| 摘要 |
PURPOSE:To provide a scanning optical device in which a deviation in a focusing position can be easily detected and corrected by a simple constitution. CONSTITUTION:A beam spot detector 7 is arranged on the extension of an optical beam scanning surface 6. The beam spot detector 7 is equipped with a mask having both sides, one of which the optical beam vertically crosses and the other side of which the optical beam obliquely crosses ahead of the detector 7. The output of the detector 7 is differentiated by a differentiating circuit 9, and both positive and negative peak values are held by a peak hold circuit 10. A CPU 11 obtains the diameters in the main and sub-scanning directions of the optical beam from the peak value, and outputs an adjustment signal when the focus deviates. On the other hand, a counter 14 obtains the width of the output signal of the beam spot detector 7, and outputs it to a CPU 15. The CPU 15 compares it with a reference value, detects the deviation in a position (registration deviation) in the sub-scanning direction, and outputs the correction signal. |
