JP2019008005A - Control device, imaging apparatus, control method, program, and storage medium - Google Patents

Abstract

To provide a control device capable of achieving the shortening of an AF time and the improvement of the quality of a display image by determining a focusing direction during zooming.SOLUTION: The control device includes zoom control means (15a) for changing the focal distance of an imaging optical system, image acquisition means (15c) for acquiring a first image and a second image whose focal distances and focus states are different from each other respectively according to the operation of the zoom control means, evaluation value generation means (14) for generating a first evaluation value for calculating a focusing position on the basis of the first image and a second evaluation value for calculating the focusing position on the basis of the second image, and direction determination means (15d) for determining a focus drive direction for obtaining the focusing position on the basis of the first evaluation value and the second evaluation value.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an imaging apparatus capable of performing an automatic focus adjustment operation.

  When performing automatic focus adjustment operation (AF operation) by detecting the contrast of the image, when the subject moves back and forth and zooming is performed accordingly, the focus direction is predicted and the focus is quickly followed. It is effective to determine the direction of the in-focus position during zooming.

  In Patent Document 1, the AF evaluation value of the focus position immediately before the input of the operation for starting shooting is compared with the thresholds A and B, and the search operation is performed from either the end L1 or the end L2 of the movable range based on the comparison result. An autofocus control device that determines whether to start the operation is disclosed. Patent Document 2 discloses a digital camera that, when a human face in an image is recognized, obtains an approximate distance to the face based on the size of the face area and determines an AF search start point based thereon. Yes. This makes it possible to detect the lens position that focuses on the face in a shorter time than when starting from the infinity end.

JP 2007-101907 A JP 2006-201282 A

  However, the autofocus control device disclosed in Patent Document 1 compares the AF evaluation value with a preset threshold value, sets the close end or the infinity end as a start position for searching for the focus position, and once passes the focus position. The focus lens is controlled to a start position for searching for an in-focus position. For this reason, when the subject moves back and forth and performs a zoom operation in accordance with the movement, it is difficult to sufficiently follow the subject.

  The digital camera of Patent Document 2 shortens the AF time by limiting the focus range search range when a face cannot be detected due to a subject other than a person or a person facing backward. I can't.

  Therefore, the present invention provides a control device, an imaging device, a control method, a program, and a storage medium that can reduce the AF time and improve the display image quality by determining the in-focus direction during zooming. The purpose is to do.

  A control apparatus according to one aspect of the present invention includes a zoom control unit that changes a focal length of an imaging optical system, a first image that has a different focal length and a different focus state in accordance with the operation of the zoom control unit, and Image acquisition means for acquiring a second image, a first evaluation value for calculating a focus position based on the first image, and generating the focus position based on the second image A direction for determining a focus driving direction for obtaining the in-focus position based on the evaluation value generating means for generating a second evaluation value for calculation, and the first evaluation value and the second evaluation value; Determination means.

  An imaging device as another aspect of the present invention includes an imaging device that photoelectrically converts an optical image formed through an imaging optical system, and the control device.

  According to another aspect of the present invention, there is provided a control method comprising: a first image and a second image having different focal lengths and focal states according to an operation of a zoom control unit that changes a focal length of an imaging optical system. A second step for obtaining a first evaluation value for calculating a focus position based on the first image and calculating the focus position based on the second image; Generating an evaluation value; and determining a focus driving direction for obtaining the in-focus position based on the first evaluation value and the second evaluation value.

  A program according to another aspect of the present invention causes a computer to execute the control method.

  A storage medium according to another aspect of the present invention stores the program.

  Other objects and features of the present invention are illustrated in the following examples.

  According to the present invention, there is provided a control device, an imaging device, a control method, a program, and a storage medium capable of determining an in-focus direction during zooming to realize a reduction in AF time and an improvement in display image quality. Can be provided.

It is a block diagram of the imaging device in each embodiment. 3 is a flowchart illustrating a shooting operation of the imaging apparatus according to the first embodiment. It is explanatory drawing of the characteristic when the focal distance of the imaging optical system in Example 1 changes. 3 is a flowchart illustrating an operation for determining a focusing direction according to the first exemplary embodiment. 6 is an explanatory diagram of a scan AF operation in Embodiment 1. FIG. It is explanatory drawing of AF frame setting in Example 2. FIG. FIG. 10 is an explanatory diagram of characteristics when the focal length of the imaging optical system changes when the imaging apparatus according to the third embodiment is activated. 10 is a flowchart illustrating a shooting operation of the imaging apparatus according to the third embodiment. FIG. 10 is an explanatory diagram of AF frame setting in the third embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  First, with reference to FIG. 1, an imaging apparatus according to Embodiment 1 of the present invention will be described. FIG. 1 is a block diagram of the imaging apparatus 1. In the imaging apparatus 1, 2 is a zoom lens group, and 3 is a focus lens group. Reference numeral 4 denotes a stop as a light amount adjusting means (exposure means, stop means) for controlling the amount of light beam transmitted through the imaging optical system including the zoom lens group 2 and the focus lens group 3. A lens barrel 31 includes a zoom lens group 2, a focus lens group 3, a diaphragm 4, and the like. The lens barrel 31 (imaging optical system) is configured integrally with the imaging apparatus main body. However, the present embodiment is not limited to this, and the imaging apparatus may include an imaging apparatus body and a lens barrel (imaging optical system) that can be attached to and detached from the imaging apparatus body.

  Reference numeral 5 denotes an image sensor (solid-state image sensor) that includes a CMOS sensor, a CCD sensor, or the like, and photoelectrically converts a subject image (optical image) formed via an imaging optical system and outputs an electrical signal (image data). . Reference numeral 6 denotes an imaging circuit that generates a predetermined image signal by receiving the electrical signal photoelectrically converted by the imaging sensor 5 and performing various image processing. Reference numeral 7 denotes an A / D conversion circuit that converts an analog image signal generated by the imaging circuit 6 into a digital image signal. Reference numeral 8 denotes a memory (VRAM) such as a buffer memory that receives the output of the A / D conversion circuit 7 and temporarily stores an image signal.

  Reference numeral 9 denotes a D / A conversion circuit that reads an image signal stored in the VRAM 8 and converts it into an analog signal, and converts it into an image signal in a form suitable for reproduction output. Reference numeral 10 denotes an image display device (LCD) such as a liquid crystal display device that displays an image signal output from the D / A conversion circuit 9. A storage memory (semiconductor memory) 12 stores image data. Reference numeral 11 denotes a compression / decompression circuit including a compression circuit and an expansion circuit. The compression / decompression circuit 11 reads the image signal temporarily stored in the VRAM 8 and performs a compression process and an encoding process on the image data in order to make it suitable for storage in the storage memory 12. The compression / decompression circuit 11 performs a decoding process and an expansion process for making the image data stored in the storage memory 12 into a form suitable for reproduction and display.

  Reference numeral 13 denotes an AE processing circuit that receives an output from the A / D conversion circuit 7 and performs automatic exposure (AE) processing. Reference numeral 14 denotes a scan AF processing circuit (evaluation value generation means) that performs an automatic focus adjustment (AF) process for receiving an output from the A / D conversion circuit 7 and generating an AF evaluation value. Reference numeral 15 denotes a CPU (control device) having a built-in memory for controlling the imaging device 1. The CPU 15 includes zoom control means 15a, focus control means 15b, image acquisition means 15c, direction determination means 15d, and aperture control means 15e. The zoom control unit 15a controls the third motor drive circuit 20 to change the focal length of the imaging optical system. The focus control unit 15b performs focus adjustment of a subject image (optical image) formed by the imaging optical system. The image acquisition unit 15c acquires a first image and a second image having different focal lengths and focal states according to the operation of the zoom control unit 15a. The first image is an image when the focal length is the first focal length, and the second image is an image when the focal length is the second focal length.

  The direction determination unit 15d determines a focus drive direction for obtaining a focusing position based on the first evaluation value and the second evaluation value. The first evaluation value and the second evaluation value are evaluation values generated by the scan AF processing circuit 14 to calculate the in-focus position based on each of the first image and the second image. is there. The focus drive direction is a direction in which the focus control unit 15b moves the focus lens (focus lens group 3) along the optical axis. The aperture control means 15e adjusts the aperture 4 so that the full aperture value is the same.

  Preferably, the direction determination unit 15d calculates a determination value for determining the focus drive direction based on the first evaluation value and the second evaluation value, and determines the focus drive direction according to the determination value. More preferably, the direction determination unit 15d calculates the determination value by subtracting the first evaluation value from the second evaluation value or dividing the second evaluation value by the first evaluation value. Preferably, the direction determination unit 15d determines the direction in which the focus state of the second image is obtained as the focus drive direction when the determination value is larger than a predetermined value. On the other hand, when the determination value is smaller than the predetermined value, the direction in which the focus state of the first image is obtained is determined as the focus drive direction. Details of each of these parts will be described later. In this embodiment, the CPU 15 and the scan AF processing circuit 14 constitute a control device.

  Reference numeral 16 denotes a timing generator (TG) that generates a predetermined timing signal. Reference numeral 17 denotes an image sensor driver (drive unit) that drives the image sensor 5. Reference numeral 21 denotes an aperture drive motor that drives the aperture 4. Reference numeral 18 denotes a first motor drive circuit that drives and controls the aperture drive motor 21. A focus drive motor 22 drives the focus lens group 3. Reference numeral 19 denotes a second motor drive circuit that drives and controls the focus drive motor 22. A zoom drive motor 23 drives the zoom lens group 2. Reference numeral 20 denotes a third motor drive circuit that drives and controls the zoom drive motor 23.

  An operation switch (operation SW) 24 includes various switch groups. Reference numeral 25 denotes an EEPROM which is an electrically rewritable read-only memory in which programs for performing various controls and data used for performing various operations are stored in advance. 26 is a battery. Reference numeral 28 denotes a strobe light emitting unit. Reference numeral 27 denotes a switching circuit that controls the flash emission of the strobe light emitting unit 28. Reference numeral 29 denotes a display element (LED) that performs warning display or the like.

  Reference numeral 30 denotes an attitude detection circuit that detects an attitude of the imaging apparatus 1 in response to an output signal of the A / D conversion circuit 7 or an output signal of an attitude sensor (not shown). Reference numeral 33 denotes an AF auxiliary light unit, which includes an illuminating unit (light source such as an LED) that illuminates all or a part of the subject when an AF evaluation value is acquired. Reference numeral 32 denotes an AF auxiliary light unit driving circuit for driving the AF auxiliary light unit 33.

  As the storage memory 12 that is a storage medium for image data and the like, a fixed semiconductor memory such as a flash memory or a semiconductor memory such as a flash memory that can be attached to and detached from the card-shaped or stick-shaped imaging device 1 is applied. Is possible. In addition, various types of memory such as a magnetic storage medium such as a hard disk or a floppy disk can be used as the storage memory 12.

  The operation switch 24 includes a main power switch for activating the imaging apparatus 1 to supply power, a release switch for starting a photographing operation (storage operation), a reproduction switch for starting a reproduction operation, and a zoom lens group 2 of the imaging optical system. It includes a zoom switch that moves and zooms. The release switch includes a first stroke (SW1) for generating an instruction signal for starting an AE process and an AF process performed prior to a shooting operation, and a second stroke (SW2) for generating an instruction signal for starting an actual exposure operation. Consists of a two-stage switch.

  Subsequently, the operation of the imaging apparatus 1 configured as described above will be described. First, the light flux of the subject that has passed through the lens barrel 31 of the image pickup apparatus 1 is imaged on the light receiving surface of the image sensor 5 after the amount of light is adjusted by the diaphragm 4. This subject image is converted into an electrical signal by photoelectric conversion processing by the image sensor 5 and is output to the imaging circuit 6. The imaging circuit 6 performs various signal processing on the input signal to generate a predetermined image signal. This image signal is output to the A / D conversion circuit 7 and converted into a digital signal (image data), and then temporarily stored in the VRAM 8. The image data stored in the VRAM 8 is output to the D / A conversion circuit 9, converted into an analog signal, converted into an image signal in a form suitable for display, and then displayed on the LCD 10 as an image. The image data stored in the VRAM 8 is also output to the compression / decompression circuit 11. The compression circuit in the compression / decompression circuit 11 performs compression processing on the image data to convert it into image data in a form suitable for storage, and stores the converted image data in the storage memory 12.

  When a playback switch (not shown) of the operation switches 24 is operated and turned on, a playback operation is started. At this time, the image data stored in a compressed form in the storage memory 12 is output to the compression / expansion circuit 11, subjected to decoding processing, expansion processing, and the like, and then output to the VRAM 8 and temporarily stored. Is done. Further, this image data is output to the D / A conversion circuit 9 and converted into an analog signal, converted into an image signal in a form suitable for display, and then displayed on the LCD 10 as an image.

  On the other hand, the image data digitized by the A / D conversion circuit 7 is also output to the AE processing circuit 13 and the scan AF processing circuit 14 separately from the VRAM 8 described above. The AE processing circuit 13 receives the input digital image signal and performs arithmetic processing such as cumulative addition on the luminance value of the image data for one screen. Thereby, the AE evaluation value corresponding to the brightness of the subject is calculated. This AE evaluation value is output to the CPU 15.

  The scan AF processing circuit 14 receives the input digital image signal, extracts a predetermined frequency component of the image data through a band-pass filter (BPF), further performs arithmetic processing such as cumulative addition, and the high frequency side An AF evaluation value signal corresponding to the amount of contour component is calculated. Specifically, in the scan AF process, a plurality of (for example, four) high-frequency components of image data corresponding to a partial region of the screen designated as the AF region are used, that is, a plurality of different frequency characteristics. And performing arithmetic processing such as cumulative addition. Thereby, a plurality of AF evaluation value signals corresponding to the component amount of the predetermined band and the like are calculated. The AF area is a central portion or one portion of an arbitrary portion on the screen, an arbitrary portion on the central portion or the screen and a plurality of adjacent portions, or a plurality of locations distributed discretely. There are cases. As described above, the scan AF processing circuit 14 plays a role as a predetermined frequency component detection unit that detects a predetermined frequency component from the image signal generated by the imaging sensor 5 in the process of performing the AF processing.

  The TG 16 outputs a predetermined timing signal to the CPU 15, the imaging circuit 6, and the imaging sensor driver 17. The CPU 15 performs various controls in synchronization with this timing signal. The imaging circuit 6 receives a timing signal from the TG 16 and performs various image processing such as separation of color signals in synchronization with the timing signal. The imaging sensor driver 17 receives the timing signal of the TG 16 and drives the imaging sensor 5 in synchronization with this timing signal.

  The CPU 15 controls the first motor drive circuit 18, the second motor drive circuit 19, and the third motor drive circuit 20. As a result, the CPU 15 drives and controls the diaphragm 4, the focus lens group 3, and the zoom lens group 2 via the diaphragm drive motor 21, the focus drive motor 22, and the zoom drive motor 23. That is, the CPU 15 controls the first motor drive circuit 18 based on the AE evaluation value calculated by the AE processing circuit 13 to drive the aperture drive motor 21 so that the aperture amount of the aperture 4 becomes appropriate. AE control to be adjusted is performed. Further, the CPU 15 controls the second motor drive circuit 19 based on the AF evaluation value signal calculated by the scan AF processing circuit 14 to drive the focus drive motor 22 to move the focus lens group 3 to the in-focus position. AF control is performed. When a zoom switch (not shown) among the operation switches 24 is operated, the CPU 15 moves the zoom lens group 2 by controlling the third motor drive circuit 20 and driving the zoom drive motor 23 in response to the operation. Then, a zooming operation of the imaging optical system is performed.

  Next, the shooting operation of the imaging apparatus 1 will be described with reference to FIG. FIG. 2 is a flowchart showing the shooting operation of the imaging apparatus 1. Each step in FIG. 2 is executed by each unit of the imaging apparatus 1 based on a command from the CPU 15.

  In this embodiment, the operation of acquiring the AF evaluation value is scanned while driving the focus lens group 3 to a predetermined position, the interval of the position of the focus lens group 3 for acquiring the AF evaluation value is the scan interval, and the AF evaluation value is acquired. The number is called the number of scan points. In this embodiment, the range for acquiring the AF evaluation value is called a scan range, and the region for acquiring an image signal for detecting the in-focus position is called an AF frame (AF region). The scan range is determined by the product of the scan interval and (the number of scan points−1). When the main power switch of the imaging apparatus 1 is in the ON state and the operation mode of the imaging apparatus 1 is the imaging (recording) mode, the imaging process sequence is executed, and imaging is performed by supplying power to the imaging sensor 5 and the like ( Shooting operation).

  First, in step S <b> 201, the CPU 15 displays an image formed on the image sensor 5 through the lens barrel 31 as an image on the LCD 10. That is, after performing the AE process for the display image and determining the accumulation time of the image sensor 5 and the aperture value of the diaphragm 4, the subject image formed on the image sensor 5 is converted into an electric signal by the photoelectric conversion process of the image sensor 5. And output to the imaging circuit 6. The imaging circuit 6 performs various signal processing on the input signal to generate a predetermined image signal. The predetermined image signal is output to the A / D conversion circuit 7, converted into a digital signal (image data), and temporarily stored in the VRAM 8. The image data stored in the VRAM 8 is output to the D / A conversion circuit 9, converted into an analog signal, converted into an image signal in a form suitable for display, and then displayed on the LCD 10 as an image.

  Subsequently, in step S202, the CPU 15 determines whether or not the zoom switch of the operation switch 24 has been operated. If the zoom switch has been operated, the process proceeds to step S210. In step S210, the CPU 15 drives the zoom lens group 2 and the focus lens group 3 according to a predetermined control procedure while the zoom switch is being operated. Further, the CPU 15 (direction determining means 15d) uses the AF evaluation value acquired by the scan AF processing circuit 14 based on the image signal obtained while the zoom switch is operated (during zooming), to determine the focus position. The direction (focus drive direction for obtaining the in-focus position) is determined. During the operation of the zoom switch, the display on the LCD 10 is also updated as needed. When the process of step S210 ends, the process returns to step S201. Details of step S210 will be described later.

  On the other hand, if the zoom switch is not operated in step S202, the process proceeds to step S203. In step S203, the CPU 15 determines the state of the release switch of the operation switch 24, that is, whether the photographer operates the release switch and SW1 (first stroke of the release switch) is turned on. If SW1 is not on, the process returns to step S201. On the other hand, if SW1 is on, the process proceeds to step S204. In step S <b> 204, the CPU 15 performs an AE process for photographing using the AE processing circuit 13 after performing an initialization process. Subsequently, in step S205, the scan AF processing circuit 14 performs a scan AF process for detecting the in-focus position. Details of the scan AF process will be described later.

  When the in-focus position is obtained in step S205, the process proceeds to step S206, and the CPU 15 performs AF display (AFOK display). Specifically, the CPU 15 performs processing such as displaying an AFOF display by turning on the display element 29 and simultaneously displaying a green frame on the LCD 10. If the in-focus position cannot be obtained in step S205, the process proceeds to step S206, and AFNG display is performed. Specifically, the CPU 15 performs processing such as displaying a yellow frame on the LCD 10 at the same time as performing AFNG display by blinking the display element 29 or the like.

  Subsequently, in step S207, the CPU 15 confirms the state of the release switch (determines whether SW2 is on). If SW2 (second stroke of the release switch) is on, the process proceeds to step S220, and the CPU 15 executes an exposure process. On the other hand, if SW2 is not on, the process proceeds to step S208. In step S208, the CPU 15 determines whether the ON state of SW1 is maintained. If the on state of SW1 is maintained, the process returns to step S207 and waits for SW2 to be on. On the other hand, if the SW1 on state is not maintained, the process returns to step S201.

  Next, the direction determination process performed in step S210 of FIG. 2 and the drive control of the zoom lens group 2 and the focus lens group 3 will be described with reference to FIG. FIG. 3 is an explanatory diagram of characteristics when the focal length of the imaging optical system changes. First, characteristics of the imaging optical system in which the focus lens group 3 is in the same position and in a different focus state when the focal length of the imaging optical system is changed will be described. In many of the optical systems that are capable of zooming operation that are generally adopted, when the focal length (zoom position) of the imaging optical system changes due to the zooming operation, the focusing distance differs unless the focus lens group 3 is moved. .

  In FIG. 3, the horizontal axis indicates the in-focus distance, and the vertical axis indicates the position (focus position) of the focus lens group 3. More specifically, FIG. 3 shows the relationship between the focus lens group 3 and the focus distance at each of zoom position 1 (ZoomPos1), zoom position 2 (ZoomPos2), and zoom position 3 (ZoomPos3). .

  As shown in FIG. 3, when the zoom lens group 2 is at ZoomPos1 and the focus lens group 3 is at the position POa, the focus distance is La. In this state, the zoom switch is operated to perform a zooming operation of the imaging optical system that moves the zoom lens group 2, and when the position of the zoom lens group 2 is ZoomPos2, the focus lens group 3 is at the position POa. If it remains as it is, the in-focus distance is Lb. Therefore, when the zoom lens group 2 is moved, images with different focus states are formed on the imaging sensor 5 before and after that.

  In order to make the in-focus distance the same, it is necessary to move the focus lens group 3 to the position POb. If focus is achieved at the position POa of the focus lens group 3 before the zoom operation is started, if the focus lens group 3 is at the position POb when the zoom lens group 2 is at ZoomPos2, the focus is theoretically reached. Is maintained. Therefore, in this embodiment, the direction of the in-focus position (the in-focus position) during zooming is utilized by utilizing the characteristic that the focus distance is different if the position of the focus lens group 3 is the same before and after the movement of the zoom lens group 2. Focus drive direction for obtaining the

  In FIG. 3, the AF evaluation value (evaluation value 1) at the position POa of the focus lens group 3 at ZoomPos1 which is the AF evaluation value at the distance La, and the Zoom lens Pos2 which is the AF evaluation value at the distance Lb. The AF evaluation value (evaluation value 2) at the position POa is compared. Then, the CPU 15 determines that the direction in which the AF evaluation value increases is the in-focus position direction. Further, the CPU 15 uses the AF evaluation value (evaluation value 3) when the focus lens group 3 is at the position POb with the ZoomPos2 which is the AF evaluation value at the distance La, thereby improving the accuracy of the determination of the in-focus position direction. . In the present embodiment, any one of the evaluation value 1, the evaluation value 2, and the evaluation value 3 is a first evaluation value, and the other two are a second evaluation value.

  For example, when the evaluation value 2 (AF evaluation value at the distance Lb) is larger than the evaluation value 1 (AF evaluation value at the distance La), it can be determined that the subject is in the direction of the distance Lb rather than the distance La. If the evaluation value 2 is larger than the evaluation value 3 (AF evaluation value at the distance La), it can be confirmed that the subject is in the direction of the distance Lb rather than the distance La. Therefore, the CPU 15 can determine that the focus lens group 3 is driven in the direction of the position POa, which is the direction in which the distance Lb is in focus with ZoomPos2, in order to obtain the in-focus position. In this way, the direction determination unit 15d calculates the determination value by subtracting the first evaluation value from the second evaluation value or dividing the second evaluation value by the first evaluation value. Preferably, the direction determination unit 15d uses the first evaluation value and the second evaluation value obtained from the first image and the second image acquired at a plurality of focal lengths with the smallest difference in focal length, Determine the focus drive direction.

  Next, with reference to FIG. 4, the operation of the direction determination process (the determination operation of the in-focus direction) performed in step S210 of FIG. 2 will be described. FIG. 4 is a flowchart showing the operation for determining the in-focus direction. Each step of FIG. 4 is mainly executed by the CPU 15 (direction determining means 15d).

  First, in step S401, the CPU 15 obtains AF evaluation values corresponding to a plurality of predetermined frequency components through a plurality of band pass filters (BPF) at the position of the zoom lens group 2 and the position of the focus lens group 3 at that time. And record. For example, the CPU 15 acquires and records a plurality of AF evaluation values at the position ZoomPos1 of the zoom lens group 2 and the position POa of the focus lens group 3 in FIG.

  Subsequently, in step S402, the CPU 15 (zoom control means 15a) drives the zoom lens group 2 according to the operation of the photographer. In step S403, the CPU 15 determines whether the zoom lens group 2 has reached a predetermined position. If the zoom lens group 2 has not reached the predetermined position, the process returns to step S402 to continue driving the zoom lens group 2. Note that the predetermined position is not the final position of the zoom lens group 2 designated by the photographer's operation, but the position of the zoom lens group 2 suitable for determining the direction. A suitable position means that when the focus lens group 3 is fixed and the position of the zoom lens group 2 is changed, a clear difference occurs in the in-focus distance, and the direction can be determined by comparing the AF evaluation values. In addition, it is a position where it can be determined that the difference in focal length is small and the difference in imaging performance of the imaging optical system is small. Also, the suitable position is the position of the zoom lens group 2 having the same open aperture value in the case of an imaging optical system having a different open aperture value depending on the position of the zoom lens group 2. In the case where there is no obvious difference with respect to the in-focus distance with respect to the position of the zoom lens group 2 having the same maximum aperture value, the following is performed. That is, the zoom lens group 2 is driven to a position where a clear difference occurs with respect to the in-focus distance, and the aperture diameter of the diaphragm is changed at the position of the zoom lens group 2 on the side where the open aperture value is bright (F value is small). Make sure the values are the same.

  Further, the CPU 15 changes the position and size of the AF frame because the shooting angle of view changes with the change of the focal length by driving the zoom lens group 2. First, the position of the AF frame is set so that the center thereof is the same position of the subject. That is, the image acquisition unit 15c sets the same position of the subject as the central area of each of the first image and the second image. When the focal length by driving the zoom lens group 2 becomes κ times, the distance from the center of the screen is set to a position that becomes κ times that before driving the zoom lens group 2. The center position of the AF frame after driving is moved on a straight line connecting the center of the screen and the center of the AF frame before driving so that the distance between the center of the screen and the center position of the AF frame after driving becomes κ times. To do. Also, the size of the AF frame is set to κ times both in the horizontal direction and in the vertical direction as compared to before the zoom lens group 2 is driven.

  The parameter of the band pass filter (BPF) for extracting a predetermined frequency component of the image data when the scan AF processing circuit 14 calculates the AF evaluation value signal is not changed. This is because the same predetermined band component is extracted on the subject side. The size of the AF frame has already been changed to the size accompanying the driving of the zoom lens group 2, and the number of image data input to the scan AF processing circuit 14 has been changed. For this reason, by not changing the parameters of the bandpass filter (BPF), it is possible to extract components in the same predetermined band on the subject side. Note that when the AF frame is shifted from the screen by changing the position and size of the AF frame, the center of the frame is shifted so that the frame does not protrude. As described above, in this embodiment, the image acquisition unit 15c determines the size of the acquisition region according to the focal length so that the sizes of the acquisition regions of the first image and the second image are equal to each other on the subject side. Change the size. Preferably, the image acquisition unit 15c does not change the parameter for the scan AF processing circuit 14 to extract the component amount of the predetermined band when the size of the acquisition region is changed.

  If the zoom lens group 2 has reached the predetermined position in step S403, the process proceeds to step S404. In step S404, the CPU 15 once stops driving the zoom lens group 2, then changes the position and size of the AF frame as described above, and acquires and records AF evaluation values corresponding to a plurality of predetermined frequency components. To do. For example, the CPU 15 acquires and records a plurality of AF evaluation values at the position ZoomPos2 of the zoom lens group 2 and the position POa of the focus lens group 3 in FIG.

  Subsequently, in step S405, the CPU 15 (focus control means 15b) drives the focus lens group 3 to a position where the subject at the same distance as the zoom lens group 2 at the position ZoomPos1 is in focus. For example, the CPU 15 drives the focus lens group 3 in FIG. 3 to the position POb.

  Subsequently, in step S406, the CPU 15 determines whether or not the focus lens group 3 has reached a predetermined position. If the focus lens group 3 has not reached the predetermined position, the process returns to step S405, and the drive of the focus lens group 3 is continued. On the other hand, when the focus lens group 3 has reached the predetermined position, the process proceeds to step S407. In step S407, after stopping the driving of the focus lens group 3, the CPU 15 acquires and records AF evaluation values corresponding to a plurality of predetermined frequency components. For example, the CPU 15 acquires and records a plurality of AF evaluation values at the position ZoomPos2 of the zoom lens group 2 and the position POb of the focus lens group 3 in FIG.

  Subsequently, in step S408, the CPU 15 determines whether or not the zoom lens group 2 has reached the final position (final position) of the zoom lens group 2 designated by the photographer's operation. If the zoom lens group 2 has not reached the final position, the process returns to step S402 and the drive of the zoom lens group 2 is continued. Therefore, there is a combination of positions of the zoom lens group 2 suitable for performing a plurality of direction determinations while driving to the final position where the zoom lens 2 is reached. Therefore, in this embodiment, the direction determination is performed using the AF evaluation value acquired by the combination of the positions of the zoom lens group 2 closest to the final position of the zoom lens 2. For example, consider a case where the zoom lens group 2 is driven from the position ZoomPos1 to the position ZoomPos3 in FIG. At this time, if each of ZoomPos1 and ZoomPos2, and ZoomPos2 and ZoomPos3 are combinations suitable for performing direction determination, the CPU 15 performs direction determination using an AF evaluation value acquired by a combination of ZoomPos2 and ZoomPos3. That is, the AF evaluation value (AF evaluation value at the distance La) at the position POb of the focus lens group 3 with ZoomPos2, and the AF evaluation value (AF evaluation value at the distance Lc) at the position POb of the focus lens group 3 with ZoomPos3. Use to determine the direction. Further, the direction is determined by using the AF evaluation value (the AF evaluation value at the distance La) at the position POc of the focus lens group 3 at ZoomPos3.

  The same applies when the shooting magnification is changed by greatly changing the focal length. When driving from ZoomPos1 to ZoomPosN to the zoom lens group 2 by a photographer's operation, there are combinations of positions of the zoom lens group 2 suitable for performing direction determination in addition to ZoomPos1 and ZoomPos2, and ZoomPos2 and ZoomPos3. . In this case, the direction determination is performed using the AF evaluation value acquired by the combination of the positions of the zoom lens group 2 suitable for determining the direction closest to the final position of the zoom lens 2.

  When the final position of the zoom lens group 2 is reached, in step S409, after stopping the driving of the zoom lens group 2, the CPU 15 acquires and records AF evaluation values corresponding to a plurality of predetermined frequency components. For example, the CPU 15 acquires and records a plurality of AF evaluation values at the position ZoomPos3 of the zoom lens group 2 and the position POc of the focus lens group 3 in FIG. As a result, it is possible to acquire three sets of a plurality of AF evaluation values in the combination of positions of the zoom lens group 2 that is closest to the final arrival position of the zoom lens 2. Hereinafter, these AF evaluation values are referred to as evaluation value 1, evaluation value 2, and evaluation value 3. For example, as shown in FIG. 3, a plurality of AF evaluation values (corresponding to evaluation value 3) at the position ZoomPos3 of the zoom lens group 2 and the position POc of the focus lens group 3 can be acquired. A plurality of AF evaluation values (corresponding to evaluation value 2) at the position ZoomPos3 of the zoom lens group 2 and the position POb of the focus lens group 3 can be acquired. A plurality of AF evaluation values (corresponding to evaluation value 1) at the position ZoomPos2 of the zoom lens group 2 and the position POb of the focus lens group 3 can be acquired. As described above, the direction determination unit 15d, when there is a combination of a plurality of images having a plurality of focal lengths having different focal states during the change of the focal length, the focal length closest to the focal length when the change of the focal length is completed. The focus drive direction is determined using the combination of images acquired in (1).

  Next, a method for determining the direction of the focus position (the focus drive direction for obtaining the focus position) will be described. First, in step S410, the CPU 15 reads the recorded AF evaluation value for each predetermined frequency component, and obtains its reliability. Specifically, the CPU 15 uses the three AF evaluation values (evaluation value 1, evaluation value 2, evaluation value 3) based on the position of the zoom lens group 2 and the position of the focus lens group 3 in order from the lowest frequency component. Calculate a measure of degree. This is obtained by calculating the maximum value and the minimum value of the evaluation value 1, the evaluation value 2, and the evaluation value 3, and then dividing the difference between the maximum value and the minimum value by the sum of the maximum value and the minimum value, the evaluation value 1, and the evaluation value. It is performed using the value 2 and the maximum value of the evaluation value 3. For example, (maximum value−minimum value) / (maximum value + minimum value) is index 1 and the maximum value is index 2. Then, the CPU 15 determines that there is reliability if both the index 1 and the index 2 are equal to or higher than the first threshold for the index 1 that is determined to be reliable and is equal to or higher than the first threshold for the index 2. However, when the evaluation value is integrated in the vertical direction, a value normalized by dividing by the number of lines being integrated is used. The CPU 15 performs this determination for a plurality of frequency components.

  Subsequently, in step S <b> 411, the CPU 15 performs a process of branching according to the magnitude relationship between the reliability determination result, the evaluation value 1, and the evaluation value 2. If either index 1 or index 2 is less than the first threshold and the reliability of the evaluation value is not high, or if no obvious difference is found between the evaluation value 1 and the evaluation value 2, the process goes to step S414. move on. In step S414, the CPU 15 determines that the direction cannot be determined based on the evaluation value of the frequency component, and proceeds to step S421. Even if the reliability is high, if there is no obvious difference between the evaluation value 1 and the evaluation value 2, the image hardly changes even if the frame does not capture the desired subject or the focus distance changes. Since it is assumed that there is a large blurred state or the like, direction determination is impossible.

  On the other hand, when both the index 1 and the index 2 are equal to or higher than the first threshold value, the reliability of the evaluation value is high, and the evaluation value 1 is clearly smaller than the evaluation value 2, the process proceeds to step S412. In step S412, the CPU 15 compares the evaluation value 2 with the evaluation value 3. When the evaluation value 2 is clearly larger than the evaluation value 3, the process proceeds to step S413. In step S413, the CPU 15 determines that the subject is moving in the in-focus distance direction by driving the zoom lens group 2, and that direction is the in-focus position direction. When the evaluation value 2 is larger than the evaluation value 1, it can be determined that the subject moves in the in-focus distance direction by driving the zoom lens group 2 and the in-focus position is in this direction. Since the evaluation value 3 obtained when the in-focus distance is returned to the distance before driving the zoom lens group 2 is smaller than the evaluation value 2, the in-focus position is set in the in-focus distance direction by driving the zoom lens group 2. This determination can be made because it can be confirmed.

  On the other hand, if the evaluation value 2 is not clearly larger than the evaluation value 3 in step S412, the value of the evaluation value in the case where the focus distance is changed is not consistent with the change (in the direction in which the evaluation value decreases). The evaluation value does not decrease as expected even though the lens group 3 is driven). Therefore, in this case, the direction cannot be determined.

  If both index 1 and index 2 are greater than or equal to the first threshold in step S411 and the reliability of the evaluation value is high, and evaluation value 1 is clearly larger than evaluation value 2, the process proceeds to step S415. In step S415, the CPU 15 compares the evaluation value 2 with the evaluation value 3. If the evaluation value 3 is clearly larger than the evaluation value 2, the process proceeds to step S416. In step S416, the CPU 15 compares the evaluation value 1 with the evaluation value 3. If the evaluation value 1 and the evaluation value 3 are substantially equal, the process proceeds to step S420. In step S420, the CPU 15 determines that the subject has not moved and the direction in which the in-focus position is located does not change from the direction obtained before that. At this time, each of the evaluation value 1 and the evaluation value 3 is larger than the evaluation value 2 and the evaluation value 1 and the evaluation value 3 are approximately equal to each other, so that it can be determined that the distance at which the subject exists has not changed. . For this reason, the CPU 15 can determine that the direction of the in-focus position has not changed. In particular, when the focus is obtained immediately before the zoom lens group 2 is driven, the in-focus position is not changed, and it is estimated that the in-focus position is a state in which the distance before the zoom lens group 2 is driven is in focus. .

  If the evaluation value 3 is not clearly larger than the evaluation value 2 in step S415, the evaluation value when the focus distance is changed is not consistent with the change (the focus lens group in the direction in which the evaluation value increases). The evaluation value does not increase as expected even though it is driving 3). Therefore, in this case, the direction cannot be determined.

  In step S416, the CPU 15 compares the evaluation value 1 with the evaluation value 3. If the evaluation value 1 and the evaluation value 3 are not substantially equal, the process proceeds to step S417. When the zoom lens group 2 is driven on the tele side (long focal side) and the evaluation value 1 is significantly larger than the evaluation value 3 (S417 → S419), the distance direction in which the zoom lens group 2 is in focus is driven. The subject is moving in the opposite direction to the direction, and that direction is determined as the in-focus position direction. The same applies when the zoom lens group 2 is driven on the wide side (short focal side) and the evaluation value 3 is significantly larger than the evaluation value 1 (S418 → S419). When each of the evaluation value 1 and the evaluation value 3 is larger than the evaluation value 2, the subject moves in the direction opposite to the in-focus distance direction by driving the zoom lens group 2, and the in-focus position is in this direction. Can be judged. In other cases, it is determined that the direction cannot be determined because the evaluation value when the focus distance is changed is not consistent with the change.

  When the above-described processing is completed, the CPU 15 determines in step S421 whether or not all the recorded predetermined frequency components have been determined. When all the comparisons are completed, the process proceeds to step S422. If at least a part of the comparison has not been completed, the process returns to step S410, and the CPU 15 makes a determination regarding the evaluation value of the next target. In step S422, the CPU 15 finalizes the direction determination result.

  As a result of processing a plurality of frequency components, the CPU 15 adopts the result when there are a plurality of direction determination results and all have the same result. For example, consider a case where there are evaluation values corresponding to four frequency components. Three of them determine that the distance direction in focus by driving the zoom lens group 2 is the in-focus position direction, and if the other one cannot be determined, “drive the zoom lens group 2 to focus. The determined distance direction is determined to be the in-focus position direction ”. If there are different direction determination results, the determination is impossible.

  In this embodiment, when the reliability of the evaluation value is high, the evaluation value 1 and the evaluation value 3 are compared with the evaluation value 2, but the present invention is not limited to this. For example, a ratio between the evaluation value 1 or the evaluation value 3 and the evaluation value 2 may be taken, and the direction of the in-focus position may be determined based on the ratio. For example, evaluation value 2 / evaluation value 1 and evaluation value 2 / evaluation value 3 are obtained, and when this value (ratio) is larger than 1.1, the zoom lens group 2 is driven and the distance direction in focus is set to the in-focus position. Determine the direction. On the contrary, when this value is smaller than 0.9, the direction of the in-focus position does not change from the direction obtained before, or the reverse direction is determined as the in-focus position direction.

  Next, the scan AF process for detecting the in-focus position performed in step S205 in FIG. 2 will be described with reference to FIG. FIG. 5 is an explanatory diagram of the scan AF operation. The scan AF processing circuit 14 receives the input digital image signal within the AF frame, and calculates a plurality of AF evaluation value signals via a plurality of (for example, four) band pass filters (BPF) having different frequency characteristics. To do. The AF evaluation value signal calculated through the bandpass filter (BPF) having any one of the characteristics is the graph shown in FIG. 5 (broken line in FIG. 5). The horizontal axis of the graph in FIG. 5 is the position of the focus lens group 3, and the left side represents the position of the focus lens group 3 that focuses on the far subject and the right side focuses on the near subject. The AF evaluation value signal calculated through the band pass filter (BPF) having any characteristic also has a characteristic as shown in FIG. However, if the conditions such as the frequency characteristics of the subject to be imaged are not appropriate, the characteristics shown in FIG. 5 may not be obtained.

  In the scan AF process, the CPU 15 drives the focus lens group 3 from the current position in a direction (focus drive direction, focus position direction) set based on the result of the direction determination process in step S210. Then, the scan AF processing circuit 14 acquires a digital image signal and calculates an AF evaluation value signal. For example, the CPU 15 determines the distance direction in focus as the in-focus position direction by driving the zoom lens group 2. When the in-focus position direction is the close side, the CPU 15 drives the focus lens group 3 from the current position (position A in FIG. 5) toward the close side (position B), and the scan AF processing circuit 14 outputs the digital image signal. The AF evaluation value signal obtained is calculated. As a result, the AF evaluation value signal becomes maximum at the in-focus position. If the position C in FIG. 5 is the in-focus position, the result is as shown in FIG.

  Outputs are not acquired for stop positions of all the focus lens groups 3 in order to increase the speed of scan AF, but outputs are acquired at predetermined scan intervals (for example, intervals corresponding to 5 depths). In this case, an AF evaluation value signal may be acquired at the three points a1, a2, and a3 shown in FIG. In such a case, the scan AF processing circuit 14 calculates the in-focus position C (the position where the AF evaluation value signal is maximized) from the point where the acquired AF evaluation value signal has the maximum value and the points before and after that. Ask for.

  The AF evaluation value indicates the maximum value Y1 (a2 in FIG. 5) when the focus lens group 3 is at the position X1, and the AF evaluation values are Y2 and Y3 (a1 in FIG. 5) at the positions X2 and X3 before and after that. , A3). At this time, the position X0 of the focus lens group 3 at the in-focus position C is obtained as in the following formula (1).

However, in the formula (1), Y1> Y3 and Y1 ≧ Y2. When the in-focus position C is obtained, the focus lens group 2 is driven to that position.

  Next, a reliability determination method will be described. Except for special cases, the AF evaluation value signal has a distance as shown on the horizontal axis and the shape of the AF evaluation value as shown in FIG. 5 near the maximum position. Therefore, whether or not the AF evaluation value is mountain-shaped near the peak is determined by the difference between the maximum value and the minimum value of the signal, the length of the portion that is inclined at a certain value or more, and the gradient of the inclined portion. By determining based on this, the reliability of the AF evaluation value can be determined. However, the calculation target range is a range of about 5 to 9 points near the maximum position, and a threshold value for determining reliability is prepared.

  As shown in FIG. 5, a scan point that is recognized as being inclined from the maximum position (point a <b> 2) is performed by examining the difference between adjacent AF evaluation values. This check starts from the point a2, examines the difference from the adjacent point a1 on the infinity side, and determines that the point is inclined if the point a2 is larger. Next, the difference between the AF evaluation values of the point a1 compared to the point a2 and its adjacent points is examined. If the value of the point a1 is large and the difference is equal to or greater than a predetermined value, it is determined that the vehicle is inclined. This check is continued until the magnitude relationship between the values of adjacent points in the range is reversed or the difference is smaller than a predetermined value. Similarly, the near side is also examined.

  Then, the width to the point recognized as being inclined is the width L of the mountain, the difference between the point a2 and the value of the point on the infinity side recognized as being inclined, and the difference between the values of the points on the closest side The sum is obtained and the value is defined as the mountain slope SL. The maximum value and the minimum value are the entire maximum value and minimum value of the AF evaluation values within the range. The numerical values for determining the reliability of the AF evaluation value calculated in this way are compared with respective threshold values, and if all the conditions are satisfied, it is determined that the AF evaluation value is reliable. Note that a specific method for determining reliability is described in, for example, Japanese Patent No. 4235422 and Japanese Patent No. 4185541.

  So far, the case where the in-focus position direction is determined to be the closest side has been described as an example. Similarly, in other cases, driving is performed in a predetermined direction from the position of the predetermined focus lens group 3 in each case, a digital image signal is acquired, and an AF evaluation value signal is calculated. As a result, the in-focus position (position C in FIG. 5) can be obtained. When it is determined that the in-focus position direction is the infinity side, driving is performed from the current position (position B in FIG. 5) toward the infinity side (position A), a digital image signal is acquired, and an AF evaluation value signal is calculated. If it is determined that the direction of the in-focus position has not changed and the in-focus position has not been obtained immediately before, the focus lens group 3 is moved toward the near side or the infinity side in accordance with the direction determination result of the immediately previous in-focus position. To obtain a digital image signal and calculate an AF evaluation value signal. When it is determined that the in-focus position has not changed and the in-focus position has been obtained immediately before, the focus lens group 3 is driven in the vicinity of the current position, a digital image signal is acquired, and an AF evaluation value signal is calculated. . For example, after driving the focus lens group 3 at a high speed to the position A1 in FIG. 5 (the AF evaluation value signal is not calculated during this period), the focus lens group 3 is driven from the position A1 to the position B1 in FIG. Then, a digital image signal is acquired and an AF evaluation value signal is calculated.

  When it is impossible to determine the direction of the in-focus position, the focus lens group 3 is driven at a high speed from the current position to a position corresponding to a predetermined infinity (the AF evaluation value signal is not calculated during this period). Thereafter, the focus lens group 3 is driven from the position toward the closest direction, a digital image signal is acquired, and an AF evaluation value signal is calculated. Note that the processing in step S210 may be executed only in a shooting mode for shooting a moving subject such as a sports mode.

  In this embodiment, if the focus lens position is the same when the focal length of the imaging optical system changes, the characteristics of the imaging optical system with different focus states can be used to adjust the focal length and the focus state during zoom operations. A direction with the in-focus position is predicted from evaluation values acquired at different positions. As a result, the AF time is shortened and the image display quality is improved in AF operations such as after the photographer performs a zoom operation so that the size on the screen becomes the same as the subject moves in the distance direction. Improvements can be realized.

  Next, a second embodiment of the present invention will be described. The present embodiment is different from the first embodiment in that a plurality of AF frames are used when determining the direction of the in-focus position. Since the other basic configuration is the same as that of the first embodiment, the description thereof is omitted.

  The setting of the AF frame will be described with reference to FIG. FIG. 6 is an explanatory diagram of AF frame setting. When the AF frame set by the photographer's operation or the like is the reference frame (first frame) shown in the center of FIG. 6, eight AF frames from the second frame to the ninth frame are set around it. The second frame is arranged at a position where a predetermined pixel (Width 1) is shifted to the left in the horizontal direction and a predetermined pixel (High 1) reference frame is shifted to the upper side in the vertical direction. The third frame is arranged at a position shifted by a predetermined pixel (High1) reference frame on the upper side in the vertical direction. The fourth frame is a predetermined pixel (Width1) on the right side in the horizontal direction and a predetermined pixel (High1) reference on the upper side in the vertical direction. It is arranged at a position where the frame is shifted. The fifth frame is arranged at a position shifted by a predetermined pixel (Width 1) reference frame on the left side in the horizontal direction. The sixth frame is arranged at a position where the predetermined pixel (Width 1) reference frame is shifted to the right in the horizontal direction. The seventh frame is arranged at a position where a predetermined pixel (Width 1) on the left in the horizontal direction and a predetermined pixel (High 1) on the lower side in the vertical direction are shifted. The eighth frame is arranged at a position where a predetermined pixel (High1) reference frame is shifted downward in the vertical direction. The ninth frame is arranged at a position where the reference frame is shifted by a predetermined pixel (High1) on the lower side in the vertical direction and a predetermined pixel (Width1) on the right side in the horizontal direction.

  This predetermined pixel is a value set from the amount that the subject position on the solid-state image sensor is expected to move due to camera shake or subject movement. When the shooting angle of view changes with the focal length by driving the zoom lens group 2, the position and size of the AF frame are changed. For this reason, the AF frame may be protruded from the screen by changing the position and size of the AF frame. In this case, the frames other than the reference frame are not set, and when the reference frame protrudes, the center of the frame is shifted so that the frame does not protrude. The operation procedure is the same as that of the first embodiment described with reference to FIGS.

  When step S210 in FIG. 2 is reached, the CPU 15 executes the processing after step S401 in FIG. In the present embodiment, regarding the processing up to step S409, the operations in steps S404, S407, and S409 are different from those in the first embodiment. Acquisition and recording of AF evaluation values are performed for a plurality of AF frames in steps S404, S407, and S409. In each AF frame, AF evaluation values corresponding to a plurality of predetermined frequency components are acquired and recorded. In step S410, the CPU 15 reads the recorded AF evaluation value for each AF frame and predetermined frequency component, and obtains its reliability.

  First, with respect to the reference frame, the CPU 15 sequentially sets the AF evaluation values of a plurality of frequency components from the low frequency components in order of the three AF evaluation values (evaluation value 1, evaluation value) according to the position of the zoom lens group 2 and the position of the focus lens group 3. Value 2, evaluation value 3) Reading and calculating an index representing reliability. The index is the same as in Example 1. A value obtained by dividing the difference between the maximum value and the minimum value of the evaluation value 1, the evaluation value 2, and the evaluation value 3 by the sum of the maximum value and the minimum value is defined as an index 1. In addition, the maximum value of the evaluation value 1, the evaluation value 2, and the evaluation value 3 is set as an index 2. Then, the CPU 15 determines that there is reliability if both the index 1 and the index 2 are equal to or higher than the first threshold for the index 1 that is determined to be reliable and is equal to or higher than the first threshold for the index 2. However, if both the index 1 and index 2 of the reference frame are equal to or greater than a second threshold value that is greater than the first threshold value that determines that there is reliability, the direction determination process is performed only for the reference frame. This is because when the reliability of the reference frame is very high, the condition of the subject is good, such as the contrast of the subject in the reference frame being high and sufficiently containing the components of the predetermined band, and the desired in the reference frame. This is because it can be determined that the subject is captured. Therefore, the direction determination is performed only with the reference frame in order to remove the adverse effects such as perspective conflict caused by using the surrounding AF frame.

  The processing in steps S411 to S420 is the same as that in the first embodiment. In step S421, it is checked whether the determination of all AF frames and all predetermined frequency components has been completed. When the determination is finished, the process proceeds to step S422. On the other hand, if the determination is not completed, the process returns to step S410, and the determination is made regarding the next target evaluation value. However, if both the index 1 and index 2 of the reference frame are equal to or greater than the second threshold value, the process proceeds to step S422 if the processing of all frequency components is completed for the reference frame.

  In step S422, the direction determination result is confirmed. This process is performed with priority given to the processing result of the reference frame. If there are a plurality of results of direction determination as a result of processing of a plurality of frequency components in the reference frame, and all of them have the same result, the result is adopted. This is the same processing as in the first embodiment. For example, assume that there are evaluation values corresponding to four frequency components. Then, three of them determine that the distance direction in focus by driving the zoom lens group 2 is the in-focus position direction, and if the other one cannot be determined, select “focus by driving the zoom lens group 2”. Is determined to be the in-focus position direction ”.

  On the other hand, if it cannot be determined by the processing result of the reference frame, it is determined by majority vote except for those that cannot be determined. Those having a large number of overwhelming determination results such as the most numerous determination results being several times more than other determination results are selected. Here, consider a case where there are evaluation values corresponding to a plurality of AF frames and a plurality of frequency components. The number of processing results obtained by “determining the distance direction in focus as the in-focus position direction by driving the zoom lens group 2” is Nd. The number of processing results obtained by “determining the direction opposite to the in-focus direction by driving the zoom lens group 2 as the in-focus position direction” is Nr. The number of processing results determined as “the direction in which the in-focus position is not changed” is Ns. The number of processing results determined as “direction determination impossible” is Ni. At this time, when Nd ≧ A · (Nr + Ns) is satisfied, “determine that the distance direction in focus by driving the zoom lens group 2 is the in-focus position direction” is the result of the direction determination. When Nr ≧ A · (Ns + Nd) is satisfied, “determining the direction opposite to the in-focus distance direction by driving the zoom lens group 2 as the in-focus position direction” is the result of the direction determination. When Ns ≧ A · (Nd + Nr) is satisfied, “the direction in which the in-focus position is not changed” is set as the result of the direction determination. In other cases, “direction determination is impossible” is set as the direction determination result. When the process of step S210 in FIG. 2 is thus completed, the same operation as that of the first embodiment is performed thereafter.

  Next, Embodiment 3 of the present invention will be described. In this embodiment, when the zoom lens group 2 and the focus lens group 3 are each driven to a predetermined position when the image pickup apparatus 1 is started up, the shooting operation after the start-up is performed using the fact that different distances are brought into focus. This differs from the first embodiment in that the direction of the in-focus position is determined before it becomes possible.

  With reference to FIG. 7, the operation principle of the present embodiment will be described. FIG. 7 is an explanatory diagram of characteristics when the focal length of the imaging optical system changes when the imaging apparatus 1 is activated. When the image pickup apparatus 1 is activated, power is supplied to each unit, and then the CPU 15 performs an operation of driving the zoom lens group 2 and the focus lens group 3 to predetermined positions at the time of activation. During this operation, the CPU 15 first drives the zoom lens group 2 and then drives the focus lens group 3. In the state in which the lens barrel 31 is housed, when the zoom lens group 2 simultaneously drives the focus lens group 3, they interfere with each other. For this reason, driving is started in the order of the zoom lens group 2 and the focus lens group 3. In the state in which the lens barrel 31 is housed, the zoom lens group 2 is at the position ZoomPos0, and the focus lens group 3 is at the position POo. When the imaging apparatus 1 is activated, the zoom lens group 2 is driven toward a predetermined position ZoomPos1 at the time of activation.

Then, upon reaching the predetermined position ZoomPos0-1 it becomes possible to drive the focus lens group 3, starts driving of the focus lens group 3 toward a predetermined position PO ₁ at startup. Note that the driving of the zoom lens group 2 is continued. When the focus lens group 3 has reached a predetermined position PO _1, to stop driving. At this time, the zoom lens group 2 has reached the position ZoomPos0-2. Therefore, the position of the zoom lens group 2 ZoomPos0-2, at position PO ₁ of the focus lens group 3, AF evaluation value for direction determination corresponding to a plurality of AF frames, the plurality of predetermined frequency components (evaluation value 1) To be acquired. Thereafter, when the zoom lens group 2 reaches the predetermined position ZoomPos1 at the start, this is stopped and the lens drive at the start is ended. Therefore, the position of the zoom lens group 2 ZoomPos1, at position PO ₁ of the focus lens unit 3, the next AF evaluation value for direction determination corresponding to a plurality of AF frames, the plurality of predetermined frequency components (evaluation value 2) To be acquired.

  Next, with reference to FIG. 8 and FIG. 9, the lens driving procedure at the time of activation will be described. FIG. 8 is a flowchart showing the photographing operation of the imaging apparatus 1 in the present embodiment. Each step in FIG. 8 is executed by each unit of the imaging apparatus 1 based on a command from the CPU 15. FIG. 9 is an explanatory diagram of AF frame setting in the present embodiment.

  The AF frame is set so as to cover almost the entire surface since it is not known at which position the main subject is located on the screen at the time of activation. For example, as shown in FIG. 9, an AF frame having a size of 33% × 33% of the entire screen is spread over a portion of 80% × 80% of the entire screen. As a result, a portion corresponding to 10% of the entire screen overlaps with the upper, lower, left and right adjacent frames.

  First, in step S801 in FIG. 8, power is supplied to each unit of the imaging apparatus 1, and the CPU 15 performs initialization processing such as resetting variables to be used. In step S802, the CPU 15 drives the zoom lens group 2 toward the predetermined position ZoomPos1 at the time of activation. Subsequently, in step S803, the CPU 15 determines whether or not the position (zoom position) of the zoom lens group 2 has reached a predetermined position ZoomPos0-1 at which the focus lens group 3 can be driven. If the zoom position has not reached the predetermined position ZoomPos0-1, step S803 is repeated until the zoom position reaches the predetermined position ZoomPos0-1. On the other hand, if the zoom position has reached the predetermined position ZoomPos0-1, the process proceeds to step S804.

In step S804, CPU 15 drives towards the focus lens group 3 to a predetermined position PO ₁ at startup. In step S805, CPU 15 determines whether the focus lens group 3 has reached the predetermined position PO ₁ at startup. If the focus position has not reached the predetermined position PO _1, focus position repeats step S805 until it reaches the predetermined position PO _1. On the other hand, when the focus position reaches a predetermined position PO _1, the process proceeds to step S806.

  In step S806, the CPU 15 stops driving the focus lens group 3. In step S807, the CPU 15 determines whether or not the framing is stable. If the framing is not stable, step S807 is repeated until the framing is stabilized. On the other hand, if framing is stable, the process proceeds to step S808. In step S808, the scan AF processing circuit 14 acquires and records an AF evaluation value (evaluation value 1) for performing direction determination corresponding to a plurality of AF frames and a plurality of predetermined frequency components. Whether or not the framing is stable is determined using the output signal of the attitude detection circuit 30 that detects the attitude of the imaging device 1. For example, when the value of the output signal of the attitude detection circuit 30 becomes a certain value or less. The CPU 15 determines that the framing is stable. In other words, in this embodiment, the image acquisition unit 15c determines that the posture of the imaging device 1 is stable based on the output signal of the posture detection circuit 30 (posture detection unit), and then displays the first image and the second image. get.

  In step S809, the CPU 15 determines whether the zoom lens group 2 has reached the predetermined position ZoomPos1 at the time of activation. If the zoom lens group 2 has not reached the predetermined position ZoomPos1, step S809 is repeated until the zoom lens group 2 reaches the predetermined position ZoomPos1. On the other hand, if the zoom lens group 2 has reached the predetermined position ZoomPos1, the process proceeds to step S810. In step S810, the CPU 15 stops driving the zoom lens group 2. In step S811, the scan AF processing circuit 14 acquires and records an AF evaluation value (evaluation value 2) for performing direction determination corresponding to a plurality of AF frames and a plurality of predetermined frequency components.

  Subsequently, in step S812, the CPU 15 reads the recorded AF evaluation value for each AF frame / predetermined frequency component, and obtains its reliability. In this process, the AF evaluation values of a plurality of frequency components are read in order from the lower frequency component in the order of the upper left AF frame to the lower right AF frame. In the present embodiment, unlike the first embodiment, there is no concept of a reference frame because it is not known where the main subject is in the screen at the time of activation. The CPU 15 calculates an index representing the reliability by using two AF evaluation values (evaluation value 1 and evaluation value 2) based on the position of the zoom lens group 2 and the position of the focus lens group 3 having the lowest frequency component. This is obtained by calculating the maximum value and the minimum value of the evaluation value 1 and the evaluation value 2, respectively, and dividing the difference between the maximum value and the minimum value by the sum of the maximum value and the minimum value, The maximum value of the evaluation value 2 is used. (Maximum value−Minimum value) / (Maximum value + Minimum value) is index 1 and the maximum value is index 2. If both index 1 and index 2 are equal to or higher than a threshold value for determining reliability, there is reliability. judge. However, when the evaluation value is integrated in the vertical direction, a value normalized by dividing by the number of lines being integrated is used. This determination is performed for a plurality of frequency components and a plurality of AF frames.

  If it is determined in step S812 that there is no reliability, the process proceeds to step S814. In step S814, the CPU 15 determines that the direction cannot be determined based on the evaluation value in the AF frame and the frequency component, and proceeds to step S817. On the other hand, if it is determined in step S812 that there is reliability, the process proceeds to step S813. In step S813, the CPU 15 checks the magnitude relationship between the evaluation value 1 and the evaluation value 2. If no obvious difference is recognized between the evaluation value 1 and the evaluation value 2, the process proceeds to step S814. Then, the CPU 15 determines that the direction cannot be determined, and proceeds to step S817.

  On the other hand, if the evaluation value 1 is clearly larger than the evaluation value 2, the process proceeds to step S815. In step S815, the CPU 15 determines the direction opposite to the distance direction in focus by driving the zoom lens group 2 as the in-focus position direction. Thereafter, the process proceeds to step S817. On the other hand, if the evaluation value 1 is clearly smaller than the evaluation value 2, the process proceeds to step S816. In step S816, the CPU 15 determines that the in-focus distance direction is the in-focus position direction by driving the zoom lens group 2. Thereafter, the process proceeds to step S817.

  In step S817, the CPU 15 determines whether the determination of all the recorded AF frames and all predetermined frequency components has been completed. When all the determinations are completed, the process proceeds to step S818. On the other hand, if at least a part of the determination is not completed, the process returns to step S812, and the CPU 15 determines the next target evaluation value.

  In step S818, the CPU 15 determines the result of the direction determination. This process is determined by majority except those that cannot be determined. Those having a large number of overwhelming determination results such as the most numerous determination results being several times more than other determination results are selected. When there are evaluation values corresponding to a plurality of AF frames and a plurality of frequency components, the number of processing results obtained by “determining the distance direction in focus by driving the zoom lens group 2 as the in-focus position direction” is Nd. To do. The number of processing results obtained by “determining the direction opposite to the in-focus direction by driving the zoom lens group 2 as the in-focus position direction” is Nr. The number of processing results determined as “direction determination impossible” is Ni. At this time, when Nd ≧ A · Nr is satisfied, “determine that the distance direction in focus by driving the zoom lens group 2 is the in-focus position direction” is the result of the direction determination. When Nr ≧ A · Nd is satisfied, “determining the direction opposite to the distance direction in focus by driving the zoom lens group 2 as the in-focus position direction” is the result of the direction determination. In other cases, “direction determination is impossible” is set as the direction determination result. When the direction of the in-focus position is determined at the time of starting the imaging apparatus 1 in this way, the processing after step S201 is executed in the same manner as in the first embodiment according to FIG.

  In this embodiment, by determining the direction of the in-focus position when the image pickup apparatus 1 is activated, evaluations obtained at different positions of the focal length and the focus state even when the zoom switch is not operated before SW1. The direction in which the in-focus position is located can be predicted from the value. For this reason, it is possible to reduce the AF time after starting the AF operation and improve the display quality. In each embodiment, a compact digital camera has been described as an example. However, each embodiment can also be applied to AF during a live view of a digital video camera or a digital single lens reflex camera.

(Other examples)
The present invention supplies a program that realizes one or more functions of the above-described embodiments 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 and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

  According to each embodiment, a control device, an imaging device, a control method, a program, and a storage medium capable of determining an in-focus direction during zooming to realize a reduction in AF time and an improvement in display image quality Can be provided.

  As mentioned above, although the preferable Example of this invention was described, this invention is not limited to these Examples, A various deformation | transformation and change are possible within the range of the summary.

14 Scan AF processing circuit (evaluation value generating means)
15a Zoom control means 15c Image acquisition means 15d Direction determination means

Claims (18)

Zoom control means for changing the focal length of the imaging optical system;
Image acquisition means for acquiring a first image and a second image having different focal lengths and focus states in accordance with the operation of the zoom control means;
A first evaluation value for calculating the in-focus position is generated based on the first image, and a second evaluation value for calculating the in-focus position is generated based on the second image. An evaluation value generating means;
And a direction determination unit that determines a focus drive direction for obtaining the in-focus position based on the first evaluation value and the second evaluation value. A focus control means for adjusting a focus of a subject image formed by the imaging optical system;
The control apparatus according to claim 1, wherein the focus driving direction is a direction in which the focus control unit moves the focus lens along the optical axis. The first image is an image when the focal length is a first focal length,
The control device according to claim 1, wherein the second image is an image when the focal length is a second focal length. The direction determination means includes
Based on the first evaluation value and the second evaluation value, a determination value for determining the focus drive direction is calculated,
The control apparatus according to claim 1, wherein the focus drive direction is determined according to the determination value.   The direction determination means calculates the determination value by subtracting the first evaluation value from the second evaluation value or dividing the second evaluation value by the first evaluation value. The control device according to claim 4. The direction determination means includes
When the determination value is larger than a predetermined value, the direction in which the focus state of the second image is obtained is determined as the focus driving direction,
6. The control device according to claim 4, wherein when the determination value is smaller than the predetermined value, the direction in which the focus state of the first image is obtained is determined as the focus drive direction.   The control according to any one of claims 1 to 6, wherein the image acquisition unit sets the same position of the subject as a central region of each of the first image and the second image. apparatus.   The image acquisition unit changes the size of the acquisition area according to the focal length so that the acquisition areas of the first image and the second image are equal to each other on the subject side. The control device according to claim 1, wherein the control device is a control device.   9. The control apparatus according to claim 8, wherein the image acquisition unit does not change a parameter for the evaluation value generation unit to extract a component amount of a predetermined band when the size of the acquisition region is changed. .   The direction determination means uses the first evaluation value and the second evaluation value obtained from the first image and the second image acquired at a plurality of focal lengths with the smallest difference in focal length. The control apparatus according to claim 1, wherein the focus driving direction is determined.   The direction determination means includes the first evaluation value and the second evaluation value obtained from the first image and the second image acquired with respect to a plurality of focal lengths having the same open aperture value of the imaging optical system. The control apparatus according to claim 1, wherein the focus drive direction is determined using an evaluation value.   12. The control device according to claim 11, further comprising aperture control means for adjusting aperture means so that the open aperture values are the same. It further has posture detection means for detecting the posture of the imaging device,
The image acquisition unit acquires the first image and the second image after determining that the posture of the imaging apparatus is stable based on an output signal of the posture detection unit. Item 13. The control device according to any one of Items 1 to 12.   The direction determining means, when there is a combination of a plurality of images having a plurality of focal lengths with different focal states during the change of the focal length, the focal length closest to the focal length when the change of the focal length is completed The control device according to claim 1, wherein the focus driving direction is determined using a combination of images acquired in step (14). An image sensor that photoelectrically converts an optical image formed via the imaging optical system;
Zoom control means for changing the focal length of the imaging optical system;
Image acquisition means for acquiring a first image and a second image having different focal lengths and focus states in accordance with the operation of the zoom control means;
A first evaluation value for calculating the in-focus position is generated based on the first image, and a second evaluation value for calculating the in-focus position is generated based on the second image. An evaluation value generating means;
An image pickup apparatus comprising: a direction determination unit that determines a focus drive direction for obtaining the in-focus position based on the first evaluation value and the second evaluation value. Obtaining a first image and a second image having different focal lengths and focal states according to the operation of a zoom control means for changing the focal length of the imaging optical system;
A first evaluation value for calculating the in-focus position is generated based on the first image, and a second evaluation value for calculating the in-focus position is generated based on the second image. Steps,
And a step of determining a focus driving direction for obtaining the in-focus position based on the first evaluation value and the second evaluation value. Obtaining a first image and a second image having different focal lengths and focal states according to the operation of a zoom control means for changing the focal length of the imaging optical system;
A first evaluation value for calculating the in-focus position is generated based on the first image, and a second evaluation value for calculating the in-focus position is generated based on the second image. Steps,
A program for causing a computer to execute a step of determining a focus driving direction for obtaining the in-focus position based on the first evaluation value and the second evaluation value.   A storage medium storing the program according to claim 17.