摘要 |
PURPOSE: To surely hold a pair of mirrors on a frame while keeping a sufficient positional accuracy of the mirror and to reduce the assembly man-hour and cost by pressing and holding the non-reflection surface sides of a pair of mirrors in the vicinity of their longitudinal intermediate parts by the leading edge of a spring. CONSTITUTION: A mirror unit 48 is provided with a 2nd mirror 64, a 3rd mirror 66 and a frame 144. The 2nd and the 3rd mirrors 64 and 66 are respectively laid between side walls 144A, placed on supporting projections 146 and 148, and positioned in a state where their reflection surfaces are opposed to each other at the relative angle of 90 deg.. The spring 150 is attached to the base part 144B of the frame 144, and the leading edge of the spring 150 presses and holds the non-reflection surface sides of the 2nd and 3rd mirrors 64 and 66 laid between the side walls 144A in the vicinity of their longitudinal intermediate parts. Thus, a pair of mirrors 64 and 66 is surely held by the single spring 150. |