JP2017028637A - Photographing device, and control method and program for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute exposure control promptly according to change in brightness while suppressing an exposure follow-up range from narrowing during acquisition of a moving image.SOLUTION: The photographing device comprises photographing means, exposure control means that executes exposure control so that a first parameter and a second parameter relating to the exposure control are changed, and brightness change detecting means that detects change in brightness, where time required for the second parameter to be changed by a predetermined amount of exposure is shorter than time required for the first parameter to be changed by the predetermined amount of exposure. The exposure control means performs control so that the second parameter is changed at one time from a first value to a second value based on changed brightness, in response to the detection of the change in brightness when the second parameter is equal to the first value, then the first parameter is changed to a value based on the changed brightness and the second parameter is gradually changed from the second value to the first value in a period of time during which the first parameter is changed.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an imaging apparatus that acquires a moving image by continuously imaging a subject, a control method thereof, and a program.

  An imaging device that changes exposure during acquisition of a moving image stepwise according to a change in luminance of a subject so that the luminance of the moving image becomes a luminance corresponding to the luminance change of the subject when acquiring a moving image Is proposed in Patent Document 1.

JP 2009-1118012 A

  On the other hand, even when a moving image is acquired, there is a scene where the exposure is desired to be quickly changed so that the moving image has a brightness corresponding to the luminance after the change according to the luminance change of the subject. As the above-described scene, for example, a presentation (image) or the like projected outside may be taken in a presentation or the like. In this case, the brightness of the material changes greatly as the content of the material is quickly switched. Therefore, when capturing an image of a material projected outside, it is desirable to quickly change the exposure according to the change in the brightness of the material so that the content of the material becomes clear.

  However, since the imaging device described in Patent Document 1 changes the exposure in stages, even in the above-described scene, according to the luminance change of the subject, the brightness corresponding to the luminance after the change is obtained. The exposure cannot be changed quickly. Therefore, in the moving image acquired in this case, the content of the material is unclear for a long time.

  In order to solve this problem, it is desirable to execute exposure control by changing a parameter that changes the exposure speed among a plurality of exposure parameters related to exposure control. In other words, it is desirable to execute exposure control by changing a parameter having a short time (hereinafter referred to as exposure change time) required for changing the predetermined exposure among a plurality of exposure parameters.

  However, if exposure control is performed by changing only the exposure parameters with a short exposure change time, the range in which exposure control can be performed following the change in luminance of the subject (hereinafter referred to as exposure tracking range) becomes narrow.

  An object of the present invention is to quickly perform exposure control according to a change in luminance while suppressing a narrowing of the exposure tracking range during acquisition of a moving image.

  The imaging apparatus of the present invention that achieves the above object changes at least one of imaging means for imaging a subject, a first parameter related to exposure control, and a second parameter different from the first parameter. The exposure control means for executing the exposure control as described above and the brightness change detection means for detecting the brightness change of the subject, and the time required to change the second parameter by a predetermined exposure is The first parameter is shorter than the time required to change the predetermined exposure, and the exposure control means is configured to set the second parameter to the first value during acquisition of a moving image using the imaging means. The second parameter is changed from the first value to the second value based on the luminance after the change in response to the luminance change detecting unit detecting a luminance change when the value is a value. Later, said The second parameter is changed from the second value in a period in which the first parameter is changed to a value based on the luminance after the change, and the first parameter is changed to a value based on the luminance after the change. Control is performed such that the first value is changed stepwise.

  ADVANTAGE OF THE INVENTION According to this invention, exposure control can be rapidly performed according to a brightness | luminance change, suppressing that an exposure follow-up range becomes narrow during the acquisition of a moving image.

It is a block diagram explaining the structure of the digital video camcorder 100 which is embodiment of the imaging device which implemented invention. It is a flowchart explaining the process regarding the exposure control at the time of document switching based on 1st Embodiment of this invention. In the exposure control process which concerns on 1st Embodiment of this invention, it is the figure explaining the range which can change a 1st parameter exemplarily. It is a figure explaining the change of the exposure parameter in exposure control processing concerning a 1st embodiment of the present invention exemplarily. In the exposure control process which concerns on 2nd Embodiment of this invention, it is the figure explaining the changeable range and standby state of a 2nd parameter exemplarily. In the exposure control process which concerns on 3rd Embodiment of this invention, it is the figure explaining the changeable range and standby state of a 2nd parameter exemplarily.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

(First embodiment)
(Basic configuration of digital video camcorder 100)
The basic configuration of a digital video camcorder (hereinafter simply referred to as video) 100 will be described below with reference to FIG. FIG. 1 is a block diagram illustrating a configuration of a video 100 that is an embodiment of an imaging apparatus that implements the present invention.

  The imaging lens 101 includes a zoom lens, a focus lens, a shift lens, and the like, and is an imaging lens group that guides an optical image (light beam) of a subject to the imaging element 104 side described later. In FIG. 1, a plurality of lens groups constituting the imaging lens 101 are illustrated as one lens for the sake of explanation.

  The diaphragm 102 is a light amount adjusting member that adjusts the amount of light that passes through the imaging lens 101 and enters the video 100.

  The ND filter 103 is a light reducing unit that reduces the amount of light that passes through the imaging lens 101 and the diaphragm 102 and enters the video 100. The ND filter 103 of this embodiment employs an optical member having a single light transmittance. As the ND filter 103, a plurality of optical members having different transmittances may be operated in cooperation, or one having different transmittances depending on the position in the plane may be employed.

  The image sensor 104 is a charge storage type solid-state image sensor, and is an image pickup unit that generates analog image data by photoelectrically converting a light beam incident through the image pickup lens 101. The image sensor 104 employs a CMOS image sensor in which color filters are arranged in a so-called Bayer array, but may be configured to employ a CCD.

  In the present embodiment, the process up to the generation of the analog image data by the image sensor 104 described above is the imaging of the subject, but the imaging of the subject may be performed until the output of digital image data described later. Note that the video 100 can acquire a moving image based on image data obtained by continuous imaging by continuously imaging a subject using the imaging element 104.

  In the present embodiment, as a mode (imaging mode) for capturing a subject and capturing a moving image (imaging mode), it is suitable for capturing a material (image) projected using an external display device such as a monitor or a screen. You can set the presentation mode to operate. The video 100 of the present embodiment can execute exposure control suitable for the brightness of the material portion in the imaging screen when the imaging mode is set to the presentation mode. Details of this will be described later in the description of the exposure control process.

  The A / D conversion unit 105 is a conversion unit that converts analog image data input from the image sensor 104 into digital image data. The A / D conversion unit 105 adjusts the analog gain amount of the analog image data before conversion to digital image data in accordance with an instruction from the exposure control unit 112 described later.

  The gain control unit 106 is a gain control unit that controls the digital gain amount with respect to the digital image data input from the A / D conversion unit 105 in accordance with an instruction from the exposure control unit 112. Further, the gain control unit 106 controls the gain amount for each color channel according to an instruction from the exposure control unit 112, and adjusts the black level correction and white balance (WB) of the digital image data.

  The signal processing unit 107 is a signal processing unit that performs various processes on the digital image data input from the gain control unit 106. The signal processing unit 107 converts the digital image data into image data for recording suitable for recording on a recording medium (not shown) that can be attached to and detached from the memory 110 and the video 100 described later. The signal processing unit 107 converts the digital image data into analog image data for display suitable for display on the monitor 108 described later.

  The monitor 108 is a display means that employs a TFT type LCD (Thin Film Transistor Driven Liquid Crystal Display), and displays analog image data for display input from the signal processing unit 107. Note that a configuration other than the TFT type LCD may be adopted as the monitor 108.

  The system control unit 109 is a control unit that comprehensively controls the operation of each unit of the video 100. The system control unit 109 includes a memory 110, a CPU 111, an exposure control unit 112, a photometry unit 113, a luminance change detection unit 114, a communication control unit 115, a wireless communication unit 116, and a bus 117.

  The memory 110 is a storage means that can be electrically erased and stored, and is, for example, an EEPROM represented by a flash memory or the like. The memory 110 stores, as various data relating to the operation of the video 100, for example, constants for operations executed in the video 100, various exposure conditions (for example, program diagrams), calculation formulas, and the like. The CPU 111 is a processing unit that executes each operation of the video 100.

  The exposure control unit 112 is an exposure control unit that performs exposure control. When exposure control is executed by the exposure control unit 112, parameters related to exposure control (exposure parameters) are changed. The exposure parameters include an aperture value related to the aperture of the aperture 102, a transmittance of the ND filter 103 (hereinafter simply referred to as transmittance), and an electronic shutter speed (hereinafter simply referred to as shutter speed) regarding the accumulation time of the image sensor 104. And a gain amount. The gain amount includes both an analog gain amount and a digital gain amount. In the present embodiment, control for changing each exposure parameter so as to have a value corresponding to the target exposure is referred to as exposure control.

  The exposure control will be specifically described. The exposure control unit 112 calculates a target exposure based on a photometric value acquired by the photometric unit 113 described later and information stored in the memory 110 in advance. The exposure control unit 112 drives and operates exposure elements such as the diaphragm 102, the ND filter 103, the image sensor 104, the A / D conversion unit 105, and the gain control unit 106 with respect to the calculated exposure, thereby exposing the exposure. Execute control. With this configuration, the exposure parameter corresponding to each exposure element is changed to a value corresponding to the target exposure.

  As described above, in this embodiment, each exposure parameter corresponding to the target exposure described above is set, and exposure elements such as the diaphragm 102 and the ND filter 103 corresponding to each exposure parameter are set so as to reach the exposure parameter. The exposure control is executed by operating.

  In the present embodiment, exposure control is executed so that at least one of the above-described exposure parameters is changed. Specifically, in order to achieve the target exposure, a target value is set for each exposure parameter, and exposure control is executed by changing a predetermined parameter of each exposure parameter toward the target value. .

  Here, the speed of changing the exposure differs depending on the exposure parameter that realizes the change of the exposure. In other words, the time required for changing the exposure by a predetermined amount of exposure (exposure changing time) differs for each exposure parameter. This will be specifically described below.

  The change of the aperture value and the transmittance is mainly performed by the mechanical operation of each part of the video 100 such as the change of the opening of the stop 102 and the insertion / extraction (or position change) of the ND filter 103. On the other hand, the change of the shutter speed and the gain amount is performed mainly by the electrical operation of each part of the video 100 such as the change of the accumulation time of the image sensor 104 and the gain amount applied to the image data. Since the time required to mechanically operate each part of the video 100 is longer than the time required to electrically operate each part of the video 100, the aperture value and the transmittance are determined by the shutter speed and the gain amount. Compared to the exposure parameter, the exposure change time is longer. That is, the time required to change the aperture value and the transmittance is relatively longer than the time required to change the shutter speed and the gain amount. For example, the time required to change the aperture value by one step of exposure is longer than the time required to change the gain amount by one step of exposure.

  In the present embodiment, among the exposure parameters, the aperture value and the light transmittance of the ND filter 103 are referred to as a first parameter. Of the exposure parameters described above, the (electronic) shutter speed and gain amount are referred to as a second parameter. Therefore, in the video 100 of this embodiment, the exposure change time is shorter when the second parameter is changed than when the first parameter is changed.

  Returning to FIG. 1, the photometric unit 113 is a photometric unit that acquires a photometric value based on the image data input from the signal processing unit 107. Specifically, the photometry unit 113 divides the acquired image data into a plurality of regions (blocks), and calculates an (average) luminance value of each block. The luminance value of each block is recorded in the memory 110 in association with the position information of each block on the imaging screen.

  Next, the photometric unit 113 applies preset weighting data for photometry to the calculated luminance value of each block. Then, the photometric unit 113 integrates the luminance value of each block to which weighting is applied to obtain a representative luminance value (photometric value), and outputs the photometric value to the exposure control unit 112 and the memory 110.

  In the present embodiment, the photometric unit 113 is configured to acquire a photometric value based on an input from the image sensor 104, but is configured to acquire based on a signal output from a sensor other than the image sensor 104. Also good. In the present embodiment, the photometric unit 113 is configured to acquire a luminance value for each of a plurality of blocks and calculate a photometric value for each frame when a moving image is acquired.

  The luminance change detection unit 114 is a luminance change detection unit that detects a luminance change of the subject based on the photometry result of the photometry unit 113. Specifically, the luminance change detection unit 114 can detect the luminance change of the subject by comparing changes in luminance values between frames based on the luminance values for each of a plurality of blocks acquired by the photometry unit 113. it can. Details of this will be described later in the description of the method for detecting the luminance change of the subject.

  The communication control unit 115 is a communication control unit that controls communication between the video 100 and an external device. The communication control unit 115 transmits and receives information to and from the external input device 200 when the external input device 200 is connected to a communication connector (not shown) of the video 100. The wireless communication unit 116 is a communication module that performs wireless communication with an external device, and transmits and receives information to and from the external device according to an instruction from the communication control unit 115.

  The bus 117 is a common path inside the video 100. The bus 117 is connected to the signal processing unit 107, the monitor 108, the system control unit 109, the memory 110, the CPU 111, the exposure control unit 112, the photometry unit 113, the luminance change detection unit 114, the communication control unit 115, and the wireless communication unit 116. Yes. The basic configuration of the video 100 has been described above.

(Image capturing operation of the digital video camcorder 100)
Hereinafter, a basic imaging operation of the subject by the video 100 will be described. When the release switch (not shown) is set to the SW1 state (for example, half-pressed) by the user, the exposure control unit 112 controls the driving of the imaging lens 101 and executes AF (Auto Focus) processing.

  Next, the exposure control unit 112 reads a predetermined exposure stored in the memory 110, and operates each part of the video 100 based on the exposure parameter corresponding to the exposure to capture an image of the subject.

  Next, the photometric unit 113 acquires digital image data (hereinafter simply referred to as an image) acquired by imaging from the signal processing unit 107, and acquires a photometric value based on the image.

  Next, the exposure control unit 112 calculates a target exposure based on the previously obtained photometric value in response to the release switch being set to the SW2 state (for example, fully pressed) by the user. Then, the exposure control unit 112 operates each part of the video 100 according to the target exposure to change the exposure parameter. Thereafter, the subject is imaged (main imaging) with the exposure reaching the target exposure by changing the exposure parameter.

  Next, the signal processing unit 107 performs various processes on the image acquired by imaging. Then, the CPU 111 records the image processed by the signal processing unit 107 in the memory 110. Further, the CPU 111 displays an image processed by the signal processing unit 107 on the monitor 108. The video 100 according to the present embodiment can reproduce and acquire a moving image by executing the operation described above for each frame based on a preset frame rate. The above is the imaging operation according to the present embodiment.

  Note that the exposure control of the present embodiment is performed based on a program diagram stored in advance in the memory 110. However, when the imaging mode is set to the presentation mode, the exposure parameter to be preferentially changed is set in advance. It has been decided. With this configuration, the video 100 according to the present embodiment can quickly perform exposure control according to the luminance change of the material portion in the imaging screen. Details of this will be described later in the description of the exposure control process.

(Subject brightness detection method)
Hereinafter, a method of detecting the luminance change of the subject by the luminance change detection unit 114 will be described. Hereinafter, a case will be described in which a luminance change is detected during moving image acquisition when the imaging mode is set to the presentation mode.

  First, the photometry unit 113 acquires a luminance value for each of a plurality of blocks for each frame during moving image acquisition. The luminance value for each frame is recorded in the memory 110.

  Next, the luminance change detection unit 114 reads out information related to the luminance value recorded in the memory 110 and compares the luminance value of the previous frame and the luminance value of the current frame at the same position in the imaging screen. The brightness value comparison is performed for each of a plurality of blocks.

  As a comparison of the luminance values between the frames described above, in this embodiment, the absolute value (luminance difference) of the difference between the luminance value of each block in the previous frame and the luminance value of each block in the current frame is calculated.

  Next, the luminance change detection unit 114 compares the previously calculated luminance difference with a preset threshold value α, and counts the number of blocks whose luminance difference is equal to or greater than the threshold value α. The luminance change detection unit 114 detects (determines) that the luminance of the material portion has changed when the number of counted blocks exceeds a predetermined number N. This detection result is transmitted to the exposure control unit 112.

  Here, the threshold value α and the predetermined number N described above will be described. In the present embodiment, since it is assumed that the imaging mode is set to the presentation mode, there is a high probability that the main subject that the user intends to capture is a material (image) projected outside. In this case, in order to obtain an exposure suitable for the brightness of the material portion in the imaging screen, it is desirable that it is possible to detect that the luminance of the entire material has changed as the luminance change of the subject. Therefore, it is desirable to set the above-described threshold value α and the predetermined number N to values suitable for detecting a change in luminance of the material portion due to the material switching or the animation effect.

  Therefore, in the present embodiment, a luminance difference corresponding to one stage of luminance values is set as the threshold value α described above. Further, as the above-mentioned predetermined number N, the predetermined number N is 30% of the blocks of all the blocks on the imaging screen. For example, when the number of blocks of the entire imaging screen is 100, the predetermined number N = 33. With this configuration, it is possible to effectively detect a change in the brightness of the entire document, not a part of the document, such as a change in the background color or character color of the document, or activation of an animation effect over the entire document.

  The threshold value α is a value that does not blur the contents of the material part in a moving image acquired with an exposure corresponding to the luminance value of the previous frame, at least when the luminance difference is smaller than the threshold value α. Good. Further, as the predetermined number N, any number may be adopted as long as it is an appropriate number as a ratio of the material portion in the entire imaging screen (view angle).

  Note that the above-mentioned one-step luminance value (and photometric value) is the brightness when the exposure parameter is changed and the exposure is changed by one step, and corresponds to 1 Ev in APEX units. Here, for the gain amount, 1 dB is set to 1/6 of the exposure. Then, the gain amount of 0 dB is ISO100 when converted into the photographing sensitivity.

  In this embodiment, a case has been described in which a luminance value is obtained for each frame (photometry of a subject) and a change in luminance of the subject is detected. However, the present invention is not limited to this. For example, in response to receiving information on switching of materials from an external display device displaying the material or a device connected to the display device via the communication control unit 115, the luminance change detection unit 114 may be configured to detect a change in luminance of the subject. That is, a configuration in which a change in luminance of the subject is detected based on information from outside regarding the switching of materials may be employed. In addition, as a device connected to the above-described display device, for example, a PC or a remote controller is assumed. The above is the method for detecting the luminance change of the subject.

(Exposure control processing)
Hereinafter, exposure control during moving image acquisition (imaging) by the video 100 will be described with reference to FIGS.

  As described above, there is a scene in which exposure is desired to be quickly changed according to a change in luminance of a subject during acquisition of a moving image. For example, in the case of recording a material projected outside in a presentation as a moving image, the luminance of the material portion changes instantaneously according to the switching of the material or the activation of the animation effect as the presentation progresses. In this case, it is desirable to change the exposure quickly according to the luminance change of the material portion.

  However, when changing the exposure parameter with a short exposure change time to the limit of the changeable range, the exposure parameter with the short exposure change time is not changed according to the change in the brightness of the material. Is unclear for a long time.

  Therefore, the video 100 according to the present embodiment preferentially sets the exposure parameter having a short exposure change time according to the luminance change of the subject while suppressing the exposure follow-up range of the exposure parameter having a short exposure change range from being narrowed. This can be addressed by making changes.

  The details will be described below with reference to FIG. FIG. 2 is a flowchart for explaining processing related to exposure control at the time of document switching (hereinafter referred to as exposure control processing) according to the first embodiment of the present invention. In the following description, it is assumed that the imaging mode of the video 100 is set to the presentation mode.

  First, when the exposure control process is started in response to the acquisition of an image to be processed in the currently processed frame, in step S201, the photometric unit 113 measures the subject and acquires a photometric value. Then, the exposure control unit 112 calculates a target exposure corresponding to the acquired photometric value. The target photometric value and the target exposure are values for the brightness of the entire imaging screen.

  Next, in step S202, the luminance change detection unit 114 compares the luminance value of the previous frame with the luminance value of the current frame, and detects the luminance change of the subject. The method for detecting the luminance change of the subject is as described above in the description of the luminance change detection unit 114. If the luminance change detection unit 114 does not detect the luminance change of the subject, the exposure control process currently being processed is terminated. When a new image is acquired, the exposure control process is executed based on the newly acquired image.

  Next, in step S203, the exposure control unit 112 performs exposure control so as to change the shutter speed and gain amount (second parameter), which are exposure parameters with a short exposure change time. In the present embodiment, exposure control executed by changing the shutter speed and gain amount with priority is referred to as high-speed AE control.

  Next, in step S204, the exposure control unit 112 determines whether or not the current exposure has reached the previously set target exposure by high-speed AE control. The process of step S204 is repeated until the high speed AE control is completed.

  As described above, in the present embodiment, the above-described high-speed AE control is executed until the target exposure is set after the brightness change of the document is detected. With this configuration, the video 100 according to the present embodiment can reach the target exposure by changing the exposure in as short a time as possible after the luminance change of the material.

  Next, in step S205, the exposure control unit 112 changes the shutter speed or the gain amount (second parameter) so as to approach a value immediately before starting the previous high-speed AE control. Specifically, in the video 100 according to the present embodiment, the shutter speed or the gain amount is changed to a value set immediately before the process of step S203 is executed.

  In step S205, the exposure control unit 112 changes the aperture value or transmittance (first parameter) by an amount corresponding to the change amount of the second parameter. That is, in step S205, the exposure control unit 112 compensates for the difference in exposure caused by changing the second parameter by changing the first parameter. For example, when the second parameter is changed by one step to the bright side in step S205, the first parameter is changed by one step to the dark side.

  In the present embodiment, the exposure control executed in step S205 is referred to as stable AE control. The stable AE control will be specifically described with reference to FIG. FIG. 3 is a diagram exemplarily illustrating a changeable range of the first parameter in the exposure control process according to the first embodiment of the present invention. As shown in FIG. 3, it is assumed that the exposure that can be controlled by changing the shutter speed is 6 steps (6 EV), and the exposure that can be controlled by changing the gain amount is 4 steps (4 EV).

  In this case, as a range in which the exposure can be changed by changing the second parameter, a total of 10 stages (10 Ev) of exposure is secured. Therefore, in this changeable range, the amount by which the shutter speed or gain amount can be changed decreases as the distance from the approximate center (5 Ev) increases.

  For example, assume that in high-speed AE control, the brightness of the document is newly detected after the shutter speed and the gain amount are changed to the position <1> shown in FIG. The gain amount and the shutter speed at the position <1> are suitable for the case where the exposure reaches the limit on the bright side and the luminance of the subject is dark.

  In this case, if the brightness of the subject after the change changes to a darker side than the brightness of the subject immediately before the change, the exposure control cannot be performed by changing the shutter speed and the gain amount. In other words, when the shutter speed and gain amount are changed to near the maximum value of the changeable range by high-speed AE control, the shutter speed and gain amount are changed even if the brightness of the subject newly changes. I can not. In this state, the aperture value and the transmissivity must be changed in response to the newly detected luminance change of the subject, so that the subject's brightness is unnatural for a long time. As in the present embodiment, when an image of an externally projected material is imaged, a state in which the content of the material is unclear continues for a long time.

  Therefore, in step S205, while maintaining the exposure changed by the high speed AE control as much as possible, each exposure parameter is changed so that the range in which the shutter speed and the gain amount can be changed is larger than when the high speed AE control is completed. To control. That is, in the stable AE control, the second parameter changed by the high-speed AE control is controlled so as to be changed to a value that can move the exposure to the maximum on both the bright side and the dark side. The exposure change amount (difference) corresponding to the change in the second parameter is compensated by changing the aperture value and the transmittance (first parameter). Therefore, the changeable range of the second parameter narrowed by executing the high-speed AE control can be widened by executing the stable AE control.

  Here, the direction of luminance change of the subject and the direction of changing each exposure parameter will be described. For example, in response to the fact that the luminance change detection unit 114 has detected that the luminance of the subject has changed to the bright side, the exposure control unit 112 changes the second parameter to the side where the brightness becomes dark. Thereafter, the exposure control unit 112 changes the second parameter again to the side where the brightness becomes brighter, and the first parameter toward the side where the brightness becomes darker so as to compensate for the change of the second parameter. Change the parameters.

  Further, in response to the fact that the luminance change detection unit 114 has detected that the luminance of the subject has changed to the dark side, the exposure control unit 112 changes the second parameter to the side where the brightness becomes brighter. After that, the exposure control unit 112 changes the second parameter again to the side where the brightness becomes darker, and the first parameter toward the side where the brightness becomes brighter so as to compensate for the change of the second parameter. Change the parameters.

  In the stable AE control of the present embodiment, the second parameter is changed during the period in which the first parameter is changed so that the brightness change in the imaging screen due to the exposure control does not increase. Perform exposure control. That is, in the stable AE control, the target exposure is maintained as much as possible by changing the first parameter and the second parameter substantially simultaneously. Specifically, in the stable AE control, in order to execute the exposure control while maintaining the target exposure as much as possible, the second parameter is changed corresponding to the exposure change time of the first parameter.

  For example, in stable AE control, when two frames are required to change the aperture value to the target value, the second parameter is changed stepwise by dividing into two frames. That is, the gain amount or the shutter speed is changed stepwise in accordance with the number of frames required for adjusting the opening of the diaphragm 102.

With the configuration described above, the exposure corresponding to the change in aperture value and transmittance can be compensated relatively slowly by changing the gain amount and shutter speed. It can be suppressed as much as possible. With this configuration,
As described above, the video 100 according to the present embodiment executes the above-described stable AE control until the next change in luminance of the subject is detected after the exposure is changed to the target exposure by the high-speed AE control. With this configuration, it is possible to quickly change the target exposure according to the luminance after the change according to the luminance change of the subject (document), and to suppress a reduction in the changeable range of the exposure parameter with a short exposure change time. . Therefore, the video 100 according to the present embodiment can quickly perform exposure control according to the luminance change while suppressing the exposure follow-up range from being narrowed during moving image acquisition.

  In the present embodiment, the case where the shutter speed and the gain amount are target values in the stable AE control is referred to as a standby state.

  Returning to FIG. 2, in step S206, the exposure control unit 112 determines whether or not the stable AE control has been completed and the shutter speed and the gain amount have changed to values corresponding to the standby state. The process of step S205 is repeated until the stable AE control is completed, and the exposure control process is terminated in response to the completion of the stable AE control.

  The change of each exposure parameter in the exposure control process of the present embodiment described above will be described with reference to FIG. FIG. 4 is a diagram for exemplarily explaining changes in exposure parameters in the exposure control process according to the first embodiment of the present invention, in which the time elapses from left to right in the figure. Is shown. Further, the upper part of FIG. 4 shows the change of the exposure parameter in a diagram, the middle part shows the detailed exposure in each period, and the lower part shows the luminance change of the material part in each period.

  For the sake of explanation, it is assumed in FIG. 4 that the light transmittance of the ND filter 103 is not changed, and the luminance change of the material is caused by the switching of the material. Further, it is assumed that the luminance change of the subject in FIG. 4 is caused by the switching of the material displayed outside.

  As shown in FIG. 4, first, the shutter speed and the gain amount are maintained at values corresponding to the standby state until the luminance change detection unit 114 detects the luminance change of the subject (standby state <1 in FIG. 4). >). In FIG. 4, the shutter speed is 1/120 seconds and the gain amount is 0 dB, which is a value corresponding to the standby state described above.

  Next, when the luminance change of the subject is detected by the luminance change detection unit 114, high-speed AE control is executed, and the gain amount is set to 0 dB (first value) to 6 dB (second value) with respect to the target exposure. Value) at a time (high-speed AE control <1>).

  Next, after reaching the target exposure by high-speed AE control, stable AE control is executed to change the gain amount from 6 dB (second value) to 0 dB (first value) step by step, The aperture value is changed from F5.6 to F8.0 (stable AE control <1>). That is, the exposure control is executed so as to change the gain amount during the aperture value change period. By the stable AE control, the shutter speed and the gain amount are changed to values corresponding to the standby state (standby state <2>).

  Note that during the stable AE control of this embodiment, an image is acquired for each new frame and the luminance value of the subject is acquired, but the exposure control process is not newly started until the exposure control process currently being processed is completed. It is a configuration.

  In addition, when a change in luminance of the subject is detected based on a newly acquired image during the stable AE control, the current stable AE control is continuously executed, and an aperture value as a target value for the stable AE control is set. Respond by changing the priority. With this configuration, it is possible to set the exposure corresponding to the newly detected brightness value without narrowing the exposure follow-up range. In the case described above, the stable AE control is continuously executed in the scene where the luminance of the subject changes instantaneously, after the change in the luminance of the subject is detected once, the subject is again detected within the frame required for the stable AE control. This is because the probability that a change in luminance is detected is low.

  Next, when the luminance change detection unit 114 newly detects a luminance change of the subject after completion of the previous stable AE control, the high-speed AE control is executed again. As the high-speed AE control, the shutter speed is changed from 1/120 seconds (first value) to 1/240 seconds (second value) at a time with respect to the target exposure (high-speed AE control <2>). .

  Note that the high-speed AE control of the present embodiment executes exposure control by giving priority to changing the shutter speed when the luminance value of the subject changes to the bright side so that the gain amount in the standby state becomes 0 dB. To do. With this configuration, it is possible to suppress an increase in the noise component of the acquired image in the standby state.

  Next, after reaching the target exposure by the high-speed AE control, the stable AE control is executed, and the shutter speed is stepped from 1/240 second (second value) to 1/120 second (first value). At the same time, the aperture value is changed from F8.0 to F5.6 (stable AE control <2>). Then, by the stable AE control, the shutter speed and the gain amount are changed to values corresponding to the standby state (standby state <3>). The exposure control processing related to the video 100 of the present embodiment has been described above.

  As described above, the video 100 according to the present embodiment changes the exposure parameter (second parameter) whose exposure change time is short until the target exposure is first reached after detecting the luminance change of the subject. Then, exposure control is executed. The first and second parameters are increased so that the changeable range of the previously changed second parameter is increased from the time when the target exposure is first reached until the next change in brightness of the material is detected. Execute exposure control to change

  With this configuration, it is possible to quickly change the target exposure according to the brightness of the subject after the change according to the change in the brightness of the subject, and to suppress a reduction in the range in which the exposure parameter can be changed with a short exposure change time. Can do. Therefore, the video 100 according to the present embodiment can quickly perform exposure control according to the luminance change while suppressing the exposure follow-up range from being narrowed during moving image acquisition.

(Second Embodiment)
In the present embodiment, in the exposure control process when the presentation mode is set, the exposure control process that suppresses the deterioration of the image quality of the image (or moving image) acquired by capturing the subject due to the influence of noise. explain. Note that the basic configuration and imaging operation of the digital video camcorder (hereinafter simply referred to as video) 100 and the method for detecting the luminance change of the subject are the same as those in the first embodiment described above, and thus the description thereof is omitted. In the present embodiment, only the difference from the first embodiment will be described regarding the exposure control process.

  FIG. 5 is a diagram exemplarily illustrating a changeable range of the second parameter and a standby state in the exposure control process according to the second embodiment of the present invention. The range in which the second parameter can be changed is the same as in the first embodiment described above.

  As shown in FIG. 5, when it is assumed that the changeable range of the second parameter is 10 steps, the shutter speed is set to 1/240 seconds and the gain amount is set to 0 dB as a value corresponding to the standby state. To do. That is, in the present embodiment, the shutter speed and the target value of the gain amount corresponding to the standby state are set so that the exposure control is executed without changing the gain amount as much as possible in accordance with the luminance change of the subject. In other words, in the present embodiment, exposure that allows the shutter speed to be preferentially changed in accordance with the luminance change of the subject is set as the value of each exposure parameter corresponding to the standby state. For example, in this embodiment, the exposure that can change the shutter speed by ± 2 steps or more on both the bright side and the dark side is set as a value corresponding to the standby state.

  With this configuration, the video 100 according to the present embodiment can change the shutter speed with priority according to the detection of the luminance change of the subject, thereby suppressing an increase in noise caused by the change in the gain amount. However, exposure control can be executed in a short time. Therefore, the video 100 according to the present embodiment can quickly perform exposure control according to the luminance change while suppressing the exposure follow-up range from being narrowed during moving image acquisition. Furthermore, the video 100 according to the present embodiment can execute exposure control in a short time while suppressing a decrease in image quality such as an increase in noise caused by a change in gain amount in response to detecting a change in luminance of the subject.

  Note that when the subject is imaged with the video 100 fixed on a tripod, desk, or the like, there is a low probability that the quality of the image will be degraded due to a camera shake of the user. Accordingly, when the video 100 is fixed to a tripod or a desk and the subject is imaged, the above-described exposure control process may be preferentially executed.

(Third embodiment)
In the present embodiment, in the exposure control process when the presentation mode is set, the exposure control process for suppressing the image quality of an image (or moving image) acquired by capturing an image of the subject from being deteriorated due to blurring. explain. Note that the basic configuration and imaging operation of the digital video camcorder (hereinafter simply referred to as video) 100 and the method for detecting the luminance change of the subject are the same as those in the first embodiment described above, and thus the description thereof is omitted. In the present embodiment, only the difference from the first embodiment will be described regarding the exposure control process.

  FIG. 6 is a diagram illustratively showing a changeable range of the second parameter and a standby state in the exposure control process according to the third embodiment of the present invention. As shown in FIG. 6, when it is assumed that the range in which the gain amount can be changed is 4 stages (4 Ev) as the second parameter, the shutter speed is fixed at 1/120 seconds and the gain amount is 12 dB. Set to. That is, the video 100 according to the present embodiment executes the high-speed AE control so as to change only the gain amount without changing the shutter speed in accordance with the luminance change of the subject.

  With this configuration, the shutter speed is a fixed value as the target value for each exposure parameter in the standby state, and the gain amount is a value that can be changed to the maximum on both the bright side and the dark side. Can do.

  Therefore, the video 100 according to the present embodiment can change only the gain amount while fixing the shutter speed that is not easily affected by the blur according to the luminance change of the subject, thereby suppressing the deterioration of the image quality caused by the blur. However, exposure control can be executed in a short time. That is, the video 100 according to the present embodiment can quickly perform exposure control according to a change in luminance while suppressing the exposure tracking range from being narrowed during moving image acquisition. Furthermore, the video 100 according to the present embodiment can execute exposure control in a short time while suppressing a decrease in image quality due to an external factor such as a user's camera shake in response to detection of a change in luminance of the document.

  Note that the above-described exposure control is preferably executed preferentially when the user holds the video 100 and the influence of camera shake by the user is relatively large.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these, A various deformation | transformation and change are possible within the range of the summary. For example, a gyro sensor, an acceleration sensor, or the like is provided in the video 100, and a CPU (blur detection unit) 111 detects the blur amount of the video 100 based on the output of the sensor. And the structure which selectively performs the exposure control process demonstrated in 2nd Embodiment and 3rd Embodiment mentioned above based on the result of the blur detection by CPU111 may be sufficient. Moreover, the structure which selectively performs the exposure control process demonstrated in 2nd Embodiment and 3rd Embodiment according to the operation input by a user may be sufficient.

  In the embodiment described above, either the shutter speed or the gain amount is changed in the high-speed AE control and the stable AE control. However, the shutter speed and the gain amount are changed at the same time. Also good. Further, in the above-described embodiment, in the stable AE control, either the aperture value or the light transmittance of the ND filter is changed. However, the aperture value and the light transmittance of the ND filter are simultaneously changed. Such a configuration may be adopted.

  In the above-described embodiment, the case where the ND filter 103 is an optical member that can switch the insertion / extraction in the optical path connecting the imaging lens 101 and the imaging element 104 or can change the position in the optical path is described. However, the present invention is not limited to this. For example, the ND filter 103 may be configured to control the transmittance of each element by controlling the voltage applied to the physical property element. In this case, the exposure control executed by changing the light transmittance of the ND filter 103 may be controlled mainly by the electrical operation of each part of the video 100. In this case, the light transmittance of the ND filter 103 corresponds to the second parameter described above.

  In the above-described embodiment, the case where the presentation mode is set as the imaging mode has been described, but the imaging mode that can be set in the video 100 is not limited to this. The imaging apparatus of each embodiment described above may be configured to execute the exposure control process illustrated in FIG. 2 when imaging a material projected outside.

  In the above-described embodiment, the exposure control process is executed when the imaging mode is set to the presentation mode. However, the present invention is not limited to this. For example, in the scene where the brightness of the subject changes abruptly, such as a stage or musical that includes sudden lighting and darkening of a spotlight, etc., and it is desired to perform exposure control promptly according to the brightness change, the exposure control described above It may be configured to execute the processing. The scene may be automatically determined by the CPU 111 or may be set based on a user's manual operation. The video 100 according to the present embodiment executes the above-described exposure control at least when the luminance of the subject changes abruptly during the acquisition of a moving image and it is desired to execute the exposure control promptly according to the luminance change. Any configuration can be used.

  In the above-described embodiment, the system control unit 109, the exposure control unit 112, the photometry unit 113, the luminance change detection unit 114, and the like operate in cooperation with each other to control the operation of the video 100. However, the present invention is not limited to this. For example, a configuration may be adopted in which a program according to the flow illustrated in FIG. 2 is stored in the memory 110 in advance, and the operation of the camera is controlled by the CPU 111 or the like executing the program. Note that the CPU 111 executes the operation of each control unit and processing unit without providing the signal processing unit 107, the system control unit 109, the exposure control unit 112, the photometry unit 113, the luminance change detection unit 114, the communication control unit 115, and the like. Such a configuration may be adopted.

  Moreover, as long as it has the function of a program, it does not ask | require the form of programs, such as an object code, the program run by an interpreter, and the script data supplied to OS. The recording medium for supplying the program may be, for example, a magnetic recording medium such as a hard disk or a magnetic tape, or an optical / magneto-optical recording medium.

  In the above-described embodiment, a digital video camcorder has been described as an example of an imaging apparatus that implements the present invention. However, the present invention is not limited to this. For example, the present invention can be applied to various imaging devices within the scope of the gist such as a portable device such as a digital camera or a smartphone.

(Other embodiments)
In addition, the present invention supplies a program that realizes one or more functions of the above-described embodiment to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read the program. It can also be realized by executing processing. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

DESCRIPTION OF SYMBOLS 100 Digital video camcorder 104 Image pick-up element 109 System control part 112 Exposure control part 113 Photometry part 114 Brightness change detection part

Claims (12)

Imaging means for imaging a subject;
Exposure control means for performing exposure control so as to change at least one of a first parameter related to exposure control and a second parameter different from the first parameter;
A luminance change detecting means for detecting a luminance change of the subject;
Have
The time required to change the second parameter by the predetermined exposure is shorter than the time required to change the first parameter by the predetermined exposure,
The exposure control means, during the acquisition of a moving image using the imaging means, in response to the brightness change detection means detecting a brightness change when the second parameter is a first value, After changing the second parameter from the first value to the second value based on the luminance after the change, the first parameter is changed to a value based on the luminance after the change, The second parameter is controlled to be changed stepwise from the second value to the first value in a period in which the first parameter is changed to a value based on the luminance after the change. An imaging device. Each of the first parameter and the second parameter has a changeable range set in advance,
The first value of the second parameter has a wider range in which exposure can be changed to both a bright side and a dark side than the second value of the second parameter. The imaging apparatus according to 1.   The exposure control means, during the acquisition of a moving image using the imaging means, in response to the brightness change detection means detecting a brightness change when the second parameter is the first value, The imaging apparatus according to claim 2, wherein only the second parameter is controlled to change until the second parameter changes from the first value to the second value.   The exposure control means, during the acquisition of a moving image using the imaging means, in response to the brightness change detection means detecting a brightness change when the second parameter is the first value, After the second parameter is changed to the second value, the first parameter is changed so as to compensate for an exposure corresponding to a difference between the first value and the second value. The imaging apparatus according to claim 1, wherein the imaging apparatus is controlled as follows. The first parameter is a parameter related to exposure control mainly composed of mechanical operations of the respective parts constituting the imaging apparatus,
5. The image pickup apparatus according to claim 1, wherein the second parameter is a parameter related to exposure control mainly including an electrical operation of each unit included in the image pickup apparatus.   The first parameter includes at least one of an aperture value related to exposure control mainly related to mechanical operation and light transmittance of an ND filter related to exposure control mainly related to mechanical operation. The imaging apparatus according to claim 5, wherein   The second parameter includes an electronic shutter speed related to exposure control mainly in electrical operation, a gain amount related to exposure control mainly in electrical operation, and exposure control mainly in electrical operation. The imaging apparatus according to claim 5, wherein the imaging apparatus includes at least one of light transmittances of ND filters related to the ND filter. The second parameter includes an electronic shutter speed and a gain amount,
The exposure control means gives priority to the shutter speed when the brightness change detection means detects a brightness change that requires the exposure to be changed to a brighter side before the brightness change detection means detects the brightness change. The imaging apparatus according to claim 7, wherein the imaging apparatus is changed.   The brightness change detecting means detects a change in brightness in response to detecting a change of the material when a moving image is acquired by continuously capturing the material projected outside. The imaging device according to any one of claims 1 to 8.   The brightness change detecting means detects the switching of the material based on information from the external device or a device connected to the external device when imaging the material projected outside by the external device. The imaging apparatus according to claim 1, wherein a change in luminance is detected in accordance with. A method for controlling an imaging apparatus including an imaging means for imaging a subject,
An exposure control step of performing exposure control so as to change at least one of the first parameter relating to exposure control and a second parameter different from the first parameter;
A detection process for detecting a change in luminance of the subject;
Have
The time required to change the second parameter by the predetermined exposure is shorter than the time required to change the first parameter by the predetermined exposure,
In the exposure control step, during the acquisition of a moving image using the imaging unit, the second parameter is detected in response to detecting a luminance change in the detection step when the second parameter is a first value. The first parameter is changed from the first value to the second value based on the luminance after the change, and then the first parameter is changed to a value based on the luminance after the change. The second parameter is controlled to be changed stepwise from the second value to the first value in a period in which the parameter is changed to a value based on the luminance after the change. Control method of imaging apparatus.   A computer-readable program for causing a computer to execute the control method of the imaging apparatus according to claim 11.

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