JP2013197923A - Electron camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electron camera which realizes low power consumption during display of a live view or recording of a moving image.SOLUTION: The electron camera comprises an imaging device, a motion detection part, and a reading control part. The imaging device captures a subject image within an imaging screen and outputs an image. The motion detection part detects the motion amount of the subject on the basis of the detection of the motion amount between images outputted by the imaging device at a predetermined frame rate. On the basis of the motion amount detected by the motion detection part, the reading control part selects reading in a designated region including at least a region in which the subject moves within the imaging screen and controls the imaging device to output images to be used for the next detection of a motion amount between the images.

Description

  The present invention relates to an electronic camera having a function of detecting the movement of a subject.

  2. Description of the Related Art Conventionally, in an electronic camera, a model in which a display monitor such as a liquid crystal is provided on the back surface of the electronic camera body is generally used (see, for example, Patent Document 1).

JP 2007-251590 A

  By the way, in the above-mentioned electronic camera, for example, when shooting a still image, a through image for composition confirmation is displayed on a display monitor as a so-called live view display. Therefore, the occupation ratio of the time occupied by the live view display becomes higher than the usage time of the electronic camera until the photographer confirms the composition with the through image and performs photographing with the release button. In this case, since the imaging device of the electronic camera is always energized, power consumption becomes a problem.

  In view of the above circumstances, an object of the present invention is to provide an electronic camera that achieves low power consumption during live view display or moving image recording.

  An electronic camera according to a first invention includes an image sensor, a motion detection unit, and a read control unit. The imaging element captures an image of a subject in the shooting screen and outputs the image. The motion detection unit detects a motion amount of the subject based on a motion detection amount between images output by the image sensor at a predetermined frame rate. Based on the amount of motion detected by the motion detection unit, the readout control unit selects readout in a designated region including at least a region where the subject moves in the shooting screen, and sets the motion detection amount between the next images on the image sensor. Output the image to be used.

  In a second aspect based on the first aspect, the reading control unit reads the first image composed of the entire shooting screen as the designated area based on the amount of movement, and the area in which the subject in the shooting screen moves as the designated area One of the reading of the second image consisting of the partial region including is selected. When the image sensor outputs a first image corresponding to the current frame, the motion detection unit performs motion detection between the first image corresponding to the previous frame and the first image corresponding to the current frame. When the image sensor outputs a second image corresponding to the current frame, the motion detection unit overwrites a portion that becomes a partial region of the first image corresponding to the frame of the second image with the second image. A third image is generated, and motion detection is performed between the first image and the third image.

  In a third aspect based on the second aspect, the readout control unit performs selection so that readout of the second image is not continuous when the amount of motion is equal to or greater than a preset threshold value.

  In a fourth aspect based on the second aspect, when the amount of motion is less than a preset threshold, the readout control unit continuously selects readout of the second image for a preset number of times.

  In a fifth aspect based on any one of the second to fourth aspects, the reading control unit selects reading of the second image so that the size of the partial region increases as the amount of motion increases.

  ADVANTAGE OF THE INVENTION According to this invention, the electronic camera which implement | achieves low power consumption can be provided during live view display or moving image recording.

1 is a block diagram illustrating a configuration of an electronic camera 1 according to an embodiment. A flowchart showing an example of the operation of the electronic camera 1 Flowchart showing an example of a first mode subroutine The figure explaining the motion amount detection process according to a mode The figure explaining the production | generation process of a pseudo frame The figure explaining an example of the sequence of the process in 1st mode and 2nd mode Flowchart showing an example of a second mode subroutine Flowchart showing an example of a third mode subroutine The figure explaining an example of the sequence of the process in 1st mode and 3rd mode

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, an image output from the entire shooting screen of the image sensor is defined as a first image, and an image in which a partial region including a region in which the subject moves in the shooting screen is output is referred to as a second image. Further, a pseudo frame generated by overwriting (or replacing) a portion that becomes a partial region of the first image with the second image is defined as a third image.

  FIG. 1 is a block diagram illustrating the configuration of the electronic camera 1 of the present embodiment.

  As shown in FIG. 1, the electronic camera 1 includes a photographing optical system 11, an image sensor 12, a timing generator (hereinafter referred to as “TG”) 13, a signal processing unit 14, a RAM (Random Access Memory) 15, a flash A memory 16, a display monitor 17, a recording interface unit (hereinafter referred to as “recording I / F unit”) 18, a touch panel 19, an operation unit 20, a release button 21, an ASIC (Application Specific Integrated Circuit) 22, And a data bus 23.

  Among these, the RAM 15, the flash memory 16, the display monitor 17, the recording I / F unit 18, and the ASIC 22 are connected to each other via the data bus 23. The touch panel 19, the operation unit 20, and the release button 21 are connected to the ASIC 22.

  The photographing optical system 11 is composed of a plurality of lens groups including a zoom lens and a focus lens. For the sake of simplicity, FIG. 1 shows the photographing optical system 11 as a single lens.

  The image sensor 12 captures an image of a subject in the shooting screen and outputs an image (analog image signal). Here, the image sensor 12 is a CMOS (Complementary Metal-Oxide Semiconductor) type image sensor in which a plurality of pixels are two-dimensionally arranged and an arbitrary line can be read by XY addressing. A CMOS type image sensor is provided with a horizontal scanning circuit and a vertical scanning circuit (not shown) for reading an image signal. The image sensor 12 is based on the readout line designated by the vertical scanning circuit, and either the first image composed of the entire photographing screen or the second image composed of a partial region including a region in which the subject moves in the photographing screen. One of them is output (details will be described later). Note that three types of color filters of R (red), G (green), and B (blue) are arranged on the imaging surface of the imaging device 12 in, for example, a Bayer array.

  Here, the image sensor 12 captures a recording image (main image) in response to the full-pressing operation of the release button 21. In addition, the imaging device 12 continuously captures images for observation (through images) at a predetermined frame rate (for example, 30 fps) even during shooting standby (live view display).

  The TG 13 controls the charge accumulation time of the image sensor 12 and the reading of the image signal. Specifically, a control signal is transmitted to each of the image sensor 12 and the signal processing unit 14 in accordance with an instruction from the ASIC 22 to control drive timing. The analog image signal output from the image sensor 12 is input to the signal processing unit 14.

  The signal processing unit 14 performs analog signal processing on an analog front end circuit (AFE) that performs analog signal processing on the image signal output from the image sensor 12 and digital signal processing on the image signal that has been subjected to analog signal processing by the AFE A digital front-end circuit (DFE). Here, the AFE of the signal processing unit 14 performs correlated double sampling or gain adjustment on the analog image signal, and then performs a process of converting the analog image signal into a digital image signal (A / D conversion). Do. The DFE of the signal processing unit 14 removes noise components from the A / D converted digital image signal.

  The image signal output by the signal processing unit 14 is temporarily and sequentially recorded (stored) in the first frame memory 22c or the second frame memory 22d in the ASIC 22 as image data of RGB signals during live view display. Is done. The first frame memory 22c and the second frame memory 22d are buffer memories for use in a preprocess (motion detection) of image processing. The first frame memory 22c and the second frame memory 22d have, for example, a capacity capable of storing image data for the number of frames necessary for the previous process. The motion detector 22a of the ASIC 22 detects the amount of motion by performing inter-frame differences using the image data recorded in the first frame memory 22c and the second frame memory 22d (details will be described later).

  The RAM 15 is a buffer memory that temporarily records image data of a recording image, for example. In other words, the RAM 15 is a buffer memory for use in subsequent steps of image processing (various image processing).

  The flash memory 16 is a non-volatile memory that stores a program for controlling the electronic camera 1 in advance. The ASIC 22 may record a recording image in the flash memory 16. In addition, the display monitor 17 displays various images, an operation menu of the electronic camera 1, and the like according to instructions from the ASIC 22.

  The recording I / F unit 18 is formed with a connector (not shown) for connecting a detachable recording medium 30. Then, the recording I / F unit 18 accesses the recording medium 30 connected to the connector and performs recording processing of an image for recording. The recording medium 30 is, for example, a non-volatile memory card. FIG. 1 shows the recording medium 30 after being connected to the connector.

  The touch panel 19 detects the position of a fingertip or the like that has touched the touch panel surface. The touch panel 19 receives the operation from the photographer by outputting the detected position information to the ASIC 22. The touch panel 19 is composed of a transparent panel having a size equivalent to that of the display monitor 17 and is laminated on the entire surface of the display monitor 17. Moreover, in the example of this embodiment, the touch panel 19 is comprised with the electrostatic capacitance type panel which senses the electrical signal by static electricity. The configuration of the touch panel 19 is not limited to the capacitance type, and a resistive film type panel that detects a change in voltage due to pressure may be used. The operation unit 20 has a plurality of buttons (not shown) that accept operations of the photographer.

  The release button 21 receives an instruction input for a half-press operation (automatic exposure (AE), automatic focusing (AF: auto focus) operation before shooting) and a full-press operation (imaging operation start). Accept.

  The ASIC 22 is a processor that performs various calculations and control of the electronic camera 1. The ASIC 22 controls each part of the electronic camera 1 by executing a program stored in advance in the flash memory 16. The ASIC 22 has a function of the image processing (pre-process and post-process). For example, the ASIC 22 reads the image data recorded in the RAM 15 and performs various image processing (for example, edge enhancement processing, color interpolation processing, white balance processing, etc.) as necessary.

  The ASIC 22 also functions as a motion detection unit 22a and a read control unit 22b. The ASIC 22 includes the first frame memory 22c and the second frame memory 22d described above.

  The motion detection unit 22a detects the amount of motion of the subject of interest that is the tracking target, based on the difference between images output by the image sensor 12 at a predetermined frame rate. Specifically, the motion detection unit 22a first divides the shooting screen into a plurality of blocks, and detects the position of the region of interest in each image. Subsequently, the motion detection unit 22a tracks, for example, a region including a contour shape of a person as a subject of interest across a plurality of time-series images in units of blocks. As an example, first, the motion detection unit 22a detects the position of a subject of interest using image data that is a source of a through image recorded in the first frame memory 22c or the second frame memory 22d. In this case, the motion detection unit 22a detects the motion of the position of the subject of interest based on a known inter-frame difference, and sequentially calculates a motion vector. Thereby, the motion detection unit 22a detects the movement of the subject of interest (the contour shape of the person) and tracks the subject of interest within the shooting screen. In addition, the motion detection part 22a is not restricted to the said method, You may track by another well-known tracking means.

  Based on the amount of motion detected by the motion detection unit 22a, the readout control unit 22b selects readout in a designated region including at least a region in which the subject moves within the shooting screen, and causes the image sensor 12 to perform a difference between the next images. The image used for is output. Specifically, the read control unit 22b selects one of reading of the first image as the designated area and reading of the second image as the designated area based on the amount of motion. Then, when selecting reading of the first image, the reading control unit 22b instructs the vertical scanning circuit of the image sensor 12 to read all line numbers. On the other hand, when the reading control unit 22b selects reading of the second image, the reading control unit 22b instructs the vertical scanning circuit of the image pickup device 12 about the line number to be partially read.

  Here, when the image pickup device 12 outputs the first image corresponding to the current frame, the motion detection unit 22a is configured between the first image corresponding to the previous frame and the first image corresponding to the current frame. Perform motion detection. In addition, when the image sensor 12 outputs the second image corresponding to the current frame, the motion detection unit 22a sets the second region as a partial region of the first image corresponding to the previous frame of the second image. A third image (pseudo frame) overwritten (or replaced) with the image is generated, and motion detection is performed between the first image and the third image. Thereby, in this embodiment, power consumption can be suppressed by the amount of outputting the second image compared to the first image. Since the pseudo frame is originally the first image, when the previous frame is a pseudo frame, the motion detection unit 22a regards the pseudo frame as equivalent to the first image, and determines the current frame (first frame). Motion detection is performed between an image and a pseudo frame.

  In addition, when the amount of motion is equal to or greater than a preset threshold, the read control unit 22a may perform selection so that reading of the second image is not continuous. That is, by making the reading of the second image discontinuous, the reading control unit 22a can also position the subject in the first image even for a subject of interest that moves faster than a subject whose amount of movement is less than a preset threshold. Can be accurately identified and tracked. The threshold value is recorded in advance in the flash memory 16, and the read control unit 22 a reads the threshold value from the flash memory 16.

  In addition, when the amount of motion is less than a preset threshold, the readout control unit 22a may continuously select readout of the second image for a preset number of times. That is, if the amount of motion is less than a preset threshold, the read control unit 22a prevents the target subject from protruding from the region of the second image as much as possible even when the second image is read continuously. Note that the preset number of times is three here. That is, the reading control unit 22a can suppress power consumption by reading the second image three times in succession. Note that the preset number of times (three times) is an example, and is not limited to these three times.

  Next, an example of the operation of the electronic camera 1 of the present embodiment will be described. FIG. 2 is a flowchart illustrating an example of the operation of the electronic camera 1. Here, after the power of the electronic camera 1 is turned on, when the operation unit 20 shown in FIG. 1 receives an input of a shooting mode for taking a still image, the ASIC 22 starts the processing of the flow shown in FIG.

  Step S101: The ASIC 22 instructs the image sensor 12 to acquire a through image via the TG 13. Thereby, the ASIC 22 displays the through image on the display monitor 17 at a frame rate of 30 fps, for example.

  Step S102: The ASIC 22 performs a moving object detection process for the subject of interest to be tracked. Specifically, the ASIC 22 analyzes the image data that is the source of the through image and detects the contour of the subject. For example, the ASIC 22 calculates a portion where the pixel value changes suddenly based on the image data, and detects the portion where the pixel value changes suddenly as a contour.

  The ASIC 22 may employ other moving object detection processing. For example, when the photographer traces the periphery of the subject of interest with the fingertip on the display screen of the display monitor 17, the ASIC 22 receives input of the position coordinates of the region surrounding the subject of interest via the touch panel 19. As a result, the ASIC 22 can detect the target subject to be tracked.

  Step S103: The ASIC 22 sets the first mode. Here, in the first mode, after the first image consisting of the entire photographing screen is read twice as a designated region including a region where the subject of interest moves, the subject of interest within the photographing screen moves as the designated region. In this mode, the second image composed of the partial area including the area is read. When the processing of the flow shown in FIG. 2 is started, the ASIC 22 sets the first mode as the initial setting. Thereafter, as will be described later, the ASIC 22 selects either the second mode setting or the third mode setting according to the amount of movement of the subject of interest.

  Step S104: The ASIC 22 performs motion detection processing according to the mode by a subroutine for each mode (details will be described later).

  Step S105: The ASIC 22 determines whether or not the amount of movement of the subject of interest is greater than or equal to a threshold value. If the amount of motion is equal to or greater than the threshold (step S105: Yes), the ASIC 22 proceeds to the process of step S106. On the other hand, when the amount of motion is less than the threshold (step S105: No), the ASIC 22 proceeds to the process of step S107.

  Step S106: The ASIC 22 sets the second mode, and proceeds to the process of step S108. Here, the second mode is a mode in which reading of the second image is discontinuous when the amount of motion is equal to or greater than a preset threshold value.

  Step S107: The ASIC 22 sets the third mode, and proceeds to the process of step S108. Here, the third mode is a mode in which, when the amount of motion is less than a preset threshold, the second image is continuously read for the preset number of times. In the present embodiment, the second image is read three times.

  Step S108: The ASIC 22 determines whether or not the release button 21 has received an instruction input for a full press operation. When the release button 21 receives an instruction input for a full-press operation (step S108: Yes), the ASIC 22 proceeds to the process of step S109. On the other hand, when the release button 21 has not received an instruction input for a full-press operation (step S108: No), the ASIC 22 returns to the process of step S104 and performs the motion detection process corresponding to the mode again.

  Step S109: The ASIC 22 performs a photographing process for a recording image (main image). Specifically, the ASIC 22 drives the image sensor 12 based on photographing conditions such as an exposure value, an aperture, and a shutter speed in response to an instruction input of a full press operation by the release button 21 via the TG 13. The signal processing unit 14 performs gain adjustment, A / D conversion, and the like of the image signal. The image signal output from the signal processing unit 14 is temporarily recorded as image data in the RAM 15. The ASIC 22 reads the image data recorded in the RAM 15 and performs various image processing (gradation conversion processing, contour enhancement processing, white balance processing, etc.).

  Step S110: The ASIC 22 performs a recording process for the main image. Specifically, the ASIC 22 records the main image on which various image processes have been performed on the recording medium 30 via the recording I / F unit 18. Then, the ASIC 22 ends the flow shown in FIG.

  Next, the motion detection process in the first mode will be described.

  FIG. 3 is a flowchart illustrating an example of the first mode subroutine. FIG. 4 is a diagram illustrating the motion amount detection process according to the mode. FIG. 5 is a diagram for explaining the process of generating a pseudo frame. FIG. 6 is a diagram illustrating an example of a processing sequence in the first mode and the second mode. FIG. 6 schematically shows images sequentially recorded in the first frame memory 22c and the second frame memory 22d. Here, in FIG. 6, a sequence number is assigned to each frame. In addition, the number with a circle in a figure represents the 2nd image. A number with a dash in the figure represents a pseudo frame overwritten with the second image.

  In FIG. 3, in order to make the explanation easy to understand, the processing of the control sequence on the image sensor 12 side and the control on the ASIC 22 side is illustrated (the same applies to FIGS. 7 and 8 described later). In FIG. 3, first, the readout control unit 22b of the ASIC 22 instructs the readout of the first image (full screen), whereby the imaging device 12 starts the process of step S201. Note that the ASIC 22 gives an instruction to the image sensor 12 via the TG 13. In the flow processing, the frame number is generalized by n, but for simplicity, the description will be made assuming that the frame number at the start of reading by the image sensor 12 is n = 1.

  Step S201: The image sensor 12 outputs the first image of the first frame (n = 1). That is, the image sensor 12 reads the captured incident light over the entire effective pixel region and outputs it as the first image of the first frame. The ASIC 22 records the image data of the first image in the first frame memory 22c shown in FIG.

  Step S202: The image sensor 12 outputs the first image of the (n + 1) th frame. As a specific example, the imaging device 12 outputs the first image of the second frame. The ASIC 22 records the image data of the first image in the second frame memory 22d shown in FIG.

  Step S203: The motion detector 22a of the ASIC 22 performs a motion detection process based on the inter-frame difference. Specifically, as shown in FIG. 4, the image is divided into a plurality of blocks. Each block includes a plurality of pixels. Then, for each block, the motion detection unit 22a is between adjacent frames (for example, the first image of the second frame shown in FIG. 4A and the first image of the first frame shown in FIG. 4B). The motion (motion vector) is detected by the difference at. Thereby, the motion detection unit 22a detects a block in which a difference occurs due to the motion vector. For example, as shown in the difference image in FIG. 4C, the movement detection unit 22a is surrounded by a diagonal line by moving from the position of the subject of interest P at the time t1 to the position of the subject of interest P at the time t2. Detect motion.

  Step S204: The reading control unit 22b of the ASIC 22 transmits a plurality of horizontal line numbers (coordinate data) including the block in which the motion is detected. That is, the read control unit 22b instructs the vertical scanning circuit of the image sensor 12 to read the second image. In FIG. 4, the image divided into blocks is associated with the effective imaging area of the imaging device 12, and the readout control unit 22 b instructs readout of line numbers 5 to 8. Further, the reading control unit 22a may select reading of the second image so that the size of the partial area increases as the amount of motion increases. Thereby, the read control unit 22a can suppress power consumption while preventing the subject of interest from being lost.

  Step S205: The image sensor 12 receives the line number (coordinate data) for reading the second image. Specifically, the imaging device 12 manages the readout line by turning on and off the flag, and when the readout line number of the second image is input to the vertical scanning circuit, the flag is turned on for the readout line number. To do.

  Step S206: The image sensor 12 outputs the second image of the (n + 2) th frame. Specifically, the image sensor 12 reads out only the partial region of the line number for which the flag is turned on from the effective pixel region, and outputs it as the image signal of the second image of the third frame. In FIG. 5A, the second image is schematically shown by being divided into blocks. Then, the ASIC 22 receives the image signal of the second image and records it in the second frame memory 22d.

  Step S207: The ASIC 22 overwrites the second image on the first image of the (n + 1) th frame to generate a third image (pseudo frame) of the (n + 2) frame. Specifically, the ASIC 22 overwrites the second image of the third frame (see FIG. 5A) with the first image of the second frame (see FIG. 5B) as the third frame. Three images (pseudo frames) are generated (see FIG. 5C). For convenience of explanation, each image is divided into blocks. FIG. 6 shows that the third image (pseudo frame 3 ') is recorded in the second frame memory 22d as the third frame.

  Step S208: The read control unit 22b sets the number of the next frame (n = n + 3). Specifically, the read control unit 22b sets the number of the next frame (n = 4).

  As described above, the motion detection unit 22a ends the motion detection process according to the first mode, and proceeds to the process of step S105 illustrated in FIG. Then, as described above, the ASIC 22 determines whether or not the motion amount is equal to or greater than the threshold value.

  If the amount of motion is greater than or equal to the threshold, the ASIC 22 sets the second mode. If there is no full-press instruction input, the ASIC 22 proceeds to the process of step S104 again, and performs the motion detection process in the second mode.

  On the other hand, when the amount of motion is less than the threshold, the ASIC 22 sets the third mode. If there is no full-press instruction input, the ASIC 22 proceeds to the process of step S104 again and performs the motion detection process in the third mode. In the case of live view display, for example, the first images (including pseudo frames) sequentially recorded in the first frame memory 22c or the second frame memory 22d are sequentially output to the display monitor 17.

  Hereinafter, the motion detection processing in the second mode and the third mode will be described. First, the motion detection process in the second mode will be described.

  FIG. 7 is a flowchart illustrating an example of the second mode subroutine. In the second mode, as an example, the read control unit 22b alternately reads the first image and the second image. Thereby, in the second mode, it is possible to prevent the deterioration of the image quality due to the movement of the subject of interest. The flow process will be described with reference to FIG.

  In FIG. 7, first, the reading control unit 22b instructs the reading of the first image, whereby the imaging device 12 starts the process of step S301. Here, since the first mode is switched to the second mode, the read control unit 22b instructs to read the first image of the fourth frame in the second mode.

  Step S301: The image sensor 12 outputs the first image of the fourth frame (n = 4). That is, the image sensor 12 reads the entire effective pixel area and outputs it as the first image of the fourth frame. The ASIC 22 records the image data of the first image in the first frame memory 22c shown in FIG.

  Step S302: The motion detector 22a performs a motion detection process based on the inter-frame difference. Specifically, as shown in FIG. 6, the motion detection unit 22a records the third image (pseudo frame 3 ′) of the third frame recorded in the second frame memory 22d and the first frame memory 22c. The motion detection process based on the interframe difference is performed using the first image 4 of the fourth frame.

  Step S303: The read control unit 22b transmits a plurality of horizontal line numbers (coordinate data) including the block in which the motion is detected. That is, the read control unit 22b instructs the vertical scanning circuit of the image sensor 12 to read the second image.

  Step S304: The image sensor 12 receives the line number for reading the second image. Specifically, as described above, when the line number for reading the second image is input to the vertical scanning circuit, the image sensor 12 turns on the flag for the line number to be read.

  Step S305: The image sensor 12 outputs a second image of the (n + 1) th frame. Specifically, the image sensor 12 reads out only the partial region of the line number for which the flag is turned on from the effective pixel region, and outputs it as the image signal of the second image of the fifth frame. Then, the ASIC 22 receives the image signal of the second image and records it in the first frame memory 22c.

  Step S306: The ASIC 22 overwrites the second image on the first image of the nth frame to generate a third image (pseudo frame) of (n + 1) frames. Specifically, the ASIC 22 overwrites the first image of the fourth frame with the second image of the fifth frame, thereby generating a third image (pseudo frame 5 ') as the fifth frame. FIG. 6 shows that the third image (pseudo frame 5 ') is recorded in the first frame memory 22c as the fifth frame.

  Step S307: The read control unit 22b sets the number of the next frame (n = n + 2). Specifically, the read control unit 22b sets the number of the next frame (n = 6).

  As described above, the motion detection unit 22a ends the motion detection process according to the second mode, and proceeds to the process of step S105 illustrated in FIG. Thereafter, the ASIC 22 returns to step S104, and when the motion detection process corresponding to the second mode is repeated, the process of the subroutine of the second mode shown in FIG. 7 is performed. Accordingly, as shown in FIG. 6, each of 6 frames (first image 6), 7 frames (pseudo frame 7 ′), 8 frames (first image 8), 9 frames (pseudo frame 9 ′), and so on. Frames are sequentially recorded in the first frame memory 22c or the second frame memory 22d. Thereby, the motion detection part 22a can perform the difference between frames.

  Next, the motion detection process in the third mode will be described.

  FIG. 8 is a flowchart illustrating an example of a third mode subroutine. FIG. 9 is a diagram illustrating an example of a processing sequence in the first mode and the third mode. In the third mode, for example, when the amount of motion is less than a preset threshold value, the readout control unit 22b selects the second image readout continuously for a preset number of times (three times). As a result, in the third mode, it is possible to save power by continuously reading the second image. If the previous frame has already been output as the second image, the read control unit 22b selects to read the second image in succession twice. That is, as a result, the read control unit 22b selects to read the second image three times in succession.

  In FIG. 8, in the third mode, the image sensor 12 starts the process of step S <b> 401 without the read control unit 22 b issuing an instruction to read the first image. The flow process will be described with reference to FIG.

  Step S401: The image sensor 12 outputs a second image of the fourth frame (n = 4). The ASIC 22 records the image data of the second image in the second frame memory 22d.

  Step S402: The ASIC 22 overwrites the second image on the first image of the (n-1) th frame to generate a third image (pseudo frame) of n frames. Specifically, the ASIC 22 generates the third image (pseudo frame 4 ′) as the fourth frame by overwriting the second image of the fourth frame on the first image (pseudo frame 3 ′) of the third frame. To do. FIG. 9 shows that the third image (pseudo frame 4 ') is recorded in the second frame memory 22d as the fourth frame.

  Step S403: The image sensor 12 outputs the second image of the (n + 1) th frame. Specifically, the image sensor 12 outputs the second image of the fifth frame. The ASIC 22 records the image data of the second image in the second frame memory 22d.

  Step S404: The ASIC 22 overwrites the second image on the first image of the nth frame to generate a third image (pseudo frame) of the (n + 1) th frame. Specifically, the ASIC 22 generates the third image (pseudo frame 5 ′) as the fifth frame by overwriting the second image of the fifth frame with the first image (pseudo frame 4 ′) of the fourth frame. To do. FIG. 9 shows that the third image (pseudo frame 5 ') is recorded in the second frame memory 22d as the fifth frame. Then, the read control unit 22b instructs to read the first image.

  Step S405: The image sensor 12 outputs the first image of the (n + 2) th frame. Specifically, the image sensor 12 reads out the entire effective pixel region and outputs the first image 6 in the sixth frame. The ASIC 22 records the image data of the first image in the first frame memory 22c.

  Step S406: The motion detector 22a performs a motion detection process based on the inter-frame difference. Specifically, the motion detection unit 22a includes the third image (pseudo frame 5 ′) recorded in the second frame memory 22d and the sixth frame recorded in the first frame memory 22c. Using the first image 6, a motion detection process based on the interframe difference is performed.

  Step S407: The read control unit 22b transmits a plurality of horizontal line numbers (coordinate data) including the block in which the motion is detected. That is, the read control unit 22b instructs the vertical scanning circuit of the image sensor 12 to read the second image.

  Step S408: The image sensor 12 receives the line number (coordinate data) for reading the second image. Specifically, as described above, when the line number for reading the second image is input to the vertical scanning circuit, the image sensor 12 turns on the flag for the line number to be read.

  Step S409: The image sensor 12 outputs the second image of the (n + 3) th frame. Specifically, the image sensor 12 reads out only the partial region of the line number for which the flag is turned on from the effective pixel region, and outputs it as the image signal of the second image of the seventh frame. Then, the ASIC 22 receives the image signal of the second image and records it in the first frame memory 22c.

  Step S410: The ASIC 22 overwrites the second image on the first image of the (n + 2) th frame and generates a third image (pseudo frame) of the (n + 3) th frame. Specifically, the ASIC 22 generates a third image (pseudo frame 7 ′) as the seventh frame by overwriting the second image of the seventh frame with the first image 6 of the sixth frame. FIG. 9 shows that the third image (pseudo frame 7 ') is recorded in the first frame memory 22c as the seventh frame.

  Step S411: The read control unit 22b sets the number of the next frame (n = n + 4). Specifically, the read control unit 22b sets the number of the next frame (n = 8).

  As described above, the motion detection unit 22a ends the motion detection process according to the third mode, and proceeds to the process of step S105 illustrated in FIG. Thereafter, the ASIC 22 returns to step S104, and when the motion detection process according to the third mode is repeated, the process of the third mode subroutine shown in FIG. 8 is performed. As a result, as shown in FIG. 9, each frame includes the first frame memory 22c or the eight frames (pseudo frame 8 ′), 9 frames (pseudo frame 9 ′), 10 frames (first image 10), or the like. The data is sequentially recorded in the second frame memory 22d. Thereby, the motion detection part 22a can perform the difference between frames.

  In the case of moving image recording, the first images (including pseudo frames) sequentially recorded in the first frame memory 22c or the second frame memory 22d are recorded in the RAM 15 and subjected to predetermined image processing. And recorded in the flash memory 16 or the recording medium 30.

  As described above, the electronic camera 1 according to the present embodiment captures the second image including the subject moving in the shooting screen based on the information of the readout line fed back from the ASIC 22 during live view display or moving image recording. Output from. The second image is overwritten (or replaced) with the first image and displayed on the display monitor 17 as a pseudo frame. Since the electronic camera 1 can reduce the amount of data transfer by outputting the second image, the power consumption can be reduced accordingly. Therefore, according to the present invention, an electronic camera that realizes low power consumption can be provided.

(Supplementary items of the embodiment)
(1) In the above embodiment, a CMOS type image sensor has been described, but a CCD (Charge Coupled Device) type image sensor may be used.

  (2) In the above embodiment, the subject that moves in the left-right direction in the shooting screen has been described. It may be a subject that moves in the (axis) direction.

  (3) In the above embodiment, a human subject is exemplified as a tracking target from a through image, but the tracking target is not limited to a person, and various objects such as animals and vehicles may be set as tracking targets.

  (4) In the above embodiment, the movement of the subject is detected, and the mode is switched between the second mode and the third mode in accordance with the amount of movement. good.

  (5) In the embodiment described above, the difference between frames is performed between adjacent frames. For example, when the amount of motion is less than the threshold, the first frame output every 30 fps is read and the difference between frames is determined. May be performed.

  (6) In the above embodiment, the threshold value for determining the switching between the second mode and the third mode has been described as the threshold value for the motion amount. However, the motion amount is larger than the determination threshold value for the second mode and the third mode. A new threshold is added, and if the detected amount of motion is greater than or equal to this new threshold, it is determined that the subject moves very quickly and the first image is continuously output every frame. Also good. In this way, when subject movement is very fast, priority is given to tracking the subject's movement, and when subject movement is not so fast, control is given priority to reducing power consumption. Thus, it is possible to perform control suitable for the purpose required according to the shooting conditions.

DESCRIPTION OF SYMBOLS 1 ... Electronic camera, 12 ... Image sensor, 22a ... Motion detection part, 22b ... Read-out control part

Claims (5)

An image sensor that captures an image of a subject in the shooting screen and outputs the image;
A motion detector that detects a motion amount of the subject based on a motion detection amount between images output by the image sensor at a predetermined frame rate;
Based on the amount of motion detected by the motion detection unit, reading in a designated region including at least the region in which the subject moves within the shooting screen is selected, and the amount of motion detection between the next images is selected on the image sensor. A read control unit for outputting an image used for
An electronic camera comprising: The electronic camera according to claim 1,
Based on the amount of movement, the read control unit reads out a first image that is the whole of the shooting screen as the designated area, and a partial area that includes an area in which the subject moves in the shooting screen as the designated area. Select one of the second image reading,
When the image sensor outputs the first image corresponding to the current frame, the motion detection unit is configured to perform the operation between the first image corresponding to the previous frame and the first image corresponding to the current frame. Perform motion detection,
In the case where the image sensor outputs the second image corresponding to the current frame, the motion detection unit is configured to determine a location that is the partial region of the first image corresponding to the previous frame of the second image. An electronic camera that generates a third image overwritten with a second image and performs motion detection between the first image and the third image. The electronic camera according to claim 2,
The electronic camera according to claim 1, wherein when the amount of motion is equal to or greater than a preset threshold value, the readout control unit performs selection so that readout of the second image is not continuous. The electronic camera according to claim 2,
The electronic camera according to claim 1, wherein when the amount of motion is less than a preset threshold, the readout control unit continuously selects readout of the second image for a preset number of times. The electronic camera according to any one of claims 2 to 4,
The electronic camera according to claim 1, wherein the reading control unit selects reading of the second image so that the size of the partial region increases as the amount of motion increases.

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