WO2003003719A1 - Photosensor system and drive control method thereof - Google Patents
Photosensor system and drive control method thereof Download PDFInfo
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- WO2003003719A1 WO2003003719A1 PCT/JP2001/009438 JP0109438W WO03003719A1 WO 2003003719 A1 WO2003003719 A1 WO 2003003719A1 JP 0109438 W JP0109438 W JP 0109438W WO 03003719 A1 WO03003719 A1 WO 03003719A1
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- image reading
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
- H04N23/70—Circuitry for compensating brightness variation in the scene
- H04N23/71—Circuitry for evaluating the brightness variation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/50—Control of the SSIS exposure
- H04N25/57—Control of the dynamic range
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
- H04N23/10—Cameras or camera modules comprising electronic image sensors; Control thereof for generating image signals from different wavelengths
Definitions
- the present invention relates to a photosensor system having a photosensor array constituted by two-dimensionally arraying a plurality of photosensors, and a drive control method thereof.
- Imaging apparatuses such as electronic still cameras, video cameras, and the like have come to be very widely used. These imaging apparatuses employ a solid-state imaging device, such as a CCD (Charge Coupled Device) , which serves as a photoelectric converting device for converting an image of a to-be- photographed subject into an image signal.
- the CCD has a structure in which photosensors (light receiving elements) such as photodiodes, or thin film transistors (TFT: Thin Film Transistor) are arranged in a matrix, and the amount of electron-hole pairs (the amount of charge) generated corresponding to the amount of light entering the light receiving section of each sensor is detected by a horizontal scanning circuit and vertical scanning circuit to detect the luminance of radiation.
- photosensors light receiving elements
- TFT Thin Film Transistor
- FIG. 11A is a sectional view showing the structure of a double-gate photosensor 10.
- FIG. 11B is a circuit diagram showing the equivalent circuit of the double- gate photosensor 10.
- the double-gate photosensor 10 comprises a semiconductor thin film 11 formed of amorphous silicon or the like, n + -silicon layers 17 and 18, source and drain electrodes 12 and 13 respectively formed on the n + -silicon layers 17 and 18, a top gate electrode 21 formed above the semiconductor thin film 11 via a block insulating film 14 and upper gate insulating film 15, a protective insulating film 20 provided on the top gate electrode 21, and a bottom gate electrode 22 provided below the semiconductor thin film 11 via a lower gate insulating film 16.
- the double-gate photosensor 10 is provided on a transparent insulating substrate 19 formed of glass or the like.
- the double-gate photosensor 10 includes an upper MOS transistor comprised of the semiconductor thin film 11, source electrode 12, drain electrode 13, and top gate electrode 21, and a lower MOS transistor comprised of the semiconductor thin film 11, source electrode 12, drain electrode 13, and bottom gate electrode 22.
- the double-gate photosensor 10 is considered to include two MOS transistors having a common channel region formed of the semiconductor thin film 11, TG (Top Gate terminal), BG (Bottom Gate terminal), S (Source terminal), and D (drain Terminal).
- the protective insulating film 20, top gate electrode 21, upper gate insulating film 15, block insulating film 14, and lower gate insulating film 16 are all formed of a material having a high transmittance of visible light for activating the semiconductor thin film 11.
- Light entering the sensor from the top gate electrode 21 side passes through the top gate electrode 21, upper gate insulating film 15, and block insulating film 14, and then enters the semiconductor thin film 11, thereby generating and accumulating charges (positive holes) in the channel region.
- FIG. 12 is a schematic view showing a photosensor system constituted by two-dimensionally arraying double-gate photosensors 10.
- the photosensor system comprises a sensor array 100 that is constituted of a large number of double-gate photosensors 10 arranged in an n x m matrix, top and bottom gate lines 101 and 102 that respectively connect the top gate terminals TG and bottom gate terminals BG of the double-gate photosensors 10 in a row direction, top and bottom gate drivers 111 and 112 respectively connected to the top and bottom gate lines 101 and 102, data lines 103 that respectively connect the drain terminals D of the double-gate photosensors 10 in a column direction, and an output circuit section 113 connected to the data lines 103.
- ⁇ tg and ⁇ bg represent control signals for generating a reset pulse ⁇ Ti and readout pulse ⁇ Bi, respectively, which will be described later, and ⁇ pg represents a pre-charge pulse for controlling the timing at which a pre-charge voltage Vpg is applied.
- the photosensing function is realized by applying a predetermined voltage from the top gate driver 111 to the top gate terminals TG, while the readout function is realized by applying a predetermined voltage from the bottom gate driver 112 to the bottom gate terminals BG, then sending the output voltage of the photosensors 10 to the output circuit section 113 via the data lines 103, and outputting serial data Vout .
- FIGS. 13A to 13D are timing charts showing a method of controlling the photosensor system, and showing a detecting period (i-th row processing cycle) in the i-th row of the sensor array 100.
- an n-type channel is formed by the voltage Vbg at each bottom gate terminal BG, the voltage VD at the data lines 103 gradually reduces in accordance with the drain current with lapse of time after the pre- charge voltage Vpg is applied. More specifically, the tendency of change in the voltage VD at the data lines 103 depends upon the amount of received light in the case where the charge accumulating period Ta is constant. As shown in FIG. 13D, the voltage VD tends to gradually reduce when the incident light is dark, i.e., a small amount of light is received, and hence only small charges are accumulated, whereas the voltage VD tends to suddenly reduce when the incident light is bright, i.e., a large amount of light is received, and hence large charges are accumulated.
- the amount of radiation can be calculated by detecting the voltage VD at the data lines 103 a predetermined period after the start of the readout period T reac j, or by detecting a period required until the voltage VD reaches a predetermined threshold voltage.
- An image reading sensitivity corresponds to the charge accumulating period Ta . Assuming that the amount of light is constant, the amount of charge accumulated increases and the image reading sensitivity enhanced in accordance with an increase in the charge accumulating period Ta . Likewise, the amount of charge accumulated decreases and the image reading sensitivity degraded in accordance with a decrease in the charge accumulating period Ta.
- Image reading is performed by sequentially executing the above-described drive-control for each line of the sensor array 100, by executing the control for each line in a parallel manner at different timings at which the driving pulses do not overlap.
- the image reading sensitivity charge accumulating period
- the proper image reading sensitivity changes depending on changes in ambient conditions such as the illuminance of external light in a use environment, and also changes when the characteristics of the photosensor change.
- a circuit for detecting the illuminance of external light must be additionally arranged.
- a subject image is read at different image reading sensitivities before the start of normal reading operation of that subject image, and an optimal image reading sensitivity must be determined on the basis of a read result.
- the present invention is advantageous in that any malfunction in setting the image reading sensitivity is prevented even if a foreign substance attaches to the sensing surface of a photosensor, or a photosensor element becomes defective .
- a photosensor system comprises: a photosensor array constituted by two-dimensionally arranging a plurality of photosensors; image reading means for reading a subject image by use of the photosensor array; sensitivity-adjusting reading means for changing the image reading sensitivity of the photosensors of the specific row section of the photosensor array, stepwise and reading the subject image; optimal image reading sensitivity-extracting means for extracting an optimal image reading sensitivity suited to the image reading operation on the basis of a predetermined measurement amount regarding an image pattern of the subject image read by the sensitivity-adjusting reading means; and reading sensitivity-setting means for setting the optimal image reading sensitivity as a reading sensitivity of the image reading means .
- the optimal image reading sensitivity-extracting means extracts an image reading sensitivity that allows the dynamic range of the measurement amount of each image reading sensitivity.
- the reading sensitivity-setting means sets the extracted image reading sensitivity as an optimal image reading sensitivity.
- abnormal pixel determining means is provided for determining whether or not any abnormal pixel exists in the specific row section by checking if the measurement amount pertaining to the specific row section and corresponding to each column changes when the image reading sensitivity is switched from one to another.
- Sensitivity-adjusting reading control means is also provided for executing sensitivity-adjusting reading operation for a specific row section other than the specific row section where the abnormal pixel is determined to exist.
- FIG. 1 is a block diagram showing an arrangement of a photosensor system according to the present invention
- FIG. 2 is a block diagram showing an arrangement of a controller applied to the photosensor system according to the present invention
- FIG. 3 is a flow chart showing the operation of the first embodiment
- FIG. 4 shows a specific row section of a photosensor array for which the sensitivity-adjusting reading operation is performed according to the first embodiment, the specific row section being illustrated in relation to a subject;
- FIGS. 5A to 5E are graphs each showing changes in lightness data in a specific row section that are obtained by the sensitivity-adjusting reading operation in the first embodiment, in relation to the number of times the reading operation is performed;
- FIG. 6 is a graph showing how a dynamic range changes in the first embodiment, in relation to the number of times the reading operation is performed;
- FIG. 7 is a flow chart showing the operation of the second embodiment
- FIG. 8 shows a specific row section of a photosensor array for which the sensitivity-adjusting reading operation is performed according to the second embodiment, the specific row being illustrated in relation to a subject image;
- FIGS. 9A to 9E are graphs showing how lightness data on a specific row section changes in the second embodiment, in relation to the number of times the reading operation is performed;
- FIGS. 10A to 10L are timing charts showing the embodiment of an image reading sensitivity setting method applied to the sensitivity-adjusting reading operation executed in each of the first and second embodiments;
- FIG. 11A is a sectional view showing the structure of a conventional double-gate photosensor;
- FIG. 11B is an equivalent circuit diagram showing the double-gate photosensor
- FIG. 12 is a schematic view showing a photosensor system constituted by two-dimensionally arraying double-gate photosensors
- FIGS. 13A to 13D are timing charts showing a conventional drive method for the double-gate photosensor system.
- FIG. 1 is a block diagram showing an arrangement of a photosensor system according to the present invention.
- the double-gate photosensor shown in FIG. 11A is used, and the arrangement of the photosensor system shown in FIG. 12 will be referred to if necessary.
- the same reference numerals as in the photosensor system shown in FIG. 12 denote the same parts .
- the photosensor system comprises a photosensor array 100 including double-gate photosensors 10 shown in FIG. 11A that are arrayed two-dimensionally, a top gate driver 111 for applying a predetermined reset pulse to a top gate terminal TG of each double-gate photosensor 10 at a predetermined timing, a bottom gate driver 112 for applying a predetermined readout pulse to a bottom gate terminal BG of each double-gate photosensor 10 at a predetermined timing, an output circuit section 113 constituted by an amplifier 116, and a column switch 114 and pre-charge switch 115 for reading a data line voltage and applying a pre-charge voltage to each double-gate photosensor 10, respectively, an analog/digital converter (to be referred to as an A/D converter hereinafter) 117 for converting the read data voltage as an analog signal into image data as a digital signal, a controller 120 which is adopted to control the operation of reading a subject image by the photosensor array 100, and to exchange data with an external function section 200, and
- A/D converter analog/digit
- the structure including the photosensor array 100, top gate driver 111, bottom gate driver 112, and output circuit section 113 is the same as and has the same function as the photosensor system shown in FIG. 12.
- this embodiment adopts the A/D converter 117, controller 120, and RAM 130 to enable various types of control as described below.
- the controller 120 outputs control signals ⁇ tg and ⁇ bg to the top and bottom gate drivers 111 and 112, respectively, which, in turn, output predetermined voltages (reset pulse and readout pulse) to the top gate terminal TG and bottom gate terminal BG of each double-gate photosensor 10 of the photosensor array 100, respectively.
- the controller 120 also outputs a control signal ⁇ pg to the pre-charge switch 115 to control execution of the operation of reading a subject image.
- a data line voltage read from the photosensor array 100 via the column switch 114 and amplifier 116 is converted into a digital signal by the A/D converter 117, and supplied as image data.
- the controller 120 also has a function of executing predetermined image processing for image data, writing or reading image data into or from the RAM 130.
- the controller 120 serves as an interface with the external function section 200 that executes predetermined processing such as image data identification, modification, and the like.
- the controller 120 has another function of controlling control signals to be output to the top and bottom gate drivers 111 and 112 to set an optimal reading sensitivity for reading a subject image in accordance with ambient environments such as the illuminance of external light, i.e., an optimal charge accumulating period for each double-gate photosensor 10.
- photosensor system drive control methods are based on the arrangement of this photosensor system.
- the first embodiment is characterized in that it changes an image reading sensitivity in relation to the photosensor in a specific row section of the photosensor array at a plurality of stages, and reads a subject image in relation to the specific row section.
- FIG. 2 is a block diagram showing an arrangement of a controller 120 applied to the first embodiment.
- the controller 120 comprises a device controller 121 for controlling a top gate driver
- the controller 120 further comprises a data comparator 124 for comparing the sizes of specific measurement data based on image data input as a digital signal from a photosensor array 100 via an A/D converter 117 to extract maximum and minimum values, an adder 125 having a function of calculating, e.g., the difference between measurement data, a data selector 126 for receiving processed image data via the A/D converter 117, data comparator 124, and adder 125, and switching write/readout in/from the RAM, re-input to the data comparator 124 and adder 125, and output to the external function section via the data controller 122 in accordance with the received data, and a sensitivity setting register 127 for changing control signals to be output from the device controller 121 to the top and bottom gate drivers 111 and 112 so
- FIG. 3 is a flow chart showing an operation executed up to the optimal image reading sensitivity setting
- FIG. 4 shows a specific row section of a photosensor array for which the sensitivity-adjusting reading operation is performed according to this embodiment, the specific row being illustrated in relation to a subject image. This operation will be described by properly referring to the arrangement of the photosensor system shown in FIGS. 1 and 2.
- Sil sensitivity-adjusting reading operation
- the main controller 123 controls to set an image reading sensitivity for sensitivity-adjusting reading operation in the sensitivity setting register 127 via the data controller 122, and executes the sensitivity-adjusting reading operation of reading a subject image at a plurality of different sensitivities while changing the image reading sensitivity stepwise for respective specific row sections of the subject image. These operations are executed prior to the normal reading operation of the subject image, for example.
- the sensitivity- adjusting reading operation applicable to the sensitivity adjusting method of the first embodiment is performed, using a photosensor array 100 in which photosensors are arranged in units of a matrix pattern of 256 rows x 196 columns, as shown in FIG. 4.
- a central row i.e., the n/2-th row
- the photosensors 10 corresponding to the specific row section are reset.
- precharge operation and readout operation are repeatedly executed at predetermined timings in such a manner that the charge accumulating period (image reading sensitivity) varies stepwise.
- the image reading sensitivity is made to vary in correspondence to the number of times reading operation is executed.
- Data are stored in a RAM 130 , for example, in a table format of (the number of times of reading operation) vs (image reading sensitivity correspondence table) . A specific method for setting the image reading sensitivity will be described later.
- S12 image data conversion step
- the image data read by the sensitivity-adjusting reading operation are converted into digital signals via an amplifier 116 and an A/D converter 117.
- the digital signal is supplied to a data comparator 124 of the controller 120 as lightness data corresponding to the bright/dark pattern of the subject image.
- the lightness data are expressed by, e.g., 256 gray levels.
- the image data corresponding to each reading operation are converted into a lightness data value in the range of 0 to 255 and stored in the data comparator 124.
- FIGS. 5A to 5E A specific example is shown in FIGS. 5A to 5E.
- FIGS. 5A to 5E show lightness data which are obtained when reading operation has been executed a predetermined number of times in one row of the specific row section, and in which the image reading sensitivity increases with an increase in the number of times reading operation is executed.
- FIGS. 5A to 5E show how lightness data change in the columns when reading operation has been executed 16 times (FIG. 5A) , 32 times (FIG. 5B) , 64 times (FIG. 5C) , 96 times (FIG. 5D) and 128 times (FIG. 5E) .
- the lightness data obtained when the reading operation has been executed 16 times and 32 times are data wherein the image reading sensitivity is low.
- the lightness data value indicating a maximum value i.e., the gray level of the brightest pixel
- the lightness data value indicating a minimum value i.e., the gray level of the darkest pixel
- the adder 125 calculates the difference between the maximum and minimum values of lightness data in relation to the number of times reading operation is executed as a dynamic range.
- the result of this calculation is stored in the RAM 130 through the use of the data selector 126.
- This dynamic range calculation step is executed each time reading operation is performed.
- the data selector 126 reads out dynamic ranges of reading operations from the RAM 130 in relation to the number of times reading operation is executed, and the readout dynamic ranges are supplied to the data comparator 124.
- the dynamic range changing tendency FIG. 6
- a maximum value DLmax of the dynamic range is determined in relation to the number of times a reading operation is executed, and the number RCa of times corresponding to the determined maximum value is extracted.
- the lightness data obtained in the 64th reading operation does not have a value that is saturated at the upper or lower limit.
- the dynamic range of the lightness data obtained in the 64th reading operation is greater than the dynamic ranges of the other lightness data.
- the maximum value is DLmax
- the number RCa of the reading operation corresponding to that maximum value is 64.
- the image reading sensitivity (i.e., the charge accumulating period) corresponding to the number RCa of the reading operation is extracted by referring to the table stored in the RAM 130, i.e., the table of [the number RCa of times of reading operation] vs [image reading sensitivity correspondence table] .
- the main controller 123 causes the data controller 122 to rewrite the data in the sensitivity setting register 127, so that the image reading sensitivity of the sensitivity setting register 127 is set at the extracted image reading sensitivity. This brings an end to the optimal image reading sensitivity setting based on the sensitivity-adjusting reading operation.
- the sensitivity-adjusting reading operation (which repeatedly reads a subject image at predetermined intervals) is executed in the selected specific row section after resetting operation.
- the subject image can be read, with the image reading sensitivity (charge accumulating period) being varied stepwise.
- the time needed for the sensitivity-adjusting reading operation can be as short as possible.
- the first embodiment uses image data corresponding to one or several specific rows (specific row section) .
- image data corresponding to one or several specific rows specifically row section.
- the amount of data used for the extraction of an optimal image reading sensitivity can be significantly reduced, resulting in a remarkable decrease in the processing load.
- the time needed for the setting of an optimal image reading sensitivity can be significantly shortened.
- the sensitivity-adjusting reading operation is limited to the specific row section.
- the first embodiment has significantly lowered the probability of inclusion of an abnormal pixel (a missing point or a twinkling point) , which may be caused by a foreign substance adhering to a target area, a defective element of a photosensor, or the like.
- an abnormal pixel a missing point or a twinkling point
- the first embodiment has significantly lowered the probability of inclusion of an abnormal pixel (a missing point or a twinkling point) , which may be caused by a foreign substance adhering to a target area, a defective element of a photosensor, or the like.
- an abnormal pixel a missing point or a twinkling point
- the specific row section may be selected from any area as long as that area shows a clear brightness pattern (contrast) of a subject image.
- the specific row section may be those located near the central row, or may be selected from another area.
- the sensitivity-adjusting reading operation is executed for one or several rows of the specific row section. This significantly reduces the probability that an abnormal pixel exits in the target specific row section in comparison with the case where the entire light- receiving area of a photosensor array or a selected area thereof is subjected to the reading operation. However, the probability that an abnormal pixel exists in the specific row section is in no way "zero.”
- the second embodiment is intended to reliably prevent the adverse effects an abnormal pixel may have when the sensitivity-adjusting reading operation is performed for one or several rows of the specific row section.
- the controller applied to the second embodiment is similar in structure to the controller 120 employed in the first embodiment and is represented by the structural blocks shown in FIG. 2.
- FIG. 7 is a flowchart illustrating how the controller 120 controls the operation of the photosensor system in the second embodiment of the present invention.
- the operations executed up to the optimal image reading sensitivity setting are illustrated.
- FIG. 8 shows a specific row section of the photosensor array for which the sensitivity-adjusting reading operation is performed according to the second embodiment, the specific row section being illustrated as Rp in relation to a subject image.
- Rp the specific row section
- the sensitivity-adjusting reading operation applied to the sensitivity adjusting method of the second embodiment is executed for a specific row section Rp of a photosensor array 100 in which photosensors are arranged in units of a matrix pattern of 256 rows x 196 columns, as shown in FIG. 8.
- Step S21 (sensitivity-adjusting reading operation) of FIG. 7 is executed in a similar manner to that of Sil of the first embodiment.
- the photosensors corresponding to the specific row section Rp of the photosensor array 100 shown in FIG. 8 are controlled in such a manner that the charge accumulating period (i.e., the image reading sensitivity) varies stepwise at predetermined intervals.
- the sensitivity-adjusting reading operation is performed for a subject image at a plurality of image reading sensitivities, which correspond to the number of times reading operation has been executed. These operations are executed prior to the normal reading of the subject image.
- Step S22 image data conversion step of FIG. 7, is executed in a similar manner to that of S12 of the first embodiment.
- the image data read by the sensitivity-adjusting reading operation are converted into lightness data.
- the lightness data are supplied to the controller 120 and stored in the RAM 130.
- FIGS. 9A to 9E A specific example is shown in FIGS. 9A to 9E. Like FIGS. 5A to 5E, FIGS. 9A to 9E show how lightness data change in the columns when reading operation has been executed 16 times (FIG. 9A) , 32 times (FIG. 9B) ,
- the lightness data include the lightness data which represent the minimum value "zero" at the number Lq of column by the abnormal pixel IL shown in FIG. 8.
- the lightness data obtained when the reading operation has been executed 16 times and 32 times are data wherein the image reading sensitivity is low. Since the sensitivity is thus insufficient, there are columns in which the data value is "0" (lower limit) .
- the lightness data obtained when the reading operation has been executed 96 times and 128 times are data wherein the image reading sensitivity is high.
- step S23 (the step of extracting and comparing the same-column data from the data of each reading operation) shown in FIG. 7 is executed.
- the data selector 126 extracts lightness data of the same column from the lightness data stored in the RAM 130 and corresponding to each reading operation.
- the extracted lightness data are supplied to the data comparator 124 so as to compare the lightness data of the same column.
- step S24 (the step of determining a variation in the same-column data) shown in FIG. 7 is executed. This step is for determining whether there is a column in which the lightness data remain the same after each reading operation.
- the pixels corresponding to this column are regarded as abnormal ones, and the specific row section for which the sensitivity-adjusting reading operation is performed is determined as containing an abnormal pixel.
- the specific row section for which the sensitivity-adjusting reading operation is performed is determined as not containing an abnormal pixel .
- a result of this determination is supplied from the data comparator 124 to the main controller 123.
- the abnormal pixel IL is present, and the lightness data corresponding to column number Lq are "0" irrespective of the number of times reading operation is executed.
- the sensitivity- adjusting reading operation may be controlled as follows: Flags are set for the respective columns on the basis of the lightness data on the columns obtained by the first-time reading operation. The light data obtained by subsequent reading operations are compared with the lightness data obtained by the first-time reading operation. This comparison is executed for each of the columns. If the lightness data on a column differ from the original lightness data, the flag corresponding to that column is reset. As long as a pixel is normal, the lightness data on the pixel vary in accordance with a change in the image reading sensitivity.
- the flag of the pixel is reset.
- the pixel if the pixel is abnormal, the lightness data on the column containing the abnormal pixel do not vary even when the image reading sensitivity changes.
- the value of the lightness data is an upper-limit value, a lower-limit value or a constant in between, for example.
- the flag continues to be in the set state.
- an abnormal pixel present in a specific row section for which the sensitivity-adjusting reading operation is to be executed can be detected by monitoring the states of the flags.
- step S24 determines that an abnormal pixel exists
- step S25 the step of changing the specific row section for which the sensitivity-adjusting reading operation shown in FIG. 7 is executed.
- the main controller 123 causes the device controller 121 to change the specific row section for which the sensitivity-adjusting reading operation is to be executed.
- the operations starting from S21 are executed again. It is only required that the specific row section for which the sensitivity-adjusting reading operation is newly executed be a another specific row section other than the specific row section where the abnormal pixel IL is detected.
- the another specific row section may be the one that is adjacent to row Rp in the upper or lower area, or may be the one that is away from that row section by a predetermined number of rows.
- the processing in steps S21-S24 is repeatedly executed until the specific row section for which the sensitivity-adjusting reading operation is to be executed is determined as not containing an abnormal pixel.
- step S24 determines that an abnormal pixel does not exist in the specific row section for which the sensitivity-adjusting reading operation is to be executed
- step S26 the step of extracting a maximum value and a minimum value in each reading operation shown in FIG. 7 is executed.
- maximum and minimum values are extracted from the lightness data obtained in each reading operation and supplied to the data comparator 124, and output to the adder 125, as in step S13 of the first embodiment.
- step S27 the step of calculating a dynamic range in each reading operation
- step S28 the step of extracting a reading operation that exhibits a maximum dynamic range
- step S29 the step of referring to and extracting a sensitivity
- step S30 the step of setting the extracted sensitivity shown in FIG. 7 are sequentially executed.
- steps S14 to S17 of the first embodiment described above That is, the dynamic range of the lightness data obtained in each reading operation is calculated by the adder, and then the data comparator 124 checks the dynamic range changing tendency (FIG. 31) relative to the number of times a reading operation is executed, and detects the reading operation in which the dynamic range is maximal.
- the image reading sensitivity (the charge accumulating period) corresponding to this reading operation is det in the sensitivity setting register 127, thereby bringing an end to the optimal image reading sensitivity setting based on the sensitivity-adjusting reading operation.
- the sensitivity setting method of the second embodiment if an abnormal pixel, which is due to a foreign substance adhering to the sensing surface of the photosensor array, any defective element of the photosensor, or the like, is present in the specific row section for which the sensitivity-adjusting reading operation is to be executed, such an abnormal pixel can be easily detected. Based on this detection, the sensitivity-adjusting reading operation is executed for another specific row section where no abnormal pixel exists.
- an optimal image reading sensitivity is unconditionally determined on the basis of the dynamic range of light data acquired by the sensitivity-adjusting reading operation. Therefore, even when the sensitivity-adjusting reading operation is to be executed for a specific row section different from the originally selected specific row section, the image reading sensitivity is kept optimal. Normal reading operation for a subject image can be executed in a reliable manner irrespective of the ambient conditions, such as the illuminated state of the environment. Accordingly, a malfunction is prevented in fingerprint recognition processing or the like.
- the specific row section for which the sensitivity-adjusting reading operation is to be executed is predetermined, for example, in the center of the photosensor. The present invention is not limited to this. That is, the specific row section need not be designated beforehand.
- the entire area of a subject image or a predetermined area thereof may be read at an arbitrary image reading sensitivity.
- a specific row section or an area most suitable for image reading is extracted, and one specific row section or several specific row sections may be determined on the basis of the extracted data.
- FIGS. 10A to 10L are timing charts illustrating an embodiment of the sensitivity-adjusting reading operation, which is applicable to the sensitivity- adjusting reading operation of the first and second embodiments.
- the one specific row section for which the sensitivity-adjusting reading operation is to be executed is a row located in the center. As shown in FIGS.
- the image reading sensitivity setting method of the embodiment initializes only the double-gate photosensors of a central row (n/2n-th row), i.e., a specific row, of the photosensor array shown in FIG. 12. More specifically, waves ⁇ Ti to ⁇ Tn/2-1 and ⁇ Tn/2+1 to ⁇ Tn applied to the first to (n/2-l)-th rows and (n/2+l)-th to n-th rows, which are among the top gate lines 101 connected to the top gate terminals TG of the double-gate photosensors 10 in the row direction, are set at a low level, and a single reset pulse ⁇ Tn/2 is applied only to the n/2-th row.
- the reset period 'T ' reset is started, and only the double-gate photosensors 10 of the (n/2)-th row are initialized. Then, the reset pulse ⁇ Tn/2 falls and the reset period T rese -t- ends. Thereafter, the charge accumulating period starts, and charges (holes) are generated and accumulated in the channel regions in accordance with the amount of light entering the double-gate photosensors 10 of the n/2-th row from their top gate terminal (21) side.
- precharge signal ⁇ pg and readout pulse ⁇ Bn/2 which is predetermined for the bottom gate lines 102 of the n/2-th row, are alternately applied at predetermined intervals Tint a number of times (x times, x: an integer larger than 1) .
- Waves ⁇ Bi to ⁇ Bn/2-1 and ⁇ Bn/2+1 to ⁇ Bn applied to the bottom gate lines 102 of the first to (n/2-l)-th rows and (n/2+l)-th to n-th rows are set at a low level.
- drain voltages VDl, VD2, ••• , VDm varying in correspondence to the charge accumulated in the charge accumulating periods TB1, TB2, ••• , TBx, which are between the end of the reset period T j -ggg ⁇ and the start of the readout time ⁇ read (i-e., the application of the readout pulses ⁇ Bn/2), are sequentially read out.
- the charge accumulating period of a specific row section increases stepwise at predetermined time intervals Tint.
- image data is read from a subject image, with the image corresponding to the specific row section being read at a plurality of different image reading sensitivities.
- the photosensors corresponding to one specific row section are reset at a time, and reading operation is repeatedly executed with respect to them.
- the amount of charge accumulated in each photosensor may be varied by the readout operation.
- the charge accumulating period of each reading operation may be corrected in accordance with an actual charge accumulating period on the basis of the correspondence between the number of times reading operation is performed and the amount of charge accumulated.
- sensitivity- adjusting reading operation is executed with respect to a subject image while simultaneously changing the image reading sensitivity stepwise.
- an image reading sensitivity which ensures an optimal image reading state is determined easily.
- This image reading sensitivity charge accumulating period
- the sensitivity setting processing can be executed using an actual subject, it is not necessary to use a standard sample or the like. Even when the lightness of the subject image varies in response to changes in the environment light, an optimal image reading sensitivity can be set in accordance with the changes in the environmental light.
- the image reading sensitivity can be set at an optimal value without being adversely affected by an abnormal pixel, which is due to a foreign substance adhering to the sensing surface of the photosensor array, a defect of the photosensor element, or the like.
- the sensitivity-adjusting reading operation is executed prior to the normal reading operation.
- the present invention is not limited to this.
- the sensitivity-adjusting reading operation may be executed in the standby state, i.e., the state where the photosensor system is operating but a subject has not yet been placed.
- the sensitivity-adjusting reading operation was described as being performed whenever the normal reading operation is executed for a subject image.
- the present invention is not limited to this.
- the sensitivity-adjusting reading operation may be performed only when there is a change in the use environment, or when a predetermined length of time has elapsed.
- the image reading sensitivity (charge accumulating period) setting method applied to sensitivity setting processing according to the present invention is not limited to the above embodiments.
- image data of a subject image can be obtained at different reading sensitivities, e.g., a series of processes described in the prior art: reset operation ⁇ charge accumulating operation ⁇ pre-charge operation —* readout operation can be repeated a plurality of number of times at different reading sensitivities, thereby obtaining image data at different reading sensitivities.
- any other methods may also be employed.
Landscapes
- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Solid State Image Pick-Up Elements (AREA)
- Facsimile Heads (AREA)
- Transforming Light Signals Into Electric Signals (AREA)
- Thin Film Transistor (AREA)
- Image Input (AREA)
- Facsimile Scanning Arrangements (AREA)
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP01978928A EP1402721A1 (en) | 2001-06-29 | 2001-10-26 | Photosensor system and drive control method thereof |
KR10-2002-7016162A KR100526297B1 (en) | 2001-06-29 | 2001-10-26 | Photosensor system and drive control method thereof |
CA002426388A CA2426388C (en) | 2001-06-29 | 2001-10-26 | Photosensor system and drive control method thereof |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2001198615A JP4081641B2 (en) | 2001-06-29 | 2001-06-29 | Sensitivity adjustment apparatus for two-dimensional image reading apparatus and sensitivity adjustment method thereof |
JP2001-198615 | 2001-06-29 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2003003719A1 true WO2003003719A1 (en) | 2003-01-09 |
Family
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2001/009438 WO2003003719A1 (en) | 2001-06-29 | 2001-10-26 | Photosensor system and drive control method thereof |
Country Status (7)
Country | Link |
---|---|
EP (1) | EP1402721A1 (en) |
JP (1) | JP4081641B2 (en) |
KR (1) | KR100526297B1 (en) |
CN (1) | CN1312906C (en) |
CA (1) | CA2426388C (en) |
TW (1) | TW516227B (en) |
WO (1) | WO2003003719A1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7787039B2 (en) | 2000-05-26 | 2010-08-31 | Semiconductor Energy Laboratory Co., Ltd. | MOS sensor and drive method thereof |
CN109102769A (en) * | 2017-06-21 | 2018-12-28 | 三星显示有限公司 | Method for operating display device |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP4373872B2 (en) * | 2004-07-30 | 2009-11-25 | 浜松ホトニクス株式会社 | Imaging apparatus and microscope apparatus using the same |
JP5866089B2 (en) * | 2009-11-20 | 2016-02-17 | 株式会社半導体エネルギー研究所 | Electronics |
DE102015219496A1 (en) * | 2015-10-08 | 2017-04-13 | Robert Bosch Gmbh | Method for determining the functionality of a driver assistance system of a vehicle, device, driver assistance system, motor vehicle |
CN109104579B (en) * | 2018-09-30 | 2020-11-13 | 易诚高科(大连)科技有限公司 | Automatic evaluation and adjustment method for photographing environment in image quality evaluation process |
CN111307375B (en) * | 2018-12-11 | 2022-05-03 | 贵州中烟工业有限责任公司 | Method, device and equipment for judging cigarette leakage detector rejection function |
CN109901333B (en) * | 2019-02-26 | 2021-11-30 | 江西合力泰科技有限公司 | Solar charging method for mobile phone based on solar liquid crystal display screen |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2001035638A1 (en) * | 1999-11-08 | 2001-05-17 | Casio Computer Co., Ltd. | Photosensor system and drive control method thereof |
WO2001035637A1 (en) * | 1999-11-10 | 2001-05-17 | Casio Computer Co., Ltd. | Photosensor system and drive control method thereof |
-
2001
- 2001-06-29 JP JP2001198615A patent/JP4081641B2/en not_active Expired - Fee Related
- 2001-10-26 WO PCT/JP2001/009438 patent/WO2003003719A1/en not_active Application Discontinuation
- 2001-10-26 CN CNB018110894A patent/CN1312906C/en not_active Expired - Fee Related
- 2001-10-26 KR KR10-2002-7016162A patent/KR100526297B1/en not_active IP Right Cessation
- 2001-10-26 CA CA002426388A patent/CA2426388C/en not_active Expired - Fee Related
- 2001-10-26 EP EP01978928A patent/EP1402721A1/en not_active Withdrawn
- 2001-10-30 TW TW090126913A patent/TW516227B/en not_active IP Right Cessation
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2001035638A1 (en) * | 1999-11-08 | 2001-05-17 | Casio Computer Co., Ltd. | Photosensor system and drive control method thereof |
WO2001035637A1 (en) * | 1999-11-10 | 2001-05-17 | Casio Computer Co., Ltd. | Photosensor system and drive control method thereof |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7787039B2 (en) | 2000-05-26 | 2010-08-31 | Semiconductor Energy Laboratory Co., Ltd. | MOS sensor and drive method thereof |
US8164652B2 (en) | 2000-05-26 | 2012-04-24 | Semiconductor Energy Laboratory Co., Ltd. | MOS sensor and drive method thereof |
CN109102769A (en) * | 2017-06-21 | 2018-12-28 | 三星显示有限公司 | Method for operating display device |
Also Published As
Publication number | Publication date |
---|---|
KR100526297B1 (en) | 2005-11-08 |
TW516227B (en) | 2003-01-01 |
KR20030055179A (en) | 2003-07-02 |
JP2003018474A (en) | 2003-01-17 |
CN1312906C (en) | 2007-04-25 |
CA2426388C (en) | 2005-12-06 |
JP4081641B2 (en) | 2008-04-30 |
EP1402721A1 (en) | 2004-03-31 |
CA2426388A1 (en) | 2003-01-09 |
CN1442018A (en) | 2003-09-10 |
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