JP2004128716A - Solid-state imaging apparatus and image correction circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress production of a linear flaw due to a step difference at joints of images by an amplitude waveform distortion caused at joints of divided image areas. <P>SOLUTION: A solid-state imaging apparatus having a plurality of pixel division areas and a means for reading pixel signals transferred through electric charge transmission paths provided for the every pixel division area, includes: white level signal detection means 21, 22, 28, 29 for using a signal value in a shade state during a one-unit read period in each of the pixel division areas for a reference signal and detecting a white level signal obtained by measuring a white chart; correction circuits 23, 30 for correcting an image signal when the white level signals detected by the white level signal means are close to each other at a plurality of points of time during the one-unit read period; and an image compositing circuit for compositing the images of the pixel division areas on the basis of the image signal after the correction. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a solid-state imaging device having a unit that divides an image region into a plurality of regions and reads out pixel signals for each of the divided image regions, and particularly to an image correction circuit of the solid-state imaging device.
[0002]
[Prior art]
Conventionally, for a digital still camera or a digital video camera, a CCD solid-state imaging device having one horizontal transfer CCD and one output terminal has been used. If a large number of vertical CCDs are connected to one horizontal CCD as the number of pixels in the CCD solid-state imaging device increases, the readout frequency must be increased. For example, in a digital video camera having 680,000 pixels, the read frequency is generally about 27 MHz. If the number of pixels is increased to about 2 million pixels, the operating frequency must theoretically be increased to, for example, about 72 MHz, but it is practically difficult to increase the operating frequency to 72 MHZ. Therefore, the signal of the previous frame remains and is mixed with the signal of the current frame, resulting in a problem that the image quality deteriorates.
[0003]
In order to solve the above problems, the image area of the CCD solid-state imaging device is divided into a plurality of areas, each of which is provided with a horizontal transfer CCD and an output amplifier, and reads out image data in parallel in the plurality of areas. Imaging devices have also been developed.
[0004]
The configuration of the split solid-state imaging device will be described with reference to FIG. The divided solid-state imaging device illustrated in FIG. 1 includes a unit that divides a pixel region into a plurality of regions (two regions in the drawing) and reads pixel signals for each region. More specifically, the pixel signals in the two divided areas are transferred by the two horizontal transfer CCDs 4 and 5, and output to the signal processing circuits 11 and 12. The signals processed in the signal processing circuits 11 and 12 are combined into one continuous image by the combining circuit 13.
[0005]
FIG. 8 is a functional block diagram showing a configuration example of a single-panel video camera using the above-mentioned split type solid-state imaging device. A subject image is formed on the imaging surface (strictly, photodiode 2 (FIG. 1)) of the CCD solid-state imaging device 111 through the lens. In the solid-state imaging device 1 (FIG. 1), the subject image is formed for each pixel (photodiode). An electric signal is obtained by photoelectric conversion.
[0006]
An output signal from the solid-state imaging device 1 is output to the outside through amplifiers 6 and 7 (FIG. 1) in units of left and right image areas sharing the horizontal CCD 4 or 5 (FIG. 1). The horizontal transfer CCD 4 and the horizontal transfer CCD 5 operate simultaneously, and the left and right image data are output simultaneously. The image data in the left and right image areas is converted into digital data by two sets of CDS circuits 112 and 113 and AD converters 112 and 113 and input to the signal processing circuit 120. The signal processing circuit 120 performs a process of correcting the right image data and the left image data output from the AD converters 112 and 113 by the correction circuits 114 and 115. The image data of the left and right image areas, which have been separately corrected, are connected by the synthesizing circuit 116 and recombined into one piece of image data, and the image signal output S2 is output.
[0007]
FIG. 9 is a diagram illustrating the operation of the synthesis circuit. In the horizontal scanning period 121 in FIG. 9, right image data and left image data are input at timings 122 and 123 in FIG. The synthesizing circuit 116 (FIG. 8) outputs the left image data at the timing of the synthesizing circuit output 124 in the same order as the input order. Thereafter, by outputting the right image data in the reverse order of the input order at the timing of the synthesizing circuit output 125, image data of two horizontal screens can be synthesized into one screen.
[0008]
That is, when the pixels of the right image data are input in the order of R1,... Rn, and the pixels of the left image data are input in the order of L1... Ln, the output of the synthesizing circuit 116 becomes an arrangement of L1. Is output.
[0009]
[Problems to be solved by the invention]
Here, the image data is connected by the synthesizing circuit 116 in FIG. 8 to synthesize one piece of image data. The image data of the left and right areas is processed by signal processing via separate horizontal transfer CCDs 4 and 5 (FIG. 1), output amplifiers 6 and 7 (FIG. 1) of the CCD solid-state imaging device, CDS circuits, AD converters 112 and 113, respectively. The amplitude difference between the image data in the left and right regions occurs due to variations in the gains of these circuits. An image correction circuit shown in FIG. 10 is provided to remove the influence of the difference in amplitude.
[0010]
The image correction circuit shown in FIG. 10 captures a white chart so that uniform light is incident on the imaging surface of the CCD solid-state imaging device, and the amplitudes of the left and right image data signals at that time are detected by the white level detection circuits 201 and 205. measure. The correction values are calculated by the correction value calculation circuits 202 and 206 so that the measured amplitudes of the left and right image data signals coincide with each other, and are set in the registers 203 and 207. The correction values of the registers 203 and 207 are multiplied by the original left and right image data by the multiplication circuits 204 and 208, and left and right image data having the same amplitude are output.
[0011]
In the horizontal transfer CCD, a difference in signal amplitude occurs between the pixel data at the start of CCD reading and the pixel data at the end of reading due to the influence of the transfer efficiency of each CCD stage. Further, each element of the CCD image pickup device, the CDS circuit, and the AD converter is subjected to sag-like amplitude distortion due to fluctuations in the power supply voltage or the like. The distortion with respect to the amplitude generated in each of these elements is proportional to the amplitude of the image data.
[0012]
As shown in FIG. 11, when the images 211 of the left and right regions subjected to the waveform distortion are connected as they are, as indicated by reference numeral 212, a V-shaped signal step centering on the connected portion of the left and right region images 211 is formed. appear. When a luminance signal is created based on the image data in a state where the V-shaped step has occurred, the luminance signal circuit generates a horizontal edge (H-DTL) signal as indicated by 213, and this signal is added to the luminance signal. This causes a problem that a vertical streak occurs in the center.
[0013]
On the other hand, the image data of the left and right regions are input to the signal processing circuit via separate horizontal transfer CCDs, output amplifiers of the CCD image pickup device, CDS circuits, and AD converters. Then, a step occurs in the black level between the image data in the left and right regions. In order to eliminate this step, an image correction circuit shown in FIG. 12 is provided.
[0014]
As shown in FIG. 12, the DUM detection circuits 301 and 305 measure the amplitudes of the dummy pixel regions located downstream of the left and right image data Din (L) and Din (R), respectively. In the measured left and right image data, the correction values are calculated by the correction value calculation circuits 300 and 302 so that the amplitude values of the dummy pixel areas match. This correction value (correction coefficient) is set in the registers 304 and 308. The correction values set in the registers 304 and 308 are added to the left and right image data by the addition circuits 303 and 307, and the left and right image data without a step is output.
[0015]
Here, when the image data is connected by the synthesizing circuit and synthesized into one image data, the image data in the left and right image areas is converted into separate horizontal transfer CCDs, output amplifiers of CCD image sensors, CDS circuits, and AD converters. The signal is input to the signal processing circuit. The image data in the left and right pixel regions undergo waveform distortion due to the above-described elements. In the horizontal transfer CCD, a difference in signal amplitude occurs between pixel data at the start of CCD reading and pixel data at the end of reading depending on the transfer efficiency of each CCD stage. In addition, each element of the CCD image pickup device, the CDS circuit, and the AD converter receives a sag-like amplitude distortion due to a change in the power supply voltage.
[0016]
As shown in FIG. 13, when the image signals in the left and right pixel regions 401 subjected to the waveform distortion are connected as they are, the image data in the light-shielded state is connected as shown by a reference numeral 402. A V-shaped signal step occurs at the center. When a luminance signal is generated based on the image data in a state where the V-shaped step occurs, a horizontal edge signal indicated by reference numeral 403 is easily generated, and this edge signal is added to the luminance signal, and the center of the output luminance signal is generated. This causes a problem that vertical streaks occur. Since this step is a step at the black reference level in the light-shielded state, it occurs regardless of the conditions of the image being captured.
SUMMARY OF THE INVENTION It is an object of the present invention to prevent image degradation near a joint which occurs when pixel data of a divided image area is combined.
[0017]
[Means for Solving the Problems]
In order to solve this problem, the present invention provides an image correction circuit used in a video camera using a CCD image pickup device having means for dividing an image area into two right and left parts and reading out pixel signals for each area. , Means for detecting the amplitude of two image areas, means for calculating a correction value, means for generating a sawtooth wave signal, and means for adjusting the amplitude of the sawtooth wave signal. By providing an image correction circuit, it is proposed to eliminate vertical stripes generated at the center and to suppress deterioration of image quality.
[0018]
That is, according to one aspect of the present invention, a solid-state imaging device including: a plurality of divided pixel regions; and a unit that reads a pixel signal transferred by a charge transfer path provided for each of the divided pixel regions. Detecting a characteristic value of an image signal during one unit readout period in each of the divided pixel regions and correcting the characteristic values of the pixel signal at a plurality of time points during the one unit readout period so as to approach each other. A solid-state imaging device provided with a correction circuit that performs the correction.
[0019]
In the solid-state imaging device, by focusing on a certain characteristic value and correcting the characteristic value so as not to change with time, a step at a boundary break when a signal in a plurality of divided pixel regions is combined is calculated. Can be reduced.
[0020]
The characteristic value is preferably a white level signal obtained by measuring a white chart using the signal value in the light-shielded state as a reference signal. Since the detection of the white level is easy, the correction can be easily performed.
[0021]
According to another aspect of the present invention, there is provided a solid-state imaging device including: a plurality of divided pixel regions; and a unit that reads a pixel signal transferred by a charge transfer path provided for each of the divided pixel regions. And a white level signal detecting means for detecting a white level signal obtained by measuring a white chart with a signal value in a light-shielded state as a reference signal during one unit readout period in each of the divided pixel regions, A correction circuit that corrects an image signal so that white level signals detected by the white level signal unit approach at a plurality of times during the one-unit readout period; and an image signal obtained by correcting a screen of the divided pixel region. A solid-state imaging device having a screen composition circuit for performing composition based on the image data can be provided.
[0022]
The correction circuit generates a compensation signal having a multiplied value for compensating the difference based on a difference between the white level signals detected at a plurality of times during the one-unit readout period, and the compensation signal and a signal before correction. And a circuit for multiplying by.
[0023]
The compensation signal is preferably a sawtooth signal having a slope opposite to the slope of the amplitude of the white level signal before correction. With the above configuration, the correction can be performed by a simple method.
[0024]
Further, according to the present invention, there is provided an image correction circuit used in a video camera using a CCD image pickup device having a means for dividing an image area into two right and left parts and reading out pixel signals for each area, wherein the image correction means for left and right image data is provided. Means for detecting an optical black signal value of CCD pixel data, means for detecting a signal value of a non-feed portion, means for detecting a black level of an image area at two light-shielded positions, and calculating a correction value Means, a sawtooth wave signal generating means, a means for adjusting the amplitude of the sawtooth wave signal, a means for adding a set value, and an image correcting circuit having an adding means for image data. It is proposed to eliminate vertical streaks occurring at the center and to suppress image quality deterioration.
[0025]
According to another aspect of the present invention, a pixel region including a plurality of divided pixel regions, each including a light-shielded pixel in a light-shielded state on the pixel region surface for obtaining a black-level reference signal, Means for reading a pixel signal transferred by a charge transfer path provided for each of the divided pixel regions, wherein the pixel signal is transferred during one unit readout period in each of the divided pixel regions. The amplitude of the signal during the one-unit readout period based on a plurality of black level signals measured in advance based on the image signal of the light-shielded pixel and at least one of the empty readout signals before and after the one-unit readout period. And a solid-state imaging device including a correction circuit that corrects the values to be equal.
[0026]
Preferably, the black level signals are first and second at least two black level signals measured in a state where the entire pixel region surface is shielded from light (when an iris is closed). One of the first black level signal and the second black level signal is temporally close to the pixel signal of the light-shielded pixel, and the other is a position temporally close to the empty readout signal. It is preferable that the measured signal is a signal measured in the above step.
[0027]
According to the solid-state imaging device, a plurality of black level signals are measured in advance, and the relevance of each black level signal to the image signal of the light-shielded pixel and at least one of the empty readout signals before and after the one-unit readout period is determined. In order to correct the image data using the height, to estimate the black level signal value that cannot be measured during operation, and to correct based on the estimated value so that the signal amplitude during the unit readout period becomes equal. , Accurate correction can be performed.
[0028]
According to still another aspect of the present invention, a pixel region including a plurality of divided pixel regions, each including a light-shielded pixel in a light-shielded state on the pixel region surface for obtaining a black-level reference signal. Means for reading a pixel signal transferred by a charge transfer path provided for each of the divided pixel regions, wherein the image signal of the light-shielded pixel in each of the divided pixel regions is provided. An optical black signal detection circuit, a dummy pixel data detection circuit for detecting an empty read signal, a black level detection circuit for detecting a plurality of black level signals, the optical black signal detection circuit, and the dummy pixel data detection A correction value based on the circuit and the black level detection circuit for making the amplitudes of the signals during the one-unit readout period equal. The solid-state imaging device that includes a Mel correction value calculation circuit is provided.
[0029]
Further, based on the values detected by the dummy pixel data detection circuit and the optical black signal detection circuit, black level signal values close to each other are estimated, and the amplitude of the signal is estimated based on the estimated black level signal. It is preferable to obtain a slope and add a compensation wave for compensating the slope to be flat and the original pixel data. Further, it is preferable that the compensation wave is a sawtooth wave having a reverse slope of the amplitude of the signal based on the black level signal.
[0030]
In addition, a pixel region including a plurality of divided pixel regions, each including a light-shielded pixel that is in a light-shielded state on the pixel region surface for obtaining a black-level reference signal, and each of the divided pixel regions. Means for reading out a pixel signal transferred by the provided charge transfer path, and an optical black signal detection circuit provided in the solid-state imaging device, the circuit detecting an image signal of the light-shielded pixel in each of the divided pixel regions. A dummy pixel data detection circuit that detects an empty read signal, a black level detection circuit that detects a plurality of black level signals, the optical black signal detection circuit, the dummy pixel data detection circuit, and the black level detection circuit. And a correction value calculation circuit for obtaining a correction value for making the amplitudes of the signals during the one-unit readout period equal based on Image correction circuit is provided.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a solid-state imaging device according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of a solid-state imaging device according to a first embodiment of the present invention. FIG. 2A is a functional block diagram illustrating a schematic configuration of the solid-state imaging device according to the first embodiment of the present invention. FIG. FIG. 2B is a functional block diagram illustrating a configuration example of a correction circuit included in the signal processing circuit of the solid-state imaging device illustrated in FIG.
[0032]
As shown in FIG. 1, the solid-state imaging device according to the present embodiment is a CCD solid-state imaging device (used in a single-panel video camera) having a means for dividing an image area into a plurality of parts and reading out pixel signals for each of the divided image areas. ). An example will be described in which a CCD solid-state imaging device of a type in which a signal is read out by dividing the signal into two right and left parts is used.
[0033]
As shown in FIG. 1, there is provided a means for dividing a pixel region into a plurality of regions and reading out pixel signals for each region. More specifically, a subject image is formed and incident on a photo diode (photoelectric conversion element) 2 arranged in a matrix on the imaging surface of the CCD solid-state imaging device 1 through a micro lens, and the subject image is Is converted into an electric signal. The converted electric signal enters the vertical charge transfer path (VCCD) 3 and is transferred by the drive circuit toward the horizontal charge transfer path (HCCD). The pixel signals in the two divided areas are transferred to the two HCCDs 4.5 in the direction of the amplifiers 6 and 7 by the driving circuit, and the amplified image signals are transferred to the signal processing circuit 11.・ Output to 12. The signals processed in the signal processing circuits 11 and 12 are combined into one continuous image by the combining circuit 13. As the output of the solid-state imaging device 1, an image data signal is output for each of the left and right image areas.
[0034]
As shown in FIG. 2A, the image data obtained by the left and right regions of the CCD solid-state imaging device 51 is converted into digital data by two sets of CDS circuits and AD converters 52 and 53, and is converted by the signal processing circuit 60 into digital data. Is entered. In the signal processing circuit 60, each of the left and right image data output from the AD converter is input to the correction circuit 54 and subjected to signal correction processing, and then output to the image synthesis circuit 55. The two-screen combining circuit 55 combines the left and right image data signals, and outputs the left-right separated image as one image data S1.
[0035]
As shown in FIG. 2B, the correction circuit includes, for example, a non-linear correction circuit, a black level correction circuit, a white level correction circuit, a two-screen synthesis circuit, and a noise correction circuit. Which circuit is included is arbitrary. The solid-state imaging device according to the present embodiment has a white level correction circuit, and mainly the white level correction circuit will be described.
[0036]
FIG. 3 is a functional block diagram showing a configuration of the white level correction circuit according to the first embodiment of the present invention. As shown in FIG. 3, the left and right image data digitally converted by the AD converters 52 and 53 (FIG. 2A) are input to the Din (L) terminal and the Din (R) terminal of the image correction circuit. . The left and right input image data are respectively input to the white level detection circuits (1) 21 and 28 and the white level detection circuits (2) 22 and 29 provided respectively, and the respective data values are measured.
[0037]
The signals from the white level detection circuits (1) 21 and (2) 22 are input to the correction value calculation circuit 23, and the signals from the white level detection circuits (1) 28 and (2) 29 are input to the correction value calculation circuit 30. And calculates a correction value from the measured data value. The sawtooth signal is output by the sawtooth signal generation circuits 24 and 31. The correction values calculated by the correction value calculation circuits 23 and 30 are set in registers 25 and 32, respectively, and the first and second multiplication circuits 26 and 33 multiply the correction value by the sawtooth signal. . The third and fourth multiplication circuits 27 and 34 convert the outputs of the first and second multiplication circuits 26 and 33 and the input image data from the Din (L) terminal and Din (R) terminal of the image correction circuit. The multiplied signals are output from the Dout (L) and Dout (R) terminals.
[0038]
Next, the operation of the white level correction circuit shown in FIG. 3 will be described with reference to FIGS. FIG. 4A is a diagram showing a method of detecting data in each part when a white chart is photographed as a subject, and it is assumed that uniform light is incident on the imaging surface of the CCD solid-state imaging device. Reference numeral 41 in FIG. 4 indicates an image data signal during one horizontal scanning period of left and right image data. Optical black data OB appears first as left and right image output signals from the CCD image sensor, followed by image data.
[0039]
The optical black data OB indicates a signal value in a light-shielded state on the CCD imaging surface, is a data value serving as an actual black reference, and the signal value is fixed to “0”. In each of the detection circuits for white level detection (1) and (2), two data of white level data (1) and white level data (2) in the image data are measured. As indicated by reference numeral 41 in FIG. 4A, image data having an amplitude difference corresponding to the amplitude between the left and right white level detection (1) and the white level detection (2), which are two detection points. , And the measured data has a slope-like signal waveform connecting the measurement data with a straight line. A multiplier coefficient that makes the level difference between the white level (1) and the white level (2) in FIG. 4A equal is obtained. This multiplication coefficient becomes a signal corresponding to the signal waveform of the sawtooth wave as shown in FIG. This signal waveform is generated by the circuits denoted by reference numerals 24, 25, and 26 and the reference numerals 31, 32, and 33 in FIG. This signal is a waveform indicated by reference numeral 42 in FIG.
[0040]
By multiplying the signal waveform 41 of the input image data in FIG. 4A and the signal waveform 42 of the sawtooth wave in FIG. 4B, an output signal having a waveform indicated by reference numeral 43 in FIG. can get. This waveform 43 is a flat signal having a small step between the white level (1) area and the white level (2) area and having a slope of almost “0”. By combining this flat signal with the left and right image data into a single piece of image data in the next stage synthesis circuit 55 (FIG. 2 (A)), a flat and smooth amplitude is obtained even at the connected portion. The characteristic is obtained, and the amplitude waveform distortion is corrected.
[0041]
As described above, according to the solid-state imaging device according to the present embodiment, in a solid-state imaging device (for example, a video camera) using a CCD imaging device having a means for dividing an image area into two right and left parts and reading out pixel signals for each area, It is possible to suppress the occurrence of vertical streak-like flaws due to steps at the joints of images due to amplitude waveform distortion generated in image data, and it is possible to provide a video camera with reduced image degradation.
[0042]
The image correction based on the white level in the solid-state imaging device according to the present embodiment is generally performed before shipping a product such as a digital still camera or a digital video camera.
[0043]
Next, a solid-state imaging device according to a second embodiment of the present invention will be described with reference to the drawings. The solid-state imaging device according to the present embodiment has a configuration substantially similar to that of the solid-state imaging device according to the first embodiment, and FIGS. 1 and 2 illustrate the solid-state imaging device according to the first embodiment. The description is omitted because it is the same.
[0044]
FIG. 5 is a functional block diagram illustrating a schematic configuration of the image correction circuit (black level correction circuit) according to the present embodiment. The left and right image data digitally converted by the AD converter are input to the Din (L) and Din (R) terminals of the image correction circuit.
[0045]
Left and right input image data include optical black data detection (OB detection) 71 and 82, dummy pixel data detection (DUM detection) 72 and 83, and black level detection.
Each data value is measured by a detection circuit of (1) 73/84 and black level detection (2) 74/85. Correction values are calculated by the correction value calculation circuits 75 and 86 based on the measurement data values from the respective detection circuits 71 to 85.
[0046]
The sawtooth wave signal generation circuits 76 and 87 output a sawtooth wave signal. The correction values calculated by the correction value calculation circuits 75 and 86 are set in amplitude parameter registers 77 and 88, and are multiplied by the correction values and the sawtooth signal by the multiplication circuits 78 and 89. The offset correction values calculated by the correction value calculation circuits 75 and 86 are set in offset value parameter registers 79 and 90, and the outputs of the multiplication circuits 78 and 89 and the offset correction values are added in offset addition circuits 80 and 91. Then, the input image data of Din (L) and Din (R) and the value added in the offset addition circuits 80 and 91 are added in the correction data addition circuits 81 and 92.
[0047]
Next, the operation of the image correction circuit shown in FIG. 5 will be described with reference to FIGS. FIG. 6A is a diagram illustrating data detection of each unit in a light-shielded state before starting the camera, for example, in an iris light-shielded state. FIG. 6B is a diagram illustrating control in an operation mode (non-light-shielded state). It is. First, the state of FIG. 6A will be described. Reference numeral 96 in FIG. 6A indicates an image data signal in one horizontal scanning period of left and right image data.
[0048]
The left and right image output signals from the CCD image sensor are composed of signal areas of OB data (OB), image data, and then dummy data (DUM). The OB data (OB) indicates a signal value in a light-shielded state on the imaging surface of the CCD, and is a data value serving as an actual black reference. On the other hand, the DUM data is pixel data when the horizontal transfer CCD performs idle read (idle transfer read), and is reference signal data.
[0049]
The black level detection (1) and the OB data, and the black level detection (2) and the DUM data are also close in distance, and have a strong correlation with each other. In the iris light blocking state at the time of starting the camera, four data of OB data, black level detection (1), black level detection (2), and DUM data are measured by each detection circuit. As shown by reference numeral 96 in FIG. 6A, the amplitude distortion of the image data has an amplitude difference between the black level detection (1) and the black level detection (2), and the slope is substantially linearly connected therebetween. It has a wavy waveform.
[0050]
A sawtooth wave signal having the same sign as the amplitude difference between the black level detection (1) and the black level detection (2) and having the opposite sign is used as the sawtooth wave generating circuit 76, the amplitude circuit 77, and the multiplier 78 in FIG. And a sawtooth wave generating circuit 87, an amplitude circuit 88, and a multiplier 89. The signals generated by the multipliers 78 and 89 are waveforms indicated by reference numeral 92 in FIG.
[0051]
By adding the waveform data indicated by reference numeral 92 in FIG. 6A and the input image data indicated by reference numeral 91, the data indicated by reference numeral 92 is added to the data indicated by dashed lines, and indicated by reference numeral 93. A waveform is obtained as an output signal. An almost flat signal with a small level difference (inclination of substantially "0") in the areas of black level detection (1) and black level detection (2) is obtained. The image data is adjusted by the offset parameter data 79 and 90 in FIG. 5 so that the step between the left and right image data becomes “0”, and the combining circuit 55 (FIG. 2A) connects the left and right image data. By combining them into one piece of image data, the amplitude waveform distortion at the joint of the divided image areas is corrected, and a flat and smooth amplitude characteristic is obtained.
[0052]
Next, FIG. 6B is a diagram showing an operation at the time of camera operation (at the time of shooting). During the operation of the camera, the level of the amplitude distortion fluctuates as shown by the dashed line (reference numeral 102) due to the fluctuation of the power supply voltage and the temperature fluctuation with respect to the solid line signal denoted by reference numeral 101, so that the correction amount must always be controlled. Must. However, since the black level (1) and the black level (2) cannot be detected as in the case of FIG. 6 (A), the OB data and the DUM data, which can be measured at all times, are used for imaging. Perform the correction dynamically.
[0053]
It is considered that the OB data is close in distance to the black level detection (1) in FIG. 6A and shows similar operation characteristics with respect to fluctuations in power supply and temperature. Further, it is considered that the DUM data and the black level (2) show similar operation characteristics. Therefore, it is considered that the amount of shift between the black level detection (1) and the black level detection (2) during the operation of the camera (at the time of photographing) is substantially equal to the amount of shift between the OB data and the DUM data. Therefore, the values of the amplitude parameter registers 77 and 78 in FIG. 5 are changed by an amount corresponding to the amount of displacement of the OB data with respect to the value of the DUM data, and as shown by reference numeral 103 in FIG. The correction is performed by changing the amplitude of the sawtooth wave signal generated by the sawtooth wave generating circuit 76, the amplitude circuit 77, the multiplier 78 and the sawtooth wave generating circuit 87, the amplitude circuit 88, and the multiplier 89. The waveform of the corrected image data becomes substantially flat as indicated by reference numeral 104 in FIG. 6B, and it can be seen that dynamic correction is possible.
[0054]
In FIGS. 6A and 6B, the transition is obtained using DUM data as a reference. However, it is also possible to control the correction data from the transition of DUM data using OB as a reference in the same manner.
[0055]
As described above, according to the solid-state imaging device according to the present embodiment, in a solid-state imaging device (mainly a digital video camera) using a CCD imaging device having a means for dividing an image area into two right and left parts and reading out pixel signals for each area, It is possible to suppress image deterioration due to a step at a joint of images due to amplitude waveform distortion generated in image data. Further, it is possible to dynamically correct amplitude distortion due to power supply fluctuation and temperature fluctuation during the photographing operation, and it is possible to provide a video camera without image degradation.
[0056]
The correction processing of the solid-state imaging device according to each of the above embodiments can be applied not only to a luminance signal but also to a color signal, and can also be applied to a color solid-state imaging device. For example, when color filters of magenta, green, cyan, and yellow are arranged on the imaging surface of the solid-state imaging device in a mosaic pattern, and a color solid-state imaging device that outputs pixel signals for each color in a point-sequential manner is used, magenta, green, Either four correction processing circuits according to the present embodiment are provided independently for each color pixel of cyan and yellow, or correction coefficients suitable for each of the four types of color pixels are provided independently, and each color By switching the correction coefficients of the above, it is possible to cope with a color solid-state imaging device. Further, in addition to the CCD solid-state imaging device, a MOS solid-state imaging device can be supported.
[0057]
In the above-described embodiment, the solid-state imaging device in which the horizontal CCD is divided into two in the left and right directions is described as an example. Is not limited.
[0058]
Although the embodiments have been described above, the present invention is not limited to these examples, and it goes without saying that various modifications are possible. The solid-state imaging device according to the present embodiment can be applied to various electronic devices including a digital still camera, a digital video camera, a notebook personal computer, a mobile phone, and the like including the same.
[0059]
【The invention's effect】
By implementing the present invention, in a solid-state imaging device having a means for dividing an image area and reading out pixel signals for each area, a stripe due to a step at an image joint due to an amplitude waveform distortion generated at a joint between the divided image areas. This makes it possible to suppress the occurrence of scratches in the shape, and to obtain an image without deterioration.
[Brief description of the drawings]
FIG. 1 is a plan view showing a schematic configuration of a solid-state imaging device according to an embodiment of the present invention.
FIG. 2A is a functional block diagram illustrating a schematic configuration of a solid-state imaging device according to an embodiment of the present invention, and FIG. 2B is a schematic diagram of a correction circuit illustrated in FIG. 2A; It is a functional block diagram showing a configuration.
FIG. 3 is a functional block diagram illustrating a schematic configuration of a white level correction circuit in the solid-state imaging device according to the first embodiment of the present invention;
FIGS. 4A and 4B are diagrams showing a procedure of correction in a white level correction circuit in the solid-state imaging device according to the first embodiment of the present invention.
FIG. 5 is a functional block diagram illustrating a schematic configuration of a black level correction circuit in a solid-state imaging device according to a second embodiment of the present invention.
FIGS. 6A and 6B are diagrams showing a procedure of correction in a black level correction circuit in a solid-state imaging device according to a second embodiment of the present invention.
FIG. 7 is a diagram illustrating a procedure of screen composition in the screen composition circuit according to the embodiment of the present invention.
FIG. 8 is a functional block diagram illustrating a schematic configuration of a general solid-state imaging device that performs two-screen synthesis.
FIG. 9 is a diagram showing a procedure of screen synthesis in a general solid-state imaging device that performs two-screen synthesis.
FIG. 10 is a functional block diagram illustrating a configuration example of a white level correction circuit in a general solid-state imaging device that performs two-screen synthesis.
FIG. 11 is a diagram illustrating a first problem when a general solid-state imaging device that performs two-screen synthesis is used.
FIG. 12 is a functional block diagram illustrating a schematic configuration of an image correction circuit based on detection of a dummy signal in a general solid-state imaging device that performs two-screen synthesis.
FIG. 13 is a diagram illustrating a problem (second problem) when a correction process is performed using the circuit of FIG. 12;
[Explanation of symbols]
1, 51, 111 CCD solid-state imaging device, 2 photoelectric conversion device (photodiode), 3 vertical charge transfer path (VCCD), 4, 5 horizontal charge transfer path (HCCD), 6, 7 amplifier, 11 , 12 ... signal processing circuit, 13 ... synthesis circuit, 21, 28 ... white level detection circuit (1), 22, 29 ... white level detection circuit (2), 23, 30 ... correction value calculation circuit, 24, 31 ... saw Wave generator circuit, 25, 32 ... register (amplitude parameter register), 26, 33 ... multiplier, 27, 34 ... multiplier, 52, 53 ... correlated double sampling (CDS) circuit and AD converter, 54 ... correction circuit, 55: screen synthesis circuit, 60: signal processing circuit, S1: image signal output, 61: one horizontal period, 71, 82: optical black data detection circuit (OB detection), 72, 83: dummy pixel data , Black level detection circuit (1), 74, 85 black level detection circuit (2), 75, 86 correction value calculation circuit, 76, 87 sawtooth wave generation circuit, 77, 88: amplitude circuit, 78, 89: multiplier, 79, 90: offset circuit (offset value parameter register), 80, 91: offset addition circuit (adder), 81, 92: correction data addition circuit (adder) ).

Claims (22)

A solid-state imaging device, comprising: a plurality of divided pixel regions; and a unit that reads a pixel signal transferred by a charge transfer path provided for each of the divided pixel regions.
A correction circuit that detects a characteristic value of an image signal during one unit readout period in each of the divided pixel regions and corrects the characteristic value of the pixel signal at a plurality of times during the one unit readout period so as to approach each other. Equipped solid-state imaging device. 2. The solid-state imaging device according to claim 1, wherein the characteristic value is a white level signal obtained by measuring a white chart using a signal value in a light-shielded state as a reference signal. A solid-state imaging device, comprising: a plurality of divided pixel regions; and a unit that reads a pixel signal transferred by a charge transfer path provided for each of the divided pixel regions.
A white level signal detecting means for detecting a white level signal obtained by measuring a white chart with a signal value in a light-shielded state as a reference signal during one unit readout period in each of the divided pixel regions;
A correction circuit that corrects an image signal such that white level signal values detected by the white level signal unit approach at a plurality of times during the one-unit readout period;
A solid-state imaging device comprising: a screen combining circuit that combines a screen of the divided pixel region based on the corrected image signal. The correction circuit generates a compensation signal having a multiplied value for compensating the difference based on a difference between the white level signals detected at a plurality of times during the one-unit readout period, and the compensation signal and a signal before correction. 4. The solid-state imaging device according to claim 3, wherein the circuit multiplies the following. The solid-state imaging device according to claim 4, wherein the compensation signal is a sawtooth signal having a slope opposite to the slope of the amplitude of the white level signal before correction. Provided in a solid-state imaging device having: a plurality of divided pixel regions; and a unit for reading a pixel signal transferred by a charge transfer path provided for each of the divided pixel regions.
A white level signal detection circuit for detecting a white level signal obtained by measuring a white chart with a signal value in a light-shielded state as a reference signal during one unit readout period in each of the divided pixel regions;
A correction circuit that corrects the image signal so that the white level signal value detected by the white level signal means approaches at a plurality of times during the one-unit readout period. An image correction circuit used in an image sensor having a unit that divides an image region into a plurality and reads a pixel signal for each of the divided regions,
Means for detecting the amplitudes of the two image areas, means for calculating the amplitude correction values of the two detected image areas, and image correction means for the image correction means for the divided image data. An image correction circuit, comprising: means for generating a sawtooth wave signal having a slope opposite to the slope of the amplitude at the two locations based on the signal; and means for adjusting the amplitude of the sawtooth wave signal. A plurality of divided pixel regions; and a unit for reading a pixel signal transferred by a charge transfer path provided for each of the divided pixel regions, wherein one unit is read from each of the divided pixel regions. A white level signal detecting means for detecting a white level signal obtained by measuring a white chart using the signal value in the light-shielded state as a reference signal during the period; A solid-state imaging device comprising: a correction circuit that corrects an image signal so that a white level signal value detected by the means approaches, and a screen synthesis circuit that synthesizes a screen of the divided pixel region based on the corrected image signal Digital video camera with. A pixel region including a light-shielded pixel that is divided into a plurality of divided pixel regions, each of which is in a light-shielded state on the pixel region surface for obtaining a black-level reference signal; and a pixel region provided for each of the divided pixel regions. Means for reading a pixel signal transferred by the charge transfer path,
An image signal of the light-shielded pixel during one unit readout period in each of the divided pixel regions, an empty readout signal at least one of before and after the one unit readout period, and a plurality of black level signals measured in advance. A solid-state imaging device including a correction circuit that corrects the amplitude of the signal during the one-unit readout period so that the amplitude of the signal becomes equal. 10. The solid-state imaging device according to claim 9, wherein the black level signal is a first and a second at least two black level signals measured in a state where the entire pixel area surface is shielded from light. . One of the first black level signal and the second black level signal is temporally close to the pixel signal of the light-shielded pixel, and the other is at a position temporally close to the empty readout signal. The solid-state imaging device according to claim 9, wherein the measured signal is a signal measured by the measurement. A pixel region including a light-shielded pixel that is divided into a plurality of divided pixel regions, each of which is in a light-shielded state on the pixel region surface for obtaining a black-level reference signal; and a pixel region provided for each of the divided pixel regions. Means for reading a pixel signal transferred by the charge transfer path,
An optical black signal detection circuit that detects an image signal of the light-shielded pixel in each of the divided pixel regions,
A dummy pixel data detection circuit for detecting an empty read signal;
A black level detection circuit for detecting a plurality of black level signals;
A correction value calculation circuit for obtaining a correction value for making the signal amplitudes equal during the one-unit readout period based on the optical black signal detection circuit, the dummy pixel data detection circuit, and the black level detection circuit A solid-state imaging device comprising: Further, based on the values detected by the dummy pixel data detection circuit and the optical black signal detection circuit, black level signal values close to each other are estimated, and the amplitude of the signal is estimated based on the estimated black level signal. 13. The solid-state imaging device according to claim 12, wherein a slope is obtained, and a compensation wave for compensating the slope to be flat and original pixel data are added. 14. The solid-state imaging device according to claim 13, wherein the compensation wave is a sawtooth signal wave having a reverse slope of the amplitude of the signal based on the black level signal. A pixel region including a light-shielded pixel that is divided into a plurality of divided pixel regions, each of which is in a light-shielded state on the pixel region surface for obtaining a black-level reference signal; and a pixel region provided for each of the divided pixel regions. Means for reading a pixel signal transferred by the charge transfer path, which is provided in the solid-state imaging device,
An optical black signal detection circuit that detects an image signal of the light-shielded pixel in each of the divided pixel regions,
A dummy pixel data detection circuit for detecting an empty read signal;
A black level detection circuit for detecting a plurality of black level signals;
A correction value calculation circuit for obtaining a correction value for making the signal amplitudes equal during the one-unit readout period based on the optical black signal detection circuit, the dummy pixel data detection circuit, and the black level detection circuit An image correction circuit comprising: Further, based on the values respectively detected by the dummy pixel data detection circuit and the optical black signal detection circuit, a black level signal value close to each value is estimated, and a signal of the signal is estimated based on the estimated black level signal. 16. The image correction circuit according to claim 15, wherein a slope of the amplitude is obtained, and a compensation wave for compensating the slope to be flat and original pixel data are added. 17. The image correction circuit according to claim 16, wherein the compensation wave is a sawtooth wave having a reverse slope of the amplitude of the signal based on the black level signal. A pixel region including a light-shielded pixel that is divided into a plurality of divided pixel regions, each of which is in a light-shielded state on the pixel region surface for obtaining a black-level reference signal; and a pixel region provided for each of the divided pixel regions. Means for reading a pixel signal transferred by the charge transfer path,
An optical black signal detection circuit for detecting an image signal of the light-shielded pixel in each of the divided pixel regions; a dummy pixel data detection circuit for detecting an empty read signal; and a black level detection circuit for detecting a plurality of black level signals And a correction value for obtaining a correction value for equalizing the signal amplitude during the one-unit readout period based on the optical black signal detection circuit, the dummy pixel data detection circuit, and the black level detection circuit. A digital video camera having a solid-state imaging device including a value calculation circuit. An image correction circuit used in a video camera using an imaging device having a unit that divides an image region into a plurality and reads pixel signals for each region,
Image correction means for left and right image data, a means for detecting an optical black signal value of pixel data, a means for detecting a signal value of a non-feed portion, and a black level of an image area at a plurality of light-shielded positions. Means for detecting, means for calculating a correction value, sawtooth signal generation means, and means for adjusting the amplitude of the sawtooth signal, image correction means,
Means for adding the set value,
An image correction circuit, comprising: means for adding image data. A solid-state imaging device, comprising: a pixel region; and a unit that reads out a pixel signal transferred by a charge transfer path provided for each pixel region.
A solid-state imaging device including a correction circuit that detects a characteristic value of an image signal in the pixel region during one unit readout period and corrects the characteristic value of the pixel signal at a plurality of points in time during the one unit readout period . A color solid-state imaging device, comprising: a plurality of divided pixel regions; and a unit that sequentially reads color pixel signals of a plurality of colors transferred by a charge transfer path provided for each of the divided pixel regions.
A white level signal detecting means for detecting a white level signal obtained by measuring a white chart with a signal value in a light-shielded state as a reference signal during one unit readout period in each of the divided pixel regions;
A plurality of correction circuits for independently correcting the color image signals of the plurality of colors for each color so that the white level signal values detected by the white level signal means approach at a plurality of times during the one-unit readout period;
A color solid-state imaging device having a screen composition circuit for composing a screen of the divided pixel area based on the corrected color image signal. A pixel region including a light-shielded pixel that is divided into a plurality of divided pixel regions, each of which is in a light-shielded state on the pixel region surface for obtaining a black-level reference signal; Means for sequentially reading color pixel signals of a plurality of colors transferred by the charge transfer path, and a color solid-state imaging device,
An optical black signal detection circuit that detects an image signal of the light-shielded pixel in each of the divided pixel regions,
A dummy pixel data detection circuit for detecting an empty read signal;
A black level detection circuit for detecting a plurality of black level signals;
Based on the optical black signal detection circuit, the dummy pixel data detection circuit, and the black level detection circuit, the correction value for equalizing the signal amplitude during the one-unit readout period is changed for the plurality of colors. A solid-state imaging device comprising: a plurality of correction value calculation circuits independently obtained for each color of a color image signal.

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