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

Claim 7:
8. An optical assembly, comprising:
a barrel having an inner wall and including a cavity having a center axis;
a plurality of components mounted sequentially in the cavity of the barrel, the plurality of components comprising, successively:
a first optical element;
a first retaining ring affixed to the barrel through a set of ring threads complementary to a set of barrel threads provided in the cavity, the first retaining ring having a rearward periphery comprising a spacer-mounting surface that is precisely centered within the cavity;
a second optical element, said second element having a forward periphery comprising a spacer-abutting surface;
a second retaining ring; and

a resilient spacer provided between the first retaining ring and the second optical element, the resilient spacer having an unthreaded cylindrical wall and opposite frontward and rearward rims in engagement with the spacer-mounting surface and the spacer-abutting surface, respectively, the frontward rim comprising a frontward rim edge engaging the spacer-mounting surface along a circular edge contact line, 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;, wherein the first optical element is secured between the first retaining ring and a seat provided in the cavity, and the second optical element is secured between the second retaining ring and the resilient spacer;, 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 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 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 a resulting force is applied to the resilient spacer by the engagements of the frontward and rearward rims with the spacer-mounting surface and the spacer-abutting surface, respectively, said resulting force being directed towards the inner wall of the barrel.