JP2013150144A - Imaging method and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct unevenness of a top dark part with a high electron multiplication factor of an electron multiplication type CCD imaging element.SOLUTION: An imaging apparatus includes: an electron multiplication type CCD imaging element; a first acquisition section for acquiring an image signal outputted from an effective pixel of a light receiving face of the CCD imaging element; a second acquisition section for acquiring a signal outputted from a shielded pixel in at least one of a top part and a bottom part of the light receiving face of the CCD imaging element; and a dark part correction section for correcting dark part unevenness. The imaging apparatus also includes means for calculating a first representative value such as a center value and a lower limit value of the signal outputted from the shielded pixel acquired in the second acquisition section. The dark part correction section corrects the dark part unevenness of a video signal in a horizontal scanning period of a screen upper end part from which a vertical video period starts after a vertical feedback period ends in proportional correlation with an average of a vertical period or more of the representative value of the signal outputted from the shielded pixel and subtracts a screen upper end correction signal obtained by multiplying a screen upper end unevenness signal which is previously prepared by the average of the vertical period or more of the representative value from the video signal of the horizontal scanning period of the screen upper end part.

Description

  The present invention relates to an improvement in sensitivity of an imaging apparatus having a solid-state imaging element.

  CCD (Charge-Coupled-Device) image sensors are less sensitive than solid-state image sensors, and there are few pixels called white scratches with abnormally high dark current levels, but white scratches occur at high temperatures, during high-sensitivity imaging, or during storage. Many. Further, when the near-infrared sensitivity of the CCD image sensor is increased, the photodiode becomes deeper and white scratches increase. For this reason, when the sensitivity is improved by the accumulation operation, white scratches are further increased, and thus the improvement in effective sensitivity is limited. Also, a timing generator (TG), a vertical transfer driver, and a horizontal transfer driver are required to operate the CCD image sensor.

  The electron multiplying CCD image sensor (Electron-Multiplying-CCD or EM-CCD) is visible because it can be combined with a CMG driving unit, an electronic cooling unit, and a temperature sensor to control the gain of electron multiplication. Quasi-video monitoring without illumination for night-time shooting of light and near-infrared light has become possible (see Non-Patent Document 1). In general, the timing is adjusted by a CR integration phase adjustment circuit combining a capacitor and a resistor.

  Furthermore, a CDS (Correlated Double Sampling) that removes noise from the signal output from the CCD, a dark current correction and variable gain amplification circuit (hereinafter referred to as AGC), and an ADC (Analog Digital Converter) that converts the digital video signal Vi. AFE (Analog Front End) with built-in ubiquity.

However, the electron multiplication factor of the EM-CCD varies depending on the temperature and the integrated amount of the high electron multiplication factor and the amount of incident light (see Non-Patent Document 2 and Non-Patent Document 3).
The EM-CCD increases the electron multiplication factor in a positive correlation with the voltage amplitude value of the electron multiplier electrode. However, when the electron multiplication factor is increased, the electron multiplication factor is increased by a slight change in the voltage amplitude value of the electron multiplier electrode. The magnification varies (see Non-Patent Document 1). For this reason, when the electron multiplication factor increases, the screen unevenness (shading) increases. In addition, the EM-CCD is susceptible to white flaws because the vertical light-shielding pixels (Vertical-Optical Black or below V-OB) above or below the effective screen are generally as few as four horizontal scanning lines. Further, since the dark current level increases in proportion to the electron multiplication factor, the left or right horizontal shading pixel (Horizontal-Optical Black or below H-OB) clamp potential of the effective screen is also easily affected by white scratches.

  Then, during the vertical blanking period of the EM-CCD having the FIT-CCD structure, horizontal transfer such as electron multiplication transfer is stopped, and high-speed vertical transfer of signal charges is performed from the imaging unit to the storage unit. Therefore, at the upper end (Top V) portion of the screen where the vertical blanking period ends and the vertical video period starts, each power supply voltage and the GND potential fluctuate. Further, at the time of high electron multiplication, the power consumption of electron multiplication transfer also increases, and fluctuations in the power supply voltage and the GND potential increase. As a result, at the time of high electron multiplication, the dark current and the electron multiplication factor for the power supply voltage fluctuation and the GND potential fluctuation fluctuate. In addition, the H-OB is at the top (Top V) portion of the screen where the vertical blanking period ends and the vertical video period starts from the phase shift of the horizontal transfer pulse due to the power supply voltage fluctuation and the GND potential fluctuation of the TG CR integration phase adjustment circuit. The clamp phase and the clamp potential fluctuate, and dark portions (dark) unevenness (shading) occur.

  Therefore, when the electron multiplication factor is increased, dark portion unevenness (shading) increases in the upper end (Top V) portion of the screen where the vertical blanking period ends and the vertical video period starts. In addition, it was difficult to correct dark shading, which increases when the electron multiplication factor is increased.

Japanese Patent Laid-Open No. 2003-189318 (CCD unevenness is variable depending on sensitivity)

TI TC246RGB-B0 680 x 500 PIXEL IMPACTRONTM PRIMARY COLOR CCD CCD IMAGESENSOR SOCS087- DECEMBER 2004-REVISED MARCH 2005 Hamamatsu Photonics Principle and Technology of High Sensitive Camera Cat No.SCAS0020J01 DEC / 2006 (Overview of electron multiplication factor) ANDOR Technical Note Longevity in EMCCD and ICCD Part I-EMCCD 14-Mar-06 (Measures against deterioration of electronic multiplication factor over time)

  An object of the present invention is to correct dark shading in a portion where a vertical video period starts at a high electron multiplication factor of an electron multiplying CCD image pickup device.

  In order to solve the above-described problems, the present invention calculates an electron multiplication factor of the electron multiplying CCD image pickup device in an image pickup apparatus using the electron multiplying CCD image pickup device, and interlocks with the calculated electron multiplication factor. Then, the above-mentioned calculated electronic multiplication factor is applied to the screen top edge non-uniformity signal (shading) prepared in advance at the top edge (Top V) of the screen where the vertical blanking period ends and the vertical video period begins. In this imaging method, the screen upper end correction signal obtained in this way is subtracted from the video signal in the horizontal scanning period at the upper end portion of the screen.

  Also, an electron multiplying CCD image pickup device, a temperature detecting means for the image pickup device of the CCD image pickup device, a drive means for the electron multiplying electrode of the CCD image pickup device, a dark portion correcting portion for correcting dark portion unevenness, a high electron multiplying factor and incidence In an imaging apparatus having a means for calculating an integral amount of a product with a light amount and approximating an electron multiplication factor from the calculated integration amount, the image pickup device is positively correlated with the approximated electron multiplication factor (proportional to the electron multiplication factor) Then, the dark portion unevenness of the video signal in the horizontal scanning period at the upper end portion of the screen at the end of the vertical blanking period and the start of the vertical video period is converted to the previously calculated screen upper end unevenness signal by the dark portion correction unit. The color solid-state imaging device is characterized by subtracting the screen upper end correction signal obtained by applying from the video signal of the horizontal scanning period at the upper end portion of the screen.

  In addition, an electron multiplying CCD image sensor, a first acquisition unit that acquires an image signal output from an effective pixel on the light receiving surface of the CCD image sensor, and at least one of an upper part or a lower part of the light receiving surface of the CCD image sensor In an imaging apparatus having a second acquisition unit that acquires a signal output from a light-shielded pixel, a signal output from the left and right (H-OB of V-OB) of the light-shielded pixel acquired by the second acquisition unit Means for calculating a first representative value (electron-multiplied dark current amount) such as an average value in the vicinity of the center of the first reference value of the first representative value at the time of non-multiplication of each temperature (reference dark current) ), And multiply the average of the ratio between the reference value and the first representative value (electron multiplication factor) over 3 vertical periods by the uneven signal at the top of the screen at the time of electron multiplication. Subtracting the image top edge correction signal obtained from the video signal in the horizontal scanning period An image device.

  In addition, an electron multiplying CCD image sensor, a first acquisition unit that acquires an image signal output from an effective pixel on the light receiving surface of the CCD image sensor, and at least one of left and right of the light receiving surface of the CCD image sensor A third acquisition unit that acquires a signal output from the light-shielded pixel, and an average value from the lower limit Nth to N + Mth of the signal output from the light-shielded pixel acquired by the third acquisition unit; And a second representative value calculating means, and at least acquired in the third acquisition unit in the vertical scanning period corresponding to the upper end portion of the screen where the vertical blanking period ends and the vertical video period starts. A dark portion correction signal calculated by interpolating the second representative value of the signal output from the light-shielded pixel by quadratic curve in the horizontal scanning period, and a video signal in the horizontal scanning period of the upper end portion of the screen as the second representative value. Subtracting from An imaging apparatus characterized.

  As described above, according to the present invention, it is possible to correct the dark portion unevenness (dark shading) in the portion where the vertical video period starts at the high electron multiplication factor of the electron multiplication type CCD image pickup device in accordance with the change of the electron multiplication factor. it can.

The block diagram which shows the imaging device of the whole structure of one Example of this invention at the time of using the CCD image pick-up element with a color separation filter. 1 is a block diagram showing an image pickup apparatus having an overall configuration according to an embodiment of the present invention when a color separation optical system and three CCD image pickup elements are used. The block diagram which shows the internal structure of the detection part which detects the representative value of OB including the detection of the dark current of one Example of this invention, a smear, and multiplication unevenness. The block diagram which shows the internal structure of the detection part which detects the representative value of OB including the detection of the dark current of one Example of this invention, a smear, and multiplication unevenness. The block diagram which shows the internal structure of the detection part which detects the average value of the 3rd to 5th value from the minimum value of H-OB of one Example of this invention as a representative value. The flowchart of one Example of this invention which detects the 2nd value from the minimum value of the vertical pixel of V-OB as a representative value. The flowchart of one Example of this invention which detects the 2nd value from the minimum value of V-OB as a representative value. The flowchart of one Example of this invention which detects the average value of the 3rd to 5th value from the minimum value of H-OB as a representative value.

In the electron multiplying CCD image pickup device, the clock phase is likely to fluctuate at the time of electron multiplication, and the dark portion unevenness (shading) at the upper end (Top V) portion where the vertical blanking period ends and the vertical video period starts increases. . Further, the electron multiplying CCD image pickup device has very large white scratches at the time of electron multiplication. Therefore, not only the video signal of the horizontal scanning period output from the effective pixels on the light receiving surface of the CCD image sensor, but also the H-OB portion having only about 20 pixels on the left and right of the vertical shading pixel (V-OB) having only about 4 rows. The average value becomes unstable due to white scratches. Therefore, an average value around the median value of the signals output from the light-shielded pixels acquired by the second acquisition unit that acquires signals output from the left and right of the light-shielded pixels above and below the light receiving surface of the CCD image pickup device is obtained. Thus, the second representative value (electron multiplying dark current amount) is calculated. Then, the reference value (reference dark current amount) of the first representative value at the time of non-multiplication of each temperature is measured, and the white value is determined from the average of the ratio of the reference value and the second representative value over three vertical periods. Calculates the electron multiplication factor that is not affected by scratches or noise. A correction signal obtained by applying a non-uniformity signal at the upper end of the screen at the time of electron multiplication measured in advance is subtracted from the video signal in the horizontal scanning period at the upper end portion of the screen.
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of each drawing, the same reference numerals are assigned to components having a common function, and duplication of description is avoided as much as possible.
An embodiment of the present invention will be described with reference to FIGS. 1A, 1B, 2A, 2B, 2C, 3A, 3B, and 3C.

Calculate the integral amount of the product of EM-CCD 3, temperature sensor 8, CMG drive unit 15 for electron multiplier electrode drive, FEP 4 for correcting dark spot unevenness, and high electron multiplication factor and incident light quantity, In an imaging apparatus having a CPU 6 that approximately calculates an electronic multiplication factor from the calculated integration amount, the vertical retrace period ends with a positive correlation (proportional to the electronic multiplication factor) with the approximated electronic multiplication factor. Under the control of the CPU 6, the dark signal unevenness at the upper end portion of the screen where the vertical video period starts is corrected by the video signal processing unit 5 including FEP 4 or multiplication detection.
Also output from the EM-CCD 3, the effective pixel on the light receiving surface of the CCD image sensor, and at least one of the light-shielded pixels (Optical Black: OB) on the upper or lower side or the left or right of the light receiving surface of the CCD image sensor. 4 and FEP 4 for obtaining a signal to be acquired, and video signal processing unit 5 including FEP 4 or multiplication detection, in an imaging apparatus that corrects dark area unevenness, multiplication detection for calculating a representative value of a signal output from a light-shielded pixel And a video signal processing unit 5 including a positive correlation (in proportion to the electron multiplication factor) of the average value of the representative value of the signal output from the light-shielded pixel that is equal to or greater than the vertical period, and the vertical blanking period ends. The dark portion unevenness at the upper end portion of the screen where the video period starts is corrected by the video signal processing unit 5 including FEP 4 or multiplication detection under the control of the CPU 6.
The embodiments described below are for explanation, and do not limit the scope of the present invention. Accordingly, those skilled in the art can employ embodiments in which these elements or all of the elements are replaced with equivalent ones, and these embodiments are also included in the scope of the present invention.

An outline of an embodiment of an imaging apparatus according to the present invention will be described with reference to FIGS. 1A, 1B, 2A, 2B, 3A, and 3B. FIG. 1A is a block diagram showing an overall configuration of an embodiment of an imaging apparatus of the present invention when a CCD imaging device with a color separation filter is used. FIG. 1B is a block diagram showing the overall configuration of an embodiment of the imaging apparatus of the present invention when a color separation optical system and three CCD imaging elements are used. 2A and 2B are block diagrams showing an embodiment of the internal configuration of the detection unit in the video signal processing unit of the imaging apparatus according to the present invention, which detects a representative value of OB including detection of dark current, smear, and multiplication unevenness. FIG.
In addition, the average value part 68 and the average value part 69 in FIG. 2A and FIG. 2B are demonstrated in Example 2 and Example 3. FIG. FIG. 3A is a flowchart illustrating an example of a process of detecting the second value from the minimum value of the V-OB vertical pixels as a representative value in the imaging method and imaging apparatus of the present invention. FIG. 3B is a flowchart illustrating an example of a process of detecting the second value from the minimum value of V-OB as a representative value in the imaging method and the imaging apparatus of the present invention.

Next, FIG. 1A which is an example of the entire configuration of the imaging apparatus of the present invention will be described. FIG. 1A is a diagram illustrating an overall configuration of an imaging apparatus using a CCD imaging device with a color separation filter.
In FIG. 1A, 1 is an imaging device, 2 is an optical system such as a lens that forms incident light, 3 is a CCD imaging device that converts light incident from the optical system 2 into an electrical signal, and 4 is reset, CDS, and AGC. FEP including dark portion correction and ADC TG, 5 is a video signal processing unit including a multiplication detection processing unit, and 6 is a CPU (Central Processing Unit) that controls each unit in the imaging apparatus 1. Reference numeral 13 denotes a vertical transfer driving unit including a timing generator (TG), 15 denotes a CMG driving unit for performing gain control of electron multiplication, 8 denotes a temperature sensor, and 17 denotes a cooling unit.

The CCD image pickup device 3 is an EM-CCD with a color separation filter. The FEP 4 includes at least an AGC unit 402 that removes noise from the signal output from the CCD image sensor 3, an AGC unit 402 that adjusts the gain by correcting dark current on the output signal of the CDS 401, and an output signal from the AGC unit 402 ADC 403, TG 404, memory unit 405, D.D. An AGC unit 406 and a DAC unit 407 are included. 1A and 1B, the memory unit 405, D.I. The AGC unit 406 and the DAC unit 407 are not shown. The AGC and dark part correction may be executed by the video signal processing unit 5 including multiplication detection.
The TG 404 is a signal generator that outputs a horizontal transfer drive signal to the CCD image pickup device 3 and outputs a timing signal to the CDS 401, the AGC unit 402, and the ADC 403 in the FEP4.

In FIG. 1A (FIG. 1B), the read and vertical transfer drive unit 13 (13) outputs a read and vertical transfer drive timing signal, and each read vertical transfer unit of the CCD image pickup device 3 (3, 7, 9). Is output.
The cooling unit 17 includes a Peltier element that cools the CCD image pickup element 3, a Peltier element driving circuit, a heat radiation fin, a fan, and a fan driving circuit (not shown in FIG. 1B). The cooling unit 17 controls the temperature of the CCD image sensor 3 by cooling the CCD image sensor 3 according to the temperature detected by the temperature sensor 8 under the control of the CPU 6. In FIG. 1B, the cooling unit 17 and the temperature sensor 8 are not shown and are omitted.
The video signal processing unit 5 including multiplication detection performs various image processing on the digital video signal Vi, and a composite video signal (Video Burst Sync: VBS) or SDI (Serial) of the NTSC system or PAL (Phase Alternating by Line) system. Digital Interface) and converted into a video signal of a predetermined system such as HDTV SDI (HD-SDI) and output.

In FIG. 1A, a CCD image pickup device 3 such as an EM-CCD of the image pickup apparatus 1 generates a signal charge by photoelectrically converting incident light imaged on a light receiving surface by an optical system 2 using a photodiode (Photo Diode). After the transfer, the signal charge is multiplied by electrons while being transferred horizontally and output to the FEP4. The FEP 4 removes noise from the signal output from the CCD image pickup device 3, corrects the dark current component, amplifies the corrected signal, converts the signal to a digital video signal Vi, and converts the converted digital video signal Vi into a video signal processing unit. 5 is output. In the video signal processing unit 5 including multiplication detection, the digital video signal Vi is sent to the detection unit 18 and also sent to a subtracter 19 for performing signal processing to be described later.
FIG. 2A is a block diagram showing an internal configuration of an embodiment of the present invention of a video signal processing unit including detection of uneven multiplication when a CCD image pickup device with a color separation filter is used. Reference numeral 18 denotes a multiplication unevenness detector, and reference numeral 19 denotes a subtractor circuit. Reference numeral 6 denotes a CPU that controls each unit in the imaging apparatus 1 (see FIG. 1A). D. The AGC unit 50 matches the OB (Optical Black) representative value signal with the amplification degree of the AGC unit of the FEP. Adjusts the amplification level of the AGC unit itself. The OB representative value signal is a smear component signal including a V-OB dark current.
In FIG. 2A, the detection unit 18 compares the digital video signal Vi with the vertical pixel signals of the V-OB lines by the comparison units 41 to 42, stores them in the line memories 43 to 44 in ascending order, and includes vertical (hereinafter V) smear. An OB representative value signal is detected. The OB representative value signal including the V smear is compared by the comparison units 55 to 56, and the V smear is calculated from the difference between the maximum value including the V smear and the minimum value not including the V smear. Further, the average value of the H-OB signal of the V-OB line at the time of non-electron multiplication at the reference temperature and the value stored in the reference memory 48 are stored in the D.D. The dark current multiplication amount can be calculated by dividing the average value of the H-OB signal of the V-OB line by the value corrected for temperature by the AGC 50. Then, the H-OB signal of the V-OB line at the reference temperature at the non-electron multiplication at the reference temperature is averaged from the dark current of the effective pixel at the non-electron multiplication at the reference temperature, and the value stored in the reference memory 48 is subtracted. Then, by multiplying the value stored in the screen memory 49 by the dark current multiplication amount by the multiplier 52, the dark current of the difference between the effective pixel and V-OB can be calculated, and the adder 45 calculates the V smear. The sum of the dark current and V smear of each effective pixel can be calculated by adding the OB representative value including the correction, and the dark current and V smear of each effective pixel can be corrected by subtracting from the digital video signal Vi by the subtractor 19. Ineffective signal, that is, noise is reduced, and effective sensitivity is improved.

1B is an example in which the color separation optical system and three CCD image pickup devices are used, and the image pickup device of FIG. 1A includes one CCD image pickup device 3 and one FEP4. In contrast, the incident light that has entered the image pickup apparatus via the lens system 2 is, for example, R (red), G (green), or B (blue) using the color separation optical system 11. The colors are separated into the three primary colors of light (or their complementary colors), and the CCD image pickup devices 3, 7, 9 and FEPs 4, 10, 12 are used for the three separated colors. In this case, the video signal processing unit (including the multiplication unevenness detection process) 5 performs processing similar to that of the video signal processing unit 5 of FIG. 1A after combining these three colors at a predetermined ratio (see FIG. 1). The description of the same configuration and operation as in 1A is omitted).
The image signal processing unit of the embodiment of the imaging apparatus of the present invention shown in FIG. 2B is also a case where a color separation optical system and three CCD image sensors are used, as in FIG. 1B. The processing unit includes, for example, FEP units 4 ′, 10 for each color separated into three primary colors (or their complementary colors) such as R (red), G (green), and B (blue). And 12, the video signal Vi (for example, RVi, GVi, BVi) is input, and three signals are output for each color from the video memory unit 32 ′ and the correlation detection unit 33 ′. (Detailed illustration is omitted).

  Next, the operation of one embodiment of the present invention will be described with reference to FIGS. 1A and 2A. The CCD image pickup device 3 of the image pickup apparatus 1 photoelectrically converts incident light imaged on the light receiving surface by the optical system 2 with a photodiode to generate a signal charge. The signal multiplied and electron-multiplied is output to FEP4. The FEP 4 removes noise from the signal output from the CCD image pickup device 3, corrects the dark current component, converts the corrected signal into an amplified signal (digital video signal Vi), and sends it to the video signal processing unit 5. Output.

  Further, the vertical transfer drive unit (w / TG) 13 and the CMG drive unit 15 output signals for driving the CCD image pickup device 3 to the CCD image pickup device 3 in accordance with the control signals output from the CPU 6. In the CCD image pickup device 3, charges are read from the photodiodes according to the input signal and output to the CMG unit. The CMG unit horizontally transfers and outputs the input charge to the voltage conversion unit. The voltage converter converts the input charge into a voltage having a gradation of 14 bits or 14 bits and outputs the converted voltage to the FEP 4.

2A and 2B, an embodiment of the function for detecting the dark current multiplication amount of the present invention will be described. 2A and 2B are block diagrams showing an internal configuration of a detection unit that detects a representative value of OB including detection of dark current, smear, and multiplication unevenness according to an embodiment of the present invention. 18 is a detection unit, 19, 46 and 57 are subtractors, 45 is an adder, 51 is a divider, 52 is a multiplier, 47, 68 and 69 are average units, 43 and 44 are line memory units, and 48 is a reference memory. , 41, 42, 53, 54, 55, and 56 are comparison units, and 49 is an image memory unit.
The detection and correction operations of the vertical smear signal will be described with reference to FIGS. 2A, 2B, 3A, and 3B.

First, the embodiment shown in FIGS. 2A and 3A will be described. The CPU 6 in FIGS. 1A and 1B sets the upper limit value of the minimum value signal and the upper limit value of the second smallest signal in the line memory units 44 and 43, respectively. Here, as these upper limit values, for example, values obtained by quantifying the luminance of the signal may be used (each value described below is also quantified by the same standard). The comparison unit 42 compares the upper limit value stored in the line memory unit 44 with the pixel value of the video signal of the first line in the V-OB area (hereinafter referred to as V-OB1) between the pixels, and the value is small. The other signal (video signal of V-OB1) is stored in the line memory unit 44 as a minimum value signal of each pixel (steps 61 and 62).
The comparison unit 42 compares the pixel value of the video signal of V-OB2 and the minimum signal value in the line memory unit 44 between the pixels, and the signal having the smaller value is stored in the line memory unit 44 in each pixel. Is stored as a minimum value signal. The signal having the larger value is sent to the comparison unit 41. The comparison unit 41 compares the value of the larger signal with the upper limit value stored in the line memory unit 43 as the second smallest signal, and compares the smaller signal with the second smallest signal of each pixel. The signal is stored in the line memory unit 43 as a signal (step 63).
Similarly, the comparison unit 42 compares the pixel value of the V-OBN video signal of the Nth line (N is a natural number of 3 or more) with the minimum value of the memory unit 44 between the pixels, and the smaller value is obtained. Is stored in the line memory unit 44 as a signal of the minimum value of each pixel. The signal having the larger value is sent to the comparison unit 41 as a comparison 1 signal for each pixel (step 64).
The comparison unit 41 compares the value of the second smallest signal and the value of the comparison 1 signal between the pixels, and outputs the signal having the smaller value as the second smallest signal (comparison 2 signal) of each pixel. It memorize | stores in the memory part 43 (step 65).
When the comparison unit 42 finishes the last V-OB comparison process, the line memory unit 43 outputs the second smallest signal as the smear correction OB representative value signal (step 66), and the representative value detection process ends. (Step 67).
The average dark current multiplication amount in the screen or the average dark current multiplication amount between the screens is calculated from the horizontal period dark current multiplication amount or the average dark current multiplication amount in the screen by the circulation average of the average unit 68. The inter-screen average dark current multiplication amount is calculated by the circulation average, and is output to the CPU 6 in FIGS. 1A and 1B.

Next, the embodiment shown in FIGS. 2B and 3B will be described. The difference between FIG. 3B and FIG. 3A is that there are a comparison unit 53 and a comparison unit 54 instead of the averaging unit 47. The operation of the same part as FIG. 3A is omitted, and the operation of the comparison unit 53 and the comparison unit 54 will be described. The CPU 6 resets the upper limit value of the minimum value signal in the comparison unit 53 and the comparison unit 54. Here, as these upper limit values, for example, values obtained by quantifying the luminance of the signal may be used (each value described below is also quantified by the same standard).
The comparison unit 54 compares the reset upper limit value with the pixel value of the video signal in the first line of the V-OB area (hereinafter referred to as V-OB1) between the pixels, and the signal (V −OB1 minimum value signal) is stored in the comparison unit 54 as a minimum value signal of each pixel (steps 71 and 72).
The comparison unit 54 compares the pixel value of the video signal of V-OB2 with the minimum signal value of the comparison unit 54 between the pixels, and the signal having the smaller value is sent to the comparison unit 54 as the minimum value of each pixel. Store as a value signal. The signal having the larger value is sent to the comparison unit 53. The comparison unit 53 compares the value of the larger signal with the upper limit value reset to the comparison unit 53 as the second smallest signal between the pixels, and compares the smaller signal with the second smallest signal of each pixel. Is stored in the comparison unit 53 (step 73).
Similarly, the comparison unit 54 compares the pixel value of the V-OBN video signal of the Nth line (N is a natural number of 3 or more) and the minimum value of the comparison unit 54 between the pixels, and the smaller value is obtained. Is stored in the comparator 54 as a signal of the minimum value of each pixel. The signal having the larger value is sent to the comparison unit 53 as a comparison 1 signal for each pixel (step 74).
The comparison unit 53 compares the value of the second smallest signal and the value of the comparison 1 signal between the pixels, and stores the signal having the smaller value in the comparison unit 53 as the second smallest signal of each pixel. (Step 75). When the comparison unit 54 finishes the last V-OB comparison process, the comparison unit 53 outputs the second smallest signal as an OB representative value signal for dark current measurement (step 76), and the representative value detection process ends. (Step 77).

Further, the vertical smear and the horizontal smear are hardly mixed in the dark current and white scratch component of the H-OB portion of V-OB. Using this, as shown in the detection unit 45 of FIG. 2A, the signals of the H-OB portion of the V-OB of the EM-CCD in the non-electron multiplication state at the reference temperature are averaged and stored. Compared with the signal of the reference memory section, the dark current multiplication amount due to temperature and electron multiplication can be estimated in real time.
As another method, the fact that the minimum value of the vertical horizontal pixel level of V-OB is a dark current component in which vertical smear and horizontal smear are hardly mixed is used. That is, as shown in the detection unit 45 of FIG. 2B, the minimum value of the vertical horizontal of the V-OB is detected, and the minimum value of the vertical horizontal of the V-OB of the EM-CCD in the non-electron multiplication state at the reference temperature. If the signal is compared with the signal of the reference memory unit that has been stored by averaging, the amount of dark current multiplication due to temperature and electron multiplication can be estimated in real time. Therefore, the dark current is output from the screen effective pixel stored in the screen memory unit 49, and then the temperature and electron increase are added to the effective pixel OB difference reference dark current signal obtained by subtracting the addition average of the signals of the H-OB portion of V-OB. If the dark current multiplication amount due to doubling is applied, the dark current of the screen effective pixel that is the difference from OB can be estimated.

  That is, it uses an FEP of 14 bits or more, and includes an electron multiplying CCD image pickup device including a temperature measuring means and a V-OB, a variable voltage electron multiplying electrode driving unit, a gain variable amplifying unit, a line memory, and a screen memory. In the imaging method of the solid-state imaging device, the current representative value of the V-OB dark current and the dark current obtained by correcting the representative value of the V-OB dark current stored at the time of non-electron multiplication with the image sensor measurement temperature Is multiplied by the reference dark current of each effective pixel of the screen memory stored at the time of non-electron multiplication, and the ratio (the estimated value of the electron multiplication factor of each vertical period) is multiplied by the effective pixel signal. Subtract. As a result, the dark current unevenness of the interstitial fixed noise in the dark part that is conspicuous on the screen is subtracted, the dark current of the main component of 1 / f noise of the electron multiplication fluctuation is also subtracted, and V-OB is also subtracted. By subtracting the dark current and white flaw component of the screen effective pixel, which is the difference from OB, from the dark current and white flaw and vertical smear components of the OB, only the video signal of the screen effective pixel can be calculated.

Next, with reference to FIG. 2A and FIG. 3A, the processing operation for detecting the second smallest signal between the V-OB vertical pixels and detecting the OB representative value for smear correction will be described.
2A and 3A, the CPU 6 in FIGS. 1A and 1B sets the upper limit value of the minimum value signal and the upper limit value of the second smallest signal in the line memory units 43 and 44, respectively. Here, as these upper limit values, for example, values obtained by quantifying the luminance of the signal may be used (each value described below is also quantified by the same standard).
The comparison unit 42 compares the upper limit value stored in the line memory unit 44 with the pixel value of the video signal of the first line in the V-OB area (hereinafter referred to as V-OB1) between the pixels, and the value is small. This signal (video signal of V-OB1) is stored in the line memory unit 44 as a minimum value signal of each pixel (start step 61, minimum value storage step 62).
The comparison unit 42 compares the pixel value of the video signal of V-OB2 and the minimum signal value in the line memory unit 44 between the pixels, and the signal having the smaller value is stored in the line memory unit 44 in each pixel. Is stored as a minimum value signal. The signal having the larger value is sent to the comparison unit 41. The comparison unit 41 compares the value of the larger signal with the upper limit value stored in the line memory unit 43 as the second smallest signal, and compares the smaller signal with the second smallest signal of each pixel. The signal is stored in the line memory unit 43 as a signal (second smallest value storing step 63).

Similarly, the comparison unit 42 compares the pixel value of the V-OBN video signal of the Nth line (N is a natural number of 3 or more) with the minimum value of the line memory unit 44, and the value is small. This signal is stored in the line memory unit 44 as a minimum value signal of each pixel. The signal having the larger value is output to the comparison unit 41 as a comparison 1 signal for each pixel (comparison 1 signal output step 64).
The comparison unit 41 compares the value of the second smallest signal and the value of the comparison 1 signal between the pixels, and sets the signal having the smaller value as the second smallest signal (comparison 2 signal) of each pixel. This is stored in the unit 43 (Comparison 2 signal storage step 65).
When the comparison unit 42 finishes the last V-OB comparison process, the line memory unit 43 outputs the comparison 2 signal to the adder 45 as an OB representative value signal for smear correction (OB representative value output step 66). The representative value detection process ends (end step 67).

3A, the OB representative value signal is also input to the comparison unit 55 to calculate the maximum value of the OB representative value, and is also input to the comparison unit 56 to calculate the minimum value of the OB representative value. The subtractor 57 takes the difference between the maximum value of the OB representative value and the minimum value of the OB representative value, and outputs the difference value to the CPU 6 as a V-OB vertical smear.
If the smear amount is greater than or equal to a predetermined reference amount, the horizontal smear that leaks into the H-OB next to the effective pixel is equal to or greater than the vertical smear of about -80 dB. However, the horizontal smear leaking from the vertical smear leaking into the V-OB to the H-OB of the V-OB is negligible at about -160 dB.

Therefore, the averaging unit 47 of FIG. 3A adds and averages the V-OB H-OB, and stores the reference V-OB H-OB addition average stored in the reference memory unit 48 as D.D. The dark current multiplication amount of the vertical cycle can be calculated by taking a ratio with the reference H-OB in which the AGC unit 50 corrects the temperature and the FEP (Analog Front End: AFE) amplification degree and the divider 51.
The difference in the subtractor 46 between the H-OB addition average of the reference V-OB stored in the reference memory unit 48 and the reference dark current of the effective pixel is used as the effective pixel OB difference reference dark current. If the effective pixel reference dark current and the dark current multiplication amount are multiplied by the multiplier 52, the effective pixel OB differential dark current of the vertical period can be calculated. Then, the calculated effective pixel OB differential dark current and the OB representative value are added by the adder 45 and output to the subtracter 19.
Instead of calculating the addition average by the averaging unit 47 of FIG. 3A, the minimum value of H-OB may be calculated using the comparison unit 54 of FIG. 3B.

If the smear amount is less than a predetermined reference amount, the horizontal smear leaking into the H-OB next to the effective pixel is equal to or smaller than the vertical smear of about -80 dB and can be ignored. Therefore, the averaging unit 47 adds and averages the horizontal H-OBs of the effective pixels and stores the horizontal H-OB adding average of the reference effective pixels stored in the reference memory unit 48. The dark current multiplication amount in the horizontal period can be calculated by taking a ratio between the reference H-OB in which the AGC unit 50 corrects the temperature and the AFE amplification degree and the divider 51.
The difference between the reference H-OB addition average stored in the reference memory unit 48 and the reference dark current of the effective pixel is calculated by the subtractor 46, and the calculated difference is used as the effective pixel OB difference reference dark current in the screen memory. 49, and the multiplier 52 multiplies the effective pixel OB difference reference dark current and dark current multiplication amount stored therein. As a result of this multiplication, the effective pixel OB differential dark current of the horizontal period can be calculated. Further, the calculated effective pixel OB differential dark current of the horizontal period and the OB representative value are added by the adder 45, and the added value is output to the subtractor 19.

Similarly, the processing operation for detecting the second smallest signal of V-OB and detecting the OB representative value for dark current multiplication amount calculation will be described with reference to FIGS. 2A and 3B.
2A and 3B, the CPU 6 sets the upper limit value of the minimum value signal and the upper limit value of the second smallest signal in the comparison units 53 and 54, respectively. Here, as these upper limit values, for example, a numerical value of the luminance of the signal may be used. Each value described below is also quantified according to the same standard.
The comparison unit 54 compares the set upper limit value with the value of each pixel of the video signal in the V-OB area, and uses the signal with the smaller value (V-OB video signal) as the minimum value of V-OB. Is stored in the line memory unit 44 and set. Then, the signal having the larger value is output to the comparison unit 53 (start step 71, minimum value storage step 72).
The comparison unit 53 compares the value of the larger signal with the upper limit value set as the second smallest signal, and sets the smaller signal to the line memory unit 43 as the second smallest signal of V-OB. Store and set (second smallest value storage step 73).

Similarly, the comparison unit 53 compares the pixel value of the V-OBN video signal of the Nth line with the minimum value of the line memory unit 44 between the pixels, and the signal with the smaller value is compared between the pixels. The signal is stored in the line memory unit 44 as a minimum value signal. The signal having the larger value is output to the comparison unit 42 as a comparison 1 signal for each pixel (comparison 1 signal output step 74).
When the comparison unit 54 finishes the last V-OB comparison process, the comparison unit 53 outputs the second smallest signal to the divider 51 as an OB representative value signal for dark current multiplication amount calculation (OB representative value). The output step 75) ends the representative value detection process (end step 76).

That is, since the H-OB in the V-OB line has neither a vertical smear component nor a horizontal smear component of the high luminance signal of the effective pixel, the H-OB in the V-OB line can be used as a representative value of the dark current of the V-OB. -OB is added and averaged, H-OB in the V-OB line of the EM-CCD at the reference temperature at the time of non-multiplication is added and averaged, and the temperature corrected is divided by the representative value of the dark current of V-OB. Thus, it is possible to detect the multiplication factor for each screen V-OB of dark current, and to estimate the multiplication factor for each vertical period.
Alternatively, neither the vertical smear component nor the horizontal smear component of the high luminance signal of the effective pixel is present in the Nth value from the minimum value of V-OB, so that the minimum value of V-OB is the representative value of the dark current of V-OB. Even if the N-th value is calculated from the value, the N-th value is calculated from the minimum value of V-OB at the time of non-multiplication, and the temperature correction is divided, the dark current increases at each screen V-OB. The magnification can be detected, and the multiplication factor for each vertical period can be estimated.

  As described above, according to the first embodiment of the present invention, the dark portion unevenness (dark shading) of the portion where the vertical video period starts at the high electron multiplication factor of the electron multiplying CCD image pickup device corresponds to the change of the electron multiplication factor. It can be corrected. Even in the case of EM-CCD, in which the dark current level increases in proportion to the electron multiplication factor, generally four horizontal scanning lines and few V-OBs, the dark current level is also affected by a pixel called a white scratch with an abnormally high dark current level. However, there is almost no influence of pixels called “black scratches” or abnormal noise.

The configuration, operation, and effects similar to those of the first embodiment are omitted, and only differences are described.
In an imaging method of a solid-state imaging device having a CCD imaging device including an OB, a variable gain amplification (AGC) unit, a line memory unit, and a screen memory unit, a vertical pixel of V-OB is used as a detection amount that strongly correlates with the amount of dark current The representative value of the dark current amount, with either the horizontal minimum value of the minimum value (smear representative value), the minimum value of V-OB, or the minimum value of H-OB of V-OB as the representative value of dark current amount The average value of the dark current amount is defined as the circulation average of the values.
Specifically, as a detection amount strongly correlated with the dark current amount, the minimum value of the vertical pixel of the V-OB detected as a smear representative value is calculated as the representative value of the dark current amount in the horizontal direction. To do. Alternatively, the minimum value of V-OB may be detected and used as the representative value of the dark current amount. Alternatively, the minimum value of H-OB of V-OB may be detected and used as a representative value of the dark current amount.

As described in the first embodiment of the present invention, the embodiment of FIGS. 2A to 2B has a function of detecting the dark current multiplication amount. Therefore, an averaging unit 68 consisting of a register, an adder, and a coefficient unit that circulates and averages within the screen, and an averaging unit 69 consisting of a register, adder, and a coefficient unit that circulates between the screens are added to the detection unit of the first embodiment. The entire configuration shown in FIGS. 2A to 2B may be used. In this case, since the configuration and operation other than the averaging unit 68 and the averaging unit 69 are the same as those in the first embodiment, the description thereof is omitted.
In FIG. 2A to FIG. 2B, the average dark current multiplication in the screen is performed by the average of the average unit 68 based on the horizontal period dark current multiplication amount or the average dark current multiplication amount in the screen output from the detection units 18A to 18D. Or the average dark current multiplication amount between screens, and is output to the outside (CPU 6 in FIG. 1A or CPU 6 ′ in FIG. 1B) and to the averaging unit 69. Then, the current multiplication amount input to the averaging unit 69 is calculated as the inter-screen average dark current multiplication amount by the circulation average of the averaging unit 69, and is output to the CPU 6 in FIG. 1A or the CPU 6 ′ in FIG. 1B.

  In FIG. 1A or 1B, the CPU 6 controls the vertical transfer driver (w / TG) 13 to control the accumulation time. Further, the CPU 6 controls 4 (or 4, 10, 12) of the FEP and controls variable gain amplification. Further, the CPU 6 controls the video signal processing unit 5 including multiplication detection, controls the variable gain amplification of the dark current component of the effective pixel signal, subtracts it from the effective pixel signal, and outputs it.

  As described above, according to the second embodiment of the present invention, the dark portion unevenness (dark shading) of the portion where the vertical video period starts at the high electron multiplication factor of the electron multiplying CCD image pickup device corresponds to the change of the electron multiplication factor. It can not only be corrected.

The configuration, operation, and effects similar to those of the first and second embodiments are omitted, and only the differences are described.
The electron multiplication type CCD image pickup device has a very large white defect at the time of electron multiplication. Therefore, not only the video signal of the horizontal scanning period output from the effective pixels on the light receiving surface of the CCD image sensor, but also an average of about 20 horizontal light-shielding pixels (H-OB) that serve as the reference potential of the video during each horizontal scanning period. The value becomes unstable due to white scratches.
Therefore, from the Nth lower limit of the signal output from the light-shielded pixel acquired by the third acquisition unit that acquires the signal output from at least one light-shielded pixel on the left or right of the light receiving surface of the CCD image sensor. By taking an average value up to the (N + M) th, a second representative value that is not affected by white scratches is calculated.

Nevertheless, at the upper end (Top V) portion of the screen where the vertical blanking period ends and the vertical video period starts, each power supply voltage and the GND potential fluctuate, and the second representative value also fluctuates.
Therefore, in the vertical scanning period corresponding to the upper end portion of the screen where the vertical blanking period ends and the vertical video period starts, the second representative value of the signal output from the shielded pixel acquired by the third acquisition unit is A dark portion correction signal calculated by quadratic curve interpolation in the horizontal scanning period is subtracted from the second representative value from the video signal in the horizontal scanning period at the upper end portion of the screen to correct the Top V dark shading.

  Next, the embodiment shown in FIGS. 2C and 3C will be described. The difference between FIG. 2C and FIG. Instead of the AGC 50, there are comparison units 84 to 88, an average unit 81, a reference memory unit 82, and a quadratic curve interpolation average unit 83.

  2A is omitted, the operations of the comparison units 84 to 88, the averaging unit 81, the reference memory unit 82, and the quadratic curve interpolation averaging unit 83 are omitted. This will be described with reference to FIG. 3C.

  At 92, the values of the comparison units 84 to 88 are set to the upper limit value of the signal, the upper limit value is compared with the H-OB1 signal, and the smaller H-OB1 signal is stored in the comparison unit 88 as the minimum value signal.

  In 93, the minimum value signal and the H-OB2 signal are compared, the smaller one is stored in the comparison unit 88 as the minimum value signal, and the smaller one is compared with the upper limit value as the second smallest signal. Is stored in the comparator 87 as the second smallest signal.

  In 94, the minimum value signal is compared with the H-OB3 signal, the smaller one is stored in the comparator 88 as the minimum value signal, the larger one is compared with the second smallest signal, and the smaller one is second. The smaller signal is stored in the comparator 87, the larger signal is compared with the upper limit value as the third smallest signal, and the smaller signal is stored in the comparator 86 as the third smallest signal.

  95, the minimum value signal is compared with the H-OB4 signal, the smaller one is stored in the comparison unit 88 as the minimum value signal, the larger one is compared with the second smallest signal, and the smaller signal is second. Is stored in the comparator 87 as the smaller signal, the larger one is compared with the upper limit value as the third smallest signal, the smaller signal is stored in the comparator 86 as the third smaller signal, and the larger signal is fourth. The smaller signal is compared with the upper limit value as a small signal, and the smaller signal is stored in the comparator 85 as the fourth smallest signal.

  In 96, the minimum value signal is compared with the H-OB5 signal, the smaller one is stored in the comparison unit 88 as the minimum value signal, the larger one is compared with the second smallest signal, and the smaller one is second. Is stored in the comparator 87 as the smaller signal, the larger one is compared with the upper limit value as the third smallest signal, the smaller signal is stored in the comparator 86 as the third smaller signal, and the larger signal is fourth. The smaller signal is compared with the upper limit value as a small signal, and the smaller signal is stored in the comparator 85 as the fourth smallest signal, and the smaller signal is compared with the upper limit value as the fifth smallest signal and the smaller signal is the fifth smallest signal. Is stored in the comparison unit 84.

  In 97, the minimum value signal and the H-OBN signal are compared, the smaller one is stored as the minimum value signal in the comparison unit 88, the larger one is compared with the second smallest signal, and the smaller one is second. Is stored in the comparator 87 as the smaller signal, the larger one is compared with the upper limit value as the third smallest signal, the smaller signal is stored in the comparator 86 as the third smaller signal, and the larger signal is fourth. The smaller signal is compared with the upper limit value as a small signal, and the smaller signal is stored in the comparator 85 as the fourth smallest signal, and the smaller signal is compared with the upper limit value as the fifth smallest signal and the smaller signal is the fifth smallest signal. Is stored in the comparison unit 84.

  At 98, the third smallest signal, the fourth smallest signal, and the fifth smallest signal are averaged by the averaging unit 81 and stored in the storage unit 82.

99, the quadratic curve correction unit 83
Hdn = Hn * (5/8) + Hn + 1 * (5/8) −Hn-1 * (1/8) −Hn + 2 * (1/8)
And the second-order curve correction average signal is used as the H-OB representative value signal for dark current correction

  As described above, according to the third embodiment of the present invention, the dark portion unevenness (dark shading) of the portion where the vertical video period starts at the high electron multiplication factor of the electron multiplying CCD image pickup device corresponds to the change of the electron multiplication factor. Even in the case of EM-CCD H-OBs that not only can be corrected, but also increase in the dark current level in proportion to the electron multiplication factor, the influence of pixels called white scratches with an abnormally high dark current level is also caused by dark current. The influence of pixels called black scratches with an abnormally low level can be made almost unaffected by spiked or ringing diving noise.

1: imaging device, 2: optical system, 11: color separation optical system, 3, 7, 9: CCD imaging device,
4, 10, 12: FEP, 5: Video signal processing unit including a multiplication detection processing unit, 6: CPU,
8: Temperature sensor, 13: Vertical transfer driver (w / TG), 14, 15, 16: CMG driver,
17: Cooling unit, 18: Detection unit, 19, 46, 57: Subtractor, 45: Adder, 51: Divider
52: Multiplier, 47, 68, 69, 81: Average part, 43, 44: Line memory part,
48, 82: reference memory unit, 83: quadratic curve interpolation average unit, 50: D.D. AGC,
49: Image memory unit, 41, 42, 53 to 56, 84 to 88: Comparison unit,
401: CDS, 402: AGC unit, 403: ADC, 404: TG,

Claims (4)

  In an imaging apparatus using an electron multiplying CCD image sensor, an electron multiplying factor of the electron multiplying CCD image sensor is calculated, and a vertical blanking period ends in conjunction with the calculated electron multiplying factor. The screen top edge correction signal obtained by multiplying the screen top edge non-uniformity signal (shading) at the screen top edge (Top V) where the start of the image is prepared in advance with the calculated electronic multiplication factor. An imaging method comprising: subtracting from a video signal in a horizontal scanning period to correct the video signal.   Electron multiplication type CCD image pickup device, temperature detection means for the image pickup device of the CCD image pickup device, drive means for the electron multiplying electrode of the CCD image pickup device, dark portion correction unit for correcting dark portion unevenness, high electron multiplication factor and incident light quantity In an imaging apparatus having a means for calculating an integral amount of a product of and calculating an approximated electron multiplication factor from the calculated integral amount, the imaging device has a positive correlation (proportional to the electronic multiplication factor) The dark portion unevenness of the video signal in the horizontal scanning period at the upper end portion of the screen at the end of the vertical blanking period and the start of the vertical video period is multiplied by the calculated electronic multiplication factor by the dark portion correction unit. A color solid-state imaging device, comprising: subtracting the screen upper end correction signal obtained from the image signal of the horizontal scanning period at the upper end portion of the screen.   An electron multiplying CCD image sensor, a first acquisition unit that acquires an image signal output from an effective pixel on the light receiving surface of the CCD image sensor, and at least one of the upper and lower portions of the light receiving surface of the CCD image sensor are shielded from light In the imaging apparatus having the second acquisition unit that acquires the signal output from the pixel, the center of the signal output from the left and right (H-OB of V-OB) of the shielded pixel acquired by the second acquisition unit Means for calculating a first representative value (electron-multiplied dark current amount) such as an average value in the vicinity, and a reference value (reference dark current amount) of the first representative value when each temperature is not multiplied Is obtained by multiplying the average of the ratio between the reference value and the first representative value (electron multiplication factor) over 3 vertical periods by the non-uniformity at the top edge of the screen at the time of electron multiplication. An image pickup apparatus characterized by subtracting the screen upper end correction signal from the video signal in the horizontal scanning period. .   An electron multiplying CCD image sensor, a first acquisition unit that acquires an image signal output from an effective pixel on the light receiving surface of the CCD image sensor, and at least one of the left and right sides of the light receiving surface of the CCD image sensor are shielded from light A third acquisition unit that acquires a signal output from the pixel, and the signal output from the light-shielded pixel acquired by the third acquisition unit (such as an average value from the lower limit Nth to N + Mth) ) Means for calculating a second representative value, and at least in the vertical scanning period corresponding to the upper end portion of the screen where the vertical blanking period ends and the vertical video period starts, the light shielding acquired by the third acquisition unit is performed. Subtract the second representative value of the signal output from the pixel by performing quadratic curve interpolation in the horizontal scanning period, and subtract the second representative value from the video signal in the horizontal scanning period at the upper end of the screen. Features to do Imaging device for.

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