JP2006258943A - Autofocus system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an autofocus system constituted so that an operator can rapidly recognize that a target subject can not be tracked by providing an informing means for informing of such a situation that the target subject can not be tracked in an automatic tracking function for bringing the target subject into focus by autofocus (AF) while tracking the target subject on an image plane. <P>SOLUTION: In a television camera or the like, a tracking device 16 stores the image of the target subject to be tracked as a reference pattern image and detects the image most matching with the reference pattern image out of photographic images of newly fetched frames by pattern matching, and detects the position of the target subject. If it can not track the target subject, a reference pattern frame showing the fetching range of the reference pattern image is displayed with flickering in a view finder 18. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an autofocus system, and more particularly to an autofocus system having an automatic tracking function for tracking a desired target subject as a focus target on a screen of a captured image of a camera.

  In an imaging system that converts an image of a subject into an electric signal (image signal) by a photographing element (CCD or the like) like a television camera, a contrast method is generally adopted as an autofocus (hereinafter referred to as AF) method. ing. In the contrast method, the contrast of the subject image is detected from the image signal captured by the image sensor, and the focus of the photographic lens is controlled so that the contrast becomes the highest, thereby automatically focusing on the best focus state (in-focus state). This is a method of matching.

  In AF such as a contrast method, the entire subject within the shooting range of the camera is not targeted for AF, but only the subject within a part of the shooting range is often targeted. In contrast-based AF, an image signal in a range targeted for AF is extracted from image signals captured by the entire imaging area of the image sensor, and focus is performed so that the contrast of the image signal in the extracted range is the highest. By controlling this, the target of AF is limited to only a certain range of subjects. In the present specification, the range of the subject to be AF in the shooting range of the camera or the image range of the subject to be AF in the entire range of the shot image of the camera is referred to as an AF area. A frame indicating the outline of the frame is referred to as an AF frame.

Conventionally, when a single AF area is fixedly set at a predetermined position on the screen of a captured image, a rectangular AF area is normally set at the center of the screen. There is also known one in which the position of the AF area can be changed (for example, see Patent Document 1).
JP 2002-365519 A

  By the way, when the AF area can be changed to a desired position and the subject to be focused is an object that moves on the screen, the operator operates an operation device such as a trackball or a joystick. It is necessary to move the position of the AF area in accordance with the movement of the target subject. For this reason, there has been a problem that the operation is troublesome and requires attention.

  Therefore, if the AF area is automatically tracked with respect to the moving subject, it is effective because the operator does not have to operate the position of the AF area. For example, a so-called pattern matching technique is known as a method for detecting a specific pattern image from a predetermined image, and the position of a specific target subject on the screen can be detected by applying this technique. By moving the AF area to the position of the detected target subject, the AF area can be tracked to the target subject.

  However, even if an automatic tracking function for tracking a desired target subject is mounted as an object to be focused in this way, the function does not always operate normally. In particular, even if the automatic tracking function operates normally until a certain point in time, there is a risk that the automatic tracking function will not operate normally and become unable to track if there is a significant change in the image of the subject or its background. is there. In this case, depending on the automatic tracking function as it is, the position of the target subject and the position to be focused by AF are greatly shifted, and an unexpected situation occurs in which the subject is out of focus. For this reason, when tracking is impossible, it is necessary for the operator to manually change the focus position (AF area position). However, until now, it is necessary to control whether tracking is performed normally. No proposal has been made for a means that can be instantly recognized by a person.

  The present invention has been made in view of such circumstances, and the operator can instantly recognize whether or not the automatic tracking function for automatically tracking the target subject to be focused by AF is operating normally. An object of the present invention is to provide an autofocus system.

  In order to achieve the object, the autofocus system according to claim 1 includes a target subject position detection unit that detects a target subject position to be tracked as a target to be focused on a screen of a captured image of a camera, and the target Auto focus means for adjusting the focus of the optical system of the camera so that the subject at the position detected by the subject position detection means is in focus, and detection of the position of the target subject by the target subject position detection means is normally performed. And a notification means for notifying that tracking is impossible when not received.

  According to the present invention, when it becomes impossible to track the target subject to be focused, the operator can instantly recognize that fact by the notification means.

  According to a second aspect of the present invention, the autofocus system according to the first aspect of the present invention includes a viewfinder that displays a photographed image of the camera, and the target subject position detection unit uses the target subject image as a reference pattern image. As the position of the target subject is detected by detecting the position of the image that best matches the reference pattern image within the range of the captured image of the camera by pattern matching processing, and the reference pattern image And the notifying unit detects whether the position of the target subject is normally detected by the target subject position detecting unit and when the target subject position is not normally detected. The range in which the reference pattern image is captured in the viewfinder It is characterized by displaying the reference pattern frame in a different manner.

  In the present invention, when pattern matching is used as a method for detecting the position of the target subject, a reference pattern frame indicating a range in which the reference pattern image is captured as an image of the target subject is displayed on the viewfinder, and the display mode thereof is changed. By changing, it is notified that tracking is impossible. For example, when tracking is performed normally, the reference pattern frame is displayed continuously (non-flashing display), and when tracking becomes impossible, the reference pattern frame is displayed blinking or the reference pattern frame is displayed. It is possible to notify the operator that tracking is impossible by changing the display color or the like.

  According to a third aspect of the present invention, there is provided the autofocus system according to the first aspect of the present invention, further comprising a viewfinder for displaying a photographed image of the camera, wherein the autofocus means is a contrast type autofocus, and the camera The focus adjustment is performed based on the contrast of an image within a predetermined AF area of the photographed image, and the position of the AF area is set to the position detected by the target subject position detection unit. An AF frame indicating the range of the AF area on the viewfinder so that it can be discriminated whether the detection of the position of the target subject by the target subject position detection means is performed normally or not. Is displayed in a different manner.

  In the present invention, when the AF frame is displayed on the viewfinder as in the contrast type AF, it is notified that tracking is impossible by changing the display mode of the AF frame. For example, when tracking is normally performed, the AF frame is continuously displayed (non-flashing display), and when tracking becomes impossible, the AF frame is flashed or the display color of the AF frame is changed. It is possible to notify the operator that tracking is impossible by changing the setting.

  According to a fourth aspect of the present invention, the autofocus system according to the first aspect of the present invention is provided with an operation unit for manually changing a position on the screen to be focused by the autofocus unit, and the operation unit. A display device, wherein the notification means can distinguish between a case where the detection of the position of the target subject by the target subject position detection means is performed normally and a case where the detection is not performed normally. The display mode is controlled.

  In the present invention, when an operation unit for manually changing the focus position is provided, a display indicating that tracking is impossible is displayed on the operation unit. For example, it is possible to notify the operator that tracking is not possible by switching the light emission state and light emission color of a lamp such as an LED between normal time and when tracking is not possible.

  According to a fifth aspect of the present invention, in the invention according to the first, second, third, or fourth aspect, the target subject position detecting means stores in advance an image of the target subject as a reference pattern image. The position where the correlation value indicating the degree of coincidence with the reference pattern image is maximized is detected as the position of the target subject within the range of the photographed image of the camera, and the notifying means has a predetermined correlation value. When the value is smaller than the threshold value, it is determined that the position of the target subject has not been normally detected.

  In the present invention, when pattern matching (normalized correlation pattern matching) is used to detect the position of the target subject, an image that most closely matches the reference pattern image (target subject image) is detected from the range of the captured image. When the correlation value is smaller than a predetermined threshold value, the detected image is not recognized to match the reference pattern image, so that it is determined that the target subject is not normally detected. Yes.

  According to the autofocus system of the present invention, the operator can instantly recognize whether or not the automatic tracking function is operating normally.

  Hereinafter, preferred embodiments of an autofocus system according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing the overall configuration of an imaging system to which an autofocus system according to the present invention is applied. The image pickup system shown in FIG. 1 is an image pickup system used for shooting with, for example, a broadcast television camera. In the figure, a camera head 10 with a replaceable lens, and a shooting lens (optical) mounted on a lens mount of the camera head 10 A lens device 12, a frame operation unit 14, a tracking device 16 and the like provided with a system) are shown.

  The camera head 10 is equipped with an image sensor (for example, a CCD), a required signal processing circuit, and the like, and an image formed by the photographing lens of the lens device 12 is photoelectrically converted by the image sensor and then subjected to signal processing. Necessary signal processing is performed by the circuit. A video signal in a predetermined format generated by the signal processing circuit is output from the video signal output terminal of the camera head 10 to an external device. Further, the camera head 10 is provided with a view finder (monitor) 18 for composition confirmation, etc., and a video signal from the camera head 10 is given to the view finder 18 and is photographed by the camera head 10. A real-time image (video) is displayed on the screen of the viewfinder 18. Further, information on an AF area that is a target range of autofocus (AF), for example, an AF frame, is also displayed on the screen of the viewfinder 18.

  The lens device 12 includes a photographing lens (optical system) (not shown) attached to a lens mount of the camera head 10, and an image of a subject is formed on the imaging surface of the imaging element of the camera head 10 by the photographing lens. . The photographing lens is provided with movable parts for adjusting photographing conditions such as a focus lens group, a zoom lens group, and a diaphragm as its constituent parts. These movable parts are electrically driven by a motor (servo mechanism) (not shown). It is designed to be driven. For example, the focus lens group and zoom lens group move in the optical axis direction, and the focus (subject distance) adjustment is performed by moving the focus lens group, and the focal length (zoom magnification) adjustment is performed by moving the zoom lens group. Is done. In the system relating to autofocus as in the present embodiment, it is sufficient that at least the focus lens group can be driven electrically, and other movable parts may be driven only manually. Further, when the predetermined movable part is electrically driven in accordance with the operation of the operator, it is based on a control signal output in accordance with the operation of the operator from an operation unit (not shown) (such as an operation unit of a controller connected to the lens device 12). Thus, the operation of the movable part is controlled, but details are omitted.

  As shown in the figure, the lens device 12 is equipped with a lens CPU 20 that performs overall control of the lens device 12, an AF processing unit 22 that executes autofocus (AF) processing, an AF imaging circuit 24, and the like. Yes. The AF image pickup circuit 24 is disposed in the lens device 12 to acquire a video signal for AF processing, and outputs an image pickup device (CCD or the like) or an output signal of the image pickup device as a video signal of a predetermined format. Etc. The image pickup element of the AF image pickup circuit 24 is referred to as an AF image pickup element. The video signal output from the AF imaging circuit 24 is a luminance signal.

  On the imaging surface of the AF imaging element, subject light branched from the subject light incident on the imaging element of the camera head 10 is imaged by a half mirror or the like disposed on the optical path of the photographing lens. The shooting range and subject distance (distance of the subject in focus) with respect to the imaging area of the AF imaging element are configured to match the shooting range and subject distance with respect to the imaging area of the imaging element of the camera head 10 and are used for AF. The captured image captured by the image sensor matches the captured image captured by the image sensor of the camera head 10. Note that it is not necessary for the shooting ranges of the two to be completely the same. For example, the shooting range of the AF imaging device may be a larger range including the shooting range of the imaging device of the camera head 10. Further, the image signal from the camera head 10 may be supplied to the AF processing unit 22 without providing an AF image sensor.

  The AF processing unit 22 acquires a video signal from the AF imaging circuit 24, and calculates a focus evaluation value indicating the level of contrast of the subject image based on the video signal. For example, after extracting a high-frequency component signal of a video signal obtained from an AF image sensor with a high-pass filter, a signal in a range corresponding to an AF area that is an AF target range among the high-frequency component signal Are accumulated one screen at a time. The integrated value obtained for each screen in this manner indicates the level of contrast of the subject image, and is given to the lens CPU 20 as a focus evaluation value. The AF area range is designated by the lens CPU 20 as will be described later.

  As will be described in detail later, the lens CPU 20 acquires AF frame information (AF frame information) indicating the range (contour) of the AF area from the frame operation unit 14, and the range within the AF frame designated by the AF frame information. Is designated to the AF processing unit 22 as an AF area. Then, the focus evaluation value obtained from the image (video signal) in the AF area is acquired from the AF processing unit 22, and the acquired focus evaluation value is maximum (maximum), that is, the contrast of the subject image in the AF area is maximum. The focus lens group is controlled so that For example, a hill-climbing method is generally known as a control method for a focus lens group based on a focus evaluation value, and the focus evaluation value starts to decrease by moving the focus lens group in a direction in which the focus evaluation value increases. Is detected, the focus lens group is set at that position. Thereby, the subject in the AF frame is automatically focused.

  The frame operation unit 14 includes an operation member for the operator to specify the setting contents of the AF frame such as the position, size, and shape of the AF frame. As shown in FIG. 2, the AF frame 50 indicates the outline of the AF area 52 that is an AF target range with respect to a shooting range or a shot image (screen) of the imaging element of the camera head 10. When the operation member is operated by the operator, the frame operation unit 14 sets and changes setting contents such as the position of the AF frame in accordance with the operation. In the present embodiment, the shape of the AF frame is not particularly mentioned, and it is assumed that the aspect ratio is set to a constant rectangular shape. Further, the setting contents such as the position of the AF frame by the operation member of the frame operation unit 14 are set by the change amount corresponding to the operation amount of the subsequent operation member based on the setting contents of the AF frame before the operation. This is done by making changes. For example, as for the position of the AF frame, the AF frame is displaced in the vertical and horizontal directions by a direction and a movement amount corresponding to the rotation direction and rotation amount of the trackball. Also, if the point that determines the position of the AF frame (the center position of the rectangular AF frame in the present embodiment) within the shooting range (screen of the captured image) is referred to as an AF point, the position of the AF frame is the position of the AF point. Is determined by setting

  On the other hand, when the operation member of the frame operation unit 14 is not operated and the operator is not instructed to change the setting contents of the AF frame, the setting contents of the AF frame are set by the AF frame information given from the tracking device 16 described later. Set and change. The frame operation unit 14 transmits AF frame information indicating the setting contents of the AF frame set or changed by the operation of the operator or the AF frame information from the tracking device 16 to the lens CPU 20 in accordance with a request from the lens CPU 20. As a result, the AF target range is set to the AF frame range set and changed in the frame operation unit 14.

  The tracking device 16 automatically changes the position of the AF area (AF frame) in accordance with the movement of the image of the target object while detecting the image of the target object (target subject) specified by the operator on the captured image. This is a device for realizing an automatic tracking function (automatic tracking), and when the manual operation for changing the AF frame is not performed by the operator, the AF frame is automatically tracked by the tracking device 16, and the operator When the manual operation for changing the AF frame is performed, the manual operation has priority over the tracking device 16, and the AF frame is changed according to the manual operation of the operator. It is also possible to turn off the automatic tracking function and enable only manual operation.

  The frame operation unit 14 also transmits AF frame information indicating the setting contents of the AF frame set and changed as described above to the camera head 10, and places the AF frame at a corresponding position on the screen of the viewfinder 18. Display. As a result, the operator can recognize the position of the AF frame at that time while looking at the viewfinder 18.

  Further, as will be described later, the tracking device 16 stores an image of the object as a reference pattern image in order to automatically track the AF frame to a desired object, and the position of the object on the screen by pattern matching processing. Processing to detect is performed. The frame operation unit 14 acquires the range in which the reference pattern image is captured by the tracking device 16 from the tracking device 16 as reference pattern frame information, and transmits the reference pattern frame information to the camera head 10 to capture the reference pattern image. A reference pattern frame indicating a range (outline) can be displayed at a corresponding position on the screen of the view funder 18. The display pattern of the reference pattern frame (continuous display, blinking display, etc.) can also be changed. When the tracking function is operating normally, the reference pattern frame is displayed continuously (non-displayed). When the tracking function is not operating normally, that is, when tracking is impossible, the reference pattern frame is displayed in a blinking manner.

  The tracking device 16 includes an image processing unit 26, an image input unit 28, a serial communication interface 30, and the like. The image input unit 28 acquires the video signal (luminance signal) obtained by the AF imaging circuit 24 via the AF processing unit 22 and obtains the image obtained from the video signal in response to a request from the image processing unit 26. The image data of the image is given to the image processing unit 26.

  Based on the image data acquired from the image input unit 28, the details of which will be described later, the image processing unit 26 performs pattern matching as described later on the movement of the image of the object specified by the operator on the captured image (screen). The position of the AF frame (AF point) for detecting the process and causing the AF frame to follow the movement of the object is obtained. Then, AF frame information indicating the position of the AF frame is transmitted to the frame operation unit 14 via the serial communication interface 30, and the position of the AF frame when automatically tracking the AF frame is designated.

  Next, the tracking process in the image processing unit 26 in the tracking device 16 will be described in detail with reference to the flowchart of FIG. First, the operator operates the operation member of the frame operation unit 14 while viewing the image displayed on the screen of the viewfinder 18 and the AF frame, and the whole or a part of the object to be tracked as the focus target is displayed in the AF frame. To pay. As a result, the object is brought into focus by AF processing in the lens CPU 20.

  Subsequently, the operator presses the determination button of the frame operation unit 14. As a result, a reference pattern image setting instruction (reference pattern image storage instruction) is given from the frame operation unit 14 to the image processing unit 26.

  When an instruction to set a reference pattern image is given, the image processing unit 26 reads AF frame information indicating the setting contents of the AF frame at that time from the frame operation unit 14 via the serial communication interface 30 and also the lens device 12. The captured image (image data) for one screen (one frame) is taken in from the video signal supplied from the AF processing unit 22 to the image input unit 28 (step S10). The captured image captured at this time is referred to as an A image. Further, when the video signal given from the AF processing unit 22 to the image input unit 28 is, for example, an interlaced video signal composed of two fields of video signals for one screen (one frame). The captured image captured as one screen from the input unit 28 may be a captured image obtained from a video signal for one field, or may be a captured image obtained from a video signal for two fields. In this specification, when a captured image for one screen is a captured image obtained from a video signal for one field in the interlace method or a video signal for two fields, or a video signal for one frame in the non-interlace method. Even if it is a case where it is set as the picked-up image obtained by, one screen shall be called one frame.

  Subsequently, the image processing unit 26 extracts an image within the range from the A image by setting a range slightly smaller than the AF frame specified by the AF frame information as a range of the reference pattern frame from the A image captured in step S10. Then, it is set (stored) as a reference pattern image (step S12).

  Here, the reference pattern image is image data used in a pattern matching process to be described later, and the reference pattern frame for setting the initial reference pattern image may be the same range as the AF frame, for example. The reference pattern frame may be set by setting the AF frame range so as to be an appropriate range (range of position, size, and shape) as the reference pattern image capture range. In this case, after the setting of the reference pattern image is completed, the AF frame may be reset to an appropriate range as the AF target range. In addition, when setting an initial reference pattern image, the reference pattern frame is displayed on the viewfinder 18 separately from the AF frame, and the range of the reference pattern frame can be set by the operator's operation separately from the AF frame. It may be.

  When the setting of the reference pattern image in step S12 is completed, the image processing unit 26 repeatedly executes the following processes of step S14 to step S28. First, a new captured image for one screen is taken from the image input unit 28 (step S14). Note that the captured image acquired in step S14 is referred to as a B image.

  Subsequently, the image processing unit 26, in a predetermined pattern detection range set within the screen range of the B image, the range (position) of the image that most closely matches the stored reference pattern image (having the highest correlation value). Is detected by a known pattern matching process. Thereby, the position on the screen of the object set as the reference pattern image is detected (step S16).

  For example, when the position of the image that best matches the reference pattern image is detected using normalized correlation pattern matching, the following calculation of the correlation value (correlation coefficient) r is performed.

The pixel value of the reference pattern image is represented by g, the pixel value of the target region of the B image for obtaining the correlation value r with the reference pattern image is represented by f, and the pixel value (luminance value) of each pixel in these regions ) Is the sum of (Σg), (Σf), the sum of squares of the pixel values of each pixel is (Σg ² ), (Σf ² ), and the pixel of the corresponding pixel between the reference pattern image and the image of the region of interest of the B image When the sum of the products of the values is (Σfg) and the number of pixels of the reference pattern image is n,
r ² = {n (Σfg) −ΣfΣg} ² / [{nΣf ² − (Σf) ² } {nΣg ² − (Σg) ² }
Is used to calculate the correlation value r. Then, by calculating the above equation for the region of interest at each position while changing the position of the region of interest within the pattern detection range of the B image, the correlation of each position with respect to the region of interest within the pattern detection range of the B image is performed. The value r is calculated.

  The correlation value r takes a value in the range of 0 ≦ r ≦ 1, and indicates a correlation value closer to a value of 1 for a region of interest having an image with a higher degree of matching with the reference pattern image. Therefore, the image of the region of interest when the correlation value r is maximized is detected as the image that most closely matches the reference pattern image. The position (range) of the region of interest at that time is detected as the position of the image that most closely matches the reference pattern image, that is, the position on the screen of the object to be tracked.

  Next, the image processing unit 26 determines whether or not a reference pattern image is detected in the B image (step S18). As described above, when the position of the image that best matches the reference pattern image is detected by normalized correlation pattern matching, whether or not the reference pattern image is detected is determined by the correlation when the image that best matches the reference pattern image is detected. The determination is made based on whether or not the value (that is, the correlation value indicating the maximum among the correlation values r for the region of interest at each position described above) is equal to or greater than a predetermined threshold value. If the correlation value is equal to or greater than the predetermined threshold value, YES is determined in step S18, and if the correlation value is smaller than the predetermined threshold value, NO is determined in step S18.

  When it determines with YES in step S18, the image process part 26 determines whether the target object moved on the screen based on the position of the target object detected by step S16 (step S20). If YES is determined, the position (AF point) of the AF area is displaced in the same direction as the moving direction by the amount of movement of the object, and AF frame information indicating the position of the AF area is displayed on the frame operation unit 14. Send to. Thereby, the setting content of the AF frame, that is, the position of the AF frame is updated (step S22). When the position of the AF frame is updated, the AF target range in the lens device 12 is updated accordingly, and the position of the AF frame displayed on the screen of the viewfinder 18 is updated. If it is determined as NO in step S20, the process of step S22 is not executed.

  Next, the image processing unit 26 captures an image in the B image detected as the image that most closely matches the reference pattern image by the pattern matching process in step S16, and updates the reference pattern image with the image (step S16). S24). Then, the reference pattern frame information indicating the range (contour) of the reference pattern frame indicating the fetched range of the updated reference pattern image is transmitted to the frame operation unit 14. As a result, the reference pattern frame 54 is normally displayed on the screen of the view fine 18 as shown in FIG. 4A through the frame operation unit 14 (step S26). The normal display is a continuous display that does not blink with respect to the blinking display described later. Further, as shown in the figure, the reference pattern frame 54 is displayed together with the AF frame 50.

  On the other hand, if NO is determined in step S18, the reference pattern frame information indicating the range of the reference pattern frame up to that time is transmitted to the frame operation unit 14 without updating the reference pattern image as described above. Tracking impossible information indicating that the reference pattern image has not been detected, that is, tracking is impossible, is transmitted to the frame operation unit 14. As a result, the reference pattern frame 54 blinks on the screen of the viewfinder 18 as shown in FIG. 4B through the frame operation unit 14 (step S28). By blinking the reference pattern frame in this manner, the operator can immediately recognize that fact, and can take measures such as switching the operation of the AF frame to manual.

  When the process of step S26 or step S28 is completed, the process returns to step S14, and the process from step S14 is repeatedly executed.

  In the above embodiment, the case where the reference pattern frame is set separately from the AF frame has been described. However, the AF frame can be used as the reference pattern frame, and in this case, the display of the reference pattern frame is performed. Similarly to the above, the AF frame displayed on the viewfinder 18 is switched from the normal display to the blinking display to notify the operator that tracking is impossible (whether the automatic tracking function is operating normally). May be.

  Even if the AF frame is not the reference pattern frame (if the AF frame and the reference pattern frame are different), the reference pattern frame is displayed on the viewfinder 18 without being displayed on the viewfinder 18. The operator may be notified that tracking is impossible by switching the AF frame to be displayed from normal display to blinking display.

  Also, it is not possible to track by changing the display mode of the frame by a desired method, such as changing the color of the frame, instead of notifying that the tracking is impossible by blinking the reference pattern frame or the AF frame. May be notified.

  Furthermore, in addition to using the reference pattern frame and AF frame as a method for notifying that tracking is impossible, character information, a warning lamp, etc. may be displayed on the screen of the viewfinder 18, or the frame operation unit 14 or the like may be displayed. A lamp such as an LED may be installed, and the display state of the lamp may be switched (turned off, lit, flashed, etc.) depending on whether the automatic tracking function is operating normally.

  Moreover, although the case where pattern matching was used as a method for detecting the position on the screen of the object to be tracked as the object to be focused has been described in the above embodiment, other methods may be used. For example, it is possible to detect the position of the object to be tracked on the screen based on the color information of the object to be tracked, a predetermined mark attached to the object, or the like. Even when such other methods are used, when tracking is impossible, the operator can be notified of this by a predetermined method.

  Moreover, in the said embodiment, although the lens apparatus 12, the frame operation part 14, and the tracking apparatus 16 were illustrated as a separate apparatus, any two or all may be an integral apparatus. In the above embodiment, an operation member (for example, a determination switch for determining an object) related to the processing of the tracking device 16 is also provided in the frame operation unit 14, but may be provided in the tracking device 16.

  In the above-described embodiment, the image signal is acquired for the AF by using an image sensor dedicated for AF that is different from the image sensor for the camera head 10, but the image obtained by the image sensor for the camera head 10 for AF is used. A signal may be used. However, if the AF video signal is obtained from the AF-dedicated imaging device as in the above embodiment, the HD signal is obtained when the camera head 10 is compatible with a high-definition (HD) television system. Since it is possible to perform AF without using a lens, it is advantageous for miniaturization and power saving.

  In the above embodiment, the contrast type AF is used. However, the present invention can be applied even when an AF other than the contrast type is used.

FIG. 1 is a block diagram showing the overall configuration of an imaging system to which an autofocus system according to the present invention is applied. FIG. 2 is a diagram illustrating an AF frame. FIG. 3 is a flowchart showing the procedure of the tracking process in the tracking device. FIG. 4 is a diagram illustrating a reference pattern frame used for displaying that tracking is impossible.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Camera head, 12 ... Lens apparatus, 14 ... Frame operation part, 16 ... Tracking apparatus, 18 ... Viewfinder, 20 ... Lens CPU, 22 ... AF process part, 24 ... Imaging circuit for AF, 26 ... Image process part, 28 ... Image input unit, 30 ... Serial communication interface, 50 ... AF frame, 52 ... AF area, 54 ... Reference pattern frame

Claims (5)

Target subject position detection means for detecting the position of the target subject to be tracked as a target to be focused on the screen of the photographed image of the camera;
Autofocus means for adjusting the focus of the optical system of the camera so that the subject at the position detected by the target subject position detection means is in focus;
A notification means for notifying that tracking is impossible when the detection of the position of the target subject by the target subject position detection means is not normally performed;
An autofocus system characterized by comprising A viewfinder for displaying images taken by the camera;
The target subject position detecting means stores in advance the image of the target subject as a reference pattern image, and detects the position of the image that best matches the reference pattern image within the range of the image captured by the camera by pattern matching processing. And detecting the position of the target subject and storing the image that best matches the reference pattern image as a new reference pattern image,
The notifying means can identify the reference pattern image in the viewfinder so that it can be discriminated between the case where the position of the target subject is detected normally by the target subject position detecting means and the case where the target subject position is not normally detected. 2. The autofocus system according to claim 1, wherein the reference pattern frame indicating the captured range is displayed in a different manner. A viewfinder for displaying images taken by the camera;
The autofocus means is a contrast type autofocus, and performs focus adjustment based on the contrast of an image within a predetermined AF area of the photographed image of the camera and is detected by the target subject position detection means. Set the position of the AF area to the position
The notification means allows the viewfinder to identify the range of the AF area so that the target subject position detection means can distinguish between a case where the detection of the position of the target subject is performed normally and a case where the detection is not performed normally. The autofocus system according to claim 1, wherein the AF frame indicating the difference is displayed in a different manner. An operation unit for manually changing a position on the screen to be focused by the autofocus unit; and a display provided in the operation unit,
The notifying unit controls the display mode of the display so that it can be distinguished between a case where the detection of the position of the target subject by the target subject position detection unit is performed normally and a case where the detection is not performed normally. The autofocus system according to claim 1. The target subject position detecting means stores in advance an image of the target subject as a reference pattern image, and the correlation value indicating the degree of coincidence with the reference pattern image is maximized within the range of the photographed image of the camera. Detecting the position as the position of the target subject,
The notification means determines that the detection of the position of the target subject has not been normally performed when the correlation value is smaller than a predetermined threshold value. 4. The autofocus system according to 4.

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