JP2014236246A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce flickering of the brightness of an image in live view display.SOLUTION: An imaging apparatus 100 includes an imaging element 10 performing photoelectric conversion of a subject image imaged by an imaging optical system 1, and a display control section 17 for controlling the aperture value of an aperture 2 for adjusting the amount of incident light to the imaging element 10, the storage time of photoelectric conversion, and the sensitivity of photoelectric conversion, respectively, and a display control section 17 for controlling a display device 13 to sequentially display an image based on a photoelectric conversion signal from the imaging element 10. The imaging control section 17 changes the aperture value by driving the aperture 2 with a first driving speed when changing only the aperture value, and changes the aperture value by driving the aperture 2 with a second driving speed different from the first driving speed when changing at least one of the storage time and sensitivity together with the aperture value.

Description

  The present invention relates to an imaging apparatus.

  A technique is known that suppresses a rapid fluctuation (flickering) in image brightness during live view display in which images captured at a predetermined cycle are sequentially displayed on a display unit (see Patent Document 1). In the prior art, the sensitivity and shutter speed are changed with priority over the aperture, and when changing the aperture, the aperture is changed slowly.

JP 2011-172145 A

  However, when changing the aperture together with the sensitivity and shutter speed, the end of change of the aperture is slower than the end of change of sensitivity and shutter speed, so that the brightness of the image tends to flicker after the end of change of sensitivity and shutter speed. There is a problem.

  An image pickup apparatus according to the present invention includes an image pickup device that photoelectrically converts a subject image formed by an image pickup optical system, an aperture value of a diaphragm that adjusts the amount of light incident on the image pickup device, an accumulation time of photoelectric conversion, and sensitivity of photoelectric conversion And a display control unit for sequentially displaying an image based on the photoelectric conversion signal from the image sensor on the display device, and the imaging control unit is the first when only the aperture value is changed. When the diaphragm value is changed by driving the diaphragm at a driving speed of at least one, and at least one of the accumulation time and the sensitivity is changed together with the diaphragm value, the diaphragm is driven at a second driving speed different from the first driving speed. It is characterized by changing the value.

  With the imaging apparatus according to the present invention, it is possible to reduce flickering of the brightness of an image in live view display.

It is a block diagram which illustrates the composition of the digital camera by one embodiment of the invention. It is a flowchart explaining the flow of the process which a control part performs. It is a figure which illustrates a program diagram.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating the configuration of a digital camera 100 according to an embodiment of the present invention. The digital camera 100 includes a camera body 100A and a photographic lens 100B that can be attached to and detached from the camera body 100A.

  In FIG. 1, a camera body 100A includes a shutter 7, a shutter drive unit 8, a driver 9, an image sensor 10, an image processing unit 11, an image storage unit 12, a display unit 13, and an exposure control unit 14. , A photometric calculation unit 15, a communication unit 16, a control unit 17, and an operation member 18. The taking lens 100 </ b> B includes an imaging optical system 1, an aperture 2, an aperture drive unit 3, a driver 4, a lens control unit 5, and a lens communication unit 6.

  The imaging optical system 1 forms a subject image on the image sensor 10. The diaphragm 2 is an iris diaphragm that adjusts the amount of subject light incident on the image sensor 10. The aperture drive unit 3 changes the aperture diameter of the aperture 2. The driver 4 drives the aperture drive unit 3 in accordance with the aperture drive signal sent from the lens control unit 5. When the lens control unit 5 receives an aperture drive instruction from the camera body 100 via the lens communication unit 6, it sends an aperture drive signal to the driver 4. The lens communication unit 6 communicates with the communication unit 16 of the camera body 100A via a communication terminal provided on a lens mount (not shown).

  The shutter 7 controls the exposure time of the image sensor 10. The exposure time of the image sensor 10 can be controlled by a method for controlling the charge accumulation time in the image sensor 10 (so-called electronic shutter control). The shutter drive unit 8 drives the shutter 7 to open and close. The driver 9 drives the shutter drive unit 8 in accordance with the shutter drive signal sent from the control unit 17. When the exposure time of the image sensor 10 is controlled by the electronic shutter control, the driver 9 supplies a necessary timing control signal to the image sensor 10.

  The image sensor 10 is configured by a CMOS image sensor or the like. The image sensor 10 photoelectrically converts a subject image formed on the imaging surface and outputs an image signal. The image processing unit 11 performs predetermined image processing on the image signal read from the image sensor 10 and converted into a digital signal by an A / D conversion unit (not shown). The image processing unit 11 further performs a resizing process for causing the display unit 13 to display a reproduced image based on the image data after the image processing.

  The image storage unit 12 records an image file on a recording medium (not shown) or reads an image file recorded on the recording medium based on an instruction from the control unit 17. The recording medium is constituted by, for example, a memory card that is detachably attached to a card slot (not shown).

  The display unit 13 is composed of a liquid crystal panel. The display unit 13 displays a live view image, a playback image, a menu screen, and the like. Here, the live view image is also called a preview image, and refers to a monitor image acquired by the image sensor 10 at a predetermined frame rate (for example, 60 fps). The photometric calculation unit 15 detects the brightness information (Bv value) of the subject based on the image signal. The exposure control unit 14 determines the aperture value Av, the shutter speed Tv, and the sensitivity Sv based on the Bv value and information on the program diagram stored in the exposure control unit 14. Sensitivity refers to sensitivity at the time of photoelectric conversion in the image sensor 10, and is also referred to as ISO sensitivity.

  The communication unit 16 communicates with the lens communication unit 6 of the photographic lens 100 </ b> B in response to an instruction from the control unit 17. The control unit 17 executes a control program and performs various controls on each unit of the digital camera 100. The drive instruction for the diaphragm 2 is instructed by the control unit 17 via the communication unit 16 based on an operation signal from a command dial (not shown) constituting the operation member 18 or a value determined by the exposure control unit 14.

  The operation member 18 includes a power switch, a shutter button, a mode change switch, a command dial, and the like, and sends an operation signal corresponding to each operation to the control unit 17. The mode switch is a switch for switching between a first mode and a second mode, which will be described later. The command dial is a dial for manually setting an aperture value and a shutter speed.

  In the present embodiment, the first effect of displaying on the display unit 13 the image effect based on the aperture value, shutter speed, and sensitivity automatically determined by the exposure control unit 14 based on the brightness of the subject is reflected in the live view image. The mode and the second mode in which the image effect due to the aperture value and shutter speed set using the command dial constituting the operation member 18 are reflected on the live view image and displayed on the display unit 13 are configured to be switchable. The

<Live view display>
In the present embodiment, the first effect that the image effect based on the aperture value, shutter speed, and sensitivity automatically determined by the exposure control unit 14 based on the brightness of the subject is reflected on the live view image and displayed on the display unit 13. Since the process is characterized by the mode, the following description will be focused on the first mode.

<Description of flowchart>
FIG. 2 is a flowchart for explaining the flow of processing executed by the control unit 17 in the first mode. The control unit 17 activates the process illustrated in FIG. 2 when the setting is switched to the first mode. The program according to FIG. 2 is stored in the nonvolatile memory 17a in the control unit 17.

  In step S1 of FIG. 2, the control unit 17 instructs initialization of the taking lens 100B, and proceeds to step S2. Accordingly, the communication unit 16 communicates with the lens communication unit 6 and transmits an instruction for an initial operation to the lens control unit 5. In the initial operation, for example, the diaphragm 2 is driven to a predetermined opening diameter.

  In step S2, the control unit 17 sends an instruction to the communication unit 16 to acquire lens information from the photographing lens 100B, and the process proceeds to step S3. The lens information includes drive speed information of the diaphragm 2.

  In step S3, the control unit 17 starts displaying the live view image and proceeds to step S4. Accordingly, live view images captured at a predetermined frame rate (for example, 60 fps) by the image sensor 10 are sequentially displayed on the display unit 13.

  In step S4, the control unit 17 causes the photometry calculation unit 15 to perform photometry calculation and proceeds to step S5. Thereby, the photometry calculating unit 15 detects the brightness information (Bv value) of the subject based on the image signal. In step S5, the control unit 17 causes the exposure control unit 14 to perform exposure calculation, and proceeds to step S6. Thereby, the exposure control unit 14 determines the aperture value Av, the shutter speed Tv, and the sensitivity Sv based on the Bv value and the program diagram information. FIG. 3 is a diagram illustrating a program diagram.

  In the program diagram illustrated in FIG. 3, when the minimum aperture stop is F16 (Av = 8) and the maximum aperture stop is F4 (Av = 4), the shutter speed Tv and the aperture Av are approximately shown as the Bv value increases. This represents control that is increased at a ratio of 1: 1.

  In FIG. 3, the sensitivity Sv is changed at shutter speeds of 1/30 seconds and 1/60 seconds. For example, Sv = 8 (equivalent to ISO 800) in the range of Tv <5 (1/30 seconds), and sensitivity Sv is set to 8 (equivalent to ISO 800) to 6 (ISO 200) according to the Bv value at Tv = 5 (1/30 seconds). Equivalent).

  Then, Sv = 6 (equivalent to ISO 200) in the range of 5 (1/30 seconds) <Tv <6 (1/60 seconds), and the sensitivity Sv is set to 6 according to the Bv value at Tv = 6 (1/60 seconds). It is changed between (equivalent to ISO 200) to 5 (equivalent to ISO 100). Further, in the range of Tv> 6 (1/60 seconds), Sv = 5 (equivalent to ISO 100).

  By using the program diagram as described above, when the subject is sufficiently bright (6 <Bv) and shooting is possible at a shutter speed faster than 1/60 seconds, sensitivity equivalent to ISO 100 is used. Further, when the subject brightness is low (Bv <6), for example, by changing the sensitivity Sv higher before changing to a shutter speed slower than Tv = 5 (1/30 seconds), camera shake is less likely to occur.

  Returning to the description of FIG. 2, the control unit 17 determines whether or not there is an Av change in step S <b> 6. If the Av value determined in step S5 is different from the current Av value, the control unit 17 makes a positive determination in step S6 and proceeds to step S7. If the determined Av value is equal to the current Av value, step S6 is performed. A negative determination is made and the process proceeds to step S10. According to the example of FIG. 3, when both the Bv value detected in step S4 and the previously detected Bv value are in the range of 3 to 5, or 6 to 12, it is determined that the Av value has changed. On the other hand, if the Bv value detected in step S4 and the previously detected Bv value are both 3 or less, both 5 to 6 or both 12 or more, it is determined that there is no change in Av value.

  In step S7, the control part 17 determines the presence or absence of Tv or Sv change. When the Tv value or Sv value determined in step S5 is different from the current Tv value or Sv value, the control unit 17 makes an affirmative determination in step S7 and proceeds to step S8, and the determined Tv value and Sv value are If it is equal to the current Tv value and Sv value, a negative determination is made in step S7 and the process proceeds to step S9. In the example of FIG. 3, Tv is changed in both cases where the detected Bv value is in the range of 3 to 5 and in the range of 6 to 12.

  In step S8, the control unit 17 instructs the diaphragm 2 to be driven at high speed, and proceeds to step S10. Thereby, the communication unit 16 communicates with the lens communication unit 6 and sends an instruction to the lens control unit 5 to drive the diaphragm 2 at a high speed to the Av value determined in step S5. High-speed driving uses the upper limit (for example, several milliseconds per 1 Ev) of the driving speed acquired in step S2.

  In step S9, the control unit 17 instructs low speed driving with respect to the diaphragm 2, and proceeds to step S10. Thereby, the communication unit 16 communicates with the lens communication unit 6 and sends an instruction to the lens control unit 5 to drive the diaphragm 2 at a low speed to the Av value determined in step S5. The low speed driving uses, for example, a speed of 1/10 to 1/100 of the speed at the time of the high speed driving.

  In step S10, the control unit 17 determines whether or not there is a Tv change. If the Tv value determined in step S5 is different from the current Tv value, the control unit 17 makes a positive determination in step S10 and proceeds to step S11. If the determined Tv value is equal to the current Tv value, the control unit 17 denies step S10. Determine and proceed to step S12.

  In step S11, the control unit 17 instructs to change the exposure time of the image sensor 10 to the Tv value determined in step S5, and the process proceeds to step S12. Thereby, the driver 9 generates a necessary timing control signal and supplies it to the image sensor 10.

  In step S12, the control part 17 determines the presence or absence of Sv change. If the Sv value determined in step S5 is different from the current Sv value, the control unit 17 makes an affirmative determination in step S12 and proceeds to step S13. If the determined Sv value is equal to the current Sv value, the control unit 17 denies step S12. Determine and proceed to step S14.

  In step S13, the control unit 17 instructs the exposure sensitivity of the image sensor 10 to change to the Sv value determined in step S5, and proceeds to step S14. As a result, the driver 9 outputs a sensitivity control signal to the image sensor 10.

  In step S14, the control unit 17 determines whether or not to end the live view image display. When an operation for stopping the live view display is performed or when the release button is pressed and the photographing process is started, the control unit 17 makes a positive determination in step S14 and ends the process of FIG. On the other hand, if the live view image display is not terminated, the control unit 17 makes a negative determination in step S14 and returns to step S3.

According to the embodiment described above, the following operational effects can be obtained.
(1) The digital camera 100 includes an imaging element 10 that photoelectrically converts a subject image formed by the imaging optical system 1, an aperture value of an aperture 2 that adjusts the amount of light incident on the imaging element 10, an accumulation time of photoelectric conversion, And a control unit 17 that controls the sensitivity of photoelectric conversion, and a control unit 17 that sequentially displays an image based on the photoelectric conversion signal from the image sensor 10 on the display unit 13. Then, the controller 17 changes the aperture value by driving the aperture 2 at the first driving speed when only the aperture value is changed, and the first time when changing at least one of the accumulation time and the sensitivity together with the aperture value. Since the aperture value is changed by driving the aperture 2 at a second driving speed different from the driving speed, flickering of the brightness of the image in the live view display can be reduced.

(2) Since the control unit 17 increases the second drive speed compared to the first drive speed for driving the diaphragm 2 (S8), a time during which the flicker of the brightness of the image is likely to occur occurs. By shortening, the occurrence of the flicker can be reduced.

(3) Since the control unit 17 determines based on the program diagram whether or not to change at least one of the accumulation time and the sensitivity together with the aperture value (S5, S6), based on the detected Bv value. Therefore, the occurrence of flicker can be appropriately reduced.

(4) When changing at least one of the accumulation time and the sensitivity together with the aperture value, the control unit 17 changes the accumulation time and the sensitivity at a time when driving of the aperture 2 is started (S8, S11, S13). Instead of changing the accumulation time and sensitivity in small increments within the drive time of the aperture 2 (the time required to change the aperture value), flickering of the image brightness occurs by changing to the target value at once. The easy time can be shortened and the occurrence of the flicker can be reduced.

(5) Since the controller 17 slows down the drive speed of the diaphragm 2 when changing only the aperture value without changing the accumulation time and sensitivity (S9), the brightness of the image between frames is reduced. The change can be suppressed and changed more smoothly.

(Modification 1)
In the above description, the first mode in which the image effect based on the aperture value, shutter speed, and sensitivity automatically determined by the exposure control unit 14 based on the brightness of the subject is reflected on the live view image and displayed on the display unit 13. In this case, the example in which the driving speed of the diaphragm 2 is switched has been described. In addition to the first mode, also in the second mode in which the image effect due to the aperture value and the shutter speed set using the command dial constituting the operation member 18 is reflected on the live view image and displayed on the display unit 13. The driving speed of the diaphragm 2 may be switched depending on whether or not at least one of the accumulation time and the sensitivity is changed together with the diaphragm value.

(Modification 2)
In the above-described embodiment, when the shutter speed or sensitivity is changed together with the driving of the diaphragm 2, the control unit 17 instructs the change of the shutter speed and the sensitivity after instructing the driving of the diaphragm 2. The instruction to change the shutter speed or sensitivity may be given at any time point, at the start of changing the aperture 2, at the end of changing the aperture 2, or during the change of the aperture 2. Note that the shutter speed and sensitivity are not changed in small increments during the drive time of the diaphragm 2 (time required for changing the aperture value), but changed to the target value at once.

(Modification 3)
In the present embodiment, a camera that combines an interchangeable photographic lens 100B that is detachable from the camera body 100A has been described as an example. Instead, a lens-integrated camera may be used as long as the diaphragm 2 includes an iris diaphragm.

  The above description is merely an example, and is not limited to the configuration of the above embodiment.

DESCRIPTION OF SYMBOLS 1 ... Imaging optical system 2 ... Aperture 10 ... Imaging element 11 ... Image processing part 13 ... Display part 14 ... Exposure control part 17 ... Control part 18 ... Operation member 100 ... Digital camera 100A ... Camera body 100B ... Shooting lens

Claims (4)

An image sensor that photoelectrically converts a subject image formed by the imaging optical system;
An imaging control unit that controls the aperture value of the diaphragm that adjusts the amount of light incident on the imaging device, the accumulation time of the photoelectric conversion, and the sensitivity of the photoelectric conversion;
A display control unit that sequentially displays an image based on a photoelectric conversion signal from the image sensor on a display device;
When changing only the aperture value, the imaging control unit drives the aperture at a first driving speed to change the aperture value, and changes at least one of the accumulation time and the sensitivity together with the aperture value. In this case, the aperture value is changed by driving the aperture at a second drive speed different from the first drive speed. The imaging device according to claim 1,
The imaging apparatus, wherein the imaging control unit increases the second driving speed as compared with the first driving speed for driving the diaphragm. The imaging device according to claim 2,
The imaging apparatus determines whether to change at least one of the accumulation time and the sensitivity together with the aperture value based on a program diagram. In the imaging device according to any one of claims 1 to 3,
When changing at least one of the accumulation time and the sensitivity together with the aperture value, the imaging control unit changes the accumulation time and the sensitivity at a time from the start of driving the aperture to the end of driving. An imaging apparatus characterized by that.

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