JP2010139666A - Imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce malfunctions of focusing due to parallax, while performing focusing at a high speed, in an imaging device. <P>SOLUTION: The image pickup device includes a first photoelectric conversion sensor for photoelectrically converting a first subject image formed by a photographic optical system to generate an image signal of the first subject image; a second photoelectric conversion sensor for photoelectrically converting a second subject image to generate a distance signal, representing the distance to the second subject image; a first focusing means for focusing the photographic optical system based on the image signal; a second focusing means for focusing the photographic optical system based on the distance signal; a subject image detection means for detecting a subject image area from the image signal; a determination means for determining whether the first subject image differs from the second subject image based on the size of the subject image area and the distance to the subject image; and a control means for performing a control that prevents performing focusing by the second focusing means, when the determination means determines that the first subject image differs from the second subject image. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an imaging apparatus.

  In an autofocus (AF) control method in an imaging apparatus, an AF evaluation value signal indicating the sharpness (contrast state) of an image signal generated using an imaging element is generated, and the AF evaluation value signal is maximized. There is a TV-AF system that searches for the position of the focus lens.

  Japanese Patent Application Laid-Open No. 2004-228688 detects a face area in a shooting screen in an electronic camera, calculates a focus evaluation value from an image signal in a focus detection area including the detected face area, and takes a photographic optical that maximizes the focus evaluation value. It describes that the position of the system is detected as the in-focus position.

  In Patent Document 2, in an imaging apparatus, a face is detected from an image of an object scene, eyes are detected using the detected face information, distance measurement is performed on the detected eye position, and distance information is obtained. And performing an autofocus operation for focusing on the eyes using the distance information.

  Also, in the AF control method, a distance measuring sensor is provided independently of the photographing lens, the focus lens focus position is calculated from the distance to the subject detected by the distance measuring sensor, and the focus lens is moved there. There is an external ranging method (external measurement phase difference detection method). In this external measurement phase difference detection method, a light beam received from an object is divided into two, and the two divided light beams are received by a set of light receiving element arrays (line sensors). Then, a shift amount of the image formed on the set of line sensors, that is, a phase difference is detected, a subject distance is obtained from the phase difference using a triangulation method, and a position where the subject distance is focused Move the focus lens to.

  Further, the AF control method includes a hybrid AF method that combines the TV-AF method and the external measurement phase difference detection method.

  Patent Document 3 describes a hybrid AF type imaging apparatus. In Patent Document 3, an AF signal processing circuit outputs an AF evaluation value signal representing a contrast state of a subject image from a high-frequency component of a signal obtained using an image sensor. The external distance measuring unit measures the distance to the subject and outputs a distance measurement signal corresponding to the measured distance. The microcomputer receives the AF evaluation value signal output from the AF signal processing circuit and the distance measurement signal output from the external distance measurement unit. Then, the microcomputer identifies the shooting situation (scene) according to the change amount of the subject distance, the change amount of the AF evaluation value, and the level of the AF evaluation value, and optimizes the state transition of the AF method and AF processing.

  Specifically, when the change amount of the subject distance is large and the change amount of the AF evaluation value is large, the microcomputer specifies that the subject distance has changed due to panning or tilting (scene 1). In this case, the microcomputer performs the external distance measurement method with respect to the AF method, and then performs the TV-AF method. The microcomputer sets the AF processing mode to the restart operation mode.

  Alternatively, when the change amount of the subject distance is small and the change amount of the AF evaluation value is large, the microcomputer specifies that the picture or the like of the equidistant subject has changed (scene 2). In this case, regarding the AF method, the microcomputer performs the external distance measurement method while the AF evaluation value varies, and performs the TV-AF method when the AF evaluation value is stabilized. The microcomputer sets the AF processing mode to a focus confirmation operation mode.

  Alternatively, when the change amount of the subject distance is large, the change amount of the AF evaluation value is small, and the AF evaluation value level is high, the microcomputer has a parallax between the shooting range of the shooting lens and the distance measurement range of the external distance measurement unit. (Parallax) is identified (scene 3). In this case, the microcomputer performs the TV-AF method with respect to the AF method. The microcomputer sets the AF processing mode to the restart operation mode.

  Alternatively, when the change amount of the subject distance is large and the change amount of the AF evaluation value is small and the level of the AF evaluation value is low, the microcomputer has a low contrast subject and the subject distance has changed due to panning or the like (scene 4 ). In this case, the microcomputer performs the external distance measurement method with respect to the AF method, and then performs the TV-AF method when the level of the AF evaluation value becomes high. The microcomputer sets the AF processing mode to the restart operation mode.

Alternatively, when the change amount of the subject distance is small and the change amount of the AF evaluation value is small, the microcomputer specifies that there is no change in the subject distance and no change in the subject image (scene 5). In this case, the microcomputer locks the AF method and does not select the AF method until the next scene change. The microcomputer sets the AF processing mode to a mode for maintaining the current focus position.
JP 2006-227080 A JP 2001-215403 A JP-A-2005-234325 (paragraphs 0037 to 0062, FIG. 3, etc.)

  In the technique described in Patent Document 3, parallax is not considered for scenes other than scene 3.

  However, when the external phase difference detection method is used, an optical system different from the main optical system of the photographic lens is used, so that parallax may occur even in scenes other than scene 3. When parallax occurs, the area on the screen where the face is detected differs from the area measured by the external phase difference detection method. In this case, the area to be measured by the external phase difference detection method becomes a background subject, and there is a possibility of focusing on the background subject by mistake.

  On the other hand, the external phase difference detection type AF control (focus adjustment) can perform a control operation at a higher speed than the TV-AF type AF control (focus adjustment).

  An object of the present invention is to reduce a malfunction of focus adjustment due to parallax while performing focus adjustment at high speed in an imaging apparatus.

  An imaging apparatus according to one aspect of the present invention includes a first photoelectric conversion sensor that photoelectrically converts a first subject image formed by a photographing optical system to generate an image signal of a first subject, and a second photoelectric conversion sensor. A second photoelectric conversion sensor that photoelectrically converts a subject image to generate a distance signal indicating a distance to a second subject, and a first focus adjustment that performs focus adjustment of the photographing optical system based on the image signal Means, second focus adjusting means for adjusting the focus of the photographing optical system based on the distance signal, subject detecting means for detecting a subject area from the image signal, the size of the subject area and the subject And determining means for determining whether the first subject and the second subject are different from each other based on the distance between the first subject and the second subject. If determined Characterized by comprising a controller that controls so as not to perform focusing by the focus adjusting means.

  According to the present invention, it is possible to reduce malfunction of focus adjustment due to parallax while performing focus adjustment at high speed in the imaging apparatus.

  An imaging apparatus 100 according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a diagram illustrating a configuration of an imaging apparatus 100 according to the first embodiment of the present invention.

  The imaging device 100 is, for example, a digital camera or a video camcorder. The imaging device 100 includes the following components.

  The imaging optical system 120 forms a first subject image on the imaging surface of the first photoelectric conversion sensor 106. The photographing optical system 120 includes a first fixed lens 101, a variable magnification lens 102, a diaphragm 103, and a second fixed lens 104. The photographing optical system 120 includes a focus compensator lens (hereinafter referred to as a focus lens) 105.

  The first fixed lens 101 guides incident light to the variable power lens 102.

  The variable magnification lens 102 moves in the optical axis direction to perform variable magnification. The variable power lens 102 guides the light received from the first fixed lens 101 to the second fixed lens 104 through the diaphragm 103.

  The diaphragm 103 adjusts the amount of light guided from the first fixed lens 101 to the second fixed lens 104.

  The second fixed lens 104 guides the light received from the variable magnification lens 102 to the focus lens 105.

  The focus lens (optical element for focus adjustment) 105 has a function of correcting the movement of the focal plane accompanying zooming and a function of focusing.

  The first photoelectric conversion sensor 106 generates an image signal for obtaining an image of the first subject by photoelectrically converting the first subject image formed by the photographing optical system 120. The first photoelectric conversion sensor 106 is, for example, a CCD sensor or a CMOS sensor. The first subject is, for example, a person's face.

  The CDS / AGC circuit 107 receives the image signal output from the first photoelectric conversion sensor 106. The CDS / AGC circuit 107 obtains an image signal from which fixed pattern noise has been removed by performing CDS processing on the received image signal. The CDS / AGC circuit 107 generates and outputs an amplified image signal by performing amplification processing on the obtained image signal with an adjusted gain.

  The camera signal processing circuit 108 receives the image signal output from the CDS / AGC circuit 107. The camera signal processing circuit 108 performs various types of image processing on the received image signal and outputs the processed image signal.

  For example, the camera signal processing circuit 108 generates an image signal for display according to the received image signal and outputs it to the monitor device 109.

  Alternatively, for example, the camera signal processing circuit 108 generates a recording image signal (compressed image data) in accordance with the received image signal and outputs it to the recording device 115.

  The monitor device 109 receives an image signal for display from the camera signal processing circuit 108. The monitor device 109 displays an image corresponding to the received display image signal. The monitor device 109 is constituted by, for example, an LCD.

  The recording device 115 receives the recording image signal output from the camera signal processing circuit 108. The recording device 115 records the received image signal for recording on a predetermined recording medium. The predetermined recording medium may be, for example, a recording medium that is detachably attached to the recording device 115 such as a magnetic tape, an optical disk, or a semiconductor memory, or may be a recording medium provided in the imaging device 100 such as a hard disk drive. good.

  The zoom drive source 110 moves (drives) the zoom lens 102. The focusing drive source 111 moves (drives) 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, respectively.

  The subject detection unit 116 receives the image signal output from the CDS / AGC circuit 107. The subject detection unit 116 performs subject detection processing on the received image signal to detect a subject region including the first subject. The subject detection unit 116 also detects the size of the subject region. The subject detection unit 116 outputs these detection results to the camera / AF microcomputer 114. Thus, the camera / AF microcomputer 114 determines a focus detection area corresponding to the subject area based on the detection result, and outputs information for designating the focus detection area to the AF gate 112. The focus detection area corresponding to the subject area is, for example, an area including the subject area and larger than the subject area.

  Here, the first subject is, for example, a human face. The subject detection process is, for example, a face detection process. The subject area is, for example, a face area. In this case, the subject detection unit 116 detects the face area including the face of the person and the size of the face area from the image signal.

  Note that a known face detection technique is used for the face detection in the present invention. As a known face detection technique, a method using learning typified by a neural network, a part having a characteristic shape such as an eye, nose, or mouth is searched from an image area using template matching, and is regarded as a face if the similarity is high. Techniques are listed. In addition, many other methods have been proposed, such as methods that detect image features such as skin color and eye shape and use statistical analysis. In general, multiple methods are used to recognize faces. Is common.

  Specific examples include a face detection method using wavelet transform and image feature amount described in JP-A-2002-251380.

  The first focus adjustment unit 130 receives the image signal output from the CDS / AGC circuit 107. The first focus adjustment unit 130 adjusts the focus of the photographing optical system 120 using the received image signal. The first focus adjustment unit 130 includes an AF gate 112, an AF signal processing circuit (focus detection means) 113, and a first focusing unit 114a.

  The AF gate 112 receives information for designating an area (focus detection area) used for focus detection from the camera / AF microcomputer 114. The AF gate 112 receives the image signal output from the CDS / AGC circuit 107. The AF gate 112 passes the signal of the designated focus detection area among the received image signals.

  The AF signal processing circuit 113 receives the image signal that has passed through the AF gate 112. The AF signal processing circuit 113 acquires the evaluation value of the focus detection area corresponding to the subject area including the first subject from the received image signal, and determines the focus state of the photographing optical system 120 based on the acquired evaluation value. To detect. The AF signal processing circuit 113 outputs the detected result to the first focusing unit 114a in the camera / AF microcomputer 114.

  Specifically, 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), and the like to generate an AF evaluation value signal. The AF evaluation value signal is output to the camera / AF microcomputer 114. The AF evaluation value signal represents the sharpness (contrast state) of an image generated based on the image signal output from the first photoelectric conversion sensor 106. Since the sharpness changes depending on the in-focus state of the image pickup optical system, a signal representing the in-focus state of the image pickup optical system results.

  The first focusing unit 114 a moves the focus lens 105 to the in-focus position via the focusing drive source 111 according to the focus state detected by the AF signal processing circuit 113.

  The external distance measuring unit (second photoelectric conversion sensor) 117 detects the distance to the second subject by photoelectrically converting the second subject image, and indicates the detected distance to the second subject. Generate a signal. Specifically, the external distance measuring unit 117 performs an external measurement phase difference detection method, an ultrasonic sensor method, an infrared ray, and the like, as in the prior art, on a signal obtained by photoelectrically converting the second subject image. The distance to the second subject is obtained by performing processing such as a sensor method. The external distance measuring unit 117 generates a distance signal indicating the distance to the second subject in accordance with the calculated distance to the second subject, and the generated distance signal is used for the second focus adjustment in the camera / AF microcomputer. Output to the unit 140 and the first switching unit 114e.

  Here, as the distance measurement reliability, for example, in the case of the external measurement phase difference detection method, distance measurement is performed based on the relative positional deviation amount in the beam splitting direction. It is common to do.

  The second focus adjustment unit 140 receives the distance signal output from the external distance measuring unit 117. The second focus adjustment unit 140 adjusts the focus of the photographing optical system 120 using the received distance signal. The second focus adjustment unit 140 includes a second calculation unit 114d and a second focusing unit 114b.

  The second calculation unit 114d receives the distance signal output from the external distance measuring unit 117. The second calculation unit 114d calculates the in-focus position of the focus lens 105 in the photographing optical system 120 according to the distance to the second subject indicated by the received distance signal. The second calculation unit 114d supplies the calculated result to the second focusing unit 114b and a first switching unit 114e described later.

  The second focusing unit 114b receives the calculation result from the second calculation unit 114d. The second focusing unit 114b moves the focus lens 105 to the in-focus position calculated by the second calculation unit via the focusing drive source 111.

  The camera / AF microcomputer 114 generally controls each part of the imaging apparatus 100 and performs various control operations. For example, the camera / AF microcomputer 114 performs AF control for moving the focus lens 105 by controlling the focusing drive source 111 based on the AF evaluation value signal.

  That is, the control unit of the camera / AF microcomputer 114 determines the first focus adjustment unit 130 and the first focus control unit 130 based on the size of the subject area including the first subject and the distance to the second subject indicated by the distance signal. The second focus adjustment unit 140 is selectively controlled as follows. The camera / AF microcomputer 114 performs focus adjustment by the second focus adjustment unit 140 when it is determined that the first subject and the second subject are the same. The camera / AF microcomputer 114 performs focus adjustment by the first focus adjustment unit 130 when it is determined that the first subject and the second subject are different.

  The camera / AF microcomputer 114 includes a first calculation unit 114c and a first switching unit 114e in addition to the first focusing unit 114a, the second calculation unit 114d, and the second focusing unit 114b. including. Here, the 1st calculating part 114c and the 1st switching part 114e comprise said control part.

  The first calculation unit 114 c receives information on the size of the subject area (face area) output from the subject detection unit 116. The first calculation unit 114c focuses on the photographing optical system 120 according to the received information on the size of the subject area, that is, the size of the subject area (face area) including the first subject (person's face). The in-focus position of the lens 105 is calculated.

  Here, the first calculation unit 114c refers to the data table in which the size of the average subject area (face area) and the distance to the subject (person's face) are associated with each other, thereby The distance to the first subject (person's face) according to the size is calculated. This data table may be stored in advance in a memory in the camera / AF microcomputer 114, or may be stored in another memory in the imaging apparatus 100, a hard disk, or the like. The first calculation unit 114c calculates a focus position of the focus lens 105 in the photographing optical system 120 according to the calculated distance to the first subject.

  The first calculation unit 114c outputs the calculated focus position information to the first switching unit 114e.

  Alternatively, the first calculation unit (distance calculation unit) 114c supplies the calculated distance to the first subject to the first switching unit 114e.

  When the difference between the in-focus position calculated by the first calculating unit 114c and the in-focus position calculated by the second calculating unit 114d is less than the first threshold, the first switching unit 114e Switch the focus adjustment operation. The first switching unit 114e switches the focus adjustment operation so that the second focus adjustment unit 140 performs the focus adjustment. That is, when the difference between the in-focus position calculated by the first calculating unit 114c and the in-focus position calculated by the second calculating unit 114d is less than the threshold, the first switching unit 114e It is determined that the subject and the second subject are the same. The first switching unit 114e switches the focus adjustment operation so that the focus adjustment by the second focus adjustment unit 140 is performed according to the determination result.

  Further, when the difference between the in-focus position calculated by the first calculating unit 114c and the in-focus position calculated by the second calculating unit 114d is equal to or more than the first threshold, The focus adjustment operation is switched so that the focus adjustment by the first focus adjustment unit 130 is performed. That is, when the difference between the in-focus position calculated by the first calculating unit 114c and the in-focus position calculated by the second calculating unit 114d is equal to or greater than the threshold, the first switching unit 114e It is determined that the subject and the second subject are different. The first switching unit 114e switches the focus adjustment operation so that the focus adjustment by the first focus adjustment unit 130 is performed according to the determination result.

  Alternatively, the first switching unit 114e switches the focus adjustment operation as follows.

  The first switching unit 114e has a difference between the distance to the first subject calculated by the first calculation unit 114c and the distance to the second subject indicated by the distance signal is less than the second threshold. In this case, the focus adjustment operation is switched as follows. The first switching unit 114e switches the focus adjustment operation so that the second focus adjustment unit 140 performs the focus adjustment. In other words, the first switching unit 114e is configured such that the difference between the distance to the first subject calculated by the first calculation unit 114c and the distance to the second subject indicated by the distance signal is less than the threshold value. , It is determined that the first subject and the second subject are the same. The first switching unit 114e switches the focus adjustment operation so that the focus adjustment by the second focus adjustment unit 140 is performed according to the determination result.

  In the first switching unit 114e, the difference between the distance to the first subject calculated by the first calculation unit 114c and the distance to the second subject indicated by the distance signal is greater than or equal to the second threshold. In this case, the focus adjustment operation is switched so as to perform the focus adjustment by the first focus adjustment unit 130. That is, the first switching unit 114e is configured such that the difference between the distance to the first subject calculated by the first calculation unit 114c and the distance to the second subject indicated by the distance signal is greater than or equal to a threshold value. It is determined that the first subject and the second subject are different. The first switching unit 114e switches the focus adjustment operation so that the focus adjustment by the first focus adjustment unit 130 is performed according to the determination result.

  As described above, the focus adjustment by the second focus adjustment unit is performed when it is determined that the first subject and the second subject are the same, so that the focus adjustment can be performed at high speed. In addition, when it is determined that the first subject is different from the second subject, the focus adjustment by the first focus adjustment unit is performed, so that it is possible to avoid a focus adjustment malfunction due to parallax. In other words, in the imaging apparatus, it is possible to reduce malfunction of focus adjustment due to parallax while performing focus adjustment at high speed.

  Next, AF control (focus adjustment operation) performed by the camera / AF microcomputer 114 will be described with reference to FIG. This AF control is executed according to a computer program stored in the camera / AF microcomputer 114. FIG. 2 is a flowchart showing the focus adjustment operation of the imaging apparatus according to the first embodiment of the present invention.

  In Step 201, the camera / AF microcomputer 114 starts AF control processing.

  In Step 202, the subject detection unit 116 performs face detection processing and outputs information on the position and size of the face area to the camera / AF microcomputer 114.

  In Step 203, if the face detection is successful in the subject detection unit 116, the camera / AF microcomputer 114 advances the process to Step 204, and if not, advances the process to Step 206.

  In Step 204, the camera / AF microcomputer 114 sets the AF frame based on the position and size of the face area.

  In Step 206, the camera / AF microcomputer 114 sets a normal AF frame. This is generally set as a fixed AF frame that does not move near the center of the screen.

  In Step 205, the camera / AF microcomputer 114 performs focusing by the hybrid AF method that combines the TV-AF method using the AF evaluation value and the external measurement phase difference AF method.

  Next, hybrid AF control (Step 205) will be described with reference to FIG. FIG. 3 is a flowchart showing hybrid AF control of the imaging apparatus according to the first embodiment of the present invention.

  In Step 801, the camera / AF microcomputer 114 starts the hybrid AF control process.

  In Step 802, the camera / AF microcomputer 114 executes TV-AF control processing. This TV-AF control includes an operation of driving the focus lens 105 to obtain focus while monitoring the AF evaluation value. Further, in the TV-AF control, in a state where the focus is obtained, in order to determine whether or not the focus lens needs to be redriven, it is determined whether or not the AF evaluation value has been reduced. The process for maintaining is also included.

  In Step 803, the camera / AF microcomputer 114 detects the subject distance by the external distance measuring unit 117, and further calculates the outer measurement focus position from the subject distance information.

  In Step 804, the camera / AF microcomputer 114 determines whether or not the current operation mode is the external measurement phase difference use mode. If the camera / AF microcomputer 114 is in the external measurement phase difference use mode, the process proceeds to Step 808. If the camera / AF microcomputer 114 is not in the external measurement phase difference use mode, the process proceeds to Step 805. The external measurement phase difference use mode is a mode in which external measurement AF for moving the focus lens 105 to the external measurement focus position is permitted only when a specific condition is satisfied in Step 810 described later.

  In Step 805, the camera / AF microcomputer 114 sets threshold values (first and second values) for determining whether or not changes in contrast and subject distance are large in Step 806 described later.

  In Step 806, the camera / AF microcomputer 114 determines a change related to the subject using the contrast information and the subject distance information in order to determine whether or not to switch to the external measurement phase difference use mode. That is, the camera / AF microcomputer 114 determines whether or not the change amount of the contrast information acquired in the current routine with respect to the contrast information acquired in the previous routine is larger than the threshold value. Further, the camera / AF microcomputer 114 determines whether or not the amount of change in the subject distance information acquired in the current routine with respect to the subject distance information acquired in the previous routine is larger than a threshold value.

  In the present embodiment, the camera / AF microcomputer 114 obtains a difference between the maximum value and the minimum value of the luminance level in each pixel line of the signal obtained from the AF signal processing circuit 113 and passed through the AF gate 112. Then, the maximum value of these differences is used as contrast information. Instead of the contrast information, an AF evaluation value that is common in terms of indicating the contrast state may be compared with a threshold value.

  In Step 806, when the camera / AF microcomputer 114 determines that the contrast change amount is larger than the threshold value and the subject distance change amount is also larger than the threshold value, the process proceeds to Step 807.

  On the other hand, when the camera / AF microcomputer 114 determines that at least one of the change amount of the contrast and the change amount of the subject distance is smaller than the threshold value, the camera / AF microcomputer 114 does not switch to the external measurement phase difference use mode and performs the processing in Step 802. The TV-AF control is performed by returning to step S2. That is, when at least one of the contrast change amount and the subject distance change amount is smaller than the threshold value, the camera / AF microcomputer 114 repeatedly performs only the TV-AF control at the imaging signal readout cycle described later.

  In the present embodiment, a case is described in which it is determined whether or not the amount of change in the subject distance information is greater than the threshold value. However, in step 803, the out-of-focus position calculated based on the subject distance information. The amount of change may be determined. In this case, it is equivalent to determining the amount of change in the subject distance information.

  The determination in Step 806 is a first-stage determination for moving the focus lens 105 using the subject distance information (or information on the external measurement focus position), that is, switching whether or not to perform external measurement AF. That is, the condition (timing) for driving the focus lens 105 by external measurement AF is limited to the case where the contrast state of the subject has changed greatly and the subject distance has changed greatly.

  As a result, when the AF evaluation value changes greatly due to changes in the subject's pattern, etc., even though the subject distance has not changed significantly and is not out of focus, the focus lens is first moved to the out-of-focus position. This prevents unwanted blurring of the image.

  In Step 808, the camera / AF microcomputer 114 switches the operation mode to the external measurement phase difference use mode, and advances the processing to Step 808.

  In Step 808, the camera / AF microcomputer 114 determines whether or not the external measurement phase difference driving mode is set. However, if the camera / AF microcomputer 114 is already set to the external measurement phase difference drive mode and the focus lens 105 is moving toward the external measurement in-focus position, the process returns to Step 802.

  On the other hand, if the camera / AF microcomputer 114 is not in the external measurement phase difference drive mode, the process proceeds to Step 809.

  In Step 809, the camera / AF microcomputer 114 sets a threshold value (third value) used in the subsequent determination in Step 810. Specifically, the camera / AF microcomputer 114 sets a focus position difference threshold th for determining whether or not the focus lens 105 should be moved to the external measurement focus position (external measurement AF is executed). The focus position difference threshold th is determined in consideration of variations in subject distance detection by the external distance measuring unit 117.

  In Step 810, the camera / AF microcomputer 114 obtains a difference (absolute value) between the external measurement focus position obtained in Step 803 and the current focus lens position, and the difference is a focus position difference threshold value set in Step 809. It is determined whether it is larger than th. If this difference is larger than the focus position difference threshold th, the camera / AF microcomputer 114 advances the process to Step 811. If the difference is smaller than the focus position difference threshold th, the camera / AF microcomputer 114 advances the process to Step 813.

  The determination in Step 810 is a second stage determination for switching whether or not to perform external measurement AF. That is, the condition (timing) for driving the focus lens 105 by external measurement AF is limited to a case where the difference between the external measurement focus position and the current focus lens position is large.

  The reason why the external measurement AF is not performed when the second stage condition is not satisfied is that the external measurement AF is inferior in focusing accuracy as compared with the TV-AF. This is because if the focus lens 105 is carelessly moved to the external measurement focus position, hunting occurs between the TV-AF and the external measurement AF or the image is blurred.

  In Step 811, the camera / AF microcomputer 114 determines whether the subject distance and the focus distance predicted from the size of the face frame are within a predetermined range. This is realized by having a data table indicating the shooting distance with respect to the detected face size at each zoom lens position. This data table is created in advance by examining how a general face size is detected by the shooting distance at each zoom lens position.

  In Step 811, if the camera / AF microcomputer 114 determines that the subject distance and the focus distance predicted from the size of the face frame are within a predetermined range, the process proceeds to Step 812.

  In Step 812, the camera / AF microcomputer 114 shifts the operation mode to the external measurement phase difference drive mode.

  In Step 813, the camera / AF microcomputer 114 moves the focus lens 105 toward the external measurement focus position.

  In Step 814, the camera / AF microcomputer 114 cancels the external measurement phase difference use mode.

  The above-described hybrid AF method is an example, and the switching method between the TV-AF method and the external measurement phase difference AF method is not limited to this.

  Next, TV-AF control (Step 802) will be described with reference to FIG. FIG. 4 is a flowchart showing TV-AF control of the imaging apparatus according to the first embodiment of the present invention.

  In Step 301, the camera / AF microcomputer 114 starts TV-AF control processing.

  In Step 302, the AF signal processing circuit 113 acquires an AF evaluation value from the image signal and outputs it to the camera / AF microcomputer 114.

  In Step 303, the camera / AF microcomputer 114 determines whether the operation mode is the minute drive mode or not the minute drive mode (the TV-AF mode). If the camera / AF microcomputer 114 is in the minute drive mode, the process proceeds to step 304; otherwise, the process proceeds to step 311.

  In Step 304, the camera / AF microcomputer 114 performs a minute driving operation to determine whether the in-focus state or not, and in which direction the in-focus position is relative to the current focus lens position (hereinafter, in-focus direction). It is determined whether there is. The detailed operation here will be described later with reference to FIG.

  Note that the control for causing the focus lens 105 to perform a minute driving operation in order to determine whether or not it is in focus from the change in the AF evaluation value can also be referred to as focus confirmation control. Further, the control for causing the focus lens 105 to perform a minute driving operation in order to determine the in-focus direction from the change in the AF evaluation value can also be referred to as in-focus direction determination control.

  In Step 305, the camera / AF microcomputer 114 determines whether or not the focus determination can be performed in Step 304. If the focus determination can be performed, the process proceeds to Step 308.

  At Step 308, the camera / AF microcomputer 114 stops driving the focus lens 105.

  In Step 309, the camera / AF microcomputer 114 stores the AF evaluation value at the in-focus position in a memory (not shown).

  In Step 310, the camera / AF microcomputer 114 shifts the operation mode to the restart mode.

  In Step 325, the camera / AF microcomputer 114 cancels the external measurement phase difference use mode. This is determined as in-focus by the TV-AF, and the focus lens 105 is stopped. Therefore, the focus lens 105 is moved to the external measurement focus position by the external measurement AF so that unnecessary blurring of the image does not occur. Because.

  If the camera / AF microcomputer 114 determines in step 305 that the in-focus determination has not been made, the process proceeds to step 306.

  In Step 306, the camera / AF microcomputer 114 determines whether or not the in-focus direction can be determined in Step 304. If the in-focus direction can be determined, the process proceeds to Step 307 to shift to the hill-climbing drive mode. If the in-focus direction cannot be determined, the camera / AF microcomputer 114 returns the process to Step 304 and continues the minute driving operation.

  In Step 311, the camera / AF microcomputer 114 determines whether or not the hill climbing drive mode is set. If the camera / AF microcomputer 114 is in the hill-climbing drive mode, the process proceeds to step 312; otherwise, the process proceeds to step 317.

  In Step 312, the camera / AF microcomputer 114 hill-climbs the focus lens 105 at a predetermined speed (focus position detection control). Details of the hill-climbing drive will be described later with reference to FIGS.

  In Step 313, the camera / AF microcomputer 114 determines whether or not the AF evaluation value exceeds the peak in the hill-climbing drive. If the peak is exceeded, the camera / AF microcomputer 114 advances the process to step 314. If the peak is not exceeded, the process is returned to step 312 to continue the hill-climbing drive.

  In Step 314, the camera / AF microcomputer 114 returns the focus lens 105 to a position where the AF evaluation value during hill-climbing driving reaches a peak (hereinafter referred to as a peak position).

  Next, in Step 315, the camera / AF microcomputer 114 determines whether or not the focus lens 105 has returned to the peak position. When the camera / AF microcomputer 114 returns to the peak position, the process proceeds to Step 316. If the camera / AF microcomputer 114 has not yet returned, the process returns to Step 315 to continuously return the focus lens 105 to the peak position.

  In Step 316, the camera / AF microcomputer 114 shifts the operation mode to the minute drive mode.

  In Step 324, the camera / AF microcomputer 114 cancels the external measurement phase difference use mode. This is because the focus lens 105 is driven to the external measurement focus position by the external measurement AF even though the focus position (peak position) is determined in the hill-climbing drive mode and the focus lens 105 is moved to the focus position. This is to prevent unnecessary blurring of the image.

  In Step 317, the camera / AF microcomputer 114 determines whether or not the operation mode is the restart determination mode. If the operation mode is the restart determination mode, the camera / AF microcomputer 114 advances the process to Step 318, and if not, advances the process to Step 321.

  In Step 318, the camera / AF microcomputer 114 compares the AF evaluation value stored in Step 309 with the latest AF evaluation value, and determines whether or not the difference between them, that is, the fluctuation of the AF evaluation value is larger than a predetermined value. If the AF evaluation value fluctuates more than a predetermined value, the camera / AF microcomputer 114 advances the process to Step 320. If the variation of the AF evaluation value is smaller than the predetermined value, the camera / AF microcomputer 114 advances the process to Step 319.

  In Step 319, the camera / AF microcomputer 114 stops the focus lens 105 as it is.

  In Step 320, the camera / AF microcomputer 114 shifts the operation mode to the minute drive mode.

  In Step 321, the camera / AF microcomputer 114 moves the focus lens 105 toward the external measurement focus position in the external measurement phase difference drive mode. The camera / AF microcomputer 114 determines whether or not the focus lens 105 has reached the target position with the external measurement focus position as the target position. The camera / AF microcomputer 114 advances the process to Step 322 when the focus lens 105 reaches the external measurement focus position.

  In Step 322, the camera / AF microcomputer 114 shifts the operation mode to the minute drive mode.

  In Step 323, the camera / AF microcomputer 114 cancels the external measurement phase difference use mode and takes over from the external measurement AF to TV-AF (micro drive mode: focus confirmation control or focus direction determination control in Step 304). When the focus lens 105 has not reached the external measurement focus position, the camera / AF microcomputer 114 continues to drive the focus lens to the external measurement focus position.

  Next, the minute driving operation (Step 304) will be described with reference to FIG. FIG. 5 is a flowchart showing a minute driving operation of the imaging apparatus according to the first embodiment of the present invention.

  In Step 401, the camera / AF microcomputer 114 starts processing of the minute driving operation.

  In Step 402, the camera / AF microcomputer 114 determines whether or not the AF evaluation value is larger than the previous AF evaluation value. If the AF evaluation value is larger than the previous AF evaluation value, the camera / AF microcomputer 114 advances the process to Step 403. If the AF evaluation value is smaller than the previous AF evaluation value, the camera / AF microcomputer 114 advances the process to Step 404.

  In Step 403, the camera / AF microcomputer 114 drives the focus lens by a predetermined amount in the previous forward direction.

  In Step 404, the camera / AF microcomputer 114 drives the focus lens by a predetermined amount in the reverse direction of the previous time.

  In Step 405, the camera / AF microcomputer 114 determines whether or not the direction determined to be the in-focus direction is the same continuously for a predetermined number of times. The camera / AF microcomputer 114 proceeds the process to Step 406 if the direction determined to be the in-focus direction is the same for a predetermined number of times, and proceeds to Step 407 if the direction has not been continued for the predetermined number of times in the same direction. Proceed.

  In Step 407, the camera / AF microcomputer 114 determines whether or not the focus lens repeats reciprocation within a predetermined range a predetermined number of times. The camera / AF microcomputer 114 advances the process to Step 408 if the focus lens repeats reciprocation within a predetermined range a predetermined number of times, and advances the process to Step 410 if the focus lens is not within the predetermined range for a predetermined time.

  In Step 406, the camera / AF microcomputer 114 determines that the direction has been determined, and proceeds to Step 409 to end the processing and shift to hill-climbing driving.

  In Step 408, the camera / AF microcomputer 114 finishes the process and determines that the in-focus determination has been made, and proceeds to the restart determination routine.

  Next, the minute driving operation (Step 304) will be described with reference to FIG. FIG. 6 is a diagram illustrating a minute driving operation of the imaging apparatus according to the first embodiment of the present invention.

  FIG. 6 shows the relationship between the movement of the focus lens 105 and the change in the AF evaluation value during the minute driving operation. Here, the horizontal axis represents time, and the vertical axis represents the focus lens position. In the upper part of the figure, a vertical synchronization signal of the image signal is shown.

Here, during the period A, the AF evaluation value EV _A for the electric charge (indicated by the hatched ellipse) accumulated in the first photoelectric conversion sensor 106 is taken in at time T _A.

During period B, an AF evaluation value EV _B for the electric charge accumulated in the first photoelectric conversion sensor 106 is taken in at time T _B.
At time _{T C,} the camera / AF microcomputer 114, AF evaluation values _EV A, compares the EV _B. If EV _A <EVB, the camera / AF microcomputer 114 moves the focus lens in the forward direction as it is. On the other hand, the camera / AF microcomputer 114 moves the focus lens in the reverse direction if EVA> EVB. Here, the camera / AF microcomputer 114 determines, based on the depth of focus, a lens driving amount such that the movement of the focus is not recognized by looking at the imaging signal on a TV screen or the like by a single movement.

  Next, the hill-climbing driving operation (Step 312) will be described with reference to FIG. FIG. 7 is a flowchart showing a hill-climbing driving operation of the imaging apparatus according to the first embodiment of the present invention.

  In Step 601, the camera / AF microcomputer 114 starts processing for hill-climbing driving operation.

  In Step 602, the camera / AF microcomputer 114 determines whether or not the AF evaluation value is larger than the previous AF evaluation value. If the AF evaluation value is greater than the previous AF evaluation value, the camera / AF microcomputer 114 proceeds to step 603. If the AF evaluation value is smaller than the previous AF evaluation value, the camera / AF microcomputer 114 proceeds to step 604.

  In Step 603, the camera / AF microcomputer 114 drives the focus lens at a predetermined speed in the previous forward direction. Thereafter, the camera / AF microcomputer 114 advances the process to Step 607 and ends the process.

  In Step 604, the camera / AF microcomputer 114 determines whether or not the AF evaluation value decreases beyond the peak. If the AF evaluation value decreases beyond the peak, the camera / AF microcomputer 114 advances the process to Step 605.

  In Step 605, the camera / AF microcomputer 114 determines that the AF evaluation value exceeds the peak, advances the process to Step 607, and ends the process.

  In Step 604, if the camera / AF microcomputer 114 does not decrease the AF evaluation value beyond the peak, the process proceeds to Step 606.

  In Step 606, the camera / AF microcomputer 114 drives the focus lens at a predetermined speed in the direction opposite to the previous time, and advances the process to Step 607.

  Next, the hill-climbing driving operation (Step 312) will be described with reference to FIG. FIG. 8 is a diagram illustrating a hill-climbing driving operation of the imaging apparatus according to the first embodiment of the present invention.

  In the hill-climbing driving operation, the camera / AF microcomputer 114 drives the focus lens 105 at a high speed, and the AF signal processing circuit 113 detects the peak position where the AF evaluation value obtained in the meantime or the vicinity thereof is detected. FIG. 8 shows the relationship between the movement of the focus lens 105 and the change in the AF evaluation value during the hill-climbing driving operation.

  Here, in the movement of C, since the AF evaluation value decreases beyond the peak, the presence of the peak position (focusing position) can be confirmed, and the hill-climbing driving operation is terminated and the operation proceeds to the minute driving operation.

  On the other hand, in the movement of D, since there is no peak and it decreases monotonously, it can be determined that the driving direction of the focus lens 105 is incorrect. In this case, the driving direction is reversed and the hill-climbing driving operation is continued.

  As described above, according to the present embodiment, in the system combining the hybrid AF method and the face detection function, the external distance measurement distance and the focus distance predicted from the size of the face detected. Only when the distance is within the predetermined range, the movement to the external distance measuring position is performed. This enables high-speed, stable and accurate focusing on the main subject intended by the photographer. If the face detection area and the distance measurement area of the external phase detection method differ, It is possible to prevent focusing on a subject different from the human subject.

  Note that the position (pixel position) of the AF evaluation value generation area in the image may be a position designated by the user via an input unit (not shown) instead of the detected face position, or the viewfinder It may be a position automatically determined by detecting the line of sight of the photographer.

  Next, an imaging apparatus 200 according to the second embodiment of the present invention will be described with reference to FIG. FIG. 9 is a diagram illustrating a configuration of an imaging apparatus 200 according to the second embodiment of the present invention. Below, it demonstrates centering on a different part from 1st Embodiment.

  The imaging apparatus 200 includes a camera / AF microcomputer 214. The camera / AF microcomputer 214 includes a third calculation unit 214f, a fourth calculation unit 214g, and a second switching unit 214e, but does not include the first switching unit 114e.

  The third calculation unit 214f calculates the in-focus direction of the focus lens 105 in the photographing optical system 120 according to the change in the size of the subject area including the first subject.

  The fourth calculation unit 214g calculates the in-focus direction of the focus lens 105 in the photographing optical system 120 in accordance with the change in the distance to the second subject indicated by the distance signal.

  When the focusing direction calculated by the third calculation unit 214f and the focusing direction calculated by the fourth calculation unit 214g are the same, the second switching unit 214e adjusts the focus by the second focus adjustment unit 140. To switch the focus adjustment operation. In other words, the second switching unit 214e determines that the first subject and the second subject when the in-focus direction calculated by the third calculating unit 214f and the in-focus direction calculated by the fourth calculating unit 214g are the same. It is determined that the two subjects are the same. The second switching unit 214e switches the focus adjustment operation so that the focus adjustment by the second focus adjustment unit 140 is performed according to the determination result.

  When the in-focus direction calculated by the third calculation unit 214f and the in-focus direction calculated by the fourth calculation unit 214g are different, the second switching unit 214e adjusts the focus by the first focus adjustment unit 130. To switch the focus adjustment operation. That is, when the focusing direction calculated by the third calculation unit 214f and the focusing direction calculated by the fourth calculation unit 214g are different from each other, the second switching unit 214e and the second switching unit 214e Judge that the subject is different. The second switching unit 214e switches the focus adjustment operation so that the focus adjustment by the first focus adjustment unit 130 is performed according to the determination result.

  Further, as shown in FIG. 10, the hybrid AF control (Step 205) is different from the first embodiment in that Step 901 is included instead of Step 811 shown in FIG. FIG. 10 is a flowchart showing hybrid AF control of the imaging apparatus according to the second embodiment of the present invention.

  In Step 901, the camera / AF microcomputer 114 determines whether or not the direction of the external focus position with respect to the current focus lens position and the focus direction predicted from the change in the size of the face frame are the same.

  For example, if the direction of the outer measurement focus position is infinite and the change in the size of the face frame is large → small, the camera / AF microcomputer 114 determines the direction of the outer measurement focus position and the size of the face frame. It is determined that the focus direction predicted from the change is the same, and external measurement AF should be used.

  For example, if the direction of the outer measurement focus position is infinite and the change in the size of the face frame is small → large, the camera / AF microcomputer 114 determines the direction of the outer measurement focus position and the size of the face frame. Different from the in-focus direction predicted from the change, it is determined that the external measurement AF should not be used.

  For example, if the camera / AF microcomputer 114 is close to the direction of the external measurement focus position and the change in the size of the face frame is small to large, the direction of the external measurement focus position and the size of the face frame are It is determined that the focus direction predicted from the change is the same, and external measurement AF should be used.

  For example, if the camera / AF microcomputer 114 is close to the direction of the outer measurement focus position and the change in the size of the face frame is large → small, the direction of the outer measurement focus position and the size of the face frame are Different from the in-focus direction predicted from the change, it is determined that the external measurement AF should not be used.

  If the direction of the in-focus position and the focus direction predicted from the change in the size of the face frame are the same, the camera / AF microcomputer 114 advances the process to Step 812. The camera / AF microcomputer 114 advances the process to Step 814 if the direction of the external measurement focus position and the focus direction predicted from the change in the size of the face frame are different.

  As described above, according to the present embodiment, in the system that combines the hybrid AF method and the face detection function, the focusing direction of the external ranging position from the current lens position, and the detected face of the face Only when the change direction of the size matches, it moves to the external ranging position. This enables high-speed, stable and accurate focusing on the main subject intended by the photographer. If the face detection area differs from the distance measurement area of the external measurement phase difference detection method, It is possible to prevent focusing on a subject different from the human subject.

1 is a diagram illustrating a configuration of an imaging apparatus 100 according to a first embodiment of the present invention. 3 is a flowchart showing a focus adjustment operation of the imaging apparatus according to the first embodiment of the present invention. 3 is a flowchart showing hybrid AF control of the imaging apparatus according to the first embodiment of the present invention. 5 is a flowchart showing TV-AF control of the imaging apparatus according to the first embodiment of the present invention. 3 is a flowchart showing a minute driving operation of the imaging apparatus according to the first embodiment of the present invention. FIG. 3 is a diagram illustrating a minute driving operation of the imaging apparatus according to the first embodiment of the present invention. 3 is a flowchart showing a hill-climbing driving operation of the imaging apparatus according to the first embodiment of the present invention. FIG. 3 is a diagram illustrating a hill-climbing driving operation of the imaging apparatus according to the first embodiment of the present invention. The figure which shows the structure of the imaging device 200 which concerns on 2nd Embodiment of this invention. 9 is a flowchart showing hybrid AF control of the imaging apparatus according to the second embodiment of the present invention.

Explanation of symbols

100, 200 Imaging device

Claims (7)

A first photoelectric conversion sensor that photoelectrically converts a first subject image formed by the photographing optical system to generate an image signal of the first subject;
A second photoelectric conversion sensor that photoelectrically converts a second subject image to generate a distance signal indicating a distance to the second subject;
First focus adjusting means for adjusting the focus of the photographing optical system based on the image signal;
Second focus adjusting means for adjusting the focus of the photographing optical system based on the distance signal;
Subject detection means for detecting a subject region from the image signal;
Determining means for determining whether the first subject and the second subject are different based on the size of the subject region and the distance to the subject;
Control means for controlling not to perform focus adjustment by the second focus adjustment means when the determination means determines that the first subject and the second subject are different;
An imaging apparatus comprising: The photographing optical system includes an optical element for focus adjustment,
The control means includes
First calculating means for calculating an in-focus position of the optical element for the focus adjustment in the photographing optical system according to the size of the subject area including the first subject;
The second focus adjustment means includes:
Second calculating means for calculating an in-focus position of the optical element for focus adjustment in the photographing optical system according to a distance to the second subject indicated by the distance signal;
The control means includes
When the difference between the in-focus position calculated by the first calculating means and the in-focus position calculated by the second calculating means is less than a first threshold, the focus adjustment by the second focus adjusting means When the difference between the in-focus position calculated by the first calculating means and the in-focus position calculated by the second calculating means is equal to or greater than the first threshold value, the first focus adjustment is performed. The imaging apparatus according to claim 1, further comprising first switching means for switching a focus adjustment operation so as to perform focus adjustment by the means. The photographing optical system includes an optical element for focus adjustment,
The control means includes
Distance calculating means for calculating a distance to the first subject in accordance with a size of the subject area including the first subject;
When the difference between the distance to the first subject calculated by the distance calculating means and the distance to the second subject indicated by the distance signal is less than a second threshold, the second focus The focus is adjusted by the adjusting means, and the difference between the distance to the first subject calculated by the distance calculating means and the distance to the second subject indicated by the distance signal is equal to or greater than the second threshold. The first switching means for switching the focus adjustment operation so as to perform the focus adjustment by the first focus adjustment means,
The imaging apparatus according to claim 1, comprising: The first focus adjusting means includes
Focus detection means for acquiring an evaluation value of a focus detection area corresponding to the subject area including the first subject from the image signal, and detecting an in-focus state of the photographing optical system based on the acquired evaluation value; ,
First focusing means for moving the optical element for focus adjustment to a focus position in accordance with the focus state detected by the focus detection means;
Including
The second focus adjustment means includes:
4. The imaging apparatus according to claim 2, further comprising a second focusing unit that moves the optical element for focus adjustment to a focusing position calculated by the second calculation unit. 5. . The photographing optical system includes an optical element for focus adjustment,
The control means includes
A third computing means for computing a focusing direction of the optical element for the focus adjustment in the photographing optical system in accordance with a change in the size of the subject area including the first subject;
A fourth computing means for computing a focusing direction of the optical element for the focus adjustment in the photographing optical system in accordance with a change in the distance to the second subject indicated by the distance signal;
When the in-focus direction calculated by the third calculating means and the in-focus direction calculated by the fourth calculating means are the same, focus adjustment is performed by the second focus adjusting means, and the third calculation is performed. When the in-focus direction calculated by the means is different from the in-focus direction calculated by the fourth calculating means, the second focus adjustment operation is switched so as to perform the focus adjustment by the first focus adjusting means. Switching means;
The imaging apparatus according to claim 1, comprising: The first focus adjusting means includes
Focus detection means for acquiring an evaluation value of a focus detection area corresponding to the subject area including the first subject from the image signal, and detecting an in-focus state of the photographing optical system based on the acquired evaluation value; ,
First focusing means for moving the optical element for focus adjustment to a focus position in accordance with the focus state detected by the focus detection means;
Including
The second focus adjustment means includes:
Second computing means for computing an in-focus position of the photographing optical system in accordance with a distance to the second subject indicated by the distance signal;
Second focusing means for moving the optical element for focus adjustment to a focus position calculated by the second calculation means;
The imaging apparatus according to claim 5, comprising: The imaging apparatus according to claim 1, wherein the first subject included in the subject region is a human face.

Images