Showing papers on "Mask inspection published in 1968"

Superimposed common carrier mask inspection system

Abstract: A SYSTEM IN WHICH THE POSITION OF THE OPAQUE AREAS ON THE SURFACE OF A FIRST TRANSPARENT PHOTOGRAPHIC MASK ARE COMPARED TO THE POSITIONS OF THE OPAQUE AREAS ON THE SURFACE OF A SECOND TRANSPARENT PHOTOGRAPHIC MASK. THE TWO MASK SURFACE ARE PLACED FACE TO FACE AND SEPARATED BY A LAYER OF MATERIAL POSSESSING THE CHARACTERISTICS OF A "ONE-WAY" MIRROR. A SINGLE TELEVISION CAMERA, FOCUSED ON THE ADJACENT MASK SURFACES, VIEWS THE TWO MASKS WHICH ARE ALTERNATELY ILLUMINATED FROM ABOVE AND BELOW. WHEN ILLUMINATED FROM BELOW, LIGHT IS TRANSMITTED THROUGH BOTH MASKS AND THE "MIRROR", THE IMAGES OF THE OPAQUE AREAS ON BOTH MASKS APPEAR ON A MONITOR. WHEN ILLUMINATED FROM ABOVE, THE "MIRROR" REFLECTS LIGHT AND ONLY THE IMAGE OF THE OPAQUE AREAS ON THE UPPER MASK APPEARS ON THE MONITOR. A "FLECKER EFFECT," OR OTHER VISUAL DIFFERENTIAL DETECTION SYSTEM, INDICATES THE DEGREE OF DEVIATION OF THE POSITIONS OF THE OPAQUE AREAS ON THE FIRST MASK FROM THE SECOND MASK.