Abstract: Reflection-type photoelectric switching apparatus comprising a housing having a transparent front window, a light projecting device, a light receiving device arranged in side-by-side relation with the light projecting device, the light projecting and receiving devices enclosed in the housing and in a predetermined space between the devices and the 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 mechanism controllable from outside of the housing for driving said screen to continuously adjust an effective area of said pair of transparent portions thereof, so that a detection field defined by a common zone, in which the projected and reflected light ray bundles are crossed, is continuously variable with said adjusting mechanism.

Abstract: A photoelectric switch comprising a housing which encloses at least a light emitting element or a light responsive element. The housing consists of two opaque plastic shells welded to each other by ultrasonic welding and a window means of transparent plastic simultaneously welded to the shells by said ultrasonic welding. The window means is formed and attached to the shells in such a manner that it includes no peripheral portion which is in parallel with the direction of ultrasonic welding pressure.