| 摘要 |
PURPOSE:To measure only the original jitter component due to the factor of a polygon scanner itself while making the influence of external environment hard to affect, by providing a voltage comparator, an output means and a differentiator. CONSTITUTION:When the mirror surface 2 of a polygon scanner 1 is irradiated with the laser beam from laser 3, the reflected beams from two different points of the mirror surface 2 are subjected to beam/electricity conversion by beam detectors 4 to be inputted to a waveform shaping circuit 15 while amplified by amplifiers 10. The input signals are compared with a predetermined preset threshold value by the voltage comparators 11 of the circuits 15. An input signal (a) is differentiated by a differentiator 13 and the zero volt level of the output thereof is detected by a voltage comparator 14. Next, pulse signals (d), (b) are inputted to an output means 12 and, only when both of them are a + level, a pulse signal (e) is outputted from the means 12. The pulse signal (d) is outputted on the basis of the reflected beams from two points of the polygon mirror and, by measuring the change of the time difference of both pulses, the jitter of the polygon mirror is measured. |
