BACKGROUND OF THE INVENTION  
         [0001]    1. FIELD OF THE INVENTION  
           [0002]    The present invention relates to a lens apparatus for use in a video camera lens, a video camera, a television camera lens or a television camera, and to an image-taking apparatus having the lens apparatus and a photoelectric conversion element which photoelectrically converts a subject image formed by the lens apparatus.  
           [0003]    2. DESCRIPTION OF THE PRIOR ART  
           [0004]    In recent years, in a zoom lens for use in a broadcast television camera such as an ENG camera, a zoom track function provided for a zooming control accessory mountable on the zoom lens has allowed setting a limit value on the drive range of the zoom lens. An operation example of the zoom track function of this type is described below with reference to FIGS.  9  to  13 .  
           [0005]    FIGS.  9  to  13  are schematic diagrams and block diagrams showing the appearance of an ENG lens which supports the conventional zoom track function (for example, see Japanese Patent Application Laid-Open No. 2000-284164). In FIGS.  9  to  13 , reference numeral  1  shows a zoom lens for use in a broadcast television camera such as an ENG camera,  2  a lens barrel,  3  a drive unit,  4  a focus ring,  5  a zoom ring,  6  an iris ring,  7  an extender lever,  8  a zoom preset speed mode switch lever,  9  a frame preset switch,  10  a memory switch,  11  a send-back switch,  12  a zoom operation switch,  13  an iris operation change switch,  14  an iris momentary auto-switch,  15  a focus speed adjustment trimmer,  16  an iris gain adjustment trimmer,  17  a zoom mode adjustment trimmer,  18  a focus servo/manual switch knob,  19  and  20  zoom remote and focus remote 20-pin connectors,  21  a zoom remote 8-pin connector,  22  a zoom speed adjustment volume,  23  a zoom servo/manual switch knob,  24  a macro-button,  25  a shuttle shot switch,  26  a DIP switch unit,  27  a VTR switch,  28  a DIP switch I,  29  a DIP switch II,  30  a DIP switch III,  31  a DIP switch IV,  32  a DIP switch V,  33  a DIP switch VI,  34  a DIP switch VII,  35  a DIP switch VIII,  36  a zoom operation control accessory,  37  a 20-pin connector,  38  a zoom remote operation switch,  39  a zoom track telephoto position adjustment remote volume,  40  a zoom track wide-angle position adjustment remote volume,  41  a zoom track function valid/invalid remote switch, and  42  a zoom track valid indicator.  
           [0006]    Although the internal structure of the lens barrel  2  is not shown, the lens barrel  2  has, in order from an object side, a fixed focus lens, a movable focus lens, a zoom lens, an iris, a relay lens and the like provided therein, and an extender is disposed behind them. The focus ring  4  is rotated around an optical axis to move the movable focus lens forward and backward in the optical axis direction to achieve focusing. The zoom ring  5  is rotated around the optical axis to move the zoom lens forward and backward in the optical axis direction to achieve zooming.  
           [0007]    The iris ring  6  is rotated around the optical axis to adjust the diaphragm diameter of the iris. The drive unit  3  is mounted on a side portion of the lens barrel  2 . The drive unit  3  has a focus drive motor, not shown, arranged therein. The drive force of the focus drive motor is transmitted to the focus ring  4  through a transmission mechanism, not shown, to drive the focus ring  4  for rotation around the optical axis. Alternatively, the focus ring  4  may be rotated manually without mounting the focus drive motor on the drive unit  3 , by way of example.  
           [0008]    The drive unit  3  has a zoom drive motor arranged therein. The drive force of the zoom drive motor is transmitted to the zoom ring  5  through a transmission mechanism, not shown, to drive the zoom ring  5  for rotation about the optical axis.  
           [0009]    Similarly, the drive unit  3  has an iris drive motor, not shown, arranged therein. The drive force of the iris drive motor is transmitted to the iris ring  6  through a transmission mechanism, not shown, to drive the iris ring  6  around the optical axis.  
           [0010]    The zoom operation switch  12  is formed on the drive unit  3 . The zoom operation switch  12  is pressed to a telephoto side or a wide-angle side to drive the zoom ring  5 , thereby moving the zoom lens toward the telephoto side or wide-angle side.  
           [0011]    A zoom drive speed can be adjusted in accordance with the amount of pressing (the operation amount) of the zoom operation switch  12 . As the pressing amount is larger, the zoom drive speed is higher. The frame preset switch  9  can be pressed to move the zoom lens to a previously stored zoom position. The zoom drive speed in this case can be changed by operating the speed mode switch lever  8 . Specifically, the zoom drive speed can be changed to one of the highest possible speed or a preset speed.  
           [0012]    The send-back switch  11  can be turned on to display return video on a viewfinder. The iris operation switch  13  can be flipped to switch between manual and servo operations of the iris.  
           [0013]    While the iris auto-switch  14  is ON, the iris operation is switched to a servo operation. The set zoom position or the zoom drive speed are set by simultaneously operating the memory switch  112  and the shuttle shot switch  25 , the frame preset switch  9  or the zoom operation switch  12 . A zoom or focus operation control accessory (20-pin) is connected to the zoom remote and focus remote 20-pin connectors  19  and  20 .  
           [0014]    The focus servo/manual switch knob  18  can be flipped to switch between manual and servo operations of the focus. A zoom operation control accessory (8-pin) is connected to the zoom remote 8-pin connector  21 . The zoom speed adjustment volume  22  adjusts the speed over the entire zoom range when a zoom operation is performed by the zoom operation switch  12 . The zoom servo/manual switch knob  23  can be flipped to switch between manual and servo operations of the zoom. The macro-button  24  is used when a user intends to take a closeup of a subject located closer than the closest focusing distance. A built-in extender is operated by manipulating the extender lever  7 . A focus speed is adjusted by the focus speed adjustment trimmer  15 . An iris servo gain is adjusted by the iris gain adjustment trimmer  16 . The zoom mode adjustment trimmer  17  is used to adjust a change caused by the zoom speed adjustment volume  22 . The zoom lens is moved forward and backward at the highest speed to zoom positions which are stored corresponding to ON/OFF of the shuttle switch  25 . The DIP switches  28  to  34  are used to perform various setting such as a function assignment to the VTR switch  27  and the like. The DIP switch  35  is not assigned any setting item. The VTR switch  27  is used to perform a start operation or a stop operation of a VTR. The zoom remote operation switch  38  is disposed swingably with a neutral position as a reference. When the zoom remote operation switch  38  is pressed to the telephoto side or wide-angle side, the zoom ring  5  is rotated to the telephoto side or wide-angle side. A zoom drive speed can be adjusted by the amount of pressing (the operation amount) of the zoom remote operation switch  38 . As the pressing amount is larger, the zoom speed is higher. The zoom operation control accessory  36  is connected to the zoom remote and focus remote 20-pin connectors  19  and  20  through the 20-pin connector  37  of the zoom operation control accessory  36 . The zoom track telephoto position is adjusted by operating the zoom track telephoto position adjustment remote volume  39  of the zoom operation control accessory  36 , and the zoom track wide-angle position is adjusted by operating the zoom track wide-angle position adjustment remote volume  40 . As a result, the drive range of the zoom lens can be set. The zoom track function can be switched between valid and invalid states by operating the zoom track function valid/invalid remote switch  41  of the zoom operation control accessory  36 . In addition, the valid or invalid state of the zoom track function can be checked through the zoom track valid indicator  42  mounted on the zoom operation control accessory  36 .  
           [0015]    The aforementioned conventional example, however, has the following disadvantages since the drive unit alone cannot set the zoom track position.  
           [0016]    Specifically, since the zoom operation control accessory (20-pin) is necessary to use the zoom track function, the zoom lens on which the accessory is mounted has poor portability. Especially when a user shoulders the lens to take images for news and the like without using a tripod, the user has great difficulty in using the zoom track function. Also, the drive unit has a number of the operation switches thereon as described above, and it is extremely difficult to newly provide a zoom track position adjustment volume and a zoom track function switch in limited space on the drive unit. In addition, erasing the stored zoom track position requires another memory operation by setting the telephoto end or wide-angle end as a zoom track position, involving significant effort. Moreover, the valid or invalid state of the zoom track function can be checked only through the zoom track valid indicator mounted on the zoom operation control accessory (20-pin), and if the zoom track function is realized by the drive unit alone, no means for checking is provided.  
           [0017]    It is a first object of the present invention to allow realization of a zoom track function by a drive unit alone without newly adding an operation switch and with a minimum required amount of operation.  
           [0018]    It is a second object of the present invention to separately enable erasure of stored contents of zoom track positions and switch between valid and invalid states of the zoom track function only with an operation switch on the drive unit and through a minimum required amount of operation.  
           [0019]    It is a third object of the present invention to allow visual recognition of switch between valid and invalid states of the zoom track function without newly mounting an indicator on the drive unit.  
         SUMMARY OF THE INVENTION  
         [0020]    To achieve the aforementioned objects, according to one aspect, the present invention provides a drive control apparatus for a lens apparatus having a zoom lens movable between a telephoto end and a wide-angle end, the drive control apparatus comprising a selecting member which selects a zoom position between the telephoto end and the wide-angle end, a controller which has a drive range limiting function of controlling drive of the zoom lens by using the selected zoom position as a drive end, and a drive range switch member which switches the drive range limiting function between an invalid state and a valid state. The controller drives the zoom lens to the drive end when the drive range limiting function is switched to the valid state. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    [0021]FIG. 1 shows a drive range of a variable power lens unit of Embodiments 1 to 3 of the present invention;  
         [0022]    [0022]FIG. 2 is a flow chart showing the storage processing procedure of zoom track positions in Embodiment 1 of the present invention;  
         [0023]    [0023]FIG. 3 is a flow chart showing the drive processing procedure of the variable power lens unit in Embodiment 1 of the present invention;  
         [0024]    [0024]FIG. 4 is a flow chart showing the storage processing procedure of zoom track positions in Embodiment 2 of the present invention;  
         [0025]    [0025]FIG. 5 is a flow chart showing the drive processing procedure of the variable power lens unit in Embodiment 2 of the present invention;  
         [0026]    [0026]FIG. 6 is a flow chart showing the storage processing procedure of zoom track positions in Embodiment 3 of the present invention;  
         [0027]    [0027]FIG. 7 is a flow chart showing the processing procedure of invalid zoom track function indication in Embodiment 3 of the present invention;  
         [0028]    [0028]FIG. 8 is a flow chart showing the processing procedure of valid zoom track function indication in Embodiment 3 of the present invention;  
         [0029]    [0029]FIG. 9 is a top view of a zoom lens of a prior art;  
         [0030]    [0030]FIG. 10 is a side view of the zoom lens of the prior art;  
         [0031]    [0031]FIG. 11 is a back view of the zoom lens of the prior art;  
         [0032]    [0032]FIG. 12 is a block diagram of DIP switches of the prior art;  
         [0033]    [0033]FIG. 13 is a side view of a zoom operation control accessory of the prior art;  
         [0034]    [0034]FIG. 14 is a flow chart showing the processing procedure of valid zoom track function indication in Embodiment 4 of the present invention; and  
         [0035]    [0035]FIG. 15 is a functional block diagram showing an image-taking system in Embodiments 1 to 3.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     Embodiment 1  
       [0036]    Method of Storing Central Reference  
         [0037]    [0037]FIG. 15 shows the structure of an image-taking system according to Embodiments 1 to 3 of the present invention. In FIG. 15, reference numeral  118  shows a camera (an image-taking apparatus) such as a television camera and a video camera, and reference numeral  116  shows a lens apparatus mounted on the camera.  
         [0038]    Reference numeral  117  shows a drive unit (a drive control apparatus) mounted on the lens apparatus  116 . The lens apparatus  116  and the drive unit  117  constitute a zoom lens system.  
         [0039]    An image-taking system  119  is formed of the lens apparatus  116 , the drive unit  117 , and the camera  118 . However, the present invention is applicable to a lens apparatus of a type which contains the function of a drive unit in a zoom lens.  
         [0040]    The lens apparatus  116  of Embodiment 1 is formed in order from an object side to an image plane side as follows. Reference numeral  101  shows a lens unit, the entirety or part of which is moved in an optical axis direction to achieve manual focusing. The MF lens unit  101  is driven by mechanically transmitting rotation of a manual focus operation ring (not shown) provided for the lens apparatus  116  or converting the rotation into an electric signal to drive a motor.  
         [0041]    Reference numeral  102  is a variable power lens unit (a zoom lens), the entirety or part of which is moved in the optical axis direction to provide variable power. Reference numeral  103  shows a diaphragm unit (an iris) for adjusting an amount of light. Reference numeral  104  shows a lens unit, the entirety or part of which is moved in the optical axis direction to realize auto-focusing. These lens units and the diaphragm unit  101  to  104  constitute an image-taking optical system. The lens apparatus of Embodiment 1 is of a type which achieves a for-element focusing scheme and a rear focusing scheme in combination.  
         [0042]    Reference numeral  121  shows a variable power drive mechanism (for example, a cam) for driving the variable power lens unit  102  in the optical axis direction, and  120  an MF drive mechanism for driving the MF lens unit  101  in the optical axis direction. Reference numeral  122  shows an AF drive mechanism for driving the AF lens unit  104  in the optical axis direction. These drive mechanisms  120  to  122  are activated in response to drive force from the drive unit  117 .  
         [0043]    In the drive unit  117 , reference numeral  109  shows a variable power control section which includes a zoom actuator such as a motor which is a drive source of the variable power lens unit  102  and its drive circuit. Reference numeral  110  shows an AF control section which includes an AF actuator which is a drive source of the AF lens unit  104  and its drive circuit. Reference numeral  108  shows an MF control section which includes an MF actuator which is a drive source of the MF lens unit  101  and its drive circuit. While a control section which includes an actuator and its drive circuit, not shown, is provided for the diaphragm unit  103 , the diaphragm unit  103  can be driven by mechanical transmission of manual operation force.  
         [0044]    Reference numeral  114  shows a zoom position detector such as an encoder and a potentiometer which is coupled to the variable power drive mechanism  121  and detects the position of the variable power lens unit  102 . Reference numeral  113  shows an MF position detector such as an encoder which is coupled to the MF drive mechanism  120  and detects the position of the MF lens unit  101 . Reference numeral  115  shows an AF position detector such as an encoder which is coupled to the AF drive mechanism  122  and detects the position of the AF lens unit  104 .  
         [0045]    Reference numeral  111  shows a lens control circuit serving as a controller which controls various operations of the drive unit  117 . The lens control circuit  111  contains a CPU  111   a  which performs various operational processing and a storage section  111   b  which stores zoom track positions (later described) and the like.  
         [0046]    Reference numerals  112 ,  123 ,  124  and  125  show a memory switch, an iris auto-switch, a zoom operation switch and a DIP switch VIII provided for the drive unit  117 , respectively, and details thereof are later described.  
         [0047]    In the camera  118 , reference numeral  105  shows a glass block corresponding to an optical filter or a color separation prism. Reference numeral  106  shows an image-pickup device such as a CCD sensor and a CMOS sensor which photoelectrically converts a subject image formed by the image-taking optical system. Reference numeral  107  shows a camera control circuit controls the whole camera  118 . The camera control circuit  107  contains a CPU (not shown) which performs various operational processing, an image processing circuit which performs various image processing on an image-pickup signal from the image-pickup device  106 , and the like.  
         [0048]    In the following, Embodiment 1 of the present invention is described with reference to FIGS.  1  to  3  and FIG. 15.  
         [0049]    [0049]FIG. 1 shows the drive range of the variable power lens unit  102 . Reference numeral  42  shows a telephoto end,  43  a wide-angle end,  44  an intermediate point between the telephoto end  42  and the wide-angle end  43 ,  45  a telephoto area from the telephoto end  42  to the intermediate point  44 , and  46  a wide-angle area from the wide-angle end  43  to the intermediate point  44 .  
         [0050]    Processing in Embodiment 1 can be divided into storage processing of zoom track positions and drive processing of the variable power lens unit. First, the procedure of the zoom track storage processing is described with reference to FIGS. 1 and 15. When the memory switch  112  and the iris auto-switch  123  are simultaneously turned on, the position of the variable power lens unit  102  at that point is stored as a zoom track telephoto position if the position falls within the telephoto area  45 , or as a zoom track wide-angle position if the position falls within the wide-angle area  46  in the storage section  111   b  such as an EEPROM.  
         [0051]    Next, the flow of zoom track drive processing is described. When the zoom operation switch  124  is flipped to the telephoto side, the variable power lens unit  102  is driven until the variable power lens unit  102  reaches the zoom track telephoto position. When the zoom operation switch  124  is flipped to the wide-angle side, the variable power lens unit  102  is driven until the variable power lens unit  102  reaches the zoom track wide-angle position.  
         [0052]    In other words, in Embodiment 1, the two zoom track positions of the telephoto direction and wide-angle direction can be stored in the storage section  111   b  by simultaneously operating the memory switch  112  and the iris auto-switch  123 .  
         [0053]    [0053]FIG. 2 is a flow chart showing the store processing procedure of the zoom track positions in the aforementioned storage processing. The flow chart is performed by the controller  111 . At step  101 , when the memory switch  112  is turned on, the flow proceeds to step  102 , or when it is not turned on, the flow proceeds to drive processing of the variable power lens unit shown in FIG. 3.  
         [0054]    At step  102 , when the iris auto-switch  123  is turned on, the flow proceeds to step  103 , or when it is not turned on, the flow proceeds to the drive processing of the variable power lens unit shown in FIG. 3.  
         [0055]    At step  103 , when the variable power lens unit  102  is positioned in the telephoto area  45 , the flow proceeds to step  104 , or when it is positioned in the wide-angle area  46 , the flow proceeds to step  105 . At step  104 , the position of the variable power lens unit  102  is stored as the zoom track telephoto position, and at step  105 , the position of the variable power lens unit  102  is stored as the zoom track wide-angle position in the storage section  111   b . Upon completion of the storage processing, the flow proceeds to the drive processing of the variable power lens unit shown in FIG. 3.  
         [0056]    Next, the drive processing procedure of the variable power lens unit is described with reference to FIG. 3. FIG. 3 is a flow chart showing the control procedure of the variable power lens unit  102 . The flow chart is performed by the controller  111 . At step  201 , when the zoom servo/manual switch knob  126  is set to the servo position, the flow proceeds to step  202 , or when the zoom servo/manual switch knob  126  is set to the manual position, the flow proceeds to step  207 .  
         [0057]    At step  202 , when the variable power lens unit  102  is positioned within a zoom track setting range, the flow proceeds to step  203 , or when the variable power lens unit  102  is out of the zoom track setting range, the flow proceeds to step  207 .  
         [0058]    At step  203 , when the zoom operation switch  124  is flipped to the telephoto side, the flow proceeds to step  204 . When the zoom operation switch  124  is flipped to the wide-angle side, the flow proceeds to step  205 .  
         [0059]    At step  204 , the variable power lens unit  102  is driven toward the telephoto side, and then the flow proceeds to step  207 . At step  205 , when the zoom operation switch  124  is flipped to the wide-angle side, the flow proceeds to step  206 , or when the zoom operation switch  124  is flipped to the telephoto side, the flow proceeds to step  207 . At step  206 , the variable power lens unit  102  is driven toward the wide-angle side, and then the flow proceeds to step  207 . At step  207 , the drive of the variable power lens unit  102  is stopped to start the storage processing of the zoom track position shown in FIG. 2.  
         [0060]    In this manner, the storage processing of the positions of the variable power lens unit  102  is provided for the two areas, that is, the telephoto area and the wide-angle area, separated by using the intermediate point  44  between the telephoto end  42  and the wide-angle end  43  as the boundary. The memory switch  112  and the iris auto-switch  123  are simultaneously operated to allow the two zoom track positions on the telephoto side and the wide-angle side to be stored in the storage section  111   b  without newly adding a switch.  
         [0061]    In Embodiment 1, when the variable power lens unit  102  is positioned at the intermediate point  44 , the position is stored as the zoom track wide-angle position in the storage section  111   b . In this case, however, the position may be stored as the zoom track telephoto position, or the zoom track position storage processing may be exited to start the zoom track lens drive processing.  
         [0062]    In addition, in Embodiment 1, the storage processing for one of the two zoom track positions in the telephoto area and the wide-angle area is selectively used in accordance with the position of the variable power lens unit  102 . However, the storage processing for one of the two zoom track positions may be selectively used in accordance with an operation method of the switch, for example, the memory switch  112  held on for a certain time period or turned on continuously a plurality of times.  
         [0063]    According to the aforementioned structure, an operator can set the zoom track positions before images are taken only by the single memory switch  112 , resulting in easier operations and allowing the operator to concentrate on other operations. In addition, the space for arranging the switches can be saved and the part cost can be reduced to cause improved cost performance of products.  
       Embodiment 2  
       [0064]    Method of Initializing Memory and Switching Valid and Invalid  
         [0065]    In the following, Embodiment 2 of the present invention is described with reference to FIGS. 1, 4,  5 , and  15 . When the DIP switch VIII  125  (a drive range switch member) is turned on, the zoom track function is turned on. When the DIP switch VIII  125  is turned off, the zoom track function is turned off to erase the stored contents of zoom track positions.  
         [0066]    On the other hand, when a certain time period elapses with the memory switch  112  and the iris auto-switch  123  turned on, the zoom track function becomes invalid if it is valid, or becomes valid if it is invalid.  
         [0067]    In other words, in Embodiment 2, it is possible to set switching between a valid state and an invalid state of the zoom track function and erasure of the stored contents of the zoom track positions.  
         [0068]    Similarly to Embodiment 1, processing in Embodiment 2 can be divided into storage processing of zoom track positions and drive processing of the variable power lens unit. First, the flow of the storage processing in blocks is described with reference to FIGS. 1 and 4. When the DIP switch VIII  125  is turned off, the zoom track function is turned off to erase the stored contents of the zoom track positions. When a certain time period elapses with the memory switch  112  and the iris auto-switch  123  turned on while the DIP switch VIII  125  is turned on, the zoom track function becomes invalid if it is valid, or becomes valid if it is invalid.  
         [0069]    When both of the memory switch  112  and the iris auto-switch  123  are turned off within a certain time period after the memory switch  112  and the iris auto-switch  123  are turned on, the position of the variable power lens unit  102  is stored as the zoom track telephoto position if the position of the variable power lens unit  102  falls within the telephoto area  45 , or the position of the variable power lens unit  102  is stored as the zoom track wide-angle position if the position of the variable power lens unit  102  falls within the wide-angle area  46 .  
         [0070]    In other words, in Embodiment 2, the zoom track positions can be initialized without performing resetting of the zoom track positions at the telephoto end and the wide-angle end or switching of the power. In addition, switching between the valid and invalid states of the zoom track function can be realized without initializing the zoom track positions.  
         [0071]    [0071]FIG. 4 is a flow chart showing the storage processing procedure of the zoom track positions in the aforementioned storage processing. The flow chart is performed by the controller  111 . In FIG. 4, at step  301 , when the DIP switch VIII  125  is turned on, the flow proceeds to step  302 . When the DIP switch VIII  125  is not turned on, the flow proceeds to step  303 .  
         [0072]    At step  303 , the stored contents of the zoom track positions are erased, and then the flow proceeds to drive processing of the variable power lens unit shown in FIG. 5. At step  302 , when both of the memory switch  112  and the iris auto-switch  123  are turned on, the flow proceeds to step  304 , or when both of the memory switch  112  and the iris auto-switch  123  are not turned on, the flow proceeds to the drive processing of the variable power lens unit shown in FIG. 5.  
         [0073]    At step  304 , a timer, not shown, is initialized to start counting, and then the flow proceeds to step  305 . At step  305 , when the timer counts for a certain time period or longer, the flow proceeds to step  307 , or when the timer counts for less than the certain time period, the flow proceeds to step  306 . At step  306 , when the memory switch  112  and the iris auto-switch  123  are not turned on, the flow proceeds to step  305 , or when both of the memory switch  112  and the iris auto-switch  123  are turned on, the flow proceeds to step  308 .  
         [0074]    At step  308 , when the position of the variable power lens unit  102  falls within the telephoto area  45 , the flow proceeds to step  309 , or when the position of the variable power lens unit  102  falls within the wide-angle area  46 , the flow proceeds to step  310 . At step  309 , the position of the variable power lens unit  102  within the telephoto area  45  at that point is stored as the zoom track telephoto position. At step  310 , the position of the variable power lens unit  102  is stored as the zoom track wide-angle position. At step  307 , when the zoom track function is valid, the flow proceeds to step  311 , or when the zoom track function is invalid, the flow proceeds to step  312 .  
         [0075]    At step  311 , the zoom track function is switched to the invalid state. At step  312 , the zoom track function is switched to the valid state. After completion of the aforementioned processing, the flow proceeds to the drive processing of the variable power lens unit  102  shown in FIG. 5.  
         [0076]    [0076]FIG. 5 is a flow chart showing the drive processing procedure of the variable power lens unit  102 . The flow chart is performed by the controller  111 . In FIG. 5, at step  401 , when the zoom servo/manual switch knob  126  is set to the servo position, the flow proceeds to step  402 , or when the zoom servo/manual switch knob  126  is not set to the servo position, the flow proceeds to step  409 .  
         [0077]    At step  402 , when the DIP switch VIII  125  is turned on, the flow proceeds to step  403 , or when the DIP switch VIII  125  is not turned on, the flow proceeds to step  409 . At step  403 , when the zoom track function is valid, the flow proceeds to step  404 , or when the zoom track function is not valid, the flow proceeds to step  409 .  
         [0078]    At step  404 , when the variable power lens unit  102  is positioned within the zoom track setting range, the flow proceeds to step  405 , or when the variable power lens unit  102  is out of the zoom track setting range, the flow proceeds to step  409 .  
         [0079]    At step  405 , when the zoom operation switch  124  is flipped to the telephoto side, the flow proceeds to step  406 , or when the zoom operation switch  124  is not flipped to the telephoto side, the flow proceeds to step  407 . At step  406 , the variable power lens unit  102  is driven toward the telephoto side. At step  407 , when the zoom operation switch  124  is flipped to the wide-angle side, the flow proceeds to step  408 , or when the zoom operation switch is not flipped to the wide-angle side, the flow proceeds to step  409 .  
         [0080]    At step  408 , the variable power lens unit  102  is driven toward the wide-angle side, and then the flow proceeds to step  409 . At step  409 , the drive of the variable power lens unit is stopped to proceed to the storage processing of the zoom track positions shown in FIG. 4.  
         [0081]    In this manner, the DIP switch VIII  125  is provided with the function of erasing the stored zoom track positions, and the function of switching the valid and invalid states of the zoom track function is added such that the function is triggered by the memory switch  112  and the iris auto-switch  123  turned on simultaneously for the certain time period or longer. Consequently, the erasure of the zoom track positions and the switching between the valid and invalid states of the zoom track function can be achieved separately without newly adding a switch.  
         [0082]    In Embodiment 2, the two zoom track positions in the telephoto area and wide-angle area are simultaneously initialized by holding the state in which the memory switch  112  and the iris auto-switch  123  are turned on for the certain time period. Alternatively, it is possible that only one of them is erased depending on the position of the variable power lens unit  102  at that point in the telephoto area or the wide-angle area.  
         [0083]    According to the aforementioned structure, an operator can erase the stored contents of the zoom track positions before images are taken without resetting the zoom track positions and can switch between the valid and invalid states of the zoom track function with the stored contents of the zoom track positions maintained, resulting in easier operations and allowing the operator to concentrate on other operations.  
       Embodiment 3  
       [0084]    Valid/Invalid Indicator  
         [0085]    In the following, Embodiment 3 of the present invention is described with reference to FIGS. 1, 6 to  8 , and  15 .  
         [0086]    Since description has already been made for FIG. 1, repetitive description thereof is omitted. In addition, basic operations are similar to those in Embodiment 2, so that description thereof is omitted. When both of the memory switch  112  and the iris auto-switch  123  are held on for a certain time period or longer with the zoom track function valid, the zoom track function becomes invalid. In addition, when the variable power lens unit  102  is positioned in the telephoto area  45 , the variable power lens unit  102  is driven to the telephoto end, and when it is positioned in the wide-angle area  46 , the variable power lens unit  102  is driven to the wide-angle end.  
         [0087]    When both of the memory switch  112  and the iris auto-switch  123  are held on for the certain time period or longer with the zoom track function invalid, the zoom track function becomes valid. In addition, when the variable power lens unit  102  is positioned in the telephoto area  45 , the variable power lens unit  102  is driven to the zoom track telephoto position, and when it is positioned in the wide-angle area  46 , the variable power lens unit  102  is driven to the zoom track wide-angle position.  
         [0088]    In other words, in Embodiment 3, the variable power lens unit  102  is driven to the zoom track telephoto position or the zoom track wide-angle position, or the telephoto end or the wide-angle end when the zoom track function is switched between the valid and invalid states, thereby making it possible to indicate that the zoom track function is switched to the valid or invalid state.  
         [0089]    [0089]FIG. 6 is a flow chart showing the storage processing procedure of the zoom track position in Embodiment 3. The flow chart is performed by the controller  111 . In FIG. 6, processing from step  501  to  510  are similar to that from step  301  to step  310  shown in FIG. 4, so that description thereof is omitted.  
         [0090]    At step  511 , the zoom track function is switched to the invalid state, and then the flow proceeds to processing of invalid zoom track function indication shown in FIG. 7. At step  512 , the zoom track function is switched to the valid state, and then the flow proceeds to processing of valid zoom track function indication shown in FIG. 8.  
         [0091]    [0091]FIG. 7 is a flow chart showing the processing procedure of invalid zoom track function indication in Embodiment 3. At step  601 , when the variable power lens unit  102  is positioned in the telephoto area  45 , the flow proceeds to step  602 , or when the variable power lens unit  102  is positioned in the wide-angle area  46 , the flow proceeds to step  603 .  
         [0092]    At step  602 , the variable power lens unit  102  is driven to the telephoto end, and then the flow proceeds to the drive processing of the variable power lens unit shown in FIG. 5. At step  603 , the variable power lens unit  102  is driven to the wide-angle end, and then the flow proceeds to the drive processing of the variable power lens unit shown in FIG. 5.  
         [0093]    [0093]FIG. 8 is a flow chart showing the processing procedure of valid zoom track function indication in Embodiment 3. In FIG. 8, when the variable power lens unit  102  is positioned in the telephoto area  45  at step  701 , the flow proceeds to step  702 , or when the variable power lens unit  102  is positioned in the wide-angle area  46 , the flow proceeds to step  703 . At step  702 , the variable power lens unit  102  is driven to the zoom track telephoto position, and then the flow proceeds to the zoom drive processing shown in FIG. 5. At step  703 , the variable power lens unit  102  is driven to the zoom track wide-angle position, and then the flow proceeds to the zoom drive processing shown in FIG. 5.  
         [0094]    In this manner, the variable power lens unit  102  is driven to the zoom track telephoto position or the zoom track wide-angle position, or the telephoto end or the wide-angle end when the zoom track function is switched between the valid and invalid states to make the indication of the zoom track function switched to the valid or invalid state. Thus, an operator can visually recognize that the zoom track function is switched to the valid or invalid state.  
         [0095]    In Embodiment 3, the variable power lens unit  102  is driven to the zoom track telephoto position or the zoom track wide-angle position, or the telephoto end or the wide-angle end in accordance with the position of the variable power lens unit  102 . Alternatively, the operator may visually recognize the zoom track function switched to the valid or invalid state by setting a single fixed drive direction of the variable power lens unit  102  regardless of the position of the variable power lens unit  102 .  
         [0096]    According to the aforementioned structure, the operator can recognize that the zoom track function is switched to the valid or invalid state without newly setting an indicator. In addition, when the zoom track function is switched to the valid state with the variable power lens unit  102  positioned out of the zoom track setting range, it is possible to prevent erroneous start of image taking out of the zoom track setting range and to eliminate the need to manually move the variable power lens unit  102  into the zoom track setting range. Thus, a focus detection area can be switched quickly, and the operator can concentrate on other operations.  
       Embodiment 4  
       [0097]    In Embodiment 3, the variable power lens unit  102  is driven regardless of whether or not a zoom track position is stored in the storage section  111   b in the valid zoom track indication processing. Namely, the variable power lens unit  102  is driven to the telephoto end or the zoom track telephoto position when the variable power lens unit  102  is positioned in the telephoto area, or the variable power lens unit  102  is driven to the wide-angle end or the zoom track wide-angle position when the variable power lens unit  102  is positioned in the wide-angle area.  
         [0098]    For example, when only the telephoto position is stored as the zoom track position, the variable power lens unit  102  is moved to the wide-angle end resulting from the valid zoom track indication processing when the variable power lens unit  102  is not positioned in the telephoto area. In this case, the variable magnification lens unit  102  after the valid zoom track indication processing is at the same position as that after the invalid zoom track indication processing, thereby making it impossible to determine whether the zoom track function is valid or invalid.  
         [0099]    To address this, when only one of the telephoto position and the wide-angle position is stored as the zoom track position, the variable power lens unit  102  is moved to the set zoom track position in the valid zoom track indication processing regardless of the position of the variable power lens unit  102  to allow visual recognition of whether the zoom track function is valid or invalid.  
         [0100]    Embodiment 4of the present invention is hereinafter described with reference to FIGS. 1, 6,  7 ,  14 , and  15 . Since description has already been made for FIGS. 1, 6,  7 , and  15 , detailed description thereof is omitted.  
         [0101]    [0101]FIG. 14 is a flow chart showing the processing procedure of valid zoom track function indication in Embodiment 4. The flow chart is performed by the controller  111 . In FIG. 14, at step  801 , it is determined whether or not neither a telephoto position nor a wide-angle position is stored as a zoom track position. When neither the telephoto position nor the wide-angle position is stored as the zoom track position, the flow proceeds to step  802  where it is determined whether or not the variable power lens unit  102  is positioned in the telephoto area  45 .  
         [0102]    When it is determined that the variable power lens unit  102  is positioned in the wide-angle area  46  at step  802 , the flow proceeds to step  803  where the variable power lens unit  102  is moved to the wide-angle end. When it is determined that the variable power lens unit  102  is positioned in the telephoto area  45 , the flow proceeds to step  804  where the variable power lens unit  102  is moved to the telephoto end.  
         [0103]    Then, zoom drive processing is performed. At step  801 , when it is determined that neither the telephoto position nor the wide-angle position is stored as the zoom track position, the flow proceeds to step  805  where it is determined whether or not only one of the telephoto position and the wide-angle position is stored as the zoom track position.  
         [0104]    When only one of the telephoto position and the wide-angle position is stored as the zoom track position, the flow proceeds to step  806  where it is determined whether or not the stored zoom track position is the telephoto position. At step  806 , when the stored zoom track position is not the telephoto position, the flow proceeds to step  807  where the variable power lens unit  102  is moved to the zoom track wide-angle position.  
         [0105]    At step  806 , when the stored zoom track position is the telephoto position, the flow proceeds to step  808  where the variable power lens unit  102  is moved to the zoom track telephoto position. Then, the zoom drive processing is performed. At step  805 , when it is determined that both of the telephoto position and the wide-angle position is stored as the zoom track position, the flow proceeds to step  809 .  
         [0106]    At step  809 , it is determined whether or not the variable power lens unit  102  is positioned in the telephoto area  45 . When it is determined that the variable power lens unit  102  is positioned in the wide-angle area  46 , the flow proceeds to step  810  where the variable power lens unit  102  is moved to the zoom track wide-angle position. At step  809 , when it is determined that the variable power lens unit  102  is positioned in the telephoto area  45 , the flow proceeds to step  811  where the variable power lens unit  102  is moved to the zoom track telephoto position. Then, the zoom drive processing is performed.  
         [0107]    In this manner, if only one of the telephoto position and the wide-angle position is stored as the zoom track position when the zoom track function is switched to the valid state, the variable power lens unit  102  is moved to the set zoom track position in the valid zoom track indication processing regardless of the position of the variable power lens unit  102 . Thus, an operator can visually recognize whether the zoom track function is valid or invalid.  
         [0108]    According to the aforementioned structure, the operator can see that the zoom track function is switched to the valid or invalid state without newly setting an indicator. In addition, when the zoom track function is switched to the valid state with the variable power lens unit  102  positioned out of the zoom track setting range, it is possible to prevent erroneous start of image taking out of the zoom track setting range and to eliminate the need to manually move the variable power lens unit  102  into the zoom track setting range. Thus, a focus detection area can be switched quickly, and the operator can concentrate on other operations.
A drive control apparatus for a lens apparatus having a zoom lens movable between a telephoto end and a wide-angle end according to the present invention comprises a selecting member which selects a zoom position between the telephoto end and the wide-angle end, a controller which has a drive range limiting function of controlling drive of the zoom lens by using the selected zoom position as a drive end, and a drive range switch member which switches the drive range limiting function between an invalid state and a valid state. The controller drives the zoom lens to the drive end when the drive range limiting function is switched to the valid state.