Optical method for light diffraction, corresponding optical system and device

Abstract

The invention concerns a light diffraction optical method covering a wide wavelengths range, a optical system and a optical measuring device corresponding. According to the optical method, at least one incident light beam ( 21 ) is sent to a surface of an optical system ( 1 ), according to a angle of incidence (α) relative to the normal line ( 20 ) to the surface, the optical system comprising a Bragg reflector ( 2 ) and a grating ( 3 ) engraved on the Bragg reflector ( 2 ) on the surface. At least one returned beam ( 22 ) is sent by the optical system according to an angle of diffraction (β) relative to the normal line after diffraction. The wavelengths and the angle of incidence of at least one of the incident beams are such that this incident beam is diffracted by the Bragg reflector and/or by the grating.

1 . A light diffraction optical method wherein: 
 at least one incident light beam ( 21 ,  25 ) having at least a wavelength is sent onto a surface ( 8 ) of an optical system ( 1 ) having a normal axis ( 20 ), according to a direction of Incidence forming an angle of incidence (α) relative to said normal axis ( 20 ), said optical system ( 1 ) comprising a Bragg reflector ( 2 ) and a grating ( 3 ) engraved on the Bragg reflector ( 2 ) at said surface ( 8 ), and    at least one returned beam ( 22 ,  26 ) is collected by the optical system ( 1 ) according to at least one diffraction direction forming an angle of diffraction (β) with respect to the normal axis ( 20 ), after diffraction of the incident beam ( 21 ,  25 ) by the optical system ( 1 ),    characterised in that said wavelengths and said angle of incidence (α) of at least one of the incident beams ( 21 ) are such that said incident beam ( 21 ) is diffracted by the Bragg reflector ( 2 ) and/or by the grating.    
     
     
         2 . An optical method according to  claim 1 , characterised in that the Bragg reflector is a crystal.  
     
     
         3 . An optical method according to one of the claims  1  or  2 , characterised in that said angle of incidence (α) is ranged between 5° and 80°.  
     
     
         4 . An optical method according to any of the  claims 1  to  3 , characterised in that said wavelengths are ranged between 0.1 nm and 0.7 nm.  
     
     
         5 . An optical method according to any of the  claims 2  to  4 , characterised in that the Bragg reflector ( 2 ) is composed of oriented silicon monocrystals (111).  
     
     
         6 . An optical method according to any of the previous claims, characterised in that the grating ( 3 ) is covered with a metallic layer ( 4 ).  
     
     
         7 . An optical method according to any of the previous claims, characterised in that said wavelengths and said angle of incidence (α) of at least another of the incident beams ( 25 ) are such that said incident beam ( 25 ) is diffracted by the grating ( 3 ).  
     
     
         8 . An optical method according to  claim 7 , characterised in that said angle of incidence (α) of said other incident beam ( 25 ) is at least equal to 70°.  
     
     
         9 . An optical method according to one of the claims  7  or  8 , characterised in that said wavelengths of said other incident beam ( 25 ) are comprised between 0.6 nm and 150 nm.  
     
     
         10 . An optical method according to any of the previous claims, characterised in that said incident beams are polychromatic luminous beams.  
     
     
         11 . An optical method according to any of the  claims 1  to  9 , charact rised in that said incident beams are monochromatic luminous beams.  
     
     
         12 . An optical system ( 1 ) comprising a Bragg reflector ( 2 ), characterised in that it comprises a diffraction grating ( 3 ) engraved on the Bragg reflector.  
     
     
         13 . An optical system according to  claim 12 , characterised in that the Bragg reflector is a crystal.  
     
     
         14 . An optical system ( 1 ) according to  claim 13 , characterised in that the Bragg reflector ( 2 ) is composed of a silicon monocrystal.  
     
     
         15 . An optical measuring device comprising: 
 an optical system ( 1 ) according to one of the  claims 12  to  14 ,    means for lighting ( 51 ) said surface ( 8 ) of the optical system ( 1 ) by means of at least one incident light beam ( 21 ,  25 ),    means for collecting ( 52 ) at least one returned beam ( 22 ,  26 ) by the optical system ( 1 ) after diffraction of said incident beams ( 21 ,  25 ) by the optical system ( 1 ), and    rotary means ( 53 ) relative of the optical system ( 1 ) with respect to said incident beams ( 21 ,  25 ).    
     
     
         16 . A use of the optical measuring method according to any of the  claims 1  to  11  or of the device according to one of the  claims 12  to  15 , for a primary calibration for measuring wavelengths or for dispersion in a monochromator.