Photoelectric system for detecting objects in a zone including vibrating light source

Claim 1

A SYSTEM FOR DETECTING THE PRESENCE OF LIGHT OPAQUE MATERIALS IN A PRESELECTED ZONE WHICH COMPRISES: A LIGHT SOURCE MOUNTED TO VIBRATE IN RESPONSE TO LOCAL VIBRATIONS TO CAUSE A LIGHT BEAM THEREFROM TO OSCILLATE; MEANS FOR DIRECTING THE LIGHT BEAM FROM SAID SOURCE IN A PATH THROUGH SAID PRESELECTED ZONE; LIGHT SENSITIVE MEANS POSITIONED TO PERIODICALLY RECEIVE THE OSCILLATING BEAM TO PRODUCE A FIRST INTERMITTENT ELECTRICAL SIGNAL THEREFROM; PEAK DETECTOR MEANS HAVING A TIME CONSTANT LONGER THAN THE OSCILLATION PERIOD OF SAID BEAM CONNECTED TO RECEIVE SAID FIRST ELECTRICAL SIGNAL AND PRODUCE A SUBSTANTIALLY STEADY SECOND ELECTRICAL SIGNAL THEREFROM; AND INDICATING MEANS CONNECTED TO RECEIVE SAID SECOND ELECTRICAL SIGNAL AND INDICATE ATTENUATION OF SAID BEAM RESULTING FROM THE PRESENCE IN SAID PATH OF SAID LIGHT OPAQUE MATERIALS.