JP4673245B2 - Imaging apparatus and control method thereof - Google Patents

Description

  The present invention relates to an imaging apparatus capable of recording a still image during moving image recording and a control method thereof.

  In recent years, digital video cameras with a still image shooting function and digital still cameras with a moving image shooting function have been developed due to technological progress of image pickup devices using individual image pickup devices such as CCDs and the increase in capacity and price of semiconductor memory cards. It is common.

  In addition, the movie shooting mode and still image shooting mode can be selected, and not only the movie or still image can be shot in the selected mode, but still image shooting can be performed without switching the mode during movie shooting. Possible imaging devices have also appeared.

  However, since normal movie shooting requires a processing speed of 30 frames / second and it is not assumed that individual frame images are viewed as still images, shooting is performed at a lower resolution than during still image shooting. It is common. In addition, autofocus control is performed with emphasis on the ability to follow a moving subject rather than the focusing accuracy.

  For this reason, when shooting a still image during movie shooting, if the same autofocus control as that used during movie shooting is applied, the image will often be out of focus. It is preferable to perform control.

  When the still image shooting process is performed during moving image shooting, it is difficult to execute the two processes completely in parallel, and the moving image recording is actually interrupted. Therefore, conventionally, proposals have been made to shorten the interruption time of moving image recording by still image shooting processing as much as possible, or to generate an image from another frame for the interruption period to suppress unnaturalness during reproduction.

  For example, Patent Document 1 proposes a technique for reducing the interruption time of moving image recording. Specifically, even if the shutter button for still image shooting is pressed halfway and autofocus control or automatic exposure control is executed, video recording will continue until the shutter button is finally fully pressed. It is.

Japanese Patent Laying-Open No. 2004-201282 (fourth embodiment, paragraphs 0120 to 0130)

  According to the method proposed in Patent Document 1, since video recording is not interrupted until actual shooting is performed, the video recording interruption time is shortened compared to the case where video recording is interrupted immediately when the shutter button is half-pressed. can do. However, there is a problem that autofocus (AF) control and automatic exposure (AE) control performed for still image shooting when the shutter button is half-pressed affects the continuously recorded moving image.

  That is, in AF control during still image shooting, the focus lens generally determines the in-focus position while scanning the entire area between the near end side and the far end side. Therefore, an image obtained during driving of the focus lens accompanying this AF control is included in the continuously recorded moving image. Therefore, when the photographer determines the desired shooting position and shooting range by repeatedly pressing and releasing the shutter button many times, a moving image that is out of focus is recorded each time the shutter button is pressed halfway. As a result, there was a problem that it was unsightly during playback.

  The present invention has been made in view of the above-described problems of the prior art. In an imaging apparatus capable of recording a still image during moving image recording and a control method thereof, the interruption time of moving image recording accompanying still image recording is shortened. An object of the present invention is to provide an imaging apparatus capable of suppressing the influence of still image recording AF control on a moving image and a control method therefor.

The purpose of this is an imaging device having a still image recording function during moving image recording, and when still image recording preparation processing start instruction is detected during moving image recording, still image recording automatic exposure is continued. An automatic exposure control means for performing a control process, an autofocus control means for performing an autofocus control process for recording a still image when a moving image recording is continued when an instruction for starting a still image recording process is given during the moving image recording, Still image recording means for performing still image recording processing based on automatic exposure control processing for still image recording and autofocus control processing for still image recording when there is an instruction to start still image recording processing after instruction to start image recording preparation processing has the door, the automatic exposure control means, still image recording for automatic exposure aperture value that has been used in the video recording when there is a preparation process start instruction for still image recording as the minimum diaphragm value It is achieved by an imaging device and performs control.

In addition, the above-described object is a method for controlling an image pickup apparatus having a still image recording function during moving image recording. When there is an instruction to start a still image recording preparation process during moving image recording, Auto exposure control step that performs automatic exposure control processing for image recording, and autofocus that performs autofocus control processing for still image recording while continuing video recording when there is an instruction to start still image recording processing during video recording If there is an instruction to start the still image recording process after the control step and the still image recording preparation process start instruction, the still image recording process is performed based on the still image recording automatic exposure control process and the still image recording autofocus control process. performed and a still image recording step, the automatic exposure control step, the minimum aperture value that has been used in the video recording when there is a preparation process start instruction for still image recording Also achieved by a control method of an imaging device and performs still image recording automatic exposure control as Values.

  With such a configuration, according to the present invention, it is possible to reduce the interruption time of moving image recording accompanying still image recording and to suppress the influence of AF control for still image recording on the moving image.

Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the drawings.
FIG. 2 is a block diagram illustrating a configuration example of a digital still camera as an imaging apparatus according to an embodiment of the present invention. In FIG. 2, only the configuration related to the still image recording process during moving image recording is shown among the configurations of the digital still camera.

  In the figure, 100 is a lens, 101 is a driving motor for the lens 100, 102 is a lens driving unit for controlling the driving motor 101, 103 is a diaphragm, 104 is a control motor for the diaphragm 103, and 105 is for controlling the driving motor 103. A diaphragm control unit. The image sensor driving unit 111 controls an electronic shutter that controls the charge accumulation time in the image sensor 110 such as a CCD sensor or a CMOS sensor. The image sensor 110 is controlled in accordance with various drive modes such as a still image shooting mode, a moving image shooting mode, and a moving image display mode such as an electronic viewfinder (EVF). Note that the actual state of the moving image shooting mode and the moving image display mode may be the same depending on the form of signal processing performed in the image sensor 110 and the subsequent stage.

  Reference numeral 112 denotes a signal amplification circuit such as AGC that changes the gain of a signal output from the image sensor, and reference numeral 113 denotes a signal processing unit that performs A / D conversion, white balance processing, color generation processing, compression coding processing, and the like. The image display unit 114 typically includes a flat color display device such as an LCD or an organic EL display, and displays the image processed by the signal processing unit 113. The image display unit 114 is used as an electronic viewfinder (EVF), a display during reproduction, and a GUI display for various settings. The CPU 130 controls the entire camera by executing a control program stored in, for example, the memory 140, the recording device 141, or a nonvolatile memory (not shown).

  The operation control during recording, which will be described later, is also realized by the CPU 130 as a main body and controlling other components. Note that at least a part of the signal processing unit 113 may be realized by a combination of the CPU 130 and control software.

  SW1 (120) and SW2 (121) are switches that are turned on / off when the shutter button is pressed. In this embodiment, SW1 (120) is turned on when the shutter button is half-pressed, and SW2 (121) is turned on when the shutter button is fully pressed. Shall. Then, turning on SW1 (120) is used as a still image recording preparation process start instruction, and turning on SW2 (121) is used as a still picture recording process start instruction.

  The memory 140 is, for example, a RAM, and temporarily stores various data and moving images and still images processed by the signal processing unit 113. At least a part of the memory 140 may be a nonvolatile RAM. The memory 140 is also used as a work area for the CPU 130.

  The storage device 141 is a hard disk drive, an optical disk drive, a semiconductor memory card reader / writer, or the like, and can take a form using a storage medium that can be detached from the camera, a form built in the main body, or a combination of these. Further, it may be a form such as a communication card that outputs data to an external device capable of storing data without storing itself.

  The operation unit 142 allows the user to make various instructions and settings for the camera, such as buttons for instructing start and stop of moving image recording, a zoom lever (when the lens 100 is a zoom lens), a cursor key, and a selection / execution key. Including the key. The shutter button also constitutes a part of the operation unit 142.

  In the camera having such a configuration, light that has passed through the lens 100 is converted into an electric signal by the image sensor 110 and is input to the signal processing unit 113 via the signal amplifier circuit 112. The signal processing unit 113 extracts data such as the luminance signal, color signal, and sharpness of the image signal, and based on these, automatic exposure (AE) control, automatic white balance (AWB) control, and autofocus (AF) are extracted. Take control.

The exposure control is performed from the CPU 130.
First, in terms of aperture control, the CPU 130 gives an aperture value (hereinafter referred to as Av) to the aperture controller 105, whereby the aperture controller 105 controls the drive motor 104 and opens and closes the aperture 103 according to the aperture value.

  Control of the electronic shutter speed is realized by giving an electronic shutter speed (hereinafter referred to as Tv) from the CPU 130 to the image sensor control unit 111, and the image sensor control unit 111 controls the electronic shutter speed. By changing the electronic shutter speed, the amount of charge accumulated in the image sensor 110 is controlled.

  The gain of the signal amplification circuit 112 is controlled by giving a gain amount (hereinafter referred to as Gain) from the CPU 130. Recently, there are many cases where the signal amplifier circuit 112 includes an AD converter. In this case, AD conversion is performed not by the signal processing unit 113 but by the signal amplifier circuit 112.

  In the auto focus control, the signal input to the signal processing unit 113 is measured while the position of the focus lens included in the lens 100 is moved within a predetermined range by the lens control unit 102 and the lens driving motor 101. Then, the lens position where the high frequency component of the luminance signal obtained from the image sensor 110 is maximized is searched as the in-focus position.

  Further, the automatic exposure control extracts a luminance level signal indicating the luminance signal level at that time from the image signal input to the signal processing unit 113, and stops the aperture, shutter speed, and so on so that the luminance level signal becomes a predetermined value. This is done by controlling the gain.

Based on the signal from the image sensor 107, the signal processing unit 113 generates color image data, and continuously displays the color image on the image processing unit 114, thereby causing the image display unit 114 to function as an electronic viewfinder. In addition, the signal processing unit 113 compresses and encodes a color image, or converts the color image into a format suitable for video output and outputs it.
The compression-coded image is temporarily stored in the memory 140 and then written in the storage device 141.

  When the number of pixels of the image sensor 110 or the amount of image data generated by the image processing unit 113 is large, a memory (not shown) built in the signal processing unit 113 or a memory built in the CPU 130 (see FIG. (Not shown). In addition, the signal processing speed may be adjusted and output directly to the storage device 141 or the image display unit 114 without using the memory 140.

(Movie recording process)
Next, the moving image recording process in the camera of the present embodiment will be described using the flowchart shown in FIG.
First, for example, moving image recording is started in response to a moving image recording start instruction from the operation unit 142 (S100).

Next, it is detected whether or not a moving image stop operation has been performed (S101). If a stop operation is detected, moving image recording is terminated.
In addition, during the moving image recording, it is checked whether the shutter button is half-pressed by the state of SW1 (120) (S102). If SW1 (120) is turned on, the process proceeds to S200 and the still image recording preparation is started. Otherwise, the process returns to S101.

When SW1 (120) is detected to be on, still image recording AF control processing is performed while moving image recording continues (S300).
In the AF control process for still image recording during moving image recording, focus detection is performed in a narrower scan range (subject distance range) than AF control performed in the normal still image recording mode. As described above, in the normal still image recording mode, a full scan for driving the focus lens is performed over the entire range from the nearest end to infinity. In contrast, in the present embodiment, when the shutter button is pressed halfway during moving image recording to perform still image recording AF control, the focus lens is driven in a narrower range than in the normal still image recording mode.

  As a result, the time for recording an out-of-focus image can be shortened compared to the case of performing a full scan, and the influence on a continuously recorded moving image can be suppressed. In principle, the effect of the present invention can be achieved by driving in a range narrower than the focus lens drive range in the normal still image recording mode, but more specific examples of control contents will be described.

  A first example of the still image recording AF process during moving image recording in step S300 will be further described with reference to the flowchart shown in FIG.

  First, autofocus control during moving image recording will be described. Autofocus control during moving image recording is roughly divided into a micro-drive AF mode, a hill-climbing AF mode, and a lens stop.

  In the micro drive AF mode, the focus lens is moved by a small distance, and the AF evaluation value at the current position and the current position are compared, thereby determining the focus, determining the direction of the focus position, and adjusting the focus over a short distance. Is an operation mode in which

  Specifically, as a result of comparing the AF evaluation values before and after the movement of the focus lens, if the AF evaluation value is increased, it is driven in the same direction. This mode repeats the adjustment. If it has moved continuously a predetermined number of times in the same direction, it is considered that the distance has changed significantly due to the reason that the subject has moved, etc., and the hill-climbing AF mode is entered.

  On the other hand, when reversal (wobbling) is repeated in an area (within a predetermined depth of focus for moving images) that can be regarded as the same for a predetermined time, it is determined that the subject is in focus and the AF evaluation value peak position is reached. Move the focus lens to make a lens stop.

  Assume that SW1 (120) is turned on when such autofocus control is being performed during moving image recording. Then, the CPU 130 acquires the value Av of the aperture 103, the zoom position (lens focal length f) of the lens 100, and the focus lens position from the aperture control unit 105 and the lens control unit 102 when the SW1 is turned on.

  Then, the depth of focus under the current shooting conditions is calculated from the aperture value Av and the diameter of a predetermined minimum circle of confusion δ at the time of moving image recording (S302). Then, still image AF control is performed using the current focus lens position as a reference and the calculated focus depth within the focus lens drive range (S303).

  Since the image is observed as being in focus within the focal depth range, even if AF control is performed with the focus lens driven within this range, the moving image being recorded is not affected. As described above, if the focus lens drive range in the still image recording AF during moving image recording is within the focusing depth at the time of moving image recording, the influence of the AF processing for still image recording during moving image recording on the moving image being recorded is theoretically It will not exist above.

  Alternatively, in S303, a range of ± focus depth can be set with the current focus lens position as a reference. In this case, the focus lens is driven to a portion slightly out of the current depth of focus. However, since it is an AF control in the vicinity that is still sufficiently narrower than full scan and is currently considered in focus in moving image shooting, the effect on the moving image being recorded can be substantially ignored. It is only a degree.

  The focus lens drive range in S303 can be appropriately determined according to the resolution of the moving image and the still image, etc., to what extent the influence on the moving image is allowed in a range narrower than the full scan.

Thus, in this embodiment,
The AF scan range is set such that AF scan range in still image mode> AF scan range for still image recording during moving image recording> AF scan range in moving image mode.

  Returning to FIG. 1, in S103, when SW1 (120) is turned off before SW2 (121) is turned on (when the shutter button is returned to the original state), the process returns to S101. If SW1 (120) is still on, it is checked whether the shutter button is fully pressed (whether SW2 (121) is on) (S104). If SW2 (121) is not turned on, the process returns to S103.

  On the other hand, when SW2 (121) is turned on, moving image recording is interrupted (S105), and the drive mode of the image sensor is switched to the still image recording mode (S106). Then, still image recording settings such as exposure change and focus position fine adjustment for still image recording are performed (S107). Depending on the imaging device, the order of S106 and S107 may be reversed.

  Thereafter, a still image recording process is performed (S108), and after reading an exposure image from the image sensor, the drive mode of the image sensor is returned to the moving image mode (S109), and moving image recording is resumed (S110).

The relationship between the shutter button state and the recording operation of the camera in this embodiment will be described with reference to FIGS.
In order to clarify the difference in operation when the same shutter button operation is performed, the operation in the conventional camera that interrupts the moving image recording each time SW1 (120) is turned on (FIG. 3) and the camera according to the present embodiment Operation (FIG. 4) is shown.

  In the conventional camera shown in FIG. 3, moving image recording is stopped when SW1 is turned on, and thereafter, still image recording AF control is performed and, for example, EVF display is performed until SW2 is turned on. Thereafter, when SW2 is turned on, still image shooting and recording processing is performed. When SW2 is turned off and then SW1 is turned off, moving image recording is resumed. As described above, the moving image recording is stopped after SW1 is turned on until SW1 is turned off.

  On the other hand, in the present embodiment, when SW1 is turned on, still image recording AF processing is performed during moving image recording. However, since moving image recording is not interrupted until SW2 is turned on, the interruption period of moving image recording is greatly reduced. You can see that.

  Further, the operation when SW1 is repeatedly turned on and off is shown in FIGS. FIG. 5 shows a case where the same control as in FIG. 3 is performed, and FIG. 6 shows a case where the control according to the present embodiment is performed.

  In the conventional example shown in FIG. 5, when SW1 is turned on, moving image recording is stopped, AF processing for still images is performed, EVF display is performed, and a standby state for still image shooting is entered. If SW1 is turned off without turning on SW2, the moving image recording is resumed. After that, since SW1 is turned on again, the same processing is performed to enter a still image shooting standby state. As described above, when the actual shooting is not performed and the shutter button is half-pressed and released repeatedly, a moving image with poor continuity is recorded.

  On the other hand, in this embodiment, as shown in FIG. 6, since the moving image recording is not stopped until SW2 is turned on, the moving image recording does not stop.

  As described above, according to the present embodiment, in an imaging device capable of recording a still image during moving image recording, moving image recording is continued in parallel during autofocus control for still image recording during moving image recording. , Interruption of video recording can be made as short as possible. In addition, the focus lens drive range in autofocus control for still image recording during moving image recording is narrower than the focus lens drive range in autofocus control performed during normal still image recording. For this reason, it becomes possible to suppress the influence on the moving image recorded in parallel.

<AE processing>
Next, the still image recording AE process during moving image recording will be described.
FIG. 7 is a flowchart for explaining the moving image recording process of the camera according to the present embodiment. Steps that perform the same processing as in FIG. 1 are given the same reference numerals, and descriptions thereof are omitted. This is different from FIG. 1 in that the still image recording AE process during moving image recording (S200) is performed before the still image recording AF process during moving image recording. Note that, depending on the shooting sequence, it may be performed after the still image recording AF during moving image recording or in parallel.

FIG. 9 is a flowchart illustrating details of the AE process performed in S200 of FIG.
First, the CPU 130 acquires the current aperture value Av from the aperture controller 105. Then, this aperture value Av is set and stored as the minimum aperture value in the AE process performed thereafter (S201).

  Next, a limit shutter speed Tv is obtained (S202), and a program diagram as an exposure program is rearranged from the relationship between the minimum aperture value Av and the limit shutter speed Tv (S203). Thus, control is performed so that the aperture is not opened more than when SW1 is pressed. Then, exposure control is performed using the rearranged program diagram (S204). Here, the exposure program is a program that defines the values of parameters for controlling exposure such as aperture value, shutter speed, and gain in accordance with the photometric value.

As described above, according to the present embodiment, the AE control is performed so that the aperture does not move to the open side from the current value in the AE process for still image recording during moving image recording. Therefore, the depth of focus does not become shallow, and the possibility that the still image recording AF process during moving image recording affects the moving image can be reduced.
Further, by performing the above-described AF control and AE control in parallel, even if there is still image recording during moving image recording, both moving image recording and still image recording can be performed appropriately.

(Other embodiments)
Note that a software program that realizes the functions of the above-described embodiments is supplied from a recording medium to an imaging apparatus having a computer that can execute the program directly or using wired / wireless communication, and the imaging apparatus supplies the software program. The present invention also includes a case where an equivalent function is achieved by executing the programmed program.

  Therefore, the program code itself supplied to and installed in the computer in order to implement the functional processing of the present invention with the computer included in the imaging apparatus also implements the present invention. That is, the computer program itself for realizing the functional processing of the present invention is also included in the present invention.

  In this case, the program may be in any form as long as it has a program function, such as an object code, a program executed by an interpreter, or script data supplied to the OS.

  As a recording medium for supplying the program, for example, a magnetic recording medium such as a flexible disk, a hard disk, a magnetic tape, MO, CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-R, DVD- There are optical / magneto-optical storage media such as RW, and non-volatile semiconductor memory.

  As a program supply method using wired / wireless communication, when the imaging apparatus has a connection function with a computer network, the computer program itself that forms the present invention in a server on the computer network, or a compressed automatic installation function A method of storing a data file (program data file) that can be a computer program forming the present invention in the execution apparatus, such as a file including the program, and downloading the program data file to the connected execution apparatus. In this case, the program data file can be divided into a plurality of segment files, and the segment files can be arranged on different servers.

  Further, the implementation apparatus and an external computer may be directly connected, and the software program constituting the present invention may be downloaded from the external computer to a nonvolatile memory in the implementation apparatus.

It is a flowchart explaining the moving image recording operation | movement in the imaging device which concerns on embodiment of this invention. It is a block diagram which shows the structural example of the imaging device which concerns on embodiment of this invention. It is a timing chart explaining the operation | movement at the time of still image recording during moving image recording in the conventional imaging device. 6 is a timing chart illustrating an operation during still image recording during moving image recording in the imaging apparatus according to the embodiment of the present invention. It is a timing chart explaining the operation | movement at the time of still image recording during moving image recording in the conventional imaging device. 6 is a timing chart illustrating an operation during still image recording during moving image recording in the imaging apparatus according to the embodiment of the present invention. It is a flowchart explaining the moving image recording operation | movement in the imaging device which concerns on embodiment of this invention. It is a flowchart explaining the detail of the AF process for still image recording during moving image recording in the embodiment of the present invention. It is a flowchart explaining the detail of the AE process for still image recording during moving image recording in embodiment of this invention.

Claims (5)

An imaging device having a still image recording function during video recording,
Automatic exposure control means for performing still image recording automatic exposure control processing while continuing video recording when an instruction to start still image recording processing is detected during video recording;
Autofocus control means for performing still image recording autofocus control processing while continuing moving image recording when there is an instruction to start the still image recording processing during moving image recording;
Still image recording processing is performed based on the still image recording automatic exposure control processing and the still image recording autofocus control processing when a still image recording processing start instruction is issued after the still image recording preparation processing start instruction is issued. Image recording means,
The automatic exposure control means performs the automatic exposure control for still image recording with the aperture value used for the moving image recording as a minimum aperture value when the preparation process start instruction for the still image recording is given. An imaging device.   The automatic exposure control means rearranges an exposure program according to an aperture value when the preparation processing start instruction is detected and a limit shutter speed, and performs exposure control based on the rearranged exposure program. Item 2. The imaging device according to Item 1.   When the autofocus control means is instructed to start the still image recording preparation process, the autofocus control means performs focus detection in a narrower distance range than the autofocus control performed during still image recording that is not during moving image recording. The imaging device according to claim 1 or 2.   4. The still image recording unit according to claim 1, wherein when there is an instruction to start a still image recording process after an instruction to start a preparation process, the still image recording process is performed by interrupting the moving image recording. The imaging device according to any one of the above. A method for controlling an imaging apparatus having a still image recording function during moving image recording,
An automatic exposure control step for performing an automatic exposure control process for still image recording while continuing the video recording when there is an instruction to start a still image recording process during video recording;
An autofocus control step for performing a still image recording autofocus control process while continuing the moving image recording when there is an instruction to start the still image recording during the moving image recording;
Still image recording processing is performed based on the still image recording automatic exposure control processing and the still image recording autofocus control processing when a still image recording processing start instruction is issued after the still image recording preparation processing start instruction is issued. An image recording step,
In the automatic exposure control step, the automatic exposure control for still image recording is performed using the aperture value used for the moving image recording as a minimum aperture value when the still image recording preparation processing start instruction is given. Control method for imaging apparatus.

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