Optical switching system for hand-held bar code reader has hand-wheel with pattern of slits to selectively let through light from photodiode to phototransistor

摘要

The switch consists of a hand-wheel (12) on a shaft (13). The rim of the wheel may have a knurled or toothed profile and projects through a slit in the side of the casing of the bar code reader. - The wheel forms a light barrier (5) between a photodiode (6) and a phototransistor (7) on a U-shaped mounting (100). A pattern of slits (51) in the light barrier lets light through at interval as the wheel is turned.