Abstract:
To provide a lens device involving simple adjustment work and an adjustment method for the same, the lens device includes the first and second lens groups, each including having a retaining guide section on a surface facing another of the first and second lens groups, wherein the retaining guide section of one of the first and second lens groups retains and guides the other of the first and second lens groups so that the other of the first and second lens groups can rotate around the optical axis in the rotary cylinder.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a lens device which comprises a plurality of lens groups built in a rotary cylinder and which moves the lens groups in the direction of an optical axis by means of rotation of the rotary cylinder, as well as to an improvement in a method for adjusting the lens device. 
   BACKGROUND OF THE INVENTION 
   A zoom lens device which enables acquisition of different focal distances through use of a single lens device has hitherto been used in an optical product, such as a camera or a projector. For instance, as described in JP-A-11-326734, JP-A-2000-321476 and JP-A-2003-202479, a plurality of lens groups are built in a lens barrel, and the lens groups are moved along the direction of the optical axis, thereby effecting scaling action and focusing. 
   Each of the lens groups is constituted of at least one lens, and an annular lens support frame for supporting the lens. For example, three bosses are provided upright on an outer periphery of the lens support frame while being radially spaced at uniform angular intervals of 120°, and a columnar cam follower is attached to each of the bosses. The lens barrel is formed from a zoom cam cylinder and a fixed cylinder. A plurality of curved cam grooves into which the cam followers of the respective lens groups are inserted are formed in the zoom cam cylinder, and a plurality of linear cam grooves aligned with the direction of the optical axis are formed in the fixed cylinder. When the zoom cam cylinder is rotated, the cam followers are pressed by the curved cam grooves, whereupon the respective lens groups are moved in the direction of a projecting optical axis along the linear cam grooves of the fixed cylinder. 
   The zoom cam cylinder and the lens support frame are formed from plastic by means of injection molding or the like. Slight, rather than great, variations arise in positions of a molded article where the cam grooves or the cam followers are to be formed. For these reasons, there sometimes arises a case where lens groups built in the lens barrel become tilted with reference to the projection optical axis, or a case where the center of the lenses comes out of alignment with the projection optical axis. The related-art zoom lens device is subjected to inspection after the lens groups have been incorporated in the lens barrel. In accordance with the result of inspection, the lens groups in the lens barrel are rotated through an angle at which the cam followers are spaced from each other around the projection optical axis; that is, an angle of 120°, thereby changing a combination of the cam grooves and the cam followers. Thus, the tilt of the lens groups with reference to the projection optical axis is adjusted. 
   However, in the case of the zoom lens device wherein, e.g., three bosses and cam followers are provided upright on the outer periphery of the lens support frame while being radially spaced apart at a uniform angular interval of 120° and wherein the lens support frame is supported by the lens barrel by means of the bosses, the three bosses attached to the lens group must once be removed to rotate the lens group by the amount corresponding to the pitch between the cam followers. In that case, unless the lens group is pressed by a jig or the like, the lens group will fall. For this reason, when the center lens group in the zoom lens device into which three or more lens groups are built is subjected to rotational adjustment, the outer lens groups must be removed from the lens barrel for inserting a jig or the like, thereby deteriorating working efficiency. 
   SUMMARY OF THE INVENTION 
   The present invention is intended for resolving the above-described drawback, and an object of the present invention is to providing a lens device involving simple adjustment operation and an adjustment method. 
   A lens device of the present invention is provided with a retaining guide section on a lens support frame constituting a lens group. The retaining guide section retains a lens support frame of an adjacent lens group and guides the lens group so as to allow rotation of the adjacent lens group around a projection optical axis. 
   A lens adjustment method of the present invention includes: bringing first and second lens groups in close contact with each other in a direction of an optical axis; removing cam followers from one lens group (e.g. the first lens group) requiring adjustment through cam grooves; retaining the one lens group, which cam followers have been removed, by means of the retaining guide section of the other lens group (e.g. the second lens group); rotating the one lens group within the rotary cylinder by the amount corresponding to a pitch between the cam followers; and again attaching the cam followers to the one lens group. 
   According to a lens device and a lens adjustment method of the present invention, when, for example, a combination of cam followers of a center lens group with cam grooves in a lens device having three or more lens groups requires adjustment, the center lens group can be rotated around the projection optical axis within the rotary cylinder without removing the outer lens group from the rotary cylinder. As a result, the efficiency of adjustment work is improved. Moreover, during assembly of the lens device, another lens group can be incorporated while the first-inserted lens groups are taken as guides, and therefore efficiency of assembly work can also be improved. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic diagram showing the configuration of a projector; 
       FIG. 2  is a cross-sectional view of a zoom lens device in an embodiment of the present invention; 
       FIG. 3  is an appearance perspective view showing a convex retaining guide section of a lens group C and a concave retaining guide section of a lens group D in an embodiment of the present invention; 
       FIGS. 4A and 4B  are cross-sectional views of the principal section showing engagement between the convex retaining guide section of the lens group C and the concave retaining guide section of the lens group D in an embodiment of the present invention; and 
       FIG. 5  is a flowchart showing procedures of a method for adjusting the zoom lens device in an embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  is a schematic diagram showing the configuration of a projector using a lens device of the present invention. A projector  2  is a translucent liquid-crystal projector constituted of a zoom lens device  3 , a translucent liquid-crystal panel  4 , and an illumination lamp  5 . On the basis of an input video signal, an image is displayed on the translucent liquid-crystal panel  4 . The illumination lamp  5  emits illumination light on the translucent liquid-crystal panel  4  from behind. The illumination light having passed through the liquid-crystal panel  4  is projected on a screen by means of the zoom lens device  3 , whereby the image is displayed. 
     FIG. 2  is a cross-sectional view of the principal section showing the configuration of the zoom lens device  3  in an embodiment of the present invention. An adjustment state used for adjusting the zoom lens device  3  is shown above a projection optical axis (i.e., an optical axis)  6 , and a telescopic state of the zoom lens device  3  is shown below the projection optical axis  6 . The zoom lens device  3  has, as an optical system, a lens group A ( 8 ) acting as a focus lens; a lens group B ( 9 ) acting as a variator; lens groups C and D ( 10 ,  11 ) acting as a compensator; and a lens group E ( 12 ) acting as a release lens. The lens groups  8  to  12  comprise a plurality of lenses  8   a  to  12   a  and annular lens support frames  8   b  to  12   b  for supporting the lenses  8   a  to  12   a.    
   The lens group A ( 8 ) to the lens group D ( 11 ) are built in a fixed cylinder  15 . A rectangular flange  16  used for fixing the zoom lens device  3  within the projector  2  is formed integrally at the rear end of the fixed cylinder  15 . The lens support frame  12   b  of the lens group E ( 12 ) is mounted on the back of the flange  16 . Attached on an upper part of the flange  16  are a focus motor  17  for moving the lens group A ( 8 ) in the direction of the projection optical axis  6 ; a zoom motor  18  for moving the lens groups B to D ( 9  to  11 ) in the direction of the optical axis  6 ; and a gear box  21  for transmitting rotation of the motors  17 ,  18  to a focus link gear  19  and a zoom link gear  20 . 
   A female helicoid is formed on an inner periphery of the extremity of the fixed cylinder  15 , and a male helicoid is formed on an outer periphery of the extremity of the lens support frame  8   b  of the lens group A ( 8 ). Therefore, when the lens group A ( 8 ) is rotated, the lens group A ( 8 ) advances or recedes in the direction of the optical axis by means of a lead of the helicoids, thereby adjusting a focus. The lens group A ( 8 ) is rotated by means of a focus cylinder fixed to the outside of the lens support frame  8   b ; the focus ring gear  19  which is attached to the rear end of a focus cylinder  24  and rotates along the outer periphery of the fixed cylinder  15 ; and the focus motor  17  which rotates the focus link gear  19  by way of the gear box  21 . 
   A rotary cylinder  27  which rotates along the outer periphery of the fixed cylinder  15  is interposed between the fixed cylinder  15  and the focus cylinder  24 . The zoom link gear  20  is latched at the rear end of the rotary cylinder  27 , and rotation of the zoom motor  18  is transmitted to the zoom link gear  20  by way of the gear box  21 . 
   Cam followers  30  to  32 , which are radially provided on the outer peripheries of the lens support frames  9   b  to  11   b  of the lens groups B to D ( 9  to  11 ) while being spaced apart from each other at uniform pitches on the respective outer peripheries, are inserted into a linearly-advancement cam groove  33  formed in the outer peripheral surface of the fixed cylinder  15 . Three of zoom cam grooves  34  to  36  into which are to be inserted the respective cam followers  30  to  32  of the lens groups B to D ( 9  to  11 ) projecting from the linearly-advancement cam are formed, each in a number of three, in the outer peripheral surface of the rotary cylinder  27 . 
   The zoom cam grooves  34  to  36  are formed on the outer periphery of the projection optical axis  6  in an essentially helical pattern. The cam followers  30  to  32  of the lens groups B to D ( 9  to  11 ) are pressed by rotation of the rotary cylinder  27 , thereby moving the lens groups B to D ( 9  to  11 ) in the direction of the projection optical axis  6 . The linearly-advancement cam groove  33  is formed along the direction of the projection optical axis  6  and acts as a translatory-moving guide for effecting regulation such that the respective cam followers  30  to  33  move in only the direction of the optical axis  6 . 
   As shown in  FIGS. 3 and 4A , the cam followers  31  of the lens group C ( 10 ) comprise three bosses  39  formed on the outer periphery of the lens support frame  10   a  so as to be spaced from each other at uniform angular intervals. Each of the cam followers  31  further comprises a sleeve  41  fixed on the boss  39  by means of a screw  40 , and a cam roller  42  rotatably held between the sleeve  41  and the screw  40 . The cam roller  42  rotates within the linearly-advancement cam groove  33  and the zoom cam groove  35 , thereby reducing resistance that arises during sliding action. Since the cam followers  30 ,  32  of the lens group B ( 9 ) and the lens group D ( 11 ) assume the same configuration, their detailed explanations are omitted. 
   A circular convex retaining guide section  45  projecting toward the lens group D ( 11 ) is formed on a surface of the lens support frame  10   a  of the lens group C ( 10 ), the surface facing to the lens group D ( 11 ). A circular concave retaining guide section  46  formed from a circular depression is formed on a surface of the lens support frame  11   a  of the lens group D ( 11 ), the surface facing to the lens group C ( 10 ). The diameter of the convex retaining guide section  45  and that of the concave retaining guide section  46  are determined so as to gently fit together to such an extent that the lens support frames can mutually rotate. 
   As shown in  FIG. 2 , when the zoom lens device  3  is brought into a state where the lens device has been moved further toward the wide side than the wide end, the lens group C ( 10 ) and the lens group D ( 11 ) are moved toward the rear end of the zoom lens device  2 . Moreover, the convex retaining guide section  45  of the lens group C ( 10 ) is inserted into the concave retaining guide section  46  of the lens group D ( 11 ). 
   For instance, the zoom lens device  3  remaining in the adjusted state is brought into an upright position such that the lens group A ( 8 ) is oriented upward. As shown in  FIG. 4B , as a result of the cam followers  31  of the lens group C ( 10 ) being removed from the lens support frame  10   a , the lens group C ( 10 ) is retained by the concave retaining guide section  46  of the lens group D ( 11 ). Further, the convex retaining guide section  45  and the concave retaining guide section  46  are formed into a circular shape. Hence, the fixed cylinder  15  and the lens group C ( 10 ) in the rotary cylinder  27  can be rotated from the outside by use of a jig or the like. 
   During the process for adjusting the zoom lens device  3 , when the combination of the cam followers  31  of the lens group C ( 10 ) with the cam groove  35  is changed, only the lens group C ( 10 ) can be rotated within the fixed cylinder  15  and the rotary cylinder  27  without removal of the lens group A ( 8 ), the lens group B ( 9 ), the lens group D ( 11 ), and the lens group E ( 12 ), to thus enhance efficiency of adjustment work. When the zoom lens device  3  is brought into an upright position such that the lens group A ( 8 ) is oriented downward, the lens group D( 11 ) can be retained by the lens group C ( 10 ). Hence, similarly, work for adjusting the lens group D ( 11 ) can also be simplified. 
   Next, a method for adjusting the zoom lens device  3  will be described by reference to a flowchart shown in  FIG. 5 . The zoom lens device  3  having finished undergone assembly is set on inspection equipment. In addition to performing tests for the focus and zoom of the lens groups A to E ( 8  to  12 ), this inspection equipment performs tests for alignment of the centers of the lenses  8   a  to  12   a  of the lens groups A to E ( 8  to  12 ) with the center of the projection optical axis  6  and tests as to whether or not the lens groups A to E ( 8  to  12 ) are inclined with reference to the projection optical axis  6 . 
   When the centers of the lenses of the lens groups are out of alignment with the center of the projection optical axis or when the lens groups are incorporated at an angle to the projection optical axis  6 , variations are considered to exist in the manufacturing accuracy of the cam followers of the lens groups or that of the zoom cam groove of the rotary cylinder  27 . In such an event, there may be a case where the lens can be properly adjusted by changing the combination of the cam followers with the zoom cam groove. 
   For instance, when the lens group C ( 10 ) is mounted at an angle to the projection optical axis, the zoom lens device  3  is set in an adjustment state, as shown in  FIGS. 2 and 4A , thereby bringing the lens groups C and D ( 10 ,  11 ) into close contact with each other. As a result, the convex retaining guide section  45  of the lens group C ( 10 ) is inserted into the concave retaining guide section  46  of the lens group D ( 11 ). 
   As shown in  FIG. 4B , the zoom lens device  3  is brought into an upright position such that the lens group A ( 8 ) faces upward, and the cam followers  31  are removed from the lens support frame  10   a  through the linearly-advancement cam groove  33  and the zoom cam groove  35 . The lens group C ( 10 ) is retained by the lens group D ( 11 ) by means of engagement of the convex retaining guide section  45  with the concave retaining guide section  46 , and is guided so as to be able to rotate around the projection optical axis  6 . 
   In this state, when the lens group C ( 10 ) is rotated by one pitch between the cam follower  31  from the outside of the fixed cylinder  15  and the rotary cylinder  27  through use of a jig or a tool, the bosses  39  of the lens support frame  10   b  again face the linearly-advancement cam groove  33  and the zoom cam groove  35 . Therefore, when the cam followers  31  are again attached, the combination of the cam followers  31  with the zoom cam groove  35  can be easily changed without involvement of disassembly of the zoom lens device  3 , so that the zoom lens device  3  can be adjusted to an appropriate state. 
   In the previous embodiment, only the lens groups C and D ( 10  and  11 ) are provided with the retaining guide sections. However, all the lens groups may be provided with the retaining guide sections. Further, although the zoom lens device of the projector has already been described as an example, the present invention can also be applied to a lens device of a camera or that of an optical instrument. 
   It will be apparent to those skilled in the art that various modifications and variations can be made to the described preferred embodiments of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover all modifications and variations of this invention consistent with the scope of the appended claims and their equivalents. 
   The present application claims foreign priority based on Japanese Patent Application No. JP2004-105507, filed Mar. 31 of 2004, the contents of which is incorporated herein by reference.