DEVICE FOR CORRECTING ERROR OF OPTICAL SCANNING BY ROTARY POLYHEDRAL BODY MIRROR

摘要

PURPOSE:To correct a shift from a scanning reference position of a beam as soon as it is generated, by dividing a reflected beam, directing of a part thereof to the surface of a photosensitive body, directing another part to a two-divided optical sensor, and detecting an error quantity in the whole line area by this sensor. CONSTITUTION:As for a modulating signal input 11 which reaches an optical modulator 2, first of all, a correcting signal from a two-divided optical sensor 9 is amplified 12, becomes a light quantity correcting signal through signal processing circuits 13, 13', an it is mixed 14. On the other hand, an uneven pitch detecting and correting signal from the two-divided optical sensor 9 is amplified 15, an output brought to a signal processing 16 is held by using an S/H amplifier 19, and as for a holding signal (d), that which is obtained by waveform-shaping 18 a start synchronizing signal output 17 and mixing it with the modulating signal 11 is used. An output of the S/H amplifier 19 becomes a correcting signal of an uneven pitch and a scanning start timing by a facet surface inclination and an axial deflection of a rotary polyhedral body mirror, it is frequency- converted 21, and thereafter, mixed 22 with the modulating signal whose light quantity has been corrected, amplified 23, applied to the optical modulator 2, and all corrections are executed.