Reflection-type photoelectric switching apparatus

Reflection-type photoelectric switching apparatus comprising

• a housing having a transparent front window,
• a light projecting device for projecting a light ray bundle to an object,
• a light receiving device arranged in side-by-side relation with said light projecting device for receiving a reflected light ray bundle from said object,
• said light projecting and receiving devices being enclosed in said housing and in a predetermined space between said devices and said front window,
• an optically opaque screen having a pair of transparent portions corresponding to said light projecting and receiving devices, said screen being slidably disposed in said predetermined space,
• an adjusting means controllable from outside of said housing for driving said screen to continuously adjust an effective area of said pair of transparent portions thereof, said effective area allowing said projected and reflected light ray bundles to pass therethrough, so that a detection field defined by a common zone, in which said projected and reflected light ray bundles are crossed, is continuously variable with said adjusting means.