| 摘要 |
PURPOSE:To realize fast scan, by containing a light shielding part which prevents the simultaneous incidence of different orders of diffracted light from a reflection type diffraction grating from being performed on the same scanning plane according to the rotation of a rotary polygonal mirror in which the reflection type diffraction grating is formed in a parallel direction with a rotary shaft in the periphery of the rotary shaft. CONSTITUTION:A beam of light from a semiconductor laser 301 is collimated, and it is made incident on the rotary polygonal mirror 304 having six planes on the surface of which the diffraction grating is formed as a parallel beam of light, and only selected diffracted light 309 which satisfies a diffracting condition with an appropriate angle by a slit 306 provided between the polygonal mirror 304 and an Ftheta lens 305 is image-formed and scanned. A beam of light 301 with a different degree diffracted to an unrequired angle is cut by the light shielding part 311 outside the slit. In such a way, it is possible to realize the fast scan by the rotary polygonal mirror having a fewer number of planes or a motor operated at lower speed than a conventional device setting the same system as an on-going system as fundamentals. |
