摘要 |
PURPOSE:To prevent the change in the shape of a lens body owing to a change in temp. and to fix the lens in a lens frame by providing plural projecting lines of a narrow width in the lens body and decreasing the frictional resistance in the radial direction in the stage of mounting the lens frame. CONSTITUTION:Projecting lines 33 are formed integrally on the contact surface of a lens 38 with the cylindrical part 32 of a lens frame. The contact area between the lens 38 and the low friction member 37 of the part 32 is decreased and the frictional resistance in said contact part is decreased when the lens 38 is fixed to a lens frame 31. Therefore, the expansion of the lens 38 owing to a change in temp. is easily and surely absorbed by the contact part of the lines 33, and the lens can be fixed to the lens frame in a way as to avoid deformation of the lens 38 owing to the hange in temp. of the body. The similar results are also obtained by providing recessed lines on the contact surface side with a retaining ring 35. |