Patent Publication Number: US-7907189-B2

Title: Imaging apparatus having a lens device for a zooming control operation and the method of using the same

Description:
This application is a continuation of prior application Ser. No. 10/643,805, filed Aug. 18, 2003, which is in turn a divisional application of Ser. No. 09/208,546, filed Dec. 9, 1998, to both of which priority under 35 U.S.C. §120 is claimed. This application claims a benefit of priority based on Japanese Patent Application No. 9-341363, filed on Dec. 11, 1997; No. 9-342756, filed Dec. 12, 1997; No. 9-342757, filed Dec. 12, 1997; and No. 9-342758, filed Dec. 12, 1997, each of which is hereby incorporated by reference herein in its entirety as if fully set forth herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a lens device having a zoom lens, an imaging device equipped with this lens device and adapted to perform electronic zooming, an imaging system, a lens control system and a computer readable storage medium. 
     2. Description of the Related Art 
       FIG. 4  is a block diagram showing the configuration of a conventional lens-interchangeable video camera. In this figure, reference numeral  100  designates an interchangeable lens unit; and  200  a camera body unit to which the interchangeable lens unit is detachably attached. In the interchangeable lens unit  100 , reference numeral  101  denotes a fixed front lens group;  102  a variator or zoom lens group for zooming or changing a magnification;  103  a fixed lens group;  104  a compensator or focusing lens group for performing both functions of compensating and focusing. These lens groups  101  to  104  constitute a lens system of inner focusing type. 
     Reference numeral  106  designates a stepping motor for moving the variator lens group  102 ;  108  a rotation shaft that is connected to a gear  107  through the stepping motor  106  and has a screw;  109  a rack that is movably mounted on the rotation shaft  108  and provided with the variator lens group  102 . Reference numeral  105  denotes a driver for driving the stepping motor  106 ; and  110  a zoom encoder for detecting the position of the variator lens group  102 . 
     Reference numeral  112  designates a stepping motor for moving the compensator lens group  104 ;  113  a rotation shaft that is directly connected to a stepping motor  112  and has a screw;  114  a rack that is movably mounted on the rotation shaft  113  and provided with the compensator lens group  104 . Reference numeral  111  denotes a driver for driving the stepping motor  112 . Reference numeral  115  designates a microcomputer (hereunder sometimes referred to as a lens microcomputer) that communicates with a microcomputer  208  of the camera body unit  200  and controls each of the drivers  105  and  111  and receives position detection information from the zoom encoder  110   
     Further, in the camera body unit  200 , reference numeral  201  denotes an imager such as CCD;  202  CDS/AGC circuit for performing a correlated double sampling operation and an automatic gain control operation;  203  A/D converter;  204  a signal processing circuit;  205  an enlargement processing circuit for performing electronic zooming;  206  a signal processing circuit;  207  D/A converter;  208  a microcomputer (hereunder sometimes referred to as a camera microcomputer) for controlling the entire video camera and for communicating with the lens microcomputer  115 ;  210  and  211  zoom switches for moving the variator lens group in a tele or telephoto direction and a wide or wide-angle direction, respectively;  212  and  213  focus switches for moving a focus position to an infinite focus position and to a shortest focus position, respectively; and  209  a group of these switches. 
     Next, an operation of this video camera will be described hereinbelow. When the interchangeable lens unit  100  is attached to the camera body unit  200 , electric power is supplied from the camera body unit  200  to the interchangeable lens unit  100 . Then, an image is formed on the imager  201  from light that comes from an object through the lens groups  101  to  104 . Video signals obtained by photoelectric conversion performed in the imager  201  are processed by the CDS/AGC circuit  202 . Subsequently, the video signals are converted by the A/D converter  203  into digital video signals which are then sent to the signal processing circuit  204 . After the signal processing circuit  204  gamma-corrects the digital video signals, the enlargement processing circuit  205  performs enlargement processing (to be described later) on the gamma-corrected video signals. Further, the signal processing circuit  206  performs balanced modulation on color signals. The processed signals are converted by the D/A converter  207  into digital analog video signals which are then sent to VTR (not shown). 
     Next, operations of the lens microcomputer  115  and zooming and focusing operations will be described hereinbelow. When the zooming or focusing operation is designated, the lens microcomputer  115  determines the rotation speed and direction of each of the motors  106  and  112  by executing programs. Further, the lens microcomputer  115  outputs control signals representing the determined rotation speed and direction, and controls the stepping motors  106  and  112  through the drivers  105  and  111 , respectively. Incidentally, regarding the zooming operation, the lens microcomputer  115  determines the rotation direction of the motor  106  according to the states of the switches  210  and  211 , which are represented by signals outputted from the camera microcomputer  208 , respectively. Regarding the focusing operation, in the case of adjusting focus by a manual operation, the rotation direction of the motor  112  is determined according to the states of the switches  212  and  213 , which are represented by signals sent from the camera microcomputer  208 . On the other hand, in the case of adjusting focus by an autofocusing (AF) operation, the rotation direction of the motor  112  is determined by executing AF processing routine in the lens microcomputer  115 . 
     Each of the motors  106  and  112  rotate by being controlled according to the aforementioned control signals. Thus, the rotation shaft  108  rotates through the gear  107 . Moreover, the rotation shaft  113  rotates. Each of the racks  109  and  114  moves back and forth together with a corresponding one of the lens groups  102  and  104 . Consequently, predetermined zoomed and focused conditions of the video camera are obtained. 
     Next, enlargement processing (namely, electronic zooming) to be performed on an image in the enlargement processing circuit  205  by utilizing linear interpolation will be described hereinbelow. Enlargement processing is performed by operating the zoom switches  210  and  211  by a cameraman. When an original image shown in the left side part of  FIG. 5A  is expanded into an enlarged image shown in the right-side part thereof, scan lines representing the original image are as illustrated in the left-side part of  FIG. 5B , and scan lines representing the enlarged image are as illustrated in the right-side part thereof. In this case, the scan lines, which represent the enlarged image and are respectively indicated by dashed lines in the right-side part of  FIG. 5B , are newly formed from the scan lines A to F representing the original image shown in the-left-side part thereof. Thus, each of the scan lines respectively indicated by dashed lines is obtained by multiplying data representing corresponding ones of scan lines, which are respectively indicated by solid lines in the right-side part of  FIG. 5B , by weight factors (or correction coefficients) corresponding to the distances thereof and adding up resultant data. The original image can be enlarged at an arbitrary enlargement magnification by performing such linear interpolation processing in the vertical and horizontal directions. 
       FIG. 6  shows the configuration of the enlargement processing circuit  205 . For simplicity of description, this figure illustrates only the vertical enlargement processing. As shown in  FIG. 6 , input video signals  300  are stored in a memory circuit  301  under the control of a memory control signal generating circuit  302 . Microcomputer interface circuit  304  receives an enlargement magnification and enlargement information from the camera microcomputer  208 . Based on this, an enlarged magnification determining circuit  303  outputs the enlargement magnification to the memory control signal generating circuit  302  and an interpolation coefficient generating circuit  308 . The memory control signal generating circuit  302  reads signals, which respectively represent an nth line and an (n−1)th line delayed by 1 H (namely, one horizontal scanning interval) from the nth line, from the memory circuit  301 . The interpolation coefficient generating circuit  308  generates interpolation coefficients corresponding to the enlargement magnification and gives the generated interpolation coefficients to multipliers  305  and  306 . These multipliers multiply the signals, which respectively represent an nth line and an (n−1)th line, by the interpolation coefficients. Outputs of these multipliers are added up in an adder  307 . Resultant signal is outputted therefrom as an output video signal  310 . 
     Next, processing to be performed in the camera microcomputer  208  will be described with reference to a flowchart of  FIG. 7 . In step  401 , the processing is started. Then, predetermined initialization is performed in step  402 . Subsequently, in step  403 , the camera microcomputer  208  waits for a vertical synchronization signal Vd. When the vertical synchronization signal Vd is inputted to the camera microcomputer  208 , control proceeds to step  404  whereupon the camera microcomputer  208  makes predetermined communication with the lens microcomputer  115 . Thereafter, the camera microcomputer  208  performs AF operation and an automatic exposure (AE) operation in step  405 . Then, the camera microcomputer  208  performs electronic and optical zooming in step  406 . Subsequently, control returns to step  403 . 
       FIG. 8  is a flowchart illustrating the operation performed in the aforementioned step  404  in more detail. As illustrated in  FIG. 8 , the operation is started in step  501 . Then, the camera microcomputer  208  sends a communication request signal to the lens microcomputer  115  in step  502 . Subsequently, control advances to step  503  whereupon the camera microcomputer  208  checks whether a communication enabling signal comes thereto from the lens microcomputer  115 . If so, control proceeds to step  505 . If not, control advances to step  504  whereupon the camera microcomputer  208  waits for a communication enabling signal for a predetermined time. If no communication enabling signal comes thereto within the predetermined time, the camera microcomputer  208  gives up communicating with the lens microcomputer  115 . Then, the camera microcomputer  208  finishes the communicating operation in step  506 . 
     In the case that a communication enabling signals comes thereto within the predetermined time, bidirectional communication between the camera microcomputer  208  and the lens microcomputer  115  is performed in step  505 . At that time, data sent from the camera microcomputer  208  to the lens microcomputer  115  includes information on the halt or moving direction of the zoom lens group, which is obtained as a result of the operation performed in the aforementioned step  406 . Further, data sent to the camera microcomputer  208  from the lens microcomputer  115  includes information on the inhibition/permission of electronic zooming. Subsequently, the camera microcomputer  208  terminates the communicating operation in step  506 . Then, in step  507 , control returns to the aforementioned step  406 . 
     Next, the step  406  will be described in detail with reference to a flowchart of  FIG. 9 . As shown in  FIG. 9 , an operation is started in step  601 . Then, in step  602 , the camera microcomputer  208  checks whether the camera is performing zooming. When both the zoom switches  210  and  211  are pushed, or when neither of the zoom switches  210  and  211  is pushed, control proceeds to step  607 . When only one of the zoom switches  210  and  211  is pushed, control proceeds to step  603  whereupon it is checked which of the zoom switches  210  and  211  is pushed. If the “TELE” switch  210  is pushed, control advances to step  604 . If the “WIDE” switch  211  is pushed, control proceeds to step  608 . 
     In step  604 , the camera microcomputer  208  checks whether electronic zooming permission information comes thereto from the lens microcomputer  115 . If the camera microcomputer  208  is permitted to perform electronic zooming, control advances to step  605 . If not, control proceeds to step  610 . In step  605 , the camera microcomputer  208  checks whether the zoom lens group  102  is placed at a tele end. If so, control advances to step  607 . Otherwise, control proceeds to step  606  whereupon an electronic zooming operation is performed by increasing or decreasing the aforementioned interpolation coefficients according to which of the switches  210  and  211 , and whereupon the camera microcomputer  208  controls the enlargement processing circuit  205  according to a result of the zooming operation. Upon completion of this control operation, the camera microcomputer  208  sends a zoom lens stop request signal to the lens microcomputer  115  in step  607 . Further, in step  610 , the camera microcomputer  208  sends the lens microcomputer  115  a request to move the zoom lens group to the tele side. 
     On the other hand, in step  608 , the camera microcomputer  208  checks whether the camera is now performing electronic zooming. If so, control proceeds to step  606 . Otherwise, control advances to step  609  whereupon the camera microcomputer  208  sends the lens microcomputer  115  a request to move the zoom lens group to a wide side. Upon completion of the operation to be performed in one of the aforementioned steps  607 ,  609  and  610 , control returns to a main routine in step  611 . 
       FIG. 10  is a flowchart illustrating processing concerning a zooming operation, which is a part of the entire processing to be performed by the lens microcomputer  115 . As illustrated in  FIG. 10 , the processing is started in step  701 . Then, in step  702 , the lens microcomputer  115  checks whether the aforementioned zoom lens stop request signal comes thereto from the camera microcomputer  208 . If so, namely, if the zoom lens group should be stopped, control proceeds to step  708 . Otherwise, control advances to step  703  whereupon the lens microcomputer  115  checks according to the information sent by the camera microcomputer  208  which of the tele direction and the wide direction the moving direction of the zoom lens group is. If the moving direction of the zoom lens group is the tele direction, control proceeds to step  704 . If the wide direction, control advances to step  705 . 
     In step  704 , the lens microcomputer  115  checks whether the zoom lens group is positioned at the tele end. If so, control proceeds to step  708 . Otherwise, control advances to step  706 . Further, in step  705 , the lens microcomputer  115  checks whether the zoom lens group is positioned at the wide end. If so, control proceeds to step  708 . Otherwise, control advances to step  706 . The moving speed of the zoom lens group and the moving speed and direction of the focusing lens group are calculated in step  706 . According to a result of this calculation, the zoom lens group and the focusing lens group are driven in step  707 . Furthermore, in step  708 , the zoom lens group is stopped. 
     Upon completion of the operation performed in step  707  or  708 , the lens microcomputer  115  checks in step  709  whether the zoom lens group is placed at the tele end. If so, control proceeds to step  710 . Otherwise, control advances to step  711 . In step  710 , the lens microcomputer  115  sends the camera microcomputer  208  an electronic zooming enabling signal. Further, in step  711 , the lens microcomputer  115  sends the camera microcomputer  208  an electronic zooming inhibiting signal. Upon completion of the operation performed in step  710  or  711 , control returns to the main routine in step  712 . 
     As described above, in the case that the zoom switches  210  and  211  are provided only in the camera body unit  200 , optical zooming and electronic zooming are realized under the control of the camera microcomputer  208 . However, in the case that a zoom ring  116  to be used for manually performing a zooming operation is provided in the interchangeable lens unit  100  as illustrated in  FIG. 3 , the conventional video camera has the problem that it is difficult to achieve suitable and smooth control of optical zooming and electronic zooming. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the present invention is to solve the aforesaid problem, thereby achieving suitable control of zooming operations in the case that zooming operation means are provided at both camera-body-side and lens-side portions, respectively. 
     Further, another object of the present invention is to smoothly switch between an optical zooming function and an electronic zooming function. 
     Moreover, still another object of the present invention is to enable an electronic zooming function independent of whether a zooming mechanism is provided in a lens-side portion. 
     To solve the aforementioned problem and to achieve the foregoing objects, according to an aspect of the present invention, there is provided a lens device which comprises variator lens means for performing a zooming operation, zoom operating means for operating the aforesaid variator lens means, information output-means for outputting operation information sent from the aforesaid zoom operating means and for outputting zooming position information of the aforesaid variator lens means, information input means for receiving control information, which is used for controlling the aforesaid variator lens means, from an external device, and variator control means for controlling a zooming operation of the aforesaid variator lens means according to the inputted control information. 
     Further, according to another aspect of the present invention, there is provided an imaging apparatus which comprises imaging means for imaging an object and for *outputting an image signal, information input means for receiving external zoom operating information and zoom position information to be supplied to external variator lens means, zoom operating means for receiving internal zoom operating information to be supplied to the aforesaid external variator lens means and information output means for generating and outputting optical zooming control information to be used for controlling a zooming operation of the aforesaid external variator lens means according to the inputted external zoom operating information and the inputted zoom position information and the internal zoom operating information received from the aforesaid zoom operating means. 
     Moreover, according to still another aspect of the present invention, there is provided an imaging system that comprises a lens device having a variator lens means for performing a zooming operation, lens-side zoom operating means for operating the aforesaid variator lens means, lens-side information output means for outputting lens-side zoom operating information and zoom position information on a zoom position of the aforesaid variator lens means, which are received from the aforesaid lens-side zoom operating means, lens-side information input means for receiving optical zoom control information to be used for controlling the aforesaid variator lens means, and variator control means for controlling a zooming operation of the aforesaid variator lens means according to the received control information, and that further has an imaging apparatus having imaging means for imaging an object and for outputting an image signal, camera-body-side information input means for receiving the lens-side zoom operating information and zoom position information from the aforesaid lens-side information output means, camera-body-side zoom operating means for receiving camera-body-side zoom operating information to be supplied to the aforesaid variator lens means, and camera-body-side information output means for generating optical zooming control information to be used to control a zooming operation of the aforesaid variator lens means, according to the received lens-side zoom operating information and the received zoom position information and the camera-body-side zoom operating information and for outputting the optical zooming control information to the aforesaid lens-side information input means. 
     Furthermore, according to yet another aspect of the present invention, there is provided a computer readable storage medium for storing a program causing a computer to execute the steps of outputting operation information, which is obtained when a variator lens is operated, and zoom position information which represents a zoom position of the aforesaid variator lens, inputting control information, which is used for controlling the aforesaid variator lens, from an external device, and controlling the aforesaid variator lens according to the inputted control information. 
     Further, according to still another aspect of the present invention, there is provided a computer readable storage medium for storing a program causing a computer to execute the steps of imaging an object and outputting an image signal, receiving external zoom operating information and zoom position information to be supplied to an external variator lens, receiving internal zoom operating information to be supplied to the aforesaid external variator lens, and generating and outputting optical zooming control information to be used for controlling a zooming operation of the aforesaid external variator lens according to the inputted external zoom operating information and the inputted zoom position information and the internal zoom operating information. 
     Further, according to yet another aspect of the present invention, there is provided a lens device which comprises variator lens means for performing a zooming operation, zoom operating means for operating the aforesaid variator lens means, information output means for outputting first zoom operating information, which is received from the aforesaid zoom operating means, and zoom position information representing a zoom position of the aforesaid variator lens means, information input means for receiving second zoom operating information and zooming inhibition information from an external device, and variator control means for controlling a zooming operation of the aforesaid variator lens means according to the first zoom operating information, the inputted second zoom operating information and the inputted zooming inhibition information. 
     Moreover, according to still another aspect of the present invention, there is provided a camera apparatus which comprises imaging means for imaging an object and for outputting an image signal, information input means for receiving first zoom operating information and zoom position information to be supplied to external variator lens means, zoom operating means for receiving second zoom operating information to be supplied to the aforesaid external variator lens means, information output means for outputting the second zooming control information and optical zooming inhibition information to be used for inhibiting a zooming operation of the aforesaid external variator lens means, electronic zooming means for performing electronic enlargement processing on an image represented by the image signal, and electronic zooming control means for controlling the aforesaid electronic zooming means according to the first zoom operating information, the zoom position information and the second zoom operating information. 
     Furthermore, according to yet another aspect of the present invention, there is provided a camera system which comprises a lens device having a variator lens means for performing a zooming operation, lens-side zoom operating means for operating the aforesaid variator lens means, lens-side information output means for outputting first zoom operating information, which is received from the aforesaid lens-side zoom operating means, and zoom position information on a zoom position of the aforesaid variator lens means, lens-side information input means for receiving second zoom operating information and zooming inhibition information from an external device and variator control means for controlling a zooming operation of the aforesaid variator lens means according to the received second zoom operating information and the zooming inhibition information and the first zoom operating information, and further comprises an imaging apparatus having imaging means for imaging an object and for outputting an image signal, camera-body-side information input means for receiving the first zoom operating information and zoom position information from the aforesaid lens-side information output means, camera-body-side zoom operating means for receiving the second zoom operating information to be supplied to the aforesaid variator lens means, and camera-body-side information output means for outputting the aforesaid lens-side information input means the second zoom operating information and the optical zooming inhibition which is used for inhibiting the aforesaid variator lens means from performing a zooming operation, electronic zooming means for performing electronic enlargement processing on an image represented by the image signal, and electronic zooming control means for controlling the aforesaid electronic zooming means according to the first zoom operating information, the zoom position information and the second zoom operating information. 
     Further, according to still another aspect of the present invention, there is provided a computer readable storage medium for storing a program causing a computer to execute the steps of outputting first zoom operating information, which is obtained when a variator lens is operated, and zoom position information which represents a zoom position of the aforesaid variator lens, inputting second zoom operating information and zooming inhibition information, which are received from an external device, and controlling the aforesaid variator lens according to the inputted second zoom operating information, the inputted zooming inhibition information and the first zoom operating information. 
     Moreover, according to yet another aspect of the present invention, there is provided a computer readable storage medium for storing a program causing a computer to execute the steps of imaging an object and outputting an image signal, receiving first zoom operating information and zoom position information to be supplied to an external variator lens, receiving second zoom operating information to be supplied to the aforesaid external variator lens, outputting the second zooming control information and optical zooming inhibition information to be used for inhibiting the aforesaid external variator lens from performing a zooming operation, and performing electronic zooming for electronically enlarging an image represented by the image signal according to the first zoom operating information and the second zoom operating information and the zoom position information. 
     Furthermore, according to still another aspect of the present invention, there is provided a lens control system which comprises a first device having optical variator means for optically changing a magnification of an image, a second device having electronic variator means for electronically enlarging an image by signal processing, and first and second variator operating members respectively provided in the aforesaid first and second devices. In this lens control system, when the aforesaid optical variator means is operated, the aforesaid optical variator means is controlled in the aforesaid first device according to information for operating the aforesaid first and second variator operating members. Further, when the aforesaid electronic variator means is operated, the aforesaid electronic variator means is controlled in the aforesaid second device according to information for operating the aforesaid first and second variator operating members. Furthermore, during the aforesaid electronic variator means is operated, the aforesaid first device inhibits the aforesaid optical variator means from operating. 
     Further, according to yet another aspect of the present invention, there is provided a camera system which comprises a lens device having an optical variator lens for optically changing a magnification of an image, a camera device having electronic variator means for electronically enlarging an image by signal processing, a lens-device-side variator operating member, and a camera-device-side variator operating member. In this camera system, when the aforesaid optical variator lens is operated, the aforesaid optical variator lens is controlled in the aforesaid lens device according to information for operating the aforesaid lens-device-side and camera-device-side variator operating members. Further, when the aforesaid electronic variator means is operated, the aforesaid electronic variator means is controlled in the aforesaid camera device according to information for operating the aforesaid lens-device-side and camera-device-side variator operating members. Moreover, during the aforesaid electronic variator means is operated, a signal causing the aforesaid lens device to inhibit the aforesaid optical variator lens from operating is transmitted to the aforesaid lens device. 
     Furthermore, according to still another aspect of the present invention, there is provided a lens device which comprises variator lens means for performing a zooming operation, control means for controlling the zooming operation of the aforesaid variator lens means, and signal output means for outputting an electronic zooming enabling signal and an electronic zooming preparation signal for giving advance notice of the electric zooming enabling signal, during the zooming operation. 
     Moreover, according to yet another aspect of the present invention, there is provided an imaging apparatus which comprises imaging means for imaging an object and for outputting an image signal, electronic zooming means for electronically enlarging an image represented by the image signal, signal input means for receiving an electronic zooming preparation permission signal and an electronic zooming enabling signal, and control means for enabling control of the aforesaid electronic zooming means when each of the electronic zooming preparation permission signal and the electronic zooming enabling signal is received. 
     Further, according to still another aspect of the present invention, there is provided an imaging system which comprises a lens device having a variator lens means for performing a zooming operation, first control means for controlling the zooming operation of the aforesaid variator lens means, and signal output means for outputting an electronic zooming enabling signal and an electronic zooming preparation permission signal which gives advance notice of the electric zooming enabling signal, during the zooming operation, and which further comprises an imaging apparatus having imaging means for imaging an object and for outputting an image signal, electronic zooming means for performing electronic enlargement processing on an image represented by the image signal, signal input means for receiving an electronic zooming preparation permission signal and an electronic zooming enabling signal, and second control means for enabling control of the aforesaid electronic zooming means when each of the electronic zooming preparation permission signal and the electronic zooming enabling signal is received. 
     Furthermore, according to yet another aspect of the present invention, there is provided a computer readable storage medium for storing a program causing a computer to execute the steps of controlling a zooming operation performed by a variator lens, and outputting an electronic zooming enabling signal and an electronic zooming preparation permission signal which gives advance notice of the electric zooming enabling signal, during the zooming operation. 
     Moreover, according to still another aspect of the present invention, there is provided a computer readable storage medium for storing a program causing a computer to execute the steps of imaging an object and outputting an image signal, performing electronic zooming for electronically enlarging an image represented by the image signal, receiving an electronic zooming preparation permission signal and an electronic zooming enabling signal, and enabling the electronic zooming when each of the electronic zooming preparation permission signal and the electronic zooming enabling signal is received. 
     Further, according to yet another aspect of the present invention, there is provided an imaging apparatus which comprises imaging means, electronic zooming means for enlarging an image taken by the aforesaid imaging means, zoom input means for receiving zoom operating information, lens information input means for receiving first zoom information, which indicates presence or absence of an optical zooming mechanism in an external lens means, and second zoom information which indicates presence or absence of an optical zooming mechanism, which does not operate in response to a control signal received from an external device, in the aforesaid external lens means, control output means for outputting an optical zooming control signal which instructs the aforesaid external lens means to perform a zooming operation and control means for controlling the aforesaid optical zooming mechanism of the aforesaid external lens means through the aforesaid electronic zooming means and the aforesaid lens control output means according to the zoom operating information inputted to the aforesaid zoom input means in such a manner as to be able to be driven, in a case that the first zoom information indicates the presence of the aforesaid optical zooming mechanism and that the second zoom information indicates the absence of the aforesaid optical zooming mechanism, and for controlling the aforesaid electronic zooming means in such a manner as to be able to be driven, in a case that the first zoom information indicates the absence of the aforesaid optical zooming mechanism, and for controlling the aforesaid electronic zooming means in such a manner as not to be driven, in a case that the second zoom information indicates the presence of the aforesaid optical zooming mechanism. 
     Furthermore, according to still another aspect of the present invention, there is provided an imaging apparatus which comprises imaging means, electronic zooming means for enlarging an image taken by the aforesaid imaging means, zoom input means for receiving zoom operating information, lens information input means for receiving zoom information, which indicates presence or absence of an optical zooming mechanism in an external lens means, and specific lens group information which indicates whether the aforesaid external lens means belongs to a specific lens group, control output means for outputting an optical zooming control signal which instructs the aforesaid external lens means to perform a zooming operation, and control means for controlling the aforesaid optical zooming mechanism of the aforesaid external lens means through the aforesaid electronic zooming means and the aforesaid lens control output means according to the zoom operating information inputted to the aforesaid zoom input means in such a manner as to be able to be driven, in a case where the zoom information indicates the presence of the aforesaid optical zooming mechanism and where the specific lens group information indicates that the aforesaid external lens means does not belong to the aforesaid specific lens group, and for controlling the aforesaid electronic zooming means in such a manner as to be able to be driven, in a case where the zoom information indicates the absence of the aforesaid optical zooming mechanism, and for controlling the aforesaid electronic zooming means in such a manner as not to be driven, in a case where the specific lens group information indicates that the aforesaid external lens means belongs to the aforesaid specific lens group. 
     Other features, objects and advantages of the present invention will become apparent from the following description of preferred embodiments with reference to the drawings in which like reference characters designate like or corresponding parts throughout several views. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a flowchart illustrating processing concerning a zooming operation, which is performed by a lens microcomputer of a first embodiment of the present invention; 
         FIG. 2  is a flowchart illustrating processing concerning a zooming operation, which is performed by a camera microcomputer of the first embodiment of the present invention; 
         FIG. 3  is a block diagram showing the configuration of a lens-interchangeable video camera according to the first embodiment of the present invention; 
         FIG. 4  is a block diagram showing the configuration of the conventional lens-interchangeable video camera; 
         FIGS. 5A and 5B  are diagrams illustrating electronic zooming by the conventional video camera; 
         FIG. 6  is a block diagram showing the configuration of the enlargement processing circuit of the conventional video camera; 
         FIG. 7  is a flowchart illustrating the processing to be performed by the camera microcomputer of the conventional video camera; 
         FIG. 8  is a flowchart illustrating the processing concerning communication to be performed by the camera microcomputer of the conventional video camera; 
         FIG. 9  is a flowchart illustrating the processing concerning zooming to be performed by the camera microcomputer of the conventional video camera; 
         FIG. 10  is a flowchart illustrating the processing concerning zooming to be performed by the lens microcomputer of the conventional video camera; 
         FIG. 11  is a flowchart illustrating processing concerning zooming to be performed by a lens microcomputer of a second embodiment of the present invention; 
         FIG. 12  is a flowchart illustrating processing concerning zooming to be performed by a camera microcomputer of the second embodiment of the present invention; 
         FIG. 13  is a block diagram showing another example of the configuration of the enlargement processing circuit of the conventional video camera; 
         FIG. 14  is a diagram illustrating results of an actual zooming operation that is conducted according to processing performed by lens and camera microcomputers of the second embodiment of the present invention; 
         FIG. 15  is a block diagram showing the configuration of a lens-interchangeable video camera according to a third embodiment of the present invention; 
         FIG. 16  is a flowchart illustrating processing concerning a zooming operation, which is performed by a lens microcomputer of the third embodiment of the present invention; 
         FIG. 17  is a flowchart illustrating processing concerning a zooming operation, which is performed by a camera microcomputer of the third embodiment of the present invention; 
         FIG. 18  is a diagram illustrating results of an actual zooming operation that is conducted according to processing performed by the lens and camera microcomputers of the third embodiment of the present invention; 
         FIG. 19  is a diagram showing the configuration of an interchangeable lens unit; 
         FIG. 20  is a diagram showing the configuration of another interchangeable lens unit; 
         FIG. 21  is a flowchart detailedly illustrating zooming processing to be performed by a camera microcomputer of a fourth embodiment of the present invention; 
         FIG. 22  is a flowchart illustrating zooming processing to be performed by a camera microcomputer of the interchangeable lens unit of  FIG. 19  in the fourth embodiment of the present invention; 
         FIG. 23  is a flowchart illustrating zooming processing to be performed by a camera microcomputer of the interchangeable lens unit of  FIG. 20  in the fourth embodiment of the present invention; 
         FIG. 24  is a flowchart illustrating zooming processing to be performed by a camera microcomputer of the interchangeable lens unit of  FIG. 4  in the fourth embodiment of the present invention; 
         FIG. 25  is a flowchart detailedly illustrating zooming processing to be performed by a camera microcomputer of a fifth embodiment of the present invention; 
         FIG. 26  is a flowchart illustrating zooming processing to be performed by the camera microcomputer of the interchangeable lens unit of  FIG. 19  in the fifth embodiment of the present invention; 
         FIG. 27  is a flowchart illustrating zooming processing to be performed by the camera microcomputer of the interchangeable lens unit of  FIG. 20  in the fifth embodiment of the present invention; and 
         FIG. 28  is a flowchart illustrating zooming processing to be performed by the camera microcomputer of the interchangeable lens unit of  FIG. 4  in the fifth embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
     First Embodiment 
     A lens-interchangeable video camera used for the first embodiment of the present invention is constituted as illustrated in  FIG. 3 . In  FIGS. 3 and 4 , same reference numerals designate substantially the same constituent elements. Operating information of a zoom ring  116  (lens-side zoom key information) is inputted to a lens microcomputer  115 . It is detected in the lens microcomputer  115  which of tele-side and wide-side zooming directions corresponds to a direction in which the zoom ring  116  is operated. 
     Further, a program for performing processing in the lens microcomputer  115  according to the flowchart of  FIG. 1  is stored in a storage medium  117 . Moreover, programs for performing processing in the camera microcomputer  208  according to the flowcharts of  FIGS. 2 ,  7  and  8  are stored in a storage medium  214 . Semiconductor memories, optical disks, magneto-optic disks or magnetic media may be used as these storage media  117  and  214 . 
     Next, processing to be performed by the lens microcomputer  115  of the first embodiment of the present invention will be described. 
       FIG. 1  is a flowchart illustrating processing concerning a zooming operation, which is a part of the entire processing to be performed by the lens microcomputer  115 . In step  801 , the processing is started. Then, in step  802 , the lens microcomputer  115  checks whether a zoom lens stop request signal comes thereto from a camera microcomputer  208 . If the zoom lens stop request signal has already come thereto, control proceeds to step  808 . Otherwise, control advances to step  803  whereupon the lens microcomputer  115  checks according to the information sent by the camera microcomputer  208  which of the tele direction and the wide direction the moving direction of the zoom lens group is. If the moving direction of the zoom lens group is the tele direction, control proceeds to step  804 . If the wide direction, control advances to step  805 . 
     In step  804 , the lens microcomputer  115  checks whether the zoom lens group is positioned at the tele end. If so, control proceeds to step  808 . Otherwise, control advances to step  806 . Further, in step  805 , the lens microcomputer  115  checks whether the zoom lens group is positioned at the wide end. If so, control proceeds to step  808 . Otherwise, control advances to step  806 . The moving speed of the zoom lens group and the moving speed and direction of the focusing lens group are calculated in step  806 . According to a result of this calculation, the zoom lens group and the focusing lens group are driven in step  807 . Furthermore, in step  808 , the zoom lens group is stopped. 
     Upon completion of the operation performed in step  807  or  808 , the lens microcomputer  115  checks in step  809  whether the zoom lens group is placed at the tele end. If so, control proceeds to step  810 . Otherwise, control advances to step  811 . In step  810 , the lens microcomputer  115  sends the camera microcomputer  208  an electronic zooming enabling signal. Further, in step  811 , the lens microcomputer  115  sets optical tele end information to be sent to the camera microcomputer  208 . Then, control proceeds to step  812 . Furthermore, in step  811 , the lens microcomputer  115  clears optical tele end information to be sent to the camera microcomputer  208 . Then, control advances to step  812  whereupon the lens microcomputer  115  detects the operating condition of the zoom ring. Moreover, the lens microcomputer  115  provides a setting for sending the camera microcomputer  208  the lens-side zoom key information indicating that the zoom ring  116  is not operated, or that the zoom ring  116  is operated in a direction corresponding to the tele or wide side. Then, control proceeds to step  813 . In this step, control returns to a main routine. 
     Next, processing to be performed in the camera microcomputer  208  of the first embodiment of the present invention will be described. The flow of the processing to be performed by the camera microcomputer  208  is broadly similar to the flow illustrated in  FIGS. 7 and 8 . 
     Step  406  of a process flow of the camera microcomputer  208  will be described in detail with reference to a flowchart of  FIG. 2 . In step  901 , the processing is started. Then, in step  902 , the camera microcomputer  208  checks the lens-side zoom key information sent from the lens microcomputer  115 . If the zoom ring  116  is not operated, control advances to step  903 . Otherwise, control proceeds to step  904  whereupon the camera microcomputer  208  further checks the lens-side zoom key information sent from the lens microcomputer  115 . If the zoom ring  116  is operated in a direction corresponding to the tele side, control advances to step  906 . If the zoom ring  116  is operated in a direction corresponding to the wide side, control proceeds to step  908 . On the other hand, in step  905 , the camera microcomputer  208  checks which of the switches  210  and  211  is pushed in the camera body unit  100 . If the “TELE” switch  210  is pushed, control advances to step  906 . Conversely, if the “WIDE” switch  211  is pushed, control proceeds to step  908 . 
     In step  906 , the camera microcomputer  208  judges from optical tele end information sent from the lens microcomputer  115  whether the zoom lens group is positioned at the optical tele end. If so, control advances to step  907 . Otherwise, control proceeds to step  910 . Then, in step  907 , the camera microcomputer  208  checks whether the zoom lens group is placed at the tele end in the case of electronic zooming. If so, control advances to step  911 . Otherwise, control proceeds to step  909 . On the other hand, in step  908 , the camera microcomputer  208  checks whether an electronic zooming operation is currently being performed. If so, control advances to step  909 . Otherwise, control proceeds to step  912 . 
     In this step  912 , the camera microcomputer  208  establishes a setting for sending the lens microcomputer  115  a request signal to be used for moving the zoom lens group to the wide side. Further, in step  909 , an electronic zooming operation is performed by increasing or decreasing the aforementioned interpolation coefficients according to which of the switches  210  and  211  is pushed. Moreover, the camera microcomputer  208  controls the enlargement processing circuit  205  according to a result of the electronic zooming operation. Then, control advances to step  911  whereupon the camera microcomputer  208  provides a setting for sending the lens microcomputer  115  a zoom lens stop request signal. On the other hand, the camera microcomputer  208  establishes a setting for sending the lens microcomputer  115  a request signal to be used for moving the zoom lens group to the tele side. Upon completion of the operation to be performed in one of the aforementioned steps  910 ,  911  and  912 , control returns to the main routine in step  913 . 
     Incidentally, it has been described that this embodiment is adapted to detect the zoom operating direction (namely, detect that the zoom lens group is operated toward the tele side or toward the wide side). However, the present invention is easily applied to a case that the camera has multi-zooming-speed in each zoom operating direction. 
     Further, even in the case that the camera body unit has a plurality of zoom operating means or that an external input device, such as a remote control device, for a camera body unit has zoom lens operating means, the present invention is easily applied to such a case by handling these means as a single zoom operating means in the camera body unit. 
     As described above, according to the first embodiment, even if a zoom operating means such as a zoom ring is provided therein, the operating information and the zoom position information are outputted to an external camera. Moreover, a zooming operation is performed according to control information provided by the camera. At that time, the control information is generated in the camera body unit according to the operating information, the zoom position information and zoom operating information produced by a zooming operation of the camera body unit. Thus, even if the zoom operating means are provided in both the lens unit and the camera body unit, respectively, the camera smoothly performs suitable zooming control operations. 
     Furthermore, according to the first embodiment, the operating information and the zoom position information are generated by a zooming operation of the lens unit and inputted to the camera body unit. Then, optical zooming control information is generated according to such inputted information and internal zoom operating information produced by the camera body unit. Subsequently, the optical zooming control information is sent to the lens unit. Thus, even if the zoom operating means are provided in both the lens unit and the camera body unit, respectively, the camera smoothly performs suitable zooming control operations. Furthermore, the camera suitably performs electronic zooming according to the aforementioned information. 
     Second Embodiment 
     A lens-interchangeable video camera used in this second embodiment is constructed in such a manner as to be similar to the video camera used in the first embodiment illustrated in  FIG. 3 . The video camera of the second embodiment is different from that of the first embodiment only in operations thereof. Thus, only the difference therebetween will be described. 
     In the case of a video camera in which a zoom ring  116  to be used for manually performing a zooming operation is provided in an interchangeable lens unit  100  as shown in  FIG. 3 , an operating condition thereof caused by switches is not uniquely determined. Thus, such a video camera has the problem that it is difficult to achieve suitable and smooth control of optical and electronic zooming operations. The second embodiment aims at solving this problem. 
     Hereinafter, the second embodiment will be described with reference to the accompanying drawings. 
     In the case of the second embodiment, a program for performing processing, which includes an operation to be performed in the lens microcomputer  115  according to the flowchart of  FIG. 11 , is stored in a storage medium  117  shown in  FIG. 3 . Moreover, programs for performing processing in the camera microcomputer  208  according to the flowcharts of  FIGS. 12 ,  7  and  8  are stored in a storage medium  214 . Semiconductor memories, optical disks, magneto-optic disks or magnetic media may be used as these storage media  117  and  214 . 
     Next, processing to be performed in the lens microcomputer  115  of the second embodiment of the present invention will be described. 
       FIG. 11  is a flowchart illustrating processing concerning a zooming operation, which is a part of the entire processing to be performed by the lens microcomputer  115 . In step  1001 , the processing is started. Then, in step  1002 , the lens microcomputer  115  checks whether an optical zooming inhibition signal comes thereto from a camera microcomputer  208 . If the optical zooming inhibition signal has already come thereto, control proceeds to step  1009 . Otherwise, control advances to step  1003  whereupon the lens microcomputer  115  checks whether a zoom ring  110  of the interchangeable lens unit  100  is operated. If so, control proceeds to step  1006 . Otherwise, control advances to step  1004 . 
     In step  1004 , the lens microcomputer  115  checks according to the information sent by the camera microcomputer  208  whether zoom switches  210  and  211  of a camera body unit  200  are operated. If so, control proceeds to step  1005 . Otherwise, control advances to step  1009 . In step  1005 , the lens microcomputer  115  judges from the information sent by the camera microcomputer  208  which of the tele direction and the wide direction the operating direction in which the zoom lens group is operated. If such an operating direction of the zoom lens group is the tele direction, control proceeds to step  1008 . If the wide direction, control advances to step  1007 . On the other hand, in step  1006 , the lens microcomputer  115  judges which of the tele direction and the wide direction corresponds to the operating direction in which the zoom ring  116  is operated. If such an operating direction of the zoom ring  116  corresponds to the tele direction, control proceeds to step  1008 . If corresponding to the wide direction, control advances to step  1007 . 
     In step  1008 , the lens microcomputer  115  checks whether the zoom lens group is positioned at the tele end. If so, control proceeds to step  1009 . Otherwise, control advances to step  1010 . Further, in step  1007 , the lens microcomputer  115  checks whether the zoom lens group is positioned at the wide end. If so, control proceeds to step  1009 . Otherwise, control advances to step  1010 . The moving speed of the zoom lens group and the moving speed and direction of the focusing lens group are calculated in step  1010 . According to a result of this calculation, the zoom lens group and the focusing lens group are driven in step  1011 . 
     Furthermore, in step  1009 , the zoom lens group is stopped. 
     Upon completion of the operation performed in step  1009  or  1011 , the lens microcomputer  115  checks in step  1012  whether the zoom lens group is placed at the tele end. If so, control proceeds to step  1013 . Otherwise, control advances to step  1014 . In step  1013 , the lens microcomputer  115  sets optical tele end information to be sent to the camera microcomputer  208 . Then, control proceeds to step  1015 . Furthermore, in step  1014 , the lens microcomputer  115  clears optical tele end information to be sent to the camera microcomputer  208 . Then, control advances to step  1015  whereupon the lens microcomputer  115  detects the operating condition of the zoom ring  116 . Moreover, the lens microcomputer  115  provides a setting for sending the camera microcomputer  208  the lens-side zoom key information indicating that the zoom ring  116  is not operated, or that the zoom ring  116  is operated in a direction corresponding to the tele or wide side. Then, control proceeds to step  1016 . In this step, control returns to a main routine. 
     Next, processing to be performed in the camera microcomputer  208  of the second embodiment of the present invention will be described. The flow of the processing to be performed by the camera microcomputer  208  is broadly similar to the flow illustrated in  FIGS. 7 and 8 . 
     Step  406  of a process flow of the camera microcomputer  208  will be described in detail with reference to a flowchart of  FIG. 12 . In step  1101 , the processing is started. Then, in step  1102 , the camera microcomputer  208  checks the zoom switches  210  and  211  of the camera body unit  100 . Further, the camera microcomputer  208  makes preparations for sending the lens microcomputer  115  a signal indicating that the zoom switches  210  and  211  are not operated or that the zoom switches  210  and  211  are operated in the tele or wide direction. 
     In step  1103 , the camera microcomputer  208  checks the lens-side zoom key information sent from the lens microcomputer  115 . If the zoom ring  116  is not operated, control advances to step  1104 . Otherwise, control proceeds to step  1105  whereupon the camera microcomputer  208  further checks the lens-side zoom key information sent from the lens microcomputer  115 . If the zoom ring  116  is operated in a direction corresponding to the tele side, control advances to step  1107 . If the zoom ring  116  is operated in a direction corresponding to the wide side, control proceeds to step  1109 . On the other hand, in step  1104 , the camera microcomputer  208  checks whether the switches  210  and  211  are pushed in the camera body unit  100 . If so, control advances to step  1106 . Otherwise, control proceeds to step  1111 . In step  1106 , the camera microcomputer  208  checks which of the switches  210  and  211  is pushed in the camera body unit  100 . If the “TELE” switch  210  is pushed, control advances to step  1107 . Conversely, if the “WIDE” switch  211  is pushed, control proceeds to step  1109 . 
     In step  1107 , the camera microcomputer  208  judges from optical tele end information sent from the lens microcomputer  115  whether the zoom lens group is positioned at the optical tele end. If so, control advances to step  1108 . Otherwise, control proceeds to step  1112 . Then, in step  1108 , the camera microcomputer  208  checks whether the zoom lens group is placed at the tele end in the case of electronic zooming. If so, control advances to step  1111 . Otherwise, control proceeds to step  1110 . On the other hand, in step  1109 , the camera microcomputer  208  checks whether an electronic zooming operation is currently being performed. If so, control advances to step  1110 . Otherwise, control proceeds to step  1112 . 
     In step  1110 , an electronic zooming operation is performed by increasing or decreasing the aforementioned interpolation coefficients according to which of the switches  210  and  211  is pushed. Moreover, the camera microcomputer  208  controls an enlargement processing circuit  205  according to a result of the electronic zooming operation. Then, control advances to step  1111  whereupon the camera microcomputer  208  provides a setting for sending the lens microcomputer  115  an optical zooming inhibition signal. Subsequently, control proceeds to step  1112  whereupon control returns to the main routine. 
     Incidentally, it has been described that the second embodiment is adapted to detect the zoom operating direction (namely, detect that the zoom lens group is operated toward the tele side or toward the wide side). However, the present invention is easily applied to a case that the camera has multi-zooming-speed in each zoom operating direction. 
     Further, even in the case that the camera body unit has a plurality of zoom operating means or that an external input device, such as a remote control device, for a camera body unit has zoom lens operating means, the present invention is easily applied to such a case by handling these means as a single zoom operating means in the camera body unit. 
     As described above, according to the second embodiment, even if a zoom operating means such as a zoom ring is provided therein, a zooming operation is controlled in accordance with the corresponding first operating information and the zoom position information and the zooming inhibition information. At that time, a zooming operation is controlled by the camera body unit according to the first operating information, the zoom position information and second zoom operating information produced by a zooming operation of the camera body unit. Thus, even if the zoom operating means are provided in both the lens unit and the camera body unit, respectively, the camera smoothly performs suitable zooming control operations. 
     Furthermore, according to the second embodiment, the first operating information and the zoom position information are generated by a zooming operation of the lens unit and inputted to the camera body unit. Thus, an electronic zooming operation is performed according to such inputted information and second zoom operating information produced by the camera body unit. Moreover, the second zoom operating information and the optical zooming control information are generated and sent to the lens unit. Thus, even if the zoom operating means are provided in both the lens unit and the camera body unit, respectively, the camera smoothly performs suitable zooming control operations. 
     Third Embodiment 
     Video cameras having both the optical zooming function and the electronic zooming function, similarly as the first and second embodiments, have the problem that it is difficult to smoothly switch between the optical zooming function and the electronic zooming function. Hereinafter, this problem will be described by taking the conventional video camera shown in  FIG. 4  as an example. 
       FIG. 13  shows the configuration of the enlargement processing circuit  205  of the conventional video camera illustrated in  FIG. 4 . For simplicity of description, this figure illustrates only vertical enlargement processing. 
     As shown in  FIG. 13 , an input video signal  300  is stored in a memory circuit  301  under the control of a memory control signal generating circuit  302  and sent to an output switch circuit  309 . Microcomputer interface circuit  304  receives an enlargement magnification and enlargement information from a camera microcomputer  208 . Based on this, an enlarged magnification determining circuit  303  outputs the enlargement magnification to the memory control signal generating circuit  302  and an interpolation coefficient generating circuit  308 . The memory control signal generating circuit  302  reads signals, which respectively represent an nth line and an (n−1)th line delayed by 1 H from the nth line, from the memory circuit  301 . The interpolation coefficient generating circuit  308  generates interpolation coefficients corresponding to the enlargement magnification and gives the generated interpolation coefficients to multipliers  305  and  306 . These multipliers multiply the signals, which respectively represent an nth line and an (n−1)th line, by the interpolation coefficients. Outputs of these multipliers are added up in an adder  307 . Resultant signal is outputted therefrom to the output switch circuit  309 . Then, the output switch circuit  309  outputs the signal sent from the adder  307  or the input video signal  300  according to a switch signal sent from the microcomputer interface circuit  304  as an output video signal  310 . 
     However, in the conventional circuit, it is difficult to set the timing of the switching between optical zooming, which is performed in the interchangeable lens unit, and enlargement processing which is performed by utilizing the electronic zooming in the camera body unit. Moreover, for some reason, the conventional circuit has no means (for example, a process sequence) for discontinuing the enlargement processing in the camera body unit (for instance, in the case that the interchangeable lens unit has a zoom ring for mechanically moving the variator lens and that a gear has a slip mechanism for transmitting the movement of the zoom ring to the rotation shaft, a cameraman operates the zoom ring in a direction corresponding to the wide side). 
     Thus, in Japanese Unexamined Patent Publication No. 9-96756 Official Gazette, the inventors of the present invention have proposed devices to solve the aforementioned problem. Consequently, smooth switching between optical and electronic zooming operations is achieved. However, troubles, such as suspension of a zooming operation, may happen in the cases that a delay occurs in transmission of an electronic zooming inhibition or permission signal between the lens unit and the camera body unit due to some cause and that, after an electronic zooming enabling signal is received by the camera body unit, a delay occurs therein until electronic zooming is performed therein. 
     Hereinafter, this phenomenon will be described in detail. 
       FIG. 14  is a diagram illustrating the timing with which an output video signal is changed from video signals of an optical zooming region to those of an electronic zooming region when a zooming operation is performed from the wide side to the tele side. In this diagram, the transverse axis represents time. As viewed in this diagram, the righter the position of a time point on the transverse axis becomes, the later time the time point indicates. 
     In  FIG. 14 , reference numeral  801  denotes a row representing a sequence of fields of a standard television signal. Fields (n−1) to (n+4) are shown in this figure. Reference numeral  802  designates a row showing various kinds of processing to be performed by the camera microcomputer  208  in the respective fields. The aforementioned kinds of processing illustrated in  FIG. 7  are performed in the respective fields. Reference numeral  803  designates a row showing the field Nos. of fields in which the input video signals  300  are obtained by photoelectric conversion. Incidentally, a field, in which a video signal is read from an imager  201 , is just subsequent to a field in which this video signal is obtained by photoelectric conversion. Thus, the field No. of this field is smaller than the field No. thereof shown in the row  801  by 1. 
     Reference numeral  804  designates a row showing the field No. of a field in which an output signal of the adder  307  is obtained in the imager  201  by photoelectric conversion. However, an output signal of the adder  307  is indefinite until a video signal is fetched in the memory circuit  301 . After a video signal is fetched thereto, a signal delayed by 1 field is outputted from the adder  307 . Reference numeral  805  denotes a row indicating which of the input video signal  300  and the output signal of the adder  307  is selected by the output switch circuit  309  according to a switch signal outputted from the microcomputer interface circuit  304  shown in  FIG. 13 . Reference numeral  806  designates a row indicating the field No. of a field in which the output video signal  310  is obtained in the imager  201  by photoelectric conversion. 
     Next, a process flow of the zooming processing will be described by concentrating on the processing to be performed by the camera microcomputer  208 . 
     During the zooming operation from the wide side to the tele side, the lens microcomputer  115  prepares electronic zooming permission information for the next communication with the camera microcomputer  208  in the field n when the optical zoom lens reaches the optical tele end at the time t(n)  1 . 
     In the field (n+1), an electronic zooming enabling signal is sent from the lens microcomputer  115  to the camera microcomputer  208  by the communication performed at the time t(n) 1 . In the zooming processing at the time t(n+1) 2 , the camera microcomputer  208  performs an operation for causing the memory circuit  301  to store the input video signal in the time (n+2). 
     In the field (n+2), an operation for causing the input video signal  300  obtained in the field (n+3) to be stored in the memory circuit  301  is performed. Moreover, operations of enlarging an image, which is represented by the stored input video signal  300  in the field (n+2), in the field (n+3), and of outputting a video signal (n+1)′ representing an enlarged image, and of selecting a received output of the adder  307  as an output of the output switch circuit  309 . 
     In the field (n+3), an operation of storing the input video signal  300 , which is obtained in the field (n+4), in the memory circuit  301  is performed during the zooming processing at the time t(n+3). Further, the circuit performs operations of enlarging an image, which is represented by the stored input video signal  300  in the field (n+2), in the field (n+3), and of outputting a video signal (n+1)′ representing an enlarged image, and of selecting a received output of the adder  307  as an output of the output switch circuit  309 . Further, the circuit performs operations of enlarging an image, which is represented by the stored input video signal  300  in the field (n+3), in the field (n+4), and of outputting a video signal (n+1) 1  representing an enlarged image, and of outputting a video signal (n+2)′ to the output switch circuit  309 . In and after the field (n+4), the same processing as performed in the field (n+3) is carried out. 
     Next, change  806  in the output video signal  310  with time will be described. Because the zoom lens reaches the optical tele end in the field “n”, signals obtained in the imager  201  by photoelectric conversion in the fields up to (n−1) and signals obtained by photoelectric conversion in the field “n”, in which the optical zooming is ceased in the middle thereof, are video signals obtained during the optical zooming. Thus, the output video signals outputted in the fields up to (n+1) are signals outputted during the optical zooming. Signals obtained in the field (n+1) by photoelectric conversion are outputted without change as the output video signal  310  in the field (n+2), and thus are neither signals obtained during the optical zooming, nor signals obtained during the electronic zooming. The output video signals  310  outputted in the field (n+3) and the subsequent fields are obtained by enlarging signals stored in the memory circuit  301  and are video signals obtained during the electronic zooming. 
     As is understood from the foregoing description, the zooming is suspended in the case that a time lag occurs between the reception of the electronic zooming enabling signal and the implementing of the electronic zooming in the camera body unit. 
     This third embodiment aims at solving the aforementioned problem and at achieving the smooth switching between the optical zooming and the electronic zooming. 
     Hereinafter, the third embodiment will be described with reference to the accompanying drawings. 
     A lens-interchangeable video camera used in the third embodiment is constructed in such a manner as to be similar to the video camera used in the first embodiment illustrated in  FIG. 4 . The video camera of the second embodiment is different from that of  FIG. 4  only in that the video camera of this embodiment has storage media  117  and  214  as illustrated in  FIG. 15 . Further, the flow of the processing to be performed by the camera microcomputer  208  is broadly similar to the flow illustrated in  FIGS. 7 and 8 . 
     Further, the storage medium  117  stores a program for performing a process illustrated in a flowchart of  FIG. 16 , which is executed by the lens microcomputer  115 . Moreover, the storage medium  117  stores a program for performing processes illustrated in flowcharts of  FIGS. 17 ,  7  and  8 , which are executed by the camera microcomputer  208 . Semiconductor memories, optical disks, magneto-optic disks or magnetic media may be used as these storage media  117  and  214 . 
     First, step  406  of a process flow (see  FIG. 7 ) by the camera microcomputer  208  of the third embodiment of the present invention will be described in detail with reference to  FIG. 17 . Incidentally, in the following description, it is assumed that only the zoom switches  210  and  211  move the variator lens group  102 . 
     As shown in  FIG. 17 , in step  1201 , the processing is started. Then, in step  1202 , the camera microcomputer  208  checks whether a zooming operation is being performed. Subsequently, if both the zoom switches  210  and  211  are pushed, or if neither of these zoom switches is pushed, control advances to step  1207 . If only one of these zoom switches is pushed, control proceeds to step  1203  whereupon the camera microcomputer  208  further checks which of the switches  210  and  211  is pushed. If the “TELE” switch  210  is pushed, control advances to step  1204 . If the “WIDE” switch  211  is pushed, control proceeds to step  1208 . 
     In step  1204 , the camera microcomputer  208  judges whether electronic zooming permission information comes thereto from the lens microcomputer  115 . If electronic zooming is permitted, control advances to step  1205 . Otherwise, control proceeds to step  1210 . In step  1205 , the camera microcomputer  208  checks whether the zoom lens group is positioned at the optical tele end. If so, control advances to step  1207 . Otherwise, control proceeds to step  1206  whereupon an electronic zooming operation is performed by increasing or decreasing the aforementioned interpolation coefficients according to which of the switches  210  and  211  is pushed. Moreover, the camera microcomputer  208  controls the enlargement processing circuit  205  according to a result of the electronic zooming operation. Then, in step  1207 , the camera microcomputer  208  sends a zoom lens stop request signal to the lens microcomputer  115 . 
     On the other hand, in step  1208 , the camera microcomputer  208  checks whether an electronic zooming operation is currently being performed. If so, control advances to step  1206 . Otherwise, in step  1209 , the camera microcomputer  208  sends the lens microcomputer  115  a request signal for moving the zoom lens group in a direction corresponding to the wide side. 
     Further, in step  1210 , the camera microcomputer  208  checks whether an electronic zooming preparation permission signal comes thereto from the lens microcomputer  115 . If permitted, control advances to step  1211 . Otherwise, control proceeds to step  1212 . In step  1211 , the camera microcomputer  208  makes preparations for starting the electronic zooming. Then, control advances to step  1212 . Input image signal  300  is stored in the memory circuit  301  so that, owing to the preparations made in step  1211 , an electronic zooming operation can be performed immediately after an electronic zooming permission signal comes from the lens microcomputer  115 . In step  1212 , the camera microcomputer  208  sends the lens microcomputer  115  a request signal to be used for moving the zoom lens group to the tele side. Upon completion of the operation to be performed in one of the aforementioned steps  1207 ,  1212  and  1209 , control returns to the main routine in step  1213 . 
     Next, processing to be performed by the lens microcomputer  115  of the third embodiment will be described. 
       FIG. 16  is a flowchart illustrating processing concerning a zooming operation, which is a part of the entire processing to be performed by the lens microcomputer  115 . Incidentally, a manual zooming operation will be described hereunder by way of example. In step  1301 , the processing is started. Then, in step  1302 , the lens microcomputer  115  checks whether the zoom stop request signal comes thereto from the camera microcomputer  208 . If the zoom stop request signal has already come thereto, control proceeds to step  1308 . Otherwise, control advances to step  1303  whereupon the lens microcomputer  115  checks from the information sent from the camera microcomputer  208  which of the tele direction and the wide direction the moving direction of the zoom lens group is. If the tele direction, control proceeds to step  1304 . Conversely, if the wide direction, control advances to step  1305 . 
     In step  1304 , the lens microcomputer  115  checks whether the zoom lens group is positioned at the tele end. If so, control proceeds to step  1308 . Otherwise, control advances to step  1306 . Further, the moving speed of the zoom lens group and the moving speed and direction of the focusing lens group are calculated in step  1306 . According to a result of this calculation, the zoom lens group and the focusing lens group are driven in step  1307 . Furthermore, in step  1308 , the zoom lens group is stopped. 
     Upon completion of the operation performed in step  1307  or  1308 , the lens microcomputer  115  checks in step  1309  whether the zoom lens group is placed at the tele end. If so, control proceeds to step  1310 . Otherwise, control advances to step  1311 . In step  1310 , the lens microcomputer  115  sets information to be used for sending an electronic zooming permission signal to the camera microcomputer  208 . Furthermore, in step  1311 , the lens microcomputer  115  sets information to be used for sending an electronic zooming inhibition signal to the camera microcomputer  208 . Then, control advances to step  1312 . 
     In this step  1312 , the lens microcomputer  115  checks whether the zoom lens group is moving to the wide side. If so, control proceeds to step  1313 . Otherwise, control advances to step  1315 . In step  1313 , the lens microcomputer  115  checks whether a current focal length f of the zoom lens group is not less than a focal length fn at which the zoom lens group would reach the tele end within ( 1/60) seconds if the zoom lens group moved by maintaining a current zooming speed. If not less than fn, control proceeds to step  1314 . Otherwise, control advances to step  1315 . In step  1314 , the lens microcomputer  115  sets information for sending an electronic zooming permission signal to the camera microcomputer  208 . Furthermore, in step  1315 , the lens microcomputer  115  sets information for sending an electronic zooming inhibition signal to the camera microcomputer  208 . Upon completion of the operation to be performed in one of the aforementioned steps  1310 ,  1314  and  1315 , control returns to the main routine in step  1316 . 
     Next, the case of integrating the processing performed by the lens microcomputer  115  with the processing performed by the camera microcomputer  208  will be described. 
       FIG. 18  is a diagram illustrating the timing with which an output video signal is changed from video signals of an optical zooming region to those of an electronic zooming region when a zooming operation is performed from the wide side to the tele side. In this diagram, the transverse axis represents time. As viewed in this diagram, the righter the position of a time point on the transverse axis becomes, the later time the time point indicates. Reference numeral  1101  denotes a row representing a sequence of fields of a standard television signal. Fields (n−1) to (n+4) are shown in this figure. Reference numeral  1102  designates a row showing various kinds of processing to be performed by the camera microcomputer  208  in the respective fields. The aforementioned kinds of processing illustrated in  FIG. 7  are performed in the respective fields. 
     Reference numeral  1103  designates a row showing the field Nos. of fields in which the input video signals  300  are obtained in the imager  201  by photoelectric conversion. Incidentally, a field, in which a video signal is read from the imager  201 , is immediately subsequent to a field in which this video signal is obtained by photoelectric conversion. Thus, the field No. of this field is smaller than the field No. thereof shown in the row  1101  by 1. Reference numeral  1104  designates a row showing the field No. of a field in which an output signal of the adder  307  is obtained in the imager  201  by photoelectric conversion. However, an output signal of the adder  307  is indefinite until a video signal is fetched in the memory circuit  301 . After Aa video signal is fetched thereto, a signal delayed by 1 field is outputted from the adder  307 . 
     Reference numeral  1105  denotes a row indicating which of the input video signal  300  and the output signal of the adder  307  is selected by the output switch circuit  309  according to a switch signal outputted from the microcomputer interface circuit  304 . Reference numeral  1106  designates a row indicating the field No. of a field in which the output video signal  310  is obtained in the imager  201  by photoelectric conversion. 
     Next, a process flow of the zooming processing will be described by concentrating on the processing to be performed by the camera microcomputer  208 . 
     In the zooming operation from the wide side to the tele side, the lens microcomputer  115  detects at the time t(n−1) 1  that the current focal length f of the zoom lens group is not less than the focal length fn at which the zoom lens group would reach the tele end within ( 1/60) seconds if the zoom lens group moved by maintaining the current zooming speed. Then, the lens microcomputer  115  prepares electronic zooming permission information for the next communication with the camera microcomputer  208  in the field n if the optical zoom lens reaches the optical tele end at the time t(n) 1 . 
     In the field “n”, an electronic zooming enabling signal is sent from the lens microcomputer  115  to the camera microcomputer  208  by the communication performed at the time t(n)  1 . In the zooming processing at the time t(n) 2 , the camera microcomputer  208  performs an operation for causing the memory circuit  301  to store the input video signal  300  in the time (n+1). In the field (n+1), an operation for causing the input video signal  300  obtained in the field (n+3) to be stored in the memory circuit  301  is performed. Moreover, if the optical zoom lens group reaches the optical tele end at the time t(n) 3 , the lens microcomputer  115  prepares electronic zooming permission information for the next communication with the camera microcomputer  208 . 
     In the field “n”, an electronic zooming preparation permission signal is sent from the lens microcomputer  115  to the camera microcomputer  208  by the communication performed at the time t(n+1) 1 . In the zooming processing at the time t(n+1) 2 , the camera microcomputer  208  performs an operation for causing the memory circuit  301  to store the input video signal  300  in the time (n+1), and also performs operations of enlarging an image, which is represented by the stored input video signal  300  in the field (n+2), and of outputting a video signal (n+1)′ representing an enlarged image to the output switch circuit  309 , and of selecting a received output of the adder  307  as an output of the output switch circuit  309 . 
     In the field (n+2), an operation of storing the input video signal  300 , which is obtained in the field (n+3), in the memory circuit  301  is performed during the zooming processing at the time t(n+2) 1 . Further, the circuit performs operations of enlarging an image, which is represented by the stored input video signal  300  in the field (n+2), in the field (n+3), and of outputting a video signal (n+1) 1  representing an enlarged image, and of selecting a received output of the adder  307  as an output of the output switch circuit  309 . Further, the circuit performs operations of enlarging an image, which is represented by the stored input video signal  300  in the field (n+3), in the field (n+4), and of outputting a video signal (n+1)′ to the output switch circuit  309 . In the field (n+3) and the subsequent fields, the same processing as performed in the field (n+2) is carried out. 
     Next, change  1106  in the output video signal  310  with time will be described. Because the zoom lens reaches the optical tele end in the field “n”, signals obtained in the imager  201  by photoelectric conversion in the fields up to (n−1) and signals obtained by photoelectric conversion in the field “n”, in which the optical zooming is ceased in the middle thereof, are video signals obtained during the optical zooming. Thus, the output video signals outputted in the fields up to (n+1) are signals outputted during the optical zooming. Each of the output video signals  310  outputted in the field (n+2) and the subsequent fields are obtained by enlarging the signal stored in the memory circuit  301  in the immediately precedent field and are video signals obtained during the electronic zooming. 
     Incidentally, in the aforementioned third embodiment, the lens microcomputer  115  is adapted to detect that the current focal length f of the zoom lens group is not less than the focal length fn at which the zoom lens group would reach the tele end within ( 1/60) seconds if the zoom lens group moved by maintaining the current zooming speed. Further, the lens microcomputer  115  is adapted to prepare electronic zooming permission information for the next communication with the camera microcomputer  208 . However, even in the case that a large time delay is caused in the timing of obtaining electronic zooming permission information from the lens microcomputer  115  by the camera microcomputer  208  for some reason after the zoom lens group reaches the optical tele end, smooth switching between optical and electronic zooming operations is realized by setting fn, which meets the aforementioned inequality f&lt;fn where f is the focal length of the zoom lens group, in such a manner that the zoom lens group would reach the optical tele end within a time period, which is an integral multiple of the cycle of the communication between the lens microcomputer  115  and the camera microcomputer  208  corresponding to the aforementioned time delay, if the zoom lens group moved by maintaining the current zooming speed. 
     As described above, according to the third embodiment, an electronic zooming preparation permission signal and an electronic zooming enabling signal are outputted to the camera body unit during the zooming operation. Thus, even in the case that there is a delay in performing electronic zooming, a zooming operation is smoothly performed without suspension. 
     Further, according to the third embodiment, electronic zooming is enabled when the aforementioned signals are inputted from the lens unit. Consequently, even in the case that a delay occurs in performing electronic zooming, a zooming operation is smoothly performed without suspension. 
     Fourth Embodiment 
     In the case that the interchangeable lens unit  100  has an electrically-controllable optical zooming mechanism, similarly as in the case of the first to third embodiment, optical zooming and electronic zooming are achieved under the control of the camera microcomputer  208 . However, in the case that, as shown in  FIGS. 16 and 17 , the lens units  130  and  140  have no electrically-controllable optical zooming mechanisms, the control of electronic zooming is not taken into consideration. 
     This fourth embodiment is enabled to smoothly function an electronic zooming mechanism of the camera body unit according to the type of an external lens unit (for instance, an interchangeable lens unit), regardless of the presence/absence of an electrically controllable optical zooming mechanism in the external lens unit. 
     Hereinafter, the fourth embodiment will be described. 
     Video camera of the fourth embodiment has a camera body unit whose hardware configuration is the same as that of the body unit  200  shown in  FIG. 4 . This camera body unit  200  is combined with an interchangeable lens unit that has the same hardware configuration as that of the interchangeable lens unit shown in  FIG. 19 ,  20  or  4 . Incidentally, the fourth embodiment is different in software used in the camera microcomputer  208  and the lens microcomputer  115  from the conventional video camera. Hereinafter, only the differences therebetween will be described. 
     The flow of the processing to be performed by the camera microcomputer  208  is broadly similar to the flow illustrated in  FIGS. 7 and 8 .  FIG. 21  shows a process flow of step  406  of this embodiment, which is illustrated in  FIG. 7 . 
     In step S 1401 , the processing is started. Then, in step S 1402 , the camera microcomputer  208  checks whether the zoom keys  210  and  211  of the camera body unit  200  are not operated or whether each of these zoom keys is operated in the tele or wide direction. If the zoom keys are operated, control advances to step S 1403 . If not operated, control proceeds to step S 1414 . In step S 1403 , the camera microcomputer  208  checks manual zooming capability information sent from the lens microcomputer  115 . If manual zooming is possible, control advances to step S 1414 . Otherwise, control proceeds to step S 1404  whereupon the camera microcomputer  208  checks presence-of-zooming-unit information sent from the lens microcomputer of the interchangeable lens unit. If the lens unit has a zooming unit, control advances to step S 1405 . Otherwise, control unit proceeds to step S 1410 . In step S 1405 , the camera microcomputer  208  checks whether the zoom keys  210  and  211  of the camera body unit  200  are operated in a direction corresponding to the tele side. If the zoom keys are operated in a direction corresponding to the tele side, control advances to step S 1406 . If the zoom keys are operated in a direction corresponding to the wide side, control proceeds to step S 1409 . In step S 1406 , the camera microcomputer  208  checks optical tele end information sent from the lens microcomputer of the interchangeable lens unit. If this information indicates the optical tele end, control advances to step S 1407 . Otherwise, control proceeds to step S 1413 . In step S 1407 , the camera microcomputer  208  checks whether the zooming unit is at the tele end in the case of electronic zooming. If so, control advances to step S 1414 . Otherwise, control proceeds to step S 1408 . In step S 1414 , the camera microcomputer  208  checks whether an electronic zooming operation is currently being performed. If so, control advances to step S 1408 . Otherwise, control proceeds to step S 1415 . In step S 1408 , an electronic zooming operation is performed by increasing or decreasing the aforementioned interpolation coefficients according to which of the switches  210  and  211  is pushed. Moreover, the camera microcomputer  208  controls the enlargement processing circuit  205  according to a result of the electronic zooming operation. Then, control advances to step S 1414 . 
     On the other hand, in step S 1410 , the camera microcomputer  208  checks whether each of the zoom keys  210  and  211  of the camera body unit  200  is operated in a direction corresponding to the tele or wide direction. If operated in the direction corresponding to the tele side, control proceeds to, step S 1411 . Conversely, if operated in the direction corresponding to the wide side, control advances to step S 1412 . In step S 1411 , the camera microcomputer  208  checks whether the zooming unit is at the tele end in the case of electronic zooming. If so, control advances to step S 1414 . Otherwise, control proceeds to step S 1408 . In step S 1412 , the camera microcomputer  208  checks whether an electronic zooming operation is currently being performed. If so, control advances to step S 1408 . Otherwise, control proceeds to step S 1414 . 
     In step S 1413 , the camera microcomputer  208  sets a control signal for moving the zoom lens to the tele side. In step S 1414 , the camera microcomputer  208  sets a control signal for stopping the zoom lens. In step S 1415 , the camera microcomputer  208  sets a control signal for moving the zoom lens to the wide side. 
     Upon completion of the operation performed in one of the aforementioned steps S 1413 , S 1414  and S 1415 , control returns to an upper-level routine in step S 1416 . 
     Next, the video camera having the combination of the camera body unit  200  of the hardware configuration shown in  FIG. 4  and the interchangeable lens unit  130  of the hardware configuration shown in  FIG. 19  will be first described below. 
     As shown in  FIG. 19 , reference numeral  130  designates an interchangeable lens unit detachably attached to a camera body unit  200 . In the interchangeable lens unit  130 , reference numeral  131  denotes a focusing lens group for performing a focusing function; and  132  a variator lens group for changing a magnification, which consists of a variator lens and a compensator lens and changes the position thereof in accordance with a cam (not shown) to thereby vary the focal length thereof. Reference numeral  133  designates a fixed image-forming lens group. These lens groups  131  to  133  constitute a lens system of what is called a front lens focusing type. 
     Reference numeral  134  denotes a zoom ring for manually moving the variator lens group  132  by a cameraman. A zooming operation is enabled only by using this zoom ring  134  (an optical zooming mechanism which does not operate according to a control signal inputted from an external device). Reference numeral  135  designates a stepping motor for moving the focusing lens group  131 ;  136  a zoom encoder;  137  a lens microcomputer which is operative to communicate with the microcomputer  208  of the camera body unit  200  and to control the stepping motor  135 . 
       FIG. 22  is a flowchart illustrating a part of processing to be performed by the lens microcomputer  137 . 
     In step S 1501 , the processing is started. Then, in step S 1502 , the lens microcomputer  137  sets presence-of-zooming-unit information and makes preparations for sending this information to the camera microcomputer  208 . Then, control advances to step S 1503  whereupon the lens microcomputer  137  sets manual zooming capability information and makes preparations for sending this information to the camera microcomputer  208 . Subsequently, control proceeds to step S 1504  whereupon it is judged by interruption processing whether the communication between the lens microcomputer  137  and the camera microcomputer  208  is completed. If completed, control advances to step S 1505 . Otherwise, control goes back to step S 1504 . In step S 1505 , the lens microcomputer  137  reads a value indicated by the zoom encoder  136 . Then, control proceeds to step S 1506  whereupon a driving amount of the focusing lens is calculated from the value indicated by the zoom encoder  136  and from an autofocusing estimation value provided by the camera body unit  200  (incidentally, the detailed description of this value is omitted for simplicity of description). Subsequently, control advances to step S 1507  whereupon the stepping motor for moving the focusing lens  131  is driven according to the driving amount of the focusing lens calculated in step S 1506 . Thereafter, control goes back to step S 1502 . 
     As is understood from the foregoing description, in the case of the combination of the camera body unit  200  and the interchangeable lens unit  130 , the manual zooming capability information (indicating the presence of the optical zooming mechanism which does not operate according to control information provided from an external device) is set (in step S 1503 ) by the lens microcomputer  137 . Thus, the camera microcomputer  208  judges (in step S 1403 ) that a manual zooming operation can be performed. Consequently, an electronic zooming mechanism (the enlargement processing circuit  205 ) provided in the camera body unit  200  does not function. 
     Next, the video camera having the combination of the camera body unit  200  of the hardware configuration shown in  FIG. 4  and the interchangeable lens unit  140  of the hardware configuration shown in  FIG. 20  will be described below. 
     As shown in  FIG. 20 , reference numeral  140  designates an interchangeable lens unit detachably attached to a camera body unit  200 . In the interchangeable lens unit  140 , reference numeral  141  denotes a focusing lens group constituting a short focus lens; and  142  a lens microcomputer which is operative to communicate with the microcomputer  208  of the camera body unit  200 . 
       FIG. 23  is a flowchart illustrating a part of processing to be performed by the lens microcomputer  142 . 
     In step S 1601 , the processing is started. Then, in step S 1602 , the lens microcomputer  142  clears presence-of-zooming-unit information and makes preparations for sending absence-of-zooming-unit information to the camera microcomputer  208 . Then, control advances to step S 1603  whereupon the lens microcomputer  142  sets manual zooming capability information and makes preparations for sending information, which indicates that manual zooming cannot be performed, to the camera microcomputer  208 . Subsequently, control proceeds to step S whereupon it is judged by interruption processing whether the communication between the lens microcomputer  142  and the camera microcomputer  208  is completed. If completed, control goes back to step S 1602 . Otherwise, control goes back to step S 1604 . 
     As is understood from the foregoing description, in the case of the combination of the camera body unit  200  and the interchangeable lens unit  140 , the manual zooming capability information (indicating the presence of the optical zooming mechanism) is cleared (in step S 1602 ) by the lens microcomputer  142 . Further, the manual zooming capability information is cleared (in step S 1603 ). Thus, the camera microcomputer  208  judges (in steps S 1403  and S 1404 ) that a manual zooming operation cannot be performed and no zooming unit is provided in the camera. Consequently, an electronic zooming mechanism (the enlargement processing circuit  205 ) provided in the camera body unit  200  functions. 
     Next, the video camera having the combination of the camera body unit  200  of the hardware configuration and the interchangeable lens unit  100  of the hardware configuration, which are shown in  FIG. 4 , will be described below. 
       FIG. 24  is a flowchart illustrating processing concerning a zooming operation, which is a part of the entire processing to be performed by the lens microcomputer  115 . In step S 1701 , the processing is started. Then, in step S 1702 , the lens microcomputer  115  checks whether a zoom lens stop request signal (S 1414 ) comes thereto from a camera microcomputer  208 . If the zoom lens group has already stopped, control proceeds to step S 1708 . Otherwise, control advances to step S 1703  whereupon the lens microcomputer  115  checks according to the information sent by the camera microcomputer  208  which of the tele direction and the wide direction the moving direction of the zoom lens group is. If the moving direction of the zoom lens group is the tele direction, control proceeds to step S 1704 . If the wide direction, control advances to step S 1705 . 
     In step S 1704 , the lens microcomputer  115  checks whether the zoom lens group is positioned at the tele end. If so, control proceeds to step S 1708 . Otherwise, control advances to step S 1706 . Further, in step S 1705 , the lens microcomputer  115  checks whether the zoom lens group is positioned at the wide end. If so, control proceeds to step S 1708 . Otherwise, control advances to step S 1706 . The moving speed of the zoom lens group and the moving speed and direction of the focusing lens group are calculated in step S 1706 . According to a result of this calculation, the zoom lens group and the focusing lens group are driven in step S 1707 . Furthermore, in step S 1708 , the zoom lens group is stopped. 
     Upon completion of the operation performed in step S 1707  or S 1708 , the lens microcomputer  115  checks in step S 1709  whether the zoom lens group is placed at the tele end. If so, control proceeds to step S 1710 . Otherwise, control advances to step S 1711 . In step S 1710 , the lens microcomputer  115  sets optical tele end information and makes preparations for sending this information to the camera microcomputer  208 . Further, in step S 1711 , the lens microcomputer  115  clears optical tele end information and makes preparations for sending information, which indicates that the zoom lens group is not placed at the tele end, to the camera microcomputer  208 . In step S 1712 , the lens microcomputer  115  sets presence-of-zooming-unit information and makes preparations for sending this information to the camera microcomputer  208 . Then, control proceeds to step S 1713  whereupon the lens microcomputer  115  clears manual zooming capability information and makes preparations for sending information, which indicates that manual zooming cannot be performed, to the camera microcomputer  208 . Subsequently, control advances to step S 1714 . Further, control returns to a main routine in step S 1714 . 
     As is understood from the foregoing description, in the case of the combination of the camera body unit  200  and the interchangeable lens unit  100 , the presence-of-zooming-unit information is set (in step S 1712 ) by the lens microcomputer  115 . Further, the manual zooming capability information is cleared (in step S 1713 ). Thus, the camera microcomputer  208  judges (in steps S 1403  and S 1404 ) that a manual zooming operation cannot be performed and a zooming unit is provided in the camera. Consequently, an electronic zooming mechanism provided in the camera body unit  200  functions. 
     Fifth Embodiment 
     A video camera of the fifth embodiment has a camera body unit of the same hardware configuration as the configuration of the unit  200  illustrated in  FIG. 4 , similarly as the fourth embodiment does. In the case of the fifth embodiment, such a camera body unit is combined with an interchangeable lens unit of the same hardware configuration as the configuration of the interchangeable lens unit shown in  FIG. 19 ,  20  or  4 . Incidentally, the fifth embodiment is different in software used in the camera microcomputer  208  and the lens microcomputer  115  from the conventional video camera and the fourth embodiment. Hereunder, only the differences therebetween will be described. 
     The flow of the processing to be performed by the camera microcomputer  208  of this embodiment is broadly similar to the flow illustrated in  FIGS. 7 and 8 .  FIG. 25  shows a process flow of step  406  of this embodiment, which is illustrated in  FIG. 7 . 
     In step S 1801 , the processing is started. Then, in step S 1802 , the camera microcomputer  208  checks whether the zoom keys  210  and  211  of the camera body unit  200  are not operated or whether each of these zoom keys is operated in the tele or wide direction. If the zoom keys are operated, control advances to step S 1803 . If not operated, control proceeds to step S 1814 . In step S 1803 , the camera microcomputer  208  checks specific lens group information sent from the lens microcomputer of the interchangeable lens unit. If the interchangeable lens unit belongs to the specific lens group, control advances to step S 1414 . Otherwise, control proceeds to step S 1804  whereupon the camera microcomputer  208  checks presence-of-zooming-unit information sent from the lens microcomputer of the interchangeable lens unit. If the lens unit has a zooming unit, control advances to step S 1805 . Otherwise, control unit proceeds to step S 1810 . In step S 1805 , the camera microcomputer  208  checks whether the zoom keys  210  and  211  of the camera body unit  200  are operated in a direction corresponding to the tele side. If the zoom keys are operated in a direction corresponding to the tele side, control advances to step S 1806 . If the zoom keys are operated in a direction corresponding to the wide side, control proceeds to step S 1809 . In step S 1806 , the camera microcomputer  208  checks optical tele end information sent from the lens microcomputer of the interchangeable lens unit. If this information indicates the optical tele end, control advances to step S 1807 . Otherwise, control proceeds to step S 1813 . In step S 1807 , the camera microcomputer  208  checks whether the zooming unit is at the tele end in the case of electronic zooming. If so, control advances to step S 1814 . Otherwise, control proceeds to step S 1808 . In step S 1809 , the camera microcomputer  208  checks whether an electronic zooming operation is currently being performed. If so, control advances to step S 1808 . Otherwise, control proceeds to step S 1815 . In step S 1808 , an electronic zooming operation is performed by increasing or decreasing the aforementioned interpolation coefficients according to which of the switches  210  and  211  is pushed. Moreover, the camera microcomputer  208  controls the enlargement processing circuit  205  according to a result of the electronic zooming operation. Then, control advances to step S 1814 . 
     On the other hand, in step S 1810 , the camera microcomputer  208  checks whether each of the zoom keys  210  and  211  of the camera body unit  200  is operated in a direction corresponding to the tele or wide direction. If operated in the direction corresponding to the tele side, control proceeds to step S 1811 . Conversely, if operated in the direction corresponding to the wide side, control advances to step S 1812 . In step S 1811 , the camera microcomputer  208  checks whether the zooming unit is at the tele end in the case of electronic zooming. If so, control advances to step S 1814 . Otherwise, control proceeds to step S 1808 . In step S 1812 , the camera microcomputer  208  checks whether an electronic zooming operation is currently being performed. If so, control advances to step S 1808 . Otherwise, control proceeds to step S 1814 . 
     In step S 1813 , the camera microcomputer  208  sets a control signal for moving the zoom lens group to the, tele side. In step S 1814 , the camera microcomputer  208  sets a control signal for stopping the zoom lens. In step S 11815 , the camera microcomputer  208  sets a control signal for moving the zoom lens to the wide side. 
     Upon completion of the operation performed in one of the aforementioned steps S 1813 , S 1814  and S 1815 , control returns to an upper-level routine in step S 1816 . 
     Next, the video camera having the combination of the camera body unit  200  of the hardware configuration shown in  FIG. 4  and the interchangeable lens unit  130  of the hardware configuration shown in  FIG. 19  will be first described below. It is assumed that the interchangeable lens unit  130  has a manual zooming mechanism which cannot be controlled by using a control signal inputted from an external device, and that the lens unit  130  belongs to the “specific lens group”. 
       FIG. 26  is a flowchart illustrating a part of processing to be performed by the lens microcomputer  137 . 
     In step S 1901 , the processing is started. Then, in step S 1902 , the lens microcomputer  137  sets presence-of-zooming-unit information and makes preparations for sending this information to the camera microcomputer  208 . Then, control advances to step S 1903  whereupon the lens microcomputer  137  sets specific lens group information and makes preparations for sending this information to the camera microcomputer  208 . Subsequently, control proceeds to step S 1904  whereupon it is judged by interruption processing whether the communication between the lens microcomputer  137  and the camera microcomputer  208  is completed. If completed, control advances to step S 1905 . Otherwise, control goes back to step S 1904 . In step S 1905 , the lens microcomputer  137  reads a value indicated by the zoom encoder  136 . Then, control proceeds to step S 1906  whereupon a driving amount of the focusing lens is calculated from the value indicated by the zoom encoder  136  and from an autofocusing estimation value provided by the camera body unit  200  (incidentally, the detailed description of this value is omitted for simplicity of description). Subsequently, control advances to step S 1907  whereupon the stepping motor for moving the focusing lens  131  is driven according to the driving amount of the focusing lens calculated in step S 1906 . Thereafter, control goes back to step S 1902 . 
     As is understood from the foregoing description, in the case of the combination of the camera body unit  200  and the interchangeable lens unit  130 , the specific lens group information (indicating that the lens unit has an optical zooming mechanism which does not operate according to control information provided from an external device) is set (in step S 1903 ) by the lens microcomputer  137 . Thus, the camera microcomputer  208  judges (in step S 1903 ) that the lens unit is a specific lens group. Consequently, an electronic zooming mechanism (the enlargement processing circuit  205 ) provided in the camera body unit  200  does not function. 
     Next, the video camera having the combination of the camera body unit  200  of the hardware configuration shown in  FIG. 4  and the interchangeable lens unit  140  of the hardware configuration shown in  FIG. 20  will be described below. Incidentally, it is assumed that the interchangeable lens unit  140  does not have a zooming mechanism and thus does not belong to the “specific lens group”. 
       FIG. 27  is a flowchart illustrating a part of processing to be performed by the lens microcomputer  142 . 
     In step S 2001 , the processing is started. Then, in step S 2002 , the lens microcomputer  142  clears presence-of-zooming-unit information and makes preparations for sending absence-of-zooming-unit information to the camera microcomputer  208 . Then, control advances to step S 2003  whereupon the lens microcomputer  142  clears specific lens group information and makes preparations for sending information, which indicates that the lens unit does not belong to the specific lens group, to the camera microcomputer  208 . Subsequently, control proceeds to step S 2004  whereupon it is judged by interruption processing whether the communication between the lens microcomputer  142  and the camera microcomputer  208  is completed. If completed, control goes back to step S 2002 . Otherwise, control goes back to step S 2004 . 
     As is understood from the foregoing description, in the case of the combination of the camera body unit  200  and the interchangeable lens unit  140 , the absence-of-zooming-unit information is set by the lens microcomputer  142 . Further, the specific lens group information is cleared (in steps S 2002  and S 2003 ). Thus, the camera microcomputer  208  judges (in steps S 1803  and S 1804 ) that the lens unit is not a specific lens group and no zooming unit is provided in the camera. Consequently, an electronic zooming mechanism (the enlargement processing circuit  205 ) provided in the camera body unit  200  functions. 
     Next, the video camera having the combination of the camera body unit  200  of the hardware configuration and the interchangeable lens unit  100  of the hardware configuration, which are shown in  FIG. 4 , will be described below. Incidentally, it is assumed that the interchangeable lens unit  100  does not have a manual zooming mechanism which cannot be controlled by a control signal inputted from an external device and that the lens unit  100  does not the “specific lens group”. 
       FIG. 28  is a flowchart illustrating processing concerning a zooming operation, which is a part of the entire processing to be performed by the lens microcomputer  115 . In step S 2101 , the processing is started. Then, in step S 2102 , the lens microcomputer  115  checks whether the zoom lens stop request signal comes thereto from a camera microcomputer  208 . If the zoom lens group has already stopped, control proceeds to step S 2108 . Otherwise, control advances to step S 2103  whereupon the lens microcomputer  115  checks according to the information sent by the camera microcomputer  208  which of the tele direction and the wide direction the moving direction of the zoom lens group is. If the moving direction of the zoom lens group is the tele direction, control proceeds to step S 2104 . If the wide direction, control advances to step S 2105 . 
     In step S 2104 , the lens microcomputer  115  checks whether the zoom lens group is positioned at the tele end. If so, control proceeds to step S 2108 . Otherwise, control advances to step S 2106 . Further, in step S 2105 , the lens microcomputer  115  checks whether the zoom lens group is positioned at the wide end. If so, control proceeds to step S 2108 . Otherwise, control advances to step S 2106 . The moving speed of the zoom lens group and the moving speed and direction of the focusing lens group are calculated in step S 2106 . According to a result of this calculation, the zoom lens group and the focusing lens group are driven in step S 2107 . Furthermore, in step S 2108 , the zoom lens group is stopped. 
     Upon completion of the operation performed in step S 2107  or S 2108 , the lens microcomputer  115  checks in step S 2109  whether the zoom lens group is placed at the tele end. If so, control proceeds to step S 2110 . Otherwise, control advances to step S 2111 . In step S 2110 , the lens microcomputer  115  sets optical tele end information and makes preparations for sending this information to the camera microcomputer  208 . Further, in step S 2111 , the lens microcomputer  115  clears optical tele end information and makes preparations for sending information, which indicates that the zoom lens group is not placed at the tele end, to the camera microcomputer  208 . In step S 2112 , the lens microcomputer  115  sets presence-of-zooming-unit information and makes preparations for sending this information to the camera microcomputer  208 . Then, control proceeds to step S 2113  whereupon the lens microcomputer  115  clears specific lens group information and makes preparations for sending information, which indicates that the lens unit does not belong to the specific lens group, to the camera microcomputer  208 . Subsequently, control advances to step S 2114 . Further, control returns to a main routine in step S 2114 . 
     As is understood from the foregoing description, in the case of the combination of the camera body unit  200  and the interchangeable lens unit  100 , the presence-of-zooming-unit information is set (in step S 2112 ) by the lens microcomputer  115 . Further, the specific lens group information is cleared (in step S 2113 ). Thus, the camera microcomputer  208  judges (in steps S 1803  and S 1804 ) that the lens unit is not a specific lens group and a zooming unit is provided in the camera. Consequently, an electronic zooming mechanism provided in the camera body unit  200  functions. 
     Incidentally, in the foregoing description of the fourth and fifth embodiments, it has been described that these embodiments are adapted to detect the zoom operating direction (namely, detect that the zoom lens group is operated toward the tele side or toward the wide side). However, the present invention is easily applied to a case that the camera has multi-zooming-speed in each zoom operating direction. 
     Further, even in the case that the camera body unit has a plurality of zoom operating means or that an external input device, such as a remote control device, for a camera body unit has zoom lens operating means, the present invention is easily applied to such a case by handling these means as a single zoom operating means in the camera body unit. 
     Moreover, in the foregoing description of the fifth embodiment, the specific lens group has been defined as a lens group having an optical lens group that cannot be controlled by a control signal inputted from an external device. However, it is apparent that other requirements, such as performance, price and use of the interchangeable lens unit, may be employed as the requirements for the specific lens group. Any of such requirements may be applied to the processing performed in the camera body unit, in view of consistency between such a requirement and the performance of or the manner of use of the electronic zooming function. 
     As described above, according to the fourth and fifth embodiments, an electronic zooming mechanism of the camera body unit smoothly functions according to the type of an external lens unit (for instance, an interchangeable lens unit), regardless of the presence/absence of an electrically controllable optical zooming mechanism in the external lens unit. 
     As many apparently widely different embodiments of the present invention can be made without departing from-the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the claims.