Optical element, spectroscopic apparatus, and method for manufacturing the same

Abstract

An optical element formed of a plurality of materials includes a middle layer between a base material and a reflecting member so as to suppress stripping, cracking and the like of the optical surface due to the difference in coefficients of thermal expansion among the component materials, in the case where a temperature difference in the service environment or a temperature difference between a manufacturing environment and the service environment is large.

What is claimed is: 
     
         1 . An optical element having a plurality of optical surfaces comprising:
 an middle layer between a base material and a reflecting layer, wherein   the base material has a thermal expansion coefficient Tb, the middle layer has a thermal expansion coefficient Ti, the reflecting layer has a thermal expansion coefficient Tr, to meet a relation: Tb<Ti<Tr.   
     
     
         2 . The optical element according to  claim 1 , wherein
 the middle layer contains Cu or Ni as a main ingredient.   
     
     
         3 . The optical element according to  claim 1 , wherein
 a shape of the plurality of optical surfaces of the optical element is formed by the middle layer.   
     
     
         4 . The optical element according to  claim 1 , wherein
 the middle layer has a thickness of 10-3000 μm.   
     
     
         5 . The optical element according to  claim 1 , wherein
 the middle layer comprises a plurality of stacked layers of a plurality of materials.   
     
     
         6 . The optical element according to  claim 5 , wherein
 a layer, among the plurality of stacked layers, directly contacting the base material is formed from a material of which difference in the thermal expansion coefficient from the thermal expansion coefficient of the base material is smallest among the plurality of stacked layers, and   a layer, among the plurality of stacked layers, directly contacting the reflecting layer is formed from a material of which difference in the thermal expansion coefficient from the thermal expansion coefficient of the reflecting layer is smallest among the plurality of stacked layers.   
     
     
         7 . The optical element according to  claim 1 , wherein
 the reflecting layer contains one or more of Au, Ag and Al as a main ingredient.   
     
     
         8 . The optical element according to  claim 1 , wherein
 the optical surface comprises a curved surface or a flat surface, such that normal lines on the plurality of optical surfaces are in different directions.   
     
     
         9 . An optical element having a plurality of optical surfaces comprising:
 an middle layer between a base material and a reflecting layer, wherein   the middle layer contains Cu or Ni as a main ingredient.   
     
     
         10 . The optical element according to  claim 9 , wherein
 a shape of the plurality of optical surfaces of the optical element is formed by the middle layer.   
     
     
         11 . The optical element according to  claim 9 , wherein
 the middle layer has a thickness of 10-3000 μm.   
     
     
         12 . The optical element according to  claim 9 , wherein
 the middle layer comprises a plurality of stacked layers of a plurality of materials.   
     
     
         13 . The optical element according to  claim 12 , wherein
 a layer, among the plurality of stacked layers, directly contacting the base material is formed from a material of which difference in the thermal expansion coefficient from the thermal expansion coefficient of the base material is smallest among the plurality of stacked layers, and   a layer, among the plurality of stacked layers, directly contacting the reflecting layer is formed from a material of which difference in the thermal expansion coefficient from the thermal expansion coefficient of the reflecting layer is smallest among the plurality of stacked layers.   
     
     
         14 . The optical element according to  claim 9 , wherein
 the reflecting layer contains Au as a main ingredient.   
     
     
         15 . The optical element according to  claim 9 , wherein
 the optical surface is a grating of a grating.   
     
     
         16 . A manufacturing method of an optical element having a plurality of optical surfaces comprising:
 manufacturing a base material;   forming an middle layer by a plating on the base material;   forming the optical surface on the middle layer; and   forming a reflecting layer on the middle layer, on which the optical surface is formed.   
     
     
         17 . The manufacturing method according to  claim 16 , wherein,
 during the manufacturing the base material, a configuration foundations the optical surface is formed.   
     
     
         18 . The manufacturing method according to  claim 16 , wherein
 the middle layer contains Cu or Ni as a main ingredient.   
     
     
         19 . The manufacturing method according to  claim 16 , wherein
 the middle layer is formed by a copper sulfate plating.   
     
     
         20 . The manufacturing method according to  claim 16 , wherein
 the reflecting layer is formed by a sputtering process.