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

Claim 6:
7. 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-spherical profile having a radius of curvature RRing_rear given by the formula:, R
   Ring_rear
  
  =
  
   
    
     
      [
      
       
        
         d
         
          r
          ⁢
          i
          ⁢
          n
          ⁢
          g
         
        
        
         2
         ⁢
         tan
         ⁢
         
          (
          
           
            φ
            threads
           
           /
           2
          
          )
         
        
       
       +
       
        h
        ′
       
       +
       
        T
        /
        2
       
      
      ]
     
     2
    
    +
    
     Y
     f_rim
     2, where:
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;
Yf_rim is a half-diameter of the frontward rim edge;
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.