Patent ID: 6040923
Filing Date: 2000-03-21
Classification: G03G,H04N

Abstract:
A paper transfer control apparatus used for optical image reading apparatus that detects paper, which is transferred by a transfer mechanism, using one or more sensors, and optically reads an image on the paper, the paper transfer control apparatus comprising:a transmission-type sensor detecting the paper;a reflection-type sensor detecting the paper;a sensor mode selecting unit for selecting one of said sensors;a transmission-type sensor processing unit performing paper detection processing for said transmission-type sensor, based on a detection signal of the transmission-type sensor when selected by said sensor mode selecting unit; anda reflection-type sensor processing unit performing paper detection processing for said reflection-type sensor, based on a detection signal of the reflection-type sensor when selected by said sensor mode selecting unit,wherein each of said transmission-type sensor processing unit and said reflection-type sensor processing unit comprises:a paper pass detection processing unit for detecting information regarding paper pass from change of sensor detection levels regarding front and back edges of the paper; anda double-feed detection processing unit for detecting double-feed of paper based on the sensor detection level,wherein said double-feed detection processing unit of said transmission-type sensor processing unit comprises:a criterion-level setting unit for obtaining a sensor output L at the time of transferring the first sheet of paper in a criterion-level setting range having an upper limit Lup and a lower limit Ldown based on a quantity of light transmitted from a base color portion of paper by controlling light emission current of a sensor, detecting a sensor output corresponding to the quantity of light transmitted from the base color portion of the paper within the criterion-level setting range, and setting a criterion-level for double-feed decision, L0; anda double-feed decision unit for setting a lower decision limit Lr1 and an upper decision limit Lr2 based on the criterion-level for double-feed decision, L0 that is set by said criterion-level setting unit, deciding to be double-feed of paper presently being transferred if the sensor output L becomes equal to or lower than said lower decision limited Lr1 when the second and later sheets of paper are transferred, and deciding to be double-feed of the first sheet of paper if the sensor output L becomes equal to or larger than said upper decision limit Lr2.