Photosensitive apparatus for deriving registrations between relatively movable members

Claim 1

APPARATUS IN WHICH THE RELATIVE DISPLACEMENT OF MOVABLE FIRST AND SECOND MEMBERS ALONG A GIVEN LOCUS IS TO BE DETERMINED BY MOVING A SCANNER MEMBER ALONG THE LOCUS INTO REGISTRATION WITH EACH OF THE TWO MEMBERS IN TURN, SAID APPARATUS COMPRISING: SAID MEMBERS; A FIRST PATTERN SUPPORT MEMBER ASSOCIATED WITH SAID FIRST MEMBER AND MARKED WITH A FIRST RANDOM PATTERN INCLUDING A NON-PERIODIC MULTIPLICITY OF RANDOMLY DISPOSED PATCHES HAVING A FIRST TRANSMISSION FACTOR TO RADIATION ON A GROUND HAVING A SECOND TRANSMISSION FACTOR TO SAID RADIATION; A SECOND PATTERN SUPPORT MEMBER ASSOCITED WITH SAID SECOND MEMBER AND MARKED WITH A SECOND RANDOM PATTERN INCLUDING A NON-PERIODIC MULTIPLICITY OF RANDOMLY DISPOSED PATCHES HAVING A FIRST TRANSMISSION FACTOR TO RADIATION ON A GROUND HAVING A SECOND TRANSMISSION FACTOR TO SAID RADIATION; A SCANNER MEMBER; A THIRD PATTERN SUPPORT MEMBER ASSOCIATED WITH SAID SCANNER MEMBER AND MARKED WITH A THIRD RANDOM PATTERN OF PATCHES ON A GROUND, IDENTICAL WITH SAID SECOND RANDOM PATTERN; A FOURTH PATTERN SUPPORT MEMBER ASSOCIATED WITH SAID SCANNER MEMBER AND MARKED WITH A FOURTH RANDOM PATTERN OF PATCHES ON A GROUND, IDENTICAL WITH SAID SECOND RANDOM PATTERN; MEANS FOR MOVING SAID SCANNER MEMBER SO AS TO REPEATEDLY EXPLORE THE LOCUS AND BRING SAID THIRD AND FOURTH PATTERN SUPPORT MEMBERS INTO REGISTRATION WITH SAID FIRST AND SECOND PATTERN SUPPORT MEMBERS RESPECTIVELY; MEANS FOR DIRECTING A MACROSCOPIC BEAM OF RADIATION THROUGH SAID FIRST AND THIRD RANDOM PATTERNS AND THROUGH SAID SECOND AND FOURTH RANDOM PATTERNS; MEANS FOR DETECTING RADIATION TRANSMITTED THROUGH SAID PATTERNS AND FOR DETERMINING RADIATION PEAKS INDICATIG AN EXACT REGISTRATION BETWEEN SAID FIRST AND THIRD RANDOM PATTERNS AND BETWEEN SAID SECOND AND FOURTH RANDOM PATTERNS; AND MEANS FOR MEASURING THE DISPLACEMENT OF SAID SCANNER MEMBER ALONG THE LOCUS BETWEEN SAID REGISTRATIONS.