JP6089390B2 - Imaging apparatus and signal readout method - Google Patents

Description

  The present invention relates to an imaging apparatus and a signal readout method.

  An imaging apparatus such as a digital still camera has a function of displaying an image input from an imaging device as a live view using a liquid crystal monitor or an electronic viewfinder. In addition to the drive mode for still image shooting, the image sensor that supports the live view display function has a drive mode for live view display that can input images with a lower resolution than still image shooting by pixel mixing and thinning. .

  Also, using the image input during live view display, the contrast of the input image is acquired while changing the lens focus position (focus position), and focus adjustment (contrast autofocus (AF)) is performed. An imaging apparatus equipped with a function to perform is known.

  However, in a conventional digital still camera, the driving method (drive mode) of the image sensor for live view display may not be suitable for focus adjustment. For example, during live view display, it is desirable that the depth of field is deep in order to make it easier to check the subject. For this purpose, high-sensitivity driving that provides a sufficiently bright image even when the lens aperture is reduced. The method is desirable. On the other hand, when adjusting the focus, the shallower the depth of field, the greater the change in contrast at each focus position, making it easier to adjust the focus. It is desirable that the driving method has a lower sensitivity than the video for live view display.

  The luminance adjustment of the input video is realized by the amplifier circuit that amplifies the input signal and the electronic shutter function of the image pickup device. If the effect of the luminance adjustment is not sufficient even if these are used, live view display and focus adjustment are possible. I couldn't do it well.

  In view of this, for example, an imaging apparatus and an imaging method that optimize the driving of the imaging device by changing the frame rate and the resolution of the input image in accordance with the depth of field of the lens during focus adjustment are disclosed. (For example, refer to Patent Document 1).

  However, in the imaging apparatus and imaging method of Patent Document 1 described above, there is no change in the depth of field itself in both the focus adjustment and the live view display, and therefore it is impossible to obtain a better depth of field for focus adjustment. There was a problem.

  In addition, when the speedlight (strobe) is preliminarily emitted by the same driving method as that of the image sensor at the time of live view display, there is a problem that pixel saturation occurs when the speedlight is preliminarily emitted.

  As described above, when the same imaging element driving method is used for different processes performed in the imaging apparatus, exposure conditions suitable for the respective processes cannot be obtained, and the obtained processing results may not be obtained.

  The present invention has been made in view of the above, and when processing is performed by the imaging apparatus, each processing is performed by switching to the driving method of the image sensor with the number of added pixels corresponding to the processing. It is an object of the present invention to provide an image pickup apparatus and a signal readout method that can realize exposure conditions suitable for the above.

In order to solve the above-described problems and achieve the object, the present invention adds an image pickup device and a plurality of same-color pixel signals from the image pickup device according to the processing content executed in the image pickup device. A mode for switching between a first drive mode for reading out image signals and a second drive mode for reading out image signals by adding a plurality of same-color pixel signals from the image sensor with a smaller number of additions than the same-color pixel signals in the first drive mode According to a switching unit, a reading unit that reads an image signal from the imaging device, and a luminance evaluation value calculated from the image signal read by the reading unit according to the first driving mode or the second driving mode. an evaluation value obtaining unit, a lens, a diaphragm mechanism that the lens to limit the amount of incident light collected, read out by said reading means And an image signal, by adjusting the throttle mechanism by using the evaluation value obtained by the evaluation value acquiring means includes an adjustment means for performing exposure control and iris diaphragm adjustment, the said adjustment means, said first In the second drive mode, the aperture of the diaphragm mechanism is adjusted to be opened more than in the first drive mode.

According to another aspect of the present invention, there is provided a signal reading method executed by the imaging apparatus, wherein the first driving mode reads out an image signal by adding a plurality of same-color pixel signals from the imaging element according to the processing content executed in the imaging apparatus. A mode switching step of switching between a second drive mode in which a plurality of same color pixel signals are added from the image sensor and an image signal is read out with a smaller number of additions than the same color pixel signals in the first drive mode, and the first drive mode or Based on the second drive mode, a read step of reading an image signal from the image sensor, an evaluation value acquisition step of acquiring a luminance evaluation value calculated from the read image signal, and a read step using the image signals, and the evaluation value acquired by the evaluation value acquiring step, the lens is light collected An adjustment step of adjusting exposure control and aperture adjustment by adjusting an aperture mechanism that limits the amount of radiation, wherein the adjustment step is performed in the second drive mode rather than in the first drive mode. The diaphragm mechanism is adjusted to open the diaphragm.

  According to the present invention, when processing is performed by the imaging apparatus, it is possible to realize an exposure condition suitable for each processing.

FIG. 1 is a functional block diagram of the configuration of the digital camera according to the first embodiment. FIG. 2 is an explanatory diagram of the 8-pixel addition mode. FIG. 3 is an explanatory diagram of the 4-pixel addition mode. FIG. 4 is an explanatory diagram of state transition of the digital camera according to the present embodiment. FIG. 5 is a flowchart for explaining processing when the release button is half-pressed. FIG. 6 is a flowchart for explaining processing when the focus adjustment operation is completed. FIG. 7 is an explanatory diagram of state transition of the digital camera according to the present embodiment. FIG. 8 is a flowchart for explaining processing when the release button is fully pressed.

(Embodiment 1)
Hereinafter, embodiments of an imaging device and a signal readout method will be described in detail with reference to the accompanying drawings. Here, an example in which the present invention is applied to a digital still camera (hereinafter simply referred to as a “digital camera”) will be described. However, the present invention is widely applied to an imaging apparatus including a display unit that displays a live view. Can be applied.

  The digital camera according to the present embodiment captures and records a still image according to the operation of the release button, and displays an image read from the image sensor on the display unit as a live view before capturing. Here, the live view is a function that allows the user of the digital camera to shoot while checking the subject at the time of shooting, and the user can determine the shooting angle of view by this function.

  FIG. 1 is a functional block diagram of the configuration of the digital camera according to the first embodiment. As shown in FIG. 1, the digital camera of the present embodiment includes a lens unit 11, an image sensor 13, an image processing LSI (Large Scale Integration) 14, an LCD (Liquid Crystal Display) 15, a controller 16, An operation board 17 and a speedlight 19 are mainly provided. The controller 16, the lens unit 11, the image sensor 13, the image processing LSI 14, the operation board 17, and the speedlight 19 are connected by a control signal line. Further, the image processing LSI 14, the image sensor 13 and the LCD 15 are connected by a data bus.

  The lens unit 11 includes a lens (not shown) and a diaphragm mechanism 12. The lens is an optical component that optically forms an image on the image sensor 13 and is installed on the light receiving surface side of the image sensor 13 so as to be movable in the optical axis direction by driving an actuator (not shown) or manually operated by a photographer. Has been. The aperture mechanism 12 limits the amount of incident light collected by the lens, and adjusts the depth of field and the amount of light according to the aperture amount.

  The image sensor 13 is configured using a CCD (Charge Coupled Device), a CMOS (Complementary Metal Oxide Semiconductor), or the like, receives incident light collected by the lens unit 11, and performs photoelectric conversion to generate an image signal (digital signal). ) Is output.

  The image processing LSI 14 generates contrast image calculation, average luminance (luminance average value) and luminance evaluation value, and display image data from the image signal output from the image sensor 13.

  The LCD 15 is a liquid crystal screen that displays characters and images, and displays image data for display output from the image processing LSI 14.

  The operation board 17 is a board provided with various buttons and switches to be operated by the user of the digital camera, and includes a release button 18. The release button 18 is a button that accepts two-stage input of half-press and full-press according to the amount of pressing.

  The speedlight 19 emits illumination light, and is composed of, for example, a xenon lamp or an LED (Light Emitting Diode).

  The controller 16 includes a control program, and performs sequence control by connecting the lens unit 11, the image sensor 13, the image processing LSI 14, the LCD 15, the operation board 17, and the speedlight 19. The controller 16 includes an input receiving unit 101, a mode switching unit 102, a reading unit 103, an evaluation value acquisition unit 104, an aperture adjustment unit 105, a focus adjustment unit 106, a display control unit 107, and a light emission control unit 108. And a photometric unit 109.

  When the user of the digital camera presses the release button 18 halfway or fully, the input receiving unit 101 receives an instruction input corresponding to them. In the present embodiment, the input receiving unit 101 receives a focus adjustment (autofocus) instruction input when the release button 18 is half-pressed, and receives a photometric instruction input when the release button 18 is fully pressed. .

  The mode switching unit 102 adds an 8-pixel same-color pixel signal from the image sensor 13 and reads an image signal, which is a drive mode of the image sensor 13, according to the processing executed by the digital camera. 1-drive mode) and a 4-pixel addition mode (second drive mode) in which the same color pixel signals of 4 pixels (the number of additions smaller than the same-color pixel signal in the 8-pixel addition mode) are added from the image sensor 13 to read the image signal It is to switch.

  The mode switching unit 102 switches to the 8-pixel addition mode when performing live view display for determining the shooting angle of view, and switches to the 4-pixel addition mode when executing focus adjustment. Further, in the digital camera of the present embodiment, when the focus adjustment operation is finished, the display changes to live view display (see FIG. 4), so that the mode switching unit 102 switches to the 8-pixel addition mode after the focus adjustment is finished. Become.

  Below, each drive mode is demonstrated concretely. First, the arrangement of color filters in the image sensor 13 will be described. In the image sensor 13 of the present embodiment, color filters are arranged in a Bayer array. Here, the Bayer array is a line in which a filter that transmits the red (R) wavelength in the horizontal direction and a filter that transmits the green (G) wavelength are alternately arranged, and a filter that transmits the green wavelength. And a line in which filters that transmit blue (B) wavelengths are alternately arranged, and the two lines are also alternately arranged in the vertical direction. That is, the green filter is used twice as much as the red and blue filters (see FIGS. 2 and 3).

  FIG. 2 is an explanatory diagram of the 8-pixel addition mode. The 8-pixel addition mode shown in FIG. 2 is a drive mode that is switched during live view display. As shown in FIG. 2, in the 8-pixel addition mode, pixel signals for 2 pixels are added from the image sensor 13 every 16 lines in the vertical direction, and pixel signals for 4 lines (4 pixels) in the horizontal direction. Are added and read out, and the pixel signals for a total of 8 pixels are added to output the read image signal. Therefore, as compared with a case where pixel signals of all the pixels are read from the image sensor 13, an image having a resolution of 1/16 in the vertical direction and 1/4 in the horizontal direction is output. In addition, the sum of the pixel signals of the eight pixels is output as an image signal as compared with reading of the image signal by thinning, so that the sensitivity is improved.

  FIG. 3 is an explanatory diagram of the 4-pixel addition mode. The 4-pixel addition mode shown in FIG. 3 is a drive mode that is switched during focus adjustment. As shown in FIG. 3, in the four-pixel addition mode, pixel signals for one pixel are added from the image sensor 13 every 16 lines in the vertical direction, and pixel signals for four lines (4 pixels) in the horizontal direction. Is added and read out, and the pixel signals for a total of four pixels are added to output the read image signal. Therefore, the resolution remains the same as in the 8-pixel addition mode described above, and an image having a resolution of 1/16 in the vertical direction and 1/4 in the horizontal direction is compared with the case where the pixel signals of all the pixels are read from the image sensor 13. Will be output. In addition, compared with the 8-pixel addition mode, the number of pixel additions is halved, so that pixel saturation is unlikely to occur, and an image signal with lower sensitivity than the 8-pixel addition mode can be output.

  The reading unit 103 reads an image signal from the image sensor 13 in accordance with the 8-pixel addition mode or the 4-pixel addition mode switched by the mode switching unit 102.

  The evaluation value acquisition unit 104 acquires a luminance evaluation value calculated from the image signal read by the reading unit 103. The luminance evaluation value is obtained by using the average luminance of pixels in a region such as a part of the input image or the entire image by the photometric method of the digital camera.

  The aperture adjustment unit 105 adjusts the aperture mechanism 12 of the lens unit 11 using the image signal read by the read unit 103 and the luminance evaluation value acquired by the evaluation value acquisition unit 104, and performs exposure control and aperture adjustment. It is.

  Specifically, when the aperture adjustment unit 105 is switched to the 4-pixel addition mode, the aperture of the aperture mechanism 12 is adjusted in the opening direction because the sensitivity is lower than that in the 8-pixel addition mode switched to the live view display. . This provides a shallow depth of field suitable for focus adjustment. On the other hand, when the mode is switched to the 8-pixel addition mode, since the sensitivity is higher than that in the 4-pixel addition mode that is switched during focus adjustment, the aperture of the aperture mechanism 12 is adjusted in the direction of aperture. Thereby, a deep depth of field suitable for live view display can be obtained. Therefore, when performing each process (live view display process and focus adjustment process) with the digital camera, it is possible to realize exposure conditions suitable for each process.

  The focus adjustment unit 106 adjusts the focus of an image captured from the lens when the release button 18 is half-pressed and a focus adjustment instruction input is received by the input reception unit 101.

  The display control unit 107 performs control to display the image data generated by the image processing LSI 14 on the LCD 15 as a live view or other video.

  The light emission control unit 108 emits illumination light from the speedlight 19 toward the visual field area captured by the digital camera. Further, the light emission control unit 108 performs preliminary light emission of the speedlight 19. Here, the preliminary light emission is a function of emitting light several times in advance before photographing in order to suppress a red-eye phenomenon that occurs during photographing in a dark place.

  The photometry unit 109 uses the light emitted from the speedlight 19 (preliminary light) to determine the exposure (combination of aperture value and shutter speed), and adjusts the brightness of the subject (the amount of light hitting the subject). The photometry is performed. The photometry unit 109 performs photometry when the release button 18 is fully pressed and a photometry instruction input is received by the input reception unit 101.

  Next, live view display and focus adjustment state transition in the digital camera of the present embodiment will be described. FIG. 4 is an explanatory diagram of state transition of the digital camera according to the present embodiment.

  First, when the power switch of the digital camera is turned on, a live view is displayed. As shown in FIG. 4, when the display control unit 107 is in the live view display state (step S1), the input receiving unit 101 receives a half-press of the release button 18 (instruction input for focus adjustment) (step S2). ) And the focus adjustment unit 106 shifts to a focus adjustment (autofocus) state (step S3). When the focus adjustment operation is completed (step S4), the display control unit 107 returns to the live view state again.

  Next, processing when the release button 18 is half-pressed, that is, when focus adjustment is executed will be described. FIG. 5 is a flowchart for explaining processing when the release button is half-pressed.

  First, the input receiving unit 101 determines whether or not a half-press of the release button 18 has been received (step S11), and if not received (step S11: No), it waits as it is. On the other hand, when received (step S11: Yes), the mode switching part 102 switches the drive mode of the image pick-up element 13 to 4 pixel addition mode (step S12). Then, the reading unit 103 reads an image signal for four pixels from the image sensor 13 in accordance with the four-pixel addition mode (step S13).

  Next, the evaluation value acquisition unit 104 acquires a luminance evaluation value calculated from the read image signal (step S14). Then, the diaphragm adjustment unit 105 adjusts the diaphragm mechanism 12 of the lens unit 11 using the acquired luminance evaluation value (step S15). At this time, since the 4-pixel addition mode has lower sensitivity than the 8-pixel addition mode that is switched during live view display, the aperture of the aperture mechanism 12 is adjusted in the opening direction. This provides a shallow depth of field suitable for focus adjustment. Then, the focus adjustment unit 106 adjusts the focus of the image captured from the lens (step S16).

  Next, processing when the focus adjustment operation is completed will be described. FIG. 6 is a flowchart for explaining processing when the focus adjustment operation is completed.

  First, the mode switching unit 102 determines whether or not the focus adjustment operation by the focus adjustment unit 106 has been completed (step S31), and if not completed (step S31: No), the mode switching unit 102 waits as it is. On the other hand, when completed (step S31: Yes), the mode switching unit 102 switches the drive mode of the image sensor 13 to the 8-pixel addition mode (step S32). Then, the readout unit 103 reads out an image signal for 8 pixels from the image sensor 13 in accordance with the 8-pixel addition mode (step S33).

  Next, the evaluation value acquisition unit 104 acquires a luminance evaluation value calculated from the read image signal (step S34). Then, the aperture adjustment unit 105 adjusts the aperture mechanism 12 of the lens unit 11 using the acquired luminance evaluation value (step S35). At this time, since the 8-pixel addition mode is more sensitive than the 4-pixel addition mode that is switched during focus adjustment, the aperture of the aperture mechanism 12 is adjusted in the direction of aperture. Thereby, a deep depth of field suitable for live view display can be obtained. Then, the display control unit 107 displays a live view on the LCD 15 (step S36).

  As described above, in the digital camera according to the present embodiment, when the focus adjustment process is performed, a low-sensitivity image can be displayed by switching to the 4-pixel addition mode. Therefore, the aperture of the aperture mechanism 12 is opened and focus adjustment is performed. A suitable shallow depth of field is obtained. On the other hand, when performing live view display processing, a high-sensitivity image can be displayed by switching to the 8-pixel addition mode, so that the aperture of the aperture mechanism 12 can be reduced to obtain a deep depth of field suitable for live view display. . Therefore, when performing each process (live view display process and focus adjustment process) with the digital camera of the present embodiment, it is possible to realize exposure conditions suitable for each process.

(Embodiment 2)
The digital camera according to the first embodiment switches to the 4-pixel addition mode when performing the focus adjustment process, and switches to the 8-pixel addition mode when performing the live view display process. On the other hand, the digital camera of the present embodiment switches to the 4-pixel addition mode when performing the speedlight photometry process, and switches to the 8-pixel addition mode when performing the live view display process. Thereby, the light control operation by the preliminary light emission of the speedlight is improved.

  First, since the configuration of the digital camera according to the second embodiment is the same as the configuration of the digital camera according to the first embodiment, a description will be given with reference to FIG. Hereinafter, only the configuration different from that of the first embodiment will be described.

  The mode switching unit 102 adds an 8-pixel same-color pixel signal from the image sensor 13 and reads an image signal, which is a drive mode of the image sensor 13, according to the processing executed by the digital camera. 1-drive mode) and a 4-pixel addition mode (second drive mode) in which the same color pixel signals of 4 pixels (the number of additions smaller than the same-color pixel signal in the 8-pixel addition mode) are added from the image sensor 13 and the image signal is read out. It is to switch.

  The mode switching unit 102 switches to the 8-pixel addition mode when performing live view display for determining the shooting angle of view, and switches to the 4-pixel addition mode when performing speedlight photometry. Here, the details of the 4-pixel addition mode and the 8-pixel addition mode are the same as those in the first embodiment, and thus the description thereof is omitted (see FIGS. 2 and 3).

  Next, live view display and speedlight photometry state transition in the digital camera of the present embodiment will be described. FIG. 7 is an explanatory diagram of state transition of the digital camera according to the present embodiment.

  First, when the power switch of the digital camera is turned on, a live view is displayed. Then, as shown in FIG. 7, when the display control unit 107 is in the live view display state (step S5), the input receiving unit 101 receives a full press of the release button 18 (photometric instruction input) (step S6). Then, the photometry unit 109 makes a transition to the photometry state of the speedlight (step S7).

  Next, a process when the release button 18 is fully pressed, that is, when the photometry of the speedlight 19 is executed will be described. FIG. 8 is a flowchart for explaining processing when the release button is fully pressed.

  First, the input receiving unit 101 determines whether or not a full press of the release button 18 has been received (step S51). If not received (step S51: No), the input receiving unit 101 waits as it is. On the other hand, when received (step S51: Yes), the mode switching part 102 switches the drive mode of the image pick-up element 13 to 4 pixel addition mode (step S52). Then, the reading unit 103 reads an image signal for four pixels from the image sensor 13 in accordance with the four-pixel addition mode (step S53).

  Next, the light emission control unit 108 performs preliminary light emission of the speedlight 19 (step S54), and the photometry unit 109 performs photometry using the light emitted from the speedlight 19 (step S55). At this time, since the 4-pixel addition mode has a lower sensitivity than the 8-pixel addition mode that is switched during live view display, pixel saturation during preliminary light emission of the speedlight 19 can be reduced.

  Live view display is executed after the speed metering is performed when the power switch of the digital camera is turned on, and processing when switching to the 8-pixel addition mode when performing live view display processing These are the same as in the first embodiment (see steps S32 to S36 in FIG. 6).

  As described above, in the digital camera of the present embodiment, when the preliminary light emission processing of the speedlight 19 is performed, a low-sensitivity image can be displayed by switching to the 4-pixel addition mode. Can be reduced. On the other hand, when performing live view display processing, a high-sensitivity image can be displayed by switching to the 8-pixel addition mode, so that the aperture of the aperture mechanism 12 can be reduced to obtain a deep depth of field suitable for live view display. . Therefore, when performing each process (live view display process, preliminary light emission process of the speedlight 19) with the digital camera of the present embodiment, it is possible to realize exposure conditions suitable for each process.

11 Lens Unit 12 Aperture Mechanism 13 Image Sensor 14 Image Processing LSI
15 LCD
DESCRIPTION OF SYMBOLS 16 Controller 17 Operation board 18 Release button 19 Speedlight 101 Input reception part 102 Mode switching part 103 Reading part 104 Evaluation value acquisition part 105 Aperture adjustment part 106 Focus adjustment part 107 Display control part 108 Light emission control part 109 Photometry part

JP 2010-187225 A

Claims (5)

In the imaging device,
An image sensor;
A first drive mode that reads out an image signal by adding a plurality of same-color pixel signals from the image-capturing device in accordance with the processing content to be executed in the imaging device, and the number of additions is smaller than that of the same-color pixel signal in the first drive mode. Mode switching means for switching between a second drive mode for reading out an image signal by adding a plurality of same-color pixel signals from the image sensor;
Reading means for reading out an image signal from the imaging device according to the first drive mode or the second drive mode;
Evaluation value acquisition means for acquiring a luminance evaluation value calculated from the image signal read by the reading means;
A lens,
A diaphragm mechanism for limiting the amount of incident light collected by the lens;
An adjustment unit that performs exposure control and aperture adjustment by adjusting the diaphragm mechanism using the image signal read by the reading unit and the evaluation value acquired by the evaluation value acquisition unit;
The image pickup apparatus according to claim 1, wherein the adjusting unit adjusts the aperture of the aperture mechanism in a direction in which the aperture is opened in the second drive mode rather than in the first drive mode.   The mode switching means switches to the first drive mode when performing live view display for determining a shooting angle of view, and switches to the second drive mode when performing focus adjustment. Item 2. The imaging device according to Item 1.   The imaging apparatus according to claim 2, wherein the mode switching unit switches to the first drive mode after the focus adjustment is completed.   The mode switching means switches to the first drive mode when performing live view display for determining a shooting angle of view, and switches to the second drive mode when performing photometry of illumination light. The imaging device according to claim 1. In the signal readout method executed by the imaging device,
A first drive mode that reads out an image signal by adding a plurality of same-color pixel signals from the image sensor according to the processing executed in the imaging device, and the imaging with a smaller number of additions than the same-color pixel signal in the first drive mode A mode switching step for switching between a second drive mode for reading out an image signal by adding a plurality of same-color pixel signals from the element;
A reading step of reading out an image signal from the image sensor based on the first drive mode or the second drive mode;
An evaluation value acquisition step of acquiring a luminance evaluation value calculated from the read image signal;
Using the image signal read out in the reading step and the evaluation value acquired in the evaluation value acquisition step, an aperture mechanism that limits the amount of incident light collected by the lens is adjusted, so that exposure control and aperture An adjustment step for making adjustments,
The signal reading method according to claim 1, wherein the adjusting step adjusts in a direction in which the aperture of the aperture mechanism is opened in the second drive mode rather than in the first drive mode.

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