Abstract:
A rod lens manufacturing method having satisfactory machining accuracy and enabling mass production. In the method, lens assembly sheets, each holding at least a row of rod lenses, are prepared. The lens assembly sheets are then arranged on holding surfaces defined on a jig. The holding surfaces are inclined relative to a reference surface of the jig by a predetermined angle. Each of the lens assembly sheet is clamped so that optical axes of the rod lenses are inclined relative to a direction perpendicular to the reference surface by that predetermined angle. The lens assembly sheets are then ground and polished.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a method, jig, and apparatus for machining rod lenses. 
     In the prior art, a method for manufacturing a rod lens is described in, for example, Japanese Examined Patent Publication No. 7-89161. Referring to FIG. 3, the manufacturing method is performed to manufacture a rod lens  11  having parallel end surfaces  63 ,  20   a  and an inclined surface  20   b , which is inclined relative to the end surfaces  63 ,  20   a  by angle θ. The prior art manufacturing method will now be discussed with reference to FIGS. 1 and 2. 
     Referring to FIG. 1A, a plurality of mother rod lenses  11 A are held in a frame  12 , which includes two glass plates  13 . The two sides of the frame  12  are each fixed to a frame spacer  14 . This forms a lens assembly sheet block  15 . In this state, the mother rod lenses  11 A are arranged so that their axes are aligned along a straight line  10 . The lens assembly sheet block  15  is then cut into lens assembly sheets  18 , each having a desired thickness L. The cut surfaces of each lens assembly sheet  18  are then polished to form parallel polished surfaces  16 ,  17  (refer to FIG.  1 B). 
     Referring to FIG. 2A, machining sheets  61 ,  62 , which are glass plates or the like, are fixed to the polished surfaces  16 ,  17  with an adhesive. Then, the machining sheet  61  is polished to form a polished surface  61   a,  which is inclined relative to the polished surface  16  of the lens assembly sheet  18  by angle θ (FIG.  2 B). Subsequently, the machining sheet  62  is polished parallel to the polished surface  61   a  to form the inclined surface  20   b  on each rod lens  11  (FIG.  2 C). The machining sheets  61 ,  62  are then removed from the lens assembly sheet  18 . The remaining surface  20   a  of each rod lens  11  adjacent to the inclined surface  20   b  is then machined and mirror finished so that it has a predetermined length A. Finally, the rod lenses  11  are removed from the frame  12 . Each rod lens  11  is shaped as shown in FIG.  3 . 
     However, when performing the above process, the adhering of the machining sheets  61 ,  62  to the lens assembly sheet  18  and the polishing of the sheets  61 ,  62  consume time. Thus, mass-production is difficult and manufacturing costs are high. Further, since the machining sheets  61 ,  62  are fixed to the lens assembly sheet  18  with an adhesive, the thickness of the resulting adhesive layer is not uniform. This leads to another shortcoming in which the angle θ of the inclined surfaces  20   b  and the length A of the remaining surfaces  20   a  are not constant. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a method, jig, and apparatus for machining rod lenses that has satisfactory machining accuracy and enables mass-production. 
     To achieve the above object, the present invention provides a method for machining rod lenses. The method includes preparing a plurality of lens assembly sheets, each holding at least a row of rod lenses. The plurality of lens assembly sheets are arranged on a plurality of holding surfaces defined on a jig. The plurality of holding surfaces are inclined relative to a reference surface of the jig by a predetermined angle. The method also includes clamping each of the lens assembly sheet with a clamp to hold the lens assembly sheet so that optical axes of the rod lenses are inclined relative to a direction perpendicular to the reference surface by the predetermined angle, grinding the plurality of lens assembly sheets, and polishing the plurality of lens assembly sheets. 
     A further perspective of the present invention is a method for arranging rod lenses to grind and polish the rod lenses. The method includes preparing a plurality of lens assembly sheets, each holding at least a row of rod lenses. The plurality of lens assembly sheets are arranged on a plurality of holding surfaces defined on a jig. The plurality of holding surfaces are inclined relative to a reference surface of the jig by a predetermined angle. The method also includes clamping each of the lens assembly sheet with a clamp to hold the lens assembly sheet so that optical axes of the rod lenses are inclined relative to a direction perpendicular to the reference surface by the predetermined angle. 
     A further perspective of the present invention is a machining jig used to perform at least one of grinding a rod lens and polishing a rod lens. The rod lens is fixed in a lens assembly sheet. The jig includes a reference surface, and a support arranged on the reference surface and having a holding surface on which the lens assembly sheet is held. The holding surface is inclined relative to the reference surface by a predetermined angle. 
     A further perspective of the present invention is an apparatus for machining a rod lens fixed in a lens assembly sheet. The apparatus includes a machining jig used to perform at least one of grinding the rod lens and polishing the rod lens. The jig includes a reference surface and a support arranged on the reference surface and having a holding surface for holding the lens assembly sheet. The holding surface is inclined relative to the reference surface by a predetermined angle. The apparatus also includes an index table on which the machining jig is arranged. 
     A further perspective of the present invention is an apparatus for machining a rod lens fixed in a lens assembly sheet. The apparatus includes a machining jig used to perform at least one of grinding the rod lens and polishing the rod lens. The jig includes a reference surface and a support arranged on the reference surface and having a holding surface for holding the lens assembly sheet. The holding surface is inclined relative to the reference surface by a predetermined angle. The apparatus also includes a table on which the machining jig is arranged. 
     Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: 
     FIG. 1A is a perspective view showing a prior art lens assembly sheet block; 
     FIG. 1B is a perspective view showing a prior art lens assembly sheet; 
     FIGS. 2A-2C are perspective views illustrating the machining of the prior art lens assembly sheet; 
     FIG. 3 is a perspective view showing a rod lens in the prior art; 
     FIG. 4 is a cross-sectional view showing a machining jig according to a first embodiment of the present invention; 
     FIG. 5 is a cross-sectional view showing the machining jig of the first embodiment; 
     FIG. 6A is a front view showing a grinding apparatus according to the first embodiment of the present invention; 
     FIG. 6B is a front view showing a further grinding apparatus according to the first embodiment of the present invention; 
     FIG. 7 is a schematic view showing the layout of the machining jig of FIG. 6A; 
     FIG. 8 is a front view showing a polishing apparatus of the first embodiment; 
     FIG. 9 is a cross-sectional view showing a lens assembly sheet after performing a polishing process according to the first embodiment of the present invention; 
     FIG. 10 is a perspective view showing the lens assembly sheet of FIG. 9 after performing the polishing process; 
     FIG. 11A is a perspective view showing a lens assembly sheet block according to a second embodiment of the present invention; 
     FIG. 11B is a perspective view showing a lens assembly sheet according to the second embodiment; 
     FIGS. 12A and 12B are cross-sectional views showing the lens assembly sheet after performing a grinding process according to the second embodiment of the present invention; and 
     FIG. 13 is a perspective view showing the lens assembly sheet after performing a polishing process of the second embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the drawings, like numerals are used for like elements throughout. 
     A method, jig, and apparatus for machining rod lenses according to a first embodiment of the present invention will now be described with reference to FIGS. 1A and 1B and FIGS. 4 to  10 . 
     In the first embodiment, the process for forming a lens assembly sheet  18  is the same as that of the prior art. As shown in FIG. 1A, a plurality of mother rod lens  11 A are held in a frame  12 , which includes two glass plates  13 . The two sides of the frame  12  are each fixed to a frame spacer  14 . This forms a lens assembly sheet block  15 . In this state, the mother rod lenses  11 A are arranged so that their axes are aligned along a straight line  10 . 
     The mother rod lenses  11 A are adhered integrally to one another in the frame  12 . The lens assembly sheet block  15  is then cut into lens assembly sheets  18 , each having a desired thickness L, as shown in FIG.  1 B. The cut surfaces of each lens assembly sheet  18  are then polished to form parallel polished surfaces  16 ,  17 . 
     A machining jig  21  of the first embodiment for machining the lens assembly sheet  18  will now be discussed. Referring to FIG. 4, the jig  21  includes a base plate  22 , which has an upper surface serving as a reference surface, and a plurality (in the first embodiment, two) of supports  23 . The supports  23  are equally spaced about the center  22   a  of the base plate  22  in an annular region. The center of the annular region coincides with the center  22   a  of the base plate  22 . 
     Each support  23  includes a holding surface  24   a  and a clamp. The holding surface  24   a  is inclined to the reference surface  22   b  of the base plate  22  by angle θ. A pit  24   b  is formed in the holding surface  24   a . The diameter of the pit  24   b  is greater than that of the rod lens  11 . The clamp includes a seat surface  24   c , an L-shaped jaw  25 , and a screw  26 . The seat surface  24   c  projects from the holding surface  24   a.    
     Referring to FIG. 5, a lens assembly sheet  18  is placed on the holding surface  24   a  of each support  23  so that its polished surface  17  contacts the holding surface  24   a  of the support  23  and its end surface  18   a  contacts the seat surface  24   c . The screw  26  is then fastened with the jaw  25  pressing the other end surface  18   b  of the lens assembly sheet  18 . Accordingly, the lens assembly sheet  18  is set on the holding surface  24   a  so that the optical axis of the rod lens  11  is inclined by angle θ relative to a direction perpendicular to the reference surface  22   b . The lens assembly sheet  18  is fixed to the support  23  without the end surfaces (polished surfaces)  63  (FIG. 3) of the rod lenses  11  contacting the holding surface  24   a.    
     Referring to FIG. 6A, a grinding apparatus  30  includes a rotating table  31 , which is an index table and rotates about a shaft  32 . The rotating table  31  is intermittently rotated so that it is indexed every predetermined angle (in the first embodiment, every 90 degrees). Referring to FIG. 7, a plurality of the machining jigs  21  (in the first embodiment, four) is fixed to the upper surface of the rotating table  31  by, for example, screws (not shown). 
     As shown in FIG. 6A, a plurality of rotary grindstones  34  are arranged above the rotating table  31 . The rotary grindstones  34  include a roughing grindstone and a finishing grindstone. The rotary grindstones  34  are each fixed to a rotary body  33  and rotated about a shaft  35  of the rotary body  33 . 
     The jigs  21 , each of which holds a lens assembly sheet  18 , is fixed to predetermined positions on the rotating table  31 . The rotating table  31  is intermittently rotated to sequentially arrange the lens assembly sheets  18  at a machining position opposing one of the rotary grindstones  34 . The rotary grindstones  34  grind the lens assembly sheets  18  in the order of rough grinding, middle grinding, and finish grinding. The plurality of rotary grindstones  34  simultaneously perform different types of grinding on the lens assembly sheets  18 . 
     The reference surface  22   b  of each base plate  22  is parallel to the grinding surfaces of the rotary grindstones  34 . Thus, the lens assembly sheets  18  are ground on the corresponding holding surfaces  24   a  inclined by angle θ. The distance between each base plate  22  and the rotary grindstones  34  is measured prior to the grinding. The distance is measured again during the grinding. The amount of material ground from the lens assembly sheets  18  is obtained from the difference between the distances. Thus, a predetermined amount of material may be removed from the lens assembly sheets  18  by monitoring the distance between each base plate  22  and the rotary grindstones  34  during the grinding. Then, the jigs  21  are removed from the rotating table  31  with the lens assembly sheets  18  attached to the jigs  21 . Cutting chips, abrasive grains, and grinding liquid are washed away from the jigs  21  and the lens assembly sheets  18 . The lens assembly sheets  18  are then removed from the jigs  21  and washed again. 
     A grinding apparatus  39  shown in FIG. 6B may be employed in lieu of the grinding apparatus  30  of FIG. 6A to grind the lens assembly sheets  18 . The grinding apparatus  39  includes a single rotary grindstone  34 A, which simultaneously covers a plurality of the lens assembly sheets  18 . Thus, the plurality of the lens assembly sheets  18  are simultaneously ground. Since the grinding apparatus  39  has only one type of rotary grindstone, the feed rate per unit time of the rotary grindstone  34 A is adjusted to perform the rough and finish grinding. Rough grinding is performed when the feed rate per unit time is large, and finish grinding is performed when the feed rate per unit time is small. 
     Referring to FIG. 8, a polishing apparatus  40  includes a rotating table  41 , which rotates about a rotary shaft  43 , a rotary grindstone (polishing body)  42  fixed to the rotating table  41 , and the machining jigs  21 . The jigs  21  are arranged along a circle, the center of which is the axis of the rotary shaft  43 . Each of the jigs  21  includes the support  23  to which a lens assembly sheet  18  is fixed. The jigs  21  are supported in the polishing apparatus  40  so that the reference surface  22   b  of each base plate  22  is parallel to the polishing surface of the rotary grindstone  42 . Thus, the lens assembly sheets  18  are polished inclined by angle θ relative to the rotary grindstone  42 . The distance between each base plate  22  and the rotary grindstone  42  is measured prior to the polishing. The distance is measure again during the polishing. The amount of material polished from the lens assembly sheets  18  is obtained from the difference between the distances. Thus, a predetermined amount of material is removed by monitoring the distance between each base plate  22  and the rotary grindstone  42  during the polishing. 
     The grinding and polishing forms a remaining polished surface  16   a , which is parallel to the polished surface  17 , and a polished surface  16   b , which is parallel to the reference surface  22   b , in each machined lens assembly sheet  18 A, as shown in FIGS. 9 and 10. In other words, referring to FIG. 10, a remaining surface  20   a , which is parallel to the polished surface  16   a , and an inclined surface  20   b , which is inclined relative to the remaining surface  20   a  by angle θ, are formed adjacent to each other in each of the rod lenses  11 . Finally, the rod lenses  11  are removed from the lens assembly sheet  18 A to obtain the rod lenses  11  of FIG.  3 . 
     The grinding and polishing performed in the first embodiment has the advantages described below. 
     (1) Each machining jig  21  has holding surface  24   a  to which the lens assembly sheets  18  are fixed inclined at the predetermined angle θ. Thus, the rod lenses  11  are easily ground and polished in a state inclined by the predetermined angle θ without using machining sheets. 
     (2) The reference surface  22   b  of the machining jigs  21  is parallel to the rotary grindstones  34  of the grinding apparatus  30 . Thus, the ground amount is easily obtained from the difference of the distances between the reference surface  22   b  and each rotary grindstone  34  prior to and during grinding. Further, the reference surface  22   b  of the machining jigs  21  is parallel to the rotary grindstone  42  of the polishing apparatus  40 . Thus, the polished amount is easily obtained from the difference of the distances between the reference surface  22   b  and the rotary grindstone  42  prior to and during polishing. Accordingly, a predetermined amount of material is accurately ground and polished. As a result, the rod lens  11  is formed having the desired lens length and the desired remaining surface length A. 
     (3) A plurality of the lens assembly sheet  18  are simultaneously ground and polished. Thus, rod lenses are mass-produced. 
     (4) Due to the pit  24   b , the polished end surface  63  of each rod lens  11  does not contact the support  23 . This prevents the polished end surface  63  from being damaged. 
     (5) The clamp includes the seat surface  24   c , the jaw  25 , and the screw  26 . Thus, the lens assembly sheet  18  is easily attached to and removed from the support  23  by manipulating the screw  26 . 
     (6) The indexing of the rotating table  31  enables rough, middle, and finishing grinding to be successively performed with the lens assembly sheet  18  fixed to the machining jig  21 . This reduces the number of operations performed to machine the lens. 
     (7) A plurality of the lens assembly sheet  18  are simultaneously ground by the single rotary grindstone, which covers every lens assembly sheet  18 . This improves manufacturing efficiency. 
     In a second embodiment of the present invention, the lens assembly sheet  18  of FIG. 1B is replaced by a double row lens assembly sheet  52 , which is shown in FIG.  11 B. The double row lens assembly sheet  52  includes two rows of the rod lenses  11 . Parts differing from the first embodiment will now be described. 
     Referring to FIG. 11A, a plurality of mother rod lenses  11 A arranged in two rows are held by a frame  12 A, which has three glass plates  13 . Frame spacers  14  are arranged at the sides of the glass plates  13  to form a lens assembly sheet block  51 . The mother rod lenses  11 A are arranged in each row so that a line connecting their axes are parallel to lines connecting axes of the mother rod lenses  11 A in other rows. The mother rod lenses  11 A are adhered to one another in the frame  12 A. As shown in FIG. 11B, the lens assembly sheet block  51  is cut into double row lens assembly sheets  52 , each having a predetermined thickness L. The cut surfaces are polished to form parallel polished surfaces  16 ,  17 . 
     Referring to FIG. 12A, each double row lens assembly sheet  52  is fixed to a machining jig  21 A. The machining jig  21  has holding surfaces  24   a , each of which is wider than the holding surfaces  24   a  of the machining jig  21  in the first embodiment, to hold the wide double row lens assembly sheet  52 . A pit  24   b  formed in the holding surface  24   a  is wider than the pit  24   b  of the machining jig  21  in the first embodiment so that the two rows of rod lenses  11  do not contact the holding surface  24   a.    
     The double row lens assembly sheet  52  is ground with the grinding apparatus of FIG. 6A or  6 B. Referring to FIG. 12A, a predetermined amount of material is ground in the same manner as the first embodiment from a first rod lens row of each double row lens assembly sheet  2 . This forms a remaining polished surface  16   a , which is parallel to the polished surface  17 , and a ground surface  52   b , which is parallel to the base plate  22  and inclined to the polished surface  16   a  by angle θ. The jaw  25  and the screw  26  are then manipulated to remove the double row lens assembly sheet  52  from each machining jig  21 . Then, the sides of the double row lens assembly sheet  52  are reversed. In this state, the double row lens assembly sheet  52  is fixed to the jig  21 A so that a second rod lens row is located at a grinding position. 
     Referring to FIG. 12B, a predetermined amount of material is ground from the second rod lens row. This forms a ground surface  52   c , which is parallel to the base plate  22  and which is inclined by angle θ relative to the polished surface  16   a . As a result, the polished surface  16   a , which is parallel to the polished surface  17 , remains in the middle of the double row lens assembly sheet  52 . Further, the ground surfaces  52   b ,  52   c , which are inclined by angle  0  relative to the polished surface  16   a , are formed with the polished surface  16   a  located in between. 
     The ground surfaces  52   b ,  52   c  of each double row lens assembly sheet  52  undergo optical polishing with the polishing apparatus  40  of FIG.  8 . Like in the first embodiment, a plurality of the double row lens assembly sheet  52  are simultaneously polished. A first polishing surface, or a polished surface  16   c , is formed by, for example, polishing the ground surface  52   c  with the rotary grindstone  42 . 
     Then, the sides of each double row lens assembly sheet  52  is reversed on the corresponding support  23  so that the second ground surface  52   b  opposes the rotary grindstone  42 . The second ground surface  52   b  is then polished to form a polished surface  16   b . As a result, referring to FIG. 13, the polished surface  16   a , which is parallel to the polished surface  17 , remains in the middle of the polished double row lens assembly sheet  52 A. Further, the polished surfaces  16   b ,  16   c  inclined by angle θ relative to the polished surface  16   a  are formed with the polished surface  16   a  located in between. In other words, the remaining surface  20   a , which is parallel to the polished surface  17 , and the inclined surface  20   b , which is inclined by angle θ relative to the polished surface  17 , are formed on each of the rod lenses  11 , which are arranged in two rows. Finally, the rod lenses  11  are each removed from the lens assembly sheet  52 A to obtain the rod lens  11  of FIG.  3 . 
     In addition to the advantages of the first embodiment, the second embodiment has the advantages described below. 
     The double row lens assembly sheet  52  has two rows of the rod lenses  11 . Thus, the rod lenses  11  are mass-produced. 
     It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Particularly, it should be understood that the present invention may be embodied in the following forms. 
     A lens assembly sheet may be polished with the polishing apparatus  40  by rotating only the base plate  22  or by rotating the rotary grindstone  42  and the base plate  22 . 
     A lens assembly sheet may be ground and polished on a table that performs indexing by moving in a linear manner. 
     Instead of using a rotary table, the base plate  22  may be arranged on a fixed table to perform grinding and polishing. 
     The rotary grindstones  34 ,  42  may have a grinding surface or a polishing surface inclined at a predetermined angle so that an end surface of each rod lens  11  is formed inclined at angle θ. 
     The same type of grindstones may be employed as the grindstones  34  of the grinding apparatus  30  shown in FIG.  6 A. In such case, the feed rate per unit time of the rotary grindstones  34  may be changed to perform the rough and finish grinding. 
     Lens assembly sheets may undergo only grinding or undergo both grinding and optical polishing. 
     In the second embodiment, the ground surface  52   c  may be formed from the first rod lens row of the double row lens assembly sheet  52 , and the ground surface  52   c  may be polished afterward to form the polished surface  16   c . Then, the ground surface  52   b  may be formed from the second rod lens row, and the ground surface  52   b  may be polished afterward to form the polished surface  16   b.    
     The present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.