| 摘要 |
PURPOSE:To remove almost completely irregularity of scanning lines, to execute mutually parallel scanning with equal intervals and to attain highly accurate writing/reading of information by finding out the deflection of a correcting optical deflector by the sum of a steady deflection and non-steady deflection. CONSTITUTION:Only a non-steady component is included in an axial deviation value (a) detected by an axial deviation detector and an amplifier 17 finds out non-steady deflection (b) on a scanning line 7 of a scanning optical beam 2 on the basis of the axial distortion value. Position detectors 18, 19 are arranged on a start point just in front of an effective scanning range B and an end point immediately after the range B to detect the position of the scanning beam 2 in the subscanning direction. An computing element 24 outputs a start point deflection (e) and end point deflection (f) stored before one period every deflecting surface of a rotary polygon mirror 6 to find out deflection, i.e. steady deflection (g), from an objective straight scanning position on the way of the scanning in case of linear scanning synchronized with the polygon mirror 6. Then, the correcting deflector 4 is driven in a direction canceling the unevenness of the scanning line on the basis of the sum (g+b) of deflection values. Consequently, the irregularity of the scanning lines can be removed. |
