STANDSTILL BODY DETECTING SENSOR

PURPOSE: To detect randomly reflected light from the other part of an object than a prescribed part without using any carpet for absorbing an projected light beam by arranging light receiving elements which detect the reflected light of the projected light beam converged through an optical element on the outside of the conversing area of the reflected light which forms the image of a prescribed part of the object. CONSTITUTION: A light beam is projected upon a prescribed part X on a floor 4 in front of a door or a ceiling, etc., around the door from a light projecting section through an optical element, such as a convex lens, etc., and reflected light from the prescribed part X is made incident to the optical element, such as the convex lens 7, etc., to form the image A'-B' of the part A-B of the floor 4. The light receiving elements 8 are arranged so that the elements 8 can receive the reflected light from the prescribed part X of the floor 4 in front of the door as much as possible, but do not receive the reflected light from the prescribed part X as much as possible. Namely, the elements 8 are arranged on the outside of the area to which the reflected light from the prescribed part X is made incident so that the elements 8 cannot interfere with the formation of the image A'-B'.