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

Claim 13:
14. A kit for mounting first and second optical elements in a spaced relationship 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 first retaining ring configured for securing the first optical element against a seat provided in the cavity, the first retaining ring having a rearward periphery comprising a spacer-mounting surface precisely centered within the cavity when mounted therein, the first retaining ring comprising a set of ring threads complementary to the set of barrel threads; and
a resilient spacer having an unthreaded cylindrical wall and opposite frontward and rearward rims, 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, the frontward rim of the resilient spacer comprising a frontward rim edge and being engageable with the spacer-mounting surface of the first retaining ring along a circular edge contact line;, wherein the spacer-mounting surface of the first retaining ring has a frustro-conical 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
     
      
       f
       -
      
      ⁢
      r
      ⁢
      i
      ⁢
      m
     
    
    
     
      
       
        [
        
         
          
           d
           
            r
            ⁢
            i
            ⁢
            n
            ⁢
            g
           
          
          
           2
           ⁢
           
            tan
            ⁡
            (
            
             
              φ
              threads
             
             /
             2
            
            )
           
          
         
         +
         
          h
          ′
         
         +
         
          T
          /
          2
         
        
        ]
       
       2
      
      +
      
       Y
       
        
         f
         -
        
        ⁢
        r
        ⁢
        i
        ⁢
        m
       
       2
      
     
    
   
   ), where:
Yf_rim is a half-diameter of the frontward rim edge;
dring is a diameter of the first 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;
wherein the rearward rim of the resilient spacer is configured to engage a spacer-abutting surface of the second optical element when the second optical element is inserted in the cavity rearwardly of the resilient spacer and mounted in said cavity using a second retaining ring; and
wherein the spacer-mounting 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.