公开(公告)号：JPH05292261A

公开(公告)日：1993-11-05

申请号：JP30851192

申请日：1992-11-18

Applicant: SYMBOL TECHNOLOGIES INC

Inventor： GURETSUGU EI MAAUIN

IPC: G06K7/10 ,  H01S5/042 ,  H04N1/113 ,  H04N1/04 ,  H01S3/096

Abstract: PURPOSE: To prolong the service lives of the important components of a laser scanner, such as a laser diode, scanning motor, etc., and, at the same time, to reduce the power consumption of the components by automatically switching the scanner to a scan mode from a sleep mode. CONSTITUTION: When a laser scanner is in a sleep mode, an object sensor circuit 30 generates a steady-state voltage signal by processing pulse-modulated light reflected from a background surface. Then the circuit 30 generates positive and negative threshold voltage signals (respectively having larger and smaller values than the steady-state voltage signal has) from the steady-state voltage signal. A comparator detects an object when the object is put in the visual field of the scanner by comparing the inputted three signals with each other and also detects the object when the steady-state voltage signal becomes higher or lower than the positive or negative threshold voltage signal in accordance with the reflectance of the object. Upon detecting the object, the comparator instructs the scanner to return to a scan mode without hindering normal scanning processing by supplying a trigger signal to the scanner.