JP5451869B2 - Focus adjustment apparatus and method - Google Patents

Description

  The present invention relates to a focus adjustment device and a focus adjustment method used in an imaging device and the like, and more particularly to a focus adjustment device and a focus adjustment method for performing automatic focus adjustment based on an image obtained by photographing.

  In conventional focus adjustment control of a video camera or the like, a focus signal representing sharpness (contrast state) is detected from an image signal obtained by photoelectrically converting a subject image by an image sensor, and a focus lens is based on the focus signal. The TV-AF method for controlling the position is the mainstream.

  However, when a person is photographed by the TV-AF method, there is a problem that depending on the photographing condition and subject condition, the subject is not the person who is the main subject but the background is high in contrast. In order to solve such a problem, an imaging apparatus having a face detection function is known. In recent years, a focus detection area (AF area) is set so that a detected face area is included, and a focus detection method (see, for example, Patent Document 1) or a human eye is detected, and based on the result. A method of performing focus detection (see, for example, Patent Document 2) has been proposed.

  In the case of focus detection using the face recognition function described above, an AF area is set corresponding to the detected face position in order to focus on the face detected by the face detection function. On the other hand, when the face is not detected, the AF area is set at a predetermined fixed position in the shooting screen such as the center position of the shooting screen. Then, focusing control is performed based on the focus signal generated from the image signal in the set AF area.

  By the way, with the above-described face detection function, it may be difficult to recognize a face due to the influence of a change in the image of a main subject that is a person (hereinafter referred to as a main person subject) or the influence of camera shake of a photographer. Therefore, the face is not always detected. Especially in the case of video shooting, the main subject is often moving. If the main subject is turned sideways, or if another subject temporarily covers the main subject, Even if a human subject is detected immediately before, face detection will fail.

  Under these conditions, the AF signal and subject distance within the AF frame change frequently between when a face is detected and when it is not, so the focus signal fluctuates greatly, resulting in stable focusing. Can not do. In order to avoid such a problem, focus adjustment control is performed so that the focus lens position is maintained for a certain period so that the focus does not fluctuate even when a face is no longer detected.

JP 2006-227080 A JP 2001-215403 A

  However, the above prior art has the following problems.

  As described above, when the face is no longer detected, the control for holding the focus lens position for a certain period of time is effective when face recognition fails temporarily despite the presence of the main subject in the screen. .

  However, on the other hand, in video shooting, the main subject will move completely out of the screen during shooting, or the main subject will change until the camera changes direction (panning). Shooting situations that occur outside often occur. In this case, the focus lens position is maintained even though the main subject that was in focus is no longer on the screen. However, there was a problem that an unsightly moving image was recorded.

  The present invention has been made in view of the above problems, and in focus detection using the subject detection function, when the main subject can be detected but cannot be detected, the focus is stably adjusted. On the other hand, it is an object to prevent an unsightly moving image in which the entire screen is blurred from being recorded.

In order to achieve the above object, the focus adjustment apparatus of the present invention detects an image capturing unit that captures an image of an object and outputs an image signal, and detects a specific object in the image capturing screen based on the image signal obtained from the image capturing unit. And when the subject is detected by the subject detection means, the subject area detected by the subject detection means is set as a focus detection area, and the subject is detected by the subject detection means. If not, a setting unit that sets a predetermined region set in advance as a focus detection region, a generation unit that generates a focus signal from the image signal of the focus detection region set by the setting unit, and the generation unit And a focus adjustment unit that performs focus adjustment control by moving a focus adjustment member based on the focus signal generated by the focus adjustment unit, When the subject is detected by the subject detection means and transitions from the state in which the subject is not detected, when the degree of focus in the predetermined area is equal to or greater than a preset threshold, the subject is not detected and is set in advance. time, as compared with the case the focus degree before Symbol predetermined area is smaller than the preset threshold value, controls so as to reduce at least one of the driving amount and the driving speed of the focus adjusting member.

In addition, the focus adjustment method of the present invention includes an imaging process in which an imaging unit captures an image of a subject and outputs an image signal, and an object detection unit detects a specific image in the imaging screen based on the image signal obtained in the imaging process. A subject detection step for detecting a subject; and a setting unit that sets the region of the subject detected by the subject detection step as a focus detection region when the subject is detected by the subject detection step; When the subject is not detected in the step, a setting step for setting a predetermined region set in advance as a focus detection region, and a generation unit generates a focus from the image signal of the focus detection region set in the setting step. A generation step of generating a signal, and a focus adjustment unit moves the focus adjustment member based on the focus signal generated by the generation step, thereby controlling the focus adjustment. A focus adjustment step to be performed, and in the focus adjustment step, when the subject is detected by the subject detection step and the state is not detected, a focus degree of the predetermined region is set in advance. equal to or greater than the threshold value, the time the object is set in advance from no longer being detected, compared with the case the focus degree before Symbol predetermined area is smaller than a predetermined threshold, the driving amount of the focus adjusting member and the driving Control to reduce at least one of the speeds .

  According to the present invention, in the focus detection using the subject detection function, when the main subject can be detected but cannot be detected, the entire screen is blurred while stably focusing. It is possible to prevent the image from being recorded.

It is a block diagram which shows the structure of the video camera in embodiment of this invention. It is a flowchart which shows the whole flow of the focus adjustment control in the 1st Embodiment of this invention. It is a flowchart which shows the detail of TV-AF control performed in FIG. It is a flowchart which shows the detail of the micro drive operation performed in FIG. It is a flowchart which shows the detail of the hill-climbing drive operation | movement performed in FIG. It is the figure which showed the movement of the focus lens in the micro drive mode in the 1st Embodiment of this invention. It is the figure which showed the movement of the focus lens in the hill-climbing drive mode. It is a flowchart which shows the whole flow of the focus adjustment control in the 2nd Embodiment of this invention.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram illustrating a configuration of a video camera as an example of an imaging apparatus according to an embodiment of the present invention. Note that although a video camera is described in this embodiment mode, the present invention can also be applied to other imaging devices that can acquire moving images, such as a digital still camera.

  In FIG. 1, 101 is a first fixed lens, 102 is a variable magnification lens that moves in the optical axis direction and performs variable magnification, and 103 is a diaphragm. Reference numeral 104 denotes a second fixed lens, and reference numeral 105 denotes a focus compensator lens (hereinafter referred to as “focus lens”) that has both a function of correcting the movement of the focal plane due to zooming and a focusing function (hereinafter referred to as “focus lens”). ). The first fixed lens 101, the variable magnification lens 102, the diaphragm 103, the second fixed lens 104, and the focus lens 105 constitute an imaging optical system.

  Reference numeral 106 denotes an image pickup element including a plurality of pixels each having a photoelectric conversion unit, which is configured by a CCD sensor or a CMOS sensor. In this pixel, a subject image can be photoelectrically converted to obtain a captured image. Reference numeral 107 denotes a CDS / AGC / AD conversion circuit that samples the output of the image sensor 106, adjusts the gain, and digitizes the output. A camera signal processing circuit 108 performs various image processing on the output signal from the CDS / AGC / AD conversion circuit 107 to generate an image signal.

  Reference numeral 109 denotes a display device composed of an LCD or the like, which is a display device that displays an image signal from the camera signal processing circuit 108, and 110 is a recording device. Recording is performed on a recording medium such as a semiconductor memory.

  Reference numeral 111 denotes an AF gate that passes only signals in a region (focus detection region) used for focus detection among output signals of all pixels from the CDS / AGC / AD conversion circuit 107. The focus signal processing circuit 112 generates a high frequency component from the image signal that has passed through the AF gate 111, a luminance difference component generated from the high frequency signal (difference between the maximum value and the minimum value of the luminance level of the signal that has passed through the AF gate 111), and the like. Extract and generate a focus signal. The focus signal is output to the camera / AF microcomputer 114. Note that the focus signal represents the sharpness (contrast state) of the image generated based on the output signal from the image sensor 106, but the sharpness changes depending on the focus state of the image pickup optical system. The signal represents the focus state of the imaging optical system.

  A face detection processing circuit (subject detection means) 113 performs face detection processing on the image signal and detects subject information (reliability indicating the size, position, and likelihood of the face of the person in the shooting screen). It is. The face detection processing circuit 113 transmits the detection result to a camera / AF microcomputer 114 described later. Based on the transmitted detection result, the camera / AF microcomputer 114 sets the focus detection area so as to include the detected face area, and transmits information to the AF gate 111. As a face recognition process, for example, a method is known in which a skin color region is extracted from the gradation color of each pixel represented by image data, and the face is detected with a matching degree with a face contour plate prepared in advance. ing. In addition, there is a method of detecting a face by extracting feature points of a face such as eyes, nose and mouth using a known pattern recognition technique, but the present invention is not limited to face recognition processing. Any method may be used.

  Reference numeral 114 denotes a camera / AF microcomputer that controls a focus lens driving source 116 (to be described later) based on the output signal of the focus signal processing circuit 112 to drive the focus lens 105 and outputs an image recording command to the recording device 110.

  Reference numeral 115 denotes a variable power lens driving source including an actuator for moving the variable power lens 102 and its driver, and 116 denotes a focus lens driving source including an actuator for moving the focus lens 105 and its driver. The zoom lens drive source 115 and the focus lens drive source 116 are configured by actuators such as a stepping motor, a DC motor, a vibration motor, and a voice coil motor.

<First Embodiment>
Next, the outline of the focus adjustment control performed by the camera / AF microcomputer 114 in the first embodiment of the present invention will be described with reference to FIGS. This AF control is executed according to a computer program stored in the camera / AF microcomputer 114. In the following description, the AF frame indicating the focus detection area set in the face area detected by the face detection processing circuit 113 is “face frame”, and the AF frame indicating the focus detection area set in a predetermined area on the screen is displayed. This is called “normal frame”.

  In FIG. 2, in step S11, first, a focus signal of a normal frame is acquired. Next, in step S12, information on the face detection processing result (face detection result) is acquired from the face detection processing circuit 113. In step S13, it is determined whether or not a face has been detected from the face detection result acquired in step S12. If not detected, the process proceeds to step S23, and if detected, the process proceeds to step S14.

  In step S14, a face frame for acquiring a focus signal is set in the face area detected in step S13. In step S15, the focus signal of the face frame set in step S14 is acquired. In step S16, since a face is currently detected, a face frame is set as an AF frame for TV-AF control described later. As an AF frame for TV-AF control, in addition to this face frame, an AF frame including a larger area is set to be overlapped in order to stabilize the AF operation, and the respective focus signals are weighted and used. This method may be used.

  In step S17, a face frame setting flag indicating that the face is currently detected is set, and in step S18, the focus position holding flag used for determining whether to hold the focus position is cleared. This is to perform focus adjustment by TV-AF control without holding the focus position while the face can be detected. Thereafter, the process proceeds to step S19.

  On the other hand, if it is determined in step S13 that no face is detected, it is determined in step S23 whether a face frame setting flag is set. If it is set, it means that the face has been detected until immediately before, so that the process proceeds to step S24 on the assumption that the face has been detected and the face cannot be detected.

  In step S24, first, the face frame setting flag is cleared because no face is detected. In step S25, in order to determine whether or not the entire screen is blurred, the focus degree of the focus signal of the normal frame acquired in step S11 is calculated. The degree of focus may be determined based on the level of the focus signal, but it should be noted that the level of the focus signal varies depending on the contrast of the captured image. Therefore, in order to more appropriately determine the in-focus level, it is more desirable to use a technique such as using a ratio between the focus signal and the maximum value of the luminance difference component extracted by the focus signal processing circuit 112, for example. The maximum value of the luminance difference component corresponds to the maximum value of the contrast of the captured image. Therefore, by dividing the focus signal by the maximum value of the luminance difference component, the focus signal can be normalized with respect to the magnitude of the contrast of the captured image, and used as a simple index of focus. be able to. Since the higher the simple focus level is, the closer the focus is, it is possible to determine the focus level based on the magnitude. Furthermore, it is possible to determine whether or not the entire screen is out of focus by setting the normal frame for calculating the degree of focus large so as to include most of the screen.

  In step S26, it is determined whether or not the focus degree of the normal frame is equal to or greater than a predetermined threshold value. If the threshold value is exceeded, the screen is not so blurred, and the face cannot be detected, but the main subject is still in the screen or there is another subject that is close to the focus even if it does not exist. It will exist in the screen. In such a case, it is better to maintain the focus state without moving the focus lens 105 suddenly as a moving image. In this case, therefore, a focus position holding flag for holding the focus lens position is set in step S27. In step S28, the focus position holding time counter for counting the time for which the focus position is held is reset to 0, and the process proceeds to step S19.

  On the other hand, if it is determined in step S26 that the focus level of the normal frame is smaller than the predetermined threshold value, the screen is out of focus, so focus adjustment is started immediately and an unsightly moving image is recorded. It is necessary to prevent it from being done. Therefore, the process proceeds to step S32 to clear the focus position holding flag, and in step S33, a normal frame is set as an AF frame for TV-AF control, and the process proceeds to step S19. The normal frame set in step S33 is set in a predetermined area on the screen. However, the normal frame does not necessarily have to include most of the screen used in step S11, and may be a frame only near the center of the screen. These frames may be superposed. When a plurality of frames are used in this way, a technique such as using each focus signal by weighted addition may be used.

  If it is determined in step S23 that the face frame setting flag is not set, it means that the face has not been detected before that, and the process proceeds to step S29. In step S29, it is determined whether the focus position holding flag is set. If not set, in order to perform TV-AF control in the normal frame, the process proceeds to step S33, the normal frame is set, and the process proceeds to step S19. On the other hand, if it is determined in step S29 that the focus position holding flag is set, the focus position holding time counter is incremented (incremented by 1) in step S30. In step S31, it is determined whether or not the time for holding the focus position has continued for a predetermined time by comparing the counter with a predetermined threshold value. If it is smaller than the threshold value, the process proceeds to step S19 to hold the focus position as it is. On the other hand, if it is equal to or greater than the threshold value, the process proceeds to step S32 to clear the focus position holding flag, and in step S33, the normal frame is set as the AF frame so that TV-AF control is performed in the normal frame, and step S19. Proceed to

  In step S19, it is determined whether the focus position holding flag is set. As described above, the focus position holding flag is set (step S27) when the face is detected and the normal frame cannot be detected, and the normal frame has a focus level equal to or greater than the threshold. It is. If the focus position holding flag is set, the focus lens position is held in step S22, and the process returns to step S11.

  On the other hand, since the focus position is not held when the focus position holding flag is not set, the focus signal of the AF frame for TV-AF set up to this point is acquired in step S20. That is, if it is determined in step S13 that a face is detected, the face frame set in step S16 is used for TV-AF control. On the other hand, when the face is detected and the normal frame is not detected, and the focus level of the normal frame is lower than the threshold value, the normal frame set in step S33 is used for TV-AF control. Furthermore, the normal frame set in step S33 is also used for TV-AF control when a predetermined time has elapsed since the face was no longer detected. In step S21, focus adjustment is performed by TV-AF control using the acquired focus signal. The detailed operation of the TV-AF control in step S21 will be described later with reference to FIG. Then, it returns to step S11.

  As described above, according to the first embodiment, when the face can be detected but cannot be detected, the focus lens 105 is set in accordance with the focus degree of the normal frame set in the predetermined area on the screen. Change the behavior. By performing such control, it is possible to perform focus adjustment control so that the entire screen is not blurred while stably performing focusing during moving image shooting.

  FIG. 3 is a flowchart showing the TV-AF control performed in step S21.

  In FIG. 3, in step S <b> 101, it is determined whether or not the focus lens 105 is in a minute drive mode for driving a minute amount. If not, the process proceeds to step S <b> 108.

  On the other hand, if it is in the minute driving mode, the process proceeds to step S102, and a minute driving operation for moving the focus lens 105 by a small amount is performed. Details of the minute driving operation in step S102 will be described later with reference to FIG. In step S103, it is determined whether or not in-focus determination is performed by the minute driving operation in step S102. If in-focus determination is performed by the minute driving operation, the process proceeds to step S106, and if not, the process proceeds to step S104. . In step S104, it is determined whether or not the direction is determined by the minute driving operation in step S102. If the direction can be determined, the process proceeds to step S105, and the mode shifts to a hill-climbing operation mode in which the focus lens 105 is moved at a high speed in the direction in which the focus signal increases. If the direction cannot be determined, the minute drive mode is continued. In step S106, the focus signal level at the time of in-focus is stored in the memory, and then the process proceeds to step S107 to enter the restart determination mode. Here, the restart determination mode is a process of determining whether or not to perform micro-driving again for direction determination, which is performed in steps S116 and S117 described later.

  In step S108, it is determined whether or not the hill-climbing drive mode is set. If the hill-climbing drive mode is not set, the process proceeds to step S113.

  On the other hand, in the case of the hill-climbing drive mode, the process proceeds to step S109, and a hill-climbing drive operation is performed in which the focus lens is moved at a higher speed than in the minute drive operation in the direction in which the focus signal increases. The detailed operation of the hill-climbing driving operation in step S109 will be described later with reference to FIG. In step S110, it is determined whether or not the peak of the focus signal has been found by the hill-climbing drive operation in step S109. If the peak of the focus signal is found, the process proceeds to step S111. Continue. In step S111, after the focus lens position where the focus signal has reached its peak is set as the target position, the focus lens 105 is moved toward the set target position, and the process proceeds to step S112 to shift to the stop mode.

  In step S113, it is determined whether or not it is the stop mode. If it is not the stop mode, the process proceeds to step S116, and if it is the stop mode, the process proceeds to step S114. In step S114, it is determined whether or not the focus lens 105 has returned to the target position where the focus signal set in step S111 reaches a peak. If not, the process returns to step S101 to continue the stop mode. When returning to the target position, the process proceeds to step S115, and the process proceeds to the minute drive mode for focusing determination.

  In the restart determination mode, the process proceeds to step S116, where the current focus signal level is compared with the focus signal level held in step S106, and it is determined whether or not the fluctuation amount is larger than a predetermined value. Here, if it is determined that the fluctuation amount is large, the process proceeds to step S117 to shift to the minute drive mode for direction determination, and if not, the restart determination mode is continued.

  Next, the minute driving operation performed in step S102 will be described with reference to FIGS.

  In the minute driving operation, first, the focus lens 105 is minutely driven alternately on the close side and the infinite side. A reference position for driving to the near side / infinite side is called a vibration center, and a driving amount for driving to the near side / infinite side with respect to the vibration center is called a vibration amplitude. Then, the focus signals on the near side and the infinite side are compared, and if the focus signal level on the near side is high, the vibration center is moved to the close side, and if it is opposite, the vibration center is moved to the infinite side. The amount of movement at this time is called the center movement amplitude.

  The time course of the focus lens operation in this minute driving is shown in FIG. The upper part of the figure represents the vertical synchronizing signal of the video signal, the horizontal axis of the lower part of the figure represents time, and the vertical axis represents the position of the focus lens 105.

Focus signal EV _A to the charge accumulated in the image pickup device 106 at the time of the label A is incorporated into the camera / AF microcomputer 114 at time _{T A.} Further, the focus signal EV _B for the electric charge accumulated in the image sensor 106 at the time of label B is taken into the camera / AF microcomputer 114 at time T _B. At time TC, the focus signals EV _A and EV _B are compared, and the center of vibration is moved only when EV _B is large. Here, the movement of the focus lens 105 is set to a movement amount that cannot be recognized on the screen on the basis of the depth of focus.

In FIG. 4, in step S201, it is determined whether the counter indicating the operation state of minute driving is currently 0. If so, the process proceeds to step S202, and if not, the process proceeds to step S203. Step S202 to hold the current focus signal level, step S202 hits the timing _{T A} in FIG. Accordingly, the focus signal held here is the focus signal EV _A for the electric charge accumulated in the image sensor 106 at the time of label A in FIG. 6, and is accumulated in the image sensor 106 when the focus lens 105 is on the infinity side. This is due to the video signal generated from the generated charges.

  In step S203, it is determined whether or not the current counter is 1. If so, the process proceeds to step S204, and if not, the process proceeds to step S209. In step S204, a vibration amplitude and a center movement amplitude for driving the focus lens 105 in step S208 described later are calculated. Usually, these amplitudes are generally set within the depth of focus. In step S205, the focus signal level on the infinite side held in step S202 is compared with the focus signal level on the near side held in step S210, which will be described later. If the former is large, the process proceeds to step S206. If the latter is large, the process proceeds to step S207. Transition.

  In step S206, the vibration amplitude and the center movement amplitude are added to obtain a drive amplitude. In step S207, the vibration amplitude is set as the drive amplitude. In step S208, driving is performed in an infinite direction based on the driving amplitude obtained in step S206 or step S207.

In step S209, it is determined whether or not the current counter is 2. If so, the process proceeds to step S210, and if not, the process proceeds to step S211. Step S210 to hold the current focus signal level, step S210 hits the timing of _{T B} in FIG. Accordingly, the focus signal held here is the focus signal EV _B for the electric charge accumulated in the image sensor 106 at the time of label B in FIG. 6, and is accumulated in the image sensor 106 when the focus lens 105 is on the closest side. This is due to the video signal generated from the generated charges.

  In step S211, the vibration amplitude and the center movement amplitude for driving the focus lens 105 in step S215 described later are calculated. Usually, these amplitudes are generally set within the depth of focus. In step S212, the focus signal level on the near side held in step S210 is compared with the focus signal level on the infinite side held in step S202 described later. If the former is large, the process proceeds to step S213. If the latter is large, the process proceeds to step S214. Transition. In step S213, the vibration amplitude and the center movement amplitude are added to obtain a drive amplitude. In step S214, the vibration amplitude is set as the drive amplitude. In step S215, driving is performed in the closest direction based on the driving amplitude obtained in step S213 or step S214.

  In step S216, it is determined whether or not the current direction determination mode is selected. If so, the process proceeds to step S217, and if not, the process proceeds to step S219.

  In step S217, it is determined whether a focal point exists in the same direction continuously for a predetermined number of times. If so, the process proceeds to step S218, and if not, the process proceeds to step S221. In step S218, it is determined that the direction has been determined.

  In step S219, it is determined whether the focus lens reciprocates in the same area a predetermined number of times. If so, the process proceeds to step S220, and if not, the process proceeds to step S221. In step S220, it is determined that the focus has been determined.

  In step S221, if the counter indicating the micro-driving operation state is 3, the counter is reset to 0, and if it is any other value, the counter is added.

  Next, the hill-climbing driving operation performed in step S109 in FIG. 3 will be described with reference to FIG.

  In step S301, the driving speed of the focus lens 105 is set. In step S302, it is determined whether the level of the current focus signal has increased from the previous time. If it has increased, the process proceeds to step S303, and if not, the process proceeds to step S304. In step S303, the focus lens 105 is hill-climbed in the same direction as the previous time based on the speed set in step S301. If the focus signal level has not increased, it is determined in step S304 whether the focus signal level has decreased beyond the peak. If the focus signal level has decreased beyond the peak, the process proceeds to step S305; Transits to step S306. In step S305, it is determined that the peak position has been found. In step S306, based on the speed set in step S301, the focus lens 105 is driven to climb in the opposite direction to the previous time. When step S306 is repeated in the hill-climbing drive mode, it means that the focus lens 105 is in the hunting state because a sufficient amount of change in the focus signal of the subject cannot be obtained.

  The operation of the focus lens 105 in this hill climbing drive is shown in FIG. In the figure, when the focus lens 105 is driven as indicated by A, the focus signal is increased, so that the hill-climbing drive in the same direction is continued. Here, when the focus lens 105 is driven in the range B, the focus signal decreases beyond the peak position. At this time, the hill-climbing driving operation is terminated assuming that the in-focus point exists, and after the focus lens 105 is returned to the peak position, the operation shifts to the minute driving operation. On the other hand, if the level of the focus signal decreases without exceeding the peak position as in C, the direction to be driven is reversed and the hill-climbing driving operation is continued.

  Thus, in the focus adjustment control by the TV-AF method, the focus signal is always maximized by moving the focus lens 105 while repeating the restart determination → micro drive → mountain climbing drive → stop → micro drive → restart determination. The in-focus state is maintained as follows.

  Furthermore, the focus signal used for the focus adjustment control can be effectively generated according to the face detection state. Therefore, it is possible to always provide a stable focus adjustment operation to the person who is the main subject intended by the photographer, especially during moving image shooting.

  Note that information indicating which face area information is being used to perform the focus adjustment operation may be displayed on the display device 109.

  In the first embodiment, the main AF area is a face area detected in the imaging screen (when a face is detected). In addition to the face, a specific subject is detected by image detection. It doesn't matter. For example, it may be possible to cut out and detect a subject image from the background. In addition, the position in the imaging screen may be determined by inputting the position in the imaging screen from an external input means or by detecting the line of sight of the photographer who is looking at the viewfinder.

<Second Embodiment>
Next, an outline of the focus adjustment control in the second embodiment of the present invention performed by the camera / AF microcomputer 114 will be described with reference to FIG. In FIG. 8, the same processes as those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

  In the first embodiment, when the focus degree of the normal frame is equal to or greater than the threshold value in step S26 of FIG. 2, the focus lens position is held for a predetermined time. By doing so, the appearance of the moving image is improved when the main subject is still present in the screen or when another subject close to the focus is present in the screen. On the other hand, in the second embodiment, when the focus degree of the normal frame is equal to or greater than the threshold value, instead of holding the focus lens position, the driving amount and driving in the minute driving mode of TV-AF control are performed. Reduce the distance to the center of the quantity and the driving speed in hill-climbing mode. This is different from the first embodiment in that rapid movement of the focus lens 105 is suppressed.

  In FIG. 8, a face is detected (YES in step S13), and after setting the face frame setting flag in step S17, a focus movement suppression flag is set in step S501 to suppress the movement of the focus lens 105 in the TV-AF control. To clear. The process of step S501 is performed instead of clearing the focus position holding flag for holding the focus position in step S18 of FIG. Thereafter, the process proceeds to step S505.

  On the other hand, if no face is detected (NO in step S13) and the focus level of the normal frame is equal to or greater than the threshold (YES in step S26), a focus movement suppression flag is set in step S502. In step S503, the focus movement suppression holding time counter for counting the time for suppressing the focus movement is reset to 0, and the process proceeds to step S505.

  If it is determined that the focus level of the normal frame is smaller than the threshold (NO in step S26), the focus movement suppression flag is cleared in step S504. In step S33, a normal frame is set as an AF frame for TV-AF control, and the process proceeds to step S505.

  If it is determined in step S23 that the face frame setting flag is not set (the face has not been detected before), the focus movement suppression time has elapsed (YES in step S31), and in step S504. Clear the focus movement suppression flag. In step S33, a normal frame is set as an AF frame for TV-AF control, and the process proceeds to step S505.

  In step S505, the focus signal of the AF frame for TV-AF set in step S16 or step S33 is acquired. In step S506, it is determined whether the focus movement suppression flag is set. If set, the process proceeds to step S508, and the TV-AF control parameter for the focus movement suppression mode is set. Thereby, the movement of the focus lens 105 is suppressed. Note that the TV-AF control parameters are, for example, the driving amount in the minute driving mode, the center to the driving amount, the driving speed in the hill-climbing mode, and the like. In the focus movement suppression mode, at least one of these TV-AF control parameters is made smaller than in normal TV-AF control, and the movement of the focus lens 105 is suppressed. Note that the TV-AF control parameter may be changed continuously according to the degree of focus calculated in step S25, or may be changed stepwise at a plurality of levels. In this case, the driving amount and speed parameters are set to be smaller as the degree of focus is higher.

  On the other hand, if it is determined in step S506 that the focus movement suppression flag is not set, it is not necessary to suppress the movement of the focus lens. Therefore, the TV-AF control parameter used in normal TV-AF control in step S507. Set.

  After setting the TV-AF control parameters in step S507 or S508, the process proceeds to step S21. In step S21, focus adjustment is performed by the TV-AF control as described above using the focus signal acquired in step S505 and the TV-AF control parameter set in step S507 or S508, and then the process returns to step S11. .

  As described above, according to the second embodiment, when the face can be detected but cannot be detected, the focus lens 105 is set in accordance with the focus degree of the normal frame set in the predetermined area on the screen. Change whether or not to suppress movement. By performing such control, it is possible to perform focus adjustment control so that the entire screen is not blurred while stably performing focusing during moving image shooting.

<Other embodiments>
Note that the present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a camera head, etc.), or a device (for example, a digital video camera, a digital still camera, etc.) including a single device. You may apply to.

  The object of the present invention can also be achieved as follows. First, a storage medium (or recording medium) that records a program code of software that implements the functions of the above-described embodiments is supplied to a system or apparatus. Then, the computer (or CPU or MPU) of the system or apparatus reads and executes the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.

  Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also the following can be achieved. That is, when the operating system (OS) running on the computer performs part or all of the actual processing based on the instruction of the read program code, the functions of the above-described embodiments are realized by the processing. It is. Examples of the storage medium for storing the program code include a flexible disk, hard disk, ROM, RAM, magnetic tape, nonvolatile memory card, CD-ROM, CD-R, DVD, optical disk, magneto-optical disk, MO, and the like. Can be considered. Also, a computer network such as a LAN (Local Area Network) or a WAN (Wide Area Network) can be used to supply the program code.

DESCRIPTION OF SYMBOLS 101 1st fixed lens 102 Variable magnification lens 103 Aperture 104 2nd fixed lens 105 Focus compensator lens 106 Image pick-up element 107 CDS / AGC / AD conversion circuit 108 Camera signal processing circuit 109 Display apparatus 110 Recording apparatus 111 AF gate 112 Focus signal processing circuit 113 face detection processing circuit 114 camera AF microcomputer 115 variable power lens drive source 116 focus lens drive source

Claims (6)

  Imaging means for photographing a subject and outputting an image signal;
  Subject detection means for detecting a specific subject in a shooting screen based on an image signal obtained from the imaging means;
  When the subject is detected by the subject detection unit, the region of the subject detected by the subject detection unit is set as a focus detection region, and when the subject is not detected by the subject detection unit, Setting means for setting the set predetermined area as a focus detection area;
  Generating means for generating a focus signal from the image signal of the focus detection area set by the setting means;
  Focus adjusting means for performing focus adjustment control by moving a focus adjusting member based on the focus signal generated by the generating means;
  The focus adjustment unit detects the subject when the degree of focus of the predetermined area is equal to or greater than a preset threshold when the subject detection unit makes a transition from a state in which the subject is detected to a state in which the subject is not detected. Control to reduce at least one of the drive amount and the drive speed of the focus adjustment member compared to a case where the degree of focus of the predetermined area is smaller than the threshold value for a preset time after being stopped. Focus adjustment device characterized.   When the focus adjustment unit makes a transition from a state in which the subject is detected by the subject detection unit to a state in which the subject is not detected, the amount of movement of the focus adjustment member becomes smaller as the degree of focus in the predetermined region increases. The focus adjustment device according to claim 1, wherein the focus adjustment device is controlled as follows.   When the focus adjustment unit transitions from a state in which the subject is detected by the subject detection unit to a state in which the subject is not detected, the driving speed of the focus adjustment member becomes slower as the degree of focus in the predetermined region increases. The focus adjustment apparatus according to claim 1, wherein the focus adjustment apparatus is controlled as follows.   An imaging process in which the imaging means images the subject and outputs an image signal;
  A subject detection step in which a subject detection means detects a specific subject in the shooting screen based on the image signal obtained in the imaging step;
  When the subject is detected by the subject detection step, the setting unit sets the subject region detected by the subject detection step as a focus detection region, and the subject is not detected by the subject detection step. A setting step of setting a predetermined area set in advance as a focus detection area,
  A generating step for generating a focus signal from the image signal of the focus detection area set by the setting step;
  A focus adjustment unit having a focus adjustment step of performing focus adjustment control by moving a focus adjustment member based on the focus signal generated by the generation step;
  In the focus adjustment step, the subject is detected when the degree of focus of the predetermined area is equal to or greater than a preset threshold when the subject is detected by the subject detection step and transitions to a state in which the subject is not detected. Control to reduce at least one of the drive amount and the drive speed of the focus adjustment member compared to a case where the degree of focus of the predetermined area is smaller than the threshold value for a preset time after being stopped. A focusing method characterized.   The program for making a computer perform each process of the focus adjustment method of Claim 4.   A computer-readable storage medium storing the program according to claim 5.

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