Patent ID: 6639620
Filing Date: 2003-10-28
Classification: G02B,G06K,H04N

Abstract:
A light beam scanning apparatus comprising:a light emitting device which outputs a light beam; a light beam scanning member which allows a light beam output from the light emitting device to scan toward a scanned face so that said light beam scans said scanned face in a main scanning direction; a pair of sensors which are arranged on said scanned face or a position equivalent thereto, which detect a light beam scanned by said light beam scanning member, and which output an electric signal; a processing circuit which has a plurality of operational amplifiers, which corrects an output from each of said pair of sensors to obtain corrected electric signals, and which integrates a difference between the corrected electric signals; a control section which determines the necessity of correction based on a value integrated by the processing circuit, which determines a scanning position of said light beam according to a value integrated by said processing circuit when the necessity of correction is not determined, and which sets a correction amount based on a value integrated by said processing circuit and an offset amount present in each operational amplifier in said processing circuit when the necessity of correction is determined; and a correction signal generation circuit which outputs a correction signal to said processing circuit so as to correct an electric signal output from each of said pair of sensors based on a correction amount set in the control section, wherein said control section sets a correction amount for each specified correction width based on a value integrated by said processing circuit and an offset amount present in each operational amplifier in said processing circuit and further sets a correction amount by using a finer correction width than said specified correction width when said specified correction width cannot detect a passage position of said light beam.