JP2005227608A - Auto-focus system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an auto-focus system appropriately changing an AF area by changing an AF range to the AF area also in another system when auto-focusing (AF) with a combination of a contrast system and another system such as an active type triangular range finding system is realized, and when the AF area for the AF range is changed in the contrast system. <P>SOLUTION: When a range of the AF area (position or the like) is assigned by an AF area operation part 14, a CPU assigns the AF area of an AF signal processing part 46 for detecting a contrast of a pickup image, and obtains the contrast (focal point evaluation value) of the image (object) in the AF area. On the other hand, the CPU changes the position of a range finding module by motors 56, 58 in the plane perpendicular to the optical axis in the triangular range finding system and obtains the range value by using the object in the above AF area as a range finding object. Then, auto-focusing is carried out based on the the focal point evaluation value and the range value. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an autofocus system, and more particularly, to an autofocus system that performs automatic focus adjustment by combining a contrast AF and another AF.

  Autofocus (AF) employed in video cameras such as TV cameras detects the contrast of a captured image based on a video signal obtained by an image sensor, and controls the focus so that the contrast becomes maximum (maximum). A contrast method is common. The contrast of the captured image is quantitatively detected by, for example, an integrated value obtained by extracting a high frequency component from a video signal obtained by the image sensor and integrating the high frequency component signal for each field. The integrated value indicates the level of the contrast of the photographed image and the degree of focusing, and is referred to as a focus evaluation value in this specification.

  Also. In many cases, the target to be focused by AF (target of AF) is limited to a subject within a part of the shooting range (on the screen). In contrast-based AF, a part of the video signal of each field is included. By detecting the focus evaluation value from the limited range of video signals, the AF target range (hereinafter referred to as the AF area) is limited to a partial range on the screen. The AF area may be fixed at a predetermined position on the screen, for example, at the center of the screen, but the photographer can change it to a desired position according to the position change of the main subject on the screen. The ones made are also known.

  On the other hand, in addition to the contrast method, an active triangular distance measuring method, a double image matching method, and the like are generally known as AF methods employed in cameras.

By the way, contrast AF is not performed properly under conditions where it is difficult to detect the peak focus evaluation value even if the focus position is changed, such as when the subject is dark or when the contrast of the subject is originally low. There is a case. Therefore, it is conceivable to perform AF by combining the contrast method and another method. According to this, even under a condition in which focusing is difficult with contrast AF, it is possible to accurately perform focusing with another AF. For example, Patent Documents 1 and 2 describe a combination of active and passive AFs.
JP 10-48509 A Japanese Patent Laid-Open No. 10-2221065

  However, when the contrast type AF and another type of AF are combined in this way, there is no one that can change the AF area range, and when the AF area range can be arbitrarily changed, Although it is necessary to change each AF area so that the range of the AF area in each method matches, conventionally, such a method has not been proposed.

  The present invention has been made in view of such circumstances, and enables the AF area range to be changed in ranging AF, and AF is performed by combining contrast AF and AF of another method (ranging method). An object of the present invention is to provide an autofocus system that can appropriately change the range of an AF area when it is performed.

  In order to achieve the object, the autofocus system according to claim 1 measures a distance to a subject in an AF area which is an AF target range among all shooting ranges shot through the shooting lens. An autofocus system comprising: a distance measuring unit; and an AF control unit that executes autofocus control based on a distance value detected by the distance measuring unit and automatically focuses on the subject. An AF optical path branched for autofocus from the optical path of the photographing lens, a distance measuring module disposed in the AF optical path and provided with an optical element of the distance measuring means, and the distance measuring module for the AF A driving means for moving in a plane perpendicular to the optical axis of the optical path; an AF area designating means for designating a range of the AF area; And a control means for controlling the position of the distance measuring module so that the subject to be measured by the distance measuring means is the subject in the AF area designated by the AF area designating means. It is characterized by.

  According to the present invention, it is possible to change the distance measurement target in the distance measurement AF to an arbitrary subject within the shooting range.

  According to a second aspect of the present invention, there is provided the autofocus system according to the first aspect of the present invention, further comprising a contrast detection unit that detects a contrast of a subject in the AF area in the entire photographing range photographed through the photographing lens. The AF control means executes autofocus control based on the contrast evaluation value detected by the focus evaluation value detection means and / or the distance measurement value detected by the distance measurement means, and automatically controls the subject. The focus is on the focus.

  According to the present invention, even in a situation where focusing cannot be performed accurately by contrast-type autofocus (AF) using a contrast detection means, the distance measurement AF using distance measurement means is used accurately. You can now focus. In addition, since the AF area as the AF target range in the contrast AF is changed, the distance measurement object in the ranging AF is also changed to the subject in the AF area. Therefore, the contrast AF and the ranging AF The AF area can be changed even when AF is performed in combination.

  According to a third aspect of the present invention, there is provided the autofocus system according to the second aspect of the invention, wherein the contrast detecting means detects the contrast of the subject by imaging the subject with the subject light guided to the AF optical path. It is characterized by. That is, by using a common AF optical path for the contrast detecting means and the distance measuring means, the AF optical path can be used effectively and the configuration of the photographing lens can be simplified.

  According to a fourth aspect of the present invention, in the invention of the first or second aspect, the distance measuring method of the distance measuring means is a triangular distance measuring method, and the optical element of the distance measuring module is a distance measuring device. A light emitting element for emitting light and a light receiving element for receiving distance measuring light are characterized.

  According to a fifth aspect of the present invention, in the invention according to the first or second aspect, the distance measuring method of the distance measuring means is a double image matching method, and the optical element of the distance measuring module is a subject. It is characterized by being a light-receiving element that receives subject light from.

  According to the autofocus system of the present invention, the AF area range can be appropriately changed even when AF is performed by combining contrast AF and other AF methods.

  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 autofocus system shown in the figure is a system applied to, for example, a broadcast television camera, and includes a lens device 10, a camera body 12, an AF area operation unit 14, a viewfinder 16, and the like.

  The camera body 12 includes a three-color separation optical system 18 and CCDs 20A, 20B, 20C, and the like, and subject light that has passed through a photographing optical system (to be described later) of the lens apparatus 10 is R (red), The light is decomposed into wavelength components of G (green) and B (blue) and imaged on the imaging surfaces (light receiving surfaces) of the CCDs 20A to 20C arranged for R, G, and B, respectively. The R, G, and B image signals photoelectrically converted by the CCDs 20A to 20C are subjected to necessary processing by a processing circuit (not shown) and then formed into a video signal of a predetermined format (for example, NTSC system).

  The lens device 10 includes a photographing optical system (photographing lens) and a control system. The photographic lens is provided with a main optical path (photographing optical path) and a sub optical path (AF optical path), and the photographic optical path is used for focus adjustment along the optical axis O in the same manner as a known photographic lens. A focus lens (group) 22 that moves in the optical axis direction, a zoom lens (group) 24 that moves in the optical axis direction for zoom adjustment (focal length adjustment), an iris 26 that opens and closes to adjust the light amount, and finally A master lens (group) 28 and the like for arranging an image are arranged. A half mirror 30 is disposed in front of the master lens 28, and the AF optical path is branched from the photographing optical path by the half mirror 30.

  In the AF optical path, an AF master lens (group) 32 for forming an image is disposed along the optical axis O ′ in the same manner as the master lens 28, and a total reflection mirror 34, a prism 36, an AF CCD 40, A ranging module 42 is arranged.

  According to this photographic lens, the subject light incident on the photographic lens passes through the focus lens 22, the zoom lens 24, and the diaphragm 26 in the photographic optical path, enters the half mirror 30, and the subject light transmitted through the half mirror 30. The light is branched into subject light reflected by the half mirror 30.

  The subject light that passes through the half mirror 30 and travels along the photographing optical path passes through the master lens 28 of the photographing optical path and enters the three-color separation optical system 18 of the camera body 12. Then, as described above, the three-color separation optical system 18 separates the R, G, and B wavelength components, and forms subject images on the imaging surfaces of the R, G, and B CCDs 20A to 20C, respectively.

  On the other hand, the subject light reflected on the half mirror 30 and traveling on the AF optical path passes through the AF master lens 32 on the AF optical path, and then reflects on the total reflection mirror 34 and enters the prism 36. The prism 36 includes a first prism 36A and a second prism 36B, and a joint surface between the first prism 36A and the second prism 36B serves as a reflective surface 38 that reflects light having a wavelength in the visible light region. Yes. The subject light incident on the prism 36 is reflected by the reflecting surface 38 and enters the imaging surface of the AF CCD 40, and the subject image is formed on the imaging surface of the AF CCD 40 by the action of the AF master lens 32. Note that the shooting conditions for the imaging surface of the AF CCD 40 such as the distance of the subject focused on the imaging surface of the AF CCD 40 and the shooting range are the same as those for the imaging surfaces of the CCDs 20A to 20C of the camera body 12. The images captured by the AF CCD 40 correspond to images captured by the CCDs 20A to 20C of the camera body 12. Further, the reflecting surface 38 of the prism 36 is not limited to the characteristic of reflecting the entire visible light region, but may be a property of reflecting only a wavelength of a specific color (for example, green) in the visible light region.

  On the other hand, the distance measuring module 42 is a module for performing distance measurement by an active triangular distance measuring method, and includes an optical unit (details will be described later) including a light projecting unit and a light receiving unit. For example, an infrared LED is installed as a light emitting element in the light projecting portion of the optical unit, and infrared light emitted by the infrared LED is emitted from the light projecting portion as distance measuring light. . The reflecting surface 38 of the prism 36 has a characteristic of transmitting light having a wavelength in the infrared light region, and the distance measuring light emitted from the light projecting unit is transmitted through the reflecting surface 38 of the prism 36 and then totally reflected. The light is reflected by the mirror 34, passes through the AF master lens 32, and enters the half mirror 30 in the photographing optical path. The half mirror 30 has a characteristic of totally reflecting light having a wavelength in the infrared light region. The distance measuring light incident on the half mirror 30 is totally reflected by the half mirror 30, and then the iris 26 in the photographing optical path. The light passes through the zoom lens 24, the focus lens 22 and the like in order, and is projected from the front surface of the photographing lens toward the subject.

  The distance measuring light reflected from the subject and returned to the photographing lens is reflected by the half mirror 30 after passing through the focus lens 22, the zoom lens 24, and the iris 26 in the photographing optical path in the same manner as the subject light. Guided to the optical path. Then, after passing through the AF master lens 32 and reflected by the total reflection mirror 34, it passes through the prism 36 and enters the light receiving portion of the optical unit of the distance measuring module 42.

  Next, the control system of the lens device 10 will be described. The lens device 10 includes a CPU 44, a contrast AF signal processing unit 46 (hereinafter referred to as an AF signal processing unit 46), and a distance measuring circuit as a control system for executing AF. 48, drivers 50 and 52, motors 54, 56, and 58 are mounted.

  The AF signal processing unit 46 is provided with captured images sequentially captured by the AF CCD 40 as video signals (luminance signals) from the AF CCD 40. The video signal supplied from the AF CCD 40 is, for example, based on an interlace method, and a captured image that is sequentially captured by the AF CCD 40 is provided for each period (one field) of the vertical synchronization signal of the video signal. .

  The AF signal processing unit 46 detects the contrast (high or low) of the captured images sequentially captured based on the video signal given from the AF CCD 40. A method for detecting contrast is well known. For example, a high frequency component of a video signal is extracted by a filter process (high pass filter process), and the high frequency component is integrated for each field. The integrated value is a focus evaluation value indicating the level of contrast of the photographed image. Thus, by obtaining the focus evaluation value for each field, the contrast of the photographed image sequentially captured by the AF CCD 40 is detected. . The contrast of the captured image of the AF CCD 40 detected in this way indicates the contrast of the captured images of the CCDs 20A to 20C of the camera body 12.

  Further, when the AF signal processing unit 46 detects the contrast of the photographed image, the CPU 44 designates a range to be integrated in order to obtain a focus evaluation value in the video signal of each field (high frequency component of the video signal). The range (position and size) of the AF area is limited. Thus, a focus evaluation value indicating the contrast of the image (subject) in the AF area is obtained. Here, the AF area indicates a range of a subject to be focused by AF, that is, an AF target range, and is set to, for example, a rectangular range within the photographing range. Details regarding the setting of the AF area will be described later.

  The focus evaluation value detected by the AF signal processing unit 46 in this way is given to the CPU 44 by an instruction from the CPU 44.

  The distance measurement circuit 48 is supplied with a detection signal output from the light receiving unit of the distance measurement module 42. The light receiving unit is provided with an optical position detecting element that receives the distance measuring light that is projected from the light projecting unit, reflected by the subject and returned, and detects the received position. The optical position detection element outputs a detection signal indicating the position where the distance measuring light is received.

  The distance measuring circuit 48 performs distance measurement in accordance with an instruction from the CPU 44. When distance measurement is performed, the light emitting unit of the distance measuring module 42 emits light, and the detection signal, that is, distance measuring light is received from the light receiving unit. A detection signal indicating the received position is acquired. Then, based on the detection signal, a distance measurement value indicating the distance to the subject on which the distance measurement light is projected (reflected) is obtained by the principle of triangulation. The distance measurement value thus obtained is given to the CPU 44.

  The CPU 44 sends a control signal to the driver 50 of the motor 54 connected to the focus lens 22 based on the focus evaluation value acquired from the AF signal processing unit 46 and the distance measurement value acquired from the distance measuring circuit 48 as described above. And the motor 54 is controlled to move the focus lens 22 to a focus position (focus position).

  Here, the AF method for setting the focus lens 22 to the in-focus position based on the focus evaluation value acquired from the AF signal processing unit 46 is a contrast method as is well known, and the focus lens 22 is moved to the in-focus position by this method. For example, a mountain climbing method is used. Although details are omitted, for example, the focus evaluation value is appropriately acquired from the AF signal processing unit 46 while the focus lens 22 is moved, and the direction in which the focus evaluation value increases is detected from the acquired focus evaluation values at a plurality of points. . Then, the focus lens 22 is moved in that direction. If the direction in which the focus evaluation value increases is not detected, that is, the focus state that is the peak of the focus evaluation value is detected, the focus lens 22 is stopped at that position. As a result, the focus lens 22 is set to the in-focus position, and the image captured by the CCDs 20A to 20C of the camera body 12 is focused on the subject in the AF area.

  On the other hand, the AF method for setting the focus lens 22 to the in-focus position based on the distance value acquired from the distance measuring circuit 48 is an active triangular distance measuring method (hereinafter simply referred to as a triangular distance measuring method) as is well known. Yes, when the focus lens 22 is moved to the in-focus position by this method, for example, the relationship between the distance of the subject to be focused and the position of the focus lens (in-focus position) at that time is stored in advance. The focus lens 22 is moved to the in-focus position corresponding to the distance value acquired from the distance measuring circuit 48 with reference to the received data. As a result, the focus lens 22 is set to the in-focus position, and the video imaged by the CCDs 20A to 20C of the camera body 12 is focused on the subject whose distance has been measured. As will be described later, the subject to be measured by the distance measuring module 42 or the distance measuring circuit 48 is the subject in the same AF area as the contrast type AF. The subject is in focus.

  The CPU 44 realizes accurate focusing regardless of the subject condition by performing AF combining the contrast method and the triangulation method based on the focus evaluation value and the distance measurement value. Is not particularly limited in the present invention. For example, when the focus AF obtained from the AF signal processor 46 is smaller than a predetermined value when the contrast AF is a standard AF and the subject is dark or the contrast of the subject is originally low, the contrast AF is used. Then, it is determined that it is difficult to detect the in-focus position, and only in such a case, an active triangulation AF is executed.

  Further, assuming that the focus lens 22 is deviated from the in-focus position, it is possible to perform a combination method in which rough focusing is first performed by a triangulation method and then high-precision AF is performed by contrast AF. .

  Furthermore, the AF method may be switched by a method in which a user selects a contrast AF and a triangulation AF, and the AF is performed by the method selected by the switch.

  Next, setting of the AF area will be described. As shown in FIG. 1, an AF area operation unit 14 is connected to the lens apparatus 10, and AF area information for designating an AF area range (position, size, etc.) within a shooting range (within a shot image screen) is displayed. The data is transmitted from the AF area operation unit 14 to the CPU 44.

  The AF area operation unit 14 is provided with an X switch 60 for moving the range (position) of the AF area in the horizontal direction (X direction) on the screen and a Y switch 62 for moving the AF area in the vertical direction. By operating the switches 60 and 62 by the operator, the range of the AF area designated for the CPU 44 can be changed to desired vertical and horizontal positions on the screen. Although the size and shape of the AF area can be changed, in this embodiment, the size of the AF area is fixed to a predetermined size, and the shape of the AF area is fixed to a rectangular shape. And Also, information on the position and size of the AF area is transmitted to the CPU 44 as AF area information indicating the range of the AF area, and the shape of the AF area is set to a rectangular shape even if not specified.

  The range of the AF area designated by the AF area operation unit 14 is also given to the camera body 12 and designated by the AF area operation unit 14 for the video signals obtained from the CCDs 20A to 20C of the camera body 12. An image of the AF area frame indicating the range (contour) of the AF area is synthesized, and the synthesized signal is output to the viewfinder 16 installed in the camera body 12 or the like. As a result, the range of the AF area (AF area frame) is displayed on the screen of the viewfinder 16 together with the real-time video imaged by the CCDs 20A to 20C of the camera body 12. Therefore, the operator can operate the AF area operation unit 14 so that the subject to be focused is within the AF area frame while viewing the viewfinder image. In FIG. 1, the flow of information related to the display of the AF area is simplified.

  The CPU 44 receives the AF area information from the AF area operation unit 14 and determines the range of the AF area according to the AF area information. Then, the AF area range is designated to the AF signal processing unit 46 as described above, and a focus evaluation value obtained from the video signal in the AF area range is acquired from the AF signal processing unit 46. As a result, the subject to be focused by contrast AF is set to the subject in the AF area designated by the AF area operation unit 14.

  Further, the CPU 44 outputs a control signal to the drivers 52 of motors (linear motion motors) 56 and 58 for moving the distance measuring module 42 in the X direction (horizontal direction) and the Y direction (vertical direction). The linear motion motors 56 and 58 are controlled to move the distance measuring module 42 to a position corresponding to the range of the AF area determined according to the AF area information from the AF area operation unit 14. As a result, the subject to be focused by the triangulation AF is set to the subject in the AF area designated by the AF area operation unit 14.

  Here, the configuration of the ranging module 42 and the linear motion motors 56 and 58 and the schematic configuration of the optical path of the photographing lens up to the ranging module 42 are shown in the perspective view of FIG. As shown in the drawing, in the optical path to the distance measuring module 42, each lens 64 schematically showing a focus lens 22, a zoom lens 24, etc. (see FIG. 1) disposed from the front surface of the photographing lens to the half mirror 30. The half mirror 30, the AF master lens 32 in the AF optical path, the total reflection mirror 34, the prism 36, and the like are disposed. The distance measuring module 42 is disposed on the rear stage side of the prism 36.

  The distance measuring module 42 includes an optical unit 70 and a substrate 72. The optical unit 70 whose side surface is covered with a case 72A includes the light projecting unit 74 and the light receiving unit 76 each having a lens on the front surface. Adjacent to each other in the horizontal direction. As described above, the ranging light having the wavelength in the infrared region emitted from the light projecting unit 74 is transmitted through the reflection surface 38 of the prism 36, and then the total reflection mirror 34, the AF master lens 32, the half mirror 30, and the photographing. Light is projected from the front surface of the photographing lens toward the subject via each lens 64 in the optical path for use. Then, the distance measuring light reflected and returned by the subject enters the light receiving unit 76 following the same optical path in reverse. Note that the subject light in the visible light region incident on the photographing lens is reflected by the reflecting surface 38 of the prism 36 and enters the AF CCD 40.

  On the other hand, on the substrate 72 of the distance measuring module 42, the optical unit 70 is fixedly provided on the front surface, and connecting portions 72A and 72B having through holes in the lower portion and the side portion are projected. Guide rods 86 and 96, which will be described later, are inserted through the through holes of the connecting portions 72A and 72B, and the substrate 72 is supported by the guide rods 86 and 96. The distance measuring circuit 48 shown in FIG. 1 may be arranged on the substrate 72.

  Each of the linear motion motors 56 and 58 is, for example, a voice coil motor, and yokes 80 and 90 fixed to a predetermined position such as a lens barrel of the photographing lens, and a movable portion 84 on which the voice coils 82 and 92 are fixed. 94. The movable portions 84 and 94 are formed in a U shape, and the guide rods 86 and 96 are supported by protruding portions at both ends. As described above, the guide rods 86 and 96 are inserted into the through holes of the connecting portions 72 and 74 protruding from the substrate 72. When a current in a predetermined direction is supplied to the voice coils 82 and 92 of the linear motion motors 56 and 58, the movable portions 84 and 94 are linearly driven by the action of the magnetic field generated in the yokes 80 and 90 and the current of the voice coils 82 and 92. The guide rods 86 and 96 are moved in a direction perpendicular to the axial direction thereof.

  Accordingly, when a current in a predetermined direction is supplied to the voice coil 82 of the linear motor 56 and the movable portion 84 of the linear motor 56 is linearly driven, the distance measuring module 42 is guided to the guide rod 96 of the linear motor 58 by the driving force. Then, when the movable portion 94 of the linear motion motor 56 is linearly driven by passing a current in a predetermined direction through the voice coil 92 of the linear motion motor 58 and moving in the X direction, the distance measuring module 42 is driven by the driving force. It is guided by the guide rod 86 and moves in the Y direction. As a result, the distance measuring module 42 is displaced, and the light projecting unit 74 and the light receiving unit 76 of the optical unit 70 are displaced in the XY plane perpendicular to the optical axis O ′ of the photographing lens. Then, the position within the photographing range where the distance measuring light emitted from the light projecting unit 74 is projected changes.

  The distance measuring module 42 is displaced by the linear motion motors 56 and 58 in this way, and the positions of the light projecting unit 74 and the light receiving unit 76 are the AF area range (position) designated by the AF area operation unit 14 as described above. Accordingly, the distance measuring light from the light projecting unit 74 can be projected onto the subject in the AF area, and the object of the triangulation AF can be set as the subject in the AF area. it can.

  Next, the processing procedure for setting the AF area in the CPU 44 will be described with reference to the flowchart of FIG. After the power is turned on, the CPU 44 performs necessary initial settings (step S10), and then repeatedly executes the following steps S12 to S20. First, processing other than AF area setting is executed (step S12). Subsequently, AF area information, that is, information on the position and size of the AF area that determines the range of the AF area is received from the AF area operation unit 14 (step S14). Then, it is determined whether or not the range of the AF area designated by the AF area information has changed with respect to the range of the AF area set at the present time (the range of the AF area designated last time) (step S16). . If NO is determined, the process returns to step S12 without performing steps S18 and S20 for changing the AF area.

  On the other hand, if YES is determined in step S <b> 16, the AF area range (position and size) is changed to a newly designated range from the AF area operation unit 14, and the changed new signal is sent to the AF signal processing unit 46. A range (position and size) of the AF area is designated (step S18). Subsequently, the linear motion motors 56 and 58 are controlled to change the position of the distance measuring module 42 (the positions of the light projecting unit 74 and the light receiving unit 76) to a position corresponding to the new AF area range (position) (step). S20).

  By repeating the processing from step S12 to step S20, the contrast AF and the triangulation AF target are set by the AF area operation unit 14 and set or changed to the subject in the AF area. .

  In the above embodiment, an autofocus system that performs automatic focus adjustment by combining contrast AF and active triangular ranging AF has been described. However, AF ranging combined with contrast AF is available. The present invention can be applied to an active type or passive type ranging method other than the active type triangulation method. In the case of applying the active distance measuring method, generally, it has a light projecting unit and a light receiving unit as in the triangular distance measuring method of the above embodiment, and the light projecting unit and the light receiving unit are shown in FIGS. The distance measurement module is installed in a distance measurement module similar to the distance measurement module 42 for the triangular distance measurement method, and the distance measurement module is in the X direction (horizontal direction) perpendicular to the optical axis as shown in FIGS. ) And Y direction (vertical direction).

  On the other hand, when the passive distance measuring method is applied, the light receiving unit generally has only a light receiving part, and the light receiving part is the same as the distance measuring module 42 for the triangular distance measuring method shown in FIGS. The distance measuring module is installed in a module and is movable in the X direction (horizontal direction) and the Y direction (vertical direction) perpendicular to the optical axis in the same manner as shown in FIGS. In the case of the passive method, it is general that subject light having a wavelength in the visible light region is received by the light receiving unit. In this case, for example, the reflecting surface 38 of the prism 36 shown in FIGS. The object light incident on the AF CCD 40 may be branched to the light receiving unit of the distance measuring module with the half mirror surface as a half mirror surface. A double image matching method is well known as a passive distance measuring method, but in the double image matching method, two light receiving portions each including a light receiving element array are arranged in a distance measuring module in the horizontal direction, for example.

  In the above-described embodiment, the video signal for detecting the contrast of the captured image is acquired from the AF CCD 40 provided for the AF in the contrast AF, but without using the AF CCD 40, A video signal obtained by the CCDs 20 </ b> A to 20 </ b> C of the camera body 12 may be acquired, and the contrast of the captured image may be detected from the video signal.

  The present invention can be applied not only to a television camera but also to a camera that uses contrast-type autofocus.

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 perspective view showing the configuration of the ranging module and the linear motion motor and the schematic configuration of the optical path of the photographic lens up to the ranging module. FIG. 3 is a flowchart showing the processing procedure for setting the AF area in the CPU.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Lens apparatus, 12 ... Camera body, 14 ... AF area operation part, 16 ... Viewfinder, 18 ... Three color separation optical system, 20A-20C ... CCD, 22 ... Focus lens, 24 ... Zoom lens, 26 ... Iris, 28 ... Master lens, 30 ... Half mirror, 32 ... AF master lens, 34 ... Total reflection mirror, 36 ... Prism, 38 ... Reflecting surface, 40 ... AF CCD, 42 ... Distance measuring module, 44 ... CPU, 46 ... Contrast AF signal processing unit (AF signal processing unit), 48: ranging circuit, 50, 52 ... driver, 54, 56, 58 ... motor, 60 ... X switch, 62 ... Y switch, 70 ... optical unit, 72 ... substrate, 72A, 72B ... connecting part, 74 ... light projecting part, 76 ... light receiving part, 80, 90 ... yoke, 82, 92 ... voice coil, 84, 94 ... movable part, 6,96 ... guide rod

Claims (5)

A distance measuring unit that measures a distance to a subject in an AF area that is a target range of AF out of the entire imaging range captured through the imaging lens, and a distance measurement value detected by the distance measuring unit. An autofocus system including an AF control unit that executes autofocus control and automatically focuses on the subject,
An AF optical path branched for autofocus from the optical path of the photographing lens;
A distance measuring module disposed in the AF optical path and provided with an optical element of the distance measuring means;
Driving means for moving the distance measuring module in a plane perpendicular to the optical axis of the AF optical path;
AF area designating means for designating the range of the AF area;
The distance measuring module is moved by the driving means, and the position of the distance measuring module is controlled so that the subject to be measured by the distance measuring means becomes the subject in the AF area specified by the AF area specifying means. Control means;
An autofocus system characterized by comprising   Contrast detection means for detecting the contrast of the subject in the AF area out of the entire photographing range photographed via the photographing lens is provided, and the AF control means evaluates the contrast detected by the focus evaluation value detection means. 2. The autofocus system according to claim 1, wherein autofocus control is executed based on the value and / or the distance value detected by the distance measuring means, and the subject is automatically focused.   3. The autofocus system according to claim 2, wherein the contrast detection means detects the contrast of the subject by imaging the subject with the subject light guided to the AF optical path.   The distance measuring method of the distance measuring means is a triangular distance measuring method, and the optical elements of the distance measuring module are a light emitting element that emits distance measuring light and a light receiving element that receives the distance measuring light. The autofocus system according to claim 1 or 2. The distance measuring method of the distance measuring means is a double image matching method, and the optical element of the distance measuring module is a light receiving element that receives subject light from a subject. Autofocus system.

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