JP2015040968A - Focus adjustment unit, image capturing device, and focus adjustment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focus adjustment technique which allows for tracking and staying focused on a moving object and, if focus is shifted accidentally onto an object other than a desired object, allows for refocusing on the desired object.SOLUTION: A focus adjustment unit includes control means which: sets a range in which a focusing lens can move; moves the focusing lens within the set range; determines focus condition on the basis of an output signal from image capturing means generated with the movement of the focusing lens within the range; and controls drive means to obtain an in-focus object image. When a target object is a moving object, the set range is set wider, if distances between in-focus positions of the focusing lens corresponding to a plurality of captured images are equal to or less than a threshold value, than the range set if the distances exceed the threshold value.

Description

  The present invention relates to a focus adjustment device, an imaging device, and a focus adjustment method, and more particularly to autofocus used for an electronic camera, a microscope, and the like.

  In the electronic camera, focus adjustment is performed with the focus lens position where the high-frequency component of the luminance signal of the subject image formed on the image sensor is maximized as the focus position where the desired subject image is in focus. A large number of high-frequency components in the luminance signal of the subject image means that the contrast of the subject image is high, indicating that the subject image is in focus as compared with a low case. This is a so-called contrast detection type focus adjustment technique (see, for example, Non-Patent Document 1).

  In such a contrast detection method, the focus lens is moved to acquire the high-frequency component of the luminance signal of the subject image at a plurality of different focus lens positions (scanning operation), and the focus lens is moved to the position where the high-frequency component is the largest. Let

  However, in so-called continuous shooting with a short shooting interval, the time during which the scanning operation can be performed is limited, so that the focus lock at the focus position at the start of continuous shooting or the movement range of the focus lens in the scanning operation between shootings is limited. There are restrictions.

  Also, when performing focus adjustment control for the next shooting in order to focus on a moving subject, the focus lens movement range is set to be equally distributed to both sides with the current focus position as the center. A method for reducing the time required for adjustment has been proposed.

  Also, since continuous shooting is performed continuously at short time intervals, the subject often moves in the same direction between consecutive shootings. Therefore, based on the moving direction of the subject until the previous shooting, that is, the driving direction of the focus lens (the moving direction of the focusing position) until the previous shooting, the focusing position at the next shooting can be predicted to some extent. Is possible. By utilizing this, it has been proposed to change the allocation range of the driving range of the focus lens based on the current in-focus position (see, for example, Patent Document 1).

  The examples shown in FIGS. 14A to 14C show the in-focus positions in three consecutive shootings. In FIG. 14C, the previous (FIG. 14B) in-focus position is used as a reference based on the moving direction of the in-focus position in the previous (FIG. 14A) and previous (FIG. 14B) shooting. As described above, the distribution widths (SC1, SC2) of the scanning ranges on both sides thereof are made different from each other. That is, the distribution width on the same direction side as the previous movement direction is relatively increased.

  In this way, by changing the allocation range of the scanning range based on the moving direction of the in-focus position until the previous shooting, the in-focus lens can be efficiently driven, and the in-focus processing is speeded up. It becomes possible.

  However, in the above-described conventional example, since the reference range is not changed only by relatively increasing the distribution range of the scanning range, it is not possible to deal with a subject whose image plane moving speed gradually increases. Specifically, the image plane moving speed increases at an accelerated speed for a general subject approaching at a constant speed, so in the conventional example, focusing on a subject with such a general movement is required. May be difficult.

  In addition, the conventional method described above has a problem that when a subject other than a desired subject such as a background is mistakenly focused, the subject continues to be focused.

  Therefore, in Patent Document 2, when the interval between the positions of focus lenses that are in focus in a plurality of captured images is equal to or smaller than a preset threshold value, a focus movement range wider than the focus movement range set when the threshold value is exceeded. Set.

JP 2002-122773 A JP 2008-281701 A

  However, when the change in the position of the focus lens is small between consecutive shots as in the focus adjustment device disclosed in Patent Document 2, if the next focus movement range is widened, even when shooting a stationary subject This will increase the focus movement range. In this case, the shooting interval is extended although the desired subject is focused.

  The present invention can focus on a moving subject and focus on a subject other than the desired subject by mistake, so that the desired subject can be refocused. The purpose is to increase the continuous shooting speed.

  In order to solve the above-described problems, the technical feature of the present invention is that a setting unit sets a range in which the focus lens is moved, and a control unit sets the focus lens in the setting step. The focus state is determined based on the output signal from the imaging means obtained while moving the range and the focus lens, and the subject image is focused based on the determined focus state. A control step for controlling the focus lens to move to a focal position; and a prediction means for a plurality of focus lenses obtained by controlling the focus lens to a plurality of focus positions in the control step. A predicting step for predicting a focus position of the focus lens in the next shooting based on the focus position; A determination step of determining whether or not the body, and in the setting step, the range is set with the focus position predicted in the prediction step as a center, and the predicted focus position and prediction of the focus position are performed. If the distance from the in-focus position with respect to the image captured after the image is less than or equal to a preset threshold value and the subject is determined to be a moving subject by the determination step, the range is set when the threshold is exceeded. A wider range is set.

  According to the present invention, in addition to focusing on a moving subject and focusing on a subject other than the desired subject by mistake, it is possible to refocus on the desired subject, and even in the case of a stationary subject The continuous shooting speed can be increased.

It is a schematic block diagram of the imaging device in Example 1, 2 of this invention. It is a flowchart of the operation | movement in Example 1, 2 of this invention. It is a schematic explanatory drawing of the operation | movement in Example 1, 2 of this invention. It is a flowchart of the operation | movement of continuous shooting AF in Example 1 of this invention. It is a flowchart of the scan range setting in Examples 1 and 2 of the present invention. It is a flowchart of scan AF in Example 1, 2 of this invention. It is a flowchart of the setting of the scanning range in Example 1, 2 of this invention. It is a flowchart of still subject determination in Examples 1 and 2 of the present invention. It is a flowchart of peak position prediction determination in Examples 1 and 2 of the present invention. It is a flowchart of the scan center prediction in Examples 1 and 2 of the present invention. It is an example of arrangement | positioning of AF frame in Example 1 of this invention. It is an example of arrangement of AF frames in Example 2 of the present invention. It is a flowchart of operation | movement of continuous shooting AF in Example 2 of this invention. It is explanatory drawing of a prior art example.

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

  FIG. 1 is a schematic configuration diagram of an imaging apparatus according to the present embodiment. Reference numeral 1 denotes an imaging device, 2 denotes a zoom lens group, 3 denotes a focus lens group, 4 denotes a zoom lens group, 2 a focus lens group 3 and the like. A certain aperture. A photographing lens barrel 31 includes a zoom lens group 2, a focus lens group 3, a diaphragm 4, and the like. 5 is a solid-state image sensor (hereinafter referred to as a sensor) that photoelectrically converts a subject image that has passed through the photographing optical system, and 6 performs various image processing by receiving electrical signals photoelectrically converted by the sensor 5. This is an imaging circuit that generates a predetermined image signal. 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 buffer that receives the output of the A / D conversion circuit 7 and temporarily stores the image signal. A memory (VRAM) such as a memory. Reference numeral 9 denotes a D / A conversion circuit which reads out an image signal stored in the VRAM 8 and converts it into an analog signal and converts it into an image signal having a form suitable for reproduction output. Reference numeral 10 denotes a liquid crystal display device for displaying the image signal ( LCD) and other image display devices (hereinafter referred to as LCD). Reference numeral 12 denotes a storage memory that stores image data including a semiconductor memory or the like. Reference numeral 11 denotes a compression / decompression circuit. Reference numeral 11 denotes a compression circuit that reads out an image signal stored in the VRAM 8 and applies a compression process and an encoding process for making it suitable for storage in the storage memory 12. Reference numeral 11 denotes a decompression circuit that performs a decoding process and a decompression process for making the image data stored in the storage memory 12 optimal for reproducing and displaying. 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. A scan AF processing circuit 14 performs an automatic focus adjustment (AF) process for receiving an output from the A / D conversion circuit 7 and generating an AF evaluation value. Here, the AF evaluation value indicates the focus state of the photographing optical system including the focus lens group. Reference numeral 15 denotes a CPU with a built-in memory for controlling the image pickup apparatus. Reference numeral 16 denotes a timing generator (hereinafter referred to as TG) that generates a predetermined timing signal. Reference numeral 17 denotes a sensor driver. 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. Reference numeral 23 denotes a zoom drive motor that drives the zoom lens group 2, and reference numeral 20 denotes a third motor drive circuit that drives and controls the zoom drive motor 23. Reference numeral 24 is an operation switch comprising various switch groups, and 25 is an electrically rewritable read-only memory (EEPROM) in which programs for performing various controls and data used for performing various operations are stored in advance. is there. 26 is a battery, 28 is a strobe light emitting unit, 27 is a switching circuit for controlling flash light emission of the strobe light emitting unit 28, 29 is a display element such as an LED for displaying a warning, etc. 30 is for voice guidance or warning It is a speaker. Reference numeral 33 denotes AF auxiliary light composed of a light source such as an LED, which is an illuminating means for illuminating all or part of the subject when the AF evaluation value is acquired. Reference numeral 32 denotes an AF auxiliary light driving circuit for driving the AF auxiliary light 33. Reference numeral 35 denotes a shake detection sensor that detects camera shake and the like. A shake detection circuit 34 processes a signal from the shake detection sensor 35. Reference numeral 36 denotes a face detection circuit that receives an output from the A / D conversion circuit 7 and detects a face position, a face size, and the like on the screen.

  The storage memory, which is a storage medium for image data or the like, is a fixed semiconductor memory such as a flash memory, or a semiconductor such as a card type flash memory that has a card shape or stick shape and is detachable from the device. Memory is applied. Further, it may be a magnetic storage medium such as a hard disk or a floppy disk.

  As the operation switch 24, there are a main power switch for starting the imaging apparatus 1 and supplying power, and a release switch for starting a photographing operation (storage operation). The operation switch 24 includes a playback switch for starting a playback operation, a zoom switch for moving the zoom lens group 2 of the photographing optical system, and performing zooming.

  The release switch then performs a first stroke (hereinafter referred to as SW1) for generating an instruction signal for starting AE processing and AF processing performed prior to the photographing operation and a second stroke (hereinafter referred to as SW2) for generating an instruction signal for starting an actual exposure operation. And a two-stage switch.

  The operation of this embodiment configured as described above will be described below.

  First, the light flux of the subject that has passed through the photographing lens barrel 31 of the image pickup apparatus 1 is adjusted on the light amount by the diaphragm unit 4 and then imaged on the light receiving surface of the sensor 5. This subject image is converted into an electrical signal by photoelectric conversion processing by the sensor 5 and output to the imaging circuit 6. In the imaging circuit 6, various signal processing is performed on the input signal, and a predetermined image signal is generated. The 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 as an image on the LCD. On the other hand, the image data stored in the VRAM 8 is also output to the compression / decompression circuit 11. After compression processing is performed by the compression circuit in the compression / decompression circuit 11, it is converted into image data in a form suitable for storage and stored in the storage memory 12.

  For example, when a reproduction switch (not shown) of the operation switches 24 is operated and turned on, a reproduction operation is started. Then, 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, etc. in the expansion circuit, and then output to the VRAM 8 and temporarily stored. The Further, the image data 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.

  On the other hand, the image data digitized by the A / D conversion circuit 7 is also output to the AE processing circuit 13, the scan AF processing circuit 14, and the face detection circuit 36 separately from the VRAM 8 described above. First, 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 high-frequency components of the image data through a high-pass filter (HPF) or the like, and performs arithmetic processing such as cumulative addition, AF evaluation value signals corresponding to the contour component amounts and the like are calculated. Specifically, in the scan AF process, a high-frequency component of image data corresponding to a partial area of the screen designated as an AF area is extracted through a high-pass filter (HPF) or the like, and an arithmetic process such as cumulative addition is performed. Thereby, an AF evaluation value signal corresponding to the contour component amount on the high frequency side and the like is calculated. When this AF area is one place in the central part or any part on the screen, or in the central part or any part on the screen and a plurality of adjacent parts, or in a plurality of places distributed discretely and so on.

  As described above, the scan AF processing circuit 14 plays a role of high-frequency component detection means for detecting a predetermined high-frequency component from the image signal generated by the sensor 5 in the process of performing the AF processing.

  The face detection circuit 36 receives the input digital image signal, searches the image for a part characterizing the face such as eyes and eyebrows, and obtains the position of the person's face on the image. Further, the size and inclination of the face are obtained from the positional relationship such as the interval between the parts characterizing the face.

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

  The CPU 15 controls the first motor drive circuit 18, the second motor drive circuit 19, and the third motor drive circuit 20, respectively. Thereby, the diaphragm 4, the focus lens group 3, and the zoom lens group 2 are driven and controlled 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 in the AE processing circuit 13 to drive the aperture drive motor 21 and adjust the aperture amount of the aperture 4 so as to be appropriate. I do. 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 and perform AF control for moving the focus lens group 3 to the in-focus position. Do. When a zoom switch (not shown) among the operation switches 24 is operated, the CPU 15 controls the zoom motor group 23 by controlling the third motor drive circuit 20 to drive the zoom drive motor 23. The zooming operation is performed for the photographing optical system.

  Next, the actual photographing operation of the imaging apparatus will be described with reference to the flowchart shown in FIG.

  In the description of this embodiment, the operation of acquiring the AF evaluation value while driving the focus lens group 3 to a predetermined position is referred to as scanning. Further, the interval of the position of the focus lens for acquiring the AF evaluation value is the scan interval, the number of acquiring the AF evaluation value is the number of scan points, the range for acquiring the AF evaluation value is the scan range, and the image for detecting the focus position An area (focus detection area) from which a signal is acquired is called an AF frame.

  When the main power switch of the imaging apparatus 1 is in the ON state and the operation mode of the imaging apparatus is in the shooting (recording) mode, the shooting process sequence is executed.

  First, in step S201, the CPU 15 displays an image formed on the sensor 5 through the photographing lens barrel 31 as an image on the LCD. That is, the subject image formed on the sensor 5 is photoelectrically converted by the sensor 5 and converted into an electrical signal, and then output to the imaging circuit 6. Therefore, various signal processing is performed on the input signal to generate a predetermined image signal, which is then output to the A / D conversion circuit 7 to be converted into a digital signal (image data) and temporarily stored in the VRAM 8. The 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 as an image on the LCD.

  Next, in step S202, the state of the release switch is confirmed. When the photographer operates the release switch and the CPU 15 confirms that SW1 (the first stroke of the release switch) is turned on, the process proceeds to the next step S203 to set exposure conditions suitable for scan AF. The AF AE process is executed. For this purpose, the value of the diaphragm 4 at the time of performing the LCD display in step S201, the accumulation time of the sensor 5, and the signal amplification factor in the imaging circuit 6 are changed as necessary. The processing time is shortened by changing the changes in parallel rather than sequentially.

  Subsequently, a scan AF process is performed in step S204.

  That is, the CPU 15 performs a scan AF process for detecting the in-focus position in step S204. The outline will be described with reference to FIG. Scan AF is performed by obtaining the position of the focus lens group 3 where the high-frequency component output from the image signal generated by the sensor 5 is the largest. The CPU 15 controls the focus drive motor 22 via a second motor drive circuit 19 that controls the drive of the focus drive motor 22. Thus, the focus lens group 3 is driven from a position corresponding to infinity (“A” in FIG. 3) to a position corresponding to the closest distance set in each photographing mode (“B” in FIG. 3). The output (AF evaluation value signal) of the scan AF processing circuit is acquired while being driven, and the position where the output becomes maximum from the AF evaluation value signal acquired when the driving of the focus lens group 3 is completed (“ C ") is obtained, and the focus lens group 3 is driven to that position.

  Acquisition of the output of the AF processing circuit is not performed for the stop positions of all the focus lens groups 3 in order to increase the speed of scan AF, and the output is acquired at every predetermined scan interval. In this case, the AF evaluation value signal may be acquired at points a1, a2, and a3 shown in FIG. In such a case, the in-focus position C is obtained by calculation from the point where the AF evaluation value signal becomes the maximum value and the points before and after that point.

  When the position of the focus lens group 3 is X1, the AF evaluation value becomes maximum and the value is Y1 (FIG. 3a1), and when the AF evaluation values acquired at the positions X2 and X3 before and after that are Y2 and Y3 (FIG. 3a2, a3), the position X0 of the focus lens group 3 at the in-focus position C is

Is required. However, Y1> Y3 and Y1 ≧ Y2.

  The reliability of the AF evaluation value signal is evaluated before the point where the AF evaluation value signal has the maximum value (C in FIG. 3) is obtained by performing interpolation calculation in this way. If the reliability is sufficient, the point at which the AF evaluation value signal becomes the maximum value is obtained, and AFOK display is performed in step S205. This is performed by turning on the display element 29 or the like, and at the same time, processing such as displaying a green frame on the LCD.

  If the reliability of the AF evaluation value signal is low as a result of evaluating the reliability of the AF evaluation value signal in step S204, the process for obtaining the point at which the AF evaluation value signal has the maximum value is not performed, and the process proceeds to step S205 to display AFNG. This is performed by, for example, blinking the display element 29, and simultaneously performing processing such as displaying a yellow frame on the LCD.

  Note that the reliability evaluation method of the AF evaluation value signal in step S204 is described in a patent document (Japanese Patent No. 04235422, etc.), and thus description thereof is omitted.

  In step S206, the CPU 15 checks whether the ON state of SW1 (the first stroke of the release switch) is maintained. If held, the process proceeds to step S207.

  In step S207, the SW2 (second stroke of the release switch) is confirmed, and if SW2 is on, the process proceeds to step S208, and the counter continuous shooting counter for counting the number of continuous shots is initialized to 1. Turn into. Thereafter, the process proceeds to step S209, the AE process for photographing is executed to determine the exposure condition, and the actual exposure process is executed in step S210, and the value of the continuous shooting counter is incremented by one.

  If the exposure process is completed, the process proceeds to step S211, and SW2 (second stroke of the release switch) is confirmed again. If SW2 is off, the process after SW1 on is terminated, and the process returns to step S206.

  If the SW2 ON state is maintained, the process proceeds to step S212, and processing related to AF (inter-shooting AF processing) performed between shooting is performed.

  Then, after the continuous shooting AF process is completed, the process returns to step S209, the AE process is executed, the exposure conditions are determined, and the actual exposure process is executed.

  However, as a matter of course, the continuous shooting AF processing is performed only when continuous shooting is instructed by the photographer. When continuous shooting is not instructed (for example, when the single shooting mode is designated by the photographer), the state of SW2 is checked in step S211 after the AE processing and exposure processing in steps S209 and S210 are completed. If the SW2 on state is maintained, it waits until it becomes the SW2 off state.

  If SW2 is not turned on in step S207, the process waits until SW2 is turned on. However, if SW1 is turned off during this time, the process returns to step S201.

  Details of the continuous shooting AF performed in step S212 will be described with reference to FIG.

  As described above, when continuous shooting is not instructed, the continuous shooting AF processing is not performed, and therefore the operation when continuous shooting is instructed will be described.

  Since this processing is executed only for the second and subsequent images in continuous shooting, the first processing for this processing is the second processing for continuous shooting. The value of the continuous shooting counter at this time is 2.

  In step S401, it is checked whether or not it is the second continuous shooting. If it is the second continuous shooting (the value of the continuous shooting counter is 2), the process proceeds to step S402, and if it is not the second continuous shooting, the process proceeds to step S403.

  In step S402, the position of the focus lens 3 (peak position FP1) at the time of the first continuous shooting is set as the center ObjP2 of the scan range. The scan range is set by giving priority to not extending the shooting interval during continuous shooting (contains within the time). In consideration of processing performed during continuous shooting, the number of scan points is determined so that the AF operation is completed between shootings, and a scan interval at which AF operation (focus position search) is possible is set. Done in The processing performed during continuous shooting includes, for example, a time for reading an image signal from the image sensor, a check time for the next shooting operation, and the like. The scan range is the product of (the number of scan points minus 1) and the scan interval. However, when the set scan range exceeds the entire region (the entire range from the closest end to be focused to the infinity end), the entire region is set as the scan range. Also, if the end of the set scan range exceeds the position corresponding to the near end or infinity end to be focused, the position corresponding to the near end or infinity end to be focused by shifting the scan range So that the end of the scan range is not exceeded.

  Note that the peak position FP1, the center ObjP2 of the scan range, and the like used here are all obtained from AF evaluation values obtained from the output signal of the entire frame in the scan of S411. In the following description, unless otherwise specified, the peak position, the center of the scan range, and the like are all obtained from the AF evaluation value obtained from the output signal of the entire frame in the scan of S411.

  If the setting of the scan range is completed, the process proceeds to step S411.

  In step S403, it is checked whether or not it is the third continuous shooting (the value of the continuous shooting counter is 3). If it is the third continuous shooting, the process proceeds to step S404, and if it is not the third continuous shooting, the process proceeds to step S405.

In the case of the third continuous shooting, the focus position history information includes information on the first and second continuous shooting (peak positions FP1, FP2). Therefore, in step S404, assuming that the time between continuous shootings is constant, the object position is predicted by primary approximation from the information regarding the two in-focus positions (prediction of the peak position at the time of the third shooting) and the scan range. Center position ObjP3 is obtained from equation (2). The focus position of the focus lens 3 in the next photographing is predicted based on the plurality of focus positions of the focus lens 3 obtained by controlling the focus lens 3 to the focus position multiple times in this way.
ObjP3 = FP2 + (FP2-FP1) × FpAdj3 Formula (2)

  However, the parameter FpAdj3 is a parameter for setting the weight of the prediction result of the subject position and the immediately previous in-focus position, and takes a value of 0 to 1. A scan range is set based on the center position ObjP3 calculated in this way, and the subject image is shifted from the previous scan range in the moving direction.

  In step S404, as in step S402, the scan range is set with priority given to not extending the shooting interval during continuous shooting. Thereafter, the process proceeds to step S411.

On the other hand, in step S405, since the fourth and subsequent shots are taken, the focus position history information includes information on at least three focus positions. Therefore, assuming that the time between continuous shootings is constant, the subject position is predicted by quadratic approximation (peak position prediction at the time of the current shooting). For example, the center position ObjP4 of the scan range at the time of photographing the fourth image can be obtained from Expression (3). A scan range is set based on the center position ObjP4 calculated in this manner, and the subject image is shifted from the previous scan range in the moving direction.
ObjP4 = (FP1-3FP2 + 3FP3) × FpAdj4 + FP3 (1-FpAdj4)
= (FP1-3FP2 + 2FP3) × FpAdj4 + FP3 Formula (3)

  Here, unlike before, the scan range is not set.

  In step S406, the absolute value of the difference between the in-focus position FP3 for the third image and the center position ObjP4 of the scan range for the fourth image is obtained, and this is calculated as the amount of movement of the subject in the optical axis direction. To do.

  In step S407, the amount of movement of the subject in the optical axis direction obtained in step S406 is compared with a predetermined value to determine whether or not the subject has moved greatly in the optical axis direction. As a result, when the movement amount of the subject in the optical axis direction is larger than the predetermined value, the process proceeds to step S408, and the scan range is set. The setting method in this case is the same as the setting method performed in steps S402 and S404, and is set with priority given not to extending the shooting interval in continuous shooting. Thereafter, the process proceeds to step S411.

  If the movement amount of the subject in the optical axis direction is smaller than the predetermined value, the process proceeds to step S409, where it is determined whether the subject is a stationary subject or a moving subject, and the scan range is set.

  In order to solve such a problem that the main subject that has moved moves out of the scan range and is not in focus, such processing needs to be set so that the main subject that has moved is included in the scan range. Because. However, in the case of a stationary subject, setting of such a scan range has an adverse effect of increasing unnecessary operation time.

  The phenomenon in the case of a moving subject occurs as follows.

  In the first shooting, when the ratio of the background subject to the AF area is large, the background is focused, and the background may continue to be focused thereafter. Since the background occupies a large proportion of the subject in the AF area, the background is focused on the first image, and thereafter the background occupies a large proportion in the AF area, so that the background is not the main subject but the background. When the main subject moves and the proportion of the AF area becomes larger than the background, the moved main subject is outside the scanning range set in step S404 and the like and is not focused.

  Therefore, the predetermined value used for the comparison in step S407 is used to determine whether or not the result of the continuous shooting AF sticks to the background. The value is a value by which it can be determined that the subject is not moving in consideration of the detection error of the in-focus position and the predicted position.

  The operation in step S409 will be described with reference to FIG.

  FIG. 11 shows the arrangement of AF frames in this embodiment. As shown in the figure, an AF frame (indicated by a dotted line in the figure) used for AF between continuous shots is divided into three parts horizontally and vertically, and nine AF frames are formed in the photographing screen. Therefore, since the AF evaluation value is acquired from each frame, nine AF evaluation values can be obtained at one scan point. Then, the nine AF evaluation values are added to obtain an AF evaluation value in the entire frame (shown by a dotted line in the figure).

  In the processing after step S701, the reliability of each divided frame is checked. Next, by checking the amount of movement of each frame in the reliable AF frame, it is determined whether the subject to be photographed is moving or stationary, and if the subject is determined to be a moving subject, it is divided. The amount of movement of the subject is predicted using the information of each frame.

  First, in step S701, initialization processing is performed. In addition to resetting the counter to be used, the AF frame to be determined is initialized. As shown in FIG. 11, when the AF frame is divided into nine, the AF frame position is set to “00 frame”.

  In step S702, the reliability in scanning at the time of the previous photographing of the corresponding AF frame evaluated by a method described in a patent document (Japanese Patent No. 04235422) is evaluated. If it is determined that there is no reliability, the process proceeds to step S707. If it is determined that there is reliability, the process proceeds to step S703.

  In step S703, a subject movement amount ΔFPmn in the AF frame being processed is obtained.

Specifically, in step S703, since the fourth and subsequent shots are taken, at least three scans are performed, so there is at least three pieces of information regarding the peak position in the AF frame being processed. Therefore, if the time between continuous shootings is constant, the subject position in the AF frame being processed by the second order approximation is predicted. For example, the predicted position ObjP4mn of the subject at the time of shooting the fourth image is obtained from Expression (4).
ObjP4mn = FP1mn-3 · FP2mn + 3 · FP3mn Formula (4)

  However, FP1mn- is the peak position in the AF frame being processed, which is obtained by scanning at the time of photographing the first image, FP2mn is the second image, and FP3mn is the third image.

  Then, the absolute value of the difference between the peak position FP3mn in the AF frame being processed obtained by scanning at the time of shooting the third image and the center position ObjP4mn of the scan range at the time of shooting the fourth image is obtained. Thus, the movement amount ΔFPmn of the subject in the optical axis direction in the AF frame that is processing this is set.

  In step S704, the obtained movement amount ΔFPmn is compared with a predetermined value, and if it is equal to or larger than the predetermined value, the process proceeds to step S705, and the moving subject counter is counted up. On the other hand, if it is less than the predetermined value, the process proceeds to step S706, and the stationary subject counter is counted up.

  The predetermined value used here is smaller than the predetermined value used in step S407 in FIG. In the case of a moving subject with the entire frame pulled in the background, the scan range for the second and subsequent frames is determined by the peak position (focus position) of the AF evaluation value of the entire frame, so that each divided frame has a sufficient scan range. There is a possibility that the second and third sheets will not stop climbing. This is because the calculated movement amount of the subject may be smaller than the actual movement amount. For example, when the predetermined value in step S407 is 5 times the open depth, it is set to 2.5 times the half open depth.

  Next, in step S707, it is checked whether or not the processing has been completed for all the divided AF frames. If not, the flow proceeds to step S716, and the AF frame to be processed is updated. For example, the AF frame position to be processed is updated to 01 frame when the 00 frame processing is completed, 02 frame when the 01 frame processing is completed, and 10 frame when the 02 frame processing is completed. .

  If the processes of steps S702 to S705 and S706 have been performed for all the divided AF frames, the process proceeds from step S707 to S708, and it is determined whether or not the subject being continuously shot is a stationary subject. Details of this processing will be described later.

  In step S709, if it is determined as a still subject as a result of the process in step S708, the process proceeds to step S710.

In step S710, a scan range for a stationary subject is set. The setting method in this case is similar to the setting method performed in steps S402, S404, and S408, and is set with priority given not to extend the shooting interval in continuous shooting. For example, in the case of the fourth shot, priority is given to not extending the shooting interval in the continuous shooting with the scan range centered on the predicted position ObjP4 of the subject at the time of the fourth shot obtained in step S405. Is set.
On the other hand, if it is determined in step S709 that the subject is a moving subject as a result of the process in step S708, the process proceeds to step S711.

In step S711, it is determined from the information of each divided frame whether the peak position of the AF evaluation value in the current shooting of the moving subject can be predicted. Details of this processing will be described later.
If it is determined that the peak position of the moving subject can be predicted, the process proceeds from step S712 to step S715, the scan center position is predicted using equation (7) described later, and then the process proceeds to step S710.

  In step S710, the scan range is set when the peak position of the stationary subject / AF evaluation value can be predicted and the movement of the subject can be followed. The setting method in this case is the same as the setting method performed in steps S402, S404, and S408, and the scan range is continuous around the predicted position ObjP4 of the subject at the time of shooting the fourth image obtained in step S715. The priority is set not to extend the shooting interval at the time of shooting.

  If it is not determined that the peak position of the moving subject can be predicted, the process advances from step S712 to step S713 to set a scan range for the moving subject. Here, since it is determined that background sticking occurs and the moving subject cannot be tracked, focusing performance is more important than continuous shooting speed. Accordingly, the scan range is set in consideration of the focal length, the shooting distance, the assumed moving speed of the subject, and the like so that the subject can be surely focused.

  Specifically, it is set as follows. FIG. 5 shows the processing procedure.

  First, in step S501, an initial scan range is set.

  Similar to step S710, the number of scan points is determined so that the AF operation is completed between photographing, and a scan interval at which an AF operation (focus position search) is possible is set. The scan range is the product of (the number of scan points minus 1) and the scan interval. If the scan range set in this way exceeds the entire range (the range from the closest end to be focused to the infinity end), or if the entire range can be covered by shifting the scan range, the entire range is set as the scan range. (Step S502 → Step S503).

  If the entire area cannot be covered with the above settings, the number of scan points is increased by 1 in step S504 without changing the scan interval. If the scan range obtained by the product of (the number of scan points minus 1) and the scan interval exceeds the entire range, or the entire range can be covered by shifting the scan range, the entire range is set as the scan range (step S505 → step S503). Here, the whole area means (range from the closest end to be focused to the infinity end).

  If the whole area is not covered even if the number of scan points is increased by 1, the scan interval is not changed in step S504, and the number of scan points is increased to twice the number of scan points before the increase (initial scan point number) (step S506). . If the scan range obtained by the product of (the number of scan points minus 1) and the scan interval exceeds the entire range, or the entire range can be covered by shifting the scan range, the entire range is set as the scan range (step S507 → step S503). .

  If the entire area is not covered, it is determined in step S508 whether or not the set scan range is half or more of the entire area. If it is more than half of the entire area, the scan range set at that time (twice the initial scan range) is used as it is. If it is determined in step S508 that the set scan range is less than half of the entire range, half of the entire scan range is set as the scan range (step S509).

  When the processing in step S713 is completed as described above, the continuous shooting counter is initialized to 1 in step S714. As a result, when it is determined that the subject has not moved due to continuing to focus on the background even though it is a moving subject, shooting at that time is not the first continuous shooting, but the first shot Treated as a shoot. Therefore, the next shooting is also handled as the second shooting. The same applies to the following photographing.

  If the above processing is completed, the process proceeds to step S411.

  In step S411, scanning is performed according to the flowchart of FIG. First, an AF evaluation value of each divided frame is acquired. Next, the AF evaluation value of the entire frame is calculated. The AF evaluation values for the divided frames in the same focus lens group 3 are added to obtain the AF evaluation value for the entire frame at the position of the focus lens group 3. Thereafter, the peak position of the AF evaluation value of each divided frame and the peak position of the AF evaluation value of the entire frame are obtained. If it is divided into nine as shown in FIG. 11, the peak positions of a total of ten AF evaluation values are obtained.

  In step S412, the focus lens 3 is moved to the peak position of the entire frame.

  Note that the focus lens 3 is not driven to a fixed point in the second and subsequent frames of continuous shooting. This is because the subject is considered to exist at the same image plane position during continuous shooting, so the previous focus position (focus lens drive position) was in focus rather than driving the focus lens to a fixed point. This is because the possibility of obtaining an image is considered high.

Similarly, in the case of continuous shooting for the fifth and subsequent shots (continuous shooting counter value is 5 or more), the subject position is predicted by quadratic approximation (the peak position is predicted for the current shooting) and the scan range is set. Center position ObjP (n) is obtained from equation (5). Based on the center position ObjP (n) calculated in this way, a scan range is set and shifted from the previous scan range in the direction in which the subject image moves.
ObjP (n) = (FP (n−3) −3FP (n−2) + 2FP (n−1)) × FpAdj (n) + FP (n−1) Equation (5)

  However, as in the case of the fourth shot, if the amount of movement of the subject is equal to or less than the predetermined value, the process proceeds to step S409, where it is determined whether the subject is a stationary subject according to the operation procedure of FIG. I do.

  Such processing may lead to a reduction in the continuous shooting speed (number of shots per unit time), but when the background sticking occurs and the moving subject cannot be tracked, the main subject is surely focused. Can do. If the subject is not really moving, or if the subject is moving but is not moving too much, or if it can be tracked from divided information, or if it is a stationary subject, the continuous shooting speed ( The number of shots per unit time) is not reduced.

  Here, the scanning operation (step S411) in the flowchart of FIG. 4 will be described with reference to the flowchart of FIG.

  First, in step S601, the focus lens 3 is moved to a scan start position at a speed faster than the speed during the scanning operation.

  In this embodiment, the scan start position is set at one end of the set scan range. In step S602, the AF evaluation value of the area corresponding to the AF frame set in the shooting area and the position of the focus lens group 3 are stored in a calculation memory (not shown) built in the CPU 15. In step S603, it is checked whether or not the lens position is at the scan end position. If it is the end position, the process proceeds to step S605; otherwise, the process proceeds to step S604. The scan end position is set at the other end of the set scan range. In step S604, the focus lens group 3 is driven and moved in a predetermined direction by a predetermined amount. In step S605, the peak position of the focus lens group 3 corresponding to the position where the AF evaluation value is maximum is calculated from the AF evaluation value stored in step S602 and the position of the focus lens group 3.

  Here, the operation of determining whether or not the subject is a stationary subject in step S708 will be described with reference to FIG.

  First, in steps S801 and S802, the values of the moving subject counter and the stationary subject counter are checked.

  If the value of the stationary subject counter counted in step S706 of FIG. 7 is equal to or greater than the first stationary subject determination predetermined value, the process proceeds to step S813, and the main subject is determined to be a stationary subject.

  Next, in step S802, if the value of the stationary subject counter is equal to or larger than the second stationary subject determination predetermined value smaller than the first and the moving subject counter is equal to or smaller than the first moving subject determination predetermined value, the process proceeds to step S813, and the main subject is stationary. Judge as a subject.

  In step S803, the moving subject counter is compared with a second moving subject determination predetermined value, and if it is equal to or larger than the predetermined value, the process proceeds to step S812, and the main subject is determined to be a moving subject.

  In the case of being influenced by the background, there is a possibility that the subject is a moving subject even if the subject movement amount ΔFP based on the in-focus position obtained from the AF evaluation value obtained for the entire AF frame is small. This is because the background is in the AF frame. In the case of a moving subject, there should be an AF frame in the divided AF frame in which the subject movement amount ΔFP is large without being affected by the background. It is. Therefore, when the value of the moving subject counter is equal to or greater than the second moving subject determination predetermined value, it is determined that the moving subject is photographed and the focus position of the entire AF frame is stuck on the background.

  Also, if the value of the stationary subject counter is smaller than the first stationary subject determination predetermined value, even if the value of the moving subject counter is small, the subject is moving because of the moving subject, the subject moves during scanning, moves out of the AF frame, etc. May be affected. Therefore, even when the value of the stationary subject counter is equal to or greater than the second stationary subject determination predetermined value, there is a possibility that the moving subject is photographed and the in-focus position of the entire AF frame sticks to the background. Therefore, it is determined that a still subject is being photographed only when the value of the moving subject counter is equal to or smaller than the first moving subject determination predetermined value and the value of the stationary subject counter is equal to or greater than the second stationary subject determination predetermined value.

  In step S804, it is checked whether the sum of the value of the stationary subject counter and the value of the moving subject counter is equal to or less than a predetermined value of the number of AF frames determined that the AF evaluation value is not reliable. An AF frame with a reliable AF evaluation value can be determined as a stationary subject or a moving subject, but a subject in an AF frame with no reliability cannot do so. As a factor that lowers the reliability, a reduction in the contrast of the subject due to the movement of the subject can be considered. Therefore, if the sum of the value of the stationary subject counter and the value of the moving subject counter is less than the predetermined value of the number of AF frames determined to be unreliable, the process proceeds to step S814, and the main subject is determined to be a moving subject.

  Thereafter, in step S805, the moving subject counter is compared with a third moving subject determination predetermined value. If it is less than the predetermined value, the process proceeds to step S806, and if it is greater than the predetermined value, the process proceeds to step S809.

  In step S806, it is checked whether the AF frame determined to be unreliable is the same AF frame as when the previous AF evaluation value was acquired. If it is determined that the same AF frame is not reliable, the process proceeds to step S807, and the movement amount of the entire frame when it is determined that the same AF frame is not reliable is compared with the threshold value of the movement amount regarded as a stationary subject. If it is equal to or smaller than the threshold value, the process proceeds to step S815, and the main subject is determined to be a stationary subject. On the other hand, if the threshold is exceeded, the process proceeds to step S814, and the main subject is determined to be a moving subject.

  If it is determined in step S806 that there is no reliability in a different AF frame, the process proceeds to step S808. Then, the movement amount of the entire frame when it is determined that there is no reliability in a different AF frame is compared with the threshold value of the movement amount regarded as a stationary subject. If it is equal to or less than the threshold value, the process proceeds to step S815, and the main subject is a stationary subject. Is determined. On the other hand, if the threshold is exceeded, the process proceeds to step S814, and the main subject is determined to be a moving subject.

  On the other hand, if the moving subject counter is equal to or greater than the third moving subject determination predetermined value, the process proceeds from step S805 to step S809.

  In step S809, it is determined whether or not the positions of all AF frames determined to have a moving subject are at the four corners and the amount of movement in the AF frame is equal to or less than a predetermined value. For example, as shown in FIG. 11, when nine AF frames are set, all the AF frames determined to have a moving subject are 00 frames, 02 frames, and 20 frames. It is determined whether the amount of movement in any of the 22 frames and the movement amount in all AF frames is equal to or less than a predetermined value. If the condition is satisfied, the process advances to step S815 to determine that the main subject is a stationary subject.

  If any of the AF frames determined to have a moving subject is not a four-corner AF frame, the process proceeds to step S810. Then, the peak position of the AF evaluation value of the AF frame in which it is determined that there is a moving subject is compared with the peak position of the AF evaluation value at the time of the previous AF evaluation value acquisition in the upper, lower, left and right AF frames of the AF frame. For example, consider a case where nine AF frames are set as shown in FIG. 11 and the number of frames determined to have a moving subject is eleven. In this case, the peak position of the AF evaluation value of the 11th frame, the peak position of the AF evaluation value of the 01th frame at the time of the previous AF evaluation value acquisition, the peak position of the AF evaluation value of the 10th frame, the AF evaluation value of the 12th frame The peak position is compared with the peak position of the AF evaluation value of the 21 frame, and the difference is obtained.

  If any of the obtained peak position differences is equal to or less than the peak position difference of the AF evaluation value regarded as a stationary subject, the process proceeds from step S811 to step S815, and the main subject is determined to be a stationary subject.

  Conversely, if the peak position difference of the AF evaluation value regarded as a stationary subject has been exceeded, the process proceeds from step S811 to step S814, and the main subject is determined to be a moving subject.

In addition, when the AF frame is divided into 9 × 3 × 3 frames,
The first stationary subject determination predetermined value is 8, the second stationary subject determination predetermined value is 7, the first moving subject determination predetermined value is 0, and the second moving subject determination predetermined value is about 2. The predetermined value of the sum of the stationary subject counter value and the moving subject counter value used for the determination is a value of about 6. The predetermined value of the moving subject counter used for the determination in S804 is a value of about 1. The same AF frame is not reliable. The threshold value of the movement amount for which the movement amount of the entire frame is determined to be a stationary subject when it is determined to be a value of about 4 depths. The movement amount of the entire frame when determined to be unreliable with a different AF frame is The threshold for the amount of movement to be regarded is a value of about 3 depths. The amount of movement to be regarded as a stationary subject used in S809 is a value of about 4 depths. Just do it.

  Here, the peak position prediction determination operation performed in step S711 will be described with reference to FIG.

  First, in step S901, initialization processing is performed. In addition to resetting the counter to be used, the AF frame to be determined is initialized. As shown in FIG. 11, when the AF frame is divided into nine, the AF frame position is set to “00 frame”.

  In step S902, the reliability of the corresponding AF frame evaluated by a method described in a patent document (eg, Japanese Patent No. 04235422) in the previous shooting is evaluated. If it is determined that there is no reliability, the process proceeds to step S905. If it is determined that there is reliability, the process proceeds to step S903.

  In step S903, it is determined whether the AF frame being processed is an upper frame or a middle frame. For example, if the camera is divided into nine AF frames as shown in FIG. 11, if the camera is in the normal position, the 00 frame, 01 frame, 02 frame are the upper frame, 10 frames, 11 frames, 12 frames are the middle frame. And

  If the AF frame being processed is an upper frame or a middle frame, the movement amount ΔFPmn of the subject in the AF frame being processed in step S904 is obtained, and then the process proceeds to step S905. This calculation method is the same as steps S405 and S406 in FIG.

  If the AF frame being processed is other than the upper frame or the middle frame, the process proceeds to step S905.

  In step S905, it is checked whether the processing has been completed for all the divided AF frames. If not, the process proceeds to step S906, and the AF frame to be processed is updated. For example, the AF frame position to be processed is updated to 01 frame when the 00 frame processing is completed, 02 frame when the 01 frame processing is completed, and 10 frame when the 02 frame processing is completed. .

  If the processing has been performed for all the divided AF frames, the process proceeds to step S907, and the AF frame in which the moving amount of the subject obtained in S904 is maximized and its moving amount are obtained.

When the movement amount of the central frame (11 frames in the example shown in FIG. 11) is the maximum, the process proceeds from step S908 to step S909, and the central frame is set as an AF frame used for prediction.
When the movement amount of the central upper frame (01 frame in the example shown in FIG. 11) is the maximum, the process proceeds from step S910 to step S911, and the central upper frame is set as the AF frame used for prediction.

  When the movement amount of the AF frame other than the center frame or the center upper frame is the maximum, the process proceeds from step S910 to step S914, and it is determined that peak prediction is impossible. And the process after step S713 of FIG. 7 is performed after that.

  In step S912, it is determined whether the movement directions of the AF frames that are the prediction frames match.

P _N−2 −P _N−1 > ΔP when the peak positions of the AF evaluation values for the current, previous, and last time AF evaluation values of the AF frame set as the prediction frame are P _N , P _N−1, and P _N−2 , respectively.
And P _N-1 −P _N > ΔP
And P _N-2 -P _N-1 and P _N-1 -P _N
Formula (6)
If the signs are equal, it is determined that the movement directions of the AF frames that are the prediction frames coincide with each other, and the process advances from step S912 to step S913. In step S913, it is determined that peak prediction is possible.

  Note that ΔP is a predetermined amount related to the amount of movement of the subject and is preferably a value of about 2 to 3 depths.

  If the moving directions are not equal, the process proceeds to step S914 and it is determined that the peak predicted position is not possible.

  However, in the following cases, it is determined that peak prediction is possible as an exception.

  When the movement amount of the frame determined to be the prediction frame is equal to or less than a predetermined value (for example, about 1 depth) that is regarded as not moving, all the obtained movement amounts are set to zero. If the previous movement amount of the prediction frame is also zero, the movement directions of the prediction frames coincide with each other, and the movement amount is set to zero and it is determined that the peak position can be predicted. Here, when the previous movement amount of the prediction frame is also zero, if the movement amount of the frame determined as the prediction frame in the previous determination is equal to or less than a predetermined value that is regarded as not moving, the movement This is the case when the quantity is zero.

  If it is determined that the peak position can be predicted, the scan center is predicted in step S715. The details are shown in FIG. First, a position at which the nearest AF evaluation value reaches a peak is selected from among the upper and middle frames (in the example shown in FIG. 11, from 00 frame to 12 frames) among the AF frames divided in step S1001. Then, in step S1002, a difference within the predetermined value (for example, within one depth) is selected, and an average value FP (n) is obtained.

In step S1003, the predicted position ObjP (n) serving as the center value of the scan AF in the next shooting is set to ObjP (n) = (FP (n−3) −3FP (n−2) + 2FP (n−1)) × FpAdj (n) + FP (n-1) Formula (7)
I ask.

  Here, FP (n-3), FP (n-2), and FP (n-1) use the peak position value of the AF evaluation value obtained in the scan of S411 in the AF frame selected in S1013.

  The above processing is performed only when an area having a normal size is designated as the AF frame. When the size of the face area detected by the face detection circuit 36 is smaller than the prescribed amount, or when the photographer intentionally designates an area smaller than the prescribed amount, the above processing is not performed. Even if the size of the AF frame on the display does not change due to the electronic zoom, the above processing is not performed even when the number of pixels of the sensor included in the AF frame is smaller than the specified amount.

  By performing the above-mentioned processing, the continuous shooting speed is not lowered for a stationary subject, the adverse effect of focusing on the background without focusing on the moved main subject is prevented, and the main subject is reliably focused. Is possible. Further, as described above, the focus lens group 3 is driven based on the AF evaluation value signal in the entire frame, so that the subject is always present in the frame even if the subject moves within the frame, and the focus is adjusted. The position can be determined. In addition, it is possible to appropriately determine whether the subject is a stationary subject or a moving subject using the divided frames.

  The difference between the second embodiment and the first embodiment is that an AF frame setting method for following a moving subject is different.

  This setting method is shown in FIG.

  As shown in the figure, 11 frames, which are AF frames for following a moving subject, are set to a size that is about four times the area ratio of 11 frames in FIG. This is to prevent the moving subject to be photographed from protruding out of the 11 frames even if it moves within the screen in the vertical and horizontal directions.

  If there is a possibility that the tracking in 11 frames is insufficient, the stationary subject determination and the peak position prediction feasibility determination are performed in the same manner as in the first embodiment using information on the surrounding 8 frames.

  The operation procedure is the same as that of the first embodiment, but there are some differences, so the procedure will be described with reference to FIG.

  In step S401, it is checked whether or not it is the second continuous shooting. If it is the second continuous shooting (the value of the continuous shooting counter is 2), the process proceeds to step S1302, and if it is not the second continuous shooting, the process proceeds to step S403.

  In step S1302, the position of the focus lens 3 (peak position FP1) at the time of the first continuous shooting is set as the center ObjP2 of the scan range in the same manner as in the first embodiment using the information on the 11 frames.

  Note that the peak position FP1, the center ObjP2 of the scan range, and the like used here are all obtained from AF evaluation values obtained from the output signals of 11 frames in the scan of S411.

  If the setting of the scan range is completed, the process proceeds to step S411.

  In step S403, it is checked whether or not it is the third continuous shooting (the value of the continuous shooting counter is 3). If it is the third continuous shooting, the process proceeds to step S1304. If it is not the third continuous shooting, the process proceeds to step S1305.

  In step S1304, in the same manner as in the first embodiment, subject position prediction (prediction of peak position at the time of the third shooting) is performed by primary approximation from information regarding two in-focus positions, and the center position ObjP3 of the scan range. Is obtained from equation (1).

  A scan range is set based on the center position ObjP3 calculated in this way, and the subject image is shifted from the previous scan range in the moving direction.

  Thereafter, the process proceeds to step S411.

  In step S1305, the object position prediction (prediction of the peak position at the time of the current photographing) is obtained from equation (2) by secondary approximation from the information about the in-focus position three times as in the first embodiment.

  A scan range is set based on the center position ObjP4 calculated in this manner, and the subject image is shifted from the previous scan range in the moving direction.

  In step S1306, the absolute value of the difference between the in-focus position FP3 of the third image obtained from the information on the 11th frame and the center position ObjP4 of the scan range at the time of the fourth image is obtained. The amount of movement in the optical axis direction.

  In step S1307, the amount of movement of the subject in the optical axis direction based on the information on the 11 frames obtained in step S1306 is compared with a predetermined value to determine whether or not the subject has moved significantly in the optical axis direction. As a result, when the movement amount of the subject in the optical axis direction is larger than the predetermined value, the process proceeds to step S408, and the scan range is set. The setting method in this case is the same as in the first embodiment. Thereafter, the process proceeds to step S411.

  If the movement amount of the subject in the optical axis direction is smaller than the predetermined value, the process proceeds to step S409, where it is determined whether the subject is a stationary subject or a moving subject, and the scan range is set.

  When the scan in step S411 is completed, the focus lens group 3 is controlled to a position where the AF evaluation value of 11 frames has a peak in step S1312.

  Other processes are the same as those in the first embodiment.

  The first and second embodiments can be applied to AF during live view.

  In this way, by setting the size of the central frame where there is a high possibility that the main subject is present to be larger than other AF frames, the possibility that the main subject can be captured in the same frame increases and the accuracy is increased. A high AF evaluation value signal is obtained. For this reason, the accuracy of predicting the peak position and the accuracy of determining whether the stationary subject is a moving subject are improved, and an appropriate scan range can be set.

  A part of the above-described embodiments may be appropriately combined. When a software program that realizes the functions of the above-described embodiments is supplied from a recording medium directly to a system or apparatus having a computer that can execute the program using wired / wireless communication, and the program is executed. Are also included in the present invention. Therefore, the program code itself supplied and installed in the computer in order to implement the functional processing of the present invention on the computer can also realize the present invention. That is, the computer program itself for realizing the functional processing of the present invention is also included in the present invention. In this case, the program may be in any form as long as it has a program function, such as an object code, a program executed by an interpreter, or script data supplied to the OS. The storage medium for supplying the program may be, for example, a magnetic recording medium such as a hard disk or a magnetic tape, an optical / magneto-optical storage medium, or a nonvolatile semiconductor memory. As a program supply method, a computer program that forms the present invention is stored in a server on a computer network, and a connected client computer downloads and programs the computer program.

  According to the present embodiment, it is possible to provide an imaging apparatus, an imaging system, an imaging apparatus control method, a program, and a storage medium that are capable of high-precision focus control at low cost.

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

1 imaging device,
2 Zoom lens group 3 Focus lens group 4 Aperture 31 Shooting lens barrel 5 Solid-state image sensor (sensor)
6 Imaging circuit 7 A / D conversion circuit 8 Memory such as buffer memory (VRAM) for temporarily storing image signals
9 D / A conversion circuit 10 Image display device such as liquid crystal display device (LCD) 12 Memory for storing image data 11 Compression / decompression circuit 13 AE processing circuit 14 Scan AF processing circuit 15 CPU with built-in memory for calculation
DESCRIPTION OF SYMBOLS 16 Timing generator 17 Sensor driver 21 Aperture drive motor 18 The 1st motor drive circuit which drives and controls the aperture drive motor 21 22 The focus drive motor to drive 19 The 2nd motor drive circuit which drives and controls the focus drive motor 22 23 Zoom drive motor 20 Zoom drive Third motor drive circuit for driving and controlling the motor 23 24 Operation switch 25 EEPROM
26 battery 28 strobe light emitting unit 27 switching circuit for controlling flash emission 29 display element such as LED for warning display 30 speaker for voice guidance or warning 32 AF auxiliary light for driving AF auxiliary light 32 Drive circuit 33 AF auxiliary light 34 shake detection circuit 35 shake detection sensor 36 face detection circuit

Claims (9)

Driving means for driving the focus lens;
Setting means for setting a range for moving the focus lens;
The focus lens is moved within the range set by the setting means, the focus state is determined based on an output signal from the imaging means obtained while moving the range and the focus lens, and based on the determined focus state Control means for controlling the drive means to move the focus lens to a focus position where the subject image is in focus;
Prediction means for predicting the focus position of the focus lens in the next shooting based on the plurality of focus positions of the focus lens obtained by controlling the focus lens to the focus position multiple times by the control means When,
Determining means for determining whether the subject is a stationary subject or a moving subject;
The setting means sets the range centered on the focus position predicted by the prediction means, and sets the predicted focus position and a focus position for an image captured after the focus position is predicted. When the interval is equal to or smaller than a preset threshold value and the determination unit determines that the subject is a moving subject, a range wider than the range set when the threshold is exceeded is set. Focusing device.   2. The focus adjustment according to claim 1, wherein when the interval is equal to or less than the threshold, the setting unit sets the entire range in which a focus state can be determined while moving the focus lens as the range. apparatus.   The setting means sets the range so that focusing is obtained by the control means within a predetermined time except when the interval is equal to or less than the threshold. The focus adjustment device described in 1.   The determining means determines whether the subject is a stationary subject or a moving subject based on a focus state corresponding to an output signal from each of the imaging means corresponding to a plurality of focus detection areas set in the photographing screen. The focus adjustment apparatus according to any one of claims 1 to 3, wherein   5. The focus adjustment apparatus according to claim 4, wherein the control unit determines a focus state based on output signals from the imaging unit corresponding to a plurality of focus detection areas set in the shooting screen. .   The predicting means predicts a focus position in the next shooting based on a plurality of focus positions of the focus lens with respect to a plurality of images obtained by the continuous shooting in continuous shooting. The focus adjustment apparatus according to any one of claims 1 to 5.   The focus adjustment apparatus according to claim 6, wherein the predicting unit predicts an in-focus position in the next shooting, assuming that the amount of movement of the subject below a predetermined value is zero.   An imaging apparatus comprising: the focus adjustment apparatus according to claim 1; and an imaging unit. A setting step in which the setting means sets a range for moving the focus lens;
The control means moves the focus lens within the range set in the setting step, and determines the focus state based on an output signal from the imaging means obtained while moving the range and the focus lens. A control step of controlling the focus lens to move to a focus position where the subject image is in focus based on the focus state;
Based on a plurality of focus positions of the focus lens obtained by the control of the focus lens to a plurality of focus positions in the control step, the predicting means, the focus position of the focus lens in the next shooting A prediction process for predicting
The determination means includes a determination step of determining whether the subject is a stationary subject or a moving subject;
In the setting step, the range is set around the in-focus position predicted in the prediction step, and the predicted in-focus position and the in-focus position with respect to the image captured after the in-focus position is predicted. When the interval is equal to or smaller than a preset threshold and the subject is determined to be a moving subject by the determination step, a range wider than a range set when the threshold is exceeded is set. Focus adjustment method.

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