| 摘要 |
PROBLEM TO BE SOLVED: To secure the stability of molding, to make achievable cost-down by improving the yield, to suppress the generation of birefringence through stress relaxing and to make formable satisfactory images. SOLUTION: This optical system is constituted so as to guide a light beam emitted from a light source means 1 to a deflecting means 5, to transmit the light beam deflected and reflected by this deflecting means 5 through a scanning lens system 11 onto a surface 8 to be scanned, and to scan this surface 8 to be scanned. In this case, the scanning lens system 11 has a spherical lens 6 and a toric lens 7 formed of plastic materials having positive refracting force in both main scanning and sub-scanning directions, and the thickness of this toric lens 7 in the direction of an optical axis within a main scanning cross section is almost fixed. |
