WO2008153085A1 - 撮像装置、撮像制御方法および撮像制御プログラム - Google Patents
撮像装置、撮像制御方法および撮像制御プログラム Download PDFInfo
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- WO2008153085A1 WO2008153085A1 PCT/JP2008/060723 JP2008060723W WO2008153085A1 WO 2008153085 A1 WO2008153085 A1 WO 2008153085A1 JP 2008060723 W JP2008060723 W JP 2008060723W WO 2008153085 A1 WO2008153085 A1 WO 2008153085A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
- H04N23/70—Circuitry for compensating brightness variation in the scene
- H04N23/741—Circuitry for compensating brightness variation in the scene by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/50—Control of the SSIS exposure
- H04N25/57—Control of the dynamic range
- H04N25/58—Control of the dynamic range involving two or more exposures
- H04N25/587—Control of the dynamic range involving two or more exposures acquired sequentially, e.g. using the combination of odd and even image fields
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/60—Noise processing, e.g. detecting, correcting, reducing or removing noise
- H04N25/63—Noise processing, e.g. detecting, correcting, reducing or removing noise applied to dark current
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/60—Noise processing, e.g. detecting, correcting, reducing or removing noise
- H04N25/68—Noise processing, e.g. detecting, correcting, reducing or removing noise applied to defects
Definitions
- Imaging device imaging control method, and imaging control program
- the present invention relates to an imaging apparatus, an imaging control method, and an imaging control program that are suitable for use in imaging with a long exposure using an imaging element.
- the exposure time When taking an image with a small amount of light per unit time on the film or image sensor in the imaging device, set the exposure time longer, such as several tens of seconds to several minutes, or more to increase the amount of light.
- a dark subject such as a dark place or an astronomical photograph, or narrowing down the aperture to increase the depth of the subject, an example of such an image is considered. It is done.
- Imaging such as CCD (Charge Coupled Device) MOs (Simple Om ementary Met a l-0x i de Semi conductor) Imager etc. that converts the emitted light into an electrical signal by photoelectric conversion and outputs it
- an imaging signal output at a predetermined period such as a frame period is added for each pixel to widen the dynamic range.
- Patent Document 1 describes an image signal obtained from the imaging element for each frame. A configuration in which the dynamic range is expanded by accumulative addition is described in Patent Document 1 (Japanese Patent Application Laid-Open No. 5-231642).
- a white spot (hereinafter, white spot) due to a leak current generated in the pixel portion of the image sensor is caused by a fixed pattern inherent to the image sensor, and the signal level of the white spot is proportional to the exposure time. Get higher. For this reason, the white spot near the black signal level during short-time exposure becomes a signal level that can be visually recognized during long-time exposure, and the number of visible white spots is exponentially increased. This is because that.
- the white spot signal level due to the leakage current results in a signal level that overflows the memory word length due to the addition, the information of the pixel where the white spot has occurred is clipped and lost at the upper limit of the dynamic range. It will be. If the number of white spots in one screen is sufficiently small, the problem can be solved by performing interpolation using the signals of adjacent pixels.
- imaging is performed in a state where the image sensor is shielded from light, and a white point is canceled using an image signal obtained thereby.
- the image was obtained with the image sensor illuminated with light from the subject, then with the exposure time set equal and the image sensor shaded to obtain the light.
- An image signal (hereinafter referred to as a light-shielded image signal) obtained in a light-shielded state from an image signal (hereinafter referred to as a non-light-shielded image signal) is subtracted for each pixel.
- the white point signal level increases in the pixel where the white point occurs according to the exposure time, while pixels other than the white point ideally have the black signal level. It is possible to cancel a point.
- Patent Document 2 Japanese Patent Laid-Open No. 2 0 3 0-2 1 9 2 8 2
- Patent Document 3 Japanese Patent Laid-Open No. 8-5 1 5 7 1
- a non-shielded image signal is thus obtained. Describes a technique in which the fixed pattern noise of the image sensor is removed by subtracting the light-shielded image signal from pixel to pixel.
- the light-shielded image signal is set to 1 ZN, and the subtraction process of the light-shielded image signal from the non-light-shielded image signal is repeated N times so that white point removal is performed more appropriately. .
- dark current accumulation cannot be ignored when performing extremely long exposures. That is, when the exposure is performed for a long time, there is a problem that the output signal of the image sensor may reach the saturation signal level only with the charge for the accumulated dark current.
- an object of the present invention is to provide an imaging apparatus, an imaging control method, and an imaging control program capable of effectively removing white spots while maintaining the dynamic range of the subject signal.
- the present invention includes a plurality of pixels, accumulates charges generated by photoelectric conversion for each pixel, and includes pixel data including charges accumulated in each pixel.
- An image sensor that outputs an image signal;
- First and second storage units for storing imaging signals
- An adder that adds the imaging signal for each pixel data
- the exposure time is divided into a plurality of number of divisions, and the image pickup signal is output from the image sensor for each divided exposure time, and the image pickup signal for each divided exposure time is cumulatively added for each pixel data.
- the image signal is output from the image sensor for each divided exposure time obtained by dividing the exposure time into a plurality of division times, and the image pickup signal for each divided exposure time is cumulatively added for each pixel data.
- each pixel data cumulatively added for a plurality of divisions stored in the first storage unit is obtained. Subtracting part to subtract
- This invention has a plurality of pixels, accumulates electric charges generated by photoelectric conversion for each pixel, and outputs an imaging signal composed of pixel data composed of electric charges accumulated in each pixel.
- an image pickup signal is output as a non-light-shielded image signal from the image sensor for each divided exposure time obtained by dividing the exposure time into a plurality of division times.
- An imaging control method is provided.
- This invention has a plurality of pixels, accumulates electric charges generated by photoelectric conversion for each pixel, and outputs an imaging signal composed of pixel data composed of electric charges accumulated in each pixel.
- a program that causes a computer to execute an imaging method for imaging using
- the imaging method is
- the present invention reads charges from the non-light-shielded imaging device at each timing obtained by dividing the exposure time, and removes the component corresponding to the negative current component from the imaging signal based on the read charges. Then, the digital image signal from which the negative current component has been removed is cumulatively added and stored every time it is read out to the first storage unit, and stored in the first storage unit after the exposure time is completed. Since the data corresponding to the charge accumulated in the time corresponding to the exposure time is subtracted from the digital imaging signal thus output and output corresponding to the exposure time, the digital imaging signal is accumulated in the first storage unit. This has the advantage of suppressing the data clipping during addition and ensuring the dynamic range.
- FIG. 1 is a schematic diagram for conceptually explaining an embodiment of the present invention.
- FIG. 2 is a block diagram showing a configuration of an example of an imaging apparatus according to an embodiment of the present invention.
- FIG. 3 is a schematic diagram showing the configuration of an example of a memory.
- FIG. 4 is a block diagram showing a configuration of an example of an addition / subtraction unit.
- FIG. 5 is a timing chart showing an example of an imaging operation in the imaging apparatus.
- FIG. 6 is a flowchart showing processing according to one embodiment of the present invention.
- FIG. 7 is a flowchart showing a process for determining each of the number of divisions and one sheet exposure time according to the embodiment of the present invention.
- FIG. 8 is a flowchart showing a process for determining the number of divisions and the exposure time for one sheet in the embodiment of the present invention.
- FIG. 9 is a flowchart showing another example of the process according to the embodiment of the present invention.
- FIG. 10 is a schematic diagram for explaining an example of the advantage of the control according to the embodiment of the present invention.
- FIG. 11 is a schematic diagram for explaining an example of advantages of control according to an embodiment of the present invention.
- FIG. 12 is a schematic diagram for explaining an example of the advantage of the control according to the embodiment of the present invention.
- FIG. 1 conceptually shows the exposure processing according to the present invention.
- exposure is divided in the image sensor in the same manner while the image sensor is shielded from light, and the light-shielded image signals obtained by the divided exposure in the shielded state are accumulated (see FIG. 1B).
- the image pickup signal is obtained by subtracting the accumulated light-shielded image signal from the accumulated non-light-shielded image signal (see FIG. 1C).
- the non-light-shielded image signal obtained by the exposure by the digital clamp for each exposure The signal component dark due to the dark current of the imaging element is subtracted from the light-shielded image signal, and the non-light-shielded image signal and the light-shielded image signal in which the dark current signal component dark (hereinafter referred to as the dark current component dark) is subtracted are accumulated. I am doing so. That is, in the non-shielding state in which the image sensor is irradiated with light from the subject, as illustrated in FIG.
- Equation (1) the value I MGi represents the non-light-shielded image signal exposed at the exposure time t. Also, here, ⁇ current component dark is the clamping action The components that are canceled due to temperature change, and components that change due to temperature changes are also included.
- the light-shielded image signals from which the current component dark has been reduced are added for each pixel to obtain an added light-shielded image signal IMGdk add . This can be expressed as Equation (2) below.
- the value I MGdki represents the light-shielded image signal exposed at the exposure time t.
- IMGdk add (IMGdk t -dark)... (2)
- the imaging signal I MGnr add has a wide dynamic range because the white spot due to the fixed pattern is removed from the non-shielded image signal and the influence of the high current is removed.
- Memory is used. That is, for example, in the case of a non-shielded image signal, the non-shielded image signal obtained by the first exposure is written to the memory, and when the non-shielded image signal is obtained by the next exposure, the non-shielded image signal previously written from the memory is obtained. Is added, and the read-out non-shielded image signal and the non-shielded image signal obtained in the next exposure are added, and the addition result is overwritten in the memory.
- the number of bits allocated to one pixel in this memory and the number of bits corresponding to the calculation for one pixel in the adder that adds the non-shielded image signal and the shielded image signal are captured.
- the AZD converter that performs A / D (Analog / Digital) conversion of the output of the element the number of quantization bits used for AZD conversion of the data of one pixel is set larger. As a result, the clip and rounding error at the time of adding the non-light-shielded image signal and the light-shielded image signal can be suppressed, and the image quality can be improved.
- FIG. 2 shows an example of the configuration of the imaging apparatus 1 according to the embodiment of the present invention.
- This imaging device 1 receives light incident through an optical system 10 and a mechanical shutter 11 1 by an imaging device 12, and receives an imaging signal obtained by converting the received light into an electrical signal by photoelectric conversion. The signal is processed and converted into a digital signal by the AZD converter 13 to obtain a digital image signal.
- a shutter other than a mechanical shutter such as a liquid crystal shutter may be used.
- This digital imaging signal is processed by the digital clamp circuit 14, the adder / subtractor 15 and the memory 16 as described later, the image signal processor 17 performs predetermined image processing, and the storage processor 18 records it. Record on media.
- the image processing unit 17 also outputs image data to be displayed on the viewfinder 20 for confirming the captured image.
- the control unit 19 controls the entire imaging apparatus 1.
- the control unit 19 has a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), and also performs timing control such as drive control of the image sensor and frame units and pixel units.
- a synchronization signal generation unit that generates a synchronization signal is provided.
- the CPU controls each part of the imaging device 1 using the RAM as a work memory according to the program stored in the ROM.
- 11 1 part 2 5 is equipped with a release button for starting imaging, and multiple controls for setting the functions of the imaging device 1, such as shot speed, aperture, zoom, and focus.
- a control signal corresponding to the operation is output to the control unit 19.
- the optical system 10 includes a lens system, an aperture mechanism, a focus mechanism, a zoom mechanism, and the like, and the aperture, focus, zoom, and the like are controlled based on control of the control unit 19 and manual operation.
- the mechanical force 11 is configured to be able to block an optical path between the lens system 10 and the image sensor 12 and physically blocks light incident on the image sensor 12. For example, when a release button (not shown) is pressed by the user, the mechanical shutter 11 is opened by the control of the control unit 19, and light is incident on the image sensor 11 through the optical system 10.
- the mechanical shirt 11 is controlled so as to be automatically closed after a predetermined time from the open state, for example, according to a preset shutter speed.
- the image sensor 12 is, for example, a CMO S (Complementary Metal-Oxide An image sensor using a semiconductor (hereinafter abbreviated as CMO S) can be applied. However, the present invention is not limited to this, and a CCD (Charge Coupled Device) can also be applied as the imaging device 12.
- CMO S Complementary Metal-Oxide
- CCD Charge Coupled Device
- the image sensor 12 is a CMOS.
- CMOS can control readout for each pixel. For example, it can control to read a pixel signal for each line. In the CMOS, the extracted charge is read and the extracted charge is reset.
- the image sensor 12 can be both a rolling shirt and a global shutter.
- the rolling shutter starts exposure after resetting for each line, and outputs pixel signals for one line when the exposure period ends. Therefore, the exposure period of each line is shifted by one line.
- the global shirter resets all the lines at once, and exposure starts on all lines simultaneously. Then, signal charges are read from the photodiode to the charge detection unit simultaneously in the imaging region as a whole.
- An imaging signal is output from the imaging device 12 as a signal for each pixel.
- the imaging signal output from the imaging element 12 is subjected to signal processing such as noise suppression processing and gain control processing by a signal processing unit (not shown) and is input to the D converter 13.
- the AZ D converter 13 converts the imaging signal input as an analog signal into a digital signal having a quantization bit number X for each pixel.
- the digital imaging signal output from the AZD converter 13 is supplied to the digital clamp circuit 14.
- the digital clamp circuit 14 digitally counts the supplied digital imaging signal and fixes the black signal level to a predetermined value.
- the digital clamp circuit 14 corresponds to the average value of the signals corresponding to multiple pixels used as optical black for the digital imaging signal whose output from the image sensor 12 is AZD converted. Subtract from the signal you want.
- the digital imaging signal whose black signal level is fixed by the digital clamp circuit 14 is supplied to the adder / subtractor 15.
- the addition / subtraction unit 15 includes an addition processing unit 15 A and a subtraction processing unit 15 B. Using the memory 16, the accumulated addition processing of the supplied digital imaging signal and the data subjected to the cumulative addition processing are performed. Subtract each other.
- the memory 16 has two areas, a memory area 16 A and a memory area 16 B (represented as area # 1 and area # 2 in FIG. 3, respectively). Each of them has a capacity to store at least one frame of digital imaging signal.
- each of the memory areas 16 A and 16 B can be accessed in units of pixels, and the number of quantization bits per pixel of the AZD converter 13 per pixel is further exceeded. The number of bits is assigned. For example, if the A / D converter 13 A / D-converts and outputs 1-pixel data with a 14-bit quantization bit rate, 1 pixel in the memory areas 16 A and 16 B As a min- ute area, at least 15 bits of S damage ij are applied. It is more preferable if the number of bits allocated to one pixel is larger.
- FIG. 4 shows an example of the configuration of the addition / subtraction unit 15.
- the addition processing unit 15 A includes an adder 30 and switches 3 1 and 3 2.
- the subtraction processing unit 15 B includes a subtracter 33.
- the adder 30 has a word length that is at least the number of bits exceeding the number of quantization bits for each pixel of the AZ converter 13. Switches 3 1 and 3 2 select memory areas 16 A and 16 B.
- Addition / subtraction unit 1 5 A digital imaging signal is supplied to one input terminal of the adder 30.
- data is read out from the memory area 16 A and supplied to the other input terminal of the adder 30 through the switch 3 2.
- the adder 30 the digital imaging signal input to one input terminal and the data input to the other input terminal are added.
- the addition result by the adder 30 is overwritten in the memory area 16 A via the switch 31. Note that the addition of data in the adder 30 is performed for each pixel corresponding to each other.
- the number of bits exceeding the number of quantization bits for each pixel of the A / D converter 13 is allocated to one pixel. As a result, it is possible to suppress errors caused by carry-out of data based on carry, data rounding processing, etc. that occur when cumulative addition of digital imaging signals is performed.
- data read out from the memory area 16 A for each pixel is supplied to one input terminal of the subtractor 33.
- the data read out from the memory area 16 ⁇ for each pixel is supplied to the other input terminal of the subtractor 33.
- the subtracter 33 subtracts the data input to the other input terminal from the data input to one input terminal and outputs the result.
- the subtraction process in the subtracter 33 is performed for each pixel corresponding to each other, for example.
- the digital image signal output from the adder / subtractor 15 is supplied to the image signal processor 17.
- the image signal processing unit 17 converts the supplied digital imaging signal into image data of a predetermined format, and performs image processing such as image quality correction on the image data.
- the image data output from the image signal processing unit 17 is supplied to the storage processing unit 18.
- the save processing unit 1 8 converts the supplied image data into, for example, JPEG (Joint The image is compressed and encoded by a predetermined compression code method that is similar to the Photographic Experts Group) method and recorded on a recording medium such as the memory 21.
- JPEG Joint Photographic Experts Group
- the release button is pressed and the ON state is entered at time t i (see Fig. 5A).
- the release button is automatically set to ⁇ FF state when a time corresponding to the shutter speed has elapsed since being set to the ON state.
- the mechanical shutter 11 is opened (see Fig. 5B), and light from the subject is irradiated to the image sensor 12 through the optical system 10 and is not shielded by the image sensor 12.
- the control unit 19 generates a vertical synchronizing signal V D (see FIG. 5C) and supplies it to the image sensor 12.
- the image sensor 12 outputs the charges stored in all the pixels simultaneously by the global shirter function (G SH), and resets the charges in all the pixels.
- the memory clearing timing may be before the accumulation of data to the memory 16 is started, and is not limited to the time of the first pixel reading, for example, when the release button is pressed. You may do so.
- the image sensor 12 sequentially reads out the charges accumulated in each pixel by the rolling shutter function (RSH) in units of lines (see Fig. 5D), Is output. Charge accumulation starts immediately after the pixel from which the charge has been read out.
- RSH rolling shutter function
- the imaging signal sequentially output in line units from the imaging device 12 is A / D converted by the AZD converter 13 and converted into a digital imaging signal in which the number of quantization bits per pixel is X bits.
- the black signal level is fixed by being clamped by the digital clamp circuit 14. By the clamping process in the digital clamp circuit 14, the process of subtracting the saddle current component d ar k of the image sensor from the image signal described with reference to FIG. 1 is realized.
- the digital imaging signal clamped by the digital clamp circuit 14 is supplied to the adder / subtractor 15 and is cumulatively written in the memory 16 (see Fig. 5E).
- the mechanical-shirt motor 1 1 are open, since the image pickup element 1 2 is exposed by the light from an object, the digital imaging signal corresponds to the non-shaded image signal described above.
- terminals 3 1 A and 3 2 A are selected by switches 3 1 and 3 2, respectively.
- the digital imaging signal is supplied to one input terminal of the adder 30 and the data read from the memory area 16 A of the memory 16 is added to the adder 30.
- 30 is supplied to the other input terminal.
- the stored contents of the memory 16 are cleared at the previous time, and the value 0 is supplied to the other input terminal of the adder 30 for each pixel.
- data supplied to one and the other input terminals is added for each pixel, and is overwritten in the memory area 16 A via the switch 31.
- the digital image signal output from the image sensor 12 2 is clamped, and the clamped digital image signal is written to the memory area 16 A.
- the digital imaging signal is written to the memory area 16 A by adding the data read from the memory area 16 A and the digital imaging signal that has been clamped and supplied to the addition / subtraction unit 15. This is added for each pixel by the device 30 and overwritten in the memory area 16 A.
- Time t 4 is, for example, when the mechanical shirt motor 1 1 is shifted from the open state to the closed state.
- FIG. 1A and Equation (1) are used for the divided exposure during the period when the mechanical shirt 11 is in the open state and the light from the subject is irradiated on the image sensor 12.
- An addition process is performed on the result of subtracting the dark current dark from the non-shielded image signal.
- the mechanical state remains closed, that is, the image sensor 12 is exposed to light and the exposure process of the image sensor 12 is performed.
- the exposure time is approximately the same as the exposure time (1 minute in this example).
- the image sensor 1 2 is exposed to light.
- an addition process is performed on the result of subtracting the dark current component dark from the light-shielded image signal, as described using FIG. 1B and Equation (2).
- the exposure process when the mechanical shirt 11 is closed is performed in substantially the same manner as the exposure process when the image sensor 12 is irradiated with light from the subject as described above.
- the imaging element 1 2 is a vertical synchronizing signal in the control unit 1 9 at time t 5 after a predetermined time instant t the charge readout is performed accumulated in the pixel in the divided exposure of the last exposed with a non-light-shielded state VD Is generated (see FIG. 5C) and supplied to the image sensor 12.
- the charges accumulated in all the pixels are simultaneously output by the global shutter function according to the vertical synchronization signal VD, and the accumulation of the charges is started in each pixel immediately after (see FIG. 5D).
- a vertical synchronizing signal VD generated by the control unit 1 9, Supplied to image sensor 1 2.
- the image sensor 12 sequentially reads out the charges accumulated in each pixel by the rolling shutter function in units of lines and outputs them as an image signal (FIG. 5D).
- the pixel from which the charge has been read starts to accumulate electric charges immediately after the read.
- the imaging signal output from the imaging device 12 is converted into a digital imaging signal in which the quantization bit number of one pixel is X bits by the AZD converter 13 and clamped by the digital clamp circuit 14 and the black signal level is increased. Fixed Is done.
- the digital imaging signal whose black signal level is fixed is supplied to the adder / subtractor 15, and the value for each pixel is cumulatively written in the memory 16 in the same manner as described above.
- the digital image signal that is exposed in a state where the image sensor 12 is shielded is written to the memory area 16 B of the memory 16.
- terminals 3 1 B and 3 2 B are selected by switches 3 1 and 3 2, respectively.
- the digital imaging signal is supplied to one input terminal of the adder 30, and the data read from the memory area 16 B of the memory 16 is supplied to the other input terminal of the adder 30.
- the stored contents of the memory 16 are cleared at the previous time, and the value 0 is supplied to the other input terminal of the adder 30 for each pixel.
- the adder 30 data supplied to one input terminal and the other input terminal is added for each pixel, and is overwritten in the memory area 16 B via the switch 31.
- corresponding pixel data is read from memory area 16 A and memory area 16 B, and one of subtracters 33 and It is supplied to the other input end.
- the subtracter 33 subtracts the data supplied to the other input terminal from the data supplied to one input terminal and outputs the result. This process is performed for all the pixel data for one frame written in the memory area 16 A and the memory area 16 B, respectively.
- white spots due to the fixed pattern of the image sensor 12 can be effectively removed, and captured image data in which deterioration of the dynamic range due to accumulation of ⁇ current components is suppressed can be obtained.
- FIG. 6 is a flowchart showing an example of exposure processing according to the embodiment of the present invention. Each determination in this flowchart is made based on a predetermined program in the control unit 19, for example.
- the shutter speed is set, and the number of divisions for performing the divided exposure in the exposure time determined by the shutter speed is determined.
- step S21 in Fig. 7A 3 minutes, 5 minutes, etc. are set as the exposure time for one sheet at the time of factory shipment.
- the user sets the shutter speed (mechanical shutter speed) to 60 minutes, for example, during imaging (step S 2 2).
- step S 3 the number of divisions is set to 20 at the time of factory shipment, for example.
- step S 3 2 the user sets the shutter speed to 60 minutes, for example, during imaging.
- step S 10 the timing for reading out electric charges from the image sensor 12 is awaited.
- the control unit 19 If it is determined that the read timing is reached, for example, the control unit 19 generates a vertical synchronization signal VD and supplies it to the image sensor 12.
- the next step S 11 it is determined whether or not the electric charge read out from the image sensor 12 by this timing is accumulated by the first exposure after the release button is pressed. For example, time t 2 in FIG. 5, it is determined that the release button is to be due to the first exposure from being pressed.
- step S 11 If it is determined in step S 11 that it is not due to the first exposure, the process proceeds to step S 13. On the other hand, if it is determined that it is due to the first exposure, the process proceeds to step S 12, the stored contents of the memory 16 are cleared, and the process proceeds to step S 13.
- step S 13 it is determined whether the exposure is performed in a non-shielded state where the image sensor 12 is irradiated with light from the subject or the exposure is performed in a state where the image sensor 12 is shielded. If it is determined that the exposure is performed in a non-shielded state in which the image sensor 12 is irradiated with light from the subject, the process proceeds to step S 14. On the other hand, if it is determined that the exposure is performed with the image sensor 12 in a light-shielded state, the process proceeds to step S 15.
- step S 14 a non-light-shielded image signal, which is a digital image signal obtained by exposure performed on the image sensor 12 2 in a non-light-shielded state, is supplied to the adder / subtractor 15, and as described above, Memory area 1 6 Cumulatively written to A.
- step S 15 a light-shielded image signal, which is a digital image signal obtained by exposure performed with the image sensor being in a light-shielded state, is supplied to the adder / subtractor 15, as described above. Are accumulated in memory area 16 B of memory 16.
- step S 16 the predetermined number of exposures according to the determined number of divisions has been completed. Judgment is made. If it is determined that the predetermined number of exposures have not yet been completed, the process returns to step S 10 and the next exposure timing is awaited.
- step S 16 determines whether the predetermined number of exposures have been completed. If it is determined in step S 16 that the predetermined number of exposures have been completed, the process proceeds to step S 17.
- step S 17 the adder / subtractor 15 cumulatively writes to the memory area 16 B from the non-light-shielded image signal that has been cumulatively written to the memory area 16 A based on the equation (3) described above. The process of subtracting the shaded image signal is performed for each pixel. This subtraction process for each pixel is performed on all the pixel data for one frame written in the memory area 16 A and the memory area 16 B, respectively.
- steps S 10, S 11, S 12, and S 14 in FIG. 6 are represented as steps S 1 10, S i 11, S 1 1 2, and S 1 1 4.
- step S 1 0 the force value C NT 1 indicating the number of divided exposures is initialized to 0. Thereafter, similarly to the processing shown in the flowchart of FIG. 6, exposure in a non-light-shielded state is performed. Step In SI 0 2, the count value CNT 1 is incremented every time the divided exposure is performed, and the count value CNT 1 is stored. If it is determined in step S 103 that the release has been released, a non-light-shielded image signal is added in memory area # 1 in step S 104.
- step S 2 0 the force count value CNT 2 indicating the number of divided exposures is initialized to 0.
- the subject signal component is assumed to be a signal component obtained by removing the noise component due to the fixed pattern of the image sensor 12 or the current component dark from the captured image signal based on the output from the image sensor 12. To do.
- the subject signal component increases with the exposure time, and the dark current component also accumulates and increases.
- the subject signal component and the heel current component are separated by the exposure time et.
- the added non-shielded image signal component reaches the X bit, which is the maximum output signal level in the AZD converter, and after the exposure time et, the non-shielded image signal component level is saturated and clipped. . Therefore, the dynamic range of the subject signal is significantly reduced after the exposure time et.
- divided exposure is performed by dividing the exposure time in long exposure, and the dark current component dark is subtracted from the subject signal component for each divided exposure. Therefore, the dark current component dark is subtracted before the non-light-shielded image signal component reaches the maximum output signal level of the AZD converter, and only the subject signal component can be cumulatively added as the non-light-shielded image signal.
- the dynamic range can be secured.
- the non-shielded image signal is a signal in which a subject signal component based on light from a subject and a noise component based on a fixed pattern of the image sensor 12 are combined.
- the subject signal component increases with the exposure time and the noise component based on the fixed pattern also increases.
- the dynamic range of the subject signal component is compressed by the accumulated noise component.
- the mechanical shutter 11 is opened and exposure is performed to obtain a non-shielded image signal. Then, the mechanical shutter 11 is closed and substantially the same as the exposure time of the non-shielded image signal. Exposure for The shaded image signal is obtained. In the shaded image signal, only noise based on the fixed pattern of the imaging element 12 is accumulated. Therefore, by subtracting the light-shielded image signal component from the non-light-shielded image signal component after exposure of the light-shielded image signal, only the subject signal component is added to the non-light-shielded image signal as illustrated in Fig. 11 B. The dynamic range of the subject signal component can be secured.
- the number of bits exceeding the number of quantum bits per pixel in the AZD converter 13 is assigned to one pixel.
- An example of the benefits of allocating to is described.
- the straight line indicating the non-shielded image signal component indicates the value in the memory area 16 A
- the straight line indicating the defective component is the value in the memory area 16 B. It shall be shown.
- the difference between the non-shielded image signal component in the memory area 16 A and the defective component in the memory area 16 B becomes the subject signal component based on the light from the subject.
- the non-shielded image signal component cumulatively increases with the exposure time, and in the memory area 16 A, the cumulative result of the non-shielded image signal component is, for example, the exposure time. It is conceivable that the et component is saturated at the data length of X bits in et, and the cumulative component of X bits or more is clipped after the exposure time et.
- the dynamic range of the subject signal component which is the result of subtracting the cumulative result of the defect component from the cumulative result of the non-light-shielded image signal component, is greatly reduced. Therefore, in the embodiment of the present invention, in the memory 16, 1 The number of bits exceeding the number of quantization bits per pixel of the AZD converter 13 (assuming Y bits) is assigned to the pixels. As a result, as illustrated in Fig. 12B, even if the exposure is performed for a long time, the accumulation result of the non-shielded image signal component is suppressed from being saturated in the memory area 16 A, and the subject signal component The dynamic range is secured (see Fig. 12 C).
Abstract
Description
Claims
Priority Applications (4)
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EP08765494A EP2157784A4 (en) | 2007-06-14 | 2008-06-05 | PICTURE RECORDING, IMAGE RECORDING AND PICTURE RECORDING PROGRAM |
CN2008800200299A CN101682699B (zh) | 2007-06-14 | 2008-06-05 | 成像装置、成像控制方法以及成像控制程序 |
JP2009519294A JP5229224B2 (ja) | 2007-06-14 | 2008-06-05 | 撮像装置、撮像制御方法および撮像制御プログラム |
US12/664,412 US8237812B2 (en) | 2007-06-14 | 2008-06-05 | Imaging apparatus, imaging control method, and imaging control program |
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JP2007-157183 | 2007-06-14 | ||
JP2007157183 | 2007-06-14 |
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US (1) | US8237812B2 (ja) |
EP (1) | EP2157784A4 (ja) |
JP (1) | JP5229224B2 (ja) |
KR (1) | KR20100031599A (ja) |
CN (1) | CN101682699B (ja) |
MY (1) | MY151485A (ja) |
WO (1) | WO2008153085A1 (ja) |
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JP2011234168A (ja) * | 2010-04-28 | 2011-11-17 | Canon Inc | 撮像装置及び制御方法 |
JP2012163522A (ja) * | 2011-02-09 | 2012-08-30 | Mitsui Optronics:Kk | 温度情報計測方法 |
WO2013054403A1 (ja) * | 2011-10-12 | 2013-04-18 | キヤノン株式会社 | 撮像装置及び撮像装置の制御方法 |
WO2013054402A1 (ja) * | 2011-10-12 | 2013-04-18 | キヤノン株式会社 | 撮像装置及び撮像装置の制御方法 |
JP2014086855A (ja) * | 2012-10-23 | 2014-05-12 | Olympus Imaging Corp | 撮像装置 |
JP2016226059A (ja) * | 2011-07-11 | 2016-12-28 | キヤノン株式会社 | 画像処理装置、撮像装置及び画像処理方法 |
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Also Published As
Publication number | Publication date |
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JP5229224B2 (ja) | 2013-07-03 |
US20100182451A1 (en) | 2010-07-22 |
EP2157784A1 (en) | 2010-02-24 |
KR20100031599A (ko) | 2010-03-23 |
CN101682699B (zh) | 2012-10-10 |
MY151485A (en) | 2014-05-30 |
CN101682699A (zh) | 2010-03-24 |
EP2157784A4 (en) | 2011-03-09 |
US8237812B2 (en) | 2012-08-07 |
JPWO2008153085A1 (ja) | 2010-08-26 |
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