JP2013140262A - Focusing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic focusing device and method capable of improving stability in focusing and also capable of reducing discomfort given to a photographer, at an AF control using a detection function of a predetermined subject.SOLUTION: A focusing device includes: means 113 for generating an AF evaluation value from an electric signal corresponding to a preset focus detection area including a predetermined subject; control means 114 for driving and controlling a focus lens 105 to adjust focus; and means 114 for determining existence of a movement of the subject in at least one of horizontal and vertical directions. The control means includes a first focus operation mode and a second focus operation mode different from the first focus operation mode with regard to a drive control mode of the focus lens and configured to perform a tracking drive operation corresponding to a distance change of the subject. If it is determined that there exists a predetermined movement of the subject, the control means restricts the second focus operation mode.

Description

The present invention relates to an automatic focus adjustment apparatus and method in an imaging apparatus that detects a subject area in a shooting screen and performs focus adjustment based on the detection result when a subject such as a person is included in an imaging target. About.

In the auto focus (AF) control of an imaging apparatus such as a video camera, the following TV-AF method is the mainstream. In this method, an AF evaluation signal indicating the sharpness (contrast state) of a video signal generated using an image sensor is generated, and the position of the focus lens that maximizes the AF evaluation value in the AF evaluation signal is searched. In addition, an imaging apparatus having a face detection function is known in order to stably focus on a main person subject when shooting a person. For example, there has been proposed an imaging apparatus that performs focus detection by setting a focus detection area including a recognized face detection area (see Patent Document 1). In addition, an imaging apparatus that detects the eyes of a person and performs focus detection based on the eyes has been proposed (see Patent Document 2).

JP 2006-227080 A JP 2001-215403 A

In face AF control, which detects a face from the above shooting screen and performs AF control on the detected face, when shooting in a crowd like a walk shot, the person grows and the It may move in the direction and quickly get out of the screen. In this case, even if a face is detected, it will be off the screen immediately, so if you perform face AF control on the detected face and focus on the responsiveness, it will appear flickering. As a result, focusing may become unstable. Also, if the person in the shooting screen moves fast, there will be a time lag due to the processing time to detect the face, so the actual face position will be misaligned with the detected face position, making it impossible to focus accurately. In addition, there is a possibility of focusing in the wrong direction. In particular, in the case of moving image shooting, this flicker may be recorded, which causes discomfort to the photographer.

Here, the following points can be cited as factors that make the focus appear to be largely flickering. That is, among the two types of operation modes of the TV-AF system described later (a micro-driving operation mode and a hill-climbing driving operation mode), the operation is performed in the hill-climbing driving operation mode despite being in focus. In some cases, the above fluffiness is noticeable. In this regard, the minute drive operation mode is an operation mode in which the focus lens is finely reciprocated so as not to see out of focus and the stability of the screen is emphasized. On the other hand, the hill-climbing drive operation mode is an operation mode that emphasizes responsiveness such as moving the focus lens at a high speed in order to quickly move from the blurred position to the in-focus position. Therefore, if the hill-climbing drive operation mode is mistakenly executed from the focused state, blurring will be conspicuous. As described above, if the focus is greatly fluctuated from the point of focus, the photographer will be uncomfortable.

An object of the present invention is to provide an automatic focus adjustment apparatus and method that can improve the stability of AF control of a face or the like in view of the above-described situation.

The automatic focus adjustment apparatus of the present invention includes an image sensor that photoelectrically converts light from a subject that has passed through an imaging optical system including a focus lens into an electric signal, and an electric signal output from the image sensor in an imaging screen. Detection means for detecting a predetermined subject; and generation means for generating an AF evaluation value from an electrical signal corresponding to a focus detection region set including the predetermined subject among electrical signals output from the image sensor; Control means for controlling the focus by driving the focus lens using the AF evaluation value obtained from the focus detection area set in the photographing screen, and at least one of the left and right and up and down directions of the subject based on the detection result by the detection means Subject movement determination means for determining the presence or absence of a predetermined movement in the direction of Then, the control means controls the focus lens to perform focus adjustment to perform focus adjustment. The first focus adjustment operation mode in which stability is emphasized, and the first focus adjustment operation mode are drive control modes of the focus lens. And a second focus adjustment operation mode emphasizing responsiveness for performing a follow-up driving operation corresponding to a change in the distance of the subject, and the subject movement determining means determines that the subject has not moved. The second focus adjustment operation mode is executed as focus lens drive control, and the second focus adjustment operation mode is limited when the subject movement determining means determines that the subject has moved.

The automatic focus adjustment method of the present invention includes an imaging step for photoelectrically converting light from a subject that has passed through an imaging optical system including a focus lens into an electrical signal, and an imaging screen from the electrical signal output in the imaging step. A detection step for detecting a predetermined subject in the image, and a generation step for generating an AF evaluation value from an electrical signal corresponding to a focus detection region set including the predetermined subject among the electrical signals output in the imaging step And a control step for controlling the focus by driving the focus lens using the AF evaluation value obtained from the focus detection area set in the shooting screen, and the detection result of the detection step, the left and right and up and down directions of the subject A subject movement determination step of determining whether or not there is a predetermined movement in at least one direction. In the control step, when the focus lens is driven and controlled to perform focus adjustment, the first focus adjustment operation mode in which stability is emphasized, and the first focus adjustment operation mode are drive control modes of the focus lens. And the second focus adjustment operation mode emphasizing responsiveness for performing a follow-up driving operation corresponding to a change in the distance of the subject can be executed, and it is determined in the subject movement determination step that the subject has not moved. The second focus adjustment operation mode is executed as focus lens drive control, and the second focus adjustment operation mode is limited when it is determined in the subject movement determination step that the subject has moved.

According to the present invention, when it is determined by subject movement determination that there is a predetermined movement in at least one of the left and right and up and down directions of the subject, the follow-up focusing on responsiveness corresponding to a change in the distance of the subject Limiting the drive operation as focus lens drive control is limited. Therefore, the stability of AF control of the face and the like can be improved, and the photographer's discomfort can be reduced.

The block diagram which shows the structure of a video camera provided with the automatic focus adjustment apparatus of this invention. The flowchart which shows the face AF control process in one Example of this invention. 5 is a flowchart showing subject movement monitoring processing in an embodiment of the present invention. The figure for demonstrating the micro drive operation mode in TV-AF process. The figure for demonstrating the hill-climbing drive operation mode in TV-AF process. The flowchart which shows the movement monitoring process of the to-be-photographed object in another Example. The figure which shows the example of a setting of a face frame and a normal frame.

A feature of the present invention is that the presence or absence of a predetermined movement in at least one of the left and right and up and down directions of the subject is determined from the detection result. If it is determined that there is no movement, a first emphasis on stability is provided. In place of the focus adjustment operation mode, the second focus adjustment operation mode emphasizing responsiveness is executed as drive control of the focus lens. If it is determined that there is the movement, the second focus adjustment operation mode is determined. It is characterized by restricting. Based on this concept, the focus adjustment apparatus and method of the present invention have the basic configuration as described in the section for solving the problems. As will be described in the first embodiment to be described later, the first focus adjustment operation mode is a mode including a minute drive operation in which focus adjustment is performed by reciprocally driving the focus lens by a predetermined drive amount, for example. In addition, the second focus adjustment operation mode, which is different from the first focus adjustment operation mode in the focus lens drive control mode, is, for example, in addition to the first focus adjustment operation mode, the focus lens is continuously moved in a predetermined direction. This is a mode including a hill-climbing driving operation in which the focus adjustment is performed by driving at a higher speed than the first focus adjustment operation mode.

Examples of the present invention will be described below. FIG. 1 shows a configuration of a video camera (image pickup apparatus) including an automatic focus adjustment apparatus according to an embodiment of the present invention. In the following embodiments, a video camera will be described, but the present invention can also be applied to other imaging devices such as a digital still camera.

<First embodiment>
In FIG. 1 showing the configuration of the main part of a video camera as an image pickup apparatus according to the first embodiment, 101 is a first fixed lens group, 102 is moved in the direction of the optical axis and zoomed to change the focal length. A variable magnification lens 103 can be made to stop. Reference numeral 104 denotes a second fixed lens group, and reference numeral 105 denotes a focus compensator lens (also referred to as a “focus lens”) having both a function of correcting the movement of the focal plane due to zooming and a focusing function. The first fixed lens group 101, the variable magnification lens 102, the stop 103, the second fixed lens group 104, and the focus lens 105 constitute an imaging optical system.

Reference numeral 106 denotes an image sensor as a photoelectric conversion element constituted by a CCD sensor or a CMOS sensor. The image sensor 106 captures a subject image formed by an imaging optical system including a focus lens and outputs an electrical signal by photoelectric conversion. Reference numeral 107 denotes a CDS / AGC circuit that samples the output of the image sensor 106 and adjusts the gain. A camera signal processing circuit 108 performs various image processing on the output signal from the CDS / AGC circuit 107 to generate a video signal. Reference numeral 109 denotes a monitor constituted by an LCD or the like, which displays a video signal from the camera signal processing circuit 108. A recording unit 115 records the video signal from the camera signal processing circuit 108 on a recording medium such as a magnetic tape, an optical disk, or a semiconductor memory.

Reference numeral 110 denotes a zoom drive source for moving the variable magnification lens 102. Reference numeral 111 denotes a focusing drive source for moving the focus lens 105. The zoom drive source 110 and the focusing drive source 111 are configured by actuators such as a stepping motor, a DC motor, a vibration motor, and a voice coil motor. Reference numeral 112 denotes an AF gate that passes only signals in an area used for focus detection (a focus detection area set to include a predetermined subject described later) in the output signals of all pixels from the CDS / AGC circuit 107. The AF signal processing circuit 113 extracts a high frequency component, a luminance difference component (difference between the maximum value and the minimum value of the luminance level of the signal that has passed through the AF gate 112) and the like from the signal that has passed through the AF gate 112, and outputs an AF evaluation signal. Generate. The AF evaluation signal is output to a camera / AF microcomputer (also simply referred to as “microcomputer”) 114. The AF evaluation signal represents the sharpness (contrast state) of the video signal generated based on the output signal from the image sensor 106, but the sharpness varies depending on the focus state of the imaging optical system. The AF evaluation signal is a signal representing the focus state of the imaging optical system.

The microcomputer 114, which is a control means, controls the operation of the entire video camera, and performs AF control for controlling the focusing drive source 111 to drive and control the focus lens 105. That is, the control means also performs focus adjustment by driving and controlling the focus lens using the AF evaluation value obtained from the focus detection area set in the photographing screen. The microcomputer 114 performs AF control (also simply referred to as “TV-AF”) in the TV-AF method as AF control. The face detection unit 116 performs known face detection processing on the video signal, detects a human face (predetermined subject) in the shooting screen, and transmits the detection result to the microcomputer 114. Based on the detection result, the microcomputer 114 transmits information to the AF gate 112 so as to add a face frame to an area including the face in the shooting screen. Here, when the faces of a plurality of persons are detected by the face detection unit 116, there is a main face determination processing unit that prioritizes according to the position of the face, the size of the face, or an instruction from the photographer. The face determined to be the highest priority by the processing unit is set as the main face (main subject). For example, the face selected by the photographer's instruction has the highest priority, and the determination is performed such that the priority is higher as the face position is closer to the center of the screen and the face size is larger. However, this is not the case. As face detection processing, for example, there is a method of extracting a skin color region from the gradation color of each pixel represented by image data and detecting the face with a matching degree with a face contour plate prepared in advance. There is also a method of performing face detection by extracting facial feature points such as eyes, nose and mouth using a known pattern recognition technique. In the present embodiment, the face detection processing method is not limited to the above-described method, and any method may be used.

Next, face AF control processing executed by the microcomputer 114 will be described. FIG. 2 is a flowchart showing face AF control processing executed by the microcomputer 114 in FIG. This process is executed in accordance with a computer program stored in the microcomputer 114, and is repeatedly executed, for example, at the readout cycle of the imaging signal from the imaging device 106 for generating one field image. In FIG. 2, first, the result of performing face detection processing on the latest video signal is acquired from the face detection unit 116 (Step 201). Next, in Step 202, if a face exists as a result of Step 201, the process proceeds to Step 205, and if there is no face, the process proceeds to Step 203. In Step 203, an area (also referred to as “AF frame”) is set by the AF gate 112 at a predetermined fixed position on the screen, a subject movement flag described later is cleared (Step 204), and TV-AF control is executed (Step 204). Step 209). On the other hand, in Step 205, an AF frame (face frame) is set at the position of the main face from the result detected by the face detection unit 116. Further, a predetermined AF frame (normal frame) that includes the face frame and does not follow the subject is set.

Next, subject movement monitoring processing, which is a feature of the present invention to be described later, is executed (Step 206), and when the subject movement flag is set in Step 207 in response to the result, TV-AF control to be described later is performed. The used hill-climbing transition counter is cleared (Step 208), the TV-AF control process (Step 209) is executed, and this process ends. If the subject movement flag is not set (No in Step 207), the TV-AF control process (Step 209) is executed. The TV-AF control process is a method that combines a well-known minute driving operation mode and a hill-climbing driving operation mode, which will be described in detail later, while driving the focus lens so that the AF evaluation value is maximized. This is a method of determining increase / decrease of the evaluation value and searching for a focal point.

A subject movement monitoring process (Step 206) in the present embodiment will be described. FIG. 3 is a flowchart of subject movement monitoring processing in this embodiment. First, in Step 301, a threshold value for determining that the subject is moving from the face size is calculated. This is because the change varies depending on the face size even with the same movement amount. This threshold may be set to 25% of the face size based on experience and may be changed depending on the face size. Next, the amount of movement of the face position is calculated (Step 302). The amount of movement of the face position is the difference between the current detected face center position and the previous detected face center position in which the face position history is stored in a volatile memory or the like (not shown). Is calculated and obtained. Here, although the center position of the face detected last time is used, in order to calculate a stable movement amount when the subject always moves, for example, the average value of the center position of the past several times and the current You may calculate the difference with the center position with the detected face. In addition, the X direction and the Y direction may be combined, or in the case where the aspect ratio of 16: 9 is increased as high-definition shooting increases, only the X direction may be considered. Then, the movement amount of the face position calculated in Step 302 is compared with the threshold value of the movement amount calculated in Step 301 (Step 303). When the movement amount of the face position exceeds the movement amount threshold value (Yes in Step 303), the subject movement flag is set (Step 305). When the movement amount of the face position is equal to or smaller than the movement amount threshold value (No in Step 303), the subject movement flag is cleared (Step 304).

This comparison processing in Step 303 is a feature of the present invention. When the movement of the face position in the left-right or up-down direction is large, it is conceivable that the person is off the screen. In addition, there is a possibility that the difference between the person and the face frame to be set becomes large. At that time, if a different subject is focused and the entire screen is in focus and the mode is shifted to the hill-climbing drive operation mode, the face AF control becomes unstable. In addition, when a person moves fast, there is a possibility that an image will flow, resulting in low contrast. At that time, if the hill-climbing drive operation mode is entered while the entire screen is in focus, the face AF control becomes unstable. Therefore, it is necessary to limit the hill-climbing drive operation mode.

FIG. 4 is a diagram for explaining the minute driving operation mode of the focus lens 105 executed in Step 209 in the TV-AF process of FIG. In FIG. 4, the horizontal axis indicates time, and the vertical axis indicates the position of the focus lens 105. In the upper part of the figure, a vertical synchronizing signal of the video signal is shown. As shown in FIG. 4, the AF evaluation value EV _A for the electric charge (indicated by the slanted ellipse in the figure) accumulated in the image sensor 106 during the period _A is taken in at time TA, and during the period B, the image sensor The AF evaluation value EV _B for the electric charge accumulated in 106 is taken in at time T _B. Also, the AF evaluation value EV _C for the charge accumulated in the image sensor 106 during the period C is taken in at time T _C. Then, at time _{T D,} AF evaluation values _{EV A,} EV B, by comparing the EV _C, if EV A> EV _B and _EV C> EV _B, moves the driving (vibration) center of the minute drive. On the other hand, if EV _A <EV _B or EV _C <EV _B , the vibration center is not moved. As described above, the minute driving operation mode is used to determine the direction in which the AF evaluation value increases while moving the focus lens 105 or to search for the position (peak position) of the focus lens 105 where the AF evaluation value is the largest. is there. It should be noted that the control for finely driving the focus lens 105 to determine whether or not the in-focus state is based on the change in the AF evaluation value can also be referred to as in-focus confirmation control. Also, the control for finely driving the focus lens 105 to determine the in-focus direction from the change in the AF evaluation value can be referred to as in-focus direction discrimination control.

Next, the hill-climbing drive operation mode will be described with reference to FIG. In the hill-climbing driving operation mode, the focus lens 105 is driven at a high speed, and the peak position where the AF evaluation value obtained during that time reaches a peak or the vicinity thereof is detected. FIG. 5 shows the relationship between the movement of the focus lens 105 and the change in the AF evaluation value in the hill-climbing drive operation mode. Here, in the movement of A, since the AF evaluation value decreases beyond the peak, the existence of the peak position (focusing position) can be confirmed, and the hill-climbing driving operation mode is terminated and the mode is shifted to the minute driving operation mode. On the other hand, since there is no peak in the movement of B and it decreases monotonously, it can be determined that the drive direction of the focus lens 105 is incorrect. In this case, the driving direction is reversed and the hill-climbing driving operation mode is continued.

Then, the TV-AF process in Step 209 in FIG. 2 determines the in-focus direction by the minute driving operation mode, shifts to the hill-climbing driving operation mode, searches for the in-focus position by the hill-climbing driving operation mode, and again performs the minute driving operation mode. The process is shifted to and the focus confirmation is repeatedly executed. Here, the in-focus direction is determined in this minute driving operation mode, and it is determined whether or not the direction of moving the driving (vibration) center is continuously moving in the same direction when shifting to mountain climbing. That is, when the direction in which the drive center is moved is continuous, the count is incremented, and when the predetermined count value is exceeded, the hill-climbing drive operation mode is entered. This is the hill-climbing transition counter used in Step 208 in FIG. 2. By clearing this hill-climbing transition counter, it is possible to prohibit transition to the hill-climbing drive operation mode. In addition, the predetermined count value can be changed according to a simple degree of focus, and is 3 counts for large blur and 5 counts for small blur. The count value of increases. Here, in this embodiment, the transition to the hill-climbing driving operation mode is prohibited by clearing the hill-climbing transition counter, but even if the transition to the hill-climbing driving operation mode is restricted by increasing the predetermined count value described above, Good. For example, 5 counts for large blur and 10 counts for small blur.

Here, a setting example of the face frame and the normal frame will be described with reference to FIG. FIG. 7A shows an example in which a face frame A and a normal frame B are set in the imaging screen. The normal frame B is set around the center of the imaging screen, and the face frame A is set at the position where the face recognition is performed. In the present embodiment, the TV-AF control is performed by adding the AF evaluation value of the face frame A and the AF evaluation value of the normal frame B. As a result, even when the face frame A has a low contrast, stable face AF control can be realized with the AF evaluation value of the normal frame B. However, when the hill climbing restriction flag is not set, the face AF control may be performed using only the face frame A. FIG. 7B shows an example in the case where the TV-AF control is performed only with the normal frame set in Step 203. Here, when only the normal frame is set in the imaging screen, the face frame A is simply deleted from the state illustrated in FIG. 7A, the AF evaluation value is detected only by the normal frame B, and TV-AF is performed. Control can be performed. However, the present invention is not limited to this, and in consideration of the fact that the photographer often places the subject in the center of the imaging screen, a normal frame C smaller than the normal frame B may be further set around the center of the screen. Good. In this case, the TV-AF control is performed by adding the AF evaluation values acquired from the normal frame B and the normal frame C, respectively.

As described above, in the present embodiment, when the focus lens is driven and controlled to perform focus adjustment, the first focus adjustment operation mode including the minute drive operation mode and the tracking corresponding to the change in the distance of the subject. A second focus adjustment operation mode including a hill-climbing drive operation mode for performing the drive operation; When the subject movement determining means in the control means determines that there is a predetermined movement of the subject, the second focus adjustment operation mode is limited. Further, in this embodiment, the subject movement determination unit has a subject position storage unit (a volatile memory or the like) that holds a history of the position of the subject output from the detection unit, and the current subject position and the previous subject When the difference from the position is greater than or equal to a predetermined position difference, it is determined that the subject has moved. Further, in this embodiment, the predetermined position difference in the subject movement determination unit is changed according to the size of the subject output from the detection unit, and the predetermined position difference is increased as the subject size increases. Enlarge.

<Second embodiment>
A face AF control process executed by the microcomputer 114 in the second embodiment will be described. The face AF control process is the same as the process in the first embodiment (FIG. 2). FIG. 6 is a flowchart showing subject movement monitoring processing executed by the microcomputer 114 in FIG. Since this process is basically the same as the face AF control process in the first embodiment, the operations common to those in FIG. 3 are replaced with the same numerals as those in FIG. explain.

First, the movement amount threshold value is calculated from the face size (Step 601), and then the movement amount of the face position is calculated (Step 602). When the movement amount of the face position exceeds the movement amount threshold value (Yes in Step 603), the process proceeds to Step 610. When the movement amount of the face position is equal to or smaller than the movement amount threshold value (No in Step 603), the continuous movement count described later is cleared (Step 614). Then, the subject movement flag is cleared (Step 604), and the process ends. Next, in Step 610, a threshold value to be compared with the continuous movement count is set. If the continuous movement count is greater than the threshold (Yes in Step 611), the process proceeds to Step 613. If the continuous movement count is equal to or smaller than the threshold value (No in Step 611), the continuous movement count is incremented (Step 612), the subject movement flag is cleared (Step 604), and the process is terminated.

This is a characteristic part of the second embodiment of the present invention. In order to improve the accuracy of the determination and determine whether it is moving stably, it is determined whether it is determined that the movement is continuously performed. It is determined and it is determined whether or not there is a movement of the subject. That is, it is determined whether or not to limit the transition to the hill-climbing drive operation mode. Therefore, it is determined whether continuous movement is detected using the continuous movement count. In addition, the threshold value to be compared with the continuous movement counter may be set to 2 counts based on experience, but is not limited thereto. Further, not only the movement amount but also the continuity including the movement direction may be counted.

Next, in Step 613, it is determined whether or not the face position is outside a predetermined area of the screen. If the face position is outside the predetermined area of the screen (Yes in Step 613), the subject movement flag is set (Step 605). If the face position is within a predetermined area of the screen (No in Step 613), the subject movement flag is cleared (Step 604). This determination process is a characteristic part of the second embodiment of the present invention. Whether or not to set the subject movement flag according to the face position on the shooting screen, that is, whether to limit the hill-climbing drive operation mode. Determine whether or not. This is likely to be off the screen when the person moves from the center of the shooting screen to the end, but conversely, if the person moves from the end of the shooting screen to the center, the person may be the main subject. There is sex. For this purpose, it is determined whether or not the current face position is outside a predetermined area of the screen, and it is determined whether the person has moved, as a result of being moved, positioned at the center of the shooting screen or at the end of the shooting screen. And if it is outside the predetermined area of the screen that is determined to be likely to be off the screen, the subject movement flag is set and the transition to the hill-climbing drive operation mode is prohibited, and inadvertent flickering occurs To alleviate Here, the predetermined area of the screen is an area including the center position of the screen, and may be, for example, a fixed normal frame area that does not follow the person set in Step 205 (normal frame B in FIG. 7). Alternatively, for example, the center position of the screen may be set to 50% to 60% of the shooting screen.

As described above, in this embodiment, the subject movement determination unit in the control unit is a predetermined unit centered on the center position of the imaging screen and the difference between the current subject position and the previous subject position is greater than or equal to a predetermined position difference. If the current subject position is outside the range of the region, it is determined that the subject has moved.

As described above, in the embodiment of the present invention, in the face AF control, when it is determined that the movement of the person in at least one of the left and right and up and down directions is large, the shooting screen of the current face position is further displayed. According to the upper position, the transition to the hill-climbing drive operation mode is prohibited. Thus, stable face AF control can be realized, and the photographer's discomfort caused by fluff can be reduced.

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

The present invention has been described in detail based on the preferred embodiments thereof, but the present invention is not limited to these specific embodiments, and various forms within the scope of the present invention are also included in the present invention. included. A part of the above-described embodiments may be appropriately combined.

105 ... Focus lens, 106 ... CCD (imaging device), 113 ... AF signal processing circuit (generation means), 114 ... Camera / AF microcomputer (control means, subject movement determination means), 116 ... Face detection (Detection means)

Claims (6)

An image sensor that photoelectrically converts light from a subject that has passed through an imaging optical system including a focus lens into an electrical signal;
Detecting means for detecting a predetermined subject in a photographing screen from an electrical signal output from the image sensor;
Generating means for generating an AF evaluation value from an electric signal corresponding to a focus detection area set including the predetermined subject among the electric signals output from the image sensor;
A control means for performing focus adjustment by driving and controlling the focus lens using an AF evaluation value obtained from a focus detection area set in the photographing screen;
Subject movement determination means for determining the presence or absence of a predetermined movement in at least one of the left and right and up and down directions of the subject from the detection result by the detection means;
An autofocus device having
When the focus control is performed by driving the focus lens, the control means differs in the focus lens drive control mode between the first focus adjustment operation mode and the first focus adjustment operation mode. And a second focus adjustment operation mode for performing a follow-up drive operation corresponding to the second focus adjustment operation mode when the subject movement determination means determines that there is no movement of the subject. Is executed as focus lens drive control, and the second focus adjustment operation mode is limited when the subject movement determination means determines that the subject is moving. The first focus adjustment operation mode is a mode including a minute drive operation that performs focus adjustment by reciprocatingly driving the focus lens by a predetermined drive amount, and the second focus adjustment operation mode is the first focus adjustment operation mode. In addition to the focus adjustment operation mode, the focus lens is a mode including a hill-climbing drive operation in which the focus lens is continuously driven in a predetermined direction at a speed higher than that of the first focus adjustment operation mode. The automatic focusing apparatus according to claim 1. The subject movement determination unit includes a subject position storage unit that holds a history of the position of the subject output from the detection unit,
3. The automatic focus adjustment apparatus according to claim 1, wherein when the difference between the current subject position and the previous subject position is equal to or greater than a predetermined position difference, it is determined that the subject has moved. 4. The predetermined position difference in the subject movement determination unit is changed according to the size of the subject output from the detection unit, and the predetermined position difference is increased as the size of the subject increases. The automatic focusing apparatus according to claim 3. The subject movement determination means is configured such that a difference between the current subject position and the previous subject position is equal to or greater than a predetermined position difference, and the current subject position is outside a predetermined area centered on the center position of the imaging screen. 5. The automatic focus adjustment apparatus according to claim 3, wherein when it exists, it is determined that there is the movement of the subject. An imaging step for photoelectrically converting light from a subject passing through an imaging optical system including a focus lens into an electrical signal;
A detection step of detecting a predetermined subject in the shooting screen from the electrical signal output in the imaging step;
A generation step of generating an AF evaluation value from an electric signal corresponding to a focus detection region set including the predetermined subject among the electric signals output in the imaging step;
A control step of performing focus adjustment by driving and controlling the focus lens using an AF evaluation value obtained from a focus detection area set in the photographing screen;
A subject movement determination step for determining the presence or absence of a predetermined movement in at least one of the left and right and up and down directions of the subject from the detection result of the detection step;
An automatic focus adjustment method comprising:
In the control step, when the focus lens is driven and controlled to perform focus adjustment, the first focus adjustment operation mode differs from the first focus adjustment operation mode in the focus lens drive control mode, and the subject distance change And a second focus adjustment operation mode in which a follow-up driving operation corresponding to the second focus adjustment operation mode can be executed, and when it is determined in the subject movement determination step that the subject has not moved, the second focus adjustment operation mode. Is executed as focus lens drive control, and the second focus adjustment operation mode is limited when it is determined in the subject movement determination step that the subject has moved.

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