Abstract:
A method that accurately cuts mother rod lenses and increases production yield. The method includes arranging the mother rod lenses such that the optical axes of the mother rod lenses are parallel to one another, forming a lens block having perpendicular first and second side surfaces to integrally hold the predetermined mother rod lenses, arranging the lens block at a predetermined position, emitting laser beams respectively toward the first and second side surfaces, receiving reflection lights of the laser beams with first and second screens, respectively, adjusting the perpendicularity of the side surfaces relative to a cutting surface of the cutter such that the reflection lights of the side surfaces hit base positions on the first and second screen, and cutting the lens block and the mother rod lenses with the cutter to produce a plurality of rod lenses.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a method for cutting a mother rod lens and to a lens block for supporting a mother rod lens. More particularly, the present invention relates to a method for cutting a mother rod lens, which has a predetermined gradient index, into rod lenses having predetermined lengths. 
     In the prior art, to manufacture a gradient index rod lens, an elongated mother rod lens having a predetermined gradient index is cut into rod lenses having a predetermined length in accordance with the purpose of usage. Each end surface of a cut rod lens must be formed at a predetermined angle relative to the optical axis of the rod lens. The end surface of the rod lens may be formed so that it is basically perpendicular to the optical axis of the rod lens. Alternatively, the end surface of the rod lens may be inclined relative to the optical axis to decrease reflection loss. 
     Further, in the prior art, a single mother rod lens is cut to form rod lenses, which have predetermined lengths, one at a time. Therefore, the manufacturing efficiency of the rod lens is low. Further, if the accuracy of perpendicularity between the optical axis of the mother rod lens and the cut surface of the rod lens is low, the optical capabilities of the rod lens may decrease and the difference in lens characteristic between rod lenses may increase. This may decrease the yield of the rod lenses. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a method for cutting a mother rod lens and a lens block for supporting a mother rod lens that increases manufacturing efficiency and increases yield through highly accurate cutting. 
     To achieve the above object, the present invention provides a method for cutting a plurality of mother rod lenses having a predetermined gradient index with a cutter. The method includes arranging the mother rod lenses, each having an optical axis, such that the optical axes of the mother rod lenses are parallel to one another, and forming a lens block for holding the mother rod lenses. The lens block has a first side surface and a second side surface. The first and second side surfaces are arranged parallel to the optical axes and at a predetermined angle with respect to each other. The method further includes arranging the lens block at a predetermined position, emitting laser beams respectively toward the first and second side surfaces, receiving reflection lights of the laser beams reflected by the first and second side surfaces with first and second screens, respectively, adjusting the perpendicularity of the first side surface relative to a predetermined cutting surface of the cutter such that the reflection light of the first side surface hits a first base position on the first screen, adjusting the perpendicularity of the second side surface relative to the predetermined cutting surface such that the reflection light of the second side surface hits a second base position on the second screen, and cutting the lens block and the mother rod lenses with the cutter to produce a plurality of rod lenses having a predetermined length. 
     A further perspective of the present invention is a method for cutting a plurality of mother rod lenses having a predetermined gradient index with a cutter. The method includes arranging the mother rod lenses, each having an optical axis, such that the optical axes of the mother rod lenses are parallel to one another, and forming a lens block for holding the mother rod lenses. The lens block has an outer surface parallel to the optical axes. A first flat surface reflection body and a second flat surface reflection body are arranged on the outer surface separated from each other by a predetermined distance. The method further includes arranging the lens block at a predetermined position, emitting laser beams respectively toward the first and second flat surface reflection bodies, receiving reflection lights of the laser beams reflected by the first and second flat surface reflection bodies with first and second screens, respectively, adjusting the perpendicularity of the first flat surface reflection body relative to a predetermined cutting surface of the cutter such that the reflection light of the first flat surface reflection body hits a first base position on the first screen, adjusting the perpendicularity of the second flat surface reflection body relative to the predetermined cutting surface such that the reflection light of the second flat surface reflection body hits a second base position on the second screen, and cutting the lens block and the mother rod lenses with the cutter to produce a plurality of rod lenses having a predetermined length. 
     A further perspective of the present invention is a lens block for holding a plurality of mother rod lenses having a predetermined gradient index to cut the mother rod lenses with a cutter. The lens block includes a holding frame for holding the mother rod lenses, each having an optical axis, such that the optical axes of the mother rod lenses are parallel to one another. The holding frame has two side surfaces arranged parallel to the optical axes and at a predetermined angle with respect to each other. The holding frame and the mother rod lenses are integrated with each other by a resin. 
     A further perspective of the present invention is a lens block for holding a plurality of mother rod lenses having a predetermined gradient index to cut the mother rod lenses with a cutter. The lens block includes a holding frame for holding the mother rod lenses, each having an optical axis, such that the optical axes of the mother rod lenses are parallel to one another. The holding frame has an outer surface parallel to the optical axes. The holding frame and the mother rod lenses are integrated with each other by a resin. 
     A further perspective of the present invention is a lens block for holding a plurality of mother rod lenses having a predetermined gradient index to cut the mother rod lenses with a cutter. The lens block includes a plurality of cylindrical dummy glass rods, each having a center axis, and a holding frame for holding the dummy glass rods such that the center axes of the mother rod lenses are parallel to one another. The holding frame has two side surfaces arranged parallel to the center axes and at a predetermined angle with respect to each other. The mother rod lenses each have a diameter smaller than the diameter of the dummy glass rods. The mother rod lenses are held between the dummy glass rods and the holding frame such that the optical axes of the mother rod lenses are parallel to one another. The holding frame, the dummy glass rods, and the mother rod lenses are integrated with each other by a resin. 
     A further perspective of the present invention is a lens block for holding a plurality of mother rod lenses having a predetermined gradient index to cut the mother rod lenses with a cutter. The lens block includes a plurality of cylindrical dummy glass rods, each having a center axis, and a holding frame for holding the dummy glass rods such that the center axes of the mother rod lenses are parallel to one another. The holding frame has an outer surface parallel to the center axes. The mother rod lenses each have a diameter smaller than the diameter of the dummy glass rods. The mother rod lens is held between the dummy glass rods and the holding frame such that the optical axes of the mother rod lenses are parallel to one another. The holding frame, the dummy glass rods, and the mother rod lenses are integrated with each other by a resin. 
     A further perspective of the present invention is a cutting apparatus for cutting a plurality of mother rod lenses held by a lens block. The lens block has a first side surface and a second side surface arranged at a predetermined angle relative to each other. The apparatus includes a cutting machine for cutting the lens block along a predetermined cutting surface. A laser beam source emits laser beams toward the first and second side surfaces. A first screen and a second screen receive reflection lights of the laser beams reflected by the first and second side surfaces, respectively. The first screen has a first base line hit by the reflection light of the laser beam reflected by the first side surface when the first side surface is perpendicular to the predetermined cutting surface. The second screen has a second base line hit by the reflection light of the laser beam reflected by the second side surface when the second side surface is perpendicular to the predetermined cutting surface. 
     A further perspective of the present invention is a cutting apparatus for cutting a plurality of mother rod lenses held by a lens block. The lens block has an outer surface including a first flat surface reflection body and a second flat surface reflection body separated from each other by a predetermined distance. The apparatus includes a cutting machine for cutting the lens block along a predetermined cutting surface. A laser beam source emits laser beams toward a first side surface and a second side surface. A first screen and a second screen receive reflection lights of the laser beams are reflected by the first and second flat surface reflection bodies, respectively. The first screen has a first base line hit by the reflection light of the laser beam reflected by the first flat surface reflection body when the first flat surface reflection body is perpendicular to the predetermined cutting surface. The second screen has a second base line hit by the reflection light of the laser beam reflected by the second flat surface reflection body when the second flat surface reflection body is perpendicular to the predetermined cutting surface. 
     A further perspective of the present invention is a method for positioning a lens block holding a plurality of mother rod lenses to cut a plurality of mother rod lenses with a cutter. The lens block includes a holding frame for holding the mother rod lenses, each having an optical axis, such that the optical axes of the mother rod lenses are parallel to one another. The holding frame includes a first side surface and a second side surface arranged parallel to the optical axes and at a predetermined angle relative to each other. The method includes arranging the lens block at a predetermined position, emitting laser beams respectively toward the first and second side surfaces, receiving reflection lights of the laser beams reflected by the first and second side surfaces with first and second screens, respectively, adjusting the perpendicularity of the first side surface relative to a predetermined cutting surface of the cutter such that the reflection light of the first side surface hits a first base position on the first screen, and adjusting the perpendicularity of the second side surface relative to the predetermined cutting surface such that the reflection light of the second side surface hits a second base position on the second screen. 
     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. 1 is an explanatory diagram illustrating a method for cutting a mother rod lens according to a first embodiment of the present invention; 
     FIGS. 2A and 2B are explanatory diagrams illustrating the adjustment of perpendicularity in the cutting method of FIG. 1; 
     FIG. 3 is a schematic diagram illustrating the layout of a cutting apparatus used in the cutting method of FIG. 1; 
     FIG. 4 is a perspective view showing a lens block used in the cutting method of FIG. 1; 
     FIG. 5 is a perspective view showing a lens block piece cut from the lens block of FIG. 4; 
     FIG. 6 is an explanatory diagram showing a polishing machine of the lens block piece of FIG. 5; 
     FIG. 7 is a front view showing a lens block according to a second embodiment of the present invention; and 
     FIG. 8 is a perspective view showing a modification of the first embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the drawings, like numerals are used for like elements throughout. 
     First Embodiment 
     FIG. 1 is an explanatory diagram illustrating a method for cutting a mother rod lens  12  according to a first embodiment of the present invention. A lens block  11 , which is shown in FIG. 1, will now be described with reference to 
     FIG.  4 . 
     The lens block  11  includes two main glass plates  13 ,  14  and two side glass plates  15 ,  16 . The main glass plates  13 ,  14  and the side glass plates  15 ,  16  surround a plurality (seven in the first embodiment) of cylindrical mother rod lenses  12 . The mother rod lenses  12  each have a predetermined gradient index and are arranged along a single row so that the optical axes C of the mother rod lenses  12  are parallel to one another. 
     The main glass plates  13 ,  14  and the side glass plates  15 ,  16  form a rectangular parallelepiped and holds seven mother rod lenses  12 . The rectangular parallelepiped includes two end surfaces  17 ,  18  and four side surfaces  19 ,  20 ,  21 , and  22 , which are parallel to the optical axes C. 
     The main glass plates  13 r  14 , the side glass plates  15 ,  16 , and the mother rod lenses  12  are integrated with one another by wax (resin)  23 . The wax  23  easily softens when heated. 
     A cutting apparatus  100  used in a cutting method of the first embodiment will now be described with reference to FIGS. 1 and 3. 
     The cutting apparatus  100  includes a cutting machine  32 , a laser beam source  35 , a first (X axis direction) screen  38 , and a second (Y axis direction) screen  39 . The cutting machine  32  includes a cutter  30 , and a surface plate  31 , on which the lens block  11  is arranged. As shown in FIG. 3, the cutting apparatus  100  includes a coolant supplying device  70  for supplying coolant to the cutter  30 . 
     The inclination of the surface plate  31  relative to a predetermined cutting surface  33  that would be formed by the cutter  30  is adjustable. The inclination of the surface plate  31  is adjusted relative to the predetermined cutting surface  33  in the X and Y axis directions. The lens block  11  is arranged on the surface plate  31  so that the end surface  18  of the lens block  11  contacts the surface plate  31 . 
     The laser beam source  35  emits laser beams  34  toward two of the four side surfaces  19 - 22  that are perpendicular to each other (in FIG. 1, the first side surface  19  and the second side surface  20 ). The first screen  38  receives a reflection light  36  of the laser beam  34  reflected by the side surface  19 . The second screen  39  receives a reflection light  37  of the laser beam  34  reflected by the side surface  20 . 
     The lens block  11 , which has long sides with a length of about 5 cm, is shown in an enlarged state in FIG.  1 . For the sake of convenience, the laser beams  34 , which are actually emitted from a single laser beam source  35 , are shown separated into an A-laser beam and a B-laser beam. Further, to facilitate understanding, the first side surface  19  of the lens block  11  irradiated by the A-laser beam is referred to as an A-surface, and the second side surface  20  irradiated by the B-laser beam is referred to as a B-surface. The angle of incidence of the A-laser beam and the B-laser beam with respect to the corresponding A-surface  19  and B-surface  20  is about 45°. 
     A base line  38   a , which serves as a base position, is impressed on the first screen  38  at a position where the reflection light  36  of the A-laser beam hits the first screen  38  when the A-surface  19  is perpendicular to the predetermined cutting surface  33 . In the same manner, a base line  39   a , which serves as a base position, is impressed on the second screen  39  at a position where the reflection light  37  of the B-laser beam hits the second screen  39  when the B-surface  20  is perpendicular to the predetermined cutting surface  33 . 
     A method for cutting a mother rod lens according to the first embodiment will now be described with reference to FIGS. 1 and 2. The method includes the following steps A-F. 
     (A) The lens block  11  of FIG. 4 is first formed. 
     (B) Then, the lens block  11  is arranged on the surface plate  31  such that the end surface  18  of the lens block  11  contacts the surface plate  31 . In this state, the A-laser beam and the B-laser beam are emitted toward the corresponding A-surface  19  and the B-surface  20 , which are perpendicular to each other. 
     (C) The first screen  38  receives the reflection light  36  of the A-laser beam, and the second screen  39  receives the reflection light  37  of the B-laser beam. 
     (D) The perpendicularity of the A-surface  19  relative to the predetermined cutting surface  33  is adjusted by inclining the surface plate  31  by a predetermined amount so that the reflection light  36  hits the base line  38   a.    
     The perpendicularity of the A-surface  19  is adjusted in the following manner. 
     When the A-surface  19  is perpendicular to the predetermined cutting surface  33 , the reflection light  36   0  of the A-laser beam (laser beam  34 ) reflected by the A-surface  19  hits the base line  38   a  of the first screen  38 , as shown by the solid line in FIG.  2 A. When the A-surface  19  is inclined downward by angle θ1 relative to the predetermined cutting surface  33 , the reflection light  36   1 , is oriented downward by angle θ1 such that the reflection light  36   1  hits the first screen  38  at a position lower than the base line  38   a , as shown by the broken line in FIG.  2 A. 
     When the A-surface  19  is inclined upward by angle θ2 relative to the predetermined cutting surface  33 , the reflection light  36   2  is oriented upward by angle θ2 such that the reflection light  36   0  hits the first screen  38  at a position higher than the base line  38   a.    
     Accordingly, the position of the reflection light  36  on the first screen  38  is monitored to adjust the perpendicularity of the A-surface  19  relative to the predetermined cutting surface  33  such that the reflection light  36  hits the base line  38   a.    
     (E) The perpendicularity of the B-surface  20  relative to the predetermined cutting surface  33  is adjusted by inclining the surface plate  31  such that the reflection light  37  hits the base line  39   a.    
     The perpendicularity of the B-surface  20  is adjusted in the following manner. 
     When the B-surface  20  is perpendicular to the predetermined cutting surface  33 , the reflection light  37   0  of the B-laser beam (laser beam  34 ) reflected by the B-surface  20  hits the base line  39   a  of the second screen  39 , as shown by the solid line in FIG.  2 B. When the B-surface  20  is inclined downward by angle θ1 relative to the predetermined cutting surface  33 , the reflection light  37   1  is oriented downward by angle θ1 such that the reflection light  37   1  hits the second screen  39  at a position lower than the base line  39   a , as shown by the broken line in FIG.  2 B. When the B-surface  20  is inclined upward by angle θ2 relative to the predetermined cutting surface  33 , the reflection light  37   2  is oriented upward by angle θ2 such that the reflection light  37   0  hits the second screen  39  at a position higher than the base line  39   a.    
     Accordingly, the position of the reflection light  37  on the second screen  39  is monitored to adjust the perpendicularity of the B-surface  20  relative to the predetermined cutting surface  33  such that the reflection light  37  hits the base line  39   a.    
     (F) After adjusting the perpendicularity of the A-surface  19  and the B-surface  20  relative to the predetermined cutting surface  33 , the cutter  30  sequentially cuts the lens block  11  into predetermined lengths (as shown by the broken lines in FIG. 4) In this state, the surface plate  31  is moved relative to the cutter  30  in the direction of arrow A in FIG.  1 . After the first piece of the lens block  11  is cut, the surface plate  31  is moved by a predetermined distance in the direction of arrow B to return the lens block  11  to its original position and cut the next piece. 
     The polishing of a lens block piece  40  cut from the lens block  11  to have a predetermined length will now be described with reference to FIGS. 5 and 6. 
     FIG. 5 shows the lens block piece  40 , which is cut into a predetermined length. The lens block piece  40  includes seven rod lenses  41 , each of which has a predetermined length. 
     The cutting machine  32  of FIG. 3 is an inner circumference blade cutting machine, and the cutter  30  of the cutting machine  32  is an annular diamond cutter. By cutting the lens block  11  with the diamond cutter  30 , the seven mother rod lenses  12  are accurately cut. The cutting surface of each mother rod lens  12  has, for example, a roughness of Rmax 5 μm or less. 
     In the prior art, the cutting surface of the lens block is polished after rough grinding and sand blast grinding (fine grinding) the cutting surface. In comparison, the grinding processes are not performed in the preferred embodiment. More specifically, the lens block pieces  40  cut from the lens block  11  are polished by a polishing machine  50 , which is shown in FIG. 6, without undergoing grinding. The polishing agent is, for example, an aqueous solution including cerium oxide. 
     After the polishing is performed, the wax  23  is heated and warmed to separate seven rod lenses  41  from the lens block piece  40 . The rod lenses  41  are than washed to remove the wax  23  from the rod lenses  41 . This completes the rod lenses  41 , which have predetermined lengths. 
     The method for cutting mother rod lenses according to the first embodiment has the advantages described below. 
     The cutter  30  sequentially cuts the lens block  11 , which holds seven mother rod lenses  12 , into the lens block pieces  40 , which have predetermined lengths. This produces seven rod lenses  41  at a time and improves the production efficiency of the rod lenses  41 . 
     The inclinations of the A-surface  19  and the B-surface  20  relative to the predetermined cutting surface  33  are each adjusted so that the reflection lights  36 ,  37  from the side surfaces  19 ,  20  of the lens block  11  hits the base lines  38   a ,  39   a  of the first and second screens  38 ,  39 , respectively. Thus, the perpendicularity between the optical axis C of each mother rod lens  12  and the predetermined cutting surface  33  is easily and accurately set. 
     The single laser beam source  35  emits the laser beams  34  toward the first side surface  19  and the second side surface  20 , which are perpendicular to each other among the four side surfaces  19 - 22  of the lens block  11 . Accordingly, only one laser beam source  35  is required to emit laser beams toward the side surfaces  19 ,  20 . This reduces the cost of the cutting apparatus  100 . 
     In the lens block  11 , the seven mother rod lenses  12 , the two main glass plates  13 ,  14 , and the two side glass plates  15 ,  16  are integrated with each other by the wax  23 . Thus, when the seven mother rod lenses  12  are cut, each mother rod lens  12  is held in a fixed state in the lens block  11 . This prevents differences in the cutting surface accuracy of each mother rod lens  12  from being produced. In other words, differences in the angle (e.g., perpendicularity) of the cutting surface of each rod lens relative to the optical axis C does not occur. 
     Second Embodiment 
     A lens block  51  according to a second embodiment of the present invention will now be described with reference to FIG.  7 . The lens block  51  is cut using the cutting method of the first embodiment. 
     The lens block  51  includes two main glass plates  54 ,  55  and two side glass plates  56 ,  57 . The main glass plates  54 ,  55  and the side glass plates  56 ,  57  hold a plurality of (four in the second embodiment) dummy glass rods  53 . The dummy glass rods  53  are arranged along a row so that the center axes C 1  of the dummy glass rods  53  are parallel to one another. 
     The main glass plates  54 ,  55  and the side glass plates  56 ,  57  are arranged to form a rectangular parallelepiped. The lens block  51  includes two end surfaces  58  (only one of the end surfaces is shown in FIG.  7 ), which are perpendicular to the optical axes C of mother rod lenses  52 , and side surfaces  59 ,  60 ,  61 , and  62 , which are parallel to the optical axes C. 
     The lens block  51  also includes a plurality of (six in the second embodiment) the mother rod lenses  52 , each of which has a diameter smaller than that of the dummy glass rods  53  and each of which has a predetermined gradient index. The six mother rod lenses  52  are held between the four dummy glass rods  53  and the main glass plates  54 ,  55  so that the optical axes C of the mother rod lenses  52  are parallel to one another. The main glass plates  54 ,  55 , the side glass plates  56 ,  57 , the four dummy glass rods  53 , and the six mother rod lenses  52  are integrated with one another by wax  23 . 
     The lens block  51  of the second embodiment has the advantages described below. 
     The six mother rod lenses  52 , the diameter of which is smaller than that of the dummy glass rods  53 , are held between the four dummy glass rods  53  and the main glass plates  54 ,  55  so that the optical axes C of the mother rod lenses  52  are parallel to one another. The main glass plates  54 ,  55 , the side glass plates  56 ,  57 , the tour dummy glass rods  53 , and the six mother rod lenses  52  are integrated with one another by wax  23 . Accordingly, the mother rod lenses  52  are held in a fixed state when cut even if the diameter of the mother rod lenses  52  is small, such as less than one millimeter. This prevents differences between the cutting surfaces of the mother rod lenses  52 . 
     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. 
     In the first embodiment, laser beams may be emitted to the two side surfaces  19 ,  20  from two laser beam sources. 
     In the first embodiment, after adjusting the perpendicularity of the two side surfaces  19 ,  20  relative to the predetermined cutting surface  33 , one of the side surfaces  19 ,  20  may be inclined by a predetermined angle relative to the predetermined cutting surface  33 . In this state, the lens block  11  may be cut. This easily, efficiently, and accurately manufactures rod lenses having end surfaces that are parallel to each other and inclined by a predetermined angle relative to the optical axes C. 
     In the first embodiment, as shown in FIG. 8, a lens block  71  may be formed by a cylindrical glass pipe (holding frame)  72 . In this state, a plurality of the mother rod lenses  12  are arranged in the cylindrical space in the glass pipe  72  so that the optical axes C of the mother rod lenses  12  are parallel to one another. Further, the cylindrical outer surface of the glass pipe  72  is parallel to the optical axes C of the mother rod lenses  12 . 
     In this case, as shown in FIG. 8, compact first and second flat surface reflection mirrors  73 ,  74  are fixed to the cylindrical outer surface of the glass pipe  72  separated from each other by a predetermined distance. The A-laser beam and the B-laser beam are emitted toward the two reflection mirrors  73 ,  74 , respectively. The perpendicularity of the cylindrical outer surface glass pipe  72  relative to the predetermined cutting surface  33  is adjusted so that the reflection lights  36 ,  37  of the A-laser beam and the B-laser beam reflected by the reflection mirrors  73 ,  74  hits the base lines  38   a ,  39   a  on the screens  38 ,  39 , respectively. 
     In the first embodiment, a base mark may be provided on the screens  38 ,  39  in lieu of the base lines  38   a ,  39   a.    
     In the first embodiment, the cutting machine  32  is not limited to an inner circumference blade cutting machine. 
     In the first embodiment, when the lens block  11  is cut, the lens block  11  may be held by a chuck. 
     In the first embodiment, the lens block  11  may be formed by two members or three members to hold the mother rod lenses  12 . 
     In the first embodiment, the lens block  11  may hold a plurality of mother rod lenses  12  arranged in two or more rows. 
     The lens blocks  11 ,  51  may have three side surfaces, five side surfaces, or more side surfaces. 
     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.