Patent ID: 11934032
Assignee: INSTITUT NATIONAL D'OPTIQUE
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 12:
13. A kit for precisely centering an optical element mounted in a barrel having an inner wall and including a cavity having a center axis, the barrel being provided with a set of barrel threads, the kit comprising:
a resilient spacer having an unthreaded cylindrical wall and opposite frontward and rearward rims, the frontward rim being engageable with a spacer-mounting surface at a rearward periphery of the optical element, the rearward rim comprising a rearward rim edge, the resilient spacer being resiliently deformable between a compressed state allowing the insertion thereof within the cavity and a biased state in which the cylindrical wall of the resilient spacer contacts the inner wall of the barrel; and
a retaining ring having a set of ring threads complementary to the barrel threads, the retaining ring having a forward periphery comprising a spacer-abutting surface engageable with the rearward rim edge of the rearward rim of the resilient spacer along a circular edge contact line precisely centered within the cavity when the retaining ring is screwed within the barrel, the spacer-abutting surface having a frustro-coni cal profile having an inclination angle α′ with respect to a plane perpendicular to the center axis of the cavity given by the formula:, α
   ′
  
  =
  
   
    sin
    
     -
     1
    
   
   (
   
    
     Y
     
      
       r
       -
      
      ⁢
      r
      ⁢
      i
      ⁢
      m
     
    
    
     
      
       
        [
        
         
          
           d
           
            r
            ⁢
            i
            ⁢
            n
            ⁢
            g
           
          
          
           2
           ⁢
           
            tan
            ⁡
            (
            
             
              φ
              threads
             
             /
             2
            
            )
           
          
         
         -
         h
         -
         
          T
          /
          2
         
        
        ]
       
       2
      
      +
      
       Y
       
        
         r
         -
        
        ⁢
        r
        ⁢
        i
        ⁢
        m
       
       2
      
     
    
   
   )
  
 

where:
Yr_rim is a half-diameter of the rearward rim edge;
dring is a diameter of the retaining ring along the ring threads;
φthread is a value of a thread angle of the ring threads;
h is a distance, in use, between (i) a first point of contact of the barrel threads with the ring threads proximate to the resilient spacer and (ii) the circular edge contact line; and
T is a distance, in use, between (i) the first point of contact of the barrel threads with the ring threads proximate to the resilient spacer and (ii) a last point of contact of the barrel threads with the ring threads farthest from the resilient spacer diametrically opposite to the first point of contact; and

wherein the spacer-abutting surface has an orientation at the circular edge contact line ensuring that, in use, a resulting force directed towards the inner wall of the barrel is applied to the resilient spacer.