Scale and manufacturing method of the same

Abstract

A scale includes: a substrate; scale gratings that are formed on a face of the substrate and has a plurality of gratings at a predetermined interval; and a protective layer that is made of fluoride and covers the scale gratings and an exposed portion of the face of the substrate.

What is claimed is: 
     
         1 . A scale comprising:
 a substrate;   scale gratings that are formed on a face of the substrate and has a plurality of gratings at a predetermined interval; and   a protective layer that is made of fluoride and covers the scale gratings and an exposed portion of the face of the substrate.   
     
     
         2 . The scale as claimed in  claim 1 , wherein a thickness of the protective layer is 3 μm or less. 
     
     
         3 . The scale as claimed in  claim 1 , wherein a thickness of the protective layer is 1 μm or less. 
     
     
         4 . The scale as claimed in  claim 1 , wherein a surface of the protective layer is flat or approximately flat. 
     
     
         5 . The scale as claimed in  claim 1 , wherein the fluoride is a polymer of fluorocarbon. 
     
     
         6 . A manufacturing method of a scale comprising:
 forming a protective layer on a face of a substrate by a plasma polymerization, the substrate having scale gratings of a plurality of gratings arranged at a predetermined interval, the protective layer being made of fluoride and covering the scale gratings and an exposed portion of the face of the substrate.   
     
     
         7 . The method as claimed in  claim 6 , wherein, in the forming of the protective layer, a surface of the protective layer is shaped into flat or approximately flat. 
     
     
         8 . The method as claimed in  claim 6 , wherein further comprising:
 forming the scale gratings by etching a layer to be etched that is formed on the face of the substrate, by using a plasma etching device,   wherein, in the forming of the protective layer, the protective layer is formed by a plasma polymerization of the fluoride gas, by changing an operation condition of the plasma etching device.   
     
     
         9 . The method as claimed in  claim 8 , wherein:
 in the forming of the scale gratings, the scale gratings are formed by performing the etching with use of a mask; and   the mask is removed by using the plasma etching device.   
     
     
         10 . The method as claimed in  claim 6 , wherein the fluoride is a polymer of fluorocarbon.