JP2006129522A - Image pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform constant rate control without prolonging a time for recording an image in a recording medium. <P>SOLUTION: An image pickup device is provided with an index value calculating circuit 16 for extracting an index value for predicting a code amount in compression from a video signal acquired from a CCD (solid-state image pickup element) 12; and a compression coefficient control circuit 17 for controlling a compression rate to be used in an image compression unit 18, on the basis of the index value acquired by the circuit 16. The circuit 17 uses an index value obtained by the circuit 16 at the time of photographing image confirming operation before image pickup, and decides the compression rate at the time of the image pickup operation. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an imaging apparatus that performs image compression processing in a digital color imaging apparatus.

  FIG. 1 is a diagram showing a schematic configuration of a conventional digital still camera disclosed in, for example, Japanese Patent Laid-Open No. 11-331672, and does not require a frame memory for storing image data before compression. 1 shows a configuration of a camera.

  In FIG. 1, 11 is an imaging lens, 12 is a shutter that also serves as an aperture, 13 is a CCD that is a photoelectric conversion element, 14 is an analog signal processor (CDS / AGC), 15 is an AD converter, and 16 is a timing generator (TG). , 17 is a digital signal processing unit (DSP), 18 is an image compression unit (JPEG encoder), 20 is a flash memory, 21 is a memory card interface (PCMCIA I / F), and 22 is a control unit.

  The imaging lens 11 forms an image of light from the subject to be photographed on the light receiving surface of the CCD 13. The aperture / shutter 12 regulates the amount of light received by the CCD 13 by regulating the beam diameter from the imaging lens 11 to the CCD 13, and closes when a predetermined time has elapsed after the CCD 13 starts photoelectric conversion, thereby reducing the exposure time of the CCD 13. Restrict. The CCD 13 is formed by alternately arranging several hundreds of thousands of pixels that are sensitive to red (R), green (G), and blue (B) light in a matrix, and charges the received light for each pixel. Is converted and stored, and the stored charge is output as an analog signal.

  The analog signal processing unit 14 performs double gain sampling on the output signal of the CCD 13 and performs automatic gain processing. The AD converter 15 converts the analog signal input from the analog signal processing unit 14 into a digital signal and outputs the digital signal to the digital signal processing unit 17.

  The timing generator 16 supplies timing signals SH and SV indicating the timing of horizontal scanning and vertical scanning to the CCD 13 via buffers 16a and 16b, respectively. The timing generator 16 also provides the analog signal processing unit 14 with a timing signal SS that indicates when the output signal of the CCD 13 is sampled, and the AD converter 15 with a timing signal SC that indicates when the output signal of the analog signal processing unit 14 is converted. give.

  The digital signal processing unit 17 subjects the output signal of the CCD 13 digitized by the AD converter 15 to processing such as white balance correction, shading, interpolation of signals of three colors R, G and B, and gamma correction. Image data composed of a luminance signal and a color signal is generated. A set of image data generated by the digital signal processing unit 17 represents a captured image of one frame, and can be displayed as it is.

  The image compression unit 18 compresses the image data generated by the digital signal processing unit 17. The image compression unit 18 is a discrete cosine transformer (DCT) 18a that sequentially performs discrete cosine transform on the image data output from the digital signal processing unit 17 for each pixel block of a predetermined size (8 × 8 pixels), and the converted image It comprises a quantizer 18b that quantizes data and a Huffman encoder 18c that encodes quantized image data.

  The flash memory 20 stores the image data compressed by the image compression unit 18. The card interface 21 copies the image data stored in the flash memory 20 to a removable memory card in units of frames. Other devices complying with the JPEG method can reproduce the captured image by reading the copied image data from the memory card and applying the composite, inverse quantization, and inverse discrete cosine transform.

  The control unit 22 adjusts the brightness of the image formed on the CCD 13 by adjusting the opening degree of the diaphragm / shutter 12. In addition, when a release button provided in an operation unit (not shown) is operated and an instruction to start image storage is given, a control signal SO for instructing start of operation is supplied to the image compression unit 18.

  The image compression unit 18 given the control signal SO gives the control signal ST to the timing generator 16. In response to this, the timing generator 16 outputs the timing signals SH, SV, SS, and SC to the CCD 13, the analog signal processing unit 14, and the AD converter 15, and operates each unit at a predetermined timing. The output period of the timing signals SH, SS, and SC is set to 1/8 of the time required for the image compression unit 18 to compress the image data for 8 lines.

  After outputting the control signal ST, the image compression unit 18 gives the control signal SP to the digital signal processing unit 17 when the time required to compress the image data for 8 lines has passed, and the next control signal ST is sent. This is given to the timing generator 16. The control signal SP given to the digital signal processing unit 17 is a signal requesting to output the generated image data for 8 lines. The image compression unit 18 compresses the image data output from the digital signal processing unit 17 in accordance with the control signal SP, and each unit pauses operation until the next instruction is given from the control unit 22.

  The controller 22 keeps the aperture / shutter 12 closed until image storage is instructed by operating the release button, and opens the aperture / shutter 12 to an appropriate range when the release button is operated. When the predetermined time set to approximately 1/30 seconds has elapsed, the diaphragm / shutter 12 is closed again. By this control, the exposure time of the CCD 13 becomes the same as before, and it is possible to prevent the inconvenience that the CCD 13 is saturated or the image taken due to movement of the object to be photographed or camera shake is generated.

  The digital still camera requires a frame memory for temporarily storing the generated image data, and there is a problem that the image data compression process cannot be performed properly without this frame memory. . In view of this problem, the above-described conventional digital still camera does not require a frame memory for storing image data before compression.

  However, since the conventional digital still camera described above eliminates the need for a frame memory by intermittently stopping the operation of the CCD, there is a problem that it takes a long time to capture an image of one frame.

  In the image compression processing, in order to improve usability, the number of compressed images to be recorded on a recording medium is generally determined in advance. Therefore, the recording capacity allocated to an image of one frame is constant regardless of the type of image, and any image data is compressed data close to a certain amount within a range not exceeding the certain amount. This method of compressing data is called constant rate control. In general, the size of the compressed data varies greatly depending on the nature of the image data. Therefore, to perform constant rate control, the parameters of the image compression processing such as the quantization table used in the quantization processing are dynamically changed to a certain amount. Although it is necessary to repeat compression until the following compressed data is obtained, the above-mentioned conventional digital still camera does not have means for dynamically changing parameters during compression, and thus cannot perform constant rate control. .

  As a method for performing constant rate control, for example, in Japanese Patent Laid-Open No. 11-234669, a high frequency component included in a digital signal of an image is extracted using a high-frequency extraction circuit, and an image compression process is performed based on the result. A method for controlling compression parameters is disclosed.

Japanese Patent Laid-Open No. 11-234669

  However, in the digital still camera, the operation state of the CCD and the charge accumulation time in the case where the image data is always displayed on the liquid crystal display device to confirm the image to be photographed and the case where the image is recorded on the recording medium by the shutter operation, In many cases, a setting value such as an incident light amount setting of a diaphragm is changed. This is to improve the operability by reducing the transfer amount of image data when confirming the image to be captured and increasing the update period of the image, while increasing the transfer amount of the image when recording the image and recording a precise image. This is to achieve both purposes. In addition, since the size of the image required for each operation varies depending on the size of the image to be captured and the digital zoom processing, when confirming the image to be captured and when capturing, there are multiple patterns for switching the operating state of the CCD. . When performing constant rate control in such control, it is necessary to control the compression parameters using a high-frequency extraction circuit, etc., with the same CCD and aperture setting conditions, and the image is recorded after the shutter operation is performed. There is a problem that the time until recording on the medium becomes long.

  In addition, since the time until the image is recorded is long, there is a problem that the difference between the image when the shutter operation is performed during imaging of a subject that moves rapidly and the image actually recorded on the recording medium increases. .

  The present invention has been made to solve the above-described problems. When image data is always displayed on a liquid crystal display device in order to confirm an image to be photographed, and when an image is recorded on a recording medium by a shutter operation. The purpose of this is to perform constant rate control without increasing the time during which an image is recorded on a recording medium, even when changing the setting values such as the operating state of the CCD, the charge accumulation time, and the incident light quantity setting of the aperture.

  The imaging apparatus according to the present invention extracts an index value for predicting a code amount at the time of compression from a video signal obtained from a solid-state imaging device, stores an index value calculated over a plurality of frames, and captures an image Index value calculation means for correcting the index value according to the change amount of the index value between frames, and compression coefficient control for determining a compression coefficient to be used in the data compression means based on the index value obtained by the index value calculation means The index value calculation means uses the index value obtained by the index value calculation means during the captured image confirmation operation before imaging, and determines the compression coefficient during the imaging operation. .

  As a result, the image compression and recording operations can be performed immediately after the imaging operation is instructed, and the shutter operation response is improved.

Hereinafter, in order to describe the present invention in more detail, the best mode for carrying out the present invention will be described with reference to the accompanying drawings.
Embodiment 1 FIG.
FIG. 2 is a block diagram showing the configuration of the image pickup apparatus according to Embodiment 1 of the present invention.

  In the figure, 11 is an imaging lens, 12 is a CCD which is a photoelectric conversion element, 13 is an analog signal processing unit (CDS / AGC), 14 is an AD converter, 15 is a digital signal processing unit (DSP), and 16 is compressed from image data. An index value calculation circuit for extracting an index value for predicting the code amount at the time, 17 is a compression coefficient for controlling a compression coefficient used in an image compression unit described later based on the index value obtained by the index value calculation circuit 16 A control circuit, 18 is an image compression unit (JPEG encoder), 19 is a recording medium for recording an image, 20 is a timing generator (TG) for driving a CCD, and 21 is for controlling the operation of each processing part. A control unit 22 is a shutter button.

  Next, the operation will be described.

  First, the imaging lens 11 forms an image of light from a subject to be photographed on the light receiving surface of the CCD 12. The CCD 12 is formed by alternately arranging several hundreds of thousands of pixels that are sensitive to red (R), green (G), and blue (B) light in a matrix, and converts the light received for each pixel into a charge. The accumulated charge is output as an analog signal.

  The CCD 12 has a plurality of drive modes such as a drive mode for sequentially outputting all accumulated charges and a drive mode for sequentially outputting only accumulated charges every other line, and is dynamically driven by the control from the timing generator 20. It has a mechanism that can change the mode.

  The analog signal processing unit 13 performs double correlation sampling on the output signal from the CCD 12 and performs gain control. The AD converter 14 converts the analog signal input from the analog signal processing unit 13 into a digital signal and outputs the digital signal to the digital signal processing unit 15.

  The timing generator 20 gives a timing signal indicating the timing of horizontal scanning and vertical scanning to the CCD 12. Further, it has a function of dynamically switching a plurality of drive modes of the CCD 12 by controlling a signal output from the timing generator 20.

  The digital signal processing unit 15 performs processing such as white balance adjustment, defective pixel correction, R, G, and B3 color signal interpolation, gamma correction, and color conversion on the output signal of the CCD 12 digitized by the AD converter 14. To generate image data composed of a luminance signal and a color difference signal.

  The image compression unit 18 compresses the image data generated by the digital signal processing unit 17. The image compression unit 18 is a discrete cosine transformer (DCT) 18a that sequentially performs discrete cosine transform on the image data output from the digital signal processing unit 17 for each pixel block of a predetermined size (8 × 8 pixels), and the converted image It comprises a quantizer 18b for quantizing data and a Huffman encoder 18c for Huffman encoding quantized image data.

  Further, the image compression unit 18 stores the compressed image data in the storage medium 19. Other devices according to the JPEG system can reproduce the image data by reading the copied image data from the recording medium and performing decoding, inverse quantization, and inverse cosine transform.

  The index value calculation circuit 16 calculates an index value for predicting the code amount at the time of compression from the image data generated by the digital signal processing unit 15. As the index value, for example, a high frequency component of the image signal is extracted and the amount of the frequency component included in the image is digitized.

  The shutter button 22 is operated when the user instructs an imaging operation. The shutter button 22 notifies the control unit 21 that an image recording has been instructed by a user operation.

  When the shutter button 22 is pressed, the control unit 21 switches the operation settings of the timing generator 20, the analog signal processing unit 13, and the digital signal processing unit 15 from the target image confirmation setting to the image shooting setting. In this switching, the respective operation settings at the time of confirming the image to be captured and at the time of capturing vary depending on the captured image size specified by the user, the digital zoom magnification setting, and the like. Therefore, a plurality of switching patterns exist depending on the combination of the respective operation settings at the time of confirming the image to be captured and at the time of imaging. The control unit 21 also notifies the compression coefficient control circuit 17 that the shutter button 22 has been pressed, and changes the operation settings of the timing generator 20, the analog signal processing unit 13, and the digital signal processing unit 15 at that time. Send notifications together.

  The compression coefficient control circuit 17 controls the compression coefficient used by the image compression unit 18 based on the index value calculated by the index value calculation circuit 16. Here, the compression coefficient refers to a parameter (hereinafter referred to as a Q value) for defining the quantization accuracy in the quantizer 18b included in the image compression unit 18. Increasing the Q value increases the quantization accuracy of the data subjected to discrete cosine transform, so that the image quality of the compressed image is improved. Since the amount of codes generated at the same time increases, the size of the generated compressed image data increases.

  Conversely, if the Q value is decreased, the quantization accuracy of the discrete cosine transformed data is lowered, and the image quality of the compressed image is deteriorated. In this case, the generated code amount is reduced, and the size of the generated compressed image data is reduced. Therefore, the compression coefficient control circuit 17 performs control to reduce the Q value when the data size of the generated compressed image data is predicted to increase from the index value output from the index value calculation circuit 16, and the compressed image Keep data size low. If the size of the compressed image data to be generated is predicted to be small, control to increase the Q value is performed to improve the image quality of the compressed image.

  The compression coefficient control circuit 17 according to the first embodiment has a mechanism for receiving a signal from the control unit 21, and the operation of the compression coefficient control circuit 17 is performed when the shutter button 22 is pressed via the control unit 21. Only when notified. This is because the operation of the image compression unit 18 is necessary only when the shutter button 22 is pressed and the compressed image data is stored in the storage medium 19. At this time, the compression coefficient control circuit 17 receives information on how the operations of the timing generator 20, the analog signal processing unit 13, and the digital signal processing unit 15 are changed from the control unit 22, and an index based on the information. The method of controlling the Q value from the index value output by the value calculation circuit 16 is changed.

  The liquid crystal screen 23 is for displaying an imaging target at any time during a captured image confirmation operation before imaging is instructed by the user. At the time of the photographed image confirmation operation, the accumulated charge is intermittently read from the CCD 12 according to the setting of the timing generator 20, and the frame update rate is increased by reducing the time required to read one frame of the image. Improves operability when adjusting the angle of view. In addition, the analog signal processing unit 13 and the digital signal processing unit 15 change the arrangement order of the output image size and pixel data in accordance with the driving mode of the CCD 12, so that the operation setting matching the driving mode of the CCD 12 is performed. Need to be. Since it is not necessary to compress and record the image data at the time of the imaging operation confirmation operation, the image data processed by the digital signal processing unit 15 is directly sent to the liquid crystal screen 23 without passing through the compression processing unit 18. , And displayed as a captured image confirmation image.

  Here, the operation of the compression coefficient control circuit 17 at the time of switching from the photographed image checking operation by the shutter button 22 to the photographing operation will be described in detail.

  FIG. 3 is an explanatory diagram showing the relationship between the index value and the file size. This figure is a graph of the relationship between the index value output from the index value calculation circuit 16 and the file size after compression. In the compression coefficient control circuit 17, correspondence information between the index value corresponding to this graph and the file size is held as data. This data needs to be measured in advance from the compression result when an image is actually taken. Each broken line in the graph of FIG. 3 shows the relationship between the index value and the compressed file size in a specific Q value setting. As the Q value increases, the file size after compression for the same index value increases, so the graph shifts upward. As the Q value decreases, the file size after compression decreases, so the graph shifts downward.

  A method for the compression coefficient control circuit 17 to determine the Q value will be described using the graph of FIG. Here, since the index value corresponding to the image currently being photographed is calculated by the index value calculation circuit 16, the intersection between the index value and a predetermined target file size is obtained. Here, without exceeding the intersection of the target file size and the index value, the uppermost polygonal line represents the maximum Q value that can be used within the range not exceeding the target file size. Therefore, the image compression unit 18 may be controlled with reference to the Q value corresponding to the broken line.

  The above method describes a case where there is no change in system operation settings during an imaging operation. Actually, since the system operation setting is changed during the imaging operation, there is a possibility that the compressed file size based on the Q value determined based on the index value is a value greatly deviating from the target file size.

  FIG. 4 is an explanatory diagram showing an index value correction coefficient table. What is shown is an example of an index value correction coefficient table used to prevent the file size shift as described above. For example, in the imaging operation, when the CCD operation mode is changed from thinning readout to all pixel readout, the coefficient obtained by referring to the section in which thinning readout is performed during the captured image confirmation operation and all pixel readout is performed during the photographing operation. Is multiplied by the calculated index value as a correction coefficient. Thereby, the error of the index value due to the change of the operation setting can be corrected, and an appropriate Q value for the target file size can be obtained.

  The coefficients in the index value correction coefficient table need to be calculated in advance based on the measurement results obtained by measuring changes in index values when the CCD operation mode is actually switched and an image is taken.

  The pattern in which the CCD operation mode changes may vary depending on the photographed image size specified by the user, the digital zoom magnification setting, etc., but combinations of all the operation modes supported by the CCD 12 as shown in FIG. If a table is prepared, an appropriate correction coefficient can be selected regardless of the change pattern.

  As described above, according to the first embodiment, since the index value information before entering the imaging operation is used to appropriately determine the compression parameter at the time of imaging, immediately after the imaging operation is instructed. In addition, image compression and recording operations can be performed, and the response of the shutter operation is improved.

  In addition, since it is not necessary to provide a frame buffer for temporarily recording an uncompressed image, there is an effect that the cost required for the configuration of the imaging apparatus can be reduced.

  In addition, after calculating the index value and performing appropriate correction, the coefficient at the time of compression is determined using the value, so that the operation of the CCD 12 is performed between the imaging operation and the captured image confirmation operation. Even when the modes are different, there is an effect that it is possible to realize constant rate control with little error with respect to the target file size.

  In addition, since correction for changes in the operation settings of the imaging device during the imaging operation is performed using a table, a number of operation switching patterns can be selected depending on the combination of the respective operation settings at the time of shooting target image confirmation and imaging. Even in the case where there is, there is an effect that it is possible to realize constant rate control with less error for all patterns.

  In addition, since the operation of the image compression unit 18 is limited to the imaging operation when the shutter button 22 is operated, there is an effect that power consumption can be reduced and a system with a long battery driving time can be realized.

Embodiment 2. FIG.
In the first embodiment, the index value is a single value, and the compression coefficient control circuit controls the Q value of the image compression unit based on the index value. However, in an imaging apparatus having no frame buffer, the transfer rate of image data after the image compression unit may be limited to a lower value than the transfer rate of image data before the image compression unit. This is expected to reduce the amount of data due to image compression, and aims to reduce the overall cost of the apparatus by ensuring only the necessary minimum transfer rate after image compression. In such an imaging device, even if the compressed data amount of the entire image is controlled so as to match the target data amount, if the compressed data size is locally increased, the data transfer amount exceeds the transfer capability. There is a possibility that a phenomenon that the image compression processing cannot be normally performed may occur.

  An imaging apparatus according to Embodiment 2 that performs appropriate image compression processing using two types of index values in an imaging apparatus that does not have such a frame buffer will be described.

  The imaging apparatus according to the second embodiment is configured similarly to the imaging apparatus according to the first embodiment shown in FIG. Here, the description of the configuration of the imaging apparatus according to Embodiment 2 is omitted.

  Next, the operation will be described.

  The operation of the imaging apparatus according to the second embodiment is substantially the same as that described in the first embodiment, and the description of the same operation as that of the imaging apparatus according to the first embodiment is omitted, and the imaging apparatus according to the second embodiment. The operation which is the feature of the will be described. In the imaging apparatus according to the second embodiment, the operations of the index value calculation circuit 16 and the compression coefficient control circuit 17 shown in FIG. 2 are different from those described in the first embodiment.

  The operations of the index value calculation circuit 16 and the compression coefficient control circuit 17 of the imaging apparatus according to the second embodiment will be described in detail.

  As in the first embodiment, the index value calculation circuit 16 calculates an index value corresponding to the entire surface of the input image, and at the same time, divides the input image into a plurality of areas and calculates an index value for each area. The index value with the largest value among the divided areas is output to the compression coefficient control circuit 17 together with the index value of the entire image as the maximum index value at the time of area division.

  The compression coefficient control circuit 17 determines the limit compression size based on the image data transfer rate after the image compression unit 18 in addition to the predetermined target file size as in the first embodiment.

  If the limit compression size is determined so that the ratio of the pre-compression image size matches the ratio of the image data transfer rate after the image compression unit 18 and before the image compression unit 18, the data transfer amount is transferred locally. The ability will not be exceeded.

  As in the first embodiment, the compression coefficient control circuit 17 refers to the correlation between the index value and the file size shown in FIG. 3 and the index value correction coefficient table shown in FIG. An appropriate Q value for performing the control is obtained. At this time, two values are obtained: the Q value based on the combination of the index value of the entire area of the image and the target file size, and the Q value based on the combination of the maximum index value and the limit file size when the area is divided.

  By controlling the image compression unit 18 using the smaller one of the two Q values, the file size does not exceed the target file size, and the local data transfer amount does not exceed. It is possible to compress the image.

  As described above, according to the second embodiment, in addition to the target file size, the Q value is controlled in consideration of the local file size increase due to the data transfer rate. Even in an imaging apparatus in which the data transfer rate is limited, there is an effect that the most appropriate compressed file size can be controlled in consideration of the transfer rate limitation.

Embodiment 3 FIG.
In the second embodiment described above, only the index value calculated in the immediately preceding frame is used as the index value for predicting the code amount at the time of data compression. At this time, especially when the CCD drive mode at the time of confirming the image to be photographed is thinning readout, and the CCD drive mode is changed from thinning readout to all pixel readout at the time of the imaging operation, the image to be photographed is confirmed by thinning out the image. Since some information is lost in the current image data, there may be a case where a correction error remains even if correction is performed using the index value correction coefficient table of FIG.

  In this case, an imaging apparatus according to Embodiment 3 that further suppresses correction errors based on changes in index values in time series will be described.

  The imaging apparatus according to the third embodiment is configured in the same manner as the imaging apparatus according to the first embodiment shown in FIG. Here, the description of the configuration of the imaging apparatus according to Embodiment 3 is omitted.

  Next, the operation will be described.

  The operation of the imaging apparatus according to the third embodiment is substantially the same as that described in the first embodiment, and the description of the same operation as that of the imaging apparatus according to the first embodiment is omitted, and the imaging apparatus according to the third embodiment. The operation which is the feature of the will be described. In the imaging apparatus according to the third embodiment, the operation of the index value calculation circuit 16 shown in FIG. 2 is different from that described in the first embodiment.

  The index value calculation circuit 16 according to the third embodiment calculates an index value for predicting the code amount at the time of compression based on the image data generated by the digital signal processing unit 15 as in the first embodiment. Here, the index value calculation circuit 16 stores the index values calculated for the latest plural frames.

  For example, considering a case where a high-frequency component of an image is extracted as an index value, the CCD 12 performs correction using a correction coefficient on the index value during thinning readout driving, and the index value when the CCD 12 performs all-pixel readout driving. It is considered that an error occurs during the period when the image contains many specific high-frequency components that can be recognized by all-pixel readout but disappear in the thinning mode. In such a case, an image in the thinning mode has a pixel value that greatly fluctuates depending on the phase relationship between the spacing between the imaging elements on the imaging surface of the CCD 12 and the high-frequency component of the image, so that the index value itself varies greatly with time series. It is expected to be.

  FIG. 5 is an explanatory diagram showing the relationship between the fluctuation range of the index value and the additional correction coefficient. The index value calculation circuit 16 obtains a fluctuation range between the maximum value and the minimum value of the index value from the history of index values stored over a plurality of frames. The large fluctuation range indicates that there are many high-frequency components in the image, and there is a high possibility that the index value in the all-pixel mode is further larger than the correction by the correction coefficient. Therefore, as shown in FIG. 5, a table showing the relationship between the fluctuation range of the index value and the additional correction coefficient is prepared in advance, and the additional correction coefficient corresponding to the fluctuation range of the index value is applied to the index value. Multiply by adding more to the value.

  As described above, according to the third embodiment, since the calculated index value is additionally corrected based on the fluctuation of the index value in time series, the compressed file size can be controlled with higher accuracy. There is an effect that can be performed.

Embodiment 4 FIG.
In each of the above-described embodiments, the relationship data between the compression code amount prediction index value and the file size used in the compression coefficient control circuit 17 and the data of the correction coefficient table are measured in advance and set as fixed data in the circuit. It is necessary to keep. However, when the actual use state is assumed, the above-mentioned various data are greatly affected by the characteristics of the entire imaging apparatus such as the performance of the optical system and the sensitivity characteristics of the CCD 12, and therefore, fixed values are determined from the circuit design stage. It is difficult to keep. Also, if these data are set as complete fixed data, it is not possible to flexibly cope with characteristic changes of the entire apparatus due to changes in the optical system or the like.

  Considering such a situation, an image pickup apparatus according to Embodiment 4 in which data used in the compression coefficient control circuit 17 can be rewritten from the outside by communication means will be described.

  FIG. 6 is a block diagram showing a configuration of an image pickup apparatus according to Embodiment 4 of the present invention. The same reference numerals are used for parts that are the same as or correspond to those shown in FIG. Reference numeral 24 denotes a data table for storing relationship data between the compression code amount prediction index value and the file size used in the compression coefficient control circuit 17 and data of the correction coefficient table.

  The data table 24 has a communication function with the outside and can freely rewrite the setting values of each data stored and held in a memory provided later, for example, using serial communication or the like. .

  Further, the data table 24 includes a nonvolatile memory in which setting values of each stored data are saved even when the settings of the entire imaging apparatus are reset or the power is turned off and then on again.

  Next, the operation will be described.

  The imaging apparatus according to the third embodiment includes the data table 24 in the imaging apparatus according to the first embodiment, and the other configuration is the same and the operation is the same. As described above, the data table 24 includes communication means for performing serial communication with the outside and a non-volatile memory for storing and saving various data. For example, the compression code amount prediction used in the compression coefficient control circuit 17 in advance. The relationship data between the index value and the file size, the data of the correction coefficient table, and the like are stored in the memory. When an instruction is given to change the data setting value from the outside and data to be changed is sent, the data table 24 rewrites the data setting value stored and saved to that sent from the outside. . Other operations are the same as those described in the first embodiment, and a description thereof will be omitted.

  As described above, according to the fourth embodiment, since various data used in the compression coefficient control circuit 17 can be freely rewritten by communication with the outside, the characteristics of the lens 11 and the sensitivity characteristics of the CCD 12 are changed. However, since various data used for compression coefficient control can be changed, there is an effect that it is possible to flexibly cope with a change in the configuration of the apparatus.

  As described above, the imaging apparatus according to the present invention is suitable for implementing an imaging apparatus that performs an image compression and recording operation immediately after an imaging operation is instructed and has a quick response to a shutter operation.

It is a figure which shows schematic structure of the conventional digital still camera. It is a block diagram which shows the structure of the imaging device by Embodiment 1 of this invention. It is explanatory drawing which shows the relationship between an index value and a file size. It is explanatory drawing which shows an index value correction coefficient table. It is explanatory drawing which shows the relationship between the fluctuation range of an index value, and an additional correction coefficient. It is a block diagram which shows the structure of the imaging device by Embodiment 4 of this invention.

Claims (1)

In an imaging apparatus comprising a solid-state imaging device and data compression means for compressing a video signal obtained from the solid-state imaging device,
An index value for predicting the code amount at the time of compression is extracted from the video signal obtained from the solid-state image sensor, and index values calculated over a plurality of frames are stored, and index values between imaging frames are stored. Index value calculation means for correcting the index value according to the amount of change;
Compression coefficient control means for determining a compression coefficient to be used in the data compression means based on the index value obtained by the index value calculation means,
The imaging apparatus according to claim 1, wherein the index value calculation means uses the index value obtained by the index value calculation means during a captured image confirmation operation before imaging, and determines a compression coefficient during the imaging operation.

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