OPTICAL APPARATUS FOR DETECTION OF CODED MARK

摘要

PURPOSE: To minimize the fluctuation of output from a photodetector by providing an opening between a condenser lens and the photodetector and condensing light so as to supply fixed illuminance to the photodetector over the entire area of the focus depth of a bar code scanner. CONSTITUTION: Since a laser beam is practically invisible, a tracking use beam irradiation means 54 is provided and an optical device related to a lamp 56 inside the tracking use beam irradiation means 54 focuses a beam for tracking on a code in front of a beam opening part. The photodetector 66 is arranged at a position out of a beam path so as to detect reflected light made to enter from a beam port and coming from an encoded code focused by the condenser lens 32. Thus, a spectrum beam splitter 62 for reflecting the reflected laser beam on the photodetector 66 is required. The condenser lens 32 and an opening member 92 arranged in front of the photodetector 66 converge the light so as to supply the fixed illuminance over the entire area of the focus depth of the bar code scanner from the front of the beam port.