Abstract:
A lens barrel includes a lens that has a plurality of sliding surfaces on an outer peripheral edge of the lens; and a lens frame that has a plurality of lens-receiving sections on an inner peripheral edge of the lens frame and accommodates the lens. The sliding surfaces have different heights in a direction perpendicular to an optical axis of incident light. Each of the lens-receiving sections comes in contact with one of the sliding surfaces.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1) Field of the Invention  
           [0002]    The present invention relates to a lens barrel capable of moving and adjusting, in an optical axis, a lens frame of a lens that is an image enlarging unit used for a projector, a moving-picture machine and the like.  
           [0003]    2) Description of the Related Art  
           [0004]    [0004]FIG. 14 is a sectional view illustrating a partial configuration of a conventional image enlarging lens barrel used for the projector, the moving-picture machine and the like. The image enlarging lens comprises a plurality of lenses in many cases. FIG. 14 shows a first group of the image enlarging lens.  
           [0005]    This first lens group includes a first lens  1 , a second lens  2  and a third lens  3  which are disposed in this order from the side closer to an image (not shown). These lenses are held by a lens frame  4 . In order to form an image (size, focus, and the like) which is most suitable for a screen size to be projected, a washer  6  having a predetermined thickness is inserted between the second lens  2  and a second lens-holding section  5  of a lens frame  4  which holds the second lens  2 , and distances between the second lens  2 , the first lens  1  and the third lens  3  are adjusted. Such a conventional image enlarging lens barrel is disclosed in, for example, Japanese Utility Model No. H7-36332 and Japanese Patent Application Laid-open No. H8-136792.  
           [0006]    An adhesive is used for fixing the second lens  2  to the second lens-holding section  5  shown in FIG. 14. When the washer  6  (see FIG. 11) is inserted to adjust the distance between the second lens  2  and the second lens-holding section  5 , the adhesive is used at two locations, i.e., a location between the second lens  2  and the washer  6  and a location between the second lens-holding section  5  and the washer  6 . When a plurality of washers  6  are to be used, it is also necessary to adhere the washers  6  to each other. In the conventional technique as described above, a position of the second lens  2  is adjusted utilizing the thickness of the washers  6  which are laminated in the direction of the optical axis, and front and back surfaces of the washers  6  are adhered and fixed to each other using the adhesive.  
           [0007]    In such an image enlarging lens, however, if a position of the second lens  2  having a function as an adjusting lens is deviated even slightly, an image which is most suitable for a screen size to be projected (e.g., focus and size with respect to the screen size) can not be formed. If the adhesive is used at many locations, the second lens  2  is moved toward the washer  6  due to change with time (e.g., change in temperature and the like) at the adhered location and the position of the second lens  2  with respect to the direction of the optical axis is deviated.  
           [0008]    When the washer  6  is used for adjusting the second lens  2  in the direction of the optical axis, it is necessary to insert the washer  6 , this increases the operation steps, and the productivity and operation efficiency of the image enlarging lens are deteriorated. The washer  6  is formed by stamping a plate, and the washer  6  must have an outward shape corresponding to an inner diameter size of the barrel and having a thickness corresponding to a distance required for adjusting and moving the lens. Therefore, especially when it is necessary to use the plurality of washers  6 , there is a problem that the number of the washers  6  and the producing cost are increased.  
         SUMMARY OF THE INVENTION  
         [0009]    It is an object of the present invention to at least solve the problems in the conventional technology.  
           [0010]    A lens barrel according to one aspect of the present invention includes a lens that has a plurality of sliding surfaces on an outer peripheral edge of the lens; and a lens frame that has a plurality of lens-receiving sections on an inner peripheral edge of the lens frame and accommodates the lens. The sliding surfaces have different heights in a direction perpendicular to an optical axis of incident light. Each of the lens-receiving sections comes in contact with one of the sliding surfaces.  
           [0011]    A lens barrel according to another aspect of the present invention includes a lens that has a plurality of slanting surfaces on an outer peripheral edge of the lens; and a lens frame that has a plurality of engaging sections on an inner peripheral edge of the lens frame and accommodates the lens. The heights of the slanting surfaces gradually change in a direction perpendicular to an optical axis of incident light. Each of the engaging sections engages with one of the sliding surfaces.  
           [0012]    The other objects, features and advantages of the present invention are specifically set forth in or will become apparent from the following detailed descriptions of the invention when read in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1A and FIG. 1B are sectional views illustrating one example of a configuration of a lens barrel according to a first embodiment;  
         [0014]    [0014]FIG. 2 is a sectional view illustrating a partial configuration of the lens barrel of the first embodiment;  
         [0015]    [0015]FIG. 3A to FIG. 3C illustrate a shape of a second lens used for the lens barrel of the first embodiment;  
         [0016]    [0016]FIG. 4A and FIG. 4B illustrate a partial configuration of a first lens frame of the lens barrel of the first embodiment;  
         [0017]    [0017]FIG. 5A to FIG. 5C illustrate a shape of a second lens used for a lens barrel of a second embodiment;  
         [0018]    [0018]FIG. 6A and FIG. 6B illustrate a partial configuration of a first lens frame of the lens barrel of the second embodiment;.  
         [0019]    [0019]FIG. 7A and FIG. 7B illustrate a shape of a second lens used for a lens barrel of a third embodiment;  
         [0020]    [0020]FIG. 8A and FIG. 8B illustrate a partial configuration of a first lens frame of the lens barrel of the third embodiment;  
         [0021]    [0021]FIG. 9A and FIG. 9B illustrate a shape of a second lens used for a lens barrel of a fourth embodiment;  
         [0022]    [0022]FIG. 10A and FIG. 10B illustrate a partial configuration of a first lens frame of the lens barrel of the fourth embodiment;  
         [0023]    [0023]FIG. 11 illustrates a partial configuration of a lens barrel of a fifth embodiment;  
         [0024]    [0024]FIG. 12A to FIG. 12C illustrate a shape of a second lens used for a lens barrel of the fifth embodiment;  
         [0025]    [0025]FIG. 13A and FIG. 13B illustrate a partial configuration of a first lens frame of the lens barrel of the fifth embodiment; and  
         [0026]    [0026]FIG. 14 is a sectional view illustrating a partial configuration of a conventional image enlarging lens barrel. 
     
    
     DETAILED DESCRIPTION  
       [0027]    Exemplary embodiments of a lens barrel of the invention will be explained in detail with reference to the accompanying drawings below. An optical axis S is shown at necessary locations in the drawings. FIG. 1A and FIG. 1B are sectional views illustrating one example of a configuration of the lens barrel according to a first embodiment.  
         [0028]    In the lens barrel of the embodiment, a first lens group  10 , a second lens group  20  and a third lens group  30  are disposed in this order from the side closer to an image (not shown). The first lens group  10 , the second lens group  20  and the third lens group  30  are held by a first lens frame  40 , a second lens frame  50  and a third lens frame  60 , respectively. The second lens frame  50  holds the second lens group  20  through a lens-holding member  51 . The third lens frame  60  is inserted into the second lens frame  50 . The second lens frame  50  is inserted in to a connection cylinder  61 , and is connected to the first lens frame  40  through the connection cylinder  61 .  
         [0029]    The second lens frame  50  and the connection cylinder  61  are accommodated in a lens-holding frame  62 . The first lens group  10  includes a first lens  1 , a second lens  120  and a third lens  3  which are disposed in this order from the side closer to an image (not shown).  
         [0030]    Each the lens constituting the lens barrel of this embodiment is made of synthetic resin. Therefore, the lens including its later-described sliding surface can easily and inexpensively be formed.  
         [0031]    [0031]FIG. 2 is a sectional view illustrating a partial configuration of the lens barrel of this embodiment. FIG. 2 shows a state in which the first lens group  10  comprising the first lens  1 , the second lens  120  and the third lens  3  arranged in this order from the side closer to the image (not shown) is held by the first lens frame  40 . The first lens frame  40  is formed with a holding section  41  which holds the second lens  120 . The holding section  41  is formed with a lens-receiving section  42  for fixing the second lens  120 .  
         [0032]    In the first embodiment, in order to fix the second lens  120  to the lens-receiving section  42 , a periphery of a right side surface (side surface closer to a film) of the second lens  120  is formed with a step  121  along a thickness direction of the lens. The step  121  is provided with a sliding surface  122  which comes in contact with a lens-receiving section  42 . The sliding surface  122  is formed with a reference surface  122   a  and adjusting surfaces  122   b  and  122   c . Each of the reference surface  122   a  and the adjusting surfaces  122   b  and  122   c  is perpendicular to the optical axis.  
         [0033]    [0033]FIG. 3A to FIG. 3C illustrate a shape of the second lens  120 . FIG. 3A is a plan view of the second lens  120 , FIG. 3B is a left side view of FIG. 3A, and FIG. 3C is a right side view of FIG. 3A. The right side surface (side surface closer to a film) of the second lens  120  is formed with a region which equally divided is into four such that a central angle becomes 90°. The sliding surface  122  of the step  121  in each region is formed with the reference surface  122   a , the adjusting surface  122   b  which is formed into a convex shape by the reference surface  122   a  and the adjusting surface  122   c  which is formed into a concave shape by the reference surface  122   a.    
         [0034]    The adjusting surface  122   b  is higher than the reference surface  122   a  by about {fraction (1/100)} to {fraction (2/100)} millimeter, and the adjusting surface  122   c  is lower than the reference surface  122   a  by about {fraction (1/100)} to {fraction (2/100)} millimeter. Positions of the reference surfaces  122   a  and the adjusting surfaces  122   b  and  122   c  formed in the divided regions are the same.  
         [0035]    A left side surface of the second lens  120  is also formed with a step  124 . Marks  125  as indices showing, with numerical values, heights of the reference surface  122   a  and the adjusting surfaces  122   b  and  122   c  formed on the right side surface are indicated at positions corresponding to these surfaces. The numerical values includes “±0” corresponding to the reference surface  122   a, “+ 0.1” corresponding to the adjusting surface  122   b , and “−0.1” corresponding to the adjusting surface  122   c.    
         [0036]    [0036]FIG. 4A and FIG. 4B illustrate a partial configuration of the first lens frame  40  of the lens barrel according to the first embodiment. FIG. 4A is a plane view illustrating the partial configuration of the first lens frame  40 , and FIG. 4B is a left side view of FIG. 4A. The first lens frame  40  is formed with the holding section  41  which holds the second lens  120 . The holding section  41  is formed at its four locations with lens-receiving sections  42  for fixing the second lens  120 . The lens-receiving section  42  has a surface perpendicular to the optical axis. Therefore, even if the second lens  120  is rotated around the optical axis, a relation between the lens and the optical axis is not changed.  
         [0037]    The first lens frame  40  is formed with a confirmation index  44  so as to grasp or find out which one of the surfaces (one of the reference surface  122   a , the adjusting surface  122   b  and the adjusting surface  122   c ) of the sliding surface  122  formed on the right side surface of the second lens  120  is in contact with the lens-receiving section  42  of the first lens frame  40 . Therefore, it is possible to grasp which one of the surfaces of the sliding surface  122  formed on the second lens  120  is in contact with the lens-receiving section  42  of the first lens frame  40  by referring to the mark  125  of the second lens  120  located at a position of the confirmation index  44 .  
         [0038]    For example, the numerical value “±0” of the mark  125  of the second lens  120  is located at the position of the confirmation index  44  as viewed from front side of the optical axis, and it is possible to easily judge that the reference surface  122   a  of the sliding surface  122  is in contact with the lens-receiving section  42 . In addition, when the second lens  120  is adjusted with respect to the optical axis, the. adjusting direction can easily be judged.  
         [0039]    In this lens barrel, the second lens  120  is rotated around the optical axis in a state in which the sliding surface  122  of the second lens  120  is in contact with the lens-receiving section  42  of the first lens frame  40 , thereby moving the second lens  120  in the direction of the optical axis to position the second lens  120 . Then, the lens-receiving section  42  and the sliding surface  122  are fixed to each other. The adhesive or the like is used for fixing them. Since the adhesive is used on one location between the lens-receiving section  42  and the sliding surface  122 , deviation therebetween in the optical axis caused by the change with time can be minimized.  
         [0040]    According to the lens barrel of the first embodiment, the second lens  120  is provided with the sliding surface  122  having the different height from that perpendicular to the direction of the optical axis, and the sliding surface  122  is brought in contact with the lens-receiving section  42 . Therefore, the second lens  120  can be moved and adjusted in the direction of the optical axis only by rotating the second lens  120 , and the operation step required for this adjustment can be simplified. Since the second lens  120  can be varied in a quantitative manner in the direction of the optical axis, it is possible to easily adjust (finely adjust) the focus of the image enlarging lens.  
         [0041]    A second embodiment is a modification of the lens barrel shown in the first embodiment. FIG. 5A to FIG. 5C illustrate a shape of the second lens used for the lens barrel in the second embodiment. FIG.  5 A is a plan view of a second lens  220 , Fig:  5 B is a left side view of FIG. 5A, and FIG. 5C is a right side view of FIG. 5A. As shown in FIG. 5A to FIG. 5C, in the second embodiment, a right side surface (side surface closer to a film) of the second lens  220  is formed with a region which is equally divided into three such that the central angle becomes 120°. Like the first embodiment, each the divided region is formed with a step  221 . The step  221  is formed with a sliding surface  222 . The sliding surface  222  comprises a reference surface  222   a , an adjusting surface  222   b  which is formed into a convex shape by the reference surface  222   a  and an adjusting surface  222   c  which is formed into a concave shape by the reference surface  222   a.    
         [0042]    The adjusting surface  222   b  is higher than the reference surface  222   a  by about {fraction (1/100)} to {fraction (2/100)} millimeter, and the adjusting surface  222   c  is lower than the reference surface  222   a  by about {fraction (1/100)} to {fraction (2/100)} millimeter. Positions of the reference surfaces  222   a  and the adjusting surfaces  222   b  and  222   c  formed in the divided regions are the same.  
         [0043]    A left side surface of the second lens  220  is also formed with a step  224 . Marks  225  showing heights of the reference surface  222   a  and the adjusting surfaces  222   b  and  222   c  formed on the right side surface are indicated at positions corresponding to these surfaces. The numerical values includes “(0” corresponding to the reference surface  222   a, “+ 0.1” corresponding to the adjusting surface  222   b , and “−0.1” corresponding to the adjusting surface  222   c.    
         [0044]    [0044]FIG. 6A and FIG. 6B illustrate a partial configuration of the first lens frame  70  of the lens barrel according to the second embodiment. FIG. 6A is a plane view illustrating the partial configuration of the first lens frame  70 , and FIG. 6B is a left side view of FIG. 6A. The first lens frame  70  is formed with the holding section  71  which holds the second lens  220 . The holding section  71  is formed at its three locations with lens-receiving sections  72  for fixing the second lens  220 . The lens-receiving section  72  has a surface perpendicular to the optical axis.  
         [0045]    The number of each of the sliding surfaces  222  and the lens-receiving sections  72  is three which is minimum number which holds the second lens  220 . Therefore, even if the second lens  220  is rotated around the optical axis, the relation between the lens and the optical axis is not changed, and it is possible to stably adjust and hold the fixed state of the lens.  
         [0046]    The first lens frame  70  is formed with a confirmation index  74  so as to grasp or find out which one of the surfaces (one of the reference surface  222   a , the adjusting surface  222   b  and the adjusting surface  222   c ) of the sliding surface  222  formed on the right side surface of the second lens  220  is in contact with the lens-receiving section  72  of the first lens frame  70 . Therefore, it is possible to grasp which one of the surfaces of the sliding surface  222  formed on the second lens  120  is in contact with the lens-receiving section  72  of the first lens frame  70  by referring to the mark  225  of the second lens  220  located at a position of the confirmation index  74 .  
         [0047]    For example, the numerical value “±0” of the mark  225  of the second lens  220  is located at the position of the confirmation index  74  as viewed from front side of the optical axis, and it is possible to easily judge that the reference surface  222   a  of the sliding surface  222  is in contact with the lens-receiving section  72 . In addition, when the second lens  220  is adjusted with respect to the optical axis, the adjusting direction can easily be judged.  
         [0048]    According to the lens barrel of the second embodiment, the second lens  220  is provided with the sliding surface  222  having the different height from that perpendicular to the direction of the optical axis, and the sliding surface  222  is brought in contact with the lens-receiving section  72 . Therefore, the second lens  220  can be moved and adjusted in the direction of the optical axis only by rotating the second lens  220 , and the operation step required for this adjustment can be simplified. Since the second lens  220  can be varied in a quantitative manner in the direction of the optical axis, it is possible to easily adjust (finely adjust) the focus of the image enlarging lens. In addition, the number of each of the lens-receiving sections  72  and the sliding surfaces  222  is three which is minimum number for holding them on the circumference. Therefore, it is easy to form these members and it is possible to adjust and hold the second lens  220  in a most stable state.  
         [0049]    A third embodiment of this invention will be explained next. The third embodiment is also a modification of the lens barrel shown in the first embodiment. FIG. 7A and FIG. 7B illustrate a shape of the second lens  320  used for the lens barrel in the third embodiment. FIG. 7A is a plan view of the second lens  320 , and FIG. 7B is a right side view of FIG. 7A. A right side surface (side surface closer to a film) of the second lens  320  is formed with a region which is equally divided into four such that the central angle becomes 90(. Each region has a step  321  including a sliding surface  322 . The sliding surface  322  is formed with a reference surface  322   a , an adjusting surface  322   b  which is formed into a convex shape by the reference surface  322   a  and an adjusting surface  322   c  which is formed into a concave shape by the reference surface  322   a.    
         [0050]    The reference surface  322   a  is formed into a tapered shape having a smooth slanting surface which continuously extends from the adjusting surface  322   b  to the adjusting surface  322   c . A central portion of this reference surface  322   a  is a reference position. A position of the adjusting surface  322   b  is higher than the reference position of the reference surface  322   a  by about {fraction (1/100)} to {fraction (2/100)} millimeter, and a position of the adjusting surface  322   c  is lower than the reference position of the reference surface  322   a  by about {fraction (1/100)} to {fraction (2/100)} millimeter. Positions of the reference surfaces  322   a  and the adjusting surfaces  322   b  and  322   c  formed in the divided regions are the same.  
         [0051]    [0051]FIG. 8A and FIG. 8B illustrate a partial configuration of the first lens frame  80  of the lens barrel according to the third embodiment. FIG. 8A is a plane view illustrating the partial configuration of the first lens frame  80  and FIG. 8B is a left side view of FIG. 8A. The first lens frame  80  is formed with the holding section  81  which holds the second lens  320 . The holding section  81  is formed at its four locations with lens-receiving sections  82  for fixing the second lens  320 . The lens-receiving section  82  is of semi-spherical shape. The lens-receiving section  82  receives the sliding surface  322  in a point-contact manner, and the lens-receiving section  82  may be of conical shape for example.  
         [0052]    According to the lens barrel of the third embodiment, the second lens  320  is provided with the sliding surface  322  having the different height from that perpendicular to the direction of the optical axis, and the sliding surface  322  is brought in contact with the lens-receiving section  82 . Therefore, the second lens  320  can be moved and adjusted in the direction of the optical axis only by rotating the second lens  320 , and the operation step required for this adjustment can be simplified. Since the reference surface  322   a  of the sliding surface  322  is formed into the tapered shape having the smooth slanting surface, it is possible to continuously and finely change the second lens  320  in the vicinity of the reference position in the direction of the optical axis. Thus, it is possible to more easily adjust (finely adjust) the focus of the image enlarging lens.  
         [0053]    Although it is not specifically described in the third embodiment, if the confirmation indices and the marks are provided like the lens barrel of the first embodiment, it is possible to grasp or find out which one of the surfaces of the sliding surface  322  formed on the second lens  320  is in contact with the lens-receiving section  82  of the first lens frame  80 .  
         [0054]    A fourth embodiment of this invention will be explained next. The fourth embodiment is a modification of the lens barrel shown in the third embodiment. FIG. 9A and FIG. 9B illustrate a shape of the second lens  420  used for the lens barrel in the third embodiment. FIG. 9A is a plan view of the second lens  420 , and FIG. 9B is a right side view of FIG. 9A.  
         [0055]    A right side surface (side surface closer to a film) of the second lens  420  is formed with a region which is equally divided into three such that the central angle becomes  1200 . Each region has a step  421  including a sliding surface  422 . The sliding surface  422  is formed with a reference surface  422   a , an adjusting surface  422   b  which is formed into a convex shape by the reference surface  422   a  and an adjusting surface  422   c  which is formed into a concave shape by the reference surface  422   a . The reference surface  422   a  is formed into a tapered shape having a smooth slanting surface which continuously extends from the adjusting surface  422   b  to the adjusting surface  422   c . A central portion of this reference surface  422   a  is a reference position.  
         [0056]    The highest position of the adjusting surface  422   b  is higher than a reference position. of the reference surface  422   a  by about {fraction (1/100)} to {fraction (2/100)} millimeter, and the lowest position of the adjusting surface  422   c  is lower than the reference position of the reference surface  422   a  by about {fraction (1/100)} to {fraction (2/100)} millimeter. Positions of the reference surfaces  422   a  and the adjusting surfaces  422   b  and  422   c  formed in the divided regions are the same.  
         [0057]    [0057]FIG. 10A and FIG. 10B illustrate a partial configuration of the first lens frame  90  of the lens barrel according to the fourth embodiment. FIG. 10A is a plane view illustrating the partial configuration of the first lens frame  90 , and FIG. 8B is a left side view of FIG. 8A.  
         [0058]    The first lens frame  90  is formed with the holding section  91  which holds the second lens  420 . The holding section  91  is formed at its four locations with lens-receiving sections  92  for fixing the second lens  420 . The lens-receiving section  92  is of semi-spherical shape. The lens-receiving section  92  receives the sliding surface  422  in a point-contact manner, and the lens-receiving section  92  may be of conical shape for example.  
         [0059]    According to the lens barrel of the fourth embodiment, the second lens  420  is provided with the sliding surface  422  having the different height from that perpendicular to the direction of the optical axis, and the sliding surface  422  is brought in contact with the lens-receiving section  92 . Therefore, the second lens  420  can be moved and adjusted in the direction of the optical axis only by rotating the second lens  420 , and the operation step required for this adjustment can be simplified. Since the second lens  420  can be varied in a quantitative manner in the direction of the optical axis, it is possible to easily adjust (finely adjust) the focus of the image enlarging lens. The number of each of the lens-receiving sections  92  and the sliding surfaces  422  is three which is minimum number for holding them on the circumference. Therefore, it is easy to form these members and it is possible to adjust and hold the second lens  420  in a most stable state. Since the reference surface  422   a  of the sliding surface  422  is formed into the tapered shape having the smooth slanting surface, it is possible to continuously and finely change the second lens  420  in the vicinity of the reference position in the direction of the optical axis. Thus, it is possible to more easily adjust (finely adjust) the focus of the image enlarging lens.  
         [0060]    Although it is not specifically described in the fourth embodiment, if the confirmation indices and the marks are provided like the lens barrel of the first embodiment, it is possible to easily recognize as to which one of the surfaces of the sliding surface  422  formed on the second lens  420  is in contact with the lens-receiving section  92  of the first lens frame  90 .  
         [0061]    A fifth embodiment of this invention will be explained next. FIG. 11 is a sectional view illustrating a partial configuration of a lens barrel of the fifth embodiment. In FIG. 11, a first lens group  100  having a first lens  1 , a second lens  520  and a third lens  3  arranged in this order from the side closer to the image (not shown) is held by the first lens frame  110 .  
         [0062]    The first lens frame  110  is formed with a holding section  111  which holds the second lens  520 . The second lens  520  is fixed by fixing a second lens  520  formed on a periphery of a left side surface of the second lens  520  and a lens-fixing section  114  provided on the first lens frame  110  by means of adhesive. In order to adjust the focus of the image enlarging lens for forming an image which is most suitable for the screen size to be projected, a washer  6  is interposed between the second lens  520  and the lens-receiving section  112  formed on the holding section  111 , and the position of the second lens  520  in a direction along the optical axis is adjusted. Details will be explained below.  
         [0063]    [0063]FIG. 12A to FIG. 12C illustrate a shape of the second lens  520 . FIG. 12A is a front view of the second lens  520 , FIG. 12B is a left side view of FIG. 12A and FIG. 12C is a right side view of FIG. 12A. A periphery of a front surface of the second lens  520  is formed with a step  521 . The front surface of the second lens  520  is formed with a region which is equally divided into four such that the central angle becomes 90°. The step  521  in each region is provided with a flat surface section  521   a  and a slanting surface section  521   b . The slanting surface section  521   b  is a smooth slanting surface, and a difference between the highest portion and the lowest portion of the slanting surface is about {fraction (1/100)} to {fraction (4/100)} millimeter. Positions of the flat surface section  521   a  and the slanting surface section  521   b  formed in the divided regions are the same.  
         [0064]    A right side (side closer to a film) of the second lens  520  is also formed with a step  524 . This step  524  is a sliding surface with respect to the lens-receiving section  112 .  
         [0065]    [0065]FIG. 13A and FIG. 13B illustrate a partial configuration of a first lens frame  110  of the lens barrel of the fifth embodiment. FIG. 13A is a plan view illustrating the partial configuration of the first lens frame  110 , and FIG. 13B is a left side view of FIG. 13A. The first lens frame  110  is formed with a holding section  111  which holds the second lens  520 . The holding section  111  is formed with a lens-receiving section  112  which fixes the second lens  520 . The lens-receiving section  112  is a surface perpendicular to the optical axis. The first lens frame  110  is formed at its four locations with bayonet convex sections (engaging sections)  113 . When the second lens  520  is fixed to the first lens frame  110 , the slanting surface section  521   b  of the second lens  520  is engaged with the bayonet convex sections  113 .  
         [0066]    By rotating the second lens  520  around the optical axis, the second lens  520  moves in the direction of the optical axis, and it is possible to bring the entire image enlarging lens into focus. The first lens frame  110  is formed with the lens-fixing section  114  for fixing the second lens  520 . The slanting surface section  521   b  is a constituent section whose height is continuously varied in the direction of the optical axis like the sliding surface, especially the tapered reference surfaces  322   a  and  422   a  explained in the previous embodiments.  
         [0067]    In the lens barrel of the fifth embodiment, the slanting surface section  521  b of the second lens  520  is engaged with the bayonet convex sections  113 , the second lens  520  is rotated around the optical axis to move the second lens  520  in the direction of the optical axis, and the second lens  520  is positioned so that the image enlarging lens can form a desired image.  
         [0068]    If a gap is adversely generated between the step  524  of the second lens  520  and the lens-receiving section  112  of the first lens frame  110 , the washer  6  is inserted into the gap and then, the slanting surface section  521   b  of the second lens  520  is engaged with the bayonet convex sections  113  of the first lens frame  110 . Lastly, the flat surface section  521   a  of the second lens  520  and the lens-fixing section  114  of the first lens frame  110  are adhered and fixed to each other using the adhesive. The adhering position is not on the side of the washer  6 . If the side of the washer  6  is adhered, it is necessary to attach both the front and back surfaces of the washer  6 . Only one location of the flat surface section  521   a  of the second lens  520  and only one location of the lens-fixing section  114  of the first lens frame  110  are adhered to each other. Since the adhesive is used in the portions which do not deviate the position of the fixed second lens  520  in this manner, the deviation in position which may be caused by the thickness of the adhesive and shrinkage of the adhesive can be avoided.  
         [0069]    According to the lens barrel of the fifth embodiment, since the slanting surface section  521   b  having the smooth slanting surface is engaged with the bayonet convex sections  113 , it is possible to continuously change the position of the second lens  520  in the direction of the optical axis by rotating the second lens  520  around the optical axis, and to adjust (finely adjust) the focus of the image enlarging lens.  
         [0070]    The embodiments of the present invention have been explained above with reference to the drawings. However, the invention is not limited to the embodiments, and it is of course possible to modify and improve the invention based on the description in the appended claims. For example, although the holding structure of the second lens which constitutes the first lens group is indicated in each of the embodiments, other lens can also be provided with the same holding structure as that of the second lens.  
         [0071]    According to the present invention as described above, the lens can be held by moving and adjusting the lens in the direction of the optical axis with respect to the lens frame. Since the lens which comes in contact with the lens-receiving section has the sliding surface whose height is different in the direction of the optical axis, the lens can be moved in the direction of the optical axis only by rotating the lens with respect to the lens frame, and there is effect that the adjusting operation of the focus by moving the lens can easily and efficiently be carried out.  
         [0072]    The present document incorporates by reference the entire contents of Japanese priority document, 2003-001606 filed in Japan on Jan. 7, 2003.  
         [0073]    Although the invention has been described with respect to a specific embodiment for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art which fairly fall within the basic teaching herein set forth.