Flying spot system for comparing an object with tolerance masks

Claim 1

OPTICAL INSPECTION APPARATUS COMPRISING MEANS TO PROVIDE ILLUMINATION IN THE FORM OF A SPOT OF LIGHT, MEANS TO SCAN SAID SPOT IN A SERIES OF SEQUENTIAL LINES TO COVER AN AREA, MEANS TO BRING LIGHT FROM SAID SPOT TO A FOCUS ON AN OBJECT UNDER OBSERVATION AND ON MASK MEANS DETERMINING MAXIMUM AND MINIMUM ACCEPTABLE LIMITS OF DIMENSIONS OF THE OBJECT, SAID MASK MEANS COMPRISING FIRST AND SECOND MASKING MEMBERS EACH LOCATED IN A PATH OF SAID LIGHT, EACH MEMBER HAVING A REGION WHICH SUBSTANTIALLY PASSES SAID LIGHT AND A REGION WHICH SUBSTANTIALLY BLOCKS SAID LIGHT, EACH OF SAID REGIONS HAVING AN OUTLINE WHICH CORRESPONDS TO THE SHAPE OF SAID OBJECT, ONE OF SAID OUTLINES BEING LARGER THAN THE OTHER SO THAT SAID ONE OUTLINE DEFINES SAID MAXIMUM LIMITS AND SAID OTHER OUTLINE DEFINES SAID MINIMUM LIMITS, MEANS TO RECEIVE THE LIGHT FROM SAID SPOT PASSING SAID OBJECT AND MEANS TO RECEIVE LIGHT FROM SAID SPOT PASSING THE MASKING MEANS, SAID RECEIVING MEANS EACH BEING ARRANGED TO PROVIDE SIGNALS CORRESPONDING TO THE LIGHT PICKED UP, AND MEANS RESPONSIVE TO SAID SIGNALS TO PROVIDE A FURTHER SIGNAL INDICATIVE OF THE POINT-BYPOINT RELATIONSHIP OF THE OBJECT WITH SAID LIMITS.