Radiation sensitive fabric flaw detecting systems

Claim 1

DETECTING APPARATUS FOR DETECTING HOLES AND LIKE SELECTED LIGHT MODIFYING CONDITIONS IN WEBS OF MATERIAL WHILE THE MATERIAL IS MOVING ALONG A PROCESSING PATH AND PRODUCING OUTPUT SIGNALS UPON OCCURRENCE OF SUCH SELECTED CONDITIONS COMPRISING A DETECTOR HEAD INCLUDING A SUBSTANTIALLY POINT SOURCE OF LIGHT, AN ELONGATED LENS HAVING A CYLINDRICAL SURFACE DEFINING AN AXIS OF CURVATURE PARALLELING THE LONGITUDINAL AXIS OF THE LENS FOR SPREADING LIGHT RAYS FROM SAID SOURCE SUBSTANTIALLY UNIFORMLY ALONG DIVERGENT INCIDENT RAY PATHS LYING IN A SINGLE PLANE THROUGH SAID AXIS OF CURVATURE TO FORM A LINE IMAGE OF LIGHT AT THE MATERIAL TO BE INSPECTED SPANNING A SELECTED DISTANCE, RETRO-REFLECTIVE MEANS DISPOSED ON THE OPPOSITE SIDE OF SAID MATERIAL FROM SAID DETECTOR HEAD POSITIONED TO RECEIVE LIGHT FROM SAID SOURCE ALONG ANY OF SAID INCIDENT RAY PATHS INTERCEPTED BY SAID SELECTED CONDITIONS IN THE MATERIAL AND RETRO-REFLECT THE SAME BACK ALONG ITS INCIDENT RAY PATH THROUGH SAID LENS, PHOTOCELL MEANS IN SAID DETECTOR HEAD, A SEMI-TRANSPARENT MIRROR BETWEEN SAID LENS AND LIGHT SOURCE TO TRANSMIT LIGHT FROM SOURCE TOWARD SAID LENS AND TO REFLECT ANY OF SAID RETRO-REFLECTED LIGHT RAYS TO SAID PHOTOCELL MEANS, LIGHT MASK MEANS BETWEEN SAID LENS AND SAID MIRROR, HAVING AN ELONGATED LIGHT APERTURE THEREIN ALIGNED WITH SAID LONGITUDINAL AXIS SHAPED TO SUBSTANTIALLY EQUALIZE LIGHT INTENSITY OF RETRO-REFLECTED LIGHT REFLECTED TO SAID PHOTOCELL MEANS ALONG ANY OF SAID RAY PATHS, AND MEANS RESPONSIVE TO A SELECTED LEVEL OF LIGHT ACTIVATION OF SAID PHOTOCELL MEANS TO GENERATE A SIGNAL INDICATIVE OF DETECTIVE OF SAID SELECTED CONDITIONS.