Abstract:
An auto-focus system comprising an AF area indicating device for indicating a range of an AF area in the shooting screen, an AF area changing device for changing a range of an AF area to be set in the focus controlling device to a range of an AF area indicated by the AF area indicating device, and a switching device for switching a change of a range of an AF area by the AF area changing device between possible and impossible, wherein the change at least relates to the location of an AF area, and wherein the switching device switches a change of a range of an AF area to impossible when the view finder controlling device has no function of displaying the AF area information on the view finder.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an auto-focus system, and more specifically, to an auto-focus system in which a range of an AF area to be set as auto-focus coverage can be changed within a shooting screen. 
     2. Related Art 
     As an auto-focus (AF) adopted for a video camera such as a broadcasting TV camera, Contrast type AF is known. The Contrast type AF obtains an image of an object imaged through a picture-taking lens by an image pickup device and controls a focus of the picture-taking lens to maximize a contrast of the image of the object. 
     The Contrast type AF does not make the entire shooting screen (a shot area) AF coverage. The Contrast type AF usually makes a part, for example a rectangle area, of shooting screen (an AF area) AF coverage. The Contrast type AF in which a range of an AF area within a shooting screen (e.g., the location) can be changed and a desired object in the shot area can be focused by AF has also been known (for example, see Japanese Patent Application Laid Open No. 10-173980). 
     A video camera has a display (monitor) generally called “view finder”, which displays, for example, an image currently taken by the camera in real time so that an operator such as a cameraperson can check a composition of the image. The view finder is also used as a monitor for displaying various types of information such as information of camera setting or lens setting in addition to the currently taken picture. A view finder in which an AF frame indicating a range of the abovementioned AF area is superimposed on the taken picture is also known. 
     A video camera whose view finder displays an AF area and a video camera which adopts a line of vision AF mode in which the location of an AF area is changed by the cameraperson&#39;s line of vision are disclosed in Japanese Patent Application Laid Open No. 7-283993. With this technique, an indication of the location of the AF area is changed on the view finder in response to a change of the location of the AF area. In Japanese Patent Application Laid Open No. 7-283993, a mode in which the location of the AF area is not changed (central emphasis AF mode) can also be selected as well as the line of vision mode. In such a central emphasis mode, an AF area is not indicated so as to avoid complicating a screen of the view finder. 
     SUMMARY OF THE INVENTION 
     In a shooting system in which a lens device with a picture-taking lens is detachable to a camera (camera head) like a TV camera, the camera usually collects information required for displaying various types of information on a view finder, generates picture signals with various types of information superimposed on the taken picture in a circuit in the camera and outputs them to the view finder. When an auto-focus system in which a range of an AF area can be changed as mentioned above is incorporated in such a shooting system, the system may be build as below, for example. A main circuit for performing AF processing is mounted on a lens device and signals of an image of an object required for the Contrast type AF (picture signals for AF) is provided from a camera to the lens device. An operating device on which an operator indicates a range of an AF area is connected to the lens device. The operator&#39;s manipulation is received via the operating device and information indicating the range of the AF area based on the received manipulation is sent from the operating device to the lens device. 
     In order to display AF area information relating to a range of an AF area, such as an AF frame, on a view finder in such a shooting system incorporating an auto-focus system, a camera needs to obtain a range of an AF area designated through the abovementioned operating device from a lens device or an operating device, superimpose AF area information corresponding to the range of the AF area on the taken picture and displays it on the view finder. 
     However, some conventional cameras have a function of displaying AF area information on a view finder but the other conventional cameras do not. Although a camera without a function of displaying AF area information may display a fixed rectangle frame similar to an AF frame at a center of the view finder screen, the fixed rectangle frame does not match the actual AF area. 
     Thus, a camera forming a shooting system may not have a function of displaying AF area information. In such a case, when an operator changes a range of an AF area by manipulating an operating device, the operator cannot check the range of the AF area on the view finder and hard to designate a desired range as an AF area. Once an AF area is changed from a preset range, it is also difficult to infer the range the AF area is set on the shooting screen. 
     The present invention is adapted in view of the abovementioned circumstance, and intends to provide an auto-focus system in which a problem due to a change of a range of an AF area can be avoided where a range of an AF area can be changed and the system has no function of displaying AF area information on a view finder. 
     In order to achieve the abovementioned object, an auto-focus system according to the first aspect of the present invention is an auto-focus system including a focus controlling device for setting an AF area in a shooting screen of a camera and controlling a focus of a picture-taking lens to focus on an object in the AF area, and an AF area display information outputting device for outputting AF area display information for displaying AF area information relating to a range of the AF area on a view finder displaying an image taken by the camera to a view finder controlling device for controlling a display of the view finder, further including an AF area indicating device for indicating a range of an AF area in the shooting screen, an AF area changing device for changing a range of an AF area to be set in the focus controlling device to a range of an AF area indicated by the AF area indicating device, and a switching device for switching a change of a range of an AF area by the AF area changing device between possible and impossible, wherein the change at least relates to the location of an AF area, and wherein the switching device switches a change of a range of an AF area to impossible when the view finder controlling device has no function of displaying the AF area information on the view finder. 
     According to the first aspect, a change of a range of an AF area can be switched to possible or impossible according to whether or not AF area information such as an AF frame is displayed on a view finder. For example, if a range (particularly the location) of an AF area is changed when AF area information is not displayed on a view finder, the AF area cannot be set in a desired range, and if a range of an AF area is changed, where the range is set cannot be inferred. In such a case, a change of a range of an AF area is preferably made impossible. As a change of an AF area automatically becomes impossible when AF area information is not displayed on the view finder, operator&#39;s tasks to determine and select whether to make a change of an AF area impossible can be saved. 
     An auto-focus system according to the second aspect of the present invention is the first aspect wherein when the view finder controlling device does not receive AF area display information from the AF area display information outputting device, the switching device determines that the view finder controlling device has no function of displaying the AF area information on the view finder. For example, if the view finder controlling device has no function of displaying AF area information on the view finder, the view finder controlling device does not require AF area display information nor receive AF area information, which can be a base of determination whether or not the view finder controlling device has the function. 
     An auto-focus system according to the third aspect of the present invention is that when the switching device makes a change of a range of an AF area impossible, at least the location of an AF area set by the focus controlling device is fixed to a predetermined location. When a change of a range of an AF area is made impossible, the range of the AF area can be easily inferred even if AF area information is not displayed on a view finder by previously fixing at least the location of an AF area on the fixed location. 
     According to the auto-focus system of the present invention, a problem due to a change of a range (mainly the location) of an AF area can be avoided when the system has no function of displaying AF area information on a view finder. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing a configuration of a shooting system applying an auto-focus system according to the present invention; 
         FIG. 2  is a diagram showing an AF frame on a screen of a view finder; and 
         FIG. 3  is a flowchart showing a procedure in a CPU of a lens device. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A preferred embodiment of an auto-focus system according to the present invention will be described in detail with reference to the attached drawings. 
       FIG. 1  is a block diagram showing a configuration of a shooting system applying an auto-focus system according to the present invention. The shooting system in the figure is a system used for, for example, a broadcasting TV camera, including a camera  10  (camera head), a lens device  12  having picture-taking lenses (optical system) attached to the camera  10  via a mount and a controlling system for controlling the picture-taking lenses, and a view finder  14 . The picture-taking lenses and the controlling system of the lens device  12  can form a single device or a part or an entire of the controlling system can form a device independent from the picture-taking lenses. 
     As the picture-taking lenses of the lens device  12 , focus lens(es) FL, zoom lens(es) ZL, iris (I), relay lens(es) RL and the like are placed along an optical axis O. The focus lens FL and zoom lens ZL are movable along the optical axis. A focus location (distance to the object) changes according to movement of the focus lens FL. Image magnification (binocular vision) changes according to movement of the zoom lens ZL. The iris I opens and closes and brightness of the image changes according to how much the iris I opens or closes. 
     On the camera  10 , a color separation optical system  16  for separating an object light incoming through the picture-taking lens into waves of three colors of red (R), green (G) and blue (B), and an image pickup device for each of R, G and B for taking a picture of the object light of each color after color separation (e.g., CCD) are placed. The picture-taking devices for R, G and B placed on the location on the light path at the optically equal distances are represented as a single picture-taking device  18  as shown in the figure. The light of an object incoming on the imaging surface of the picture-taking device  18  is subject to photoelectric conversion by the picture-taking device  18  and signal processing by a predetermined signal processing section  20  in the camera  10 . Picture signals in a predetermined form are generated by the signal processing at the signal processing section  20  and outputted to an outside appliance such as a recorder. Picture signals in which later described information on an AF area (AF area information) is superimposed on a taken picture are generated by the signal processing at the signal processing section  20  and outputted to a view finder  14  set on the camera  10 . As AF area information, an AF frame F indicating a range (outline) of an AF area, for example, is displayed on a screen of the view finder  14 . 
     The focus lens FL, the zoom lens ZL and the iris I for imaging lenses are electrically controlled by a controlling system of the lens device  12 . In the embodiment of the present invention, only a control relating to an auto-focus (AF) is described and only a controlling system for controlling a focus lens FL by AF is shown in the figure. 
     On the controlling system of the lens device  12 , a CPU  30 , a driving circuit  32 , a motor  34 , an AF processing section  36  and the like are loaded. The focus lens FL of the picture-taking lenses is connected with the motor  34 , which is driven by control signals outputted from the CPU  30  to the driving circuit  32  and moves the focus lens FL so that the CPU  30  can control the location and moving speed of the focus lens FL. 
     On the other hand, picture signals (luminance signals) generated in the abovementioned manner are sent from the signal processing section  20  of the camera  10  to the lens device  12  and input into the AF processing section  36 . The AF processing section  36  includes an A/D converter  40 , a high path filter (HPF)  42 , a gate circuit  44  and an addition circuit  46 . First, the picture signals input from the camera  10  to the AF processing section  36  are converted into digital signals by the A/D converter  40 . Next, only signals of high frequency component are extracted from the picture signals by HPF  42 . Then, the picture signals of high frequency component are input into a gate circuit  44  and only picture signals within a range corresponding to a predetermined AF area set in the shooting screen are extracted. The range of the AF area for extracting picture signals at the gate circuit  44  is set by AF area signals provided from the CPU  30 . The picture signals in the AF area extracted by the gate circuit  44  is input into the addition circuit  46  and integrated for each field (for each screen). An integrated value obtained at the addition circuit  46  in this manner is a focus evaluation value indicating the degree of the contrast of an object image in an AF area. 
     The CPU  30  controls the focus lens FL, while obtaining the focus evaluation value from the AF processing section  36  and moves the focus lens FL to the location (focus point) where the focus evaluation value become the highest (the maximum). In this manner, a focus of the picture-taking lens is controlled so that an object in the AF area is focused. So called hill-climbing method is used as a method for moving the focus lens FL to a focus point where the focus evaluation value is the highest and the processes below are performed for example. When the CPU  30  starts AF processing, it displaces the focus lens FL by minimum distance to the hyperfocal point and to the infinity (so called wobbling), obtains a focus evaluation value at each displaced point from the AF processing section  36  and compares the values. Based on the result, the CPU  30  detects the direction in which the focus lens FL moves to increase the focus evaluation value. When no direction in which the focus evaluation value increases is detected, the CPU  30  determines that the focus lens FL focuses on the object and sets the focus lens FL to the location before the wobbling. On the other hand, when a direction in which the focus evaluation value increases is detected, the CPU  30  moves the focus lens FL in the direction, sequentially obtaining the focus evaluation values from the AF processing section  36 . When the focus lens FL passes the location where the focus evaluation value is the maximum, the CPU  30  detects the maximum value of the focus evaluation value. When the CPU  30  detects the maximum value of the focus evaluation value, it moves the focus lens FL to the location where the maximum value is detected and stops the lens there. In this manner, the picture-taking lens is set as focusing on the object. The CPU  30  repeats the AF processing to sequentially focus each lens by AF. 
     Now, processing by the CPU  30  relating to the AF area will be described. As shown in  FIG. 2 , an AF area F, which is AF coverage, is set on a shooting screen (or a screen of view finder  14 ) P. 
     To lens device  12 , an AF area operating section  48  (AF area operating device) is connected so that an operator can change a range of the AF area F by manipulating the AF area operating section  48  when the camera  10  has a function of displaying AF area information relating to the range of the AF area F, such as an AF frame indicating the range (outline) of the AF area F on the view finder  14  as shown in  FIG. 2 . 
     On the AF area operating section  48 , operating parts for an operator to designate (change) a range of an AF area including the location, size and shape of the AF area to a desired range on the shooting screen is placed. For example, as operating parts for designating the location of the AF area, a track ball and a joy stick is placed. With the parts, the location of the AF area F can be changed vertically and horizontally (or diagonally) as shown in  FIG. 2 . The initial range of the AF area, for example at turn-on, is predetermined to a standard range, for example. 
     The AF area operating section  48  outputs AF area indicating information indicating a range of an AF area according to manipulation of an operator and provides the AF indicating information to the CPU  30  of the lens device  12 . When the camera  10  has a function of displaying AF area information on the view finder  14 , the CPU  30  sets the range of the AF area according to the AF area indicating information provided from the AF area operating section  48  and provides AF area signals corresponding to the range of the AF area to the gate circuit  44  of the AF processing section  36 . Accordingly, picture signals of the range of the AF area are extracted by the gate circuit  44  and the focus evaluation value is obtained based on the picture signals in the AF area. By performing AF processing on the basis of the focus evaluation value, the CPU  30  performs a focus control so that the object in the AF area is focused. 
     The CPU  30  and a CPU  22  in the camera  10  exchange various signals by communication (e.g., serial communication). When the camera  10  has a function of displaying AF area information on the view finder  14 , the CPU  22  in the camera  10  requires the CPU  30  on the lens device  12  to send the AF area display information for displaying the AF area information on the view finder  14  via the communication. In response to the request of the AF area display information from the CPU  22  in the camera  10 , the CPU  30  sends AF area display information corresponding to a range of a currently set AF area to the CPU  22  in the camera  10 . When the CPU  22  in the camera  10  obtains the AF area display information, the AF area display information is provided to the signal processing section  20 . 
     The signal processing section  20  merges picture signals of a taken picture to be output to the view finder  14  with picture signals of the AF frame indicating a range (outline) of an AF area. Thus, the AF frame is displayed as the AF area information with the taken picture on the view finder  14 . The operator can set a desired range on the shooting screen to an AF area by manipulating the AF area operating section  48  as checking the AF frame on the view finder  14 . 
     In contrast, there is a case that the camera  10  has no function of displaying the AF area information on the view finder as mentioned above. In such a case, as the camera  10  does not request from the CPU  30  in the lens device  12  to send the AF area display information, the CPU  30  in the lens device  12  can determine whether or not the camera  10  has such a function based on whether or not the AF area display information is requested. When the camera  10  does not request AF area information, the CPU  30  makes a change of an AF area impossible. In other words, the CPU  30  does not change a range of an AF area according to the AF area indicating information from the AF area operating section  48 . Then, the CPU  30  reads a predetermined range of an AF area from EEPROM  48  and sets the range as the AF area. This avoids a problem due to a change of an AF area when a camera without a function of displaying AF area information on the view finder  14  is used. The range of an AF area stored on EEPROM  48  can be changed by a user to a desired range. Determination whether the camera  10  has a function of displaying AF area information on the view finder  14  can be performed in a way other than the determination whether the camera  10  requests the AF area displaying information. 
     A series of processes of the abovementioned CPU  30  will be described by flowchart in  FIG. 3 . When the CPU  30  starts communication with the camera  10  (CPU  22 ), it determines whether the camera  10  requests AF area display information (step S 11 ). When it is determined NO, the CPU  30  reads setting information indicating the predetermined range of the AF area from the EEPROM  38  and sets an AF area to a range indicated by the setting information (step S 12 ). 
     On the other hand, when it is determined YES at step S 10 , the CPU  30  obtains the AF area indicating information from the AF area operating section  48  (step S 14 ). Then the CPU  30  sets an AF area to a range indicated by the AF area indicating information and converts the range of the set AF area to the AF area display information for displaying as the AF area information on the view finder  14  (in the form for sending information on the range of the AF area to the camera  10 ) (step S 16 ) and sends the AF area display information to the camera  10  (step S 18 ). The processes of the above steps S 10 -S 18  are repeated with other processes. 
     Although a range of an AF area that can be changed by the AF area operating section  48  has been described as the location, size and shape of the AF area in the abovementioned embodiments, it is not limited that all the elements to determine a range of an AF area is changeable, and any one element or any elements may be changed and the other elements may remain unchanged. For example, only the location of the AF area can be changed and the shape can be fixed to a rectangle and the size can also be fixed. Or, the location and size of the AF area can be changed and the shape can be fixed to a rectangle. 
     When elements including the location among the elements determining a range of an AF area can be changed and the camera  10  has no function of displaying AF area information on the view finder  14 , only the location of the AF area is fixed unchangeable to the predetermined location (e.g., at a center of the screen) and the other elements remain changeable. If the location of an AF area is fixed, no big problem can occur even when AF area information such as an AF frame is not displayed on the view finder  14  and elements other than the location (e.g., size) is changed. 
     Although whether a change of a range of an AF area is made possible or impossible (made invalid) is automatically switched based on whether the camera  10  has a function of displaying the AF area information on the view finder  14  in the abovementioned embodiment, the present invention is not limited to this embodiment and adapted so that an operator selects either of them via a predetermined selecting device (switch). 
     Although the abovementioned embodiment is described by the case that the present invention is applied in Contrast type AF, the present invention can be applied to the cases other than Contrast type AF shown in the abovementioned embodiment.