JP5247945B2 - IMAGING DEVICE, IMAGING DEVICE CONTROL METHOD, PROGRAM, AND STORAGE MEDIUM - Google Patents

Description

  The present invention relates to an imaging device mounted on an imaging device such as a camera, a control method for the imaging device, a program, and a storage medium.

  Conventionally, as an automatic focus adjustment method in an automatic focus adjustment apparatus such as a video camera, for example, the following is available. That is, a subject image is photoelectrically converted by an image sensor or the like to obtain a video signal, and a focus signal representing the sharpness of the screen is detected from the video signal. Then, a method (hereinafter referred to as a TV-AF method) in which automatic focus adjustment is performed by controlling the position of the focus lens so that the focus signal is maximized is the mainstream.

  However, when a person is photographed by the TV-AF method, there is a problem that depending on the photographing conditions and subject conditions, the subject is not the main subject but the background is high in contrast.

  In order to solve such a problem, the following imaging device having a face detection function is known. For example, a focus detection area (face frame) including a recognized face area is set to perform focus detection (Patent Document 1), or focus detection is performed by estimating the distance from the size of the face frame to the subject. A method (Patent Document 2) and the like have been proposed.

JP 2006-227080 A JP 2006-201282 A

  However, in the focus detection method using the face detection function described above, there is a problem in the time until detection of the in-focus position.

  Generally, the focus signal in the face frame detected by the face detection function has a low contrast and it is difficult to detect the maximum value. In the case of the above-mentioned Patent Document 1, focus detection is performed using a contour portion having a relatively high contrast in the detected face frame, but the contour portion is detected depending on the direction and moving direction of the subject. It is difficult to always capture in the face frame. In addition, depending on the size of the face frame, a focus signal with a sufficient contour portion may not be obtained, and a lot of time may be spent in detecting the in-focus position.

In Patent Document 2, the time until the detection of the in-focus position changes due to the accuracy of the face size. For example, when a person turns sideways, the size of the face frame may change due to a change in the area of the face. In this case, although the distance is the same, it is erroneously recognized that a change in the distance to the subject has occurred due to a change in the size of the face. Therefore, the estimation of the in-focus position is wrong, and time is spent until focus detection. Further, in the case of a photograph or a poster, it is possible to enlarge at a ratio different from the actual size of the face, which causes an erroneous estimation of the subject distance and spends a lot of time in detecting the in-focus position.

  In view of the above-described conventional problems, the present invention can improve the responsiveness of the focus adjustment operation to a specific subject such as a face and realize a stable focus adjustment operation, and control of the image pickup device It is an object to provide a method, a program, and a storage medium.

  In order to achieve the above object, an image pickup apparatus of the present invention detects an image of a subject in a shooting screen based on an image pickup unit that picks up a subject and outputs a video signal, and a video signal obtained from the image pickup unit. Subject image detection means, focus signal detection means for detecting a focus signal indicating the sharpness of the shooting screen from the video signal, and automatic focus adjustment means for adjusting the focus by moving a focus adjustment member in accordance with the focus signal The automatic focus adjustment means is configured to cause the focus adjustment member to reciprocate at a predetermined vibration amplitude to the near side and the infinity side so that a focal point exists in either the near side or the infinity side. A direction determination mode for determining a direction of whether to perform, a focus position determination mode for determining a focus position by driving the focus adjustment member in the direction determined from the direction determination mode and shifting from the direction determination mode; An amplitude increase mode in which the predetermined vibration amplitude of the focus adjustment member is increased when the specific subject image is detected by the subject image detection unit in the determination mode, compared to when the specific subject image is not detected. It is characterized by having.

  According to another aspect of the present invention, there is provided a method for controlling an imaging apparatus, including an imaging step of shooting a subject and outputting a video signal, and a subject image for detecting a specific subject image in a shooting screen based on the video signal obtained in the imaging step. A detection step, a focus signal detection step of detecting a focus signal indicating the sharpness of the shooting screen from the video signal, and an automatic focus adjustment step of performing focus adjustment by moving a focus adjustment member in accordance with the focus signal. In the method for controlling an imaging apparatus, the automatic focus adjustment step includes reciprocating the focus adjustment member to a close side and an infinite side with a predetermined vibration amplitude so that a focal point is set in either the close side or the infinite side. A direction determining step for determining a direction of existence, a focus position determining step for determining a focus position by moving from the direction determining step and driving the focus adjusting member in the direction determined for the direction; Direction judgment When the specific subject image is detected in the subject image detection step, an amplitude increasing step for increasing the predetermined vibration amplitude of the focus adjustment member as compared with a case where the specific subject image is not detected. It is characterized by having.

  According to the present invention, it is possible to improve the responsiveness of the focus adjustment operation to a specific subject such as a face and realize a stable focus adjustment operation.

It is a block diagram which shows the structure of the video camera (imaging device) which concerns on embodiment. It is a flowchart which shows the whole focus adjustment control in embodiment. It is a flowchart which shows the detail of TV-AF control. It is a flowchart which shows the detailed process of micro drive mode. FIG. 5 is a flowchart continued from FIG. 4. It is a figure which shows the focus lens 105 operation | movement of a micro drive mode. It is the schematic diagram which showed an example of the position of a fixed AF frame and the AF frame (face frame) at the time of face detection. It is the graph which showed the focus signal state of a face frame and a fixed frame. It is the graph which showed the change of the focus signal in a face frame. It is a flowchart which shows the detailed process at the time of a hill-climbing drive mode. It is the graph which showed operation | movement of the focus lens 105 at the time of the hill-climbing drive mode in embodiment.

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

[First Embodiment]
<Configuration of imaging device>
FIG. 1 is a block diagram showing the configuration of a video camera (imaging device) equipped with an automatic focus adjustment device according to an embodiment of the present invention. Note that although a video camera is described in this embodiment, the present invention can also be applied to other imaging devices such as a digital still camera.

  In FIG. 1, in this video camera, a first fixed lens 101, a variable power lens 102, a diaphragm 103, a second fixed lens 104, and a focus compensator lens 105 are sequentially arranged in the optical axis direction, and thereby an imaging optical system is arranged. Composed. The variable power lens 102 is a lens that moves in the optical axis direction to perform variable power. A focus compensator lens (hereinafter referred to as a focus lens) 105 is a lens that has both a function of correcting the movement of the focal plane accompanying zooming and a focusing function. An image sensor 106 is disposed behind the focus lens 105. The imaging element 106 is a photoelectric conversion element configured by a CCD sensor or a CMOS sensor.

  Further, this video camera includes a CDS / AGC / AD converter 107, a camera signal processing circuit 108, a display device 109, a recording device 110, an AF gate 111, a focus signal processing circuit 112, a face detection processing circuit 113, and a camera / AF microcomputer. 114.

  The CDS / AGC / AD converter 107 is a circuit that samples, gain adjusts, and digitizes the output of the image sensor 106. The camera signal processing circuit 108 is a circuit that performs various kinds of image processing on the output signal from the CDS / AGC / AD converter 107 to generate a video signal. The display device 109 is a device that displays the video signal from the camera signal processing circuit 108, and the recording device 110 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. Device. The AF gate 111 is a circuit that passes only signals in a region used for focus detection among output signals of all pixels from the CDS / AGC / AD converter 107.

  The focus signal processing circuit 112 extracts a high frequency component, 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 from the signal that has passed through the AF gate 111. Thus, the focus signal is generated. Here, 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. In other words, the signal represents the focus state of the imaging optical system.

  The face detection processing circuit 113 (an example of a detection unit) is a circuit that performs a known face recognition process on the image signal to detect a human face area in the shooting screen, and the detection result is represented by the camera / AF microcomputer 114. Send to. Based on the detection result, the camera / AF microcomputer 114 transmits information to the AF gate 111 so as to add an area used for focus detection to a position including the face area in the shooting screen.

  In the known face recognition process, for example, a skin color region is extracted from the gradation color of each pixel represented by image data, and a face is detected with a matching degree with a face contour plate prepared in advance, A method of performing pattern recognition from extracted facial feature points such as eyes, nose and mouth is known.

  Based on the output signal of the focus signal processing circuit 112, the camera / AF microcomputer 114 controls a focus lens driving source 116 described later to drive the focus lens 105 and outputs an image recording command to the recording device 110.

  The video camera also includes a variable magnification lens drive source 115 and a focus lens drive source 116. The zoom lens driving source 115 includes an actuator for moving the zoom lens 102 and its driver, and the focus lens driving source 116 includes 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.

<Overview of focus adjustment control>
Next, the outline of the focus adjustment control in the present embodiment executed by the camera / AF microcomputer 114 will be described with reference to FIGS. In the series of processes in FIG. 2, a process for setting a face detection flag is performed from the start of face detection when a face is detected until a predetermined time N. This flag is referred to in the processing of FIGS. 4, 5 and 10 described later, and the driving of the focus lens 105 is changed for a certain time from the start of face detection.

  FIG. 2 is a flowchart showing the entire focus adjustment control in the present embodiment, and mainly shows processing related to AF frame setting.

  In FIG. 2, first, in step S <b> 501, the position and size of a fixed AF (autofocus) frame for acquiring a focus signal that is the basis of TV-AF control is set from the focus signal processing circuit 112. At this time, the filter coefficient in the focus signal processing circuit 112 is set, and a plurality of band pass filters having different extraction characteristics are constructed. The extraction characteristic is the frequency characteristic of the bandpass filter, and the setting here means changing the setting value of the bandpass filter in the focus signal processing circuit 112.

  In the next step S <b> 502, the camera / AF microcomputer 114 acquires face detection processing result information from the face detection processing circuit 113. Hereinafter, an area located around the detected face is referred to as a face frame. However, in the present embodiment, description will be made assuming that the maximum number of extracted face frames is one.

  In subsequent step S503, the camera / AF microcomputer 114 determines whether or not a face has been detected from the information acquired in step S502. If detected, the process proceeds to step S504. If not detected, the process proceeds to step S512. .

  In step S504, the camera / AF microcomputer 114 resets a fixed AF frame to the detected face frame. In the case of a video camera, since processing is performed in synchronization with the vertical synchronization signal V of the video signal, in the subsequent step S505, the camera / AF microcomputer 114 has the same subject as the previous vertical synchronization signal V and the current subject. Determine whether. The determination criterion is determined by using a significant shift of the position of the AF frame.

  If the subject is the same, the process proceeds to step S509. If the subject is not the same, that is, if the face frame is switched or a new face is detected, the process proceeds to step S506. In step S506, the camera / AF microcomputer 114 resets the face detection time counter for detecting the face detection time to 0, and the process proceeds to step S507. In step S507, the camera / AF microcomputer 114 sets a face detection flag indicating that face detection has started.

  In the next step S508, the camera / AF microcomputer 114 starts the face detection time counter, and in the subsequent step S509, it is determined whether the value of the face detection time counter is less than N. The setting of the constant N will be described later. If the value of the face detection time counter is less than N, in step S510, the camera / AF microcomputer 114 performs processing to advance the value of the face detection time counter.

  On the other hand, if the value of the face detection time counter is greater than or equal to N, it is determined that a certain time has elapsed after the start of face detection, and the camera / AF microcomputer 114 clears the face detection flag in step S511. If the camera / AF microcomputer 114 determines in step S503 that no face has been detected, the camera / AF microcomputer 114 performs processing to clear the face detection flag in step S512, and further resets the face detection time counter to 0 in step S513. To do.

  The above processing is terminated, and in step S514, the focus signal of the designated AF frame is acquired. At this time, as the AF frame, a fixed AF frame is used when a face is not detected, and an AF frame of a face area is used when a face is detected.

  In the next step S515, the camera / AF microcomputer 114 performs focus adjustment by TV-AF control. The detailed operation here will be described with reference to FIG. Thereafter, the process returns to step S501.

  Next, detailed processing of the TV-AF control executed in step S515 in FIG. 2 will be described with reference to FIG.

  FIG. 3 is a flowchart showing details of the TV-AF control executed in step S515 of FIG.

  First, in step S601, the camera / AF microcomputer 114 determines whether the mode is the micro drive mode. If the mode is the micro drive mode, the process proceeds to step S602. If the mode is not the micro drive mode, the process proceeds to step S608.

In step S602, the camera / AF microcomputer 114 performs a minute driving operation, drives the focus lens 105 with a predetermined amplitude, and determines whether it is in focus or in which direction the focus is present. The detailed operation here will be described with reference to FIGS. Step S6
In 03, the camera / AF microcomputer 114 determines whether or not the focus determination is successful by the minute driving operation in step S602, and if successful, the process proceeds to step S606, and if not successful, the process proceeds to step S604.

  In step S604, the camera / AF microcomputer 114 determines whether or not the direction determination is successful by the minute driving operation in step S602. If the direction determination is successful, the process proceeds to step S605 to shift to the hill-climbing drive mode. If the direction determination is not successful, the process returns to step S501 and the minute drive mode is continued.

  In step S606, the camera / AF microcomputer 114 stores the focus signal level at the time of focusing in the memory in the camera / AF microcomputer 114, and then transitions to step S607 to shift to the restart determination mode.

  On the other hand, in step S608, the camera / AF microcomputer 114 determines whether the camera / AF microcomputer 114 is in the hill-climbing drive mode. If so, the process proceeds to step S609; otherwise, the process proceeds to step S613. . In step S609, the camera / AF microcomputer 114 performs a hill-climbing drive operation to drive the focus lens 105 to a hill-climb at a predetermined speed in a direction in which the focus signal increases. The detailed operation here will be described with reference to FIG.

  In subsequent step S610, the camera / AF microcomputer 114 determines whether or not the peak position of the focus signal has been found by the hill-climbing driving operation in step S609. If so, the process proceeds to step S611. If not, the process returns to step S501 to continue the hill-climbing drive mode. In step S611, the camera / AF microcomputer 114 sets the position of the focus lens 105 at which the focus signal has reached a peak as the target position, and then transitions to step S612 to shift to the stop mode.

  On the other hand, in step S613, the camera / AF microcomputer 114 determines whether the mode is the stop mode. If so, the process proceeds to step S614, and if not, the process proceeds to step S616. In step S614, the camera / AF microcomputer 114 determines whether or not the focus lens 105 has returned to the position where the focus signal peaks. If so, the process proceeds to step S615 to shift to the minute driving (focus determination) mode. If not, the process returns to step S501 and the stop mode is continued.

  On the other hand, in step S616, the camera / AF microcomputer 114 compares the current focus signal level with the focus signal level held in step S606, and determines whether or not the fluctuation amount is larger than a predetermined value. If it is determined that the amount of variation is large, the process proceeds to step S617 to shift to the minute driving (direction determination) mode. If not, the process returns to step S501 and the restart determination mode is continued.

<Details of micro drive mode>
Next, detailed processing in the micro drive mode executed in step S602 in FIG. 3 will be described with reference to FIGS.

  4 and 5 are flowcharts showing detailed processing in the minute drive mode executed in step S602 of FIG.

First, in step S701, the camera / AF microcomputer 114 determines whether the counter indicating the micro-driving operation state is currently 0. If so, the process proceeds to step S702, and if not, the process proceeds to step S703. . In step S702, the current focus signal level is held as processing when the focus lens 105 is on the close side. The focus signal here is based on a video signal generated from the charge accumulated in the image sensor 106 when the focus lens 105 is on the infinite side in step S710 described later.

  In step S703, the camera / AF microcomputer 114 determines whether or not the current counter is 1. If yes, the process proceeds to step S704, and if not, the process proceeds to step S709.

  In step S704, the camera / AF microcomputer 114 calculates a vibration amplitude and a center movement amplitude for driving the focus lens 105 in step S708, which will be described later. In subsequent step S704A, it is confirmed whether the face detection flag is set. Do. When the face detection flag is set, it is within a certain time after the start of face detection. Therefore, in step S704B, a value obtained by multiplying the calculation result in step S704 by the coefficient K is set as the calculation result. The values are set as a vibration amplitude and a center movement amplitude for driving the focus lens 105 used in step S708 described later. In general, these amplitudes are generally set within the depth of focus.

  In step S705 following step S704A, the camera / AF microcomputer 114 compares the infinite focus signal level held in step S702 with the close focus signal level held in step S710 described later. If the former is large, the process proceeds to step S706. If the latter is large, the process proceeds to step S707.

  In step S706, the sum of the vibration amplitude and the center movement amplitude is set as the drive amplitude, and in step S707, the vibration amplitude is set as the drive amplitude. In subsequent step S708, the camera / AF microcomputer 114 drives the focus lens 105 in an infinite direction based on the drive amplitude obtained in step S706 or step S707.

  On the other hand, in step S709, the camera / AF microcomputer 114 determines whether or not the current counter is 2. If so, the process proceeds to step S710, and if not, the process proceeds to step S711. In step S710, the current focus signal level is held as processing when the focus lens 105 is on the infinity side. The focus signal here is based on the video signal generated from the charge accumulated in the image sensor 106 when the focus lens 105 is in the closest side in step S702.

  In step S711, the camera / AF microcomputer 114 calculates a vibration amplitude and a center movement amplitude for driving the focus lens 105 in step S715, which will be described later. In subsequent step S711A, it is confirmed whether the face detection flag is set. Do. When the face detection flag is set, it is within a certain time after the start of face detection. Therefore, in step S711B, a value obtained by multiplying the calculation result in step S711 by the coefficient K is set as the calculation result. The values are set as a vibration amplitude and a center movement amplitude for driving the focus lens 105 used in step S715 described later. In general, these amplitudes are generally set within the depth of focus.

  In step S712, the camera / AF microcomputer 114 compares the close focus signal level held in step S710 with the infinite focus signal level held in step S702 described later. If the former is large, the process proceeds to step S713. If the latter is large, the process proceeds to step S714.

In step S713, the sum of the vibration amplitude and the center movement amplitude is set as the drive amplitude, and in step S714, the vibration amplitude is set as the drive amplitude. In subsequent step S715, the camera / AF microcomputer 114 drives the focus lens 105 in the closest direction based on the drive amplitude obtained in step S713 or step S714.

  In step S716, the camera / AF microcomputer 114 determines whether the current mode is the direction determination mode. If so, the process proceeds to step S717, and if not, the process proceeds to step S719. In step S717, the camera / AF microcomputer 114 determines whether a focal point exists in the same direction continuously for a predetermined number of times. If so, the process proceeds to step S718. If not, the process proceeds to step S721. . In step S718, it is determined that the direction can be determined.

  In step S719, the camera / AF microcomputer 114 determines whether the focus lens 105 has reciprocated in the same area a predetermined number of times. If so, the process proceeds to step S720, and if not, the process proceeds to step S721. In step S720, it is determined that the focus has been determined.

  In subsequent step S721, the camera / AF microcomputer 114 returns the value to 0 if the counter indicating the operation state of minute driving is 3, and adds the counter if the value is any other value.

  Next, the operation of the focus lens 105 in the above-described minute driving mode will be described with reference to FIG.

  FIG. 6 is a diagram illustrating the operation of the focus lens 105 in the minute driving mode. In the drawing, the horizontal axis represents time and the vertical axis represents the position of the focus lens 105 in accordance with the vertical synchronization signal of the video signal.

  The focus signal EVA for the electric charge accumulated in the image sensor 106 at the time of label A is taken into the camera / AF microcomputer 114 at time TA. The focus signal EVB 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 TB. At time TC, the focus signals EVA and EVB are compared, and the vibration center is moved only when EVB 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.

<Processing Characteristic of this Embodiment>
FIG. 7 is a schematic diagram showing an example of positions of a fixed AF frame and an AF frame (face frame) at the time of face detection. FIG. 8 shows focus signal states of the face frame and the fixed frame in the example of FIG. It is the shown graph.

  The above description using FIG. 4 and FIG. 5, which is the details of the minute driving operation (step S602 in FIG. 3), is the minute driving operation when an ideal evaluation value is obtained. However, when the face frame 701 obtained by face detection is an AF frame as shown in FIG. 7, the focus signal of the face frame is compared with the focus signal of the fixed AF frame 702 as shown in FIG. Has a gentle peak.

  The reason is that since the face is generally a low-contrast subject, the focus signal rarely has a steep peak. Therefore, when focus detection is performed by the above-described micro drive using such a focus signal, a sufficient amount of change in the focus signal cannot be obtained, and the focus position may not be specified.

  Therefore, this problem can be solved by changing the driving amount of the focus lens 105 during a certain time at the time of face detection, which is a feature of the present embodiment. In the following, processing that characterizes the present embodiment will be described with reference to FIG.

  FIG. 9 is a graph showing changes in the focus signal in the face frame in the example of FIG.

  First, the case where the focus lens 105 is located at the portion A in FIG. 8 will be described. When the focus lens 105 is finely driven in the infinite / closest direction, the fluctuation amount of the focus signal becomes small as shown by the signal fluctuation amount d in FIG. This is because the focus signal cannot be changed much because the contrast of the face frame 701 is low. In this case, since the change in the focus signal is small, there is a possibility that the current position of the focus lens 105 is erroneously recognized as the in-focus position.

  Therefore, it can be seen that in the case of an object with low contrast such as a face, the focus lens 105 must be moved per unit time in the infinite / closest direction with an amplitude larger than the reference value. This is illustrated by the signal fluctuation amount d 'in FIG.

  When the amplitude of the focus signal at the time of non-face detection (W in FIG. 9) is used as a reference, the focus lens 105 is moved per unit time with a larger amplitude (W ′ in FIG. 9) at the time of face detection. Even minute changes in the signal can be read. By using the fluctuation amount of the focus signal read at this time, the direction in which the focus lens 105 is to be moved is known, and it is possible to focus even on a low-contrast subject such as a face.

  However, the time for increasing the amplitude for focus signal detection may be a fixed time for performing the process of determining the direction in which the focus lens 105 should move. Since it is necessary to acquire at least three samples of the focus signal value in the infinite / closest direction during the time, it is desirable that the face detection time counter described in step S508 and step S509 in FIG. The specific constant N is determined by repeating sufficient measurement. The face detection time counter is an example of a recording unit, and the number of counters corresponds to the elapsed time since the detection of a specific subject image, that is, the face detection.

In addition, the method for determining the coefficient K that represents the amount of increase in amplitude used in the processing in steps S704B and S711B in FIG.
Amplitude when detecting face = Amplitude when detecting non-face * K <depth of focus
It is desirable to satisfy.

  The drive amount of the focus lens 105 (an example of a focus adjustment member), which is a feature of the present embodiment, has been described by taking an increase amount at the time of face detection as an example when the reference is set as a non-face detection. However, the reference amplitude amount (that is, the reference amount) may be based on the optimum amplitude amount at the time of face detection. The optimum amount of amplitude at the time of face detection is the amount of amplitude when the focus lens 105 is in the in-focus position with respect to the face area obtained from the face detection processing circuit 113 and is in focus. Further, the reference amplitude amount may be the amplitude amount immediately before face detection. That is, the driving amount of the focus lens 105 immediately before the face detection processing circuit 113 detects the face area may be used.

<Details of hill-climbing drive mode>
Next, details of processing in the hill-climbing drive mode in the present embodiment will be described.

  FIG. 10 is a flowchart showing detailed processing in the hill-climbing drive mode in step S609 of FIG.

  First, in step S801, the camera / AF microcomputer 114 sets the drive speed of the focus lens 105. In the next step S801A, it is determined whether or not the face detection flag is set. If it is set, the process proceeds to step S801B.

  In step S801B, since the camera / AF microcomputer 114 is within a predetermined time from the start of face detection, the camera / AF microcomputer 114 multiplies the set driving speed by a constant K ′. Thereby, the arrival time to the in-focus position is shortened, and AF responsiveness is improved. That is, the speed of the hill-climbing driving operation can be increased. The value of the constant K ′ is set to a constant K ′ that is measured a sufficient number of times and does not generate blur and does not generate lens noise.

  In subsequent step S802, the camera / AF microcomputer 114 determines whether or not the current focus signal level has increased from the previous time. If so, the process proceeds to step S803, and if not, the process proceeds to step S804. In step S803, the focus lens 105 is driven to climb in the same direction as the previous time based on the speed set in step S801.

  In step S804, it is determined whether or not the focus signal level has decreased beyond the peak. If so, the process proceeds to step S805, and if not, the process proceeds to step S806. In step S805, the camera / AF microcomputer 114 determines that the peak position has been found.

  In step S806, based on the speed set in step S801, the focus lens 105 is hill-climbed in the direction opposite to the previous time. If step S806 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.

  Next, the operation of the focus lens 105 in the above-described hill-climbing drive mode will be described with reference to FIG.

  FIG. 11 is a graph showing the operation of the focus lens 105 in the hill-climbing drive mode in the present embodiment.

  In the figure, when the focus lens 105 is driven as indicated by A in the figure, the focus signal is increased, and therefore, the mountain 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, when 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. At this time, if face detection is performed, it is possible to easily shift to the hill-climbing driving operation, and if face detection cannot be performed, it may be difficult to shift to the hill-climbing driving operation compared to when face detection is performed.

<Advantages according to the present embodiment>
According to the present embodiment, the drive of the focus lens 105 is increased from the reference amount for a certain time during face detection. That is, when a specific subject such as a face is detected, the drive of the focus lens 105 is increased from the reference amount so that a minute change in the focus signal is read. As a result, even for a low-contrast subject such as a face, the direction of the focus lens 105 can be determined, and the time until focusing can be shortened.

  As a result, the responsiveness of the focus adjustment operation at the time of face detection is improved, and it becomes possible to realize a stable focus adjustment operation for the person who is the main subject intended by the photographer, especially during movie shooting. .

[Second Embodiment]
Next, a second embodiment of the present invention will be described.

  The imaging device according to the second embodiment is the same as that described in FIG. 1 of the first embodiment described above. In the following, parts different from the present embodiment will be mainly described.

  In FIG. 1, a focus signal processing circuit 112 extracts a high-frequency component, a luminance difference component generated from the high-frequency signal, and the like from a signal that has passed through the AF gate 111, and generates a first focus signal. The face detection processing circuit 113 transmits the result of detecting the person's face area in the shooting screen to the camera / AF microcomputer 114. Based on the detection result, the camera / AF microcomputer 114 transmits information to the AF gate 111 so as to add an area used for focus detection to a position including the face area in the shooting screen. The focus signal processing circuit 112 extracts a high-frequency component, a luminance difference component generated from the high-frequency signal, and the like from the signal that has passed through the AF gate 111 based on the information transmitted from the camera / AF microcomputer 114 to obtain the second focus. Generate a signal.

  In this embodiment, the first focus signal and the second focus signal are weighted and combined. The synthesized signal is set as a third focus signal. This is because the second focus signal determined from the face detection processing circuit 113 may change sequentially, and the focus signal may change suddenly. However, when a face cannot be detected by the face detection processing circuit 113, the second focus signal is not synthesized, and focus adjustment control is performed using the first focus signal.

  Based on the above, by weighting the second focus signal and synthesizing it with the first focus signal, it is possible to absorb changes in the second focus signal and perform stable focus signal processing.

  The focus adjustment control described with reference to FIGS. 2 to 11 is the same as that in the first embodiment, and thus the description thereof is omitted.

[Other embodiments]
The object of the present invention can also be achieved by executing the following processing. That is, a storage medium that records a program code of software that realizes the functions of the above-described embodiments is supplied to a system or apparatus, and a computer (or CPU, MPU, etc.) of the system or apparatus is stored in the storage medium. This is the process of reading the code.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the program code and the storage medium storing the program code constitute the present invention.

  Moreover, the following can be used as a storage medium for supplying the program code. For example, floppy (registered trademark) disk, hard disk, magneto-optical disk, CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD + RW, magnetic tape, nonvolatile memory card, ROM or the like. Alternatively, the program code may be downloaded via a network.

Further, the present invention includes a case where the function of the above-described embodiment is realized by executing the program code read by the computer. In addition, an OS (operating system) running on the computer performs part or all of the actual processing based on an instruction of the program code, and the functions of the above-described embodiments are realized by the processing. Is also included.

  Furthermore, a case where the functions of the above-described embodiment are realized by the following processing is also included in the present invention. That is, the program code read from the storage medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. Thereafter, based on the instruction of the program code, the CPU or the like provided in the function expansion board or function expansion unit performs part or all of the actual processing.

DESCRIPTION OF SYMBOLS 101 1st fixed lens 102 Variable magnification lens 103 Diaphragm 104 2nd fixed lens 105 Focus lens 106 Image pick-up element 108 Camera signal processing circuit 109 Display apparatus 112 Focus signal processing circuit 113 Face detection processing circuit 114 Camera AF microcomputer

Claims (10)

Imaging means for photographing a subject and outputting a video signal, subject image detection means for detecting a specific subject image in a photographing screen based on the video signal obtained from the imaging means, and sharpness of the photographing screen from the video signal An imaging apparatus having a focus signal detection unit that detects a focus signal indicating a degree, and an automatic focus adjustment unit that moves a focus adjustment member in accordance with the focus signal and performs focus adjustment,
The automatic focus adjustment means reciprocally moves the focus adjustment member to the close side and the infinity side with a predetermined vibration amplitude, and performs direction determination to determine the direction in which the in-focus point exists in the close side or the infinity side. Mode, a focus position determination mode in which the focus adjusting member is driven in the direction determined in the direction determined from the direction determination mode and the focus position is determined by the subject image detection means in the direction determination mode. An imaging apparatus comprising: an amplitude increasing mode for increasing the predetermined vibration amplitude of the focus adjustment member when the specific subject image is detected compared to when the specific subject image is not detected. apparatus.   In the direction determination mode, the automatic focus adjustment unit is set to the amplitude increase mode for a certain period of time after the detection when the specific subject image is detected by the subject image detection unit during moving image shooting, The imaging apparatus according to claim 1, wherein when the time is exceeded, the amplitude increase mode is canceled.   The imaging apparatus according to claim 1, wherein the predetermined vibration amplitude is set within a focal depth.   The imaging apparatus according to any one of claims 1 to 3, wherein the predetermined vibration amplitude is a movement amount of the focus adjustment member per unit time. A subject frame for detecting the specific subject image, and a fixed frame wider than the subject frame,
In the direction determination mode, the automatic focus adjustment unit is configured to detect a first focus signal generated from a video signal in the fixed frame and an in-subject frame when the subject image detection unit detects the specific subject image. 5. The focus adjustment is performed by using a third focus signal obtained by synthesizing the second focus signal generated from the video signal as a focus signal. The imaging device according to one item.   The imaging apparatus according to claim 1, wherein the specific subject image is a subject having a contrast lower than a predetermined value.   The imaging apparatus according to claim 6, wherein the specific subject image is a face. An imaging step of shooting a subject and outputting a video signal, a subject image detection step of detecting a specific subject image in a shooting screen based on the video signal obtained in the imaging step, and a sharpness of the shooting screen from the video signal A focus signal detection process for detecting a focus signal indicating a degree, and an automatic focus adjustment process for adjusting the focus by moving a focus adjustment member according to the focus signal,
The automatic focusing step includes
A direction determining step of reciprocating the focus adjusting member to a close side and an infinite side with a predetermined vibration amplitude to determine a direction in which the focal point exists in the close side or the infinite side;
A focus position determination step for determining a focus position by moving from the direction determination step and driving the focus adjusting member in the direction determined in the direction;
In the direction determination step, when the specific subject image is detected in the subject image detection step, an amplitude that increases the predetermined vibration amplitude of the focus adjustment member compared to a case where the specific subject image is not detected. And a method of controlling the imaging apparatus.   The program for making a computer perform each process of the control method of Claim 8.   A computer-readable storage medium storing the program according to claim 9.

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