Electronic servo system

Claim 1

AN ELECTRONIC SERVO APPARATUS FOR FOLLOWING THE CONTOUR OF A LINE PATTERN COMPRISING: (A) A FLYING SPOT SCANNER FOR IMAGING AN ILLUMINATED SPOT ON A SURFACE CONTAINING THE LINE PATTERN, AND OPERATIVE RESPONSIVE TO THE RESPECTIVE MAGNITUDES OF AT LEAST TWO APPLIED CONTROL POTENTIALS TO POSITION THE IMAGE ON THE SURFACE TO ENCOMPASS AN AREA WHICH INCLUDES THE PATTERN; (B) A GENERATOR FOR PRODUCING AN ELECTRICAL SIGNAL HAVING A SINUSOIDAL WAVEFORM; (C) MEANS CONNECTED TO SAID GENERATOR FOR PRODUCING TWO SINUSOIDALLY VARYING ELECTRICAL WAVEFORMS RESPECTIVELY DISPLACED FROM ONE ANOTHER BY ONE QUARTER WAVELENGTH; (D) A PLURALITY OF ATTENUATING DEVICES RESPECTIVELY CONNECTED TO RECEIVE EACH OF THE QUARTER WAVELENGTH PHASE DISPLACED SINUSOIDAL WAVEFORMS, EACH DEVICE BEING OPERATIVE RESPONSIVE TO THE PRESENCE OF AN ELECTRICAL CONTROL SIGNAL TO ATTENUATE THE SIGNAL CONNECTED THERETO, AND IN THE ABSENCE OF THE CONTROL SIGNAL TO PASS THE SIGNAL CONNECTED THERETO WITHOUT ATTENUATION; (E) AN INTEGRATING DEVICE CONNECTED TO EACH OF SAID ATTENUATING DEVICES AND TO SAID FLYING SPOT SCANNER TO SUPPLY THE CONTROL POTENTIALS THERETO; (F) A LIGHT RESPONSIVE DEVICE OPERATIVE RESPONSIVE TO THE CHANGE IN THE ILLUMINATION INTENSITY AS SAID IMAGED SPOT OF LIGHT MOVES INTO SAID LINE TO PRODUCE A POTENTIAL OUTPUT RESPONSE MANIFESTIVE OF THE CHANGE; (G) AND MEANS CONNECTED TO SAID LIGHT RESPONSIVE DEVICE AND TO SAID ATTENUATORS, OPERATIVE RESPONSIVE TO THE POTENTIAL OUTPUT RESPONSE OF SAID LIGHT RESPONSIVE DEVICE TO PRODUCE AN ELECTRICAL CONTROL SIGNAL HAVING A FIXED DURATION SUBSTANTIALLY NOT GREATER THAN ONE HALF THE PERIOD OF SAID SINUSOIDAL WAVEFORM, THE SAID ELECTRICAL SIGNAL BEING OPERATIVE TO CAUSE SAID ATTENUATORS TO ATTENUATE THE INSTANTANEOUS AMPLITUDES OF THE SINUSOIDAL WAVEFORMS ENTERED THEREIN.