| 摘要 |
PROBLEM TO BE SOLVED: To offset a change in the optical characteristic of a scanning lens group due to a change of temperature by the otpical characteristic change of a cylindrical lens made of synthetic resin. SOLUTION: The reference surface 11a of a glass part 11 in a composite cylindrical lens 10 consisting of the glass part 11 and a synthetic resin part 12 is fixed on a prescribed position of a housing 1 and the approximately center of the glass part 11 is positioned so as to be put on an optical axis O from a semiconductor laser beam souruce up to a rotary polygon mirror 4. Since the lens 10 is constituted of two materials, i.e., synthetic resin and glass, the optical characteristic of the lens 10 can be maintained even when an environmental temperature in using is changed. |
