SCANNING OPTICAL SYSTEM AND SCANNING OPTICAL DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a scanning optical system which makes it possible to obtain a very small beam spot and to deal with image formation of a large size and a scanning optical device. SOLUTION: The scanning optical device 1 deflects an optical flux by a polygon mirror 5 and converges the luminous flux to a surface 9 to be scanned by means of an fθlens 6, a cylindrical lens 7 and a cylindrical mirror 8. The scanning length at the surface 9 to be scanned is longer than 500 mm and the incident angle in the sub-scanning direction of the incident light on the cylindrical mirror 8 is <=15 deg.. The ratio of the luminous flux diameter DX in the sub- scanning direction of the incident light on the cylindrical mirror 8 and the distance DL between the cylindrical mirror 8 and the surface 9 to be scanned is so set as to satisfy 0.03