Object detecting apparatus including photosensors for restricted detection area

摘要

An object detecting apparatus has a plurality of light emitters which are sequentially actuated for projecting sequential light beams. A first structure is provided for receiving beams not reflected off any external body. A second structure is provided for receiving any part of the light beams reflected from an object in the area. A reference phase signal corresponding to the projected light beams is generated. A detection phase signal corresponding to the received reflected beam is also generated. The light emitters corresponding to the reflected light beams are continuously activated. The detection area is restricted by inhibition of output from an alarm phase difference discriminating circuit to a circuit when a difference between the reference and detection phases is not within a predetermined range. Consequently, the detection area can be restricted to a desired range, and the alarm circuit can be retained non-operative unless the object remains continuously in the area. This avoids any malfunction produced by any transitory object, while the actuation of the light projecting means in a very short time sequence accelerates the detecting operation with minimized power consumption.