JP2008113070A - Imaging device and imaging method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To pick up an image of high quality by an imaging device through fast imaging operation. <P>SOLUTION: Image data generated through imaging and digital conversion by an imaging element are compressed by a RAW compressing unit 41 by an irreversible compression method and temporarily held as compressed image data in a memory. A RAW expanding unit 42 expands the compressed image data read out of the memory, and a signal processing function including a gain adjusting part 44 in a digital image processing circuit 14 processes the image data expanded by the RAW expanding unit 42 as specified. A compression/expansion control unit 74 automatically switches the compressing operation of the RAW compressing unit 41 and the expanding operation of the RAW expanding unit 42 into off states when a gain application quantity of the gain adjusting part 44 becomes equal to or more than a predetermined gain threshold. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image pickup apparatus and an image pickup method for picking up an image using a solid-state image pickup device, and is suitable for a case where digitally converted image data is temporarily stored in a memory and then the image data is read from the memory and processed. The present invention relates to an imaging apparatus and an imaging method.

  In recent years, imaging apparatuses capable of capturing an image using a solid-state imaging device and storing the captured image as digital data, such as a digital still camera and a digital video camera, have become widespread. In such an image pickup apparatus, the number of pixels of the image pickup element is increased and the function and performance of the apparatus are improved. In particular, as the number of pixels of the image sensor increases, the processing load of the image pickup signal increases. However, even such an image pickup apparatus is required to be able to process at high speed so that there is no stress in operation.

  Further, in a general digital imaging apparatus, RAW (raw) image data obtained from an imaging element is temporarily stored in an image memory such as an SDRAM (Synchronous Dynamic Random Access Memory), and then read from the image memory. Many are configured to perform signal processing and the like. For example, in the case of an imaging device that captures one frame in a plurality of fields, such as when using an interlace readout type imaging device, the data of each field is stored in the image memory, and then the frame data is generated. It is essential. Further, in order to suppress the size of the line memory of the camera signal processing unit, the entire screen is partially (for example, vertically) using only a delay line that is a fraction of the length of 1H (horizontal synchronization period). Even in the case of a processing system that performs processing (in the form of several strips in the direction), it is necessary to store the data of the entire screen in the memory at least before the processing.

  However, in the imaging apparatus having such a configuration, as the number of pixels of the imaging element increases and the capacity of the RAW image data increases, the load of data transfer increases and the time required for writing / reading of the image memory also increases. Therefore, if the time required for the recording process is to be shortened, it is necessary to increase the bus band by increasing the transmission frequency, and there is a problem that the apparatus cost increases. There is also a problem that the larger the number of pixels, the larger the capacity of the memory for storing the RAW image data. Therefore, it is considered to increase the processing speed by compressing and transmitting RAW image data during transmission on the internal bus.

As a technique related to the above, an imaging apparatus having a function of recording a captured image on a recording medium as RAW image data instead of compressed data by a JPEG (Joint Photographic Experts Group) method or the like is realized. For example, there is a function of compressing and recording RAW image data by a reversible compression method using a Huffman table, and optimizing the Huffman table for each color channel (for example, see Patent Document 1). ). In addition, when a RAW compression mode for compressing and recording RAW image data is set, an interpolation processing unit for RAW image data used in the normal compression mode is bypassed (for example, Patent Document 2). reference). Patent Document 1 compresses RAW image data using a variable-length encoding method, and both Patent Documents 1 and 2 compress RAW image data in order to reduce the bandwidth of the internal bus. is not.
Japanese Patent Laid-Open No. 2004-40300 (paragraph numbers [0019] to [0028], FIG. 2) JP 2003-125209 A (paragraph numbers [0027] to [0037], FIG. 1)

  By the way, there is a strong demand for a recent digital imaging device to increase imaging sensitivity. For this reason, there are many opportunities to amplify the image data obtained by imaging by applying gain. Yes. However, generally, when a strong gain is applied to image data, a lot of noise appears and image quality deteriorates.

  In particular, as described above, when a method of compressing and transmitting RAW image data on the internal bus of the imaging apparatus, and further employing a lossy compression and variable length encoding method as the compression method, There has been a problem that image quality deterioration due to compression, which has not been a problem, may become noticeable by increasing the gain application amount.

  Further, in the image data compression, there is a problem that the influence on the image quality deterioration becomes strong even when the image data includes many high-frequency components or when image data having a wide dynamic range is input.

  The present invention has been made in view of the above points, and an object thereof is to provide an imaging apparatus and an imaging method capable of capturing a high-quality image by a high-speed imaging operation.

  In the present invention, in order to solve the above-described problem, in an imaging apparatus that captures an image using a solid-state imaging device, the image data captured by the solid-state imaging device and converted into a digital image is compressed by an irreversible compression method. A compression unit that outputs data; a memory that temporarily holds the compressed image data output from the compression unit; a decompression unit that decompresses the compressed image data read from the memory; and the decompression unit. A signal processing unit that performs predetermined signal processing including gain application processing on the decompressed image data; an ON state that causes the compression unit and the decompression unit to perform a compression operation and a decompression operation; and the compression operation and The expansion operation is stopped and the off state in which the input image data is output as it is is switched, and the gain application amount in the signal processing unit is predetermined. If it is more than the gain threshold, the imaging device is provided characterized by having a said switch the compression operation and the decompression operation to the off-state compression / decompression control unit.

  In such an imaging apparatus, image data captured by a solid-state imaging device and digitally converted is compressed by a compression unit using an irreversible compression method, and temporarily stored in a memory as compressed image data. The expansion unit expands the compressed image data read from the memory, and the signal processing unit performs predetermined signal processing including gain application processing on the image data expanded by the expansion unit. The compression / decompression control unit has a function of switching between an on state in which the compression unit and the decompression unit respectively perform a compression operation and an expansion operation, and an off state in which the compression operation and the decompression operation are stopped and input image data is output as it is. When the gain application amount in the signal processing unit is greater than or equal to a predetermined gain threshold value, the compression operation of the compression unit and the expansion operation of the expansion unit are automatically switched to an off state.

  According to the imaging apparatus of the present invention, the image data captured and digitally converted by the solid-state imaging device is temporarily stored in the memory in a state compressed by the compression unit, and the compressed image data is read from the memory. Since the data is decompressed by the decompression unit and processed by the signal processing unit, the access time to the memory for writing and reading the image data is shortened, and the processing can be speeded up. At the same time, under the control of the compression / expansion control unit, when the gain application amount in the signal processing unit is equal to or greater than a predetermined gain threshold value, the compression operation of the compression unit and the expansion operation of the expansion unit are switched to the off state. Therefore, it is possible to suppress image quality degradation caused by the compression process.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing a main configuration of an imaging apparatus according to an embodiment of the present invention.
The imaging apparatus shown in FIG. 1 is realized as a digital still camera or a digital video camera. The imaging apparatus includes an optical block 11, a driver 11a, an imaging device 12, a timing generator (TG) 12a, an analog / digital (A / D) conversion circuit 13, a digital image processing circuit 14, an image memory 15, a display 16, and a microcomputer. 17, an input unit 18, a memory card I / F (interface) 19, a memory card 19 a, a flash memory 20, and a built-in memory 21.

  The optical block 11 includes a lens for condensing light from the subject on the image sensor 12, a drive mechanism for moving the lens to perform focusing and zooming, a shutter mechanism, an iris mechanism, and the like. The driver 11 a controls driving of each mechanism in the optical block 11 based on a control signal from the microcomputer 17.

  The image pickup device 12 is a solid-state image pickup device such as a CCD (Charge Coupled Device) type or a CMOS (Complementary Metal Oxide Semiconductor) type, and is driven based on a timing signal output from the TG 12a to receive incident light from a subject. Convert to electrical signal. The TG 12 a outputs a timing signal under the control of the microcomputer 17.

  The A / D conversion circuit 13 is a circuit that executes analog front-end processing including A / D conversion for an image signal. The A / D conversion circuit 13 performs a sample hold on the image signal output from the image sensor 12 so as to maintain a good S / N (Signal / Noise) ratio by CDS (Correlated Double Sampling) processing. A / D conversion is performed on the signal to output digital image data.

  The digital image processing circuit 14 performs a detection process for AF (Auto Focus), AE (Auto Exposure), various image quality correction processes on the image data from the A / D conversion circuit 13, and a micro based on the detection information. Various image quality correction processes according to the signal output from the computer 17 are performed. In addition, a function of generating data for display on the display 16 and a function of compressing / decompressing image data using a JPEG method or the like are also provided.

  The image memory 15 is made of, for example, SDRAM, and is connected to the digital image processing circuit 14 via a memory bus 15a. The image memory 15 temporarily stores image data processed by the digital image processing circuit 14. As will be described later, a part of the image data transferred between the image memory 15 and the digital image processing circuit 14 via the memory bus 15a is a compression of the RAW image data provided in the digital image processing circuit 14. • Compressed by the decompression function.

  The display 16 is composed of an LCD (Liquid Crystal Display), for example, and displays an image based on display image data output from the digital image processing circuit 14. The display 16 displays an image that is currently being picked up by the image pickup device 12, a reproduced image based on the image data recorded on the memory card 19a, and the like.

  The microcomputer 17 comprehensively controls the entire imaging apparatus. A flash memory 20 and a built-in memory 21 are connected to the microcomputer 17. The microcomputer 17 reads and executes various programs stored in the flash memory 20, for example, and stores the programs in the flash memory 20 as necessary. Refer to various data. The built-in memory 21 that is a volatile memory is used as a work area when the microcomputer 17 executes a program.

  The input unit 18 outputs a control signal corresponding to an operation input by the user to various input switches to the microcomputer 17. As this input switch, for example, a shutter release button, a cross key for selecting various menus, setting an operation mode, and the like are provided.

  The memory card I / F 19 includes a card slot (not shown) in which the memory card 19a is inserted, and performs data writing to the memory card 19a inserted and data reading from the memory card 19a. The memory card 19a is composed of a nonvolatile memory such as a flash memory, and mainly stores image files. In addition to the memory card 19a, for example, a portable recording medium such as a magnetic tape or an optical disk, or a built-in recording medium such as an HDD (Hard Disk Drive) may be used as a recording medium for storing an image file. Good.

  In this image pickup apparatus, signals received and photoelectrically converted by the image pickup device 12 are sequentially supplied to the A / D conversion circuit 13 and converted into digital image data. The digital image processing circuit 14 performs image quality correction processing on the image data supplied from the A / D conversion circuit 13, converts the processed image data into an image signal for display, and outputs it to the display 16. As a result, the display 16 displays the currently captured image on the display 16, and the photographer can visually recognize this image and check the angle of view.

  In this state, when the microcomputer 17 is instructed to record an image by pressing the shutter release button of the input unit 18, the digital image processing circuit 14 displays the image data after the image quality correction processing. A compression encoding process is performed to generate an image file. Note that a RAW image data file that has not been subjected to image quality correction processing or compression encoding may be generated. The microcomputer 17 supplies the image file generated by the digital image processing circuit 14 to the memory card I / F 19 and stores it in the memory card 19a.

  The image file to be recorded in the memory card 19a may be a moving image file as well as a still image file. The digital image processing circuit 14 compresses and encodes one frame of image data when recording a still image file, and outputs the compressed and encoded image data continuously when recording a moving image file.

FIG. 2 is a block diagram showing the internal configuration of the digital image processing circuit.
The digital image processing circuit 14 includes a RAW compression unit 41, a RAW expansion unit 42, a detection unit 43, a gain adjustment unit 44, a white balance (WB) adjustment / YC conversion unit 45, and a resolution conversion / compression expansion unit 46.

  The RAW compression unit 41 compresses the RAW image data output from the A / D conversion circuit 13 and supplies it to the image memory 15 via the memory bus 15a. In practice, the image data supplied from the A / D conversion circuit 13 is subjected to preprocessing such as signal correction processing for defective pixels in the image sensor 12 and shading processing for correcting a loss of peripheral light of the lens. Then, the processed RAW image data may be supplied to the RAW compression unit 41.

The RAW decompression unit 42 decompresses the compressed RAW image data read from the image memory 15 via the memory bus 15 a and outputs the decompressed RAW image data to the detection unit 43 and the gain adjustment unit 44.
Note that the RAW compression unit 41 and the RAW expansion unit 42 can switch whether to perform compression / expansion processing on the input signal in accordance with a control signal instructing on / off from the microcomputer 17. It is possible.

  The detection unit 43 performs signal detection processing for AF, AE, AWB (Auto White Balance), etc. based on the image data supplied from the RAW expansion unit 42, and outputs the detection result to the microcomputer 17. Based on the detection result, the microcomputer 17 calculates a focus lens control signal for AF, an exposure control signal for AE, a gain control signal for AWB, and the like.

The gain adjustment unit 44 applies gain to each frame of the image data supplied from the RAW expansion unit 42 based on a gain control signal from the microcomputer 17.
The WB adjustment / YC conversion unit 45 applies a WB gain according to a control signal from the microcomputer 17 to the image data whose gain has been adjusted by the gain adjustment unit 44. Further, the image data after WB adjustment is converted into a Y (luminance) signal and a C (color difference) signal.

  The resolution conversion / compression / decompression unit 46 converts the resolution of the image data YC converted by the WB adjustment / YC conversion unit 45 into a resolution corresponding to a control signal from the microcomputer 17. For example, the image data for display is generated by converting to a resolution suitable for the display 16. In addition, the image data is converted to a resolution designated for recording on the memory card 19a, and the image data after the conversion is subjected to compression encoding processing according to a predetermined encoding method such as JPEG. The image data generated by the compression encoding process is supplied to the memory card I / F 19 via the microcomputer 17. Furthermore, the image data supplied from the memory card I / F 19 via the microcomputer 17 can be expanded and decoded to be converted into a display resolution and output to the display 16.

  The display processing unit 47 is configured as an NTSC (National Television Standards Committee) encoder, for example, and displays an image on the display 16 based on the image data whose resolution is converted for the display 16 by the resolution conversion / compression / decompression unit 46. An image signal for generating the image is generated and output to the display 16. Further, the composite image data supplied from the microcomputer 17 can be combined with the image data from the resolution conversion / compression / decompression unit 46. For example, a luminance histogram of the captured image can be synthesized and displayed.

  In the digital image processing circuit 14, the image data gain-adjusted by the gain adjustment unit 44 is processed by the WB adjustment / YC conversion unit 45, the resolution conversion / compression / decompression unit 46, and the display processing unit 47. The image data being processed is appropriately written into the image memory 15 via the memory bus 15a, and is read out therefrom.

  As described above, when the digital image processing circuit 14 processes the image data output from the A / D conversion circuit 13, the processing target data is appropriately written in the image memory 15, and necessary data is read therefrom and processed. Is done. Here, by providing the RAW compression unit 41 at the input position of the RAW image data in the digital image processing circuit 14, the amount of RAW image data transmitted to the image memory 15 through the memory bus 15a, and the data as an image Both the amount of data when reading from the memory 15 and transmitting to the digital image processing circuit 14 through the memory bus 15a can be reduced.

  Thereby, the transmission load of the memory bus 15a during the imaging operation is reduced, and the time required for the writing / reading processing with respect to the image memory 15 is shortened. In particular, by simplifying the compression / expansion processing in the RAW compression unit 41 and the RAW expansion unit 42 as much as possible, the effect of shortening the processing time can be enhanced. Further, the transmission frequency on the memory bus 15a can be reduced to suppress power consumption.

  In addition, the capacity of the image memory 15 can be reduced. Further, if the capacity is the same, the area of the image memory 15 is used for other processing, RAW image data for a plurality of frames is stored, the number of continuous shots is increased, or the continuous shooting speed is improved. It can also contribute to higher image quality and higher functionality. Therefore, it is possible to realize a high-performance, small-sized and low-cost imaging device in which the time required for imaging and data recording is reduced.

  In the present embodiment, as will be described later, the RAW compression unit 41 and the RAW expansion unit 42 can perform fixed-length encoding, can maintain good image quality, and can be processed relatively easily. Employs a lossy compression / decompression technique that can be realized with By encoding at a fixed length, it is possible to stably reduce the transmission load on the memory bus 15a and the capacity of the image data storage area on the image memory 15, and read / write control processing in the image memory 15 Can be simplified. In addition, since the compression / decompression process is simplified and speeded up, the imaging operation is reliably speeded up.

  By the way, when irreversible compression is performed on image data, it is inevitable that the image quality is basically deteriorated in the image data expanded thereafter. In particular, even when only image quality deterioration that is normally difficult to visually recognize occurs, when gain is applied to the decompressed image data, image quality deterioration occurs as the gain application amount increases. May stand out.

  In the imaging apparatus of the present embodiment, when the imaging sensitivity is increased, the amount of gain applied to the input image data by the gain adjusting unit 44 in the digital image processing circuit 14 is increased under the control of the microcomputer 17. In this case, there is a possibility that image quality deterioration due to compression cannot be ignored. Therefore, in the present embodiment, when the amount of gain applied is high, the RAW compression unit 41 and the RAW expansion unit 42 do not perform compression / expansion processing, and control to output the input image as it is. To prevent deterioration.

  In addition, when image data is compressed, image quality deterioration generally tends to occur even when the input image contains many high-frequency components or when the input image has a wide dynamic range. In particular, as in the compression method employed in the present embodiment, when performing fixed-length encoding in which the compression rate can be changed in units of a plurality of pixels, the higher the high-frequency component and the wider the dynamic range, The compression rate is increased, and image quality is likely to deteriorate.

  Therefore, in the imaging apparatus of the present embodiment, the operation of compression / expansion processing in the RAW compression unit 41 and the RAW expansion unit 42 is further controlled in consideration of the high-frequency component and dynamic range of the captured image.

FIG. 3 is a block diagram showing functions of the microcomputer for controlling the operations of the RAW compression unit and the RAW expansion unit.
The microcomputer 17 includes an AE control unit 71, an AF control unit 72, a composite image generation unit 73, and a compression / decompression control unit 74.

  The AE control unit 71 determines whether or not the current control value (exposure control value) for the exposure adjustment function is appropriate based on the luminance detected by the detection unit 43. If not, the exposure control is performed. Update the value to the optimum value. Further, the AE control unit 71 may perform the above determination process based on the integral value of the luminance for each frame (or for each predetermined region in one frame) from the detection unit 43. In addition, the AE control unit 71 is not based on the detection value based on the captured image data by the detection unit 43 but based on the detection result by the brightness detector separately provided in the imaging device, or the detection result and detection by the detection unit 43. The exposure control value may be calculated based on both values.

  Such determination of the exposure control state is executed when a still image is captured, for example, when the shutter release button in the input unit 18 is half-pressed. Further, at the time of capturing a moving image, it is executed at least during recording of moving image data (for example, at regular intervals). Even when a still image is captured, the exposure control state may be determined at regular intervals.

  The AE control unit 71 controls the exposure state, the exposure mechanism control signal for controlling the opening degree of the iris and the shutter speed (exposure time) in the optical block 11, and the gain application amount in the gain adjustment unit 44. And a gain control signal for controlling. The AE control unit 71 basically applies a gain to the gain adjustment unit 44 when the shooting scene is dark and sufficient brightness cannot be obtained even by controlling the iris and shutter speed. Instruct. The exposure mechanism control signal is supplied to the driver 11a and the TG 12a. The gain control signal is output to the gain adjustment unit 44 and also supplied to the compression / decompression control unit 74.

  The AF control unit 72 calculates a focus lens control signal for driving the focus lens in the optical block 11 based on the high frequency component detected by the detection unit 43. Here, for example, the detection unit 43 performs low-pass filter processing on the input image data, integrates the processed data for each frame (or for each predetermined region in one frame), and uses the integrated value as a high frequency component. Output.

  For example, the AF control unit 72 performs a focusing process when the shutter release button is half-pressed or at regular intervals. The focusing is performed, for example, by moving the focus lens little by little to acquire a high frequency component each time and moving the focus lens so that the high frequency component is maximized.

  The composite image generation unit 73 generates composite image data to be combined on the image in the display processing unit 47. As an example, a histogram (luminance histogram) indicating the frequency for each luminance in one frame is acquired from the detector 43, and composite image data representing the luminance histogram is generated. When display of the luminance histogram is requested by an operation input by the photographer, the combined image data of the luminance histogram at that time is output to the display processing unit 47. Thereby, the photographer can visually recognize the luminance histogram displayed on the display 16 and recognize the luminance distribution of the captured image.

  The compression / expansion control unit 74 turns on / off the compression / expansion processing in the RAW compression unit 41 and the RAW expansion unit 42 based on the gain control signal from the AE control unit 71, the high frequency component from the detection unit 43, and the luminance histogram. To control. This control processing procedure will be described in detail with reference to FIG.

FIG. 4 is a flowchart showing a control processing procedure by the compression / decompression control unit.
[Step S1] The compression / decompression control unit 74 acquires the latest gain control signal output from the AE control unit 71.

  [Step S2] The compression / decompression controller 74 compares the gain amount based on the acquired gain control signal with a preset gain amount threshold value. If the gain amount based on the gain control signal is less than the threshold value, the process of step S3 is executed. If the gain amount based on the gain control signal is equal to or greater than the threshold value, the process of step S9 is executed. To do.

  [Step S3] The compression / expansion control unit 74 acquires the latest high-frequency component detected by the detection unit 43. As described above, the amount of the high frequency component is acquired as, for example, a value obtained by integrating data obtained by performing low-pass filter processing on input image data for each frame (or for each predetermined region in one frame).

  [Step S4] The compression / expansion control unit 74 compares the amount of the acquired high frequency component with a preset threshold value of the high frequency component. When the amount of the acquired high frequency component is less than the threshold value, the process of step S5 is executed. When the amount of the acquired high frequency component is equal to or greater than the threshold value, the process of step S9 is executed.

[Step S5] The compression / decompression control unit 74 acquires the latest luminance histogram detected by the detection unit 43.
[Step S6] The compression / decompression control unit 74 calculates the dynamic range of the imaging scene based on the acquired luminance histogram.

Here, FIG. 5 is a diagram for describing the dynamic range calculation method in step S6.
5A and 5B show examples of luminance histograms acquired in step S5. When acquiring the luminance histogram, the compression / decompression control unit 74 detects a minimum luminance value and a maximum luminance value whose frequency (that is, the number of pixels) is equal to or higher than a predetermined threshold value Pth (where Pth> 0), A difference between the minimum luminance value and the maximum luminance value is defined as a dynamic range. In the example of FIG. 5, the image having the luminance histogram (A) has a wider dynamic range than the image having the luminance histogram (B).

Hereinafter, description will be made with reference back to FIG.
[Step S7] The compression / decompression control unit 74 compares the calculated dynamic range with a preset dynamic range threshold. If the calculated dynamic range is less than the threshold value, the process of step S8 is executed. If the calculated dynamic range is equal to or greater than the threshold value, the process of step S9 is executed.

[Step S8] The compression / decompression control unit 74 turns on both the compression processing function by the RAW compression unit 41 and the expansion processing function by the RAW expansion unit 42.
[Step S9] The compression / decompression control unit 74 sets both the compression processing function by the RAW compression unit 41 and the decompression processing function by the RAW expansion unit 42 to an off state (that is, a state in which input image data is output as it is).

  The above-described processing of FIG. 4 is executed each time image data for one frame is output from the A / D conversion circuit 13, for example. For example, when capturing a still image, in the monitoring state before image recording, the RAW compression unit 41 and the RAW expansion unit 42 are always on (or always off), and the shutter release button is half-pressed. The on / off state of the RAW compression unit 41 and the RAW expansion unit 42 may be controlled by processing. Similarly, when a moving image is picked up, the recording standby state is always on (or always off), and the on / off state is controlled by the above process during the period from the start to the end of recording. Good.

  In addition, for example, in the imaging mode that prioritizes image quality and the imaging mode that prioritizes speed, the control processing that is fixed in the on state or the off state and the variable control processing in the on / off state by the above processing may be used separately. Good. For example, the imaging mode that prioritizes image quality may always be in the off state, and in the imaging mode that prioritizes speed, the on / off state may be controlled by the above processing. In addition, the on / off state may be controlled by the above processing only in an imaging mode (continuous shooting mode) in which continuous shooting is performed at high speed.

  In addition, for example, when the function of performing pixel addition is provided in the output circuit of the image sensor 12, or when the function of outputting only the pixel signal of the central region of the light receiving surface is provided in the image sensor 12, etc. When the resolution of the image data output from the A / D conversion circuit 13 changes, a control process that is fixed in an on state or an off state according to the resolution, and a variable on / off state by the above process. You may make it use a control process properly. For example, when the resolution is low, it is always in the off state, and when the resolution becomes a certain value or more, the on / off state control by the above processing may be performed. In addition, even when the frame rate of the image data output from the A / D conversion circuit 13 is variable, the control processing is fixed in the on state or the off state in accordance with the frame rate, and the on / off state by the above processing. You may make it use properly the variable control process of a state.

  Further, the threshold values in the above steps S2, S4, and S7 are basically determined according to the characteristics of image quality change by the compression / expansion processing in the RAW compression unit 41 and the RAW expansion unit 42. The threshold value may be changed according to the user's operation. Further, for example, depending on whether the shutter release button described above is half-pressed, whether there is a recording request, various imaging mode settings, the resolution of image data output from the A / D conversion circuit 13, the frame rate, etc. The threshold values may be automatically changed. For example, in the continuous shooting mode, each threshold value is set higher than in the other imaging modes, so that processing for each frame in the digital image processing circuit 14 is ensured within a desired continuous shooting period. It becomes possible to execute.

  By the control of the compression / decompression control unit 74 as described above, the condition that the gain amount for the captured image data is a certain value or more, the condition that the amount of the high frequency component of the captured image data is a certain value or more, the dynamic range of the captured image data When at least one of the conditions in which the value is equal to or greater than a certain value is satisfied, the compression / decompression function of the RAW compression unit 41 and the RAW expansion unit 42 is turned off. This shortens the time required for writing RAW image data to the image memory 15 and reading RAW image data from the image memory 15 via the memory bus 15a, thereby speeding up the process and reducing power consumption. While achieving the effect, it is possible to prevent image quality deterioration that may occur due to compression / decompression processing.

  The compression / expansion control unit 74 also performs conventional imaging such as a gain control signal from the AE control unit 71, a high-frequency component detected for AF control, and a luminance histogram detected for display on the display 16. On / off of the compression / decompression function is controlled using information used in the apparatus. Therefore, it is not necessary to significantly change the internal configuration of the conventional imaging device in order to perform the on / off control of the compression / decompression function, and the development / manufacturing cost of the imaging device can be suppressed.

  Next, the RAW image data compression / decompression technique applied in the present embodiment will be described. In this embodiment, as will be described below, a lossy compression / decompression method that can perform fixed-length encoding, maintain good image quality, and can be realized with relatively simple processing. adopt.

  Here, by enabling encoding of fixed length, the bandwidth of RAW image data to be read from and written to the image memory 15 can be kept constant, and the transmission load on the memory bus 15a can be stably reduced. In addition, by performing fixed-length encoding, processing such as reading address designation when data is read from the image memory 15 to the detection unit 43 is simplified.

  In the following example, the raw image data signal is fixed at 14 bits per pixel, the quantization word length is fixed at 7 bits, and 16 horizontal pixels having the same color component are converted into encoded data of one block. . For example, 14-bit data occupies a 16-bit area in the image memory 15. As described above, assuming that 16 pixels are one block, when RAW image data corresponding to one block is recorded in the image memory 15 without being compressed, an area of 256 bits is occupied. Such a recording area can be compressed to 128 bits, and a compression ratio of 1/2 can be achieved.

FIG. 6 is a block diagram showing an internal configuration of the RAW compression unit.
As shown in FIG. 6, the RAW compression unit 41 includes a polygonal line compression unit 101, a blocking unit 102, a maximum / minimum detection unit 103, a minimum value latch unit 104, a maximum value latch unit 105, a minimum value address latch unit 106, a maximum value, A value address latch unit 107, subtracters 108 and 109, a quantizer 110, a quantized data buffer 111, and a packing unit 112 are provided.

  The polygonal line compression unit 101 nonlinearly compresses the input 14-bit RAW image data into 11-bit data by approximation using a polygonal line. The broken line compression unit 101 is provided for the purpose of improving the overall compression efficiency by reducing the gradation as much as possible before the subsequent compression procedure. For this reason, it may be omitted depending on the target compression rate. In this case, it is also necessary to omit the reverse broken line conversion unit provided at the output stage of the RAW expansion unit 42 described later with reference to FIG.

Here, FIG. 7 is a figure which shows the example of the broken line used in a broken line compression part.
FIG. 7 shows an example in which the gradation of the input data is converted by straight lines having five inclinations divided by four points. In this example, in accordance with human visual characteristics, a higher gradation is assigned as input data is smaller, that is, darker (or lighter in color). Such a broken line may be prepared for each color component, for example, and may be used by switching for each color component of the input pixel.

  In the polygonal line compression unit 101, for example, after converting the gradation of the input data using such a polygonal line, the converted data is divided by 8 (that is, shifted downward by 3 bits) to become 11-bit data. Compress. At this time, the discarded lower bits are rounded off, for example. Alternatively, the polygonal line compression unit 101 prepares a ROM table that stores the input data and the compressed output data in association with each other based on the above calculation, and the input / output data is converted according to the ROM table. Also good.

Hereinafter, the description will be returned to FIG.
The block forming unit 102 divides the data output from the polygonal line compression unit 101 into blocks composed of the same color component pixels for 16 pixels adjacent in the horizontal direction, and outputs the blocks for each separated block. Thereby, the correlation of the data in a block becomes strong, and the image quality deterioration by subsequent quantization processing can be suppressed.

  For example, when the Bayer array image sensor 12 is used, in the output data, the repetition of the R component and the Gr component and the repetition of the B component and the Gb component appear for each line. As an example, when the R component and the Gr component repeatedly appear in the input data to the blocking unit 102 such as R0, Gr0, R1, Gr1,..., R15, Gr15, R0, R1, R2,. .., R15, Gr0, Gr1,..., Gr15, the output order is changed so that 16 pixels of the same color component appear continuously, and the blocks are formed.

  The maximum / minimum detection unit 103 detects the maximum value and the minimum value in one block. Specifically, the maximum value and minimum value in one block, and the addresses indicating the number of pixels having the maximum value and minimum value from the beginning of one block (hereinafter referred to as maximum value address and minimum value address). ) Is detected. The maximum value address and the minimum value address are detected as address values of 0 to 15, respectively.

  However, considering the case where there are multiple pixels with the same value in the block and the value is the maximum value or the minimum value, the following determination rules are used for determining the maximum value and the minimum value: By providing this, confusion in compression / decompression processing is avoided. First, in determining the maximum value, as the initialization operation, the value of the 0th pixel is captured as a temporary maximum value (temporary maximum value). Next, for the first to fifteenth pixels, if the value is not less than the temporary maximum value, the temporary maximum value is updated with the value of that pixel. Thereby, the temporary maximum value after the determination of the 15th pixel is determined as the maximum value in the block.

  In determining the minimum value, similarly, as the initialization operation, the value of the 0th pixel is taken in as a temporary minimum value (temporary minimum value). Next, for the 1st to 15th pixels, if the value is less than the temporary maximum value, the temporary minimum value is updated with the value of the pixel. Thereby, the temporary minimum value after the determination of the 15th pixel is determined as the minimum value in the block.

  For example, of the 16 pixels, when the first two pixels (0th and 1st) have the same maximum value, the maximum value address is “1”. When all 16 pixels have the same value, the minimum value address is “0” and the maximum value address is “15”.

  The maximum / minimum detection unit 103 outputs the detected minimum value and maximum value to the minimum value latch unit 104 and the maximum value latch unit 105, respectively, and the minimum value address and the maximum value address are respectively output to the minimum value address latch unit. 106 and the maximum value address latch unit 107. Further, the input data for one block is sequentially output to the subtracter 108 after the maximum and minimum determinations of the block are completed.

  The minimum value latch unit 104 and the maximum value latch unit 105 latch the minimum value and the maximum value from the maximum / minimum detection unit 103, respectively. Further, the minimum value address latch unit 106 and the maximum value address latch unit 107 latch the minimum value address and the maximum value address from the maximum / minimum detection unit 103, respectively. The minimum value latch unit 104, the maximum value latch unit 105, the minimum value address latch unit 106, and the maximum value address latch unit 107 are used until the block corresponding to the input data is encoded in the packing unit 112. Latch input data.

  The subtracter 108 subtracts the minimum value of the corresponding block output from the minimum value latch unit 104 from the pixel data output from the maximum / minimum detection unit 103. This subtraction is equivalent to subtracting the DC offset common to the pixels in one block from the data of each pixel.

  The subtractor 109 subtracts the minimum value of the corresponding block output from the minimum value latch unit 104 from the maximum value output from the maximum value latch unit 105. This subtraction result indicates the dynamic range (DR) at the time of quantization.

  The quantizer 110 quantizes the output data of the subtracter 108 according to the size of the dynamic range output from the subtractor 109. In this embodiment, as an example, quantization is performed with a fixed length of 7 bits.

  As the quantizer 110, for example, a configuration in which the output data of the subtractor 108 is divided by the dynamic range using an integer type divider can be applied. Also, when the quantization step is limited to a power of 2, a bit shifter that operates as follows can be applied, thereby reducing the circuit scale. If such a bit shifter is used on the compression processing side, the circuit scale can be similarly reduced in the inverse quantization on the decompression processing side.

When the 11-bit input data from the subtracter 108 is quantized into 7-bit data, for example, the following shift operation may be performed.
[When 0 ≦ DR ≦ 127] The input data is output as it is.

[When 128 ≦ DR ≦ 255] The input data is shifted downward by one bit.
[When 256 ≦ DR ≦ 511] The input data is shifted down by 2 bits.
[When 512 ≦ DR ≦ 1023] The input data is shifted downward by 3 bits.

[When 1024 ≦ DR ≦ 2047] The input data is shifted downward by 4 bits.
The quantized data buffer 111 temporarily holds the quantized data for 16 pixels output from the quantizer 110.

  The packing unit 112 uses the output data from the quantized data buffer 111, the minimum value latch unit 104, the maximum value latch unit 105, the minimum value address latch unit 106, and the maximum value address latch unit 107 to 128 per block. Pack into bit compressed data. The packing unit 112 reads out the quantized data corresponding to each pixel from the quantized data buffer 111, based on the output data of the minimum value address latch unit 106 and the maximum value address latch unit 107, and the maximum value and the minimum value. The quantized data corresponding to is discarded, and only the quantized data for the remaining 14 pixels in the block is packed as shown in FIG.

FIG. 8 is a diagram showing a configuration of compressed data for one block generated by packing.
As shown in FIG. 8, the compressed data includes a maximum value and a minimum value (both 11 bits) in the block, a maximum value address and a minimum value address (both 4 bits) corresponding to these values, a maximum value and It consists of quantized data (98 bits) for 14 pixels excluding the pixel having the minimum value.

  Here, since the maximum value and the minimum value in the block are packed, the corresponding quantized data is omitted, and instead, the maximum value address and the minimum value address indicating the positions of these pixels are packed. The original data can be restored when decompressing. Since the quantized data is 7 bits, the address is 4 bits because of 16 addresses, and from these differences, a reduction effect of 6 bits can be obtained by combining the maximum value and the minimum value per block. As described above, 128-bit data obtained by compressing RAW image data for 16 pixels occupying a memory area for 256 bits to ½ is obtained.

Next, FIG. 9 is a block diagram showing an internal configuration of the RAW expansion unit.
As shown in FIG. 9, the RAW decompression unit 42 includes a data latch unit 201, a selector 202, a subtractor 203, an inverse quantizer 204, an adder 205, an address counter 206, an address comparison unit 207, a selector 208, and an inverse polygonal line transform. A unit 209 and a dot sequential processing unit 210.

  The data latch unit 201 latches 128-bit compressed data read from the image memory 15. The data latch unit 201 latches the input data until all the blocks corresponding to the input data are processed in the selector 208.

  The selector 202 receives quantized data (98 bits) among the data latched by the data latch unit 201, and sequentially selects 7-bit data corresponding to one pixel from the data, and performs inverse quantization. To the container 204.

  The subtracter 203 receives the maximum value (11 bits) and the minimum value (11 bits) among the data latched by the data latch unit 201, subtracts the minimum value from the maximum value, and outputs the dynamic range.

  The inverse quantizer 204 inversely quantizes the quantized data for each pixel from the selector 202 according to the size of the dynamic range. In this embodiment, a 7-bit fixed length code is inversely quantized and 11-bit data is output.

  As the inverse quantizer 204, for example, a configuration of multiplying quantized data and a dynamic range by using an integer multiplier can be applied. Further, as described in the description of the quantizer 110 above, when the quantization step is limited to a power of 2, the quantization can be configured by a bit shifter, thereby reducing the circuit scale. it can. This bit shifter operates, for example, as follows.

[When 0 ≦ DR ≦ 127] The input data (quantized data) is output as it is.
[When 128 ≦ DR ≦ 255] The input data is shifted upward by one bit.
[When 256 ≦ DR ≦ 511] The input data is shifted upward by 2 bits.

[When 512 ≦ DR ≦ 1023] The input data is shifted upward by 3 bits.
[When 1024 ≦ DR ≦ 2047] The input data is shifted upward by 4 bits.
The adder 205 adds the output data of the inverse quantizer 204 and the minimum value latched by the data latch unit 201. As a result, a common DC offset value in the block is added to the dequantized data.

The address counter 206 performs a count-up operation in accordance with the pixel output timing, and generates a count value (0 to 15) corresponding to the pixel order in the block.
The address comparison unit 207 receives the maximum value address and the minimum value address among the data latched by the data latch unit 201, compares it with the count value from the address counter 206, and if it matches the value of each address, the selector A selection signal is output to 208.

  The selector 208 selects and outputs the data from the adder 205 and the maximum and minimum values from the data latch unit 201. Specifically, when the selection signal corresponding to the maximum value address is received from the address comparison unit 207, the maximum value from the data latch unit 201 is selected and output, and the selection signal corresponding to the minimum value address is received. Selects and outputs the minimum value from the data latch unit 201, otherwise selects and outputs the data from the adder 205. Thereby, the data of the same color pixel compressed to 11 bits is expanded in pixel order.

The reverse broken line conversion unit 209 expands the data from the selector 208 from 11 bits to 14 bits with the reverse characteristics of the broken line compression unit 101 of the RAW compression unit 41.
Here, FIG. 10 is a diagram illustrating an example of a polygonal line used in the reverse polygonal line conversion unit.

  The polygonal line in FIG. 10 is adapted to convert the gradation by characteristics opposite to those of the polygonal line compression unit 101 shown in FIG. The inverse broken line conversion unit 209 first multiplies the input data by 8 (that is, shifts upward by 3 bits) to 14 bits, and then performs gradation conversion using the broken line in FIG. 10 to obtain 14-bit pixel data. Stretch. A ROM table in which input data and decompressed output data are stored in association with each other may be prepared, and input / output data conversion may be performed according to the ROM table.

If compression by the polygonal line compression unit 101 is not applied at the time of compression, data conversion by the reverse polygonal line conversion unit 209 is also bypassed at the time of decompression.
Hereinafter, the description will be returned to FIG.

  The point-sequential processing unit 210 converts the decompressed data into the pixel order of the original RAW image data and outputs it by a process reverse to the blocking performed by the blocking unit 102 of the RAW compression unit 41. For example, this is the case when 16 pixels of the same color component are blocked and compressed such that R0, R1, R2,..., R15, Gr0, Gr1,. Are rearranged so that the R component and the Gr component appear repeatedly, such as R0, Gr0, R1, Gr1,..., R15, Gr15. In order to perform such rearrangement, the dot-sequential processing unit 210 includes a buffer memory for holding the expanded data for two blocks, and when the data for two blocks are accumulated in the buffer memory, Data of each color component is output alternately.

  According to the RAW compression unit 41 and the RAW expansion unit 42 having the above-described configuration, the quantization word length per pixel at the time of compression is set to a fixed length, so that compression can be performed by performing fixed-length encoding. Therefore, the bandwidth of data read / written to / from the image memory 15 through the memory bus 15a can be reduced to a certain level, and address management for the image memory 15 can be simplified.

  In addition, since the compression rate is determined by the combination of the number of pixels of one block to be compressed and the quantization word length, the required image quality (that is, the amount of allowable compression distortion) and the allocation of the transmission band on the transmitted bus Therefore, it is possible to flexibly cope with the read / write performance of the image memory 15. For example, as in the above-described embodiment, if the RAW image data for 16 pixels is quantized with a quantization word length of 7 bits, the compression rate is ½, but a normal natural image The PSNR (Peak Signal to Noise Ratio) at the time of conversion into a luminance / color difference signal after compression / expansion can be maintained at about 50 dB. If the PSNR of this signal is about 50 dB to 40 dB, the compression distortion can be suppressed to such an extent that it cannot be detected with the naked eye.

  In addition, since compression / decompression processing is basically executed by one-dimensional processing, for example, a line memory for referring to pixel data of the upper and lower lines becomes unnecessary, and processing becomes relatively simple. For this reason, the circuit scale for compression / decompression and the manufacturing cost can be suppressed, and the effect of speeding up the processing and shortening the processing time can be enhanced. That is, the effect of shortening the read / write time of the RAW image data in the image memory 15 and the effect of reducing the transmission load of the memory bus 15a can be reliably improved.

  Accordingly, it is possible to realize an image pickup apparatus that can record / display a high-quality image at a high speed during image pickup, and that is small in size and relatively low in manufacturing cost. Then, the compression / decompression function of the RAW compression unit 41 and the RAW expansion unit 42 is adaptively turned on / off under the control of the compression / decompression control unit 74 described above, thereby minimizing image quality degradation due to compression / decompression processing. Can be fastened.

  That is, in the above compression / decompression method, since lossy compression is performed, image quality degradation caused by compression / decompression may become more conspicuous as the amount of gain applied to image data increases. The controller 74 can prevent such image quality deterioration by turning off the compression / decompression function when the gain application amount is a certain value or more. In the compression / decompression method described above, fixed-length packing is performed in units of a fixed number of pixels, and the compression rate can be varied according to the dynamic range. Therefore, an image with a high frequency component or an image with a wide dynamic range is used. Therefore, there is a high possibility that image quality deterioration due to compression / decompression will increase. However, the compression / decompression control unit 74 can prevent such image quality deterioration by turning off the compression / decompression function when the amount of high-frequency components and the dynamic range are equal to or greater than a certain value.

  In the compression method described above, when the quantization step is a power of 2, the quantizer can be configured by a bit shifter. In this case, the shift amount indicates the dynamic range in the block. Here, when the maximum value in the block is quantized, it is obvious that all the bits thereof are 1. Therefore, on the expansion side, instead of the absolute value of the maximum value, the maximum value of the quantum value is calculated from the shift amount. Can be obtained and expanded.

  Therefore, by storing the shift amount (at least 3 bits in the above operation example) in the quantizer instead of the maximum value (11 bits) in the compressed data, the number of bits of data to be stored in the compressed data is reduced. be able to. Therefore, the image quality can be improved by further increasing the compression rate or increasing the quantization word length.

  In the above description, an example in which RAW image data is blocked and compressed for each line has been shown. However, the above compression / decompression method can be applied to block each rectangular area over a plurality of lines. It is. For example, when an image sensor capable of reading out all pixels (progressive reading) such as a CMOS sensor is used, the pixel data is read out sequentially, so that the correlation of the pixel data with respect to the vertical direction becomes strong. Therefore, even if the pixels in the rectangular area are blocked, the compression can be performed without degrading the image quality. Furthermore, the rectangular area to be blocked can be made the same as the detection frame applied by the detection unit 43.

It is a block diagram which shows the principal part structure of the imaging device which concerns on embodiment of this invention. It is a block diagram which shows the internal structure of a digital image processing circuit. It is a block diagram which shows the function with which a microcomputer is provided in order to control operation | movement of a RAW compression part and a RAW expansion | extension part. It is a flowchart which shows the control processing procedure by a compression / decompression control part. It is a figure for demonstrating the calculation method of a dynamic range. It is a block diagram which shows the internal structure of a RAW compression part. It is a figure which shows the example of the broken line used in a broken line compression part. It is a figure which shows the structure of the compressed data for 1 block produced | generated by packing. It is a block diagram which shows the internal structure of a RAW expansion | deployment part. It is a figure which shows the example of the broken line used in a reverse broken line conversion part.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Optical block, 11a ... Driver, 12 ... Image sensor, 12a ... Timing generator, 13 ... A / D conversion circuit, 14 ... Digital image processing circuit, 15 ... Image memory, 15a ... Memory Bus, 16 ... Display, 17 ... Microcomputer, 18 ... Input section, 19 ... Memory card I / F, 19a ... Memory card, 20 ... Flash memory, 21 ... Built-in memory, 41 ... RAW Compression unit 42... Raw expansion unit 43. Detection unit 44. Gain adjustment unit 45. WB adjustment / YC conversion unit 46. Resolution conversion / compression expansion unit 47. Display processing unit 71... AE control unit, 72... AF control unit, 73... Composite image generation unit, 74.

Claims (18)

In an imaging device that captures an image using a solid-state imaging device,
A compression unit that compresses image data captured by the solid-state imaging device and converted into digital data by an irreversible compression method, and outputs compressed image data;
A memory that temporarily holds the compressed image data output from the compression unit;
A decompression unit for decompressing the compressed image data read from the memory;
A signal processing unit that performs predetermined signal processing including gain application processing on the image data expanded by the expansion unit;
The signal processing unit switches between an on state in which the compression unit and the decompression unit respectively execute a compression operation and an expansion operation, and an off state in which the compression operation and the decompression operation are stopped and input image data is output as it is. A compression / expansion control unit that switches the compression operation and the expansion operation to the off state when a gain application amount is equal to or greater than a predetermined gain threshold;
An imaging device comprising: An exposure control unit for automatically controlling an exposure adjustment function including the gain application processing function in the signal processing unit according to the brightness of the imaging scene;
The imaging apparatus according to claim 1, wherein the compression / expansion control unit determines the gain application amount based on a gain control signal output from the exposure control unit and corresponding to the gain application processing function.   The imaging apparatus according to claim 1, wherein the gain threshold set in the compression / decompression control unit is variable.   The imaging apparatus according to claim 3, wherein the compression / decompression control unit automatically sets the gain threshold value to a higher value in an imaging mode in which speed is prioritized over image quality.   The compression / decompression control unit further performs the compression operation and the decompression operation in the off state even when the amount of the high frequency component of the image data output from the decompression unit is equal to or greater than a predetermined component amount threshold value. The imaging apparatus according to claim 1, wherein the imaging apparatus is switched to A high-frequency component detection unit for detecting the amount of high-frequency components from the image data output from the expansion unit;
A focus control unit that calculates a focus control value for moving the focus lens to the in-focus position based on the detection result by the high-frequency component detection unit;
Further comprising
The compression / expansion control unit compares the detection result by the high-frequency component detection unit with the component amount threshold value to determine whether or not to set the compression operation and the expansion operation to the off state. The imaging apparatus according to claim 5, wherein:   The compression / expansion control unit further switches the compression operation and the expansion operation to the off state even when the dynamic range of the image data output from the expansion unit is equal to or greater than a predetermined range threshold value. The imaging apparatus according to claim 1. A histogram detection unit for detecting a histogram indicating the frequency for each luminance in one frame unit from the image data output from the decompression unit;
The imaging apparatus according to claim 7, wherein the compression / decompression control unit determines the dynamic range based on the histogram detected by the histogram detection unit.   The imaging apparatus according to claim 8, further comprising a display unit that displays an image based on the histogram detected by the histogram detection unit.   The compression unit compresses the digitally converted image data in units of blocks each including a predetermined number of pixel data, and outputs the compressed image data as fixed-length encoded data. Imaging device.   The compression unit includes a maximum value and a minimum value of the pixel data in a block composed of a predetermined number of pixel data, position information in the block, and the block in the block excluding the maximum value and the minimum value. The imaging apparatus according to claim 1, wherein the compressed image data including quantized data obtained by quantizing a subtraction value obtained by subtracting the minimum value from the pixel data is generated. The compression unit is
For each block, a maximum / minimum detection unit that detects the maximum value and the minimum value of the pixel data, and the position information in the block, and
A quantization unit that quantizes the subtraction value obtained by subtracting the minimum value in the corresponding block from the pixel data according to a dynamic range calculated as a difference value between the maximum value and the minimum value in the block. When,
For each block, the maximum value and the minimum value in the block, the position information thereof, and the quantized data quantized by the quantization unit, corresponding to the maximum value and the minimum value A packing unit that packs the quantized data except for generating the compressed image data;
The imaging apparatus according to claim 11, further comprising:   The imaging apparatus according to claim 12, wherein a quantization word length in the quantization unit is a fixed value.   The compression unit further includes a pre-compression unit that converts the gradation of the digitally converted image data according to human visibility characteristics and then supplies the compressed data to the compression unit after reducing the number of bits. The imaging apparatus according to claim 12.   13. The imaging apparatus according to claim 12, wherein the quantization unit quantizes the subtraction value with a bit shifter that shifts the number of steps lower by a number corresponding to the dynamic range, with a quantization step being a power of 2. .   The imaging apparatus according to claim 15, wherein the packing unit packs a shift amount in the bit shifter instead of the maximum value in the block. The extension part is
Inverse quantization for dequantizing the quantized data extracted from the compressed image data for each block according to the dynamic range calculated as a difference value between the maximum value and the minimum value extracted from the compressed image data And
An adder for adding the minimum value to the data dequantized by the dequantization unit;
Based on the position information of the minimum value and the maximum value extracted from the compressed image data for each block, the maximum value, the minimum value, and the output value from the adding unit are sent to the compression unit. An output control unit that outputs the input original pixel data in the order;
The imaging apparatus according to claim 12, further comprising: In an imaging method for imaging an image using a solid-state imaging device,
The compression unit compresses the image data imaged and digitally converted by the solid-state imaging device by an irreversible compression method, outputs the compressed image data, and temporarily stores it in the memory.
An expansion unit expands the compressed image data read from the memory;
The signal processing unit performs predetermined signal processing including gain application processing on the image data expanded by the expansion unit,
An on state in which the compression / decompression control unit causes the compression unit and the decompression unit to perform a compression operation and an expansion operation, respectively, and an off state in which the compression operation and the decompression operation are stopped and input image data is output as it is. Switching, when the gain application amount in the signal processing unit is equal to or greater than a predetermined gain threshold value, the compression operation and the expansion operation are switched to the off state,
An imaging method characterized by the above.

Images