Lens holding structure, its assembling method and its dimension determining method

摘要

A structure for holding lenses in which they are inserted into a lens frame in an axial direction thereof for their mounting thereon, and in which a lens that is first inserted into the lens frame is fixed thereto by caulking a part of the lens frame against the lens, so that an enlargement in a radial direction of the lens frame is prevented. The lens frame has three through-holes in a circumferential direction with an equal space therebetween in which the through-holes form around an intermediate position thereof relative to the axial direction, a stepped surface on a first end opposite a second end from which the lens is inserted, and a partial caulking projection which forms inside each hole as a part of the lens frame. After the first lens is inserted from the second end into the lens frame, the partial caulking projection is thermally caulked against a periphery, of the lens, which is downstream relative to the direction in which the lens is inserted, so that the first lens is held between the stepped surface and the partial caulking projection.