| 摘要 |
PURPOSE:To prevent the generation of compressive stress and clatter in a plastic lens on account of a change in temp. by providing a grade to one end face of the collar of said lens and providing the same grade to the engaging surface of a lens barrel or a retaining ring as well. CONSTITUTION:A grade is provided at a prescribed angle theta to one end face of the collar 12 of a plastic lens 11. A graded surface 16 having the same angle theta is also provided to the engaging surface of a lens barrel 15. A recess 17 having the inside diameter larger by delta than the outside diameter of the lens 11 is provided on the inside surface of the barrel 15. The graded surface 13 of the lens 11 is engaged with the graded surface 16 of the barrel 15 and is fixed by a retaining ring 20. Even if the lens 11 expands or contracts on account of a change in temp., the lens 11 expands or contracts freely along the graded surface 16 and the flat end face 21 of the ring 20 and therefore the compressive stress and clatter of the lens are prevented. |
