WO2018142555A1 - Image pickup device - Google Patents

Abstract

The purpose of the present invention is to correct dark current irregularity, so-called fixed pattern noise, in an image pickup element, the dark current fluctuating due to the temperature of the image pickup element, and to perform such correction immediately after startup and in a short amount of time. An image pickup device (30) includes: a temperature sensor (20); peripheral-temperature sensor (20a); a motor fan (74); a heat-dissipating fin (73); a Peltier element (71) which is between an image pickup element (70) and the heat-dissipating fin (73); a Peltier driving circuit (72) for driving the Peltier element (71); a light blocking means for, for example, an electric filter disk wheel or aperture of the lens (71); and a white-flaw and absolute black-flaw detection and interpolation unit (38) that reads and stores a fixed pattern signal for which an OB pixel model-value was subtracted from an effective pixel image-pickup signal at the time of image pickup, and that subtracts the stored fixed pattern signal from the image signal for which the OB pixel model-value was subtracted from the effective pixel image pickup signal at the time of image pickup.

Description

Imaging device

The present invention relates to an imaging apparatus such as a television camera, and more particularly to an imaging apparatus having a fixed pattern correction function of an imaging element.

Noise included in a video signal from an imaging device (also referred to as “imaging signal”) includes random noise that varies with time and fixed pattern noise (FPN) that does not vary with time. The FPN can be removed or suppressed by signal processing based on its regularity.

In general, in an image pickup device, the dark current becomes about twice as the temperature rises by 6 ° C., and fluctuates in proportion to an exponential function of the image pickup device temperature. However, in order to specialize in high pixels, high sensitivity, and high-speed readout, there is also a CMOS image sensor in which dark current changes with temperature in a nonlinear manner (see, for example, Patent Document 1). In addition, there is a CMOS image sensor in which dark current varies nonuniformly in a screen according to nonlinearity with temperature. For this reason, it may be difficult to store the FPN as a correction value from the video signal when the CMOS image sensor is shielded at a high temperature, and calculate and correct the FPN according to the temperature of the CMOS image sensor.

For this reason, the power supply is energized for about 30 minutes and heat-run, and the FPN correction unit of the image pickup apparatus extracts the FPN from the video signal at the time of shading and stores it as a correction value, and the correction value is obtained from the actual video signal. The corrected video signal from which the FPN has been removed is output by subtraction. Furthermore, there is a technique for removing both dark FPN and bright FPN from a video signal (see, for example, Patent Document 2). In other words, in the conventional UHDTV8K (effective pixel number 7680H × 4320V) camera, after a heat run of 30 minutes, a fixed pattern signal obtained by subtracting the OB pixel typical value from the effective pixel imaging signal is read and stored, and the OB is acquired from the effective pixel imaging signal at the time of imaging. It was subtracted from the video signal from which the pixel typical value was subtracted.

In addition, a production camera using an image pickup tube having an avalanche multiplication photoelectric conversion film has a drive circuit for energizing and driving the Peltier element in both positive and negative directions, even at ultra-low temperatures where the operation of the avalanche multiplication photoelectric conversion film becomes unstable. There is a technique for performing control so that photographing is possible (see, for example, Patent Document 3). Furthermore, when the avalanche multiplication is performed at a high temperature at which a flaw that causes a saturation signal current to gradually grow in the screen of the avalanche multiplication photoelectric conversion film, the operation voltage is reduced to a simple photoelectric conversion operation without avalanche multiplication. High sensitivity photography was possible about 3 seconds after the start of the avalanche multiplication photoelectric conversion film cooling down to the temperature at which the Peltier cooling became effective and the avalanche multiplication could be stably performed in the sensitivity photography state.

JP 2009-100300 A Japanese Patent Laying-Open No. 2015-100099 JP-A-5-316407

By the way, if the broadcasting camera using the imaging tube having the avalanche multiplication photoelectric conversion film described above is in a state called preheating or standby in which only the heater of the electron gun of the imaging tube is energized, the avalanche multiplication is performed. Knowing that the photoelectric conversion film was gradually broken, high-sensitivity photography by avalanche multiplication was possible immediately after startup before Peltier cooling became effective.
As described above, in many cases, broadcasting cameras are required to be able to shoot immediately after activation, and a countermeasure technique has been demanded.

The present invention has been made in view of such a situation, and aims to solve the above problems.

According to the present invention, an imaging apparatus includes a solid-state imaging device, a solid-state imaging device temperature detection unit that detects a temperature of the solid-state imaging device, a casing outer peripheral temperature detection unit that detects an ambient temperature outside the casing, and the solid-state imaging device. A Peltier element attached to the fan, a ventilation fan that encourages the flow of air in and out of the housing,
A heat dissipation fin attached to the Peltier element, a Peltier element driving circuit for driving the Peltier element, a light shielding means for blocking light to the solid-state imaging element, and a fixed value obtained by subtracting the OB pixel typical value from the effective pixel imaging signal Image processing means for reading and storing a pattern signal, performing OB correction processing for subtracting the stored fixed pattern signal from a video signal obtained by subtracting an OB pixel typical value from an effective pixel imaging signal at the time of imaging, and a temperature of the imaging device A control unit for controlling, the control unit starts light shielding of the light shielding means at the time of startup, stops the ventilation fan, the Peltier element drive circuit, the ambient temperature and the imaging device Pulse driving is executed at a first time corresponding to the difference from the temperature, and then a current is passed through the Peltier element at a second time longer than the first time. If the temperature difference between the ambient temperature and the temperature of the solid-state imaging device falls within a predetermined temperature range by controlling the state to the second time state, the control unit The fan is controlled to a normal drive corresponding to the temperature of the solid-state image sensor, and the Peltier device drive circuit is controlled to a normal drive corresponding to the temperature of the solid-state image sensor, and the image processing unit performs the OB correction Execute the process.
Another imaging device of the present invention includes a solid-state imaging device, a solid-state imaging device temperature detecting unit that detects a temperature of the solid-state imaging device, a casing outer periphery temperature detecting unit that detects an ambient temperature outside the casing, and the solid-state imaging A Peltier element attached to the element, a ventilation fan for urging air in and out of the housing, a heat dissipating fin attached to the Peltier element, a Peltier element driving circuit for driving the Peltier element, and the solid-state imaging element A light-shielding means that shields light from the light source, a fixed pattern signal obtained by subtracting the OB pixel typical value from the effective pixel imaging signal, and storing it, and the video signal obtained by subtracting the OB pixel typical value from the effective pixel imaging signal at the time of imaging. An image processing unit that performs an OB correction process for subtracting the stored fixed pattern signal; and a control unit that controls the temperature of the imaging device. The light shielding means starts light shielding, the ventilation fan is stopped, and the Peltier element driving circuit is cooled in the first time according to the difference between the ambient temperature and the temperature of the imaging element. Pulse driving is performed, and then, in a second time longer than the first time, control is performed so that no current flows through the Peltier element, and control is performed in the second time state. When the temperature difference between the ambient temperature and the temperature of the solid-state image sensor is within a predetermined temperature range, the control unit controls the ventilation fan to a normal drive corresponding to the temperature of the solid-state image sensor, The Peltier device driving circuit is controlled to a normal driving corresponding to the temperature of the solid-state imaging device, the image processing unit executes the OB correction processing, and the first time is 0.001 second to 0.00. 1 second A range, wherein the second time is in the range of 1 second to 3 seconds.
Still another image pickup apparatus according to the present invention is attached to the solid-state image pickup device, a solid-state image pickup device temperature detection means for detecting the temperature of the solid-state image pickup device, a casing outer periphery temperature detection means for detecting an ambient temperature outside the case, and the solid-state image pickup device. A Peltier element, a ventilation fan for energizing air in and out of the housing, a heat dissipating fin attached to the Peltier element, a Peltier element driving circuit for driving the Peltier element, and light to the solid-state imaging element A light shielding means for shielding light, and a fixed pattern signal obtained by subtracting the OB pixel typical value from the effective pixel imaging signal is read and stored, and the stored fixed pattern is obtained from the video signal obtained by subtracting the OB pixel typical value from the effective pixel imaging signal at the time of imaging. An image processing unit that performs OB correction processing for subtracting a signal, and a control unit that controls the temperature of the imaging element, and the control unit is configured to block the light-shielding hand when activated. The ventilation fan is stopped, the Peltier element drive circuit is pulsed positively and negatively, and the pulse drive is performed positively and negatively at a time ratio that is the inverse of the voltage ratio of the positive and negative power supply voltage of the Peltier element drive circuit. Then, the solid-state imaging device and the heat radiation fin are heated so that there is no temperature difference between both surfaces of the Peltier device, and when the temperature difference between the ambient temperature and the temperature of the solid-state imaging device is within a predetermined temperature range, The ventilation fan is controlled to a normal operation corresponding to the temperature of the solid-state image sensor, and the Peltier element drive circuit is controlled to a normal drive corresponding to the temperature of the solid-state image sensor, and the image processing unit is OB correction processing is executed.

According to the present invention, a change in so-called fixed pattern noise, such as non-uniformity in dark current of an image sensor that varies non-linearly in a screen in a non-linear manner with respect to the temperature of the solid-state image sensor, is detected immediately after activation (for example, from about 1 second to about 3 Seconds), the fixed pattern noise component is detected and corrected by subtracting the fixed pattern noise component at the time of shooting to obtain a high-quality shooting without fixed pattern noise component (previously, about 30 minutes after startup) Time) can be greatly reduced.

1 is a block diagram illustrating an overall configuration of an imaging apparatus according to an embodiment of the present invention. It is a block diagram which shows the structure of the white flaw detection interpolation part based on embodiment of this invention. It is a block diagram which shows the structure of the complete black flaw detection interpolation part based on embodiment of this invention. It is a schematic diagram in the case of interpolating with the median value of 8 pixels around a complete black defect before OB correction at the time of light shielding according to the embodiment of the present invention. It is a schematic diagram in the case of interpolating with the median value of 8 pixels around a complete black defect before OB correction at the time of light shielding according to the embodiment of the present invention. It is a schematic diagram of the interpolation in the case of using the median value of 8 pixels around the white defect in the imaging signal before OB correction at the time of light shielding according to the embodiment of the present invention. It is a schematic diagram in the case of interpolating with a median value of 8 pixels around a white defect in an imaging signal before OB correction at the time of light shielding according to an embodiment of the present invention. It is a block diagram which shows the structure of the white defect surrounding pixel interpolation part based on embodiment of this invention. It is a block diagram which shows the structure of the black crack surrounding pixel interpolation part based on embodiment of this invention. It is a block diagram which shows the structure of the dark current calculation OB correction | amendment part based on embodiment of this invention. It is a block diagram which shows the structure of the FPN correction | amendment part based on embodiment of this invention. It is a block diagram of the Peltier device drive circuit concerning Example 1 of an embodiment of the present invention. It is a figure which shows the example of a drive of the Peltier device 71 using the Peltier drive circuit based on Example 1 of embodiment of this invention. It is a figure which shows another example of a drive of the Peltier device using the Peltier drive circuit based on Example 1 of embodiment of this invention. It is a flowchart of the FPN detection after a short time FPN change reduction by the image sensor heating by the pulse drive at the time of starting based on Example 1 of the embodiment of the present invention. It is a flowchart of the FPN correction | amendment at the time of imaging based on Example 1 of embodiment of this invention. It is a block diagram of the Peltier drive circuit based on Example 2 of the embodiment of the present invention. The Peltier device using the Peltier drive circuit according to Example 2 of the embodiment of the present invention

Next, modes for carrying out the present invention (hereinafter simply referred to as “embodiments”) will be specifically described with reference to the drawings. In this embodiment, the so-called fixed pattern noise, which is dark current unevenness of the image sensor that fluctuates with the temperature of the image sensor (solid-state image sensor), is detected in a short time immediately after startup, and is displayed nonlinearly with respect to the temperature. An image sensor having a fixed pattern noise that varies non-uniformly within 30 minutes after the start-up, when the internal temperature rise approaches saturation and the change becomes small, the fixed pattern noise is detected and photographed. Instead of correcting, the fixed pattern noise is corrected by detecting a change in the fixed pattern noise close to saturation immediately after the startup.

FIG. 1 is a block diagram showing the overall configuration of the imaging apparatus 30 of the present embodiment, for example, a television camera. The image pickup apparatus 30 in FIG. 1 mainly shows the function of video signal processing of a post-gamma matrix. The image pickup apparatus 30 includes a CMOS image pickup device (solid-state image pickup device) in which AFE (analog front end) for noise reduction, gain correction, and analog-digital conversion is integrated. OB correction is performed to subtract the value from the effective pixel video signal.

More specifically, the image pickup apparatus 30 includes a CMOS image pickup device with an on-chip color filter (hereinafter referred to as “image pickup device 70”), a video signal processing unit 35 with a white flaw complete black flaw detection interpolation function, a parallel- A serial conversion unit 37 and a CPU (Central Processing Unit) 39 are provided.

Further, the imaging device 30 includes a Peltier element 71, a Peltier drive circuit 72, a heat radiation fin 73, a motor fan 74, a motor fan drive circuit 75, a temperature sensor 20, and an ambient temperature sensor 20a, and realizes a cooling function of the image sensor 70. To do. The motor fan 74 is controlled to be driven by a motor fan drive circuit 75 and operates to encourage air to flow in and out of the housing. A lens 31 and a viewfinder 40 are attached to the imaging device 30.

The image sensor 70 outputs an R / G / B signal, but here includes a Bayer color filter and outputs G1 and G2 signals as G signals. That is, an R / G1 / G2 / B signal is output. When the signals G1 and G2 are not distinguished, “G1” and “G2” are described and described as “G”.

The video signal processing unit with white flaw complete black flaw detection interpolation function 35 includes a white flaw complete black flaw detection interpolation unit, a gamma color outline correction 53, and a MATRIX unit. The white defect complete black defect detection interpolation unit 38 includes a white defect detection interpolation unit 50, a complete black defect detection interpolation unit 51, a dark current calculation OB correction unit 52, and an image sensor control unit 54.

The function of each component will be specifically described together with the signal flow.
Incident light from the subject is imaged by the lens unit 31, and the imaged incident light is photoelectrically converted by the imaging element 70 of the imaging device 30. The R / G1 / G2 / B signal photoelectrically converted by the image sensor 70 is subjected to noise reduction, gain correction and analog-digital conversion in the image sensor 70, and the converted signal is completely black with white flaws. It is sent to the video signal processing unit 35 with a flaw detection correction function. The video signal processing unit with white flaw / black flaw detection / interpolation function 35 performs various video signal processing such as color correction, contour correction, gamma correction, and knee correction.

The temperature sensor 20 is provided in the vicinity of the image sensor 70 and detects the temperature of the image sensor 70. The ambient temperature sensor 20 a is a casing outer periphery temperature detection unit, and detects a temperature near the outside of the casing of the imaging device 30. The ambient temperature sensor 20a may be externally attached to the imaging device 30 and notify the imaging device 30 of a measurement result by wired or wireless connection.

The CPU 39 drives the Peltier element 71 and the motor fan 74 based on the temperature of the image sensor 70 to cool or heat the image sensor 70. Specifically, the CPU 39 instructs the Peltier drive circuit 72 to drive the Peltier element 71. In addition, the CPU 39 instructs the motor fan drive circuit 75 to drive the motor fan 74 and controls the temperature of the radiating fins 73 to approach a desired temperature, for example, the ambient temperature.

The image sensor control unit 54 controls accumulation and reading of the image sensor 70 in accordance with instructions from the CPU 39. The lens unit 31 controls light shielding or standard imaging with an optical aperture or variable optical attenuation (hereinafter referred to as “aperture”) in accordance with an instruction from the CPU 39.

When the image pickup apparatus 30 is activated, the aperture of the lens 31 is closed to block light, the motor fan 74 is stopped and the Peltier drive circuit 72 is pulse-driven, and the temperature difference between the ambient temperature and the temperature of the image pickup element 70 is the image pickup element 70. And the heat radiation fin 73 are controlled to approach a temperature difference of saturation (specifically, thermal resistance and heat capacity saturation).

When the saturation temperature difference is approached, the drive of the Peltier element 71 and the drive of the motor fan 74 are shifted to a normal operation corresponding to the temperature of the image sensor 70. Thereafter, a fixed pattern signal obtained by subtracting the OB pixel typical value from the effective pixel imaging signal 64 times (about 1 second) is read and stored, and the OB pixel typical value is subtracted from the video signal from the effective pixel imaging signal at the time of imaging, Further, the fixed pattern signal is subtracted. Details will be described later in Example 1 and Example 2.

The video signal processing unit with white flaw complete black flaw detection interpolation function performs various video signal processing and the like, and then uses the MATRIX unit 36 to convert the BT. The R / G / B output of the video signal 709 is converted into a luminance signal (Y) and a color difference signal (Pb / Pr).
Y = 0.2126R + 0.7152G + 0.0722B
Pb = 0.5389 (BY)
Pr = 0.6350 (RY)
Then, it is converted into a serial video signal by the parallel-serial converter 37 and output to the outside.

BT. ITU / BT.709, which has a wider color gamut than 709 primary color points. Video signal output at 2020 Y = 0.2627R + 0.6780G + 0.0593B
Pb = 0.5315 (BY)
Pr = 0.67882 (RY)
There is also a video signal output.
Further, the output of red, green and blue primary color video signals is not shown, but there is also the output of red, green, green and blue primary color video signals.

The CPU 39 controls each unit of the imaging device 30. Further, the image display unit of the viewfinder 40 or the monitor display (not shown) has a setting menu of the imaging device 30, an imaging pixel (hereinafter referred to as “white scratch”), a normal pixel, and a sensitivity with an abnormally large dark current. Displays an automatic interpolation operation with an imaging pixel (hereinafter referred to as a “complete black flaw”) that has an abnormally low dark current and a leakage current level, or an arbitrary pixel manual interpolation operation with surrounding pixels.

In the viewfinder 40 or monitor display, the menu screen is superimposed on the subject image, and the user can automatically detect white scratches and complete black scratches while looking at the menu screen, or manually interpolate any pixel at surrounding pixels. Display operations.

Hereinafter, the basic configuration and operation regarding the flaw detection and the interpolation processing will be described with reference to FIG. 1, FIG. 2 to FIG. 10, and FIG.

FIG. 2 is a block diagram showing the configuration of the white flaw detection interpolation unit 50. FIG. 3 is a block diagram showing the configuration of the complete black defect detection interpolation unit 51. As shown in FIG. The white defect detection interpolation unit 50 shown in FIG. 2 detects and interpolates an imaging pixel (so-called “white defect”) with an abnormally large dark current. The complete black flaw detection interpolating unit 51 in FIG. 3 detects an image pickup pixel (so-called “complete black flaw”) whose sensitivity is abnormally low and the dark current is only about the leakage current.

Specifically, the white flaw detection interpolation unit 50 acquires an R / G / B signal from the image sensor 70, performs white flaw detection interpolation processing, and performs a white flaw interpolation signal R (1) / G white flaw. The white defect interpolation signal B (1) of the interpolation signal G (1) / B is output to the complete black defect detection interpolation unit 51.

The complete black defect detection interpolation unit 51 obtains the white defect interpolation signal R (1) / G white defect interpolation signal G (1) / B white defect interpolation signal B (1) from the white defect detection interpolation unit 50. Then, complete black defect detection interpolation processing is performed, and the complete black defect interpolation signal R (2) / G complete black defect interpolation signal G (2) / B complete black defect interpolation signal B (2) is calculated as a dark current OB. Output to the correction unit 52.

At this time, the complete black defect detection interpolation unit 51 subtracts the complete black defect reference level in the long-time accumulation of complete black defect detection, determines the video signal timing (address) of the complete black defect, Interpolation is performed at surrounding pixels of the complete black defect at the video signal timing (address) of the complete black defect without determining the complete black defect interpolation level at the time of imaging.

As shown in FIG. 2, the white defect detection interpolation unit 50 includes a white defect determination unit 15, a white defect surrounding pixel interpolation unit 16, three subtractors (subtracter (1) 12a, subtracter (2) 13a, Subtractor (3) 14a).

The white scratch determination unit 15 performs white scratch video signal timing (address) determination and white scratch interpolation determination during standard imaging, and white scratch video signal timing (address) Twr corresponding to the R / G / B signal. Twg and Twb are output to the white defect surrounding pixel interpolating unit 16. In addition, when not distinguishing the video signal timing (address) Twr, Twg, and Twb of each white defect, it will be described as the video signal timing (address) Tw of the white defect. The white defect surrounding pixel interpolating unit 16 performs interpolation at the surrounding pixels of the white defect.

As shown in FIG. 3, the complete black defect detection interpolation unit 51 includes a black defect determination unit 17, a black defect surrounding pixel interpolation unit 18, and three subtractors (subtracter (1) 12b, subtracter (2) 13b. And a subtractor (3) 14b).

The black scratch determination unit 17 performs black scratch video signal timing (address) determination, and black scratch video signal timing (address) Tbr, Tbg, Tbb corresponding to the R / G / B signal is interpolated around the black scratch. To the unit 18. In addition, when not distinguishing the video signal timing (address) Tbr, Tbg, and Tbb of each black scratch, it is referred to as the video signal timing (address) Tb of the black scratch. The black scratch surrounding pixel interpolating unit 18 performs interpolation at the black scratch surrounding pixels.

As shown in FIGS. 1, 2, and 3, the CPU 39 instructs the lens 31 to close the aperture and shield the image sensor 70. Next, the CPU 39 instructs the image sensor control unit 54 to store approximately 1 second in the middle time. Based on the instruction, the image sensor control 54 generates a white flaw detection intermediate time intermittent pulse and supplies it to the image sensor 70. Then, the subtractor (1) 12a, subtracter (2) 13a, and subtracter (3) 14a of the white flaw detection interpolating unit 50 are used to detect R, G, and B image signals accumulated during the light-shielding time and white flaw detection. The difference from the white scratch reference level (SR1, SG1, SB1) in the time accumulation is output to the white scratch determination unit 15. The white scratch reference level (SR1, SG1, SB1) is output from the CPU 39. The white flaw determination unit 15 performs white flaw video signal timing (address) determination from the difference.

Next, the CPU 39 instructs the image sensor control unit 54 to store for a long time (from 1 second to 163894 seconds) in inverse proportion to the dark current of the normal pixels. The image sensor control 54 generates a complete black flaw detection long-term intermittent pulse based on the instruction and supplies it to the image sensor 70. Then, the subtractor (1) 12b, subtracter (2) 13b, and subtracter (3) 14b of the complete black defect detection interpolation unit 51 uses the white, flawed, R, G, and B image signals accumulated for a long period of time as shading. R, G, B interpolation signals (R (1), G (1), B (1)) interpolated at surrounding pixels of white scratches at 16 based on signal timing (address) and complete black scratch detection The difference from the complete black scratch reference level (SR2, SG2, SB2) in the long-time accumulation is output to the black scratch determination unit 17. The black scratch determination unit 17 determines the video signal timing (address) of the complete black scratch from the difference.

At the time of standard imaging, the CPU 39 causes the lens 31 to open the aperture and instructs the image sensor control unit 54 to perform standard imaging. Based on the instruction, the image sensor control 54 generates a standard imaging pulse and supplies it to the image sensor 70. The subtractor (1) 12a, subtracter (2) 13a, and subtracter (3) 14a of the white flaw detection interpolation unit 50 perform standard imaging R, G, B imaging signals and white flaw interpolation level ( SR1 ′, SG1 ′, and SB1 ′) are output to the white scratch determination unit 15. The white flaw determination unit 15 performs white flaw video signal timing (address) determination from the difference. The white defect surrounding pixel interpolating unit 16 performs interpolation on the surrounding pixels of the white defect at the image signal timing (address) of the white defect with the imaging signal equal to or lower than the white defect interpolation level. R, G, B interpolation signals (R (1), G (1), B (1)) interpolated by surrounding pixels of white flaws by white flaw surrounding pixel interpolation unit 16 are complete black flaw detection interpolating units. 51 is output. The black defect surrounding pixel interpolation unit 18 of the complete black defect detection interpolation unit 51 interpolates the complete black defect with the median value of the surrounding pixels based on the video signal timing (address) of the complete black defect. The black scratch determination unit 17 does not perform complete black scratch interpolation level determination during standard imaging.

Further, in FIG. 2, with respect to the determination level, the white scratch reference level (SR1, SG1, SB1) during white scratch detection medium time accumulation or the white scratch interpolation level (SR1 ′, SG1 ′, SB1 ′) during standard imaging is shown. The white scratch video signal timing (address) determination and the white scratch interpolation determination at the time of standard imaging can be performed by the same means (white scratch determination unit 15), and the circuit can be downsized and the price can be reduced. realizable.

FIG. 4A is a schematic diagram in the case of interpolating with the median value of 8 pixels around a complete black defect before OB correction at the time of light shielding, and shows interpolation at normal pixels around the complete black defect with a standard imaging signal. . As shown in the figure, the complete black scratch imaging signal “0” at the center becomes the surrounding normal pixel imaging signals “32”, “48”, “56”, “64”, “80”, “96”, “102”. ”And“ 128 ”are interpolated by the median“ 64 ”or“ 80 ”.

FIG. 4B is a schematic diagram in the case of interpolating with the median value of 8 pixels around the complete black defect before OB correction at the time of light shielding, and interpolation at normal pixels including the surrounding black defect of the complete black defect in the standard imaging signal. Is shown. As shown in the figure, the surrounding complete normal pixel imaging signal “32”, “48” except for the complete black scratch imaging signal “0” in the center (lower right of the matrix in the figure) is the central perfect black scratch imaging signal “0”. , “56”, “64”, “80”, “102”, “128” are interpolated by the median “64”.

FIG. 4C is a schematic diagram in the case of interpolating with the median value of 8 pixels around the white defect in the image signal before OB correction at the time of light shielding, and an example of interpolation at normal pixels around the white defect in the standard image signal Is shown. As shown in the figure, the center white scratch imaging signal “1024” is converted into the surrounding normal pixel imaging signals “32”, “48”, “56”, “64”, “80”, “96”, “102”. , “128” is interpolated with the median “64” or “80”.

FIG. 4D is a schematic diagram in the case of interpolating with a median value of 8 pixels around white flaws in the image signal before OB correction at the time of light shielding, and is a normal pixel including white flaws around white flaws in the standard image pickup signal. An example of interpolation is shown. As shown in the figure, the white scratch imaging signal “1024” at the center becomes the surrounding normal pixel imaging signals “32”, “48”, “56”, “80”, “96”, “102”, “128”. Is interpolated with a median of “80”. Complete black scratch interpolation is performed after white scratch interpolation.

FIG. 5 is a block diagram showing the configuration of the white flaw surrounding pixel interpolation unit 16. FIG. 6 is a block diagram showing the configuration of the black defect surrounding pixel interpolation unit 18. The white defect surrounding pixel interpolation unit 16 and the black defect surrounding pixel interpolation unit 18 have the same configuration, and each calculates and interpolates the median value of the surrounding eight pixels.

As shown in FIG. 5, the white defect surrounding pixel interpolation unit 16 includes a surrounding pixel signal selection unit 9a, a surrounding pixel median value detection unit 19a, a delay unit 8a, and an output switch 29a. The peripheral pixel signal selection unit 9a includes a line memory (1) 5a, a line memory (2) 6a, and an input switch 7a. The surrounding pixel median value detection unit 19a includes eight comparators (comparator (1) 21a to comparator (8) 28a) and outputs the surrounding pixel median value to the output switch 29a. The line memory (1) 5a and the line memory (2) 6a generate imaging signals at addresses 1H and 2H from the imaging signal at address 0H.

The input switch 7a selects the image signals at addresses 0H, 1H, and 2H, and generates surrounding pixel signals of the image signals. A frame memory (not shown) may be used in place of the line memory (1) 5a and the line memory (2) 6a. The delay unit 8a delays the imaging signal by the delay of the surrounding pixel median value detection unit 19a.

Then, the surrounding pixel median value detection unit 19a rearranges the surrounding pixel signals of the imaging signal by the comparator (1) 21a to the comparator (8) 28a, for example, in descending order, and the comparator (4) corresponding to the median value. The median value of the surrounding pixels of the imaging signal is detected from 24a to the output switch 29a. Further, in the output selector 29 of the white scratch surrounding pixel interpolating unit 16 according to the video signal timing (address) Tw of the white scratch at the time of the determination below the white scratch level from the white scratch determining unit 15 shown in FIG. The imaging signal is interpolated to the median value of surrounding pixels of the imaging signal.

Also, as shown in FIG. 6, the flaw surrounding pixel interpolation unit 18 includes a surrounding pixel signal selection unit 9b, a surrounding pixel median value detection unit 19b, a delay unit 8b, and an output switch 29b. The peripheral pixel signal selection unit 9b includes a line memory (1) 5b, a line memory (2) 6b, and an input switch 7b. The surrounding pixel median value detection unit 19b includes eight comparators (comparator (1) 21b to comparator (8) 28b), and outputs the surrounding pixel median value. Line memory (1) 5b and line memory (2) 6b generate white scratch interpolation signals at addresses 1H and 2H from the white scratch interpolation signal at address 0H.

The input switch 7b selects the white scratch interpolation signal at addresses 0H, 1H, and 2H and generates a surrounding pixel signal of the white scratch interpolation signal. The delay unit 8b delays the white defect interpolation signal of the surrounding pixel median value detection unit 19b.

Then, the surrounding pixel median value detection unit 19b rearranges the surrounding pixel signals of the white defect interpolation signal by the comparator (1) 21b to the comparator (8) 28b, for example, in descending order, and the comparator (4 ) The surrounding pixel median value of the white scratch interpolation signal is detected from 24b to the output switch 29b. Further, in accordance with the video signal timing (address) Tb of the complete black scratch from the black scratch determination unit 17 of FIG. 3, the output switch 29b of the black scratch surrounding pixel interpolation unit 18 converts the white scratch interpolation signal into the white scratch interpolation signal. Interpolates to the surrounding pixel median.

In the white defect surrounding pixel interpolation unit 16 in FIG. 5 and the black defect surrounding pixel interpolation unit 18 in FIG. 6, even if there are a plurality of white defects in the surrounding pixels, complete black defect interpolation is performed after white defect interpolation. Full black scratch interpolation is not affected by white scratches. Further, since complete black defect interpolation is performed after white defect interpolation, the functions of the white defect surrounding pixel interpolation unit 16 and the black defect surrounding pixel interpolation unit 18 may be realized by switching the input signal and the control signal in the same circuit. Good.

FIG. 7 is a block diagram showing the configuration of the dark current calculation OB correction unit 52, which detects the Nth to N + Mth pixel values from the minimum value of the OB pixel signal as a representative value, and adds the average value of the representative values. Is output. Here, as an example, a configuration for outputting the addition average of the fourth to seventh pixel values (that is, N = 3, M = 4) from the minimum value is illustrated.

The dark current calculation OB correction 52 includes a representative value average detection unit 48, a delay unit 55, and a subtracter 4. The representative value average detection unit 48 includes a representative value detection unit 47, a ¼ division unit 46, an adder (1) 43, an adder (2) 44, and an adder (3) 45.

The representative value detection unit 47 obtains the OG pixel signal from the complete black defect detection interpolation unit 51, and the adder (1) 43, the adder (2) 44, and the adder (3) 45 are the fourth to fourth values from the minimum value. The seventh pixel value is added and output to the ¼ division unit 46.

Specifically, as shown in the figure, the representative value detection unit 47 includes comparators (1) 21c to (8) 28c. For example, the OG pixel values are rearranged in descending order, and the minimum value is the comparator ( 8) The maximum value (that is, the eighth pixel value from the minimum value) is set in the comparator (1) 21c in 28a. Here, the seventh pixel value from the comparator (2) 22c and the sixth pixel value from the comparator (3) 23c are output to the adder (1) 43. The fifth pixel value is output from the comparator (4) 24c, and the fourth pixel value is output from the comparator (5) 25c to the adder (2) 44. Then, the pixel value added by the adder (1) 43 and the pixel value added by the adder (2) 44 are further added by the adder (3) 45 and output to the ¼ division unit 46.

The ¼ division unit 46 obtains an addition value of the fourth to seventh pixel values (that is, N = 3, M = 4) from the minimum value from the adder (3) 45, and ¼ by the 2-bit shift. Turn into. By such processing, the representative value average detection unit 48 adds and averages the OB pixel signals excluding the white defect and the complete black defect.

Note that the imaging effective pixel signal delayed by the delay unit 55 is corrected by the addition average output from the representative value average detection unit 48 by the subtractor 4 and output as an OB corrected imaging pixel signal. In the V-OB correction (vertical OB correction), the delay unit 55 is not essential, but it is more stable that the imaging effective pixel signal is delayed by the delay unit 55 and corrected by the V-OB after the effective pixel. Note that the V-OB correction also serves as vertical stripe correction and HShading correction.

Generally, in a television camera to which the imaging device 30 is assumed to be applied, the number of OB pixels decreases as compared to effective pixels as the imaging element becomes a high pixel such as 2K, 4K, and 8K. Therefore, the OB pixel is easily affected by white scratches and complete black scratches. However, in this embodiment, without being affected by the white defect and the complete black defect of the OB pixel, for example, when the temperature of the image sensor 70 (hereinafter also referred to as “image sensor temperature”) rises by 6 ° C., it is approximately doubled. It is possible to detect the dark current of the normal pixel of the increasing OB pixel signal. As a result, the accumulation time can be made inversely proportional to the dark current of the detected normal pixel (approximately doubled when the temperature of the image sensor increases by 6 ° C.).

Also, if the dark current signal of the normal pixel of the detected OB pixel signal is subtracted from the imaging effective pixel signal, the OB correction is stably performed in the video signal processing without being affected by the white defect and the complete black defect of the OB pixel. As a result, the black color of the video signal becomes stable, and the wide dynamic range of the TV camera becomes easy.

By detecting the representative value of the OB pixel signal that increases approximately twice when the image sensor temperature rises by 6 ° C., the temperature of the image sensor can be detected without providing a separate temperature sensor. By making the accumulation time inversely proportional to the detected dark current of the normal pixel (which is approximately doubled at 6 ° C. at the image sensor temperature), the dark current of the normal pixel at low temperatures and the sensitivity are low. It is possible to reliably discriminate from the dark current of the abnormally low sensitivity pixel (hereinafter referred to as “complete black flaw”) that is abnormally low and has only a dark current corresponding to the leakage current, so that the complete black flaw can be reliably detected. Unlike white flaw detection, since it is difficult to detect a complete black flaw signal, accumulation for a long time during detection at a low temperature is allowed.

FIG. 8 is a block diagram showing a configuration of the FPN correction unit 80 applied to the imaging device 30 shown in FIG. The first imaging device calculates a one-frame addition average value of the video data input at the time of light shielding, and corrects sudden DC fluctuations by subtracting the one-frame addition average based on the calculated one-frame addition average value. The correction value can be calculated.

Specifically, as illustrated, the FPN correction unit 80 includes a black level subtractor 81, a memory controller 82, a frame memory 83, a one-frame addition average calculation unit 84, an adder 87, a line buffer ( 1) 88, a line buffer (2) 89, a divider 85, a subtracter (1) 86, and a subtracter (2) 90. The FPN correction unit 80 may be realized by, for example, an FPGA and a DDR memory, or may be realized by an FPGA having a large memory capacity.

The black level subtracter 81 subtracts the black reference level from the video signal at the time of shading in the correction value calculation process for calculating the cumulative correction value that is the basis of the correction value of the FPN correction. As a result, the FPN level reference is set to a digital value of zero.

The memory controller 82 controls data input / output with respect to the frame memory 83.
The frame memory 83 stores video data, and stores an area for storing video data for one frame at the time of shading input from the black level subtractor 81, and an area for storing a cumulative correction value for one frame. It has. Two memories, that is, a memory for input data and a memory for cumulative correction values may be provided.

The 1-frame addition average calculation unit 84 calculates the 1-frame addition average value by performing the addition average calculation of all pixels on the video data for one frame at the time of shading output from the black level subtractor 81. Specifically, the one-frame addition average calculation unit 84 cumulatively adds the input pixel data, adds one frame, and then divides by the total number of pixels to obtain the one-frame addition average value of the frame.

The adder 87 adds the accumulated correction value read from the frame memory 83 for each pixel.
The line buffer (1) 88 holds the output from the adder 87 for each row and outputs it to the memory controller 82 in units of rows. The line buffer (2) 89 holds the output for each row from the memory controller 82, outputs it to the adder 87 for each pixel, and outputs it to the divider 85.

The divider 85 divides the cumulative correction value read from the frame memory 83 by a predetermined number of additions (k times) for each pixel, calculates the average level of the video data at the time of light shielding, and The FPN correction value is output to the subtracter (1) 86.

A subtracter (1) 86 subtracts the FPN correction value from the divider 85 for each pixel from the video data input at the time of shooting after the correction value calculation processing is completed, and corrects the video data (corrected video data). ) Is output.

Examples 1 and 2 having the above-described configuration will be described below.
<Example 1>
As described above, in general, in an image sensor, the dark current is about twice as much as the temperature rises by 6 ° C. In a camera that is devised for heat dissipation, in general, the increase in the internal temperature decreases in about 30 minutes, and further, it is saturated in about 2 hours and is about 12 ° C. For this reason, even when the ambient temperature is constant, the internal temperature rise is 12 ° C., which is four times as high as the internal temperature rise when saturated, compared to the startup. However, in order to specialize in high pixels, high sensitivity, and high-speed readout, there are also CMOS image sensors in which dark current changes nonuniformly in the screen according to nonlinearity with temperature.

Hereinafter, Example 1 will be described with reference to the imaging device 30 of FIG. 1 described above and FIGS. 9, 10, 11, 12, and 13. FIG.

1 is stopped, the motor fan 74 is stopped and the Peltier driving circuit 72 is pulse-driven at the time of activation. When the temperature difference between the ambient temperature and the temperature of the image sensor 70 (image sensor temperature) approaches the temperature difference between the thermal resistance and the heat capacity of the image sensor 70 and the heat radiating fins 73, the driving of the Peltier element 71 and the motor fan 74 Drive is set to a normal operation corresponding to the image sensor temperature. Then, a fixed pattern signal obtained by subtracting the OB pixel typical value from the effective pixel imaging signal is read and stored only 64 times (about 1 second), and the OB pixel typical value is subtracted from the video signal from the effective pixel imaging signal at the time of imaging. Further, the fixed pattern signal is subtracted.

Here, FIG. 9 is a block diagram of the Peltier element driving circuit 72 of the first embodiment. The Peltier driving circuit 72 is a circuit example that realizes Peltier element driving in the positive direction (fin heating by imaging element cooling).

The Peltier drive circuit 72 includes an operational amplifier IC1 and a transistor Q1. The operational amplifier IC1 is, for example, a Rail-to-Rail operational amplifier for both input and output. Transistor Q1 is a PNP type. The collector terminal of the transistor Q1 is connected to one end of the Peltier element 71. The transistor Q1 may be a Pch MOSFET.

The positive power supply voltage Vcc is connected to the positive power supply terminal of the operational amplifier IC1 and the emitter terminal of the transistor Q1. The D / A output (Vin) of the CPU 39 is connected to the inverting input terminal of the operational amplifier IC1 through the resistor R2. The path between the resistor R2 and the inverting input terminal of the operational amplifier IC1 is grounded through the resistor R3.

The non-inverting input terminal of the operational amplifier IC1 is connected to the other end of the Peltier element 71, and a feedback signal from the Peltier element 71 is input. The path of the feedback signal is grounded through the resistor R1. The output of the operational amplifier IC1 is connected to the base terminal of the transistor Q1.

Here, the relationship between the D / A output (Vin) of the CPU 39 and the feedback voltage Vr from the resistor R1 is expressed by the following equation using the resistors R2 and R3.
Vr = Vin × R3 / (R2 + R3)
For example, assuming that the positive power supply voltage Vcc = + 12V, the resistance R1 = 0.1Ω, the resistance R2 = 47 kΩ, the resistance R3 = 1 kΩ, and Vin = 5V, the feedback voltage Vr is about 0.12V as shown in the following equation. It becomes.
Vr = 5 × 1.2 / 48.2≈0.12V
Here, the voltage across the Peltier element 71 is about 12V, and the current of the Peltier element is about 1.2A. When Vin is 0V, Vr = Vin × R3 / (R2 + R3) = 0V, the voltage across the Peltier element 71 is 0V, and the current of the Peltier element is 0A.

FIG. 10 is a diagram showing a driving example of the Peltier element 71 using the Peltier driving circuit 72 of FIG. It is an example of a two-time pulse of imaging element heating by pulse driving in a positive (final heating by imaging element cooling) direction. (A: upper stage) Transition of voltage between both ends of Peltier element 71 and current of Peltier element 71, (b: (Lower) The transition of the temperatures at both ends of the Peltier element 71 (imaging element temperature TS and fin temperature Tfin) is shown. Here, the relative temperature based on the ambient temperature Ta is shown.

In FIG. 10, the fin heating period is relatively short at 0.15 seconds for the first time when the image sensor is cooled. On the other hand, 0.85 seconds of non-drive is longer than or equal to the thermal time constant (usually 1 second or less) of the product of the thermal resistance of the Peltier device 71 and the heat capacity of the imaging device 70. During 0.85 seconds of non-drive, the heat of the fin heating reaches the image sensor 70 by heat conduction of the Peltier element 71, and the image sensor 70 is heated as a whole.

If the rise of the image sensor temperature Ts is not yet close to the thermal saturation equivalent to the Peltier weak cooling at the time of imaging, the period of the positive (fin heating by image sensor cooling) direction is 0.02 seconds for the second time. . On the other hand, the non-drive time is 0.98 seconds, and during the non-drive time of 0.98 seconds, the heat of the fin heating reaches the image pickup device 70 by the heat conduction of the Peltier device 71, and as a whole, the image pickup is performed. The element 70 is heated. When the light-shielding operation is completed and the temperature rise of the imaging device approaches the equivalent of thermal saturation during Peltier weak cooling during imaging, that is, within a predetermined temperature range, the PPN detection period is set to Peltier weak cooling during imaging. Then, the fixed pattern signal is calculated and stored by accumulating for about 1 second in the light-shielded state and subtracting the typical value of the dark current of the OB pixel.

FIG. 11 is a diagram showing another driving example of the Peltier element 71 using the Peltier driving circuit 72 of FIG. It is an example of a one-time pulse of imaging element heating by pulse driving in the positive direction (fin heating by imaging element cooling), (a) transition of the voltage across the Peltier element and current of the Peltier element, and (b) both ends of the Peltier element (imaging) The element temperature TS and the fin temperature Tfin) show the transition of temperature. Here, the relative temperature based on the ambient temperature Ta is shown.

In FIG. 11, the fin heating period is only once by cooling the image sensor and is relatively short, 0.17 seconds. On the other hand, 0.83 seconds of non-drive is longer than or equal to the thermal time constant (usually 1 second or less) of the product of the thermal resistance of the Peltier element 71 and the heat capacity of the image sensor 70. During this non-driven 0.83 seconds, the heat of the fin heating reaches the image sensor 70 by the heat conduction of the Peltier element 71, and the image sensor 70 is heated as a whole. When the light-shielding operation is completed and the temperature rise of the imaging device approaches the equivalent of thermal saturation during Peltier weak cooling during imaging, that is, within a predetermined temperature range, the PPN detection period is set to Peltier weak cooling during imaging. Then, the fixed pattern signal is calculated and stored by accumulating for about 1 second in the light-shielded state and subtracting the typical value of the dark current of the OB pixel.

For light shielding, the aperture of the lens 31 may be closed, or a light shielding filter with an electric filter disc wheel may be selected. However, the light shielding needs to be completed before the imaging element 70 is heated by driving the pulse of the Peltier element 71 to bring the temperature close to saturation of the internal temperature rise. 10 and 11, the light shielding operation may be performed at a general speed of about 1 second or less.

FIG. 12 is a flowchart of FPN detection after a short time FPN change reduction by image sensor heating by pulse drive at the time of activation. After startup, the motor fan 74 is stopped (S1), the ambient temperature Ta and the image sensor temperature Ts are measured (S2), and it is determined whether the temperature rise is equal to or higher than the saturation of cooling (S3).

If the temperature rise is less than the cooling saturation (N in S3), a process of driving the Peltier element 71 in accordance with the difference from the saturation is executed (S4), and the process returns to S2. If the temperature rise is equal to or higher than the saturation of cooling (Y in S3), DC driving for cooling (positive) the Peltier element 71 is performed according to the difference between the ambient temperature Ta and the imaging element temperature Ts (S5). Further, the motor fan 74 is driven according to the difference between the ambient temperature Ta and the image sensor temperature Ts (S6). For simplicity, the motor fan 74 may be simply driven. Subsequently, light shielding is performed (S7), and the FPN memory is cleared (S8).

Following clearing of the FPN memory, an all-pixel dark current detection process (S9) and an OB pixel typical dark current calculation process (S10) are performed, and the OB pixel typical dark current is subtracted from the effective pixel dark current to calculate an FPN component ( S11), the calculated FPN component is added to the FPN memory (S12). If the above process (S9-12) has not reached the 256th time (N in S13), the process returns to the all-pixel dark current detection process (S9). If it is the 256th time (Y in S103), the light shielding is stopped (S14), and the flow ends.

FIG. 13 is a flowchart of FPN correction during imaging. After the start of imaging, the ambient temperature Ta and the image sensor temperature Ts are measured (S101), and the direct current in the direction of the Peltier element 71 is positive (fin heating by image sensor cooling) according to the difference between the ambient temperature Ta and the image sensor temperature Ts. Driving is performed (S102). Further, fan driving is performed according to the difference between the ambient temperature Ta and the image sensor temperature Ts (S103). Here, simply, the motor fan 74 may be simply driven.

Standard imaging is performed (S104), processing for subtracting the FPN memory signal is performed (S105), and scratch surrounding pixel interpolation processing (S106) is performed. If the shooting is to be continued (N in S107), the process returns to S101. In the case of shooting end (Y in S107), the flow ends.

In the first embodiment, the Peltier device 71 is heated for about 0.2 seconds in the cooling direction of the image pickup device 70 in the cooling direction of the image pickup device 70 and is left for about 2 seconds for about 1 second in the cooling direction of the image pickup device 70. The image sensor temperature is brought close to the saturation of the internal temperature rise, and the so-called fixed pattern noise change of the dark current unevenness of the image pickup element 70 that varies non-linearly in the screen non-linearly with respect to the image sensor temperature is brought close to the saturation of the internal temperature rise. Thus, the change at the time of shooting after the Peltier element 71 is pulse-driven is reduced, the fixed pattern noise component is detected in about 1 second, and the fixed pattern noise component is subtracted and corrected at the time of shooting.

In other words, in the present invention, the fixed pattern noise component is subtracted in a short time, such as about 2 to 3 seconds after the start-up, instead of shooting after correcting the fixed pattern noise after the change is reduced about 30 minutes after the start-up. Therefore, it is possible to perform high-quality shooting without a fixed pattern noise component.

The characteristics of the first embodiment are summarized as follows. That is, the image pickup apparatus 30 according to the first embodiment includes a temperature sensor 20 (solid-state image pickup device temperature detection unit), an ambient temperature sensor 20a (housing peripheral temperature detection unit), a motor fan 74 (ventilation fan), and a heat radiation fin 73. , A Peltier element 71 between the image sensor 70 (solid-state image sensor) and the radiation fin 73, a Peltier drive circuit 72 that drives the Peltier element 71 positively (cooling), and a light block such as a diaphragm of the lens 71 or an electric filter disk wheel. And a fixed pattern signal obtained by subtracting the OB pixel typical value from the effective pixel imaging signal and stored, and white defect perfect black defect detection interpolation to be subtracted from the video signal obtained by subtracting the OB pixel typical value from the effective pixel imaging signal at the time of imaging Unit 38 (image processing means).

Then, the imaging device 30 starts shielding the light shielding means at the time of activation, stops the motor fan 74, and causes the Peltier element driving circuit 72 to operate for a time (0.001 second) according to the difference between the ambient temperature and the imaging element temperature. To drive the Peltier element 71 in the positive direction, and then to the Peltier element 71 for a time sufficiently longer than the pulse drive (approximately 1 to 3 seconds). (That is, the imaging element 70 and the heat radiation fin 73 are heated so that there is no temperature difference between both surfaces of the Peltier element 71), and the temperature difference between the ambient temperature and the temperature of the imaging element 70 is the same as that of the imaging element 70. When the temperature difference of saturation (thermal resistance and heat capacity saturation) with the radiating fin 73 approaches, that is, within a predetermined temperature range, the motor fan 74 is set to a normal drive corresponding to the temperature of the image sensor, The Peltier driving circuit 72 also performs normal driving corresponding to the image sensor temperature, reads and stores a fixed pattern signal obtained by subtracting the OB pixel typical value from the effective pixel imaging signal, and stores the OB pixel typical value from the effective pixel imaging signal at the time of imaging. Is subtracted from the video signal.

<Example 2>
Hereinafter, Example 2 will be described with reference to the above-described imaging device 30 in FIG. 1 and FIGS. 14, 15, 12, and 13. FIG.

1, the image pickup apparatus 30 shown in FIG. 1 stops the motor fan 74 and drives the Peltier drive circuit 72 in a pulse manner at the time of activation, as in the first embodiment. If the temperature difference between the ambient temperature and the temperature of the image sensor 70 (image sensor temperature) approaches the temperature difference between the thermal resistance and the heat capacity of the image sensor 70 and the heat radiation fin 73, that is, within a predetermined temperature range, the Peltier The driving of the element 71 and the driving of the motor fan 74 are set to normal driving corresponding to the temperature of the imaging element. Then, a fixed pattern signal obtained by subtracting the OB pixel typical value from the effective pixel imaging signal is read and stored only 64 times (about 1 second), and the OB pixel typical value is subtracted from the video signal from the effective pixel imaging signal at the time of imaging. Subtract fixed pattern signal.

Here, FIG. 14 is a block diagram of the Peltier drive circuit 72 of the second embodiment. This Peltier drive circuit 72 is a circuit example that realizes Peltier element driving in both positive (fin heating by imaging element cooling) and negative (fin cooling by imaging element heating) directions.

The Peltier drive circuit 72 has a configuration in which a transistor Q2 and a resistor R4 are added to the circuit configuration of the first embodiment shown in FIG. Transistor Q2 is of the NPN type. The collector terminal of the transistor Q2 is connected to the collector terminal of the transistor Q1, and is commonly connected to one end of the Peltier element 71. The base terminal of the transistor Q2 is connected to the base terminal of the transistor Q1, and is commonly connected to the output of the operational amplifier IC1. The emitter terminal of the transistor Q2 is connected to the negative power supply voltage Vee. Here, the negative power supply voltage Vee is −5V. A resistor R4 is provided between the negative power supply voltage Vee and the inverting input terminal of the operational amplifier IC1. Resistor R4 is 100 kΩ here. The transistor Q1 may be a Pch MOSFET and the transistor Q2 may be a Pch MOSFET.

Here, the relationship between the D / A output Vin of the CPU 39 and the feedback voltage Vr from the resistor R1 is expressed by the following equation using the resistors R2, R3, and R4.
Vr = (Vin / R2 + Vee / R4) × R2 / R3 / (R2 + R3)
For example, assuming a case where the positive power supply voltage Vcc = + 12V, the negative power supply voltage Vee = −5V, the resistance R1 = 0.1Ω, the resistance R2 = 47 kΩ, the resistance R3 = 1500Ω, the resistance R4 = 100K, and Vin = 5V. The feedback voltage Vr≈0.12V. At this time, the voltage across the Peltier element 71 is about 12 V, and the current of the Peltier element 71 is about 1.2 A. In the case of Vin = 0V, the feedback voltage Vr≈−0.05V, the voltage across the Peltier element 71 is about −5V, and the current of the Peltier element 71 is about −0.5A.

FIG. 15 is a diagram showing a driving example of the Peltier element 71 using the Peltier driving circuit 72 of FIG. The pulse drive time, voltage, and current of Peltier device driving in both directions of positive (fin heating by imaging device cooling) and negative (fin cooling by imaging device heating) are schematically shown. Here, (a: upper stage) shows the transition of Peltier element 71 temperature (imaging element temperature Ts and fin temperature Tfin) by the voltage across Peltier element 71 and the current of Peltier element (b). The positive direction (fin heating by imaging element cooling) and the negative direction (fin cooling by imaging element heating) are pulse-driven positively and negatively at a time ratio that is the inverse of the voltage ratio of the positive / negative power supply voltage of the Peltier element driving circuit 72, and about 0 .The imaging element and the fin are heated in a short time of 102 seconds. Here, the H level (12V, 1.2A) corresponding to the positive driving is about 1 msec, and the L level (−5V, −0.5A) corresponding to the negative driving is about 2.4 msec. The combination is operated 30 times, that is, 0.102 seconds. In another example of operation, five combinations of pulses with an H level (12V1.2A) of about 10 msec and an L level (−5V, −0.5A) of about 24 msec for a total of (10 + 24) msec × 5 = 170 milliseconds (0.17 seconds). As described above, the light shielding operation of the second embodiment needs to be as fast as about 0.1 second or less in the former example.

When the light-shielding operation is completed and the temperature rise of the image sensor approaches that equivalent to thermal saturation during Peltier weak cooling during imaging, Peltier weak cooling during imaging is performed and the FPN detection period is accumulated for about 1 second in a light-shielded state. A fixed pattern signal is calculated and stored by subtracting the typical value of the dark current of the OB pixel.

It should be noted that the FPN detection process after a short time FPN change reduction by image sensor heating by pulse driving at the time of activation is the same as the flowchart of FIG. Further, the FPN correction process at the time of imaging is the same as the flowchart of FIG. 13 of the first embodiment. Here, the description is omitted.

In the second embodiment, the Peltier element 71 is driven in the positive direction (the cooling direction of the image pickup element 70 in the heating direction of the heat radiation fin 73) in the positive direction and the negative direction (the heat dissipation fin in the heating direction of the image pickup element 70). The pattern of driving for about 2.4 milliseconds in the cooling direction is repeated, and the imaging element 70 and the radiation fins 73 are heated for about 0.1 second to bring the imaging element temperature close to saturation of the internal temperature rise, and to the temperature of the imaging element 70 On the other hand, the change in the so-called fixed pattern noise of the dark current unevenness of the image pickup element 70 that varies non-linearly and non-uniformly in the screen is brought close to the saturation of the internal temperature rise, and the change at the time of photographing after the Peltier element 71 is pulse-driven is reduced. Then, the fixed pattern noise component is detected in about 1 second, and the fixed pattern noise component is subtracted and corrected at the time of photographing.

That is, the present invention does not take a picture after correcting the fixed pattern noise after the change is reduced in about 30 minutes after starting, but subtracts the fixed pattern noise component as soon as about one second after starting to fix the fixed pattern. It is possible to perform high-quality shooting without noise components.

As described above, the imaging device 30 according to the second embodiment includes the temperature sensor 20 (solid-state imaging device temperature detection unit), the ambient temperature sensor 20a (housing peripheral temperature detection unit), the motor fan 74 (ventilation fan), and the heat dissipation. A fin 73, a Peltier element 71 between the image sensor 70 (solid-state image sensor) and the radiation fin 73, a Peltier drive circuit 72 that drives the Peltier element 71 in both positive and negative directions (cooling direction and heating direction), and an aperture of the lens 71 Alternatively, a shading means such as an electric filter disk wheel and a fixed pattern signal obtained by subtracting the OB pixel typical value from the effective pixel imaging signal are read and stored, and the image signal obtained by subtracting the OB pixel typical value from the effective pixel imaging signal at the time of imaging. A white flaw complete black flaw detection interpolation unit 38 (image processing means) for subtracting the stored fixed pattern signal.

Then, at the time of activation, the light shielding means starts to shield the light, the radiating fin 73 is stopped, the Peltier drive circuit 72 is pulse-driven in both positive and negative directions, and the time ratio of the inverse ratio of the positive / negative power supply voltage of the Peltier drive circuit 72 The Peltier element 71 and the radiating fin 73 are heated so that there is no temperature difference between both sides of the Peltier element 71.

Further, when the temperature difference between the ambient temperature and the image sensor temperature approaches the temperature difference between the image sensor 70 and the heat radiating fin 73 (saturation between thermal resistance and heat capacity), the heat radiating fin 73 corresponds to the image sensor temperature. In this operation, the Peltier drive circuit 72 is also driven normally corresponding to the image sensor temperature, and a fixed pattern signal obtained by subtracting the OB pixel typical value from the effective pixel imaging signal is read out and stored, and the effective pixel imaging signal at the time of imaging is read out. The stored fixed pattern signal is subtracted from the video signal obtained by subtracting the OB pixel typical value.

The present invention has been described based on embodiments (including Example 1 and Example 2). These characteristics are summarized as follows. The imaging device 30 includes a temperature sensor 20 (solid-state imaging device temperature detection means), an ambient temperature sensor 20a (housing outer periphery temperature detection means), a motor fan 74 (ventilation fan), a heat radiation fin 73, and an imaging device 70 ( A Peltier element 71 between the solid-state imaging element) and the radiation fins 73, a Peltier drive circuit 72 for driving the Peltier element 71, a light shielding means such as a diaphragm of the lens 71 or an electric filter disk wheel, and an OB pixel from the effective pixel imaging signal. The fixed pattern signal obtained by subtracting the typical value is read and stored, and the white defect complete black defect detection interpolation unit 38 (subtracting the stored fixed pattern signal from the image signal obtained by subtracting the OB pixel typical value from the effective pixel imaging signal at the time of imaging. Image processing means).

Then, at the time of activation, the light shielding means starts shielding, the motor fan 74 is stopped, and the Peltier driving circuit 72 is set to a time corresponding to the difference between the ambient temperature and the image sensor temperature, that is, the Peltier driving circuit 72 is positive (cooling). If driving only in the direction, a positive (cooling) pulse drive of the Peltier element 71 is executed in about 0.01 to 0.2 seconds, and then a time sufficiently longer than the pulse drive (about 1 to 3 seconds) A state in which no current flows through the element 71 is set.

At this time, if the Peltier drive circuit 72 is driven in both positive (+ 12V) and negative (−5V) directions, pulse driving in the cooling (positive) direction is performed on the Peltier element 71 in the positive (cooling) direction from about 0.1 ms to 30 ms. Then, the pulse driving of the Peltier element 71 in the negative (heating) direction is performed in the negative (heating) direction for approximately 0.2 msec to 70 msec, so that there is no temperature difference between the two surfaces of the Peltier element 71 and heat dissipation. The fins 73 are heated.

Furthermore, when the temperature difference between the ambient temperature and the image sensor temperature approaches the temperature difference of saturation (saturation of thermal resistance and heat capacity) between the image sensor 70 and the radiation fin 73, that is, when the temperature difference falls within a predetermined temperature range, the motor fan 74 is turned on. With normal driving corresponding to the temperature of the image sensor, the Peltier drive circuit 72 also performs normal driving corresponding to the image sensor temperature, and reads and stores a fixed pattern signal obtained by subtracting the OB pixel typical value from the effective pixel imaging signal. Then, it is subtracted from the video signal obtained by subtracting the OB pixel typical value from the effective pixel imaging signal at the time of imaging.

That is, according to this embodiment, the image pickup element 70 is heated by pulsing the Peltier element 71 to bring the temperature close to saturation of the internal temperature rise, and non-linearly fluctuates non-linearly in the screen with respect to the temperature of the image pickup element 70. The change in the so-called fixed pattern noise of the dark current unevenness of the image pickup device to be brought close to the saturation of the internal temperature rise, and the change at the time of shooting after the Peltier device 71 is pulse-driven is reduced to reduce the fixed pattern noise component from about 1 second. It can be detected in about 3 seconds and corrected by subtracting a fixed pattern noise component during shooting. In other words, the imaging device 30 can shoot with high image quality in about 1 to 3 seconds after activation, and can make the 8K camera compatible with ENG (Electronic News News Gathering). In addition, changes in the so-called fixed pattern noise of non-uniform dark current that varies non-linearly in the screen non-linearly with respect to the temperature of CMOS image sensors that are frequently used in high dynamic range (HDR) compatible 2K, 4K, and 8K cameras are allowed. Thus, the cost reduction of HDR compatible 2K, 4K, and 8K cameras can be realized.

The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to combinations of these components, and such modifications are also within the scope of the present invention. For example, although the color camera using the image sensor of the on-chip color filter has been described as the image pickup device 30, it may be a color camera using three R / G / B image sensors, or R / G1 / G2. A color camera using four image sensors of / B may be used. Even in a monochrome camera using an image sensor without an on-chip color filter, the processing of the present invention can be applied if OB correction is performed by video signal processing.

4: Subtractors 5a, 5b: Line memory (1)
6a, 6b: Line memory (2)
7a, 7b: Video signal switching units 8a, 8b, 55: Delay units 9a, 9b: Ambient pixel signal selection units 12a-14a, 12b-14b: Subtracter (1) to subtracter (3)
15: White scratch determination unit 16: White scratch surrounding pixel interpolation unit 17: Black scratch determination unit 18: Black scratch surrounding pixel interpolation unit 19a, 19b: Surrounding pixel median value detection unit,
20: Temperature sensor 20a: Ambient temperature sensors 21a to 28a, 21b to 28b, 21c to 28c: Comparator (1) to Comparator (8)
29a, 29b: Video signal switch 30: Image pickup device 31: Lens 35: Video signal processing unit with white flaw complete black flaw detection interpolation function 36: MATRIX unit 37: Parallel-serial conversion unit (P / S)
38: White scratch complete black scratch detection interpolation unit 39: CPU (control unit)
40: Viewfinders 43 to 45: Adder (1) to Adder (3)
46: 1/4 division unit 47: representative value detection unit 48: representative value average detection unit 50: white defect detection interpolation unit 51: complete black defect detection interpolation unit 52: dark current calculation OB correction unit 53: gamma color contour correction unit 54: Image sensor control unit 70: Image sensor 71: Peltier element 72: Peltier drive circuit (P drive circuit)
73: Radiation fin 74: Motor fan 75: Motor fan drive circuit (F drive circuit)
80: FPN correction unit 81: Black level subtraction unit 82: Memory controller 83: Frame memory 84: One frame addition averaging unit 85: Divider 86, 90: Subtractor 88: Line buffer (1)
89: Line buffer (2)
IC1: Operational amplifier (Op-Amp)
Q1, Q2: Transistors R1 to R4: Resistance

Claims (3)

1. A solid-state image sensor;
   Solid-state image sensor temperature detecting means for detecting the temperature of the solid-state image sensor;
   A casing outer periphery temperature detecting means for detecting an ambient temperature outside the casing;
   A Peltier element attached to the solid-state image sensor;
   A ventilation fan that encourages the flow of air in and out of the housing,
   A radiation fin attached to the Peltier element;
   A Peltier element driving circuit for driving the Peltier element;
   Light shielding means for shielding light to the solid-state imaging device;
   An OB correction process for reading out and storing a fixed pattern signal obtained by subtracting the OB pixel typical value from the effective pixel imaging signal, and subtracting the stored fixed pattern signal from the video signal obtained by subtracting the OB pixel typical value from the effective pixel imaging signal at the time of imaging. Image processing means for performing
   A control unit for controlling the temperature of the image sensor;
   Have
   The controller is
   At the time of start-up, the light shielding means starts shielding, the ventilation fan is stopped, and the Peltier element driving circuit is pulse-driven at a first time corresponding to the difference between the ambient temperature and the temperature of the imaging element. Executing, and subsequently, controlling a state in which no current flows in the Peltier element in a second time longer than the first time,
   When the temperature difference between the ambient temperature and the temperature of the solid-state imaging device is within a predetermined temperature range by being controlled to the state of the second time,
   The control unit controls the ventilation fan to a normal drive corresponding to the temperature of the solid-state image sensor, and controls the Peltier element drive circuit to a normal drive corresponding to the temperature of the solid-state image sensor. The processing unit executes the OB correction process.
2. A solid-state image sensor;
   Solid-state image sensor temperature detecting means for detecting the temperature of the solid-state image sensor;
   A casing outer periphery temperature detecting means for detecting an ambient temperature outside the casing;
   A Peltier element attached to the solid-state image sensor;
   A ventilation fan that encourages the flow of air in and out of the housing,
   A radiation fin attached to the Peltier element;
   A Peltier element driving circuit for driving the Peltier element;
   Light shielding means for shielding light to the solid-state imaging device;
   An OB correction process for reading out and storing a fixed pattern signal obtained by subtracting the OB pixel typical value from the effective pixel imaging signal, and subtracting the stored fixed pattern signal from the video signal obtained by subtracting the OB pixel typical value from the effective pixel imaging signal at the time of imaging. Image processing means for performing
   A control unit for controlling the temperature of the image sensor;
   Have
   The controller is
   At the time of start-up, the light shielding means starts to shield the light, the ventilation fan is stopped, and the Peltier element driving circuit is operated at the first time according to the difference between the ambient temperature and the temperature of the imaging element. Performing pulse driving so that the element cools, and then controlling the Peltier element not to flow current in a second time longer than the first time;
   When the temperature difference between the ambient temperature and the temperature of the solid-state imaging device is within a predetermined temperature range by being controlled to the state of the second time, the control unit moves the ventilation fan to the solid-state imaging device. And controlling the Peltier device driving circuit to normal driving corresponding to the temperature of the solid-state imaging device, the image processing unit executes the OB correction processing,
   The first time ranges from 0.001 seconds to 0.1 seconds,
   The image pickup apparatus, wherein the second time is in the range of 1 second to 3 seconds.
3. Solid-state image sensor temperature detecting means for detecting the temperature of the solid-state image sensor;
   A casing outer periphery temperature detecting means for detecting an ambient temperature outside the casing;
   A Peltier element attached to the solid-state image sensor;
   A ventilation fan that encourages the flow of air in and out of the housing,
   A radiation fin attached to the Peltier element;
   A Peltier element driving circuit for driving the Peltier element;
   Light shielding means for shielding light to the solid-state imaging device;
   An OB correction process for reading out and storing a fixed pattern signal obtained by subtracting the OB pixel typical value from the effective pixel imaging signal, and subtracting the stored fixed pattern signal from the video signal obtained by subtracting the OB pixel typical value from the effective pixel imaging signal at the time of imaging. Image processing means for performing
   A control unit for controlling the temperature of the image sensor;
   Have
   The controller is
   At the time of start-up, the light shielding means starts shielding, the ventilation fan is stopped, the Peltier element driving circuit is pulsed positively and negatively, and the time of the inverse ratio of the positive / negative power supply voltage ratio of the Peltier element driving circuit Heating the solid-state imaging device and the radiation fin so that there is no temperature difference between both sides of the Peltier device by pulse driving in positive and negative ratios,
   When the temperature difference between the ambient temperature and the temperature of the solid-state image sensor approaches the saturation temperature difference between the solid-state image sensor and the heat radiating fin, the ventilation fan is controlled to a normal drive corresponding to the temperature of the solid-state image sensor. In addition, the Peltier device driving circuit is controlled to a normal driving corresponding to the temperature of the solid-state imaging device, and the image processing unit executes the OB correction processing.

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