Photosensitive object detecting mechanism

Claim 1

OBJECT DETECTING MECHANISM FOR SENSING THE PRESENCE OF A PHYSICAL OBJECT IN AN ENTRANCEWAY DEFINED BETWEEN TWO OPPOSITELY DISPOSED ENTRANCEWAY FRAMING STRUCTURES, SAID DETECTING MECHANISM COMPRISING: (A) A RECEIVER UNIT INCLUDING A PHOTOCELL ADAPTED FOR EXCITATION BY LIGHT ENERGY; (B) A TRANSMITTER UNIT FOR PROJECTING A BEAM OF LIGHT ENERGY FOR EXCITING SAID PHOTOCELL; (C) MEANS FOR ADJUSTABLY MOUINTING SAID RECEIVER UNIT ON ONE OF SAID ENTRANCEWAY FRAMING STRUCTURES; (D) MEANS FOR ADJUSTABLY MOUNTING SAID TRANSMITTER UNIT ON THE OTHER OF SAID OPPOSITELY DISPOSED FRAMING STRUCTURES IN POSITION FOR PROJECTING ITS LIGHT BEAM ACROSS SAID ENTRANCEWAY AND ONTO SAID PHOTOCELL; (E) A LIGHT SHIELD OF OPAQUE MATERIAL ALSO ADJUSTABLY MOUNTED ON SAID ONE OF SAID FRAMING STRUCTURES FOR EXCLUDING LIGHG ENERGY FROM SAID PHOTOCELL, SAID LIGHT SHIELD HAVING A FRONT FACE INTERMEDIATE SAID PHOTOCELL AND SAID TRANSMITTER, SAID FRONT FACE HAVING A CERTAIN APERTURE DEFINED THEREIN, SAID APERTURE BEING DIMENSIONED TO OBTAIN A PIN HOLE LENS OPENING EFFECT CAUSING LIGHT RAYS PASSING THERETHROUGH TO EXIT AT THE SAME ANGLE AT WHICH SUCH RAYS ENTER SAID APERTURE; (F) SAID RECEIVER UNIT, SAID TRANSMITTER UNIT AND SAID LIGHT SHIELD BEING MOUNTED WITH RESPECT TO EACH OTHER ON SAID FRAMING STRUCTURES SUCH THAT ADJUSTMENT OF SAID MEANS FOR ADJUSTABLY MOUNTING SAID RECEIVER UNIT AND SAID TRANSMITTER UNIT PERMITS SAID LIGHT BEAM FROM SAID TRANSMITTER TO PASS THROUGH SAID SHIELD APERTURE AT AN ANGLE NORMAL TO SAID SHIELD FACE AND ONTO SAID PHOTOCELL FOR EXCITATION THEREOF