is changed in a plurality of steps with respect to the light sensors in a particular row portion of the light sensor arrangement, and the subject image for the particular row portion is read out.

2 is a block diagram showing the arrangement of the controller 120 applied to the first embodiment. As shown in this figure, the controller 120 includes image data for the device controller 121 and the RAM 130 for controlling the top gate driver 111, the bottom gate driver 112, and the output circuit 113. , A data controller 122 for operating various data such as write data and read data, and a main controller 123 that collectively controls the controllers 121 and 122 and interfaces with external functional units.

The controller 120 compares the size of the specific measurement data based on the image data input as the digital signal from the optical sensor array 100 through the A / D converter 117 with the extracted maximum and minimum values 124. ), Received image data processed via an adder 125, an A / D converter 117, a data comparator 124, and an adder 125 having a function of calculating a difference between measured data, A data selector 126 for switching recording / reading from the data, re-entering the data comparator 124 and the adder 125, and outputting the data to the external function unit via the data controller 122 according to the received data; and Sensitivity setting for changing the control signals output from the device controller 121 to the top and bottom gate drivers 111 and 121 to optimize the read sensitivity of the optical sensor array based on the control signals from the data controller 122. Positive register 127.

The operation of the first embodiment in the operation control method of the optical sensor system using the controller 120 will be described with reference to FIG. FIG. 3 is a flowchart showing an operation performed up to an optimal image reading sensitivity setting, and FIG. 4 shows a specific row portion of the optical sensor array in which the sensitivity adjustment reading operation is performed according to the present embodiment. Is shown in relation to the subject image. This operation will be described with appropriate reference to the arrangement of the photosensor system shown in FIGS. 1 and 2.

In step S11 (sensitivity adjustment read operation) of Fig. 3, the main controller 123 controls the setting of the image read sensitivity for the sensitivity-adjusted read operation in the sensitivity setting register 127 via the data controller 122; And the sensitivity-adjusted reading operation of the subject image reading is performed at a plurality of different sensitivity while the image reading sensitivity changes step by step for each specific row portion of the subject image. Such operations are performed, for example, prior to the normal read operation on the subject image. As shown in Fig. 4, the sensitivity-adjustable read operation applicable to the sensitivity adjustment method of the first embodiment is performed using the arrangement of the matrix pattern units of 256 rows x 196 columns. In this light sensor arrangement, the center row (i.e. the n / 2th row) or several rows around it are considered to be a particular row portion, and the photosensor 10 corresponding to this particular row portion is reset. Thereafter, the preliminary charging operation and the reading operation are repeatedly performed at predetermined timings in such a manner that the charge accumulation period (image reading sensitivity) changes stepwise. In other words, the image reading sensitivity is made to change in correspondence with the number of times the reading operation is performed. The data is stored in the RAM 130 and is, for example, in the form of a table of (number of read operations) versus (image read sensitivity correspondence table). Specific methods for setting the image reading sensitivity will be described below.

In step S12 (image data conversion step) in Fig. 3, the image data read by the sensitivity-adjustment read operation is converted into a digital signal via the amplifier 116 and the A / D converter 117. The digital signal is supplied to the data comparator 124 of the controller 120 as luminance data corresponding to the light / dark pattern of the subject image. Luminance data is represented with 256 gray levels. Image data corresponding to each read operation is converted into luminance data values in the range of 0 to 255 and stored in the data comparator 124. Specific embodiments are shown in FIGS. 5A-5E. 5A to 5E show luminance data obtained when a read operation is performed a predetermined number of times in one row of a specific row portion, where the image read sensitivity increases as the number of times the read operation is performed. For example, FIGS. 5A-5E show when a read operation is performed 16 times (FIG. 5A), 32 times (FIG. 5B), 64 times (FIG. 5C), 96 times (FIG. 5D) and 128 times (FIG. 5E). Indicate how the luminance data in the row changes. The luminance data obtained by performing the read operation 16 times and 32 times is data having low image reading sensitivity. That is, since the sensitivity is insufficient, there are rows in which the data value is "0" (lower limit value). On the other hand, the luminance data obtained by performing the read operation 96 times and 128 times is data having high image reading sensitivity. Since the sensitivity is too high, there are rows in which the data value is "255" (upper limit).

In step S13 (step of extracting the maximum value and the minimum value with respect to the number of times the read operation has been performed) in FIG. Extracted. The extracted maximum and minimum values are output to the adder 125. In other words, luminance data representing the maximum value (ie, the gray level of the brightest pixel) and luminance data representing the minimum value (ie, the gray level of the darkest pixel) are extracted each time a read operation is performed.

Next, in step S14 of FIG. 3 (calculating the dynamic range in relation to the number of times the read operation is performed), the adder 125 determines the difference between the maximum value and the minimum value of the luminance data in relation to the number of times the read operation is performed. Calculate as a dynamic range. The result of this operation is stored in RAM 130 through the use of data selector 126. This dynamic range calculation step is executed each time a read operation is performed.

In step S15 (extracting a read operation indicating the maximum dynamic range) of FIG. 3, the data selector 126 reads the dynamic range of the read operation from the RAM 130 in relation to the number of times the read operation is performed, The read dynamic range is then provided to a data comparator 124. Based on the number of read operations performed and the trend of change in the dynamic range relative to each other, the maximum value DLmax of the dynamic range is determined in relation to the number of times the read operation is performed, and the number of repetitions RCa corresponding to the determined maximum value. Is extracted. In the embodiment shown in Figs. 5A to 5E, the luminance data obtained in the 16th and 32nd read operations have a minimum value saturated with the lower limit value (= 0), and the luminance data obtained in the 96th and 128th read operations are obtained by the upper limit value ( = 255). In contrast, the luminance data obtained in the 64th read operation does not have a value saturated with an upper limit or a lower limit. As a result, the dynamic range of the luminance data obtained in the 64th read operation is larger than the dynamic range of the other luminance data. Thus, the maximum value is DLmax, and the repetition number RCa of the read operation corresponding to the maximum value is 64.

Next, step S16 (extracting with reference to the sensitivity) of FIG. 3 is executed based on the extracted number RCa of the read operation. In the step, the image reading sensitivity (i.e., charge accumulation period) corresponding to the extracted number RCa of the read operation corresponds to the table stored in the RAM 130, i.e. (number of read operations RCa) versus (image reading sensitivity). It is extracted by referring to the table of table).

In step S17 of FIG. 3 (step of setting the extracted sensitivity), the main controller 123 causes the data controller 122 to rewrite the data in the sensitivity setting register 127, whereby The image reading sensitivity is set at the extracted image reading sensitivity. This allows to terminate the optimal image read sensitivity setting based on the sensitivity-adjusted read operation.

According to the sensitivity setting method of the first embodiment, one or more specific rows (specific row portions) of the optical sensor array are selected, and the sensitivity-adjusted reading operation (repetitively reading the subject image at predetermined intervals) is a reset operation. It is then executed on the selected part of the row. In this way, the subject image can be read while the image reading sensitivity (charge accumulation cycle) is gradually changed. In this way, the time required for the sensitivity-adjusted read operation can be as short as possible.

Compared with the optimum image reading sensitivity extracted based on conventional read image data corresponding to one frame, the first embodiment uses image data corresponding to one or several specific rows (specific row portions). This can significantly reduce the amount of data used for extraction of the optimum image reading sensitivity, resulting in a marked reduction in processing load. In addition, the time required for setting the optimum image reading sensitivity can be significantly reduced.

Moreover, the sensitivity-adjusted read operation is limited to a specific row portion. Compared with the conventional case where the sensitivity-adjusted reading operation is performed for the entire light receiving area of the light sensor array, the first embodiment significantly lowers the possibility of inclusion of abnormal pixels (no points or shiny points), and this abnormality. The pixels are due to foreign matters on the target area or defects of the optical sensor. As a result, the possibility that an inappropriate image reading sensitivity is set by the presence of abnormal pixels is significantly lowered. Therefore, an error is prevented in the fingerprint recognition process.

In the first embodiment, the particular row portion is the center row (n / 2th row) of the matrix of n rows x m columns (n = 256, m = 196) and several rows located around it. Needless to say, the invention is not limited to this embodiment. The specific row portion can be selected from any area as long as it shows a clear luminance pattern (contrast) of the subject image. For example, the particular row portion may be located near the center row or may be selected in another area.

Second Embodiment

A second embodiment of a drive control method of an optical sensor system according to the present invention will be described with reference to the accompanying drawings.

In the above-described first embodiment, the sensitivity-adjusted read operation is performed in one or several rows of specific row portions. Compared to the case where the entire light-receiving area of the photosensor array, or a selected one of them, is subjected to a read operation, this significantly reduces the probability of abnormal pixels in the object specific row portion. However, the probability that an abnormal pixel exists in a specific row portion is never "0".

Similar to the first embodiment, the second embodiment seeks to reasonably prevent adverse effects due to retaining abnormal pixels when a sensitivity-adjusted read operation is performed for one or several rows of a specific row portion. The controller provided in the second embodiment is similar in structure to the controller 120 employed in the first embodiment, and is represented again by the structural blocks shown in FIG.

7 is a flowchart showing how the controller 120 controls the operation of the photosensor system in the second embodiment of the present invention. In the flowchart, operations performed up to the optimum image reading sensitivity setting are described. Fig. 8 shows a specific row portion of the photosensor array in which the sensitivity-adjustment reading operation is performed according to the second embodiment, in which the specific row portion is described as Rp in relation to the subject image. In the following description, reference is made to the structure of the photosensor system shown in FIGS. 1 and 2 as necessary. Similar or corresponding constituent members will be designated by the same reference numerals as used in the description of the first embodiment, and a brief description will be given for such constituent members.

The sensitivity-adjusting read operation provided in the sensitivity adjustment method of the second embodiment is performed for a specific row portion Rp of the photosensor array 100. These photosensors are arranged in units of a matrix pattern of 256 rows x 196 columns, as shown in FIG. In the following description, the abnormal pixel IL3 exists at the position of the specific row portion Rp and column Lq, and the foreign matter on the sensing surface of the optical sensor array, the defect member of the optical sensor, etc. Assume the luminance data value is "0".

Step S21 (sensitivity-adjustment read operation) of Fig. 7 is performed in a manner similar to that of step S11 of the first embodiment. That is, the optical sensor corresponding to the specific column portion Rp of the optical sensor array 100 shown in FIG. 8 is controlled in such a manner that the charge accumulation period (i.e., image read sensitivity) varies step by step at predetermined intervals. The sensitivity-adjusted reading operation is performed with a plurality of image reading sensitivity on the subject image, and the plurality of image reading sensitivity corresponds to the number of times that the reading operation has been performed. These operations are performed prior to normal reading of the subject image.

Step S22 (image data conversion step) of Fig. 7 is executed in a manner similar to that of step S12 of the first embodiment. The image data read by the sensitivity-adjusted read operation is converted into luminance data. Luminance data is provided to the controller 120 and stored in the RAM 130. Specific examples are shown in FIGS. 9A-9E. Similar to FIGS. 5A-5E, FIGS. 9A-9E show that the read operation is performed 16 times (FIG. 9A), 32 times (FIG. 9B), 64 times (FIG. 9C) in a particular column portion (one column in this case). , 96 times (FIG. 9D) and 128 times (FIG. 9E), show how the luminance data change in a row. The luminance data includes luminance data indicating the minimum value "0" in the number of rows Lq by the abnormal pixel IL shown in FIG. The luminance data obtained when the read operation is performed 16 and 32 times is data having low image reading sensitivity. Therefore, since the sensitivity is insufficient, there are rows in which the data value is "0" (lower limit value). On the other hand, the luminance data obtained when the read operation is performed 96 times and 128 times is data having high image reading sensitivity. Since the sensitivity is too high, there are rows in which the data value is "255" (upper limit).

Next, step S23 (step of extracting data of each read operation by comparing with the same column data and extracting) shown in FIG. 7 is performed. In this step, the data selector 126 extracts the same row of luminance data from the luminance data stored in the RAM 130 and corresponding to each read operation. The extracted luminance data is supplied to the data comparator 124 to compare the luminance data of the same row.

Then, step S24 (step of determining change in the same row data) shown in Fig. 7 is performed. This step is to determine whether there are rows in which the same luminance data remains after each read operation.

If there is a column in which the luminance data has not changed, the pixel corresponding to this column is regarded as abnormal, and the specific row portion in which the sensitivity-adjusted read operation is performed is determined to contain the abnormal pixel.

If there are no columns in which the same luminance data remains, it is determined that the specific row portion in which the sensitivity-adjusted read operation is performed does not contain abnormal pixels.

The result of this determination is supplied from the data comparator 124 to the main controller 123. In the example shown in Figs. 9A to 9E, an abnormal pixel IL appears, and the luminance data corresponding to the row number Lq is " 0 " regardless of the number of times a read operation has been performed. In other words, there is a row in which the luminance data remains the same after each read operation, and the row Rq is determined to contain abnormal pixels.

A description will be given of a particular method by which the luminance data can be checked for the presence / absence of abnormal pixels by detecting whether there are rows that do not change before and after each read operation. For example, the sensitivity-adjusted read operation is controlled as follows: A flag is set for each row based on the luminance data of the rows obtained by the first read operation. The optical data obtained by the sequential read operation is compared with the luminance data obtained by the first read operation. This comparison is performed for each row. The luminance data of a row is different from the original luminance data, and the flag corresponding to that row is reset. As long as the pixel is normal, the luminance data on the pixel changes with the change in the image reading sensitivity. As a result, the flag of the pixel is reset. On the other hand, if the pixel is abnormal, the luminance data of the row containing the abnormal pixel does not change even if the image reading sensitivity changes. The value of the luminance data is, for example, an upper limit value, a lower limit value, or a constant value therebetween. As a result, the flag continues in the setting state. As seen from these, abnormal pixels appearing in a particular column portion where the sensitivity-adjusted read operation is to be performed can be detected by monitoring the state of the flag.

In step S24 (determining a change in the same row data), it is determined whether an abnormal pixel exists, and step S25 (changing a specific column portion to which a sensitivity-adjustable read operation is to be performed) shown in Fig. 7 is executed. In this step, the main controller 123 causes the device controller 121 to change the particular column portion for which the sensitivity-adjusted read operation is to be performed. Therefore, the operation started from step S21 (sensitivity-adjustment read operation) is performed again. Only a specific row portion in which the sensitivity-adjustment read operation is newly executed is required for another specific row portion rather than the specific row portion in which the abnormal pixel IL is detected. For example, another particular row portion may be adjacent to the top region or the bottom region of the row Rp, or may be a predetermined number of rows away from the row portion. The processing in steps S21-S24 is repeatedly performed until it is determined that the specific row portion to which the sensitivity-adjustment read operation is to be performed does not contain abnormal pixels.

If step S24 (determining the change in the same row data) determines that there are no abnormal pixels in a particular row portion where the sensitivity-adjusted read operation is to be performed, step S26 (maximum value in each read operation) shown in FIG. And extracting the minimum value. In this step, the maximum and minimum values are extracted from the luminance data obtained in each read operation and provided to the data comparator 124, and output to the adder 125 as in step S13 of the first embodiment.

As a result, steps S27 (calculate the dynamic range in each read operation), S28 (extract the read operation representing the maximum dynamic range), and S29 (reference and extract the sensitivity) shown in FIG. , Step S30 (step of setting the extracted sensitivity) is executed sequentially. These steps are similar to steps S14 to S17 of the first embodiment described above. That is, the dynamic range of the luminance data obtained in each read operation is calculated by the adder, and the data comparator 124 checks the dynamic range change trend (Fig. 31) in correlation with the number of times the read operation is performed, so that the dynamic range is maximum. Detects a read operation. The image reading sensitivity (charge accumulation period) corresponding to this reading operation is set in the sensitivity setting register 127, thereby ending the optimum image reading sensitivity setting based on the sensitivity-adjusting reading operation.

In the sensitivity setting method of the second embodiment, if an abnormal pixel appears in a specific row portion where a sensitivity-adjusted reading operation is to be performed due to foreign matter on the sensing surface of the optical sensor array, all defects of the optical sensor, etc., such an abnormal pixel is Can be easily detected. Based on this detection, a sensitivity-adjusted read operation is performed on another specific row portion where no abnormal pixel exists. In this way, luminance data for a particular row portion that does not contain abnormal pixels is obtained as luminance data for sensitivity adjustment. Although abnormal pixels are included in the specific row portion first selected for the sensitivity-adjusted read operation, the adverse effects caused by these abnormal pixels can be eliminated.

In addition, the optimum image reading operation can be determined unconditionally based on the dynamic range of the luminance data obtained by the sensitivity-adjusting reading operation. Therefore, the image reading sensitivity remains optimal even when the sensitivity-adjusted reading operation is performed for the specific row portion which is different from the initially selected specific row portion. Normal reading operations on the subject image can be performed in a reliable manner regardless of ambient conditions such as ambient lighting conditions. Therefore, an error can be prevented in a fingerprint recognition process or the like.

In the above-described first and second embodiments, the specific row portion on which the sensitivity-adjusted reading operation is to be executed is predetermined, for example, at the center of the light sensor. The present invention is not limited to this. In other words, a specific row portion does not need to be specified in advance. For example, the entire area of the subject image or a predetermined area thereof is read out at an arbitrary image reading sensitivity. In this case, a specific row portion or area most suitable for image reading is extracted, and one specific row portion or several specific row portions is determined based on the extracted data.

In the above-described embodiments, an image reading sensitivity (charge accumulation period) setting method that can be applied to the sensitivity-adjusting reading operation will be described with reference to various aspects of the accompanying drawings. In the following description, reference will be made to the structure of the light sensor system shown in FIGS. 1 and 2 and the structure of the light sensor system shown in FIGS. 11 and 12.

10A to 10L are timing charts showing an embodiment of a sensitivity-adjusted read operation that can be applied to the sensitivity-adjusted read operation performed in the first and second embodiments, respectively. In the following description, it is assumed that one particular row portion on which the sensitivity-adjusted read operation is to be performed is a row centered.

As shown in Figs. 10A to 10E, the image reading sensitivity setting method of the embodiment initializes only the center row (n / 2th row) of the optical sensor array shown in Fig. 12, that is, the double-gate optical sensors of a specific row. . More specifically, the waveforms φT1 to φTn / 2-1 and φTn / 2 + 1 to φTn applied to the first to (n / 2-1) th rows and the (n / 2 + 1) th to nth rows are Set to low level, these rows are among the top gate lines 101 connected to the top gate terminal TG of the double-gate photosensor 10 in the row direction, and a single reset pulse φ Tn / 2 is n / 2 Only on the first row. In this way, the reset period Treset starts, and only the double-gate photo sensor 10 of the (n / 2) th row is initialized.

Then, the reset pulse? Tn / 2 drops and the reset period is terminated. Then, the charge accumulation cycle starts, and charges (holes) are generated and accumulated in the channel region according to the amount of light entering the n / 2th row of the double-gate photosensor 10 from the top gate electrode 21 side. .

As a result, as shown in FIGS. 10F to 10K, the precharge signal φpg and the read pulse φBn / 2, which are internally defined for the bottom gate line 102 of the n / 2th row, have a predetermined interval Tint. ) And the number of times (x times, x is an integer greater than 1).

Waveforms φB1 to φBn / 2-1 and φBn / 2 + 1 to to which are applied to the bottom gate line 102 of the first to (n / 2-1) th rows and the (n / 2 + 1) th to nth rows φ Bn is set at a low level.

As shown in Fig. 10L, the drain voltage thus changes corresponding to the charge accumulated during the charge accumulation period TB1, TB2, ..., TBx between the end of the reset period Treset and the start of the read time Tread. (VD1, VD2, ..., VDm) are read sequentially.

By this sensitivity-adjusted read operation, the charge accumulation period of a specific row portion increases step by step for a predetermined time interval Tint. As a result, the image data is read from the subject image, with the image corresponding to the specific row portion to be read out with a plurality of different image reading sensitivitys.

In the above-described sensitivity-adjusted read operation, the photosensors corresponding to one particular row portion are initially reset, and the read operation is repeatedly performed on them. In this relationship, it should be noted that the amount of charge accumulated in each optical sensor is changed by the read operation. To solve this problem, the charge accumulation period of each read operation is modified according to the actual charge accumulation period based on the correlation between the number of read operations performed and the accumulated charge amount.

As described above, according to the sensitivity setting method of the above embodiments, the sensitivity-adjusted reading operation is performed on the subject image while changing the image reading sensitivity step by step. The image reading sensitivity is easily determined based on the distribution of the dynamic range of the luminance data obtained at each image reading sensitivity to ensure an optimum image reading state. This image reading sensitivity (charge accumulation period) can be used as the optimum sensitivity, whereby the sensitivity setting is made automatically. However, since the sensitivity setting process is obtained using a real object, it is not necessary to use a standard sample or the like. Even when the brightness of the subject image changes according to the change in the ambient light, the optimum image reading sensitivity can be set according to the change in the ambient light. This eliminates the need to adopt special circuitry designed to sense ambient light. Moreover, even if the photosensors vary with the characteristics, the image data obtained from these photosensors is used to determine the optimum sensitivity. This significantly reduces the adverse effects resulting from the change in properties.

Only a specific row portion of the light sensor arrangement is used for the sensitivity-setting read operation. Instead, if the appearance of an abnormal pixel is determined, a specific row portion not containing the abnormal pixel is used for the sensitivity-adjusted read operation. Therefore, the image reading sensitivity can be set to an optimal value without adverse effects caused by abnormal pixels resulting from foreign matters on the sensing surface of the optical sensor array, defects of the optical sensor member, and the like.

In each of the above-described embodiments, the sensitivity-adjusted read operation is usually executed before the read operation. The present invention is not limited thereto. For example, a sensitivity-adjusted read operation is performed in the standby state. In other words, the standby state is a state in which the light sensor system is operated although the target is not yet placed.

In addition, the sensitivity-adjusted read operation may be performed whenever a normal read operation is performed on the subject image. The present invention is not limited thereto. For example, the sensitivity-adjusted read operation may be performed only when there is a change in the use environment or when a predetermined time has elapsed.

The image reading sensitivity (charge accumulation period) setting method applied to the sensitivity setting process according to the present invention is not limited to the above embodiments. As long as image data of the subject image can be obtained with different reading sensitivity, a series of processes described in the prior art: reset operation → charge accumulation operation → preliminary charging operation → reading operation can be repeated several times with different reading sensitivity, This results in image data at different read sensitivitys. Optionally, of course, all other methods can be adopted.

Claims (18)

An optical sensor array 100 in which a plurality of optical sensors 10 are two-dimensionally arranged; Image reading means for reading a subject image with a predetermined image reading sensitivity using the photosensor array (100); Among the plurality of optical sensors 10 of the optical sensor array 100, only the optical sensor 10 located in a specific row is used, and the same image of the subject image corresponding to the optical sensor located in the specific row is used. Sensitivity-adjusting reading means for reading a part of the image a plurality of times with a plurality of different image reading sensitivitys; Suitable for the image reading operation, based on a predetermined measurement amount relating to the image pattern of the images for each of the plurality of different image reading sensitivity to the same portion of the subject image read out multiple times by the sensitivity-adjusting reading means. Optimum image reading sensitivity extraction means for extracting an optimum image reading sensitivity; And And a reading sensitivity setting means for setting the optimum image reading sensitivity to the reading sensitivity of the image reading means. 2. Optical sensor system according to claim 1, wherein the optical sensors (10) of a particular row portion of the optical sensor array (100) are optical sensors (10) of several rows of the optical sensor array (100). 2. Optical sensor system according to claim 1, wherein the optical sensors 10 in a particular row portion of the optical sensor array 100 are optical sensors 10 in one particular row of the optical sensor array 100. . 2. The abnormal pixel determination means according to claim 1, wherein it is determined whether a specific row portion contains abnormal pixels by checking whether a measurement amount corresponding to one row of a specific row portion is changed each time the image reading sensitivity is switched differently. The optical sensor system further comprises. 5. The apparatus according to claim 4, wherein if the abnormal pixel determination means determines that an abnormal pixel exists in a specific row portion, a sensitivity-adjusted read control means for performing a sensitivity-adjusted read operation to a specific row portion other than the specific row portion is made. The optical sensor system further comprises. The optical sensor system according to claim 1, wherein the predetermined measurement amount in said optimum reading sensitivity extracting means is luminance data corresponding to an image pattern of a subject image read by said sensitivity-adjusting reading means. 2. Optical sensor system according to claim 1, wherein the image reading sensitivity of the optical sensor array (100) is set by adjusting the charge accumulation period of the optical sensor (10). The method of claim 1, wherein the optimum reading sensitivity extraction means, Measurement amount comparison means for extracting a maximum value and a minimum value of a measurement amount associated with an image pattern of the subject image for each image reading sensitivity based on the subject image read by the sensitivity-adjusting reading means; Dynamic range calculation means for calculating a dynamic range of the measurand based on the maximum and minimum values of the measurand extracted for each image reading sensitivity; And And a maximum dynamic range extracting means for extracting an image reading sensitivity having a maximum dynamic range among the dynamic ranges of the measured amounts calculated for each image reading sensitivity. The method of claim 1, Each optical sensor 10 has a source electrode 12 and a drain electrode 13 formed through a channel region 14 made of a semiconductor layer, and a top gate electrode 21 formed at least above and below the channel region through insulating films. ) And the bottom gate electrode 22, One of the top gate electrode and the bottom gate electrode is used as the light emitting side of the light, and And charges corresponding to the amount of light irradiated from the light emitting side of the light are generated and accumulated in the channel region. Performing a sensitivity-adjusted reading operation of the subject image reading associated with the optical sensors 10 in the specific row portion while the image reading sensitivity of the photosensor array 100 is changed in a plurality of steps; Extracting the image reading sensitivity suitable for the reading operation of the subject image based on a predetermined measurement amount associated with the image pattern of the subject image read by the sensitivity-adjusting reading operation; Setting the extracted image reading sensitivity to a reading sensitivity in a reading operation of the subject image; And Performing an image reading operation of the subject image reading with the set reading sensitivity; 2. The driving control method of an optical sensor system having an optical sensor array configured as a plurality of optical sensors two-dimensionally arranged. 11. A drive control method according to claim 10, characterized in that the photosensors (10) of the particular row portion are photosensors (10) of several rows. 11. A drive control method according to claim 10, wherein the photosensors (10) of the particular row portion are photosensors (10) of one row. The method of claim 10, Determining whether a specific row portion contains abnormal pixels by checking whether a measurement amount corresponding to one row of a specific row portion changes each time the image reading sensitivity is changed differently. Drive control method. The method of claim 13, And if the abnormal pixel determination step determines that there are abnormal pixels in the specific row portion, performing a sensitivity-adjustment read operation on the specific row portion different from the specific row portion. The drive control method according to claim 10, wherein the predetermined measurement amount is luminance data relating to an image pattern of a subject image read by a sensitivity-adjusted read operation. 11. The drive control method according to claim 10, wherein the image reading sensitivity of the photosensor array (100) is set by adjusting the charge accumulation period of the photosensor (10). The method of claim 10, wherein the extracting of the image reading sensitivity comprises: Extracting a maximum value and a minimum value of a measurement amount associated with an image pattern of the subject image for each image reading sensitivity based on the subject image read by the sensitivity-adjusted reading operation; Calculating a dynamic range of the measurand based on the maximum and minimum values of the measurand extracted for each image reading sensitivity; And Extracting an image reading sensitivity having a maximum dynamic range among the dynamic ranges of the measured amounts calculated for each image reading sensitivity; Drive control method, characterized in that consisting of. The method of claim 10, Each optical sensor 10 has a source electrode 12 and a drain electrode 13 formed through a channel region 14 made of a semiconductor layer, and a top gate electrode 21 formed at least above and below the channel region through insulating films. ) And the bottom gate electrode 22, One of the top gate electrode and the bottom gate electrode is used as the light emitting side of the light, and And charges corresponding to the amount of light irradiated from the light emitting side of the light are generated and accumulated in the channel region.