Lens frame, manufacturing method of the same, metal mold for molding the same, and lens positioning method

Abstract

A lens frame capable of accurately holding a lens, a production method thereof, a mold for molding the lens frame, and method for positioning the lens are provided. The lens frame according to the invention includes a cylindrical body and three ribs on an outer circumferential surface of the cylindrical body. The cylindrical body also has an inner circumferential surface including contacting portions where the ribs are formed on the outer circumferential surface, and spaced portions where the ribs are not formed thereon. A radius r 1 of the contacting portions differs from a radius r 2 of the spaced portions by 2 μm or more (r 1 −r 2 >=2 μm).

1 . A lens frame comprising a cylindrical body having at least three ribs on an outer circumferential surface of the cylindrical body on whose inner circumferential surface of the cylindrical body, a difference (r 2 −r 1 ) between a radius (r 1 ) of portions where the ribs are formed and a radius (r 4 ) of other portions is 2 μm or more.  
     
     
         2 . A lens frame as claimed in  claim 1 , wherein the ribs are three ribs disposed at an approximate interval of 120 degrees on the outer circumferential surface of the cylindrical body.  
     
     
         3 . A lens frame as claimed in  claim 1 , wherein the lens frame comprises at least one material selected from a group of materials including polycarbonate, polymethyl methacrylate, acrylonitrile butadiene styrene, polyoxymethylene, and polystyrene.  
     
     
         4 . A lens frame as claimed in  claim 1 , wherein the ribs have a rectangular parallelepiped shape extending in a direction parallel to an axis of the cylindrical body.  
     
     
         5 . A manufacturing method of a lens frame including a cylindrical body having at least three ribs on an outer circumferential surface of the cylindrical body, comprising: 
 preparing a mold for molding a lens frame:    injecting a molding material into a cavity of the mold for molding a lens frame; and    removing the molded lens frame from the cavity of the mold for molding a lens frame,    wherein the mold includes:    an inner mold having a cavity surface for inner circumferential surface, corresponding to the shape of the inner circumferential surface of the cylindrical body; and    an outer mold placed around the inner mold, and comprising: cavity surfaces for outer circumferential surface corresponding to the outer circumferential surface of the cylindrical body; and rib cavity surfaces respectively corresponding to the ribs.    
     
     
         6 . A manufacturing method of a lens frame as claimed in  claim 5 , wherein the ribs are three ribs disposed at an approximate interval of 120 degrees on the outer circumferential surface of the cylindrical body; and 
 the rib cavity surfaces for the ribs are three cavity surfaces corresponding to the ribs.    
     
     
         7 . A manufacturing method of a lens frame as claimed in  claim 5 , wherein the method uses in the injection at least one material selected from a group of materials including polycarbonate, polymethyl methacrylate, acrylonitrile butadiene styrene, polyoxymethylene, and polystyrene.  
     
     
         8 . A manufacturing method of a lens frame as claimed in  claim 5 , wherein the ribs have a rectangular parallelepiped shape extending in a direction parallel to an axis of the cylindrical body.  
     
     
         9 . A manufacturing method of a lens frame as claimed in  claim 5 , wherein the process of preparing the mold for molding a lens frame comprises using a machine tool with an approximate processing accuracy of ±0.1 μm and manufacturing a mold for molding a lens frame.  
     
     
         10 . A mold for molding a lens frame including a cylindrical body having at least three ribs on an outer circumferential surface of the cylindrical body, the mold comprising: 
 an inner mold comprising a cavity surface for inner circumferential surface, corresponding to an inner circumferential surface of the cylindrical body; and    an outer mold placed around the inner mold, and comprising: cavity surfaces for outer circumferential surface corresponding to the outer circumferential surface of the cylindrical body; and rib cavity surfaces respectively corresponding to the ribs, 
 wherein, of the cavity surface for inner circumferential surface, a difference (r 4 −r 3 ) between a radius (r 3 ) of portions facing the rib cavity surfaces and a radius (r 4 ) of other portions is 2 μm or more.  
   
     
     
         11 . A mold for molding a lens frame as claimed in  claim 10 , wherein 
 the ribs are disposed at an approximate interval of 120 degrees on the outer circumferential surface of the cylindrical body; and    the ribs are three ribs disposed at an approximate interval of 120 degrees on the outer circumferential surface of the cylindrical body.    
     
     
         12 . A mold for molding a lens frame as claimed in  claim 10 , wherein: 
 the ribs have a rectangular parallelepiped shape extending in a direction parallel to an axis of the cylindrical body; and    each of the rib cavity surfaces defines a groove of a rectangular parallelepiped shape corresponding to each of the ribs.    
     
     
         13 . A mold for molding a lens frame as claimed in  claim 10 , wherein the mold is manufactured using a machine tool with an approximate processing accuracy of ±0.1 μm.  
     
     
         14 . A mold for molding a lens frame as claimed in  claim 10 , wherein the cavity surface for inner circumferential surface includes portions respectively facing the rib cavity surfaces and having a circularity of 2 μm or less  
     
     
         15 . A positioning method of a lens with respect to a lens frame including a cylindrical body having at least three ribs on an outer circumferential surface of the cylindrical body, the method comprising, of an inner circumferential surface of the cylindrical body, making only portions where the ribs are formed on the outer circumferential surface contact the lens.  
     
     
         16 . A positioning method of a lens as claimed in  claim 15 , wherein the three ribs are disposed at an approximate interval of 120 degrees on the outer circumferential surface of the cylindrical body.  
     
     
         17 . A positioning method of a lens as claimed in  claim 15 , wherein the lens frame comprises a material selected from a group of materials including polycarbonate, polymethyl methacrylate, acrylonitrile butadiene styrene, polyoxymethylene, and polystyrene.  
     
     
         18 . A positioning method of a lens as claimed in  claim 15 , wherein the ribs have a rectangular parallelepiped shape extending in a direction parallel to an axis of the cylindrical body.