JP2005156995A - Autofocus system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an autofocus system with which the range of an actual AF area can be appropriately displayed on a view finder screen by obtaining the range of an AF area by taking the range of the video area as a reference even when the range (image size) of the video area of a camera is changed between for example, 16:9 and 4:3. <P>SOLUTION: In the autofocus system for a broadcasting television camera, a CCD 36 for AF is arranged in addition to a main CCD 16 for obtaining a recording/reproducing video, and AF is performed based on the image in the AF area out of the images obtained by the CCD for AF 36. Besides, an AF area frame showing the range of the AF area is displayed together with the video photographed by the main CCD 16 on the view finder 20 based on AF area information transmitted from the CPU 42 of a lens device 12 to a camera circuit 18. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an autofocus system, and more particularly to an autofocus system applied to a broadcast television camera or the like.

  In a television camera for broadcasting and a video camera for consumer use, a contrast method is generally employed as an autofocus (AF) method. In contrast AF, for example, the contrast of a captured image is detected from a video signal obtained by photographing a subject, and the focus of the photographing lens is adjusted so that the contrast height becomes maximum (maximum). The height of the contrast of the captured image is quantified by, for example, the magnitude of the integrated value (focus evaluation value) obtained by extracting the high frequency component signal from the video signal and then integrating the high frequency component signal. Will be judged.

  In contrast AF, a subject in the entire shooting range, that is, an image in the entire pixel range (video area) in which an image is effectively captured by the image sensor is not targeted for AF, but one of the video areas. In many cases, an image captured from a certain area is used as an AF target. Note that a range of a subject to be AF-targeted or a pixel range into which an image is captured is referred to as an AF area. When a part of the video area is an AF area, the contrast of the captured image is detected by extracting a video signal in a range corresponding to the AF area.

  Conventionally, an image sensor for AF (in this specification, AF) is separate from the original image sensor for acquiring a video signal for recording or reproduction (referred to as a video image sensor or a main line image sensor in this specification). There is known an autofocus system in which an AF image sensor is provided and AF is performed using a video signal obtained from the AF image sensor. For example, the subject light incident on the photographing lens is split into two subject lights by a half mirror or the like, one image is formed on the image pickup surface of the image pickup device for video, and the other is formed on the image pickup surface of the AF image pickup device. . At this time, the subject distance in which the shooting range of the AF image sensor includes at least the range of the AF area of the shooting range of the video image sensor and the focus on the imaging surface of the AF image sensor is It is configured to be equal to the subject distance focused on the image pickup surface of the image pickup device for video. As a result, focus adjustment is performed based on the video signal obtained by the AF image sensor so that the imaging surface of the image sensor can be focused.

  Further, the subject light guided to the AF imaging element is further branched to form subject light on a plurality of imaging surfaces arranged at different optical path lengths, and based on video signals obtained by these imaging surfaces. An autofocus system called a so-called optical path length difference method for focusing is proposed (for example, see Patent Document 1). In this system, for example, a plurality of image pickup surfaces of the AF image pickup device are arranged so as to focus on the front and rear distances with respect to the subject distance focused on the image pickup surface of the image pickup image pickup device. A focus evaluation value is obtained for each received video signal. Based on the focus evaluation values obtained from the plurality of imaging surfaces, the focus state (front pin, rear pin, in-focus) with respect to the image pickup surface of the image pickup device is detected, and the focus state indicates the in-focus state. Focus adjustment is performed. The optical path length difference type AF has an advantage that an operation such as wobbling for slightly changing the focus to detect a focus state becomes unnecessary.

In recent years, in the field of broadcasting television cameras, a shooting mode (referred to as 4: 3 mode) in which shooting is performed with an image size (video area size) of an aspect ratio of 4: 3 corresponding to a conventional TV screen. And a so-called switchable camera that can switch between a shooting mode (16: 9 mode) for shooting with an image size of an aspect ratio of 16: 9 corresponding to a wide screen on a high definition TV (HDTV). It has been commercialized. In Patent Document 2, if the AF area when shooting in the 4: 3 mode is also applied to the shooting in the 16: 9 mode as it is, the AF area includes a subject outside the screen range in the 16: 9 mode and appears on the screen. Since a problem of focusing on an unfocused subject may occur, it has been proposed to change the AF area between the 4: 3 mode and the 16: 9 mode so that such a problem does not occur.
JP 2002-365517 A Japanese Patent No. 3441882

  By the way, in a broadcast television camera or the like, usually, an image captured by an image sensor is displayed in real time on a viewfinder such as a liquid crystal monitor, and a cameraman uses the image displayed on the viewfinder. Shooting while checking focus and angle of view.

  However, normally, the above-described AF area is not displayed on the viewfinder in a camera used for shooting a moving image, particularly a broadcast television camera. Therefore, when the cameraman performs focusing by AF, there is a problem that it is difficult to determine in which range on the screen the subject to be focused should be placed. Also, if the cameraman can change the position and size of the AF area, the AF can be focused on the subject at an arbitrary position on the screen, so the practicality of the AF is improved. In that case, it is a problem that the cameraman cannot recognize the AF area.

  In view of this, on the viewfinder screen, for example, a method of superimposing and displaying an AF area frame indicating the AF area on the subject image is conceivable so that the range of the AF area can be understood.

  On the other hand, when displaying an AF area frame on the viewfinder, it is necessary to match the actual AF area range with the range surrounded by the AF area frame on the screen. However, when an AF area frame is displayed on the viewfinder with a switchable camera whose image size can be changed as described above, the 4: 3 mode and 16: 9 mode can be used even if the AF area range is constant. The position and size of the AF area frame in the video area are different from those in the mode. Therefore, if the AF area frame is not combined with the subject image in consideration of the image size, there is a problem that the range of the AF area frame on the viewfinder screen is different from the actual AF area range.

  The present invention has been made in view of such circumstances, and even if the range (image size) of the video area in the video image sensor (main line image sensor) is changed, it is displayed on the viewfinder screen. An object of the present invention is to provide an autofocus system capable of appropriately displaying the actual AF area range.

  In order to achieve the object, the autofocus system according to claim 1 is capable of changing to a different aspect ratio in a video area range indicating a pixel range in which an image is effectively acquired on an imaging surface of an imaging unit, An autofocus system for automatically focusing a photographic lens based on an image acquired from an AF area range indicating a target range of autofocus in the video area, wherein the autofocus system is based on the range of the video area. An AF area range calculation unit that calculates a range of the AF area in a video area, and the image acquired by the range of the video area based on the range of the AF area calculated by the AF area range calculation unit And display means for displaying the range of the AF area.

  According to the present invention, even if the range of the video area is changed, the range of the AF area is calculated based on the range of the video area, so that the captured image is displayed on a display such as a viewfinder. At the same time, when the range of the AF area is displayed, the actual range of the AF area can be appropriately displayed.

  According to a second aspect of the present invention, there is provided the autofocus system according to the first aspect of the present invention, wherein the autofocus system according to the first aspect includes a camera body provided with the imaging means, a lens device provided with the photographing lens, and the display means. It is constructed by a monitor that displays an image to be displayed. For example, this system is constructed in a television camera system for broadcasting.

  According to a third aspect of the present invention, in the invention according to the first aspect, the display means displays the range of the AF area with an AF area frame surrounding the range. Thereby, the range of the AF area can be easily recognized.

  According to a fourth aspect of the present invention, there is provided the autofocus system according to the first aspect of the invention, wherein the range of the video area can be changed to a range of aspect ratio 16: 9 and a range of aspect ratio 4: 3. It is characterized by that. For example, this system is effective when a so-called switchable camera that can switch the shooting mode between an image size with an aspect ratio of 16: 9 and an image size with an aspect ratio of 4: 3 is used.

  According to a fifth aspect of the present invention, there is provided an autofocus system according to the first aspect of the present invention, further comprising an AF area changing means for changing the range of the AF area to a desired range. For example, in the case of moving image shooting, it is convenient that the AF area can be changed, which improves practicality.

  According to a sixth aspect of the present invention, there is provided the autofocus system according to the second aspect of the invention, wherein the operating means for designating the AF area range and the AF area range designated by the operating means are designated by the operating means. AF area changing means for changing to the above, and the operation means is an accessory device connected to the lens device. According to the present invention, only when the AF area can be changed, the operation means may be connected to the lens apparatus.

  According to a seventh aspect of the present invention, there is provided the autofocus system according to the first aspect of the present invention, further comprising an AF imaging unit for acquiring an image in the range of the AF area separately from the imaging unit. It is said. For example, the present system can be applied to an optical path length difference type AF.

  The autofocus system according to the present invention can appropriately display the actual AF area range on the viewfinder screen even when the range (image size) of the video area of the camera is changed. .

  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 autofocus system to which the present invention is applied. The system shown in the figure is a system that enables autofocus (AF) in, for example, a television camera for broadcasting, and is mainly constructed by circuits and the like mounted on the camera body 10 and the lens device 12. The camera body 10 is a so-called switcher that can switch the shooting mode between a 4: 3 mode for shooting with an image size of an aspect ratio of 4: 3 and a 16: 9 mode for shooting with an image size of an aspect ratio of 16: 9. It is a bull camera. Three-color separation optics that separates the subject light incident on the camera body 10 through the photographing optical system (photographing lens) of the lens device 12 into three colors of R (red), G (green), and B (blue). A system 14 and CCDs 16 </ b> A to 16 </ b> C that photoelectrically convert R, G, and B subject lights decomposed thereby are provided. In addition, a processing circuit for performing a predetermined process on the signals obtained from the CCDs 16A to 16C and generating a video signal of a predetermined format (for example, NTSC format) is mounted. All other processing circuits are omitted and shown as a camera circuit 18. The CCDs 16A to 16C are original image pickup elements for acquiring video signals for recording or reproduction, and are hereinafter referred to as main line CCDs 16.

  Further, for example, a liquid crystal viewfinder 20 is attached to the camera body 10, and a video signal for displaying an image photographed by the main line CCD 16, an AF area frame to be described later, and the like on the viewfinder 20. Is provided from the camera circuit 18, and the image taken by the main line CCD 16 is displayed on the screen of the viewfinder 20 in real time and necessary information such as an AF area frame is displayed. The viewfinder 20 may be a monitor that is not a liquid crystal.

  The lens device 12 includes a photographing lens for forming an image of subject light on the imaging surface of the main line CCD 16, a circuit for AF, and the like. The photographing lens has a main light path for guiding subject light to the imaging surface of the main line CCD 16, and subject light is branched from the main light path, and the branched subject light is imaged on the AF CCD 36 (hereinafter referred to as AF CCD 36). An AF optical path is provided to guide the light.

  In the main line optical path, a focus lens group 22, a zoom lens group 24 including a zooming system and a correction system, a diaphragm 26, a half mirror 28, and a master lens group 30 are arranged from the previous stage (object side). The subject light that has passed through the main optical path is decomposed into subject light for each of the R, G, and B wavelength regions by the three-color separation optical system 14 of the camera body 10, and the imaging surfaces of the corresponding main CCDs 16 (16A to 16C). Is imaged.

  The focus lens group 22 is driven in the optical axis direction by a motor 38. The motor 38 is driven in accordance with a drive signal given from the CPU 42 to the driver 40, and the focus lens group 22 moves. When the focus lens group 22 moves, the distance (subject distance) of the subject that connects (focuss on) the image point to the imaging surface of the main line CCD 16 changes. The zoom lens group 24 and the diaphragm 26 are also driven manually or by a motor, but are omitted.

  In the half mirror 28, the subject light is split into two, the subject light transmitted through the half mirror 28 travels the main line optical path as it is, and the subject light reflected by the half mirror 28 is guided to the AF optical path. ing.

  When the camera body 10 is a switchable camera as in the present embodiment, in the 4: 3 mode, out of the video area in the 16: 9 mode (the pixel range in which an image is effectively captured by the main line CCD 16). Since the 4: 3 area is used as the video area, the angle of view is reduced by about 20%. Therefore, there are cases where a photographic lens is used in which a ratio converter is detachably arranged on the main optical path of the photographic lens in correspondence with such a switchable camera. In this case, for example, in the 16: 9 mode, a 1 × lens that does not convert the image magnification (1 ×) is arranged on the main optical path, whereas in the 4: 3 mode, instead of the 1 × lens. In addition, a ratio converter 37 indicated by a dotted line in FIG. 1 for increasing the image magnification to about 0.8 is inserted on the main optical path. As a result, the image circle of the photographing lens is reduced along with the reduction of the size (image size) of the video area, so that the angle of view is not reduced even in the 4: 3 mode.

  An AF master lens group 32, a total reflection mirror 34, and an AF CCD 36 are disposed in the AF optical path. The AF master lens group 32 corresponds to the master lens group 30 in the main optical path, and the subject light guided to the AF optical path by the half mirror 28 passes through the total reflection mirror 34 by the image forming action of the AF master lens group 32. Then, an image is formed on the imaging surface of the AF CCD 36.

  As the AF CCD 36, the same kind of CCD as the main line CCD 16 is used, and the size of the entire imaging surface is completely the same as that of the main line CCD 16. In addition, the shooting range (view angle) that is imaged over the entire range of the imaging surface of the AF CCD 36 and the subject distance that is in focus with the imaging surface of the AF CCD 36 completely match the shooting range and subject distance of the main CCD 16. ing. Accordingly, the same image as that captured by the main CCD 16 is captured by the AF CCD 36. The AF CCD 36 is, for example, a monochrome CCD.

  On the other hand, the lens device 12 is provided with a CPU 42, an AF signal processing unit 44, and the like as circuits for AF. The AF signal processing unit 44 detects a focus evaluation value that evaluates the level of contrast of an image in an AF area that is an AF target range, from a video signal (luminance signal) obtained by the AF CCD 36. For example, after an analog video signal obtained by the AF CCD 36 is converted into a digital signal, a high-frequency component signal is extracted by a high-pass filter or the like. Subsequently, only a signal in a range corresponding to the AF area is extracted by the gate circuit or the like from the high frequency component signal. Then, the extracted high frequency component signals in the AF area are integrated for each screen by an adder circuit or the like, and the integrated value is sequentially obtained as a focus evaluation value indicating the level of contrast.

  The CPU 42 drives the motor 38 via the driver 40, moves the focus lens group 22, and sequentially acquires the focus evaluation value from the AF signal processing unit 44, while the focus evaluation value is maximum (maximum), that is, the image. The focus lens group 22 is controlled so as to maximize the contrast. Thereby, the focus of the photographic lens is set to the in-focus state by AF.

  Further, an AF area operation device (AF area operation unit) 46 as shown in FIG. 2 can be connected to the lens device 12, and the operator operates each knob of the AF area operation unit 46. The range of the AF area can be changed to a desired position and size. For example, in FIG. 2, when the position adjustment knobs (horizontal position adjustment knob 48, vertical position adjustment knob 50) are rotated, the position of the AF area is shifted in the horizontal and vertical directions on the screen (in the video area). Can do. On the other hand, when the size adjustment knobs (the horizontal size adjustment knob 52 and the vertical size adjustment knob 54) are rotated, the size of the AF area in the horizontal direction and the vertical direction can be changed.

  In FIG. 1, the CPU 42 acquires information (AF area information) indicating the position and size of the AF area that is changed by the operation of the position adjustment knob and the size adjustment knob from the AF area operation unit 46, and uses the AF area information as the AF area information. Based on this, a signal for designating the range (position and size) of the AF area in the image area of the AF CCD 36 is transmitted to the AF signal processing unit 44. As described above, the AF signal processing unit 44 is an AF designated by the CPU 42 as a pixel range for capturing an image as an AF target, that is, a range in which a signal is extracted by a gate circuit or the like when obtaining a focus evaluation value from a video signal. Set to the range of the area. As a result, the AF target range is set to the AF area range designated by the operation of the AF area operation unit 46.

  If the AF area is not changed, the AF area operation unit 46 does not need to be connected to the lens device 12, and in that case, the AF area is set to a standard position (for example, the center of the screen) and size. . Further, the AF area operation unit 46 does not have to be an accessory (attached device) connected to the lens device 12 in order to specify the range of the AF area. For example, a touch panel is installed on the screen of the viewfinder 20, and The range of the AF area may be designated by a touch operation at.

  In addition, the viewfinder 20 displays in real time an image captured by the main line CCD 16 of the camera body 10 and an AF area frame indicating the range of the AF area superimposed on the image. It has become. Information (AF area information) indicating the range (position and size) of the AF area is transmitted from the CPU 42 to the camera circuit 18, and on the basis of this information, an image of the AF area frame is added to the video obtained from the main line CCD 16. Images are synthesized. The video signal obtained by combining the images in the AF area frame is output from the camera circuit 18 to the viewfinder 20, and the video is displayed on the screen of the viewfinder 20. FIG. 3 is a view showing a screen of the viewfinder 20, and an image captured by the main line CCD 16 is displayed in real time on the screen 20A of the viewfinder 20, and an AF area frame indicating the range of the AF area is shown. 56 is displayed superimposed on the video.

  Although details will be described later, the CPU 42 considers whether the shooting mode of the camera body 10 is the 16: 9 mode or the 4: 3 mode when transmitting the AF area information to the camera circuit 18. AF area information indicating the position and size of the AF area in the selected video area is transmitted, indicating the mode in the camera body 10, that is, the aspect ratio (16: 9 or 4: 3) of the image size. Information is acquired from the camera circuit 18 as aspect ratio information.

  Next, processing related to AF area frame display will be described.

  4A shows an image circle 70 on the imaging surface of the AF CCD 36, a video area 72 indicating a pixel range in which an image is effectively captured by the AF CCD 36, and an AF area 74 indicating an AF target range. FIG. 4B illustrates an image circle 80 on the imaging surface of the main line CCD 16 when the camera body 10 is in the 16: 9 mode, a video area 82 indicating a pixel range in which an image is effectively captured by the main line CCD 16, and , AF area 84 indicating the target range of AF is shown. As shown in FIGS. 4A and 4B, in the 16: 9 mode, the AF CCD 36 and the main line CCD 16 are the size of the image circles 70 and 80 and the image formed in the image circles 70 and 80. Are substantially matched, and the video areas 72 and 82 are set so as to be substantially inscribed in the image circles 70 and 80, and the sizes (image sizes) of the video areas 72 and 82 are also matched. Accordingly, the positions and sizes of the AF area 74 shown in the video area 72 of the AF CCD 36 and the AF area 84 shown in the video area 82 of the main line CCD 16 also coincide with each other.

  On the other hand, FIG. 5A shows an image circle 70, a video area 72, and an AF area 74 on the imaging surface of the AF CCD 36 as in FIG. 4A, and FIG. An image circle 90, a video area 92, and an AF area 94 on the imaging surface of the main line CCD 16 in the 4: 3 mode are shown. 1 is not inserted on the optical path. As shown in FIGS. 5A and 5B, in the 4: 3 mode, the size of the image circles 70 and 90 and the image formed in the image circles 70 and 90 in the AF CCD 36 and the main line CCD 16 are formed. Is almost the same. On the other hand, the video area 92 of the main line CCD 16 is set to an area with an aspect ratio of 4: 3 excluding a part of the left and right ranges of the video area 82 in the 16: 9 mode indicated by a broken line. That is, the image area 72 of the AF CCD 36 and the image area 92 of the main line CCD 16 do not match. Accordingly, the position and size of the AF area 74 in the image area 72 of the AF CCD 36 do not match the position and size of the AF area 94 in the image area 92 of the main line CCD 16.

  The CPU 42 of the lens device 12 determines the position of the AF area 74 in the image area 72 of the AF CCD 36 shown in FIGS. 4A and 5A based on the AF area information acquired from the AF area operation unit 46. And the size and the size of the AF area 84 in the video area 82 of the main line CCD 16 shown in FIG. 4B or the size and size shown in FIG. The position and size of the AF area 94 in the video area 92 of the main line CCD 16 are obtained.

  Here, the position of the AF area can be defined as the coordinate value of the center position of the AF area in the XY coordinates assumed for the video area, for example. The size of the AF area is represented by a horizontal size and a vertical size. The ratio (%) of the horizontal size of the AF area to the horizontal size of the video area and the ratio (%) of the vertical size of the AF area to the vertical size of the video area. ).

  For example, the image circle 70, 80, 90 on the imaging surface of the AF CCD 36 and the main CCD 16 is 11 mm, and the horizontal size of the video area 72 of the AF CCD 36 and the horizontal area of the video area 82 of the main CCD 16 in the 16: 9 mode is 9. .59 mm and the vertical size is 5.39 mm. In the 4: 3 mode, the horizontal size of the video area 92 of the main line CCD 176 is 7.19 mm and the vertical size is 5.39 mm. The position (center position) of the AF area coincides with the center position of the video area, and the size of the AF area 74 is a square of 1.2 mm in both the horizontal size and the vertical size.

  At this time, the position of the AF area 84 in the video area 72 of the AF CCD 36 and the video area 82 of the main CCD 16 in the 16: 9 mode is the XY coordinate that is also assumed in the video area 72 and the video area 82. Is obtained as the coordinate value (X0, Y0) of the center position. The sizes of the AF area 74 and the AF area 84 are obtained with a horizontal size (ratio of horizontal size) of 12.5% and a vertical size (ratio of vertical size) of 22.3%. Further, the position of the AF area 94 in the video area 92 of the main line CCD 16 in the 4: 3 mode is obtained as the coordinate value (X1, Y1) of the center position in the XY coordinates assumed in the video area 92. . The size of the AF area 94 is obtained with a horizontal size (ratio of horizontal size) of 13.3% and a vertical size (ratio of vertical size) of 22.3%. If the coordinate values of the XY coordinates from (0000h, 0000h) to (FFFFh, FFFFh) are assigned to the video area regardless of the size of the video area, the center position of the AF area becomes the center position of the video area. The coordinate value (X0, Y0) of the center position of the AF area 84 in the video area 82 and the coordinate value (X1, Y1) of the center position of the AF area 94 in the video area 92 in the case where they match each other are ( 8000h, 8000h).

  The CPU 42 transmits information on the position and size of the AF area 74 in the video area 72 obtained with reference to the video area 72 of the AF CCD 36 to the AF signal processing unit 44, so that the AF signal processing unit 44 performs AF. Set the target range.

  Further, the CPU 42 acquires the aspect ratio information from the camera circuit 18 and determines whether the size of the video area of the main line CCD 16 is 16: 9 in the 16: 9 mode or 4: 3 in the 4: 3 mode. Get information about. Then, when the shooting mode of the camera body 10 is set to 16: 9 mode, when information that the aspect ratio is 16: 9 is acquired from the aspect ratio information, the video area 82 in the 16: 9 mode is used as a reference. Information about the position and size of the AF area 84 in the obtained video area 82 is transmitted to the camera circuit 18 as AF area frame information.

  On the other hand, when the shooting mode of the camera body 10 is set to 4: 3 mode and the information that the aspect ratio is 4: 3 is acquired from the aspect ratio information, the image area 92 in the 4: 3 mode is obtained as a reference. Information on the position and size of the AF area 94 in the video area 92 is transmitted to the camera circuit 18 as AF area frame information.

  The camera circuit 18 transmits, as the AF area frame information, from the CPU 42 to the video (image) photographed in the video area 82 in the 16: 9 mode or the video area 92 in the 4: 3 mode of the main line CCD 16. A frame image of the AF area frame corresponding to the position and size of the AF area 84 or the AF area 94 is synthesized, and the synthesized video signal is output to the viewfinder 20. Thereby, as shown in FIGS. 6A and 6B, the AF area frame 56 of a rectangular line is displayed on the screen 20A of the view funder 20 so as to overlap the video. 6A shows the display in the 16: 9 mode, and the image obtained from the 16: 9 image area 82 is displayed on the entire screen 20A (shaded portion) of the viewfinder 20, and FIG. B) is a display in 4: 3 mode, and the video obtained from the 4: 3 video area 92 is displayed in the 4: 3 area (shaded area) excluding the left and right ranges on the screen 20A of the viewfinder 20. Is displayed. Further, the range of the AF area may be displayed by a method other than the AF area frame as shown in FIG.

  Next, the processing procedure of the CPU 42 for displaying the AF area frame will be described with reference to the flowchart of FIG. First, after performing required initial settings (step S10), the CPU 42 executes processing other than AF area setting (step S12). Then, AF area information is received from the AF area operation unit 46 (step S14).

  Subsequently, the CPU 42 determines whether or not there is a change in the AF area information received from the AF area operation unit 46 (step S16). When it determines with NO, it returns to the process of step S12. On the other hand, if YES is determined, the aspect ratio information indicating the aspect ratio of the video area of the main line CCD 16 is read from the camera circuit 18 of the camera body 10 (step S18). Then, the position and size of the AF area given by the AF area information are calculated based on the video area of that aspect ratio (the video area of the main line CCD 16) (step S20).

  Next, it is determined whether or not the AF area range (position and size) obtained in step S20 is within the video area range (step S22). If NO is determined, the AF area is corrected to be within the video area (step S24). If it is determined as YES in step S22, the process of step S24 is not performed.

  Subsequently, AF area frame information indicating the position and size of the AF area based on the video area of the main CCD 16 of the camera body 10 obtained in step S20 or step S24 is transmitted to the camera circuit 18 of the camera body 10 (step S20). S26). Also, the position and size of the AF area in the image area of the AF CCD 36 are obtained (step S28), and the position and size of the AF area are transmitted to the AF signal processing unit 44 (step S30). When the process of step S30 ends, the process returns to step S12, and the process from step S12 is repeated.

  As described above, since the AF area frame is displayed on the viewfinder 20 based on the AF area information indicating the range of the AF area in the video area based on the video area of the main line CCD 16, the video area is displayed. Even if it is changed, the actual range of the AF area can be appropriately displayed.

  Even when the camera body 10 is in the 4: 3 mode and the ratio converter 37 shown in FIG. 1 is inserted on the main optical path, the image magnification is the same on both imaging surfaces of the AF CCD 36 and the main CCD 16 ( Therefore, it is not necessary to display the AF area frame in consideration of whether or not the ratio converter 37 is inserted on the main optical path. That is, the range of the AF area in the video area of the main CCD 16 obtained by the above processing is the actual AF area (that is, the AF area in the video area of the AF CCD 36) by inserting the ratio converter 37 on the main optical path. Therefore, even if the ratio converter 37 is inserted on the main optical path, it is not necessary to obtain the AF area range in the video area of the main CCD 16 by special processing.

  In the above embodiment, the range of the AF area in the video area of the main line CCD 16 is obtained by the CPU 42 of the lens apparatus 12. For example, in the camera circuit 18 of the camera body 10, the video area of the main line CCD 16 is obtained. AF area information that does not take into account the range is acquired from the lens device 12 or the AF area operation unit 46, and the AF area in the video area of each mode depends on whether the camera circuit 18 is in the 16: 9 mode or the 4: 3 mode. The range may be obtained in the same manner as in the above embodiment. Other than the camera circuit 18, for example, the CPU of the AF area operation unit 46 acquires necessary information from the lens device 12 and the camera body 10, and the AF area range in the video area of the main line CCD 16 is the same as in the above embodiment. You may make it ask.

  In the above-described embodiment, the case where the video area of the main line CCD 16 is switched to either the aspect ratio 16: 9 or 4: 3 has been described, but the video area range may be switched in other ranges. The present invention is applicable. Further, the present invention is not limited to the case where the range of the video area is switched by the switchable camera as in the above embodiment, but also when the range of the video area is changed by exchanging the camera body 10 used in the system. Can be applied.

  In the above-described embodiment, a system in which AF is performed using the AF CCD 36 on one imaging surface for acquiring an image for AF has been described. However, the system adopts a so-called optical path length difference type AF. Even if it exists, this invention is applicable. Although detailed description of the optical path length difference type AF is omitted, in the optical path length difference type AF, for example, the subject light reflected by the half mirror 28 in FIG. 1 is further branched and arranged at a position where the optical path length is different. The subject light is imaged on a plurality of imaging surfaces (for example, two imaging surfaces), and the subject is imaged on each of the imaging surfaces. Then, a focus evaluation value is obtained for each video signal obtained from each imaging surface, and the focus state (front pin, rear pin, in-focus) with respect to the imaging surface of the main line CCD is detected from the magnitude relationship, and the detected focus state The focus of the taking lens is adjusted based on the above.

FIG. 1 is a block diagram showing the overall configuration of an autofocus system to which the present invention is applied. FIG. 2 is a diagram showing an external configuration of the AF area operation device (AF area operation unit). FIG. 3 is a diagram illustrating an example of an AF area frame displayed on the viewfinder screen. FIG. 4 is a diagram showing an image circle, a video area, and an AF area in the AF CCD and the main line CCD in the 16: 9 mode. FIG. 5 is a diagram showing an image circle, a video area, and an AF area in the AF CCD and the main line CCD in the 4: 3 mode. FIG. 6 is a diagram illustrating an example of an AF area frame displayed on the viewfinder. FIG. 7 is a flowchart showing a processing procedure in the CPU of the lens apparatus for displaying the AF area frame.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Camera body, 12 ... Lens apparatus, 14 ... Three color separation optical system, 16, 16A-16C ... Main line CCD, 18 ... Camera circuit, 20 ... Viewfinder, 22 ... Focus lens group, 24 ... Zoom lens group, 26 ... Aperture, 28 ... Half mirror, 30 ... Master lens group, 32 ... Master lens group for AF, 34 ... Total reflection mirror, 36 ... CCD for AF, 37 ... Ratio converter, 38 ... Motor, 40 ... Driver, 42 ... CPU 44... AF signal processing section 46... AF area operation section 56... AF area frame

Claims (7)

The range of the video area indicating the pixel range for effectively acquiring an image on the imaging surface of the imaging means can be changed to a different aspect ratio, and is acquired from the AF area range indicating the autofocus target range of the video area. An autofocus system that automatically focuses the photographic lens based on the image
An AF area range calculation means for calculating the range of the AF area in the video area based on the range of the video area;
Display means for displaying the range of the AF area together with the image acquired by the range of the video area based on the range of the AF area calculated by the AF area range calculation unit;
An autofocus system characterized by comprising   2. The autofocus system is constructed by a camera body including the imaging unit, a lens device including the photographing lens, and a monitor that displays an image displayed by the display unit. Autofocus system.   2. The autofocus system according to claim 1, wherein the display means displays the range of the AF area by an AF area frame surrounding the range.   2. The autofocus system according to claim 1, wherein the range of the video area can be changed to a range having an aspect ratio of 16: 9 and a range having an aspect ratio of 4: 3.   2. The autofocus system according to claim 1, further comprising AF area changing means for changing the range of the AF area to a desired range.   An operating means for specifying an AF area range; and an AF area changing means for changing the AF area range to an AF area range specified by the operating means, wherein the operating means is connected to the lens device. The autofocus system according to claim 2, wherein the autofocus system is an accessory device. 2. The autofocus system according to claim 1, further comprising an AF imaging means for acquiring an image in the range of the AF area separately from the imaging means.

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