Abstract:
This invention provides a lens device and a correction method therefor whereby the focal position of the lens device can be corrected with high accuracy even if a lens surface shape or the like is not uniform. A ring-shaped lens fixing frame  52  is mounted on the outer periphery of a lens  51.  A gear  53  is formed on the lens fixing frame  52  in the circumferential direction. A gear  54,  which engages with the gear  53,  is rotated by a motor  20 A. Then, the lens  51  rotates about the optical axis L thereof. Further, a rack  57,  which extends in the direction of the optical axis L, is formed on a part of the lens fixing frame  52.  A pinion  58  engages with the teeth  57 A of the rack  57,  and the pinion  58  is rotated by another motor  20 B. Then, the rack  57  moves in the direction of the optical axis L, and thus the lens  51  moves in the direction of the optical axis L. Since the lens  51  rotates about the optical axis L thereof, even if the surface shape or the like of the lens  51  is uneven in the circumferential direction, improvement can be realized.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a Continuation of PCT International Application No. PCT/JP2015/055108 filed on Feb. 24, 2015, which claims priority under 35 U.S.C. §119(a) to Japanese Patent Application No. 2014-067470 filed Mar. 28, 2014. Each of the above application(s) is hereby expressly incorporated by reference, in its entirety, into the present application. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to a lens device and a correction method for the lens device. 
         [0004]    2. Description of the Related Art 
         [0005]    There has been a progress in lens performance, and thus there has been a demand for lens position adjustment at a level which cannot be supported in conventional lens processing and adjustment. In particular, in a lens having performance superior to that of a high-definition television broadcast system, an effect of the adjustment is significant. For example, on the basis of respective functions, box-type lenses can be classified into five parts of a focus lens group, a zoom lens group, a vibration-proof lens group, an extender, and a master lens group. In a theoretical lens shape and mechanical components, focal positions at zoom positions are predetermined. However, the focal position is shifted due to an abnormal state caused by a lens surface shape, processing errors in mechanical dimensions, and the like, and thus a phenomenon, in which a focal position is minutely shifted in accordance with the zoom position, occurs (zooming focus shift). Further, also in a diaphragm which is disposed behind the zoom lens group, a phenomenon, in which the focal position is shifted, occurs (stopping focus shift). 
         [0006]    In the conventional art, such a change has been dealt with by selection of mechanical components or the like. However, the conventional art is unable to achieve performance superior to that of a high-definition television broadcast system, and thus it is not possible to obtain desired performance. 
         [0007]    Hence, there is a lens in which on the basis of the correspondence relationship between the zoom positions and the focal positions, a position of a focus lens is adjusted in accordance with the zoom position (JP2004-233892A). Further, there is a lens in which a focal position is corrected in accordance with the zoom position (JP2003-57528A), and also there is a lens in which correction is performed on only a master lens group (JP1998-186209A (JP-H10-186209A)). 
       SUMMARY OF THE INVENTION 
       [0008]    However, in any of JP2004-233892A, JP2003-57528A, and JP1998-186209A (JP-H10-186209A), it is not possible to accurately correct a focal position. For example, in the description of JP2003-57528A, correction of a focus shift amount is performed using a focus lens group, but a weight of the focus lens group is heavy. Accordingly, it is difficult to increase a speed of the correction. Further, in the description of JP1998-186209A (JP-H10-186209A), correction of a focus shift amount is performed using a master lens group, but a stroke of adjustment of the master lens group reaches an upper limit in correction. Therefore, in a case where a zoom lens group is set on a telephoto side, sufficient correction is not performed. In particular, in a case where a lens surface shape or a refractive index is not uniform, if such an effect is not eliminated, it is not possible to perform sufficient correction. 
         [0009]    This invention has an object to correct a focal position with high accuracy even in a case where the lens surface shape or the refractive index is not uniform. 
         [0010]    A lens device according to this invention comprises: a plurality of lenses; a lens moving mechanism that moves one or more lenses, which are included in the plurality of lenses, in a direction of an optical axis of the plurality of lenses; a storage section that stores a plurality of positions of the plurality of lenses in the direction of the optical axis and a plurality of rotation angles respectively corresponding to the plurality of positions; and a lens rotating mechanism that rotates at least one lens, which are included in the plurality of lenses, about the optical axis of the lens by a rotation angle corresponding to a position of the lens, which is moved by the lens moving mechanism, in the direction of the optical axis, among the plurality of rotation angles stored in the storage section, and that is driven separately from the lens moving mechanism. The lens rotating mechanism, which can be driven separately from the lens moving mechanism, is defined as a lens rotating mechanism on which operations of the lens moving mechanism have no effect. 
         [0011]    This invention also provides a correction method for the lens device. That is, in a correction method for a lens device having a plurality of lenses, a lens moving mechanism moves one or more lenses, which are included in the plurality of lenses, in a direction of an optical axis of the plurality of lenses, a storage section stores a plurality of positions of the plurality of lenses in the direction of the optical axis and a plurality of rotation angles respectively corresponding to the plurality of positions, and a lens rotating mechanism can be driven separately from the lens moving mechanism, and rotates at least one lens, which are included in the plurality of lenses, about the optical axis of the lens by a rotation angle corresponding to a position of the lens, which is moved by the lens moving mechanism, in the direction of the optical axis, among the plurality of rotation angles stored in the storage section. 
         [0012]    The at least one lens, which is rotated by the lens rotating mechanism, is a lens, of which at least one of a surface shape or a refractive index is relatively uneven in a circumferential direction orthogonal to the optical axis and centered on the optical axis, among the plurality of lenses. 
         [0013]    The at least one lens, which is rotated by the lens rotating mechanism, may be a lens, of which an optical sensitivity is relatively low, among the plurality of lenses. 
         [0014]    In a case where the lens device includes a zoom optical system, the lens, which is moved by the lens moving mechanism, may be a lens included in the zoom optical system. 
         [0015]    The plurality of lenses may include a focus optical system that is moved by a first movement unit so as to thereby adjust a focal position, a master optical system that is moved by a second movement unit, which is smaller than a movement unit of the focus optical system, so as to thereby adjust the focal position, and a zoom optical system that changes a zoom ratio. Further, the lens device may further comprise: a diaphragm that restricts an amount of incident light; and adjustment control means for performing at least one of adjustment of the focal position performed by the focus optical system or adjustment of the focal position performed by the master optical system, on the basis of an amount of variation in focal position which is predetermined to correspond to the zoom ratio of the zoom optical system or an aperture value of the diaphragm. 
         [0016]    The lens device may further comprise a memory that stores an amount of adjustment of the focal position. 
         [0017]    As adjustment of the focal position performed by the adjustment control means, only adjustment of the focal position based on movement of the focus optical system is performed if the zoom ratio is at a telephoto end, or only adjustment of the focal position based on movement of the master optical system is performed if the zoom ratio is at a wide-angle end. 
         [0018]    In accordance with the amount of variation in focal position, the amount of adjustment of the focal position based on the movement of the focus optical system may be larger at a position closer to the telephoto end and may be smaller at a position closer to the wide-angle end, and the amount of adjustment of the focal position based on the movement of the master optical system may be larger at a position closer to the wide-angle end and may be smaller at a position closer to the telephoto end. 
         [0019]    In accordance with the amount of variation in focal position, in a case of an aperture value at which an opening of the diaphragm is minimized, only the adjustment of the focal position based on the movement of the focus optical system may be performed, and in a case of an aperture value at which the opening of the diaphragm is maximized, only the adjustment of the focal position based on the movement of the master optical system may be performed. 
         [0020]    In accordance with the amount of variation in focal position, the amount of adjustment of the focal position based on the movement of the focus optical system may be larger at an aperture value closer to an aperture value at which the opening of the diaphragm is minimized, and may be smaller at an aperture value closer to an aperture value at which the opening of the diaphragm is maximized, and the amount of adjustment of the focal position based on the movement of the master optical system may be larger if a size of the opening of the diaphragm is closer to a maximum thereof and may be smaller if the size of the opening of the diaphragm is closer to a minimum thereof. 
         [0021]    According to this invention, the plurality of positions of the plurality of lenses in the direction of the optical axis and the plurality of rotation angles respectively corresponding to the plurality of positions are stored. The lens is rotated about the optical axis by a rotation angle corresponding to the position of the moved lens in the direction of the optical axis, separately from the movement of the lens in the direction of the optical axis. In accordance with the position in the direction of the optical axis, such a rotation angle of the lens as that which eliminates non-uniformity in the lens surface shape, the refractive index, and the like is stored. Thereby, it is possible to eliminate adverse effects caused by non-uniformity in the lens surface shape, the refractive index, and the like. It is possible to correct the focal position with high accuracy even in a case where the lens surface shape or the refractive index is not uniform. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  shows an optical configuration and an electrical configuration of a television camera lens. 
           [0023]      FIG. 2  shows a lens moving mechanism and a lens rotating mechanism. 
           [0024]      FIG. 3  is an exploded perspective view of a lens, a lens fixing frame, and a lens holding frame. 
           [0025]      FIG. 4  is a rear view of a lens onto which a lens fixing frame is fixed. 
           [0026]      FIG. 5  is a plan view illustrating a rack. 
           [0027]      FIG. 6  is an example of a table of positions and rotation angles. 
           [0028]      FIG. 7  is an example of a table of zoom ratios and amounts of variation in focal position. 
           [0029]      FIG. 8  is an example of a table of aperture values and the amounts of variation in focal position. 
           [0030]      FIG. 9  is an example of a table illustrating a relationship between the zoom ratios, the aperture values, and the amounts of variation. 
           [0031]      FIG. 10  is a flowchart illustrating a procedure of processing of generating the amounts of variation in focal position. 
           [0032]      FIG. 11  is a flowchart illustrating a procedure of processing of adjusting the focal position. 
           [0033]      FIG. 12  is a flowchart illustrating a procedure of processing of adjusting the focal position. 
           [0034]      FIG. 13  is a flowchart illustrating a procedure of processing of adjusting the focal position. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0035]      FIG. 1  is a block diagram illustrating an electric configuration of a television camera lens (lens device)  1 . 
         [0036]    All operations of the television camera lens  1  are integrally controlled by a control circuit  40 . 
         [0037]    The television camera lens  1  includes an imaging element  11 . A focus optical system  2  including a single or a plurality of lenses, a zoom optical system  5  that changes a zoom ratio, a diaphragm  6 , an extender lens (group)  7 , and a master optical system  10  including a single or a plurality of lenses are disposed in front of the imaging element  11 . The optical axis L of the television camera lens  1  passes through centers of the light receiving surfaces of a focus optical system  2 , a zoom optical system  5 , a diaphragm  6 , a master optical system  10 , and an imaging element  11 . The zoom optical system  5  includes a single or a plurality of variable power system lenses  3  and a single or plurality of correction system lenses  4 . In the extender lens  7 , an imaging lens  8  having an imaging magnification of 1× and an imaging lens  9  having an imaging magnification of 2× are mounted on a turret board (not shown in the drawing). The turret board of the extender lens  7  rotates in accordance with a switching control signal issued from a changing-over switch  41 . Then, either one of the imaging lens  8  having a magnification of 1× or the imaging lens  9  having a magnification of 2× is positioned on the optical axis L. 
         [0038]    A detector  13  detects lens positions of the lenses included in the focus optical system  2 . A detection signal, which indicates the lens positions of the lenses included in the focus optical system  2  detected by the detector  13 , is converted into digital detection data in an analog/digital conversion circuit  14 , and is input to the control circuit  40 . A user sets an amount of focus by turning a focus ring (not shown in the drawing). The control circuit  40  compares the set amount of focus and the detected lens positions of the lenses included in the focus optical system  2  represented by the digital detection data. On the basis of the result of the comparison, data, which indicates an amount of driving of the lenses included in the focus optical system  2 , is generated. The data, which indicates the generated amount of driving, is given to the driving circuit  15 , and the driving circuit  15  controls a focus motor  16 . Thereby, the lens positions of the lenses included in the focus optical system  2  are adjusted. 
         [0039]    The variable power system lens  3  constituting the zoom optical system  5  changes a focal length, and the correction system lens  4  performs correction so as not to change the focal position. If a zoom command issued from a zoom button  46  is given to the control circuit  40 , the control circuit  40  controls a driving circuit  19 A, and causes the motor  20 A to rotate. The motor  20 A moves at least one of the variable power system lens  3  or the correction system lens  4  on the optical axis L. As might be expected, by rotating a zoom cam barrel (not shown in the drawing) that rotates in accordance with rotation of a zoom ring (not shown in the drawing) operated by a user, the variable power system lens  3  and the correction system lens  4  may be moved along the optical axis L in a fixed relationship. The detector  17  detects a zoom position of the zoom optical system  5 . The detection signal, which is output from the detector  17 , is converted into the digital detection data in the analog/digital conversion circuit  18 , and is input to the control circuit  40 . The control circuit  40  compares an amount of zooming, which is set using a zoom ring, and the detected lens positions of the lenses included in the zoom optical system  5  represented by the digital detection data. On the basis of the result of the comparison, data, which indicates an amount of driving of the lenses included in the zoom optical system  5 , is generated. The data, which indicates the generated amount of driving, is given to the driving circuit  19 , and the driving circuit  19 A controls a zoom motor  20 A. Thereby, the lens positions of the variable power system lens  3  and the correction system lens  4  constituting the zoom optical system  5  are adjusted. 
         [0040]    In this example, the lenses included in the zoom optical system  5  are rotated about the optical axis L. Hence, the television camera lens  1  includes a driving circuit  19 B and a motor  20 B. The driving circuit  19 B drives the motor  20 B, whereby it is possible to rotate a desired lens, which is included in the zoom optical system  5 , about the optical axis L. 
         [0041]    The detector  23  detects an amount of aperture of the diaphragm  6 . The detection signal, which is output from the detector  23 , is converted into the digital detection data by the analog/digital conversion circuit  24 , and is input to the control circuit  40 . Further, data, which indicates an amount of driving, is generated in accordance with an amount of rotation of a diaphragm ring (not shown in the drawing) operated by a user. The data, which indicates the generated amount of driving, and the data, which indicates the detected amount of driving, are compared. On the basis of the result of the comparison, data, which indicates the amount of driving of the diaphragm  6 , is generated. The data, which indicates the generated amount of driving, is given to the driving circuit  21 , and the driving circuit  21  controls a diaphragm motor  22 . Thereby, the diaphragm  6  is set at a desired aperture value. 
         [0042]    A photo interrupter (detector)  25  is provided in the vicinity of the extender lens  7 . The photo interrupter  25  detects whether either one of imaging lenses  8  or  9  constituting the extender lens  7  is positioned on the optical axis L. An output signal issued from the photo interrupter  25  is input to the control circuit  40 , and it is detected whether the imaging lens  8  or  9  designated by the changing-over switch  41  is positioned on the optical axis L. If the imaging lens  8  or  9  designated by the changing-over switch  41  is positioned on the optical axis L, the designated imaging lens  8  or  9  is positioned on the optical axis L, and the driving data is generated by the control circuit  40 , and is given to the driving circuit  26 . The driving circuit  26  controls the extender motor  27  such that the imaging lens  8  or  9  is positioned on the optical axis L. 
         [0043]    A flange-back adjustment knob  30 , which is for setting an amount of adjustment of the master optical system  10  including a single or a plurality of lenses, is provided. Data, which indicates the amount of adjustment that is set by the knob  30 , is input to the control circuit  40 . Further, a detection signal, which is output from a potentiometer (detector)  28  that detects the amount of movement of the master optical system  10 , is input to the analog/digital conversion circuit  29 , is converted into digital detection data, and is input to the control circuit  40 . The data, which indicates the amount of adjustment that is set by the knob  30 , and the digital detection data, which indicates the amount of movement of the master optical system  10 , are compared in the control circuit  40 . On the basis of the result of the comparison, the driving data is generated. The generated driving data is given to the driving circuit  31 , and the master lens motor  32  is driven. The master optical system  10  moves along the optical axis L, whereby focus correction is performed such that a subject image is in focus on the imaging surface of the imaging element  11 . 
         [0044]    A video signal, which is output from the imaging element  11 , is input to the signal processing circuit  12 , and signal processing such as sampling processing, white color balance adjustment, and gamma correction is performed, whereby a television signal is generated. The generated television signal is output to a viewfinder, is reproduced thereon, and is given to an output terminal  47 . 
         [0045]    The control circuit  40  is connected with a memory  42 , a timer  43  that measures date and time, an error LED  44  that emits light in order to notify a user or the like that the optical system constituting the television camera lens  1  fails, and a warning LED  45  that emits light in order to give a warning when failure is highly likely to occur. 
         [0046]      FIG. 2  is a partial sectional view of the zoom optical system  5 .  FIG. 3  is an exploded perspective view of a lens  51  and the like included in the zoom optical system  5 .  FIG. 4  is a rear view of the lens  51  and the like viewed from the side of the imaging element  11 .  FIG. 5  is a plan view illustrating parts constituting a part of a lens moving mechanism that moves the lens  51  and the like in a direction of the optical axis L. 
         [0047]    A lens fixing frame  52 , of which the inner peripheral surface is fixed onto the outer peripheral surface of the lens  51 , is mounted on the outer peripheral surface of the lens  51 . A gear  53  is formed to be closer to the inner side than the outer peripheral surface of the lens fixing frame  52  in a circumferential direction, in a section of the lens fixing frame  52  on the imaging element  11  side (refer to  FIG. 4 ). 
         [0048]    A lens holding frame  56  surrounding the outer periphery of the lens fixing frame  52  is provided. As shown in  FIG. 2 , two flanges  56 B are formed in the direction of the optical axis L with an inner peripheral surface  56 C of the lens holding frame  56  interposed therebetween. The flanges  56 B enables the lens  51  (lens fixing frame  52 ) to rotate about the optical axis L without shift in the direction of the optical axis L relative to the lens holding frame  56 . A ball bearing may be provided between the inner peripheral surface  56 C of the lens holding frame  56  and the outer peripheral surface of the lens fixing frame  52 . The lens  51  smoothly rotates. 
         [0049]    The motor  20 B is fixed onto the lens holding frame  56 , and the gear  54  is fixed onto the shaft of the motor  20 B. The gear  54  engages with the gear  53  of the lens fixing frame  52 . By driving the motor  20 B, the lens fixing frame  52  rotates, and thereby the lens  51  rotates about the optical axis L. 
         [0050]    One end of a plurality of pins  60  is fixed onto the lens holding frame  56 . The other end of these pins  60  is inserted into a guiding groove  61  which is formed in a barrel  62  of the zoom optical system  5 . The guiding groove  61  is formed in the direction of the optical axis L. By moving the pins  60  along the guiding groove  61 , the lens holding frame  56  (lens  51 ) is able to move in the direction of the optical axis L. 
         [0051]    A rack  57 , which protrudes in the direction of the optical axis L, is formed on a part of the lens holding frame  56 . Teeth  57 A formed on the rack  57  engages with a pinion  58 . A shaft of the above-mentioned motor  20 A is fixed onto the pinion  58 . 
         [0052]    Referring to  FIG. 5 , the rack  57  includes a part in which the teeth  57 A are formed and a part  57 B in which the teeth  57 A are not formed. The motor  20 A is disposed on the part  57 B in which the teeth  57 A are not formed. The guiding groove  57 C is formed in the direction of the optical axis L in the part  57 B in which the teeth  57 A are not formed, and a regulation pin (not shown in the drawing), which protrudes downward (downward in  FIG. 2 ) from the motor  20 A, is inserted into the guiding groove  57 C. If the motor  20 A is driven, the pinion  58  rotates, and the rack  57  moves in the direction of the optical axis L. Therefore, the lens  51  also moves in the direction of the optical axis L. The motor  20 A is fixed onto the part  57 B in which the teeth  57 A of the rack  57  are not formed, and is fixed onto the inner peripheral surface of the barrel  62 . The motor  20 A does not move together with the rack  57 , and the lens  51  moves in the direction of the optical axis L. 
         [0053]    The motor  20 A, the pinion  58 , the rack  57 , the lens holding frame  56 , the lens fixing frame  52 , the pins  60 , and the guiding groove  61  constitute the lens moving mechanism that moves the lens  51  in the direction of the optical axis L. The lens moving mechanism may move not a single lens but a plurality of lenses (one or more lenses) in the direction of the optical axis L. Further, the motor  20 B, the gear  54 , the lens fixing frame  52 , and the lens holding frame  56  constitute a lens rotating mechanism that rotates the lens  51  about the optical axis L and can be driven separately from the lens moving mechanism. The lens rotating mechanism, which can be driven separately from the lens moving mechanism, is able to rotate the lens  51  about the optical axis L without being affected by (regardless of) the movement of the lens  51  moved by the lens moving mechanism. 
         [0054]      FIG. 6  is an example of a position/rotation angle table illustrating a relationship between positions of the lens  51  and rotation angles of the lens  51 . 
         [0055]    In this example, the plurality of positions of the lens  51  in the direction of the optical axis L and the plurality of rotation angles respectively corresponding to the plurality of positions are stored in the memory (storage section)  42  as the position/rotation angle table. If the lens  51  is set at the position in the direction of the optical axis L, the lens rotating mechanism rotates the lens  51  about the optical axis L by a rotation angle which is stored in association with the set position. As described above, the lens rotating mechanism can be driven separately from the lens moving mechanism by rotating at least one lens, which is included in the optical system, in the optical axis L of the optical system, by a rotation angle, which corresponds to a position of the lens moved by the lens moving mechanism in the direction of the optical axis L, among the plurality of rotation angles stored in the memory (storage section)  42 . For example, if the lens  51  is set at a position P 1 , the lens  51  is rotated by an angle of θ 1 . It is needless to say that the reference position of the lens  51  in the rotation direction is set and the rotation is performed by the motor  20 B on the basis of the reference position. If necessary, a reference mark is attached to the lens fixing frame  52 , and a sensor detects the mark, whereby the lens  51  can be rotated on the basis of the rotation reference position of the lens  51  and the rotation angle which is determined on the basis of the rotation reference position. 
         [0056]    For example, the position/rotation angle table stores a relationship between the rotation angles and the positions in the direction of the optical axis L such as minimizes (reduces) aberrations by rotating the lens. By rotating the lens in accordance with the set position, aberrations in the television camera lens  1  are reduced. It is needless to say that if there are lenses which are rotated other than the lens  51 , the rotation angle of the lens  51  is determined such that aberration is reduced in consideration of the rotation angles of the other lenses. 
         [0057]    In the above-mentioned example, the lens  51 , which is included in the zoom optical system  5 , is rotated. However, not a lens, which is included in the zoom optical system  5 , but one or more lenses, which are included in the plurality of lenses of the focus optical system  2 , the master optical system  10 , the other optical systems, and the like, may be rotated about the optical axis L in accordance with the position thereof in the direction of the optical axis L. Further, one or more lenses, which are rotated, may be lenses, of which at least one of a lens surface shape or a refractive index is relatively not uniform in a circumferential direction that is orthogonal to the optical axis L and is centered on the optical axis L, among the plurality of lenses included in the television camera lens  1 . It is possible to reduce aberrations and the like which are caused by non-uniformity in the lens surface shape and the refractive index. A degree of non-uniformity may indicate non-uniformity in the circumferential direction as well, and thus whether non-uniformity occurs is detected on the basis of for example a variance value. Further, relatively whether non-uniformity occurs can be determined on the basis of whether the variance value is greater than a median value or an average value in a case where a plurality of lenses included in the television camera lens  1  are arranged in an order of non-uniformity. 
         [0058]    At least one lens rotated by the lens rotating mechanism may be a lens, of which an optical sensitivity (lens power) is relatively low, among the plurality of lenses. It can be determined whether a lens has a relatively low optical sensitivity, on the basis of whether the optical sensitivity is equal to or less than median values or average values of the optical sensitivities of the plurality of lenses included in the television camera lens  1 . 
         [0059]      FIG. 7  is an example of a zoom ratio/amount of variation table that indicates the zoom ratios and the amounts of variation in focal position. This table is also stored in the memory (storage section)  42 . 
         [0060]    The focal position is theoretically fixed regardless of the zoom ratio. However, the focal position is shifted due to the lens surface shape, the processing error, the zoom ratio, and the like (zooming focus shift). In this example, the amount of variation in focal position, which is shifted due to the zoom ratio, is stored in advance, and the amount of variation is adjusted in accordance with the zoom ratio at the time of actually using the television camera lens  1 . 
         [0061]    The zoom ratio corresponds to Z 1 , Z 2 , Z 3 , Z 4 , and the like, the amount of variation in focal position is measured in advance as V 1 , V 2 , V 3 , V 4 , and the like, and those are stored. 
         [0062]      FIG. 8  is an example of the aperture value/amount of variation table that indicates the aperture values and the amounts of variation in focal position. Also, this table is stored in the memory (storage section)  42 . 
         [0063]    Like the zooming focus shift, theoretically, the focal position is fixed regardless of the aperture value. However, in practice, the focal position may be shifted due to the aperture value (stopping focus shift). In this example, the amount of variation in focal position, which is shifted due to the aperture value, is stored in advance, and the amount of variation is adjusted in accordance with the aperture value at the time of actually using the television camera lens  1 . 
         [0064]    In accordance with F 1  (open diaphragm), F 1 . 4 , F 2 , F 2 . 8 , F 4 , and the like as the aperture value, the amount of variation in focal position is measured as V 11 , V 12 , V 13 , V 14 , V 15 , and the like in advance, and those are stored. 
         [0065]      FIG. 9  is an example of a table illustrating the amounts of variation in focal position corresponding to the zoom ratios and the aperture values. This table is also stored in the memory (storage section)  42 . 
         [0066]    As described above, in accordance with the zoom ratios or the aperture values, the amounts of variation in focal position are stored. At the time of using the television camera lens  1 , the amounts of variation may be adjusted. However, the amounts of variation in focal position corresponding to both the zoom ratios and the aperture values may be stored. In the table shown in  FIG. 9 , the amounts of variation are stored. 
         [0067]    The amounts of variation in focal position are stored in the table in association with the set zoom ratios and the set aperture values. The amounts of variation, which are stored in association with the zoom ratios and the aperture values that are set in actual use, are read, and the read amounts of variation are adjusted. More specifically, focal position adjustment can be achieved. 
         [0068]      FIG. 10  is flowchart illustrating a procedure of processing of generating the amounts of variation in focal position in the zoom ratio/amount of variation in focal position table shown in  FIG. 7 . The processing is performed in an ex-factory state of the television camera lens  1 . 
         [0069]    First, the zoom optical system  5  is set at the wide-angle end (step  61 ). A shift A of the focal position at the wide-angle end is detected, and the focal position at the wide-angle end is set as a reference position (step  62 ). If the zoom ratio at the wide-angle end is Z 1 , the shift A of the focal position is equal to the amount of variation in focal position V  1 . The lens included in the zoom optical system  5  is moved in a definition step (step  63 ), and the above-mentioned zoom ratio is set. For example, if the zoom ratio at the wide-angle end is Z 1 , the zoom ratio is set as Z 2 . The amount of variation in focal position Al at the zoom ratio is measured (step  64 ). The amount of variation V 2  at the zoom ratio Z 2  is equal to Δ+Δ 1 . Until the zoom optical system  5  reaches the telephoto end, processing in steps  63  and  64  is repeated (step  65 ). 
         [0070]    Through such processing, it is possible to obtain a table shown in  FIG. 7 . 
         [0071]    The aperture value/amount of variation table shown in  FIG. 8  can also be obtained by measuring the amount of variation in focal position for each aperture value. Further, a table shown in  FIG. 9  can also be obtained by measuring the amount of variation in focal position for each zoom ratio and for each aperture value. 
         [0072]      FIG. 11  is a flowchart illustrating a procedure of processing of adjusting the focal position on the basis of the table shown in  FIG. 7 . 
         [0073]    The zoom optical system  5  is set at the zoom ratio according to the zoom command issued from a user (step  71 ) (the lens included in the zoom optical system  5  is moved in the direction of the optical axis). In this case, it is preferable that, as described above, if the moved lens is a lens that rotates about the optical axis, as shown in  FIG. 6 , the lens is rotated by a rotation angle corresponding to the moved position. 
         [0074]    The amount of variation in focal position corresponding to the set zoom ratio is read from the table shown in  FIG. 7  (step  72 ). From the read amount of variation, an operation ratio between the focal position adjustment performed by the focus optical system  2  and the focal position adjustment performed by the master optical system  10  is determined (step  73 ). For example, the operation ratio is determined as follow: at a position closer to the telephoto end, the amount of adjustment of the focal position based on movement of the focus optical system  2  is larger, and the amount of adjustment of the focal position based on movement of the master optical system  10  is smaller; and at a position closer to the wide-angle end, the amount of adjustment of the focal position based on movement of the focus optical system  2  is smaller, and the amount of adjustment of the focal position based on movement of the master optical system  10  is larger. By moving the focus optical system  2  in a first movement unit, the focal position thereof is adjusted. By moving the master optical system  2  in a second movement unit smaller than the first movement unit, the focal position thereof is adjusted. At a position closer to the telephoto end, the amount of variation in focal position is larger, and thus a percentage of the adjustment of the position adjusted by the focus optical system  2  having a larger movement unit is larger. As a result, it is possible to achieve faster adjustment. Further, at a position closer to the wide-angle end, the amount of variation in focal position is smaller, and thus a percentage of the adjustment of the position adjusted by the master optical system  10  having a smaller movement unit is smaller. As a result, it is possible to achieve more accurate adjustment. With the operation ratio which is determined in such a manner, the control circuit  40  (adjustment control means) performs at least one of the focal position adjustment performed by the focus optical system  2  or the focal position adjustment performed by the master optical system  10  (step  74 ). Through the focal position adjustment, a subject is accurately brought into focus on the light receiving surface of the imaging element  11 . 
         [0075]    Further, only adjustment of the focal position based on movement of the focus optical system  2  may be performed if the zoom ratio is at a telephoto end, or only adjustment of the focal position based on movement of the master optical system  10  is performed if the zoom ratio is at a wide-angle end. 
         [0076]      FIG. 12  is a flowchart illustrating a procedure of processing of adjusting the focal position on the basis of the table shown in  FIG. 8 . 
         [0077]    The diaphragm  6  is set at a desired aperture value of a user (step  81 ). The amount of variation in focal position corresponding to the set aperture value is read from the table shown in  FIG. 8  (step  82 ). From the read amount of variation, an operation ratio between the focal position adjustment performed by the focus optical system  2  and the focal position adjustment performed by the master optical system  10  is determined (step  83 ). For example, the amount of adjustment of the focus optical system  2  is larger if a size of the opening of the diaphragm  6  is closer to a minimum thereof, and thus the amount of adjustment of the master optical system  10  is smaller. The amount of adjustment of the focus optical system  2  is smaller if the size of the opening of the diaphragm  6  is closer to a maximum (a fully opened size) thereof, and thus the amount of adjustment of the master optical system  10  is larger. The amount of variation in focal position is larger if the size of the opening of the diaphragm  6  is closer to the minimum thereof, and thus a percentage of the adjustment of the position adjusted by the focus optical system  2  in a larger movement unit is larger. As a result, it is possible to achieve faster adjustment. Further, the amount of variation in focal position is smaller if the size of the opening of the diaphragm  6  is closer to the maximum thereof, and thus the percentage of the adjustment of the position adjusted by the master optical system  10  in a smaller movement unit is smaller. As a result, it is possible to achieve more accurate adjustment. With the operation ratio which is determined in such a manner, the control circuit  40  (adjustment control means) performs at least one of the focal position adjustment performed by the focus optical system  2  or the focal position adjustment performed by the master optical system  10  (step  84 ). 
         [0078]    In a case of an aperture value at which the opening of the diaphragm  6  is minimized, only the adjustment of the focal position based on the movement of the focus optical system  2  may be performed. In a case of an aperture value at which the opening of the diaphragm  6  is maximized, only the adjustment of the focal position based on the movement of the master optical system  10  may be performed. 
         [0079]      FIG. 13  is a flowchart illustrating a procedure of processing of adjusting the focal position on the basis of the table shown in  FIG. 9 . 
         [0080]    As described above, the zoom optical system  5  is set at a zoom ratio according to the zoom command (step  91 ), and an aperture value, which is desired by a user, is set (step  92 ). The amount of variation in focal position corresponding to the set zoom ratio and the set aperture value is read from the table shown in  FIG. 9  (step  93 ). From the read amount of variation, the operation ratio between the focal position adjustment performed by the focus optical system  2  and the focal position adjustment performed by the master optical system  10  is determined (step  94 ). In this determination method, in a manner similar to that of the above description, the operation ratio between the focus optical system  2  and the master optical system  10  is determined as follows. At a position closer to the telephoto end, the amount of adjustment of the focus optical system  2  is larger, and the amount of adjustment of the master optical system  10  is smaller. At a position closer to the wide-angle end, the amount of adjustment of the focus optical system  2  is smaller, and the amount of adjustment of the master optical system  10  is larger. Further, if the size of the opening of the diaphragm  6  is closer to the minimum thereof, the amount of adjustment of the focus optical system  2  is larger, and the amount of adjustment of the master optical system  10  is smaller. If the size of the opening of the diaphragm  6  is closer to the maximum (a fully opened size) thereof, the amount of adjustment of the focus optical system  2  is smaller. 
         [0081]    In this case, if the zoom ratio is at the telephoto end, only the adjustment of the focal position based on the movement of the focus optical system  2  may be performed regardless of the aperture value, and if the zoom ratio is at the telephoto end, only the adjustment of the focal position based on the movement of the focus optical system  2  may be performed in a case where the size of the opening of the diaphragm  6  is at the minimum. Further, in the case where the size of the opening of the diaphragm  6  is at the minimum, only the adjustment of the focal position based on the movement of the focus optical system  2  may be performed regardless of the zoom ratio. Likewise, if the zoom ratio is at the wide-angle end, only the adjustment of the focal position based on the movement of the master optical system  10  may be performed regardless of the aperture value, and if the zoom ratio is at the wide-angle end, only the adjustment of the focal position based on the movement of the master optical system  10  may be performed in a case where the size of the opening of the diaphragm  6  is at the maximum. Further, in the case where the size of the opening of the diaphragm  6  is at the maximum, only the adjustment of the focal position based on the movement of the master optical system  10  may be performed regardless of the zoom ratio. With the operation ratio which is determined in such a manner, the control circuit  40  (adjustment control means) performs at least one of the focal position adjustment performed by the focus optical system  2  or the focal position adjustment performed by the master optical system  10  (step  95 ). 
         [0082]    In a case of capturing an image of a subject which is moving, focusing is performed by the focus optical system  2  while a zooming operation is performed by the zoom optical system  5 . In a case where the movement of the subject is slow, the focus optical system  2  is controlled such that the amount of variation in focal position is added to (subtracted from) the focal position of the focus optical system  2  obtained without consideration of the amount of variation in focal position. It is possible to accurately bring a subject into focus. In a case where the movement of the subject is fast, the focus optical system  2  is controlled to be at the focal position of the focus optical system  2  obtained without consideration of the amount of variation in focal position. Thereby, it is possible to promptly bring the subject into focus. Thereafter, the focus optical system  2  is controlled to be at the focal position to which the amount of variation in focal position is added. 
         [0083]    In the above-mentioned example, the adjustment is performed using the focus optical system  2  and the master optical system  10  so as to obtain a focal position by adding (subtracting) the amount of variation in focal position to (from) the focal position as a reference which is obtained without consideration of the amount of variation in focal position. However, if the focal position to (from) which the amount of variation in focal position was added (subtracted) is set as a reference, the focal position to (from) which the amount of variation in focal position was added (subtracted) may be used. For example, referring to  FIG. 7 , in a case where the zoom ratio is set as Z 2 , the amount of variation in focal position is V 2 . Therefore, the focus optical system  2  and the master optical system  10  are controlled such that the focal position is adjusted by the amount of variation V 2  from the focal position calculated in a case where the amount of variation in focal position is not considered. However, in a case where the zoom ratio is changed from Z 2  to Z 3 , the focal position may be adjusted by an amount of V 3 −V 2  which is a difference between the amounts of variation in focal position. Therefore, the amount of adjustment may be small. In such a case, only the master optical system  10  may be used. It is possible to accurately perform fine adjustment. 
         [0084]    By performing a routine such as a correction mode for measuring the focal position for each zoom ratio or each aperture value, it is possible to check a current amount of variation. By comparing the current amount of variation with the amount of variation (the amount of variation of the initial value) stored in advance, it is possible to diagnose a current driving state of the television camera lens  1 . In a system in which an amount of correction in reciprocation is stored, hysteresis characteristics between the focus optical system  2  and the master optical system  10  are compared. ‘Therefore, it is possible to quantitatively capture the amount of backlash by the cam. Further, in a case where the difference between the current amount of variation and the amount of variation of the initial value is greater than a threshold value, it is determined that failure occurs. For example, this configuration can also be applied to determination as to whether the television camera lens  1  fails.