Patent ID: 8049974

Claim:
An apparatus comprising: a first part having first, second and third surface portions that are angularly offset from each other about an axis, and that each face inwardly in relation to said axis, wherein for each of said first, second and third surface portions, a radial distance from said axis to the surface portion decreases progressively in a given direction along said axis; and a second part having fourth, fifth and sixth surface portions that are angularly offset from each other about said axis, and that each face outwardly in relation to said axis, wherein for each of said fourth, fifth and sixth surface portions, a radial distance from said axis to the surface portion decreases progressively in said given direction along said axis, and wherein each of said fourth, fifth and sixth surface portions faces, is closely adjacent to, and is substantially congruent in shape with a respective one of said first, second and third surface portions; wherein one of said first and second parts is an optical component; wherein said first part has a seventh surface portion facing approximately opposite said given direction; wherein said second part has an eighth surface portion facing approximately in said given direction and engaging said seventh surface portion; wherein said first part has a first annular surface extending around said axis such that a radial distance from said axis to said first annular surface decreases progressively in said given direction along said axis, said first, second and third surface portions being respective portions of said first annular surface; wherein said second part has a second annular surface extending around said axis such that a radial distance from said axis to said second annular surface decreases progressively in said given direction along said axis, said fourth, fifth and sixth surface portions being respective portions of said second annular surface; wherein said first part has a third annular surface extending around said axis, said seventh surface portion being a portion of said third annular surface; wherein said second part has a fourth annular surface extending around said axis, said eighth surface portion being a portion of said fourth annular surface; wherein said first part includes a first concave surface immediately adjacent to said third annular surface, said third annular surface extending radially outwardly from an outer peripheral edge of said first concave surface; and wherein said second part includes a first convex surface immediately adjacent to said fourth annular surface, said fourth annular surface extending radially outwardly from an outer peripheral edge of said first convex surface, and said first convex surface being in a complementary facing relationship with said first concave surface to form a first air gap therebetween.