Metal mold manufacturing method, metal mold, optical element, and optical element manufacturing method

Abstract

A material of a cemented carbide having tungsten carbide as a major ingredient is cut and polished into a shape, a silicon coating as a protecting layer is applied thereto by the plasma CVD method, and a chromium nitride coating with a thickness of 1 μm is applied thereto to form a preliminary shape metal mold. The shape of the formed preliminary shape metal mold or the shape of a sample formed with the preliminary shape metal mold is measured, and from the manufacture error thereof, the shape correction amount of a preliminary shape metal mold 30 for use as a drag is obtained. Based on the obtained shape correction amount, correction by etching is performed on a drag molding surface 301 of the drag preliminary shape metal mold 30 so that a predetermined precision is obtained, thereby completing the metal mold. An optical element or a part is manufactured by use of the metal mold.

What is claimed is:  
     
         1 . A method of manufacturing a metal mold for molding an object, comprising: 
 preparing a preliminary shape metal mold having a shape approximate to an outside shape of the object; and    a processing to obtain a molding surface by selectively removing a surficial part of the preliminary shape metal mold by etching.    
     
     
         2 . A method according to  claim 1 , wherein said processing includes: 
 correcting a shape of a surface of the preliminary shape metal mold by selectively etching the surface of the preliminary shape metal mold in accordance with a shape correction amount determined through prior measurement.    
     
     
         3 . A method according to  claim 2 , wherein the shape correction amount is determined through measurement of a surface shape of the preliminary shape metal mold not having undergone etching yet.  
     
     
         4 . A method according to  claim 2 , wherein said processing includes: 
 forming a sample of the object by use of the preliminary shape metal mold not having undergone etching yet; and    determining the shape correction amount through measurement of an amount in which a surface shape of the sample is reflected.    
     
     
         5 . A method according to  claim 2 , wherein said processing includes: 
 forming a sample of the object by use of the preliminary shape metal mold not having undergone etching yet; and    determining the shape correction amount through measurement of optical performance of the sample.    
     
     
         6 . A metal mold for molding an object, comprising: 
 a first portion of molding surface obtained by a preliminary manufacturing stage; and    a second portion of molding surface obtained by selectively removing a surficial part obtained by the preliminary manufacturing stage by etching in accordance with a predetermined shape correction amount.    
     
     
         7 . A metal mold according to  claim 6 , wherein the shape correction amount is determined through prior measurement.  
     
     
         8 . A metal mold according to  claim 7 , wherein the shape correction amount is determined through measurement of shape of a surface obtained by the preliminary manufacturing not having undergone etching yet.  
     
     
         9 . A metal mold according to  claim 7 , wherein a sample of the object is formed by use of the mold obtained by the preliminary manufacturing not having undergone etching yet and the shape correction amount is determined through measurement of an amount in which a surface shape of the sample is reflected.  
     
     
         10 . A metal mold according to  claim 7 , wherein a sample of the object is formed by use of the mold obtained by the preliminary manufacturing not having undergone etching yet and the shape correction amount is determined through measurement of optical performance of the sample.  
     
     
         11 . A method of manufacturing an optical element, comprising: 
 preparing a preform having a shape approximate to an outside shape of the optical element; and    processing for obtaining the optical element by selectively etching a surface shape of the preform.    
     
     
         12 . A method according to  claim 11 , wherein said processing includes: 
 selectively etching a surface of the preform in accordance with a shape correction amount determined through prior measurement.    
     
     
         13 . A method according to  claim 12 , wherein said processing further includes: 
 determining the shape correction amount through measurement of an amount in which the surface shape of the preform is reflected.    
     
     
         14 . A method according to  claim 12 , wherein said processing further includes: 
 determining the shape correction amount through measurement of optical performance of the preform.    
     
     
         13 . A method according to claims  11 , wherein the optical element has a plurality of optical surfaces successively acting on incident light, and 
 in the etching, the optical surfaces are corrected all together by selectively etching a specific one of the optical surfaces.    
     
     
         14 . A method according to  claim 13 , wherein the optical surfaces include a substantially plane part, and the substantially plane part is selected as the specific optical surface.  
     
     
         15 . A method according to  claim 11 , wherein the optical element is not more than 1 mm in diameter.