Lens and optical pickup device

Abstract

A metal mold including: a first inner metal mold which forms a first lens surface and a first flat surface portion of a lens; a first outer metal mold which forms a second flat surface portion; a second inner metal mold which forms a second lens surface and a third flat surface portion; and a second outer metal mold which forms a fourth flat surface portion, and wherein a first protruded portion which forms a first concaved portion on the lens is formed all around an outer periphery of the first inner metal mold, the first concaved portion serving as clearance for a burr, and a second protruded portion which forms a second concaved portion on the lens is formed all around an outer periphery of the second inner metal mold, the second concaved portion serving as clearance for a burr.

What is claimed is: 
     
         1 . A lens made of resin, comprising:
 a first lens surface;   a second lens surface formed on a reverse side of the first lens surface;   a first flat surface portion that is formed around an outer periphery of the first lens surface and is a ring-shaped surface perpendicular to an optical axis of the lens;   a second flat surface portion that is formed around an outer periphery of the first flat surface portion and is positioned closer to a side of the second lens surface than the first flat surface portion, the second flat surface portion being a ring-shaped surface perpendicular to the optical axis of the lens; and   a first concaved portion formed all around an outer periphery of the first flat surface portion, the first concaved portion serving as clearance for a burr which occurs at a boundary between the first flat surface portion and the second flat surface portion;   wherein:   the first concaved portion is formed such that a position on the first concaved portion approaches to the second lens surface as the position on the first concaved portion separates from the optical axis; and   a point in the first concaved portion nearest to the second lens surface is positioned on the first lens surface side with respect to the second flat surface portion in the optical axis direction.   
     
     
         2 . The lens according to  claim 1 , further comprising:
 a third flat surface portion that is formed around an outer periphery of the second lens surface and is a ring-shaped surface perpendicular to the optical axis of the lens;   a fourth flat surface portion that is formed around an outer periphery of the third flat surface portion and is positioned closer to a side of the first lens surface than the third flat surface portion, the fourth flat surface portion being a ring-shaped surface perpendicular to the optical axis of the lens; and   a second concaved portion formed all around an outer periphery of the third flat surface portion, the second concaved portion serving as clearance for a burr which occurs at a boundary between the third flat surface portion and the fourth flat surface portion,   wherein:   the second concaved portion is formed such that a position on the second concaved portion approaches to the first lens surface as the position on the second concaved portion separates from the optical axis; and   a point in the second concaved portion nearest to the first lens surface is positioned on the second lens surface side with respect to the fourth flat surface portion in the optical axis direction.   
     
     
         3 . An optical pickup device, comprising:
 a lens according to  claim 1 ; and   a lens holder configured to hold the lens at the first flat surface portion.   
     
     
         4 . An optical pickup device, comprising:
 a lens according to  claim 2 ;   a lens holder configured to hold the lens at the first flat surface portion; and   a cap configured to cover the fourth flat surface portion.