Formed lens and optical pickup device

Abstract

A formed lens produced by pressing an optical material so as to shape a predetermined configuration, has an optical surface having a light entrance side, a light exit side and an optical axis. When a normal line angle is defined as an angle formed between the optical axis and a normal line at an arbitrary point on the optical surface, the maximum normal angle is 60° to 90° and an intersection at which the maximum normal line forming the maximum normal line angle intersects with the optical axis is located at the light exit side from the point of the maximum normal line on the optical surface, and Abbe's number νd of the optical material is 60 or more.

What is claimed is:  
     
         1 . A formed lens produced by pressing an optical material so as to shape a predetermined configuration, comprising: 
 an optical surface having a light entrance side, a light exit side and an optical axis;    wherein when a normal line angle is defined as an angle formed between the optical axis and a normal line at an arbitrary point on the optical surface, the maximum normal angle is 60° to 90° and an intersection at which the maximum normal line forming the maximum normal line angle intersects with the optical axis is located at the light exit side from the point of the maximum normal line on the optical surface, and    wherein Abbe's number νd of the optical material is 60 or more.    
     
     
         2 . The formed lens of  claim 1 , wherein when a normal line does not intersect with the optical axis, the normal angle is an angle formed between the optical axis and a line obtained by projecting the normal line on a plane which is parallel to the normal line and includes the optical axis.  
     
     
         3 . The formed lens of  claim 1 , wherein before the optical material is pressed, the optical material is shaped in a preliminary form.  
     
     
         4 . The formed lens of  claim 1 , wherein when an equivalent sphere is defined as a sphere having the same volume of the optical material shaped in the preliminary form, the surface of the preliminary form is located in a space between a spherical surface of a half sphere whose radius is a half of that of the equivalent sphere and a spherical surface of a double sphere whose radius is a double of that of the equivalent sphere.  
     
     
         5 . The formed lens of  claim 1 , wherein the optical surface includes a microscopic structure.  
     
     
         6 . The formed lens of  claim 5 , wherein the microscopic structure is diffractive grooves.  
     
     
         7 . The formed lens of  claim 1 , wherein the optical material has a diffractive index not larger than 1.61 for d-line.  
     
     
         8 . The formed lens of  claim 1 , wherein the optical material is a glass.  
     
     
         9 . The formed lens of  claim 1 , wherein the optical material is a plastic.  
     
     
         10 . The formed lens of  claim 1 , wherein the formed lens is used in an optical pickup device.  
     
     
         11 . An optical pickup device, comprising: 
 a light source to emit a light flux having a wavelength of 450 nm or less;    a light converging system having an objective lens being the formed lens described in  claim 1;  and    a photodetector;    wherein the optical pickup device conducts recording and/or reproducing information by converging the light flux from the light source on an information recording plane of an optical information recording medium through the light converging system.