JP4845696B2 - Focus adjustment device, imaging device, and control method thereof - Google Patents

Description

  The present invention relates to a focus adjustment device having a focus adjustment function, an imaging device including the focus adjustment device, and a control method thereof.

  Conventionally, there has been known a method in which a photographer selectively or freely sets a focus detection frame (hereinafter referred to as an AF frame) at any position on the screen and performs autofocus in a focus detection area corresponding to the position of the AF frame. ing. For example, there has been proposed an imaging apparatus in which a photographer can freely move an AF frame left and right and up and down by operating a cross switch and the like. As a result, autofocus can be performed at the position intended by the photographer, and the degree of freedom in composition of shooting is improved. For example, there has been proposed an imaging apparatus that takes a picture while focusing only on a portion selected by a photographer (see Patent Document 1). In this document 1, a frame can be freely set by a photographer's operation of a cross key, an auxiliary button, or the like. For example, the size of the AF frame can be enlarged by the photographer operating the cross key while pressing the auxiliary button. The AF frame can be easily set by pressing the enter button after changing the size.

In addition, an imaging apparatus is proposed that detects a face from a captured image, automatically sets an AF frame at the face position, and focuses on the face. (See Patent Document 2)
JP 2006-128793 A JP 2001-215403 A

  However, in the above document 2, when there are a plurality of subjects, the AF frame cannot always be set at the face position desired by the photographer. Further, in the above-mentioned document 1, since the photographer has to operate the determination button in order to finish the setting of the AF frame, the operability is poor and there is a possibility that a photo opportunity will be missed.

  Accordingly, the present invention has been made in view of the above-described problems, and an object thereof is to improve operability when performing focus control on a subject (object) intended by a photographer.

In order to solve such a problem, a technical feature of the present invention is a control method of a focus adjustment device that performs focus adjustment of the imaging optical system based on a focus state detected while moving the imaging optical system. According to the photographer's instruction, the AF frame display position corresponding to the region for detecting the in-focus state is moved, and the focus adjustment is performed after the first period has elapsed since the AF frame was moved. And when a focus adjustment start instruction is given in a second period shorter than the first period, the focus adjustment is controlled before the first period elapses .

  As described above, according to the present invention, it is possible to improve operability when performing focusing control on a subject intended by a photographer.

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

<Description of the device>
FIG. 1 is a block diagram of an electronic camera (imaging device). Reference numeral 101 denotes a focus lens for focusing on an image sensor described later. Reference numeral 102 denotes a photo interrupter that detects the initial position of the focus lens 101, 103 denotes a motor that drives the focus lens 101, and 104 denotes a focus lens drive circuit that inputs a drive signal to the motor 103 and moves the focus lens 101. Reference numeral 105 denotes a light amount control member such as an aperture and a shutter, 106 denotes a motor that drives the aperture / shutter 105, and 107 denotes an aperture / shutter drive circuit that inputs a drive signal to the motor 106 to move the aperture / shutter 105. Reference numeral 108 denotes a zoom lens that changes the focal length of the photographing lens. Reference numeral 109 denotes a photo interrupter that detects the initial position of the zoom lens 108, 110 denotes a motor that drives the zoom lens 108, and 111 denotes a zoom lens driving circuit that inputs a drive signal to the motor 110 to move the zoom lens 108. The focus lens 101, the aperture / shutter 105, the zoom lens 108, and the like are also referred to as an imaging optical system. Reference numeral 112 denotes an imaging element which is an imaging means for photoelectrically converting reflected light (subject image) from an object into an electrical signal and outputting an image signal. Reference numeral 113 denotes an A / D converter that converts an analog signal output from the image sensor 112 into a digital signal. Reference numeral 114 denotes a timing signal generation circuit (hereinafter referred to as TG) that generates timing signals necessary for operating the image sensor 112 and the A / D converter 113. Reference numeral 115 denotes an image processor that performs predetermined processing on the image data input from the A / D converter 113, and 116 denotes a buffer memory that temporarily stores the image data processed by the image processor 115. Reference numeral 117 denotes an interface for connection to a recording medium to be described later. Reference numeral 118 denotes a recording medium such as a memory card or a hard disk. Reference numeral 119 denotes a microcontroller (hereinafter referred to as CPU) for controlling the system such as a photographing sequence. Reference numeral 120 denotes a zoom switch for inputting a signal for instructing the start and stop of the zoom operation to the CPU. Reference numeral 121 denotes a switch (hereinafter referred to as SW1) for instructing photographing preparation such as the start of focus adjustment and the start of photometry operation, and 122 designates photographing processing such as main exposure and recording operation after the operation of the photographing preparation instruction switch 121. Is a photographing process instruction switch (hereinafter referred to as SW2). When SW2 is operated, a photographing process is performed based on information acquired in accordance with the operation of SW1 (for example, the focus lens is moved to the in-focus position obtained by SW1). Reference numeral 123 denotes a main switch for turning on the system. Reference numeral 124 denotes a mode switch for setting the operation mode of the camera. Reference numeral 125 denotes a program memory in which a program executed by the CPU 119 is stored. Reference numeral 126 denotes a work memory in which various data necessary for the CPU 119 to perform processing according to a program stored in the program memory 125 are written and read. Reference numeral 127 denotes an operation display unit for displaying the operation state of the camera and various warnings. Reference numeral 128 denotes a display unit for displaying an image. For example, an electronic viewfinder (hereinafter referred to as EVF) is considered as an example. The display on the display unit 128 is controlled by the CPU 119. Reference numeral 129 denotes a setting switch for performing various settings. Reference numeral 130 denotes a cross switch used for selecting a menu item displayed on the operation display unit 127 or the EVF 128, or instructing movement of the AF frame position. Reference numeral 131 denotes a face detection unit that detects a face from a captured image signal (image). Reference numeral 132 denotes an AF frame movement switch for instructing movement of the AF frame position. Reference numeral 133 denotes a timer counter that counts the passage of time.

<Overall flow of AF frame setting and AF processing>
Next, the change of the AF frame position displayed in a visible manner on the screen of the display unit 128 and the autofocus control at that position will be described using the flowchart of FIG. First, in S201, the AF frame movement flag is set to FALSE. The AF frame movement flag is a flag indicating that an AF frame movement instruction has been made by operating the AF frame movement switch 132. In S202, the state of the AF frame movement flag is determined. If TRUE, the process proceeds to S209, and if not, the process proceeds to S203. In step S203, face position detection information obtained according to a procedure described later is acquired. In S204, the state of the AF frame movement switch 132 is determined. If it is ON, the process proceeds to S205, and if not, the process proceeds to S202.

  In S205, based on the face detection information acquired in S203, the AF frame display position on the EVF 128 is moved to the next face position. Here, as a method for determining the next face position, the face on the right side of the current face position is selected, and when there is no face on the right side, the face on the leftmost side is selected. In S206, the AF frame movement flag is set to TRUE. In S207, the timer counter 133 is set to zero. In S208, the timer counter 133 is started. The timer counter 133 is counted up as time passes.

  In S209, the state of SW1 is determined. If ON, the process proceeds to S210, and if not, the process proceeds to S213. In S210, the timer counter 133 is stopped. In S211, the position on the image sensor 112 corresponding to the position moved in S205 is set as a focus detection area. In S212, AF processing is performed for the main exposure according to the procedure described later. When the processing is completed, the process proceeds to S201. In this AF process, a focus evaluation value (a value indicating the in-focus state of the imaging optical system) obtained from the focus detection area set in S211 is used.

  In S213, it is determined whether the count value of the timer counter 133 is greater than a predetermined value. In S214, the timer counter 133 is stopped. In S215, the position on the image sensor 112 corresponding to the position moved in S205 is set as the focus detection area.

  In S216, AF processing is started. In this AF process, the focus evaluation value obtained from the focus detection area set in S215 is used. In S217, the state of the AF frame movement switch 132 is determined. If it is ON, the process proceeds to S218. In S218, the AF process is stopped and the process proceeds to S205. In S219, the end of the AF process is determined. If completed, the process proceeds to S201, and if not, the process proceeds to S216.

  By performing the AF frame setting and the AF process as described above, the AF frame display moves to the next position and the AF process according to the photographer's intention becomes smooth. Therefore, it is possible to provide an apparatus that can reliably capture a photo opportunity.

<How to detect faces>
Face detection from the captured image signal (image) is performed by the face detection unit 131 (subject detection unit). Face position information is detected and stored using an image created for display on the EVF 128. While the image is displayed by the EVF 128 (while the image signal captured by the EVF 128 is sequentially displayed), the detection and storage of the face position information is repeated, and the latest face detection result is always stored in the work memory 126. deep. That is, face detection is performed asynchronously with the operation timing of the AF frame movement switch 132 described above. (The position of the frame displayed on the display unit is moved by an instruction to move the frame by operating the AF frame moving switch.)

  As a face detection method by the face detection unit 131, a known method may be used. Various techniques are known as techniques for detecting a face. For example, there is a method using learning represented by a neural network. In addition, there is a technique for identifying parts having physical shape features such as eyes, nose, mouth, and facial contour from image information using template matching. In addition, there is a method using a statistical analysis by detecting a feature amount of image information such as skin color or eye shape (for example, Japanese Patent Laid-Open Nos. 10-232934 and 2000-48184). reference). In addition, it is determined whether the previous face area is near the detected position, the color near the face area is determined in consideration of the color of clothes, or the face identification is performed closer to the center of the screen. There is a method of setting the threshold value for this purpose low. In this embodiment, a face identification process is performed by detecting a pair of eyes (both eyes), a nose, a mouth, and the outline of a face, and determining a face from these relative positions.

<Description of AF frame display operation>
Next, the movement of the AF frame display and the AF operation when configured as in the flowchart of FIG. 2 will be described with reference to FIG.

  FIG. 3 shows an image in which three people are displayed on the EVF 128. First, in the initial state, the AF frame is displayed at the position A in FIG. 3, that is, at the center of the screen. When SW1 is pressed in this state, AF processing is performed based on the focus evaluation value corresponding to this position. Next, when the AF frame movement switch 132 is pressed, the display position of the AF frame is moved to the position B in FIG. When the AF frame movement switch 132 is pressed again, the display position of the AF frame is moved to the position C in FIG. In this way, the display position of the AF frame is sequentially moved each time the AF frame movement switch 132 is pressed. If the AF frame movement switch 132 is pressed while displaying at the position D in FIG. 3, the next display position is not the position A with no face but the position B with the face.

<AF frame movement and AF processing flow>
After the AF frame movement switch 132 is pressed and the display position of the AF frame is moved, the timer counter 133 counts time. When a predetermined time (first period) elapses, AF processing is performed based on the focus evaluation value corresponding to the display position of the AF frame. When the AF frame movement switch 132 is pressed again before the predetermined time has elapsed, the display position of the AF frame is moved and the timer counter is counted again.

  If SW1 is pressed before a predetermined time has elapsed (second period shorter than the first period), the timer counter stops counting and AF processing is performed for the main exposure.

  Further, even after the predetermined time has elapsed and the AF process is started, the state of the AF frame moving switch 132 is determined. If the AF frame movement switch 132 is ON, the AF process is stopped, the AF frame display position is moved, and the timer counter Reset the time.

<Flow of AF processing>
FIG. 4 is a flowchart for explaining AF processing in S212 and S216 of FIG. First, in S401, the focus lens 101 is moved to the scan start position. This scan start position is, for example, the infinite end of the focusable area. In S402, the analog video signal read from the focus detection area on the image sensor 112 set in S211 is converted into a digital signal using the A / D converter 113. Then, the image processor 115 extracts the high frequency component of the luminance signal from the output, and stores it in the work memory 126 as a focus evaluation value. In S403, the current position of the focus lens 101 is acquired and stored in the work memory 126. When a stepping motor is used for the focus lens drive motor 103, the position of the focus lens 101 is determined by the number of relative drive pulses from the initial position detected by the photo interrupter 102. Moreover, you may measure an absolute position using the rotary encoder etc. which are not shown in figure. In S404, it is checked whether the current position of the focus lens 101 is equal to the scan end position. If they are equal, the process proceeds to S406, and if not, the process proceeds to S405. The scan end position is, for example, the closest end of the focusable area. In S405, the focus lens 101 is moved by a predetermined amount in the scan end direction.

  In S406, the maximum value is calculated from the focus evaluation values acquired in S402. In S407, the position of the focus lens 101 (hereinafter referred to as the peak position) when the maximum focus evaluation value calculated in S406 is acquired is stored in the work memory 126. In S408, the focus lens 101 is moved to the peak position stored in the work memory 126 in S407.

<Summary of the embodiment, effects, etc.>
If the AF process is performed immediately after the AF frame display position is moved, the AF process must be completed when the AF frame display is moved to the next position, or the AF process must be stopped. The AF frame display cannot be moved quickly. However, since the AF processing is not performed immediately after the display position of the AF frame is moved by using the above-described embodiment, the AF frame display can be quickly moved to the next position. .

  Even after the AF process is started, if the AF frame movement switch 132 is pressed, the AF process is stopped and the display position of the AF frame is moved. Therefore, without waiting until the AF process ends. The AF frame display can be moved to the next position.

  In addition, if SW1 is pressed during the timing after the AF frame movement instruction, the timing is stopped and AF processing is performed, so that a device that can quickly respond to the photographer's operation and capture the photo opportunity is provided. it can.

  On the other hand, by performing AF processing along with the movement of the AF frame display, the subject at the position where the AF frame is moved can always be brought into focus, so that the photographer's desired subject can be viewed on the EVF 128. Will improve. Also, when SW1 is pressed from this state and AF processing is performed for the main exposure, the processing can be quickly performed because the focus processing is once performed.

  In the above description, the AF process is performed after a predetermined time has elapsed after the AF frame has been moved to a position where the face is present. Similarly, when the AF frame is moved to a position where there is no face, the predetermined time has elapsed. AF processing may be performed later. In this case, the AF frame is moved by operating the cross switch 130. That is, the display position of the AF frame is moved in the direction in which the cross switch 130 is pressed, and the movement is stopped when the cross switch 130 is released. Stop moving when you get to the edge of the screen.

  In the above embodiment, the face detection unit 131 performs the face detection process. However, a subject (target object) may be detected instead of the face detection. For example, it may be possible to cut out and detect a subject image from the background.

  In the above embodiment, the initial AF frame is set by automatically detecting the object. However, the initial frame is set according to a conventionally realized algorithm such as “center-oriented” or “near-point priority” in which the apparatus automatically determines one focus detection area where the main subject is supposed to be present. You may do it. Also in this case, the AF frame is moved in accordance with the photographer's instruction, and when a predetermined time elapses, the AF process is smoothly performed by shifting to the AF process.

  In the above embodiment, when the AF frame movement switch 132 is pressed and SW1 is pressed before the predetermined time has elapsed, the timer counter stops counting and the AF processing is performed for the main exposure. Similarly, when the zoom switch is pressed before the predetermined time has elapsed, the timer counter may be stopped and the zoom operation may be started. In addition, when the mode SW is pressed before the predetermined time has elapsed, the timer counter may be stopped and the camera operation mode setting may be changed. As described above, when the photographer's intention is clear, it is possible to provide an apparatus capable of capturing a photo opportunity reliably by quickly responding to the SW operation.

It is a block diagram of an electronic camera. 6 is a flowchart showing a flow of AF frame position movement and AF processing. It is a figure explaining the movement of the AF frame display position in FIG. It is a figure explaining the AF process in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Focus lens 108 Zoom lens 112 Image pick-up element 117 Interface 118 Recording medium 119 Microcontroller 121 Switch (SW1)
122 Shooting processing instruction switch (SW2)
126 Work memory 127 Operation display unit 128 Electronic viewfinder 129 Setting switch 130 Cross switch 131 Face detection unit 132 AF frame movement switch 133 Timer counter

Claims (6)

Focus adjusting means for adjusting the focus of the imaging optical system based on the in-focus state detected while moving the imaging optical system;
Display control means for controlling the display means to display an AF frame corresponding to the region for detecting the in-focus state;
Movement control means for controlling to move the display position of the AF frame in accordance with a photographer's instruction;
A switch for instructing the start of focus adjustment;
The focus adjustment unit performs focus adjustment after a first period has elapsed since the AF frame is moved by the movement control unit, and performs focus adjustment by the switch during a second period shorter than the first period. A focus adjustment apparatus, wherein when a start instruction is given, focus adjustment is performed before the first period elapses. The focus adjusting means changes the area again when an instruction from the photographer is given by the movement control means while detecting the in-focus state while moving the imaging optical system. The focus adjustment apparatus according to claim 1, wherein focus adjustment is performed after the first period has elapsed since a change. Further comprising an object detecting means for detecting an object from an image output by an imaging means,
The focus adjustment apparatus according to claim 1, wherein the movement control unit moves a display position of the AF frame in correspondence with the detected object. The object detecting means detects a face from the image outputted by the imaging unit, wherein the display control unit, according to claim 3, characterized in that displaying the position of the detected face by the object detecting means focusing device according to. Imaging means for photoelectrically converting an image of a subject formed by the imaging optical system and outputting an image;
Recording means for controlling to record the image obtained using the imaging means on a recording medium;
An imaging apparatus comprising: the focus adjustment apparatus according to claim 1. A focus adjustment device control method for performing focus adjustment of the image pickup optical system based on a focus state detected while moving the image pickup optical system, wherein the focus state is detected in accordance with a photographer's instruction. The display position of the corresponding AF frame is moved, focus adjustment is performed after a first period has elapsed since the AF frame is moved, and focus adjustment is started in a second period shorter than the first period. A control method for a focus adjusting apparatus, wherein when instructed, control is performed so that focus adjustment is performed before the first period elapses.

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