Optical bar code reader using narrow slit illumination - uses condenser lenses and narrow slits allowing side by side dual scanners to check each other

摘要

The appts. improves the reliability of reading by using a narrow band of illumination with slit filtering of the reflected light. A linear filament incandescent lamp, with a reflector behind, emits a light beam which passes through a condenser lens concentrating the light to a narrow flat beam. The beam is further filtered and narrowed by a slit and a second condenser lens. The light beam is reflected at variable intensity from bar code markings and the reflected beam passes through a condenser lens (10), a slit 11(a), and a second condenser lens (12), before detection by a light detector (13). Increased reliability is possible because the narrow illumination allows the use of two light transmitter-receiver units, placed side-by-side, and having their outputs compared for discrepancies in the character read.