Patent ID: 11874217
Assignee: COMMISSARIAT A L'ENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 13:
14. A method for manufacturing a device for the photoacoustic characterization of a gaseous substance, the method comprising:, (
   
    
     sin
     ⁢
     α
    
    n
   
   )
  
  >
  
   i
   c
  
 

producing a chamber intended to contain the gaseous substance to characterize, the chamber being delimited at least in part by a first wall, formed in a material, said first wall having an inner face, substantially flat and situated on a side of the chamber, as well as an outer face, the major part of the outer face being flat, contained in a same plane, and being substantially parallel to an average plane of said inner face,
producing, or mounting on the device, a light source that emits a light radiation, the light source being optically associated with the chamber so as to inject said light radiation into the chamber, in the form of a light beam, a part at least of the light beam being reflected on the inner face of the first wall,
wherein producing the chamber comprises producing recesses, etched on the inner face of the first wall, each recess being delimited laterally by a lateral surface, a part of said lateral surface, which is illuminated by said light beam, being tilted, with respect to the average plane of said inner face, by a tilt angle a of less than 90 degrees and which satisfies the following inequality:, α
    -
    
      
        sin
        
          -
          1
        
      
      (
      
        
          sin
          ⁢
          
            
          
          ⁢
          α
        
        n
      
      )
    
  
  >
  
    i
    C
  

where ic is the critical angle of total internal reflection in said material and where n is the optical index of said material.