JP2010130088A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus capable of photographing images almost without a shutter time lag when a photographer presses a release button to start photographing. <P>SOLUTION: When a release button is pressed to start photographing, a CMOS sensor 20 is controlled by a TG (timing signal generator) 33, imaging by at least two times of exposure of different time is continuously performed first, and the exposure in the first imaging is evaluated in an exposure determination part 36. When it is determined that the exposure is sufficient, the image data of the exposure in the imaging for the time of the determination are acquired. When it is determined that the exposure in the first imaging is not sufficient, the exposure in the second imaging is evaluated in the exposure determination part 36, and when determining that the exposure is sufficient, exposure image data obtained when it is determined are defined as final exposure image data. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an imaging apparatus such as a digital camera.

In a conventional digital camera, when a release button (shutter button) is pressed (ON) during still image shooting, pre-exposure processing for measuring the brightness of the subject is performed, and imaging is performed with the exposure time determined by this pre-exposure processing. (See, for example, Patent Document 1).
JP 2003-279840 A

  As described above, in the conventional digital camera, since the actual imaging operation is started after the pre-exposure processing is completed, a shutter time lag of a predetermined time (for example, several tens of milliseconds) occurs. For this reason, even if the photographer presses the release button to start imaging, there may be a case where the shutter time lag is generated for the pre-exposure processing time, and thus imaging cannot be performed at the photographing timing intended by the photographer.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image pickup apparatus that can take an image with almost no shutter time lag when a photographer presses a release button to start shooting.

  In order to achieve the above object, the imaging apparatus according to claim 1 outputs an imaging unit that outputs captured image data, and control that controls the imaging unit to sequentially perform imaging with a plurality of set exposure times. And an exposure evaluation unit that evaluates the exposure amount of the image data acquired by the imaging unit. When shooting is started, the control unit first continuously performs imaging by at least two exposures, When the first image data is acquired by imaging, the first image data is evaluated by the exposure evaluation means in parallel with the second imaging, and when it is determined that the exposure amount is sufficient, If the image data of the first image data is the final image data, the subsequent processing of the image data output by the second imaging is stopped, and it is determined that the exposure amount of the first image data is not sufficient. Imaging If the second image data is acquired, the second image data is evaluated by the exposure evaluation means in parallel with the third imaging, and if it is determined that the exposure amount is sufficient, the image at the time of this determination When the data is the final exposure image data and the subsequent processing of the image data output by the third imaging is stopped and it is determined that the exposure amount of the second image data is not sufficient, the exposure evaluation Until the exposure amount is judged to be sufficient by the means, the exposure time by the first imaging is the shortest, and the imaging is repeatedly performed so as to become longer for each subsequent imaging.

  The imaging apparatus according to claim 2 includes an imaging unit that outputs captured image data, a control unit that controls the imaging unit to sequentially perform imaging with a plurality of set exposure times, and the imaging unit. An exposure evaluation unit that evaluates the exposure amount of the acquired image data and a composite exposure image data by sequentially synthesizing the image data output from the imaging unit when imaging is sequentially performed with the set exposure time. An image data synthesizing unit, and when the imaging is started, the control unit first continuously performs imaging by at least two exposures, and when the first imaging acquires the first image data, the second imaging In parallel with this, the first image data is evaluated by the exposure evaluation means, and when it is determined that the exposure amount is sufficient, the image data at the time of determination is set as final image data, and the second image data When the subsequent processing of the image data output by the image is stopped and it is determined that the exposure amount of the first image data is not sufficient, the first image data and the second image obtained by the second imaging First synthesized image data obtained by synthesizing the data by the image data synthesizing unit is acquired, and the first synthesized image data is evaluated by the exposure evaluating unit in parallel with the third imaging, and the exposure amount is sufficient. If it is determined that there is image data, the image data at the time of this determination is used as final exposure image data, the subsequent processing of the image data output by the third imaging is stopped, and the exposure amount of the first composite image data Is obtained, the second synthesized image data obtained by synthesizing the first synthesized image data and the third image data obtained by the third imaging by the image data synthesizing unit is obtained. In parallel with imaging When the composite image data 2 is evaluated by the exposure evaluation means and it is determined that the exposure amount is sufficient, the image data at the time of the determination is set as final image data, and the image data output by the fourth imaging When the subsequent processing is stopped and it is determined that the exposure amount of the second composite image data is not sufficient, the plurality of set exposure times until the exposure evaluation unit determines that the exposure amount is sufficient It is characterized in that imaging is repeatedly performed based on the above.

  The imaging apparatus according to claim 3, wherein the plurality of set exposure times are set such that an exposure time by the first imaging is shortest and becomes longer for each subsequent imaging.

  The imaging apparatus according to claim 4 starts the first and second imaging based on a signal from the control means without obtaining an optimum exposure amount when an instruction to start imaging is given by an operation by an operator. It is characterized by that.

  The imaging apparatus according to claim 5, wherein the exposure amount is when the number of pixels that the exposure evaluation unit determines to be crushed in black on the low luminance side is less than a predetermined ratio with respect to all pixel data to be determined. It is characterized by determining that it is sufficient.

  The imaging apparatus according to claim 6, wherein when the exposure evaluation unit determines that the exposure amount is not sufficient, the pixel that is crushed in black is specified, and the specific pixel is determined by image data acquired after the determined image data. When the number of reductions or the reduction rate of pixels in which blackout is eliminated or improved is smaller than a predetermined value, it is determined that the exposure amount is sufficient regardless of the predetermined rate. It is characterized by that.

  The imaging apparatus according to claim 7, wherein the imaging unit is a CMOS sensor having a rolling shutter function, and an imaging operation by the imaging unit and an exposure evaluation operation by the exposure evaluation unit are performed in parallel using the rolling shutter function. It is characterized by that.

  The imaging apparatus according to claim 8, wherein the first exposure time during the first imaging and the second exposure time during the second imaging are set by a dynamic range and a transfer frame rate of the CMOS sensor. It is characterized by.

  According to the imaging apparatus of the first and second aspects, it is not necessary to perform the pre-exposure processing for measuring the luminance of the subject first at the start of photographing as in the prior art, and there is almost no shutter time lag. It becomes possible to take an image at a shooting timing intended by the person.

  In the imaging apparatus according to claim 3, the plurality of set exposure times are set such that the exposure time by the first imaging is the shortest and becomes longer for each subsequent imaging. Thus, a plurality of exposures can be performed continuously.

  According to the imaging device of the fourth aspect, when the start of shooting is instructed by an operation by the operator, the first and second imaging are started based on a signal from the control means without obtaining the optimum exposure amount. By doing so, imaging can be performed with almost no shutter time lag.

  According to the imaging apparatus of the fifth aspect, it is possible to easily determine whether or not the exposure amount is sufficient based on a preset threshold value.

  According to the imaging device of the sixth aspect, for example, when the low luminance of the image is already dark, it can be determined that the exposure amount is sufficient without determining that the exposure is insufficient.

  According to the image pickup apparatus of the seventh aspect, by using a CMOS sensor having a rolling shutter function as the image pickup means, it is possible to easily pick up images sequentially at a plurality of different exposure times using the rolling shutter function.

  According to the imaging apparatus of the eighth aspect, the first exposure time during the first imaging and the second exposure time during the second imaging can be set by the dynamic range and transfer frame rate of the CMOS sensor. Therefore, in the case of a CMOS sensor with a faster transfer frame rate, this time (first and second exposure times) can be set shorter.

Hereinafter, the present invention will be described based on the illustrated embodiments.
<Embodiment 1>
FIG. 1A is a front view showing a digital still camera (hereinafter referred to as “digital camera”) as an example of an imaging apparatus according to Embodiment 1 of the present invention, and FIG. 1 (c) is a rear view thereof, and FIG. 2 is a block diagram showing an outline of a system configuration in the digital camera shown in FIGS. 1 (a), (b), and (c).

(Appearance structure of digital camera)
As shown in FIGS. 1A, 1B, and 1C, a release button (shutter button) 2, a power button 3, a shooting / playback switching dial 4 are provided on the upper surface side of the digital camera 1 according to the present embodiment. In the front (front) side of the digital camera 1, a lens barrel unit 6 having a photographing lens system 5, a strobe light emitting unit (flash) 7, and an optical viewfinder 8 are provided.

  On the back side of the digital camera 1, there are a liquid crystal monitor (LCD) 9, an eyepiece 8 a of the optical viewfinder 8, a wide-angle zoom (W) switch 10, a telephoto zoom (T) switch 11, and a menu (MENU) button 12. , A confirmation button (OK button) 13 and the like are provided. Further, a memory card storage unit 15 for storing a memory card 14 (see FIG. 2) for storing captured image data is provided inside the side surface of the digital camera 1.

(Digital camera system configuration)
As shown in FIG. 2, the digital camera 1 is output from a CMOS sensor 20 and a CMOS sensor 20 as image pickup elements on which a subject image incident through the taking lens system 5 of the lens barrel unit 6 is formed on the light receiving surface. A signal processing unit 21 for processing electrical signals (digital RGB image data), an SDRAM 22 for temporarily storing image data, a plurality of exposure times for the light receiving unit 30 of the CMOS sensor 20 in a dynamic range expansion mode to be described later, and a control program And a motor driver 24 that drives the lens barrel unit 6.

  The lens barrel unit 6 includes a photographic lens system 5 having a zoom lens, a focus lens, and the like, and a mechanical shutter unit 25. The drive units of the photographic lens system 5 and the mechanical shutter unit 25 are driven by a motor driver 24. . The motor driver 24 is driven and controlled by a drive signal from a control unit (CPU) 26 of the signal processing unit 21.

  The CMOS sensor 20 includes a light receiving unit 30 in which unit pixels (hereinafter referred to as “pixels”) including photoelectric conversion elements that photoelectrically convert incident visible light into a charge amount corresponding to the amount of light are two-dimensionally arranged in a matrix. , An amplification unit (AMP) 31, an A / D conversion unit 32, a TG (timing signal generation unit) 33 that drives each pixel of the light receiving unit 30, and the like. As shown in FIG. 3, the CMOS sensor 20 (light receiving unit 30) starts accumulation of electric charge from that point in time for a pixel that outputs a signal, so that the charge accumulation start timing is shifted for each pixel row. This is an accumulation control method called a shutter, and images are sequentially taken at a plurality of different exposure times as described later using this rolling shutter function.

  An RGB primary color filter (not shown) as a color separation filter is disposed on a plurality of pixels constituting the light receiving unit 30 of the CMOS sensor 20, and an electrical signal (analog RGB image data) corresponding to the RGB three primary colors is amplified. Amplified by the unit 31 and converted into a digital signal (hereinafter referred to as “RAW-RGB data”) by the A / D converter 32.

  The signal processing unit 21 includes a camera interface (hereinafter referred to as “camera I / F”) 34 that captures RAW-RGB data output from the A / D conversion unit 32 of the CMOS sensor 20, and a memory controller 35 that controls the SDRAM 23. An exposure determination unit 36 that determines whether or not the exposure at the time of imaging is appropriate based on the RAW-RGB data, and converts the RAW-RGB data into YUV format image data that can be displayed and recorded, and further white An image data processing unit 37 for adjusting the balance, a resizing processing unit 38 for changing the image size in accordance with the size of the image data to be displayed and recorded, a display output control unit 39 for controlling the display output of the image data, A data compression unit 40 for recording image data by JPEG formation and the like, and writing the image data to the memory card 14 Or based on a control program stored in the ROM 23 based on operation input information from a media interface (hereinafter referred to as “media I / F”) 41 that reads image data written in the memory card 14 and an operation unit 42. The control unit (CPU) 26 that performs system control and the like of the entire digital camera 1 is provided.

  In addition, the control unit 26 outputs a horizontal synchronization signal (HD) and a vertical synchronization signal (VD) to the TG 33 of the CMOS sensor 20, and a plurality of light-receiving units 30 constituting the CMOS sensor 20 are configured in accordance with these synchronization signals. Drive the pixels.

  The operation unit 43 includes a release button 2, a power button 3, a photographing / playback switching dial 4, and a wide-angle zoom provided on the external surface of the digital camera 1 (see FIGS. 1A, 1B, and 1C). The switch 10, the telephoto zoom switch 11, the menu button 12, the confirm button 13, and the like, and a predetermined operation instruction signal is input to the control unit 26 by the photographer's operation.

  The SDRAM 22 stores the RAW-RGB data, image data such as JPEG formation compressed by the data compression unit 40, and the like.

(Still Image Shooting Operation in Embodiment 1)
When the photographer presses the menu (MENU) button 12 (see FIG. 1C), a shooting setting screen (not shown) is displayed on the liquid crystal monitor (LCD) 9. From this display screen, “still image shooting” is displayed. By selecting the “mode” item, the control unit 26 controls to switch to the still image shooting mode. At this time, a photographed image (moving image) is displayed on the liquid crystal monitor 9 by the monitoring operation, and the photographer can take a picture while visually recognizing the photographed image displayed on the liquid crystal monitor 9. In this monitoring operation, AE (automatic exposure) processing and AWB (auto white balance) processing are continuously performed.

  Then, during the monitoring operation, the photographer points the photographing lens system 5 toward the subject and presses the release button 2 (half-press (hereinafter referred to as “release 1”) to full-press (hereinafter referred to as “release 2”)). By starting still image shooting, a control signal is output from the control unit 26 to the TG 33, and the CMOS sensor 20 (light receiving unit 30) is driven based on a plurality of preset exposure times read from the ROM 23. It should be noted that RAW-RGB data is output from the CMOS sensor 20 to the camera I / F 34 by the release 1 to the release 2 of the release button 2, and the control unit 26 evaluates AF (automatic focus) calculated from the RAW-RGB data. Based on the value, for example, an AF (automatic focus) operation of a contrast evaluation method called so-called hill-climbing AF is executed, and the focus lens of the photographic lens system 5 is moved by the drive command to the motor driver 24 to focus. Let

  For example, as shown in FIG. 4, the plurality of exposure times in the present embodiment are four times exposure (first exposure a1, second exposure a2, and third exposure) by the rolling shutter function of the CMOS sensor 20 (light receiving unit 30). a3, fourth exposure a4) time is set, and imaging is performed a maximum of four times corresponding to the four exposure times (first exposure a1, second exposure a2, third exposure a3, fourth exposure a4) (First imaging, second imaging, third imaging, fourth imaging) can be performed continuously. In the present embodiment, the time of the first exposure a1 is 1/960 (= 1 / (60 × 16)) seconds, the time of the second exposure a2 is 1/60 seconds, and the time of the third exposure a3 is 1/30 ( = 2/60) seconds, and the time of the fourth exposure a4 is preset to 4/15 (= 16/60) seconds. That is, the time of the first exposure a1 is set to be the shortest and the exposure time is sequentially increased.

  The time of the second exposure a2 in the second imaging is set to a reference time calculated from the transfer frame rate of the CMOS sensor 20. In this embodiment, since the transfer frame rate is 60 fps, the time of the second exposure a2 is set to 1/60 seconds.

  Further, the first exposure a1 in the first imaging and the second exposure a2 in the second imaging are continuous exposures by the rolling shutter function of the CMOS sensor 20 (light receiving unit 30), and the time lag between the first imaging and the second imaging. Is small enough to be ignored. The time of the first exposure a1 in the first imaging and the time of the second exposure a2 in the second imaging can be calculated based on the dynamic range and transfer frame rate of the CMOS sensor 20 as described above.

  Next, the still image shooting operation in the present embodiment will be described with reference to the flowchart shown in FIG.

  In the present embodiment, the first exposure a1 by the first imaging and the second imaging are first performed by the rolling shutter function of the CMOS sensor 20 (light receiving unit 30) by the start of shooting by the release 1 from the release 1 of the release button 2. The second exposure a2 is continuously performed (Step S1, Step S2).

  Then, the exposure determination unit 36 applies the first RAW-RGB data (hereinafter referred to as “first exposure image data”) captured from the CMOS sensor 20 to the camera I / F 34 of the signal processing unit 21 by the first imaging. The appropriate exposure determination process is performed to determine whether or not the exposure is sufficient (sufficient exposure amount) (step S3).

  Here, the first proper exposure determination process by the exposure determination unit 36 in step S3 will be described with reference to the flowchart shown in FIG.

  First, the first exposure image data is taken from the first exposure (step S21), and a luminance histogram is generated from the first exposure image data (step S22). Then, based on the luminance histogram generated in step S22, the ratio of the number of pixels crushed in black on the low luminance side to the total number of pixels is determined (step S23). Note that the blackened pixel on the low luminance side in step S23 is a pixel in which the low luminance side of the image is blackened due to insufficient exposure time, or a pixel in which the low luminance side of the image is blackened in the dark state. Is the case.

  If it is determined that the ratio of the number of blackened pixels on the low luminance side to the total number of pixels is, for example, less than 0.1% (step S24; YES), the first exposure is determined to be a sufficient exposure amount. (Step S25). That is, there is a possibility that the image data information on the low luminance side can be acquired by extending the exposure time, but the ratio of the number of blackened pixels on the low luminance side to the total number of pixels is, for example, less than 0.1% Is a sufficiently small value with respect to the total number of pixels, and is determined to be a sufficient exposure amount.

  On the other hand, if it is determined that the ratio of the number of black pixels on the low luminance side to the total number of pixels is, for example, 0.1% or more (step S24; NO), the low luminance side is crushed on the low luminance side. It is determined that the ratio of the number of pixels is not a small value with respect to the total number of pixels and the first exposure is underexposed (step S26).

  In the first appropriate exposure determination process in step S3 described above, when it is determined that the first exposure is sufficient exposure (sufficient exposure amount) (step S4; YES), the second imaging is performed in step S2. Subsequent processing on the RAW-RGB data (hereinafter referred to as “second exposure image data”) captured from the CMOS sensor 20 to the camera I / F 34 of the signal processing unit 21 is stopped (step S5), and the first exposure image is displayed. The data is output to the image data processing unit 37 (step S6). The first exposure image data and the second exposure image data are stored in the SDRAM 22 via the memory controller 35.

  The image data processing unit 37 converts the first exposure image data read from the SDRAM 22 through the memory controller 35 into YUV format image data, and further sets the white balance, and then the resize processing unit 38 sets the number of recorded pixels. The data is converted into a corresponding size, and the data compression unit 40 compresses the image data in JPEG format or the like. The compressed image data such as JPEG format is written back to the SDRAM 23, read out from the SDRAM 23 via the memory controller 35, and recorded on the memory card 14 via the media I / F 41.

  In the first appropriate exposure determination process in step S3, when it is determined that the first exposure is not a sufficient exposure amount (insufficient exposure) (step S4; NO), the second exposure a2 in the second imaging is performed. The third exposure a3 (see FIG. 4) by the third imaging is performed (step S7). In the present embodiment, the time of the third exposure a3 by the third imaging is twice (1/30 seconds) the time of the second exposure a2 in the second imaging as described above.

  When using the rolling shutter function of the CMOS sensor 20 as in the present embodiment, it is desirable to set the exposure time after the third imaging by a multiple of the transfer frame rate of the CMOS sensor 20 as described above. By setting the exposure time after the third imaging to a multiple of the transfer frame rate, the exposure in each imaging can be regarded as continuous exposure.

  Then, a second sufficient exposure determination process is performed on the second exposure image data by the exposure determination unit 36 to determine whether the exposure is sufficient (a sufficient exposure amount) (step S8).

  Here, the second sufficient exposure determination process by the exposure determination unit 36 in step S8 will be described with reference to the flowchart shown in FIG.

  First, the second exposure image data is fetched from the second exposure (step S31), and a luminance histogram is generated from the second exposure image data (step S32). Then, based on the luminance histogram generated in step S32, the ratio of the number of pixels crushed in black on the low luminance side to the total number of pixels is determined (step S33). Note that the blackened pixel on the low luminance side in step S33 is a pixel in which the low luminance side of the image is blackened due to insufficient exposure time, or a pixel in which the low luminance side of the image is blackened in the dark state. Is the case.

  Then, when it is determined that the ratio of the number of blackish pixels on the low luminance side to the total number of pixels is less than 0.1%, for example (step S34; YES), the second exposure is determined to be a sufficient exposure amount. (Step S35). That is, there is a possibility that the image data information on the low luminance side can be acquired by extending the exposure time, but the ratio of the number of blackened pixels on the low luminance side to the total number of pixels is, for example, less than 0.1% Is a sufficiently small value with respect to the total number of pixels, and is determined to be sufficient exposure.

  On the other hand, if it is determined that the ratio of the number of blackish pixels on the low luminance side to the total number of pixels is, for example, 0.1% or more (step S34; NO), the previous step in step S24 of FIG. A change in the number of blackened pixels on the low luminance side from the determination time is determined (step S36). If it is determined in step S36 that the number of blackened pixels on the low luminance side has changed since the previous determination (step S24 in FIG. 6) (for example, if the total number of pixels is 10 million pixels, When the number of blackened pixels on the low-brightness side is about 100,000 pixels at the time of this determination, and the number of blackened pixels on the low-brightness side is reduced to about 50,000 pixels at the time of this determination) (Step S36; NO), there is a possibility that new image data information on the low luminance side can be acquired by extending the exposure time, and it is determined that the second exposure is underexposed (step S37).

  If it is determined in step S36 that the number of blackened pixels on the low luminance side has hardly changed from the previous determination (step S24 in FIG. 6) (step S36; YES), the exposure time is extended. Nevertheless, the fact that the number of blackened pixels on the low luminance side has hardly changed is presumed that there is a high possibility that the low luminance side of the image is already dark, and the second exposure has a sufficient exposure amount. Determination is made (step S35).

  In the second sufficient exposure determination process in step S8 described above, if it is determined that the second exposure is sufficient exposure (sufficient exposure amount) (step S9; YES), the third imaging is performed in step S7. Subsequent processing for the RAW-RGB data (hereinafter referred to as “third exposure image data”) captured from the CMOS sensor 20 to the camera I / F 34 of the signal processing unit 21 is stopped (step S10), and the second exposure image is obtained. Data is output to the image data processing unit 37 (step S11). The third exposure image data and the second exposure image data are stored in the SDRAM 22 via the memory controller 35.

  The image data processing unit 37 converts the second exposure image data read from the SDRAM 22 via the memory controller 35 into YUV format image data, and further sets the white balance, and then the resize processing unit 38 sets the number of recorded pixels. The data is converted into a corresponding size, and the data compression unit 40 compresses the image data in JPEG format or the like. The compressed image data such as JPEG format is written back to the SDRAM 23, read out from the SDRAM 23 via the memory controller 35, and recorded on the memory card 14 via the media I / F 41.

  In the second sufficient exposure determination process in step S8, when it is determined that the second exposure is not a sufficient exposure amount (insufficient exposure) (step S9; NO), the third exposure a3 in the third imaging is performed. The fourth exposure a4 (see FIG. 4) by the fourth imaging is performed (step S12). In the present embodiment, the time of the fourth exposure a4 by the fourth imaging is four times (4/15 (= 16/60) seconds) the time of the second exposure a2 in the second imaging as described above.

  Then, a third sufficient exposure determination process is performed on the third exposure image data by the exposure determination unit 36 to determine whether the exposure is sufficient (a sufficient exposure amount) (step S13).

  Here, the third sufficient exposure determination process by the exposure determination unit 36 in step S13 will be described with reference to the flowchart shown in FIG.

  First, the third exposure image data is taken from the third exposure (step S41), and a luminance histogram is generated from the third exposure image data (step S42). Then, based on the luminance histogram generated in step S42, the ratio of the number of pixels crushed in black on the low luminance side to the total number of pixels is determined (step S43). Note that the blackened pixel on the low luminance side in step S43 is a pixel in which the low luminance side of the image is blackened due to insufficient exposure time, or a pixel in which the low luminance side of the image is blackened in the dark state. Is the case.

  If it is determined that the ratio of the number of pixels on the low luminance side that is crushed in black to the total number of pixels is, for example, less than 0.1% (step S44; YES), the third exposure is determined to be a sufficient exposure amount. (Step S45). That is, there is a possibility that the image data information on the low luminance side can be acquired by extending the exposure time, but the ratio of the number of blackened pixels on the low luminance side to the total number of pixels is, for example, less than 0.1% Is a sufficiently small value with respect to the total number of pixels, and is determined to be sufficient exposure.

  On the other hand, if it is determined that the ratio of the number of blackish pixels on the low luminance side to the total number of pixels is, for example, 0.1% or more (step S44; NO), the previous step in step S34 in FIG. A change in the number of blackened pixels on the low luminance side from the determination time is determined (step S46). If it is determined in step S46 that the number of blackened pixels on the low luminance side has changed since the previous determination (step S34 in FIG. 7) (for example, if the total number of pixels is 10 million pixels, When the number of blackened pixels on the low-brightness side is about 50,000 pixels at the time of this determination, and the number of blackened pixels on the low-brightness side is reduced to about 10,000 pixels at the time of this determination) (Step S46; NO), there is a possibility that new image data information on the low luminance side can be acquired by extending the exposure time, and it is determined that the third exposure is underexposed (step S47).

  If it is determined in step S46 that the number of blackened pixels on the low luminance side has hardly changed from the previous determination (step S34 in FIG. 7) (step S46; YES), the exposure time is extended. Nevertheless, the fact that the number of pixels that are crushed in black on the low luminance side has hardly changed is presumed that there is a high possibility that the low luminance side of the image is already dark, and the third exposure has a sufficient exposure amount. Determination is made (step S45).

  In the third sufficient exposure determination process in step S13 described above, when it is determined that the third exposure is sufficient exposure (sufficient exposure amount) (step S14; YES), the fourth imaging is performed in step S12. The subsequent processing on the RAW-RGB data (hereinafter referred to as “fourth exposure image data”) captured from the CMOS sensor 20 to the camera I / F 34 of the signal processing unit 21 is stopped (step S15), and the third exposure is performed. The image data is output to the image data processing unit 37 (step S16). The fourth exposure image data and the third exposure image data are stored in the SDRAM 22 via the memory controller 35.

  The image data processing unit 37 converts the third exposure image data read from the SDRAM 22 through the memory controller 35 into YUV format image data, and further sets the white balance, and then the resize processing unit 38 sets the number of recorded pixels. The data is converted into a corresponding size, and the data compression unit 40 compresses the image data in JPEG format or the like. The compressed image data such as JPEG format is written back to the SDRAM 23, read out from the SDRAM 23 via the memory controller 35, and recorded on the memory card 14 via the media I / F 41.

  If it is determined in the third sufficient exposure determination process in step S13 that the third exposure is not a sufficient exposure amount (insufficient exposure) (step S14; NO), the fourth exposure image read from the SDRAM 22 is used. The data is output to the image data processing unit 37 (step S17). The fourth exposure image data is stored in the SDRAM 22 via the memory controller 35.

  The image data processing unit 37 converts the fourth exposure image data read from the SDRAM 22 through the memory controller 35 into YUV format image data, and further sets the white balance, and then the resize processing unit 38 sets the number of recorded pixels. The data is converted into a corresponding size, and the data compression unit 40 compresses the image data in JPEG format or the like. The compressed image data such as JPEG format is written back to the SDRAM 23, read out from the SDRAM 23 via the memory controller 35, and recorded on the memory card 14 via the media I / F 41.

  In step S17, when it is determined that the third exposure is not a sufficient exposure amount (underexposure), the fourth exposure image data is output to the image data processing unit 37, but the third exposure is performed. When it is determined that the exposure amount is not sufficient (underexposure) (step S14; NO), the third exposure is processed as underexposure (ie, exposure NG) without outputting the fourth exposure image data (step NG) (step S14). S17) The image data may not be output (recorded).

  As described above, in the imaging apparatus of the first embodiment, during the monitoring operation, the above-described imaging operation by the multiple exposure is performed simultaneously with the imaging start operation by the release 1 to the release 2 of the release button 2 as in the related art. When the release button 2 starts shooting with the release 1 to the release 2, there is no need to perform pre-exposure processing for measuring the luminance of the subject first.

  That is, in the conventional case shown in FIG. 9A, the pre-exposure processing is first performed at the start of shooting with the release button from the release 1 to the release 2, and monitoring in which AE (automatic exposure) processing is continuously performed. During the operation, AE (automatic exposure) control is locked by release 1 of the release button at time t1, and AF (automatic focusing) processing is performed. Then, at time t2, the pre-exposure process for measuring the luminance of the subject is first performed by the release button 2 of the release button, and then the exposure is performed at the time determined by the pre-exposure process. The time required for this pre-exposure processing is, for example, about 33 msec.

  On the other hand, in the case of the first embodiment shown in FIG. 9B, during the monitoring operation in which the AE (automatic exposure) process is continuously performed, the release button 1 of the release button releases AE (automatic) at time t1. (Exposure) control is locked, and AF (autofocus) processing is performed. At time t2, photographing is started by release 2 of the release button, and first exposure, second exposure, and third exposure are sequentially performed based on the processing shown in the flowchart of FIG. 5 without performing pre-exposure processing as in the prior art. Perform exposure.

  As described above, according to the present embodiment, when taking a still image in the normal shooting mode, it is not necessary to perform the pre-exposure processing for measuring the luminance of the subject at the start of shooting as in the prior art, and the shutter time lag is almost generated. Therefore, it is possible to take an image at the photographing timing intended by the photographer.

  In the present embodiment, since the rolling shutter function of the CMOS sensor 20 is used, the time lag between the imagings with different exposure amounts can be made substantially zero, and the imaging time can be further shortened.

  In the conventional case shown in FIG. 9A, the pre-exposure processing is performed at the start of photographing by the release button 2 of the release button. However, the conventional pre-exposure processing is performed by the release button 1 of the release button. Even in this case, since the start of shooting by the release button release 2 is not executed until this pre-exposure processing is completed, it may not be possible to perform shooting without a shutter time lag at the shooting timing intended by the photographer.

<Embodiment 2>
FIG. 10 is a block diagram illustrating an outline of a system configuration in the digital camera according to the present embodiment. As shown in FIG. 10, in the present embodiment, an image data composition unit 43 that accumulates and composes image data obtained by a plurality of exposures having different exposure times in the system configuration of the first embodiment shown in FIG. Is further provided. Other configurations are the same as those of the first embodiment shown in FIGS. 1 to 4, and redundant description is omitted.

(Still Image Shooting Operation in Embodiment 2)
As in the first embodiment, when the photographer presses the menu (MENU) button 12 (see FIG. 1C), a shooting setting screen (not shown) is displayed on the liquid crystal monitor (LCD) 9. By selecting the “still image shooting mode” item from the display screen, the control unit 26 controls to switch to the still image shooting mode. At this time, a photographed image (moving image) is displayed on the liquid crystal monitor 9 by the monitoring operation, and the photographer can take a picture while visually recognizing the photographed image displayed on the liquid crystal monitor 9. In this monitoring operation, AE (automatic exposure) processing and AWB (auto white balance) processing are continuously performed.

  Also in the present embodiment, the plurality of exposure times are the same as in the first embodiment, for example, as shown in FIG. 4, four exposures (first exposure a 1, 1) by the rolling shutter function of the CMOS sensor 20 (light receiving unit 30). The second exposure a2, the third exposure a3, the fourth exposure a4) are set, and the four exposure times (first exposure a1, second exposure a2, third exposure a3, fourth exposure a4) are set. Correspondingly, up to four times of imaging (first imaging, second imaging, third imaging, and fourth imaging) can be performed continuously. In the present embodiment, the time of the first exposure a1 is 1/960 (= 1 / (60 × 16)) seconds, the time of the second exposure a2 is 1/60 seconds, and the time of the third exposure a3 is 1/30 ( = 2/60) seconds, and the time of the fourth exposure a4 is preset to 4/15 (= 16/60) seconds. That is, the time of the first exposure a1 is set to be the shortest and the exposure time is sequentially increased.

  The time of the second exposure a2 in the second imaging is set to a reference time calculated from the transfer frame rate of the CMOS sensor 20. In this embodiment, since the transfer frame rate is 60 fps, the time of the second exposure a2 is set to 1/60 seconds.

  Further, when the dynamic range of the CMOS sensor 20 of the present embodiment is, for example, 6 EV, the time difference between the long and short exposure times can be allowed up to 2 6 (= 64 times). In order to ensure the continuity of the brightness of the images to be combined, an overlapping portion is provided as an overlapping portion of the dynamic range of each image. In the present embodiment, the exposure time difference is 4EV (2 4 (= 16 times)) with 2EV as an overlapping portion. Accordingly, the time of the first exposure a1 in the first imaging is set to 1/960 seconds (1/16 of the time of the second exposure a2 in the second imaging) as described above. Further, the first exposure a1 in the first imaging and the second exposure a2 in the second imaging are continuous exposures by the rolling shutter function of the CMOS sensor 20 (light receiving unit 30), and the time lag between the first imaging and the second imaging. Is small enough to be ignored.

  The time of the first exposure a1 in the first imaging and the time of the second exposure a2 in the second imaging can be calculated based on the dynamic range and transfer frame rate of the CMOS sensor 20 as described above. Therefore, in the case of a CMOS sensor with a faster transfer frame rate, this time can be set shorter.

  Next, the still image shooting operation in the present embodiment will be described with reference to the flowchart shown in FIG.

  In the present embodiment, the first exposure a1 by the first imaging and the second imaging are first performed by the rolling shutter function of the CMOS sensor 20 (light receiving unit 30) by the start of shooting by the release 1 from the release 1 of the release button 2. The second exposure a2 is continuously performed (Step S51, Step S52).

  Then, the first appropriate exposure determination process is performed by the exposure determination unit 36 on the first exposure image data captured from the CMOS sensor 20 to the camera I / F 34 of the signal processing unit 21 by the first imaging, and sufficient exposure ( It is determined whether or not the exposure amount is sufficient (step S53). Note that the first appropriate exposure determination processing by the exposure determination unit 36 in step S53 is the same as the flowchart shown in FIG. 6 in the first embodiment.

  In the first appropriate exposure determination process in step S53, if it is determined that the first exposure is sufficient exposure (sufficient exposure amount) (step S54; YES), the CMOS is obtained by the second imaging in step S52. Subsequent processing for the second exposure image data captured from the sensor 20 to the camera I / F 34 of the signal processing unit 21 is stopped (step S55), and the first exposure image data is output to the image data processing unit 37 (step S55). S56). The first exposure image data and the second exposure image data are stored in the SDRAM 22 via the memory controller 35.

  The image data processing unit 37 converts the first exposure image data read from the SDRAM 22 through the memory controller 35 into YUV format image data, and further sets the white balance, and then the resize processing unit 38 sets the number of recorded pixels. The data is converted into a corresponding size, and the data compression unit 40 compresses the image data in JPEG format or the like. The compressed image data such as JPEG format is written back to the SDRAM 23, read out from the SDRAM 23 via the memory controller 35, and recorded on the memory card 14 via the media I / F 41.

  In the first appropriate exposure determination process in step S53, when it is determined that the first exposure is not a sufficient exposure amount (insufficient exposure) (step S54; NO), the second exposure a2 in the second imaging is performed. The third exposure a3 (see FIG. 4) by the third imaging is performed (step S57). In the present embodiment, the time of the third exposure a3 by the third imaging is twice (1/30 seconds) the time of the second exposure a2 in the second imaging as described above.

  As described in the first embodiment, by setting the exposure time after the third imaging to a multiple of the transfer frame rate, the exposure in each imaging can be regarded as continuous exposure. Thereby, when the image data synthesizing unit 43 to be described later adds and synthesizes the image data, it is possible to prevent the edge portion at the time of subject blurring in the final output image from being doubled.

  Then, the first exposure image data and the second exposure image data read from the SDRAM 23 via the memory controller 35 are cumulatively added and synthesized by the image data synthesis unit 43 to generate first synthesized exposure image data (step). S58). Then, a second sufficient exposure determination process is performed on the second exposure image data by the exposure determination unit 36 to determine whether the exposure is sufficient (a sufficient exposure amount) (step S59).

  Here, the second sufficient exposure determination process by the exposure determination unit 36 in step S59 will be described with reference to the flowchart shown in FIG.

  First, the first composite exposure image data generated in step S58 of FIG. 11 is captured (step S71), and a luminance histogram is generated from the first composite exposure image data (step S72). Then, based on the luminance histogram generated in step S72, the ratio of the number of blackened pixels on the low luminance side to the total number of pixels is determined (step S73). Note that the blackened pixel on the low luminance side in step S73 is a pixel that is blackened on the low luminance side of the image due to insufficient exposure time, or a pixel that is blackened on the low luminance side of the image in the dark state. Is the case.

  If it is determined that the ratio of the number of pixels on the low-luminance side with respect to the total number of pixels is less than 0.1%, for example (step S74; YES), the first combined exposure has a sufficient exposure amount. Determination is made (step S75). That is, there is a possibility that the image data information on the low luminance side can be acquired by extending the exposure time, but the ratio of the number of blackened pixels on the low luminance side to the total number of pixels is, for example, less than 0.1% Is a sufficiently small value with respect to the total number of pixels, and is determined to be a sufficient exposure amount.

  On the other hand, when it is determined that the ratio of the number of blackened pixels on the low luminance side to the total number of pixels is, for example, 0.1% or more (step S74; NO), the previous step in step S24 of FIG. A change in the number of blackened pixels on the low luminance side from the determination time is determined (step S76). If it is determined in step S76 that the number of blackened pixels on the low luminance side has changed since the previous determination (step S24 in FIG. 6) (for example, if the total number of pixels is 10 million pixels, When the number of blackened pixels on the low-brightness side is about 100,000 pixels at the time of this determination, and the number of blackened pixels on the low-brightness side is reduced to about 50,000 pixels at the time of this determination) (Step S76; NO), there is a possibility that new image data information on the low luminance side can be acquired by extending the exposure time, and it is determined that the first composite exposure is underexposed (step S77).

  If it is determined in step S76 that the number of blackened pixels on the low luminance side has hardly changed since the previous determination (step S24 in FIG. 6) (step S76; YES), the exposure time is extended. Nevertheless, the number of blackish pixels on the low-luminance side is almost unchanged, and it is assumed that the low-luminance side of the image is likely to be dark, and the first composite exposure has a sufficient exposure amount. (Step S75).

  If it is determined in the determination process of step S59 that the first composite exposure is sufficient exposure (sufficient exposure amount) (step S60; YES), a signal is output from the CMOS sensor 20 by the third imaging in step S57. Subsequent processing for the third exposure image data captured by the camera I / F 34 of the processing unit 21 is stopped (step S61), and the first combined exposure image data is output to the image data processing unit 37 (step S62). The third exposure image data and the first composite exposure image data are stored in the SDRAM 22 via the memory controller 35.

  The image data processing unit 37 converts the first composite exposure image data read from the SDRAM 22 through the memory controller 35 into YUV format image data, and further sets the white balance, and then the resize processing unit 38 records the number of recorded pixels. The data compression unit 40 compresses the image data into JPEG format image data. The compressed image data such as JPEG format is written back to the SDRAM 23, read out from the SDRAM 23 via the memory controller 35, and recorded on the memory card 14 via the media I / F 41.

  In the second sufficient exposure determination process in step S59, if it is determined that the first combined exposure is not a sufficient exposure amount (insufficient exposure) (step S60; NO), the third exposure in the third imaging is performed. A fourth exposure a4 (see FIG. 4) by the fourth imaging is performed so as to be continuous with a3 (step S63). In the present embodiment, the time of the fourth exposure a4 by the fourth imaging is four times (4/15 (= 16/60) seconds) the time of the second exposure a2 in the second imaging as described above.

  Then, the third exposure image data read from the SDRAM 23 via the memory controller 35 and the first combined exposure image data are cumulatively added and combined by the image data combining unit 43 to generate second combined exposure image data ( Step S64). Then, a third sufficient exposure determination process is performed on the second composite exposure image data by the exposure determination unit 36 to determine whether the exposure is sufficient (a sufficient exposure amount) (step S65).

  Here, the third sufficient exposure determination process by the exposure determination unit 36 in step S65 will be described with reference to the flowchart shown in FIG.

  First, the second composite exposure image data generated in step S64 of FIG. 11 is fetched (step S81), and a luminance histogram is generated from the second composite exposure image data (step S82). Then, based on the luminance histogram generated in step S82, the ratio of the number of pixels crushed in black on the low luminance side to the total number of pixels is determined (step S83). Note that the blackened pixel on the low luminance side in step S83 is a pixel in which the low luminance side of the image is blackened due to insufficient exposure time, or a pixel in which the low luminance side of the image is blackened in the dark state. Is the case.

  Then, when it is determined that the ratio of the number of blackish pixels on the low-luminance side to the total number of pixels is less than 0.1%, for example (step S84; YES), the second combined exposure has a sufficient exposure amount. Determination is made (step S85). That is, there is a possibility that the image data information on the low luminance side can be acquired by extending the exposure time, but the ratio of the number of blackened pixels on the low luminance side to the total number of pixels is, for example, less than 0.1% Is a sufficiently small value with respect to the total number of pixels, and is determined to be sufficient exposure.

  On the other hand, when it is determined that the ratio of the number of blackened pixels on the low luminance side to the total number of pixels is, for example, 0.1% or more (step S84; NO), the previous step in step S74 of FIG. A change in the number of blackened pixels on the low luminance side from the determination time is determined (step S86). In step S86, when it is determined that the number of blackened pixels on the low luminance side has changed significantly since the previous determination (step S74 in FIG. 12) (for example, when the total number of pixels is 10 million pixels, When the number of blackened pixels on the low-luminance side at the previous judgment is about 50,000 pixels, and the number of blackened pixels on the low-luminance side at the current judgment is changed to decrease to about 10,000 pixels (Step S86; NO), there is a possibility that new image data information on the low luminance side can be acquired by extending the exposure time, and it is determined that the second composite exposure is underexposed (Step S87).

  Further, when it is determined in step S86 that the change in the number of blackened pixels on the low luminance side is small and hardly changed from the previous determination (step S74 in FIG. 12) (step S86; YES), the exposure time. Although the number of pixels crushed in black on the low-luminance side has hardly changed in spite of extending the length of the image, it is presumed that the low-luminance side of the image is likely to be dark, and the second composite exposure is sufficient. It is determined that the exposure amount is high (step S85).

  If it is determined in the determination process in step S65 that the second composite exposure is sufficient exposure (sufficient exposure amount) (step S66; YES), the CMOS sensor 20 is captured by the fourth imaging in step S63. Thereafter, the subsequent processing for the fourth exposure image data captured by the camera I / F 34 of the signal processing unit 21 is stopped (step S67), and the second composite exposure image data is output to the image data processing unit 38 (step S68). ). The fourth exposure image data and the second composite exposure image data are stored in the SDRAM 22 via the memory controller 35.

  The image data processing unit 37 converts the second composite exposure image data read from the SDRAM 22 via the memory controller 35 into YUV format image data, and further sets the white balance, and then the resize processing unit 38 records the number of recorded pixels. The data compression unit 40 compresses the image data into JPEG format image data. The compressed image data such as JPEG format is written back to the SDRAM 23, read out from the SDRAM 23 via the memory controller 35, and recorded on the memory card 14 via the media I / F 41.

  In the third sufficient exposure determination process in step S65, if it is determined that the second composite exposure is not a sufficient exposure amount (insufficient exposure) (step S66; NO), the fourth exposure read from the SDRAM 22 is performed. The image data and the second combined exposure image data are accumulated and combined by the image data combining unit 43, and the generated third combined image data is output to the image data processing unit 37 (steps S69 and S70). The third composite image data is stored in the SDRAM 22 via the memory controller 35.

  The image data processing unit 37 converts the third composite image data read from the SDRAM 22 through the memory controller 35 into YUV format image data, and further sets the white balance, and then the resize processing unit 38 sets the number of recorded pixels. The data is converted into a corresponding size, and the data compression unit 40 compresses the image data in JPEG format or the like. The compressed image data such as JPEG format is written back to the SDRAM 23, read out from the SDRAM 23 via the memory controller 35, and recorded on the memory card 14 via the media I / F 41.

  In step S70, when it is determined that the second combined exposure is not a sufficient exposure amount (underexposure), the third combined image data is output to the image data processing unit 37. When it is determined that the exposure is not a sufficient exposure amount (underexposure) (step S66; NO), the second composite exposure is processed as underexposure (ie, exposure NG) without outputting the third composite image data. However, the processing may be such that image data is not output (recorded) (step S70).

  As described above, in the imaging apparatus according to the second embodiment, as in the first embodiment, during the monitoring operation, the above-described imaging operation by multiple exposures is executed simultaneously with the shooting start operation by the release 1 to the release 2 of the release button 2. As a result, since the pre-exposure processing for measuring the luminance of the subject first is not required at the start of shooting using the release button 1 from the release button 2 of the release button 2, the shutter time lag is almost eliminated, and the shooting timing intended by the photographer is eliminated. It becomes possible to perform imaging.

  Also in the second embodiment, since the rolling shutter function of the CMOS sensor 20 is used, the time lag between the imagings with different exposure amounts can be made substantially zero, and the imaging time can be further shortened.

  In addition, the photometric processing time at the time of general still image shooting with a single exposure requires substantially the same time as the total time between the first imaging and the third imaging in the second embodiment. That is, even in normal photometry processing, photometry is performed with an exposure time that is a predetermined exposure amount. The photometry time at this time is substantially the same as the time of the second imaging (1/60 seconds), and depends on the transfer frame rate of the CMOS sensor 20 described above. Although it is not used as the final image data, the image data is acquired from the CMOS sensor 20, and the appropriate exposure is calculated by feeding back the evaluation result obtained from the acquired image data.

  As described above, the exposure time of the first imaging in the second embodiment is sufficiently shorter than the exposure time of the second imaging, and also in the photometric process at the time of general still image shooting with a single exposure. In consideration of performing a plurality of times of photometry processing, the total time between the first imaging and the third imaging in the second embodiment is substantially equal to the photometry time at the time of taking a still image with a general single exposure. Can be considered.

  In the first and second embodiments, four exposures (four imagings) are set as the plurality of exposures described above. However, the set number of exposures (imaging times) is not limited to four. For example, It may be twice, three times, or five times or more. In addition, the number of times of exposure (number of times of imaging) (two or more times) may be set in advance, and the exposure (imaging) may be terminated when the number of times of exposure (number of times of imaging) reaches the set number of times. A configuration may be adopted in which a time until the end time is set in advance and a plurality of exposures (imaging) are performed within the set time.

  In the second embodiment, the exposure time for the first imaging is set to be the shortest for each subsequent imaging. However, the present invention is not limited to this setting. For example, the exposure time for the first imaging is maintained. You may set so that it may image repeatedly, and the exposure time of 1st imaging and the exposure time of 2nd imaging are the same time and the shortest time (for example, 1/960 which is the time of the above-mentioned 1st exposure a1). (= 1 / (60 × 16)) seconds) and may be set so as to be longer for each subsequent imaging.

  In addition, a technique for expanding the dynamic range of an image by continuously imaging a plurality of times with different exposure amounts for the same subject and synthesizing a plurality of obtained image data is conventionally known. The technique of the present invention described above (Embodiments 1 and 2) can also be applied to such an image dynamic range expansion process.

  That is, in the first and second embodiments, for example, the first exposure image data of the first imaging and the second exposure image data of the second imaging are obtained with respect to the final exposure image data finally obtained by the sufficient exposure determination process. An image with an expanded dynamic range can be obtained by combining arbitrary selected exposure image data such as.

  In addition, when the technique of the present invention is applied to the dynamic range expansion process of an image as described above, the shutter time lag is almost eliminated because the pre-exposure process is unnecessary as described above, and the time from the start of photographing to the end of exposure. Can be shortened.

  In the above example, the technique of the present invention is applied to the dynamic range expansion processing of an image. However, in addition to this, pre-exposure processing is not required at the start of photographing as in the present invention, and the shutter time lag is almost eliminated. It is possible to combine the points that can be eliminated with other technologies.

(A) is a front view which shows the digital camera as an example of the imaging device which concerns on Embodiment 1 of this invention, (b) is the top view, (c) is the back view. 1 is a block diagram showing an outline of a system configuration in a digital camera as an example of an imaging apparatus according to Embodiment 1 of the present invention. The figure for demonstrating the rolling shutter function of a CMOS sensor. The timing chart of the exposure time in the 1st imaging-the 4th imaging using the rolling shutter function of a CMOS sensor. 5 is a flowchart showing an exposure process in Embodiment 1 of the present invention. 5 is a flowchart showing a first sufficient exposure determination process in Embodiment 1 of the present invention. 7 is a flowchart showing second sufficient exposure determination processing according to the first embodiment of the present invention. 10 is a flowchart showing third sufficient exposure determination processing according to the first embodiment of the present invention. (A) is a timing chart at the time of normal imaging in which conventional pre-exposure processing is performed, and (b) is a timing chart at the time of normal imaging when the exposure processing of Embodiment 1 of the present invention is performed. The block diagram which shows the outline | summary of the system configuration | structure in the digital camera as an example of the imaging device which concerns on Embodiment 2 of this invention. 9 is a flowchart showing exposure processing in Embodiment 2 of the present invention. 9 is a flowchart showing a second sufficient exposure determination process in Embodiment 2 of the present invention. 9 is a flowchart showing a third sufficient exposure determination process in Embodiment 2 of the present invention.

Explanation of symbols

1 Digital camera (imaging device)
5 photographic lens system 6 lens barrel unit 9 liquid crystal monitor 12 menu button 20 CMOS sensor (imaging means)
21 signal processing unit 22 SDRAM
24 ROM
26 Control unit (control means)
30 light-receiving part 33 TG (control means)
34 Camera Interface 35 Memory Controller 36 Exposure Determination Unit (Exposure Evaluation Unit)
37 Image data processing unit 43 Image data synthesis unit (image data synthesis means)

Claims (8)

Imaging means for outputting captured image data;
Control means for controlling the image pickup means to sequentially pick up images with a plurality of set exposure times;
Exposure evaluation means for evaluating the exposure amount of the image data acquired by the imaging means,
When the photographing is started, the control means first continuously performs imaging by at least two exposures, and when the first image data is acquired by the first imaging, the first image is parallel to the second imaging. When the data is evaluated by the exposure evaluation means and it is determined that the exposure amount is sufficient, the image data at the time of determination is set as final image data, and the subsequent image data output by the second imaging Stop processing,
When it is determined that the exposure amount of the first image data is not sufficient, the second image data is acquired by the second imaging, and the second image data is exposed to the exposure in parallel with the third imaging. When the evaluation unit evaluates and determines that the exposure amount is sufficient, the image data at the time of this determination is set as final exposure image data, and the subsequent processing of the image data output by the third imaging is stopped. ,
When it is determined that the exposure amount of the second image data is not sufficient, the exposure time by the first imaging is the shortest for each subsequent imaging until the exposure evaluation unit determines that the exposure amount is sufficient. An imaging device that repeatedly performs imaging so as to be long. Imaging means for outputting captured image data;
Control means for controlling the image pickup means to sequentially pick up images with a plurality of set exposure times;
Exposure evaluation means for evaluating the exposure amount of the image data acquired by the imaging means;
Image data synthesizing means that sequentially synthesizes image data output from the imaging means when calculating images with the set exposure time, and calculates composite exposure image data;
When the photographing is started, the control means first continuously performs imaging by at least two exposures, and when the first image data is acquired by the first imaging, the first image is parallel to the second imaging. When the data is evaluated by the exposure evaluation means and it is determined that the exposure amount is sufficient, the image data at the time of determination is set as final image data, and the subsequent image data output by the second imaging Stop processing,
When it is determined that the exposure amount of the first image data is not sufficient, a first composite image obtained by combining the first image data and the second image data obtained by the second imaging by the image data combining unit Data is acquired, and the first composite image data is evaluated by the exposure evaluation means in parallel with the third imaging. When it is determined that the exposure amount is sufficient, the image data at the time of this determination is subjected to final exposure. The image data and the subsequent processing of the image data output by the third imaging are stopped,
When it is determined that the exposure amount of the first composite image data is not sufficient, the second composite image data and the third image data obtained by the third imaging are combined by the image data combining unit. When the composite image data is acquired, the second composite image data is evaluated by the exposure evaluation means in parallel with the fourth imaging, and when it is determined that the exposure amount is sufficient, the image data at the time of the determination is obtained. The final image data and the subsequent processing of the image data output by the fourth imaging are stopped,
When it is determined that the exposure amount of the second composite image data is not sufficient, repeated imaging is performed based on the plurality of set exposure times until the exposure evaluation unit determines that the exposure amount is sufficient. An imaging apparatus characterized by the above.   The imaging apparatus according to claim 2, wherein the plurality of set exposure times are set such that an exposure time by the first imaging is the shortest and becomes longer for each subsequent imaging.   4. The first and second imaging are started based on a signal from the control means without obtaining an optimum exposure amount when an instruction to start imaging is given by an operation by an operator. The imaging device according to any one of the above.   The exposure evaluation unit determines that the exposure amount is sufficient when the number of pixels determined to be black on the low luminance side is smaller than a predetermined ratio with respect to all pixel data to be determined. The imaging device according to any one of claims 1 to 4.   The exposure evaluation unit identifies a pixel that is crushed black when it is determined that the exposure amount is not sufficient, and determines a change in luminance information of the specific pixel based on image data acquired after the determined image data. The exposure amount is determined to be sufficient regardless of the predetermined ratio when the reduction number or the reduction ratio of the pixels in which blackout is eliminated or improved is smaller than a predetermined value. The imaging device described.   The imaging means is a CMOS sensor having a rolling shutter function, and an imaging operation by the imaging means and an exposure evaluation operation by the exposure evaluation means are performed in parallel using the rolling shutter function. Item 7. The imaging device according to any one of Items 1 to 6.   The first exposure time at the time of the first imaging and the second exposure time at the time of the second imaging are set according to a dynamic range and a transfer frame rate of the CMOS sensor. Imaging device.

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