| 摘要 |
PURPOSE:To measure highly precise jitter quantity by measuring a scan time to a subject surface by a light flux through the deflection surfaces of a light deflector. CONSTITUTION:Light beams radiated from a light source means 1 are formed into a parallel light flux through a collimator lens 2 to be deflected and reflected by a light deflector 3 having plural deflection surfaces, and the light flux is guided into a subject surface through an image forming optical system for optical scan. Light detection parts 4, (5) are provided, so that the light flux passing through condenser lenses 4a, (5a) and aperture parts of slit members 4b, (5b) disposed at focal position of the lenses 4a, (5a) is detected by light detectors 4c, (5c) disposed in rear of the aperture parts, in such a way that the light flux from the light deflector 3 is irradiated to the scan starting side and the scan completing side in the main scan direction of the subject surface directly without passing through the imaging optical system. Jitter quantity is thus detected by utilizing signals obtained at the two light detection parts 4, (5). |
