JP2008022164A - Imaging apparatus and method for controlling it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To compress and process an image file by a proper file capacity even when a noise component is increased by the sensibility setting of a camera, the temperature of an imaging device or the like. <P>SOLUTION: An apparatus includes: a signal processing means for varying a gain setting at a time when image data are generated by carrying out a signal processing to an image signal output from the image sensing element; a compression means for compressing the image data generated by the signal processing means while changing a compression parameter in response to image-sensing conditions; and a storage means for storing compression data compressed by the compression process in a recording medium. Even when the noise components are increased by the sensibility setting of the camera, the temperature of the image sensing element, or the like; the time up to a conservation in a memory card by processing images on one screen is not increased remarkably. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image pickup apparatus and a control method for the image pickup apparatus, and more particularly to a technique suitable for converting a subject image into an electric signal, performing a predetermined compression process, and recording it.

  2. Description of the Related Art Conventionally, for example, a digital still camera is known as an imaging device that converts a subject image into an electrical signal, records the image by performing a predetermined compression process. In a conventional digital still camera, a subject image (not shown) imaged on an image sensor by a lens is converted into an electrical signal by the image sensor and output. The electrical signal output from the image sensor is subjected to predetermined processing in the analog signal processing circuit, converted into a digital signal in the AD converter, and supplied to the digital signal processing circuit.

  In the digital signal processing circuit, predetermined processing is further performed to generate image data. The image data generated in the digital signal processing circuit is subjected to predetermined compression processing in the data compression / decompression circuit, and an image file is generated.

  As this compression processing, irreversible JPEG compression processing using DCT processing is generally used. The image file generated in the data compression / decompression circuit is recorded on the memory card via the memory card interface. The above operation is controlled by the control unit in accordance with an operation on an operation member (not shown).

  In the above-described conventional digital still camera, even if the same subject is photographed, if the camera sensitivity setting is set to high sensitivity, the noise component included in the photographed image increases. Also, when the shooting time is longer than the predetermined time, dark current noise in the image sensor included in the shot image increases. Furthermore, even when the temperature of the image sensor 2 is high, such as when the shooting atmosphere is a high temperature environment, the noise component included in the captured image output from the image sensor increases.

  In an image shot under these conditions, the noise component included in the image data after signal processing increases, and the noise component is simultaneously compressed in the data compression / decompression circuit 6. File capacity increases.

  For this reason, an image file having a remarkably large file size is generated depending on the setting state or operating state of the camera. As described above, since the increase in file capacity is due to noise components, the amount of information recorded does not increase even when the file capacity increases. Therefore, there is a problem that the number of images that can be recorded on the memory card is reduced.

  In order to solve such problems, for example, an electronic camera as shown in Patent Document 1 has been proposed. The electronic camera described in Patent Document 1 includes two compression modes, a constant size mode and a constant image quality mode, and can switch between the two compression modes as appropriate. In the constant size mode, the file capacity of the image file is calculated after the compression process once. If the file capacity of the image file exceeds a predetermined value, it is applied when the compression process is performed in the data compression circuit. The parameter has been changed. Then, the compression rate is increased and the image data before compression processing is compressed again. As described above, in the electronic camera described in Patent Document 1, an image file is compressed with an appropriate file capacity.

JP 2001-54115 A

  However, in the compression process described in Patent Document 1 described above, when the noise component increases due to the sensitivity setting of the camera, the temperature of the image sensor, or the like, and the recompression is necessary, the compression process is performed twice, or Depending on the conditions, it had to be done further. For this reason, the conventional digital still camera has a problem that the time required to process an image on one screen and store it on a memory card is remarkably increased.

  SUMMARY OF THE INVENTION In view of the above-described problems, the present invention has an object to enable an image file to be compressed with an appropriate file capacity even if a noise component increases due to the sensitivity setting of the camera or the temperature of the image sensor. Yes.

  An image pickup apparatus according to the present invention includes a signal processing unit having a variable gain setting when image processing is performed on an image signal output from an image pickup device to generate image data, and image data output from the signal processing unit. It has compression means for compressing while changing compression parameters according to imaging conditions, and storage means for storing compressed data output from the compression means in a recording medium.

  An image pickup apparatus control method according to the present invention includes a signal processing step in which gain setting is variable when image data is generated by performing signal processing on an image signal output from an image pickup device, and an image generated in the signal processing step. The method includes a compression step of compressing data while changing a compression parameter according to an imaging condition, and a storage step of storing the compressed data compressed in the compression step in a recording medium.

  According to the present invention, the compression parameter is changed according to the imaging condition. As a result, even if the noise component increases due to the sensitivity setting of the image sensor, temperature, etc., it is possible to compress the image file with an appropriate file capacity, and to process one screen image and save it to the memory card. Time can be prevented from increasing significantly.

(First embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating a configuration example of the imaging apparatus according to the present embodiment.
In FIG. 1, 1 is a lens, 2 is a solid-state imaging device, 3 is an analog signal processing circuit, 4 is an AD converter, 5 is a digital signal processing circuit, 6 is a data compression / decompression circuit, 7 is a control unit, and 8 is a memory card. An interface 9 is a removable memory card.

  The operation will be described with reference to FIG. 1. A subject image (not shown) formed on the solid-state image sensor 2 by the lens 1 is converted into an electrical signal by the solid-state image sensor 2 and output. The electrical signal output from the solid-state imaging device 2 is subjected to predetermined processing in the analog signal processing circuit 3, converted into a digital signal in the AD converter 4, and supplied to the digital signal processing circuit 5. Further, predetermined processing is performed to generate image data. About the above point, it is the same as that of the past.

  The image data generated in the digital signal processing circuit 5 is subjected to a predetermined compression process in the data compression / decompression circuit 6. In the present embodiment, the first compression parameter is applied when the shooting time of the camera, that is, when the image accumulation time in the solid-state imaging device 2 is shorter than the first predetermined accumulation time. In addition, when the time is longer than the first predetermined accumulation time and shorter than the second predetermined accumulation time, the second parameter having a compression rate higher than that of the first compression parameter is set. Applied. Furthermore, when the time is longer than the second predetermined accumulation time, the third compression parameter having a higher compression rate is applied. As a result, even if the shooting time of the camera is a long time, the file capacity of the compressed image file is equal to or less than a predetermined capacity.

  The image file generated in the data compression / decompression circuit 6 is recorded on the memory card 9 via the memory card interface 8, and the above operation is controlled by the control unit 7 in accordance with an operation on an operation member (not shown). The point is the same as the conventional one. Further, the shooting time of the solid-state imaging device 2 is also controlled.

FIG. 2 is a flowchart illustrating an example of an operation procedure of the imaging apparatus according to the present embodiment.
In FIG. 2, this sequence is started when a shutter button (not shown) is depressed (step S201). After starting the sequence, in step S202, image storage of the solid-state imaging device 2 is started.

  Next, in step S203, it is determined whether a predetermined accumulation time has elapsed. If the result of this determination is that it has not elapsed, the system waits until a predetermined accumulation time has elapsed. On the other hand, as a result of the determination in step S203, if a predetermined accumulation time has elapsed, the process proceeds to step S204, and the solid-state imaging device 2 reads an image signal as an electrical signal.

  Next, in step S205, the image signal read by the solid-state imaging device 2 is subjected to predetermined image processing and converted into image data. In step S206, it is determined how many seconds the camera has been set to compress the image data in the data compression / decompression circuit 6.

  As a result of this determination, if the second setting is equal to or less than the first predetermined second, the process proceeds to step S207, and the first compression parameter with the lowest compression rate is set in the data compression / decompression circuit 6. If the second setting is longer than the first predetermined second and shorter than the second predetermined second as a result of the determination in step S206, the process proceeds to step S208, and the compression rate is higher than that of the first compression parameter. A high second compression parameter is set in the data compression / decompression circuit 6. Furthermore, if the second setting is longer than the second predetermined second as a result of the determination in step S206, a third compression parameter having a higher compression rate than the second compression parameter is set in the data compression / expansion circuit 6. (Step S209).

  Next, in step S210, compression processing is performed based on the set compression parameter. Next, in step S211, the compressed image file is recorded on the memory card 9. Then, this sequence ends (step S212).

  As described above, in the present embodiment, since an appropriate compression parameter is set according to the shooting time of the camera, an image file with an appropriate file capacity that does not depend on the shooting time can be recorded.

(Second Embodiment)
A second embodiment of the present invention will be described with reference to the drawings.
FIG. 3 is a block diagram illustrating a functional configuration example of the imaging apparatus according to the present embodiment. In FIG. 3, the same members as those in FIG. 1 are denoted by the same reference numerals, and the description of the overlapping configuration is omitted. 3 is different from FIG. 1 in that a temperature sensor 10 is provided.

  The operation will be described with reference to FIG. A subject image (not shown) formed on the solid-state image sensor 2 by the lens 1 is converted into an electrical signal by the solid-state image sensor 2 and output. The electrical signal output from the solid-state imaging device 2 is subjected to predetermined processing in the analog signal processing circuit 3, converted into a digital signal in the AD converter 4, and supplied to the digital signal processing circuit 5. Further, predetermined processing is performed to generate image data. The above points are the same as in the first embodiment.

  In the present embodiment, a temperature sensor 10 is connected to the control unit 7 and measures the temperature in the vicinity of the solid-state imaging device 2 at the time of shooting. The image data generated in the digital signal processing circuit 5 is subjected to a predetermined compression process in the data compression / decompression circuit 6.

  In the present embodiment, the first compression parameter is applied when the temperature in the vicinity of the solid-state imaging device 2 measured using the temperature sensor 10 is lower than the first predetermined temperature. In addition, when the temperature is higher than the first predetermined temperature and lower than the second predetermined temperature, the second parameter having a higher compression rate than the first compression parameter is applied. Further, when the temperature is higher than the second predetermined temperature, the third compression parameter having a higher compression rate is applied. As a result, the file capacity of the compressed image file does not depend on the temperature of the solid-state imaging device 2 at the time of photographing, and becomes a predetermined capacity or less.

  The image file generated in the data compression / decompression circuit 6 is recorded on the memory card 9 via the memory card interface 8. The point that the above operation is controlled by the control unit 7 in accordance with an operation on an operation member (not shown) is the same as in the first embodiment.

FIG. 4 is a flowchart illustrating an example of an operation procedure of the imaging apparatus according to the present embodiment. The processing in steps S401 to S405 in FIG. 4 is the same as the processing in steps S201 to S205 in FIG.
In step S406, in order to compress the image data in the data compression / decompression circuit 6, it is determined how many times the temperature in the vicinity of the solid-state imaging device 2 measured by the temperature sensor 10 has been measured.

  If the result of this determination is that the measured temperature is equal to or lower than the first predetermined temperature, processing proceeds to step S407, and the first compression parameter with the lowest compression rate is set in the data compression / expansion circuit 6. If the result of determination in step S406 is that the measured temperature is higher than the first predetermined temperature and lower than the second predetermined temperature, the process proceeds to step S408, where the compression rate is higher than the first compression parameter. 2 compression parameters are set in the data compression / decompression circuit 6. If the measured temperature is higher than the second predetermined temperature as a result of the determination in step S406, the process proceeds to step S409, and the third compression parameter having a higher compression ratio than the second compression parameter is compressed and decompressed. Set in circuit 6. Settings for setting these compression parameters in the data compression / decompression circuit 6 are performed by the control unit 7.

  In step S410, the data compression / decompression circuit 6 performs compression processing based on the set compression parameter. Next, in step S411, the compressed image file is recorded on the memory card 9. Then, this sequence ends (step S412).

  As described above, in this embodiment, the temperature sensor 10 is provided in the camera, and the control unit 7 sends an appropriate compression parameter to the data compression / decompression circuit 6 according to the temperature inside the apparatus measured by the temperature sensor 10. I set it. This makes it possible to record an image file with an appropriate file capacity that does not depend on the temperature at the time of shooting.

(Third embodiment)
A third embodiment of the present invention will be described with reference to the drawings.
Since the functional configuration of the imaging apparatus of the present embodiment is the same as the configuration shown in FIG. 3 of the second embodiment described above, description of each configuration is omitted.

  The operation will be described with reference to FIG. A subject image (not shown) formed on the solid-state image sensor 2 by the lens 1 is converted into an electrical signal by the solid-state image sensor 2 and output. The electrical signal output from the solid-state imaging device 2 is subjected to predetermined signal processing in the analog signal processing circuit 3, converted into a digital signal in the AD converter 4, and supplied to the digital signal processing circuit 5. Further, predetermined digital signal processing is performed to generate image data. About the above point, it is the same as that of 2nd Embodiment. The analog signal processing circuit 3, the AD converter 4 and the digital signal processing circuit 5 constitute a signal processing means, and the sensitivity of the imaging apparatus is determined by the set gain.

  The image data generated in the digital signal processing circuit 5 is subjected to a predetermined compression process in the data compression / decompression circuit 6. In the present embodiment, the compression parameter applied at this time is determined by the sensitivity setting, the shooting time, and the temperature in the vicinity of the solid-state imaging device 2.

Here, K1 is a coefficient representing noise generated at low sensitivity, short seconds, and low temperature of the camera, K2 is a coefficient representing noise that varies depending on the shooting time, and a coefficient representing noise that varies depending on the temperature of the solid-state imaging device 2. K3. In this case, the noise amount N1 at the time of low sensitivity can be obtained by the following equation (1).
N1 = K1 + K2 + K3 (1)

If the noise multiple that changes according to the sensitivity setting is An, the total noise amount N can be obtained by the following equation (2).
N = An × N1 (2)

  The compression parameter is determined according to the noise amount N. If N is lower than the first predetermined amount, the first compression parameter is applied. Further, when N is higher than the first predetermined amount and lower than the second predetermined amount, the second parameter having a higher compression ratio than the first compression parameter is applied. Furthermore, when the amount is higher than the second predetermined amount, a third compression parameter having a higher compression rate is applied. As a result, the file capacity of the compressed image file is equal to or less than a predetermined capacity regardless of the sensitivity setting of the camera, the shooting time, the temperature in the vicinity of the solid-state imaging device 2, and the like.

  The image file generated in the data compression / decompression circuit 6 is recorded on the memory card 9 via the memory card interface 8. The point that the above operation is controlled by the control unit 7 in accordance with an operation on an operation member (not shown) is the same as in the second embodiment.

FIG. 5 is a flowchart illustrating an example of an operation procedure of the imaging apparatus according to the present embodiment. The processes in steps S501 to S505 in FIG. 5 are the same as the processes in steps S201 to S205 in FIG.
Next, in step S506, it is determined how much noise N is present when the data compression / decompression circuit 6 performs compression processing on the image data.

  If the result of this determination is that the noise amount N is less than or equal to the first predetermined amount, processing proceeds to step S507, and the first compression parameter with the lowest compression rate is set in the data compression / decompression circuit 6. If the noise amount N is larger than the first predetermined amount and smaller than the second predetermined amount, the process proceeds to step S508, and the second compression parameter having a higher compression ratio than the first compression parameter is compressed and decompressed. Set in circuit 6. Further, when the noise amount N is larger than the second predetermined amount, the process proceeds to step S509, and a third compression parameter having a higher compression rate than the second compression parameter is set in the data compression / expansion circuit 6.

  Next, in step S510, compression processing is performed based on the set compression parameter. In step S511, the compressed image file is recorded on the memory card 9. Then, this sequence ends (step S512).

  As described above, according to the present embodiment, an appropriate compression parameter is set according to the sensitivity setting of the solid-state imaging device 2, the shooting time, and the temperature inside the apparatus measured by the temperature sensor 10. As a result, an image file having an appropriate file capacity can be recorded without depending on camera settings and environmental conditions.

(Other embodiments according to the present invention)
Each unit constituting the image pickup apparatus and each step of the control method of the image pickup apparatus in the embodiment of the present invention described above can be realized by operating a program stored in a RAM or ROM of a computer. This program and a computer-readable recording medium recording the program are included in the present invention.

  Further, the present invention can be implemented as, for example, a system, apparatus, method, program, or recording medium. Specifically, the present invention may be applied to a system including a plurality of devices. The present invention may be applied to an apparatus composed of a single device.

  In the present invention, a software program (in the embodiment, a program corresponding to the flowcharts shown in FIGS. 2, 4, and 5) that realizes the functions of the above-described embodiments is directly or remotely supplied to the system or apparatus. This includes the case where the system or the computer of the apparatus is also achieved by reading and executing the supplied program code.

  Accordingly, since the functions of the present invention are implemented by computer, the program code installed in the computer also implements the present invention. In other words, the present invention includes a computer program itself for realizing the functional processing of the present invention.

  In that case, as long as it has the function of a program, it may be in the form of object code, a program executed by an interpreter, script data supplied to the OS, or the like.

  Examples of the recording medium for supplying the program include a floppy (registered trademark) disk, a hard disk, an optical disk, and a magneto-optical disk. Further, there are MO, CD-ROM, CD-R, CD-RW, magnetic tape, nonvolatile memory card, ROM, DVD (DVD-ROM, DVD-R) and the like.

  As another program supply method, there is a method of connecting to a homepage on the Internet using a browser of a client computer. The computer program itself of the present invention or a compressed file including an automatic installation function can be downloaded from the homepage by downloading it to a recording medium such as a hard disk.

  It can also be realized by dividing the program code constituting the program of the present invention into a plurality of files and downloading each file from a different homepage. That is, a WWW server that allows a plurality of users to download a program file for realizing the functional processing of the present invention on a computer is also included in the present invention.

  As another method, the program of the present invention is encrypted, stored in a recording medium such as a CD-ROM, distributed to users, and encrypted from a homepage via the Internet to users who have cleared predetermined conditions. Download the key information to be solved. It is also possible to execute the encrypted program by using the key information and install the program on a computer.

  Further, the functions of the above-described embodiments are realized by the computer executing the read program. Furthermore, based on the instructions of the program, an OS or the like running on the computer performs part or all of the actual processing, and the functions of the above-described embodiments can be realized by the processing.

  As another method, the program read from the recording medium is first written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. Then, based on the instructions of the program, the CPU or the like provided in the function expansion board or function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are also realized by the processing.

It is a block diagram showing an example of functional composition of an imaging device of a 1st embodiment of the present invention. 3 is a flowchart illustrating an example of an operation procedure of the imaging apparatus according to the first embodiment of the present invention. It is a block diagram which shows the function structural example of the imaging device of the 2nd Embodiment of this invention. It is a flowchart which shows an example of the operation | movement procedure of the imaging device of the 2nd Embodiment of this invention. 10 is a flowchart illustrating an example of an operation procedure of the imaging apparatus according to the third embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lens 2 Solid-state image sensor 3 Analog signal processing circuit 4 AD converter 5 Digital signal processing circuit 6 Data compression / expansion circuit 7 Control part 8 Memory card interface 9 Memory card 10 Temperature sensor

Claims (14)

A signal processing unit having a variable gain setting when signal processing is performed on an image signal output from the image sensor to generate image data;
Compression means for compressing image data output from the signal processing means while changing a compression parameter according to an imaging condition;
An image pickup apparatus comprising: a storage unit that stores the compressed data output from the compression unit in a recording medium.   The imaging apparatus according to claim 1, wherein the compression unit changes a compression parameter according to an image accumulation time in the imaging element.   The imaging apparatus according to claim 2, wherein the compression unit changes a compression parameter so that a compression rate is increased according to a length of an image accumulation time in the imaging element. Having temperature measuring means for measuring the temperature inside the device,
The imaging apparatus according to claim 1, wherein the compression unit changes a compression parameter according to a temperature inside the apparatus measured by the temperature measurement unit.   The imaging apparatus according to claim 4, wherein the compression unit changes a compression parameter so that a compression rate increases as a temperature inside the apparatus measured by the temperature measurement unit increases. Having temperature measuring means for measuring the temperature inside the device,
The compression unit changes a compression parameter according to a gain set by the signal processing unit, an image accumulation time in the image sensor, and an internal temperature measured by the temperature measurement unit. The imaging device according to claim 1.   The compression means estimates the amount of noise included in the image data from the gain set by the signal processing means, the image accumulation time in the image sensor, and the temperature inside the apparatus measured by the temperature measurement means. The imaging apparatus according to claim 6, wherein a compression parameter is changed so that a compression rate is increased in accordance with an increase in the amount of noise. A signal processing step in which a gain setting is variable when generating image data by performing signal processing on an image signal output from the image sensor;
A compression step of compressing the image data generated in the signal processing step while changing a compression parameter according to an imaging condition;
And a storage step for storing the compressed data compressed in the compression step in a recording medium.   9. The method according to claim 8, wherein, in the compression step, a compression parameter is changed according to an image accumulation time in the image sensor.   The method for controlling an imaging apparatus according to claim 9, wherein, in the compression step, a compression parameter is changed so that a compression rate is increased in accordance with a length of an image accumulation time in the imaging element. It has a temperature measurement process that measures the temperature inside the device,
9. The method according to claim 8, wherein, in the compression step, a compression parameter is changed according to a temperature inside the device measured in the temperature measurement step.   12. The imaging apparatus according to claim 11, wherein, in the compression step, a compression parameter is changed so that a compression rate increases as the temperature inside the device measured in the temperature measurement step increases. Control method. It has a temperature measurement process that measures the temperature inside the device,
In the compression step, the compression parameter is changed according to the gain set in the signal processing step, the image accumulation time in the image sensor, and the temperature inside the apparatus measured in the temperature measurement step. The control method of the imaging device according to claim 8.   In the compression step, the amount of noise included in the image data is estimated from the gain set in the signal processing step, the image accumulation time in the image sensor, and the temperature inside the apparatus measured in the temperature measurement step. The method of controlling an imaging apparatus according to claim 13, wherein a compression parameter is changed so that a compression rate is increased in accordance with an increase in the amount of noise.

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