JP5123828B2 - Imaging device - Google Patents

Description

  The present invention relates to an image pickup apparatus, and more particularly to an image pickup apparatus that accurately calculates a strobe emission amount when shooting a moving object.

As disclosed in Patent Document 1, an imaging apparatus has been proposed in which pre-flash is performed before main shooting with strobe flash is performed, and the amount of flash emission in the main shooting is determined based on an image obtained by pre-flash. . Specifically, the amount of flash emission in the actual shooting is determined based on the difference between the luminance value of the image obtained in the frame where the pre-flash is emitted and the luminance value of the image obtained in the frame where the pre-flash is not executed. Is done.
JP 2002-359774 A

  However, when shooting a moving object (an object that moves relatively with respect to the imaging device), the position of the moving object varies between the frame image during pre-flash and the frame image without pre-flash. An accurate light emission amount cannot be calculated only by a difference in luminance values of the entire image.

  Accordingly, an object of the present invention is to provide an imaging apparatus that accurately calculates the amount of strobe emission when shooting a moving object.

  An imaging apparatus according to the present invention includes a pre-flash in response to an operation of a release button, a strobe that emits light at the time of main shooting performed after the pre-flash, and a plurality of frames obtained by imaging performed before the pre-flash. A calculation unit that determines whether or not a moving object is included in a plurality of frame images and specifies a motion vector of the moving object based on the image, and the calculation unit determines that a moving object is included in the plurality of frame images Then, based on the motion vector, the region of the moving body estimated in the first frame image obtained by the first imaging without strobe emission and the second frame obtained by the second imaging with strobe pre-emission The moving object area estimated in the image is calculated, and based on the luminance value of the moving object area in the first frame image and the luminance value of the moving object area in the second frame image And it calculates the light emission amount of the definitive strobe.

  When the moving object is included in the subject, the first frame image obtained by the first imaging performed when the pre-flash is not performed and the second frame image obtained by the second imaging performed when the pre-flash is performed are: Due to the time difference, the position of the moving object is different. For this reason, the position and size of the moving object in the first and second frame images are calculated from the motion vector of the moving object obtained before the pre-emission, such as before the release button is fully pressed, and the region of the moving object in the second frame image. And the light emission amount of the strobe at the time of the actual photographing is calculated based on the luminance value of the moving object and the luminance value of the moving object region in the first frame image. As a result, the amount of stroboscopic light emission is accurately calculated as compared with the case where the amount of light emission during the main photographing is calculated based on the overall luminance values of the first and second frame images without predicting the movement of the moving object. It becomes possible.

  Preferably, the calculation unit calculates the size of the moving object estimated in the third frame image obtained in the main shooting based on the motion vector, and considers the size of the moving object in the third frame image to determine the light emission amount. calculate.

  Further, when the size of the moving object on the frame image changes, for example, when the distance between the imaging device 1 and the moving object changes, the moving object estimated in the third frame image obtained by the main photographing from the motion vector of the moving object The amount of flash emission is calculated in consideration of the area (size). Thereby, it becomes possible to calculate the light emission amount of the strobe more accurately.

  Preferably, the calculation unit determines whether or not a moving object is included in the plurality of frame images based on a plurality of frame images obtained by imaging before the release button is fully pressed, and the movement of the moving object. Perform vector identification.

  Since it is determined whether or not a moving object is included based on a frame image obtained by imaging before the release button is fully pressed, compared to a case based on a frame image obtained by imaging after the release button is fully pressed. Thus, the calculation processing after the release button is fully pressed does not increase greatly, and the occurrence of a release time lag can be suppressed.

  As described above, according to the present invention, it is possible to provide an imaging apparatus that accurately calculates the amount of strobe light emitted when a moving object is imaged.

  Hereinafter, the present embodiment will be described with reference to the drawings. The imaging device 1 is a digital camera. The part relating to the imaging of the imaging apparatus 1 includes a power button 9 and a release button 13 that are used for switching on and off the power source of the imaging apparatus 1, a control unit 30 that controls each unit, a lens driving unit 45, and an exposure control unit. 47, a lens 51, an image pickup device 53 such as a CCD, an AFE (analog front end) 55, a DSP (video signal processing circuit) 60, a strobe 65, a recording unit 70, and a display unit 90 (see FIG. 1).

  The subject image is captured by the image sensor 53 as an optical image via the lens 51. Image data obtained by imaging is converted from an analog signal to a digital signal by the AFE 55, and image processing is performed by the DSP 60. Such an operation is performed at regular time intervals (1/30 seconds), and a through image is displayed on the display unit 90 based on the image data (live view display).

  The DSP 60 compares frame images between a plurality of frames obtained by imaging at regular time intervals, detects a portion where there is a change, and a moving object in the frame image (an object that moves relatively with respect to the imaging device 1). It is determined whether or not the item is included. If included, the DSP 60 specifies the motion vector (position, size, moving direction, and moving speed) of the moving object. The determination of whether or not a moving object is included in the frame image and the specification of the motion vector of the moving object are performed at regular intervals and until the release button 13 is fully pressed, and the latest information is the DSP 60 or the control unit 30 or the like. Is temporarily recorded. These pieces of information immediately before the release button 13 is fully pressed are used for calculating the light emission amount of the strobe 65 at the time of actual photographing. Further, after the end of the main photographing, it is determined again whether or not a moving object is included in the frame image and the motion vector of the moving object is specified.

  When the release button 13 is half-pressed, a photometric switch (not shown) is turned on, and photometry and distance measurement and focusing operations by the lens driving unit 45 are performed. Photometry is performed based on image data obtained by imaging with the image sensor 53. Specifically, the DSP 60 obtains a luminance value in the photometric area (information on the brightness of the subject) from the luminance signal generated in the image processing, and outputs this to the control unit 30 as a photometric result. The control unit 30 calculates an appropriate exposure (aperture and exposure time) based on the luminance value (exposure calculation). Distance measurement is performed based on the contrast of the image of the portion corresponding to the AF area from the image data obtained by imaging.

  In the present embodiment, the description has been given of the case where the photometry and the distance measurement are started after the release button 13 is pressed halfway. However, after the imaging apparatus 1 is turned on using the power button 9, the photometry and the distance measurement are always performed. The form which performs is also possible. In this case, when the release button 13 is half-pressed, the photometry or distance measurement operation is stopped, and the photometry or distance measurement result immediately before being half-pressed is used for the actual photographing.

  When the release button 13 is fully pressed, a release switch (not shown) is turned on, and the aperture and exposure time are controlled by the exposure control unit 47 so that imaging is performed with the exposure calculated by the control unit 30. In this state, actual imaging is performed. An image corresponding to the image data obtained by imaging is displayed on the display unit 90 after image processing in the DSP 60, and the image data is recorded in the recording unit 70.

  When the imaging device is set to the flash mode of the strobe 65, after the release button 13 is fully pressed, the first imaging in a state where the strobe 65 does not emit light and the strobe 65 based on the control of the control unit 30. The control unit 30 calculates the light emission amount of the strobe 65 in the main photographing based on the image data obtained by the first and second imaging (light control). ). In the actual photographing performed thereafter, the strobe 65 emits light with the light emission amount calculated by the light control. The strobe 65 may be configured integrally with the imaging apparatus 1 or may be configured separately.

  The calculation of the light emission amount of the strobe 65 in the actual photographing will be specifically described. The control unit 30 reads out a determination result as to whether or not a moving object is included in the frame image temporarily recorded immediately before the release button 13 is fully pressed, and when the moving image is included in the frame image, A first light emission amount calculation is performed, and if a moving object is not included in the frame image, a second light emission amount calculation is performed.

  When performing the first light emission amount calculation, the control unit 30 determines the moving object estimated at the time of the first imaging based on the information of the moving object motion vector temporarily recorded immediately before the release button 13 is fully pressed. The position and size on the first frame image (see FIG. 2) and the position and size on the second frame image of the moving object estimated at the time of the second imaging (see FIG. 3) are calculated.

  The upper left of FIG. 2 is the first frame image obtained by the first imaging, and the lower right shows the moving body region and the surrounding luminance value distribution in the first frame image. The upper left of FIG. 3 is the second frame image obtained by the second imaging, and the lower right shows the moving body region and the surrounding luminance value distribution in the second frame image.

  Note that the position and size of the moving object in the second frame image is estimated from the motion vector information obtained before the release button 13 is fully pressed. The second frame image obtained by imaging at the time of pre-flash is a strobe. Due to the 65 pre-light emission, the luminance of the subject is greatly changed compared to the first frame image obtained by the imaging before the pre-light emission, and the moving object in the second frame image is only compared with the first and second frame images. This is because it is considered that it is difficult to specify.

  After the first and second imaging, the control unit 30 represents the representative value (or average value) of the luminance values of the moving object region in the second frame image and the luminance of the region determined to be the moving object in the first frame image. Based on the difference between the value and the representative value (or average value), the light emission amount of the strobe 65 in the actual photographing is calculated.

  Further, when it is determined that the size of the moving object is fluctuating from the information of the motion vector obtained before the release button 13 is fully pressed, such as when the distance between the moving object and the imaging device 1 is changed, the control is performed. The unit 30 calculates the size of the moving object area estimated in the third frame image obtained at the time of the main photographing, and reflects the size of the area in the calculation of the light emission amount of the strobe 65 in the main photographing. For example, when the moving object region in the third frame image is small, the light emission amount is controlled to be increased, and when the moving object region is large, the light emission amount is controlled to be decreased.

  When performing the second light emission amount calculation, the control unit 30 uses the representative value (or average value) of the luminance values of the second frame image without using the motion vector information obtained before the release button 13 is fully pressed. Based on the difference from the representative value (or average value) of the luminance values of the first frame image, the light emission amount of the strobe 65 in the main photographing is calculated (normal light emission amount calculation).

  Next, the procedure from when the release button 13 is fully pressed until the actual shooting is performed will be described with reference to the flowchart of FIG. When the release button 13 is fully pressed, in step S11, the control unit 30 determines whether or not the imaging apparatus 1 is in the strobe light emission mode. If the flash emission mode is set, the process proceeds to step S12. If not, the process proceeds to step S15. In step S12, the control unit 30 reads the determination result as to whether or not a moving object is included in the frame image temporarily recorded immediately before the release button 13 is fully pressed, and the moving object is included in the subject (frame image). It is determined whether or not. If it is included, the process proceeds to step S13. If it is not included, the process proceeds to step S14.

  In step S13, the first light emission amount calculation of the strobe 65 corresponding to a case where a moving object is included in the subject is performed. Details of this calculation will be described later using the flowchart of FIG. In step S14, the second light emission amount calculation of the strobe 65 corresponding to the case where the moving object is not included in the subject, that is, the normal light emission amount calculation is performed. In step S15, actual shooting is performed, and the strobe 65 emits light with the light emission amount calculated in step S13 or step S14 in the actual shooting.

  Next, details of the calculation of the light emission amount of the strobe 65 corresponding to a case where a moving object is included in the subject will be described using the flowchart of FIG. In step S31, based on the information of the motion vector temporarily recorded immediately before the release button 13 is fully pressed, the position and size of the moving object on the first frame image estimated at the time of the first imaging, and the second The position and size of the moving object estimated at the time of imaging on the second frame image are calculated. In step S32, the first imaging without light emission of the strobe 65 and the second imaging with pre-light emission by the strobe 65 are performed, and the DSP 60 displays the moving object region in the first and second frame images calculated in step S31. The control unit 30 calculates the difference between the luminance value of the moving object region in the second frame image and the luminance value of the moving object region in the first frame image. Further, when the size of the moving object is changed based on the motion vector information temporarily recorded immediately before the release button 13 is fully pressed, the control unit 30 performs the operation based on the motion vector information. Then, the size of the area of the moving object estimated in the third frame image obtained at the time of the main photographing is calculated. In step S <b> 33, the control unit 30 calculates the light emission amount of the strobe 65 at the time of actual shooting based on the difference in luminance values and the size of the moving object in the third frame image. When the size of the moving object has not changed, the size of the moving object is not taken into account in the calculation of the light emission amount of the strobe 65 during the main photographing.

  When the moving object is included in the subject, the first frame image obtained by the first imaging performed when the pre-flash is not performed and the second frame image obtained by the second imaging performed when the pre-flash is performed are: Due to the time difference, the position of the moving object is different. For this reason, the position and size of the moving object in the first and second frame images are calculated from the motion vector of the moving object obtained before the release button 13 is fully pressed, and the luminance value of the moving object region in the second frame image is calculated. Based on the luminance value of the moving object region in the first frame image, the light emission amount of the strobe 65 at the time of the main photographing is calculated. Thus, the amount of light emitted by the strobe 65 can be calculated more accurately than in the case where the amount of light emitted during actual photographing is calculated based on the overall luminance values of the first and second frame images without predicting the movement of the moving object. It becomes possible to do. Further, since it is determined whether or not a moving object is included based on a frame image obtained by imaging before the release button 13 is fully pressed, a frame image obtained by imaging after the release button 13 is fully pressed is determined. Compared with the case based on this, the calculation processing after the release button 13 is fully pressed does not increase greatly, and the occurrence of a release time lag can be suppressed.

  Further, when the size of the moving object on the frame image changes, such as when the distance between the imaging device 1 and the moving object changes, the actual shooting is performed from the moving object motion vector obtained before the release button 13 is fully pressed. The amount of light emitted by the strobe 65 is calculated in consideration of the area (size) of the moving body estimated in the obtained third frame image. This makes it possible to calculate the light emission amount of the strobe 65 more accurately.

  In the present embodiment, the determination of whether or not there is a moving object and the calculation of the position and size of the moving object in the third frame image obtained by shooting at the time of pre-flash are obtained by imaging before the release button 13 is fully pressed. Although the description has been made with respect to the frame image that is obtained based on the frame image, the image may be performed based on the frame image obtained by imaging after the release button 13 is fully pressed.

  In addition, the DSP 60 determines the presence or absence of moving objects in the frame image and specifies the motion vector, and the control unit 30 calculates the light emission amount of the strobe 65 based on these. The form performed by a part may be sufficient and the form performed by one arithmetic circuit (arithmetic part) may be sufficient.

It is a block diagram of the imaging device in this embodiment. It is a figure which shows the luminance value distribution of a 1st frame image and a 1st frame image. It is a figure which shows the luminance value distribution of a 2nd frame image and a 2nd frame image. It is a flowchart which shows the operation | movement procedure until this imaging | photography is performed. 6 is a flowchart illustrating a procedure for calculating a flash light amount corresponding to a case where a moving object is included in a subject.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Imaging device 9 Power button 13 Release button 30 Control part 45 Lens drive part 47 Exposure control part 51 Lens 53 Image pick-up element 55 AFE
60 DSP
65 Strobe 70 Recording unit 90 Display unit

Claims (3)

Pre-flash in response to the operation of the release button, a strobe that emits light at the time of main shooting after the pre-flash,
An arithmetic unit that determines whether or not a moving object is included in the plurality of frame images and specifies a motion vector of the moving object based on a plurality of frame images obtained by imaging performed before the pre-light emission. Prepared,
When the calculation unit determines that a moving object is included in the plurality of frame images, the calculation unit is estimated based on the motion vector in a first frame image obtained by first imaging without light emission of the strobe. Calculating a region of the moving object and the region of the moving object estimated in the second frame image obtained by the second imaging with the pre-flash of the strobe, and a luminance value of the region of the moving object in the first frame image; An image pickup apparatus that calculates a light emission amount of the strobe in the main photographing based on a luminance value of the moving object region in the second frame image.   The calculation unit calculates a size of the moving object estimated in the third frame image obtained by the main photographing based on the motion vector, and considers the size of the moving object in the third frame image. The imaging apparatus according to claim 1, wherein the light emission amount is calculated.   The imaging apparatus according to claim 1, wherein the calculation unit performs the determination and the identification based on a plurality of frame images obtained by imaging before the release button is fully pressed.

Images