burkhardt etal

Claim 1

IN AN APPARATUS FOR AUTOMATICALLY SORTING MAIL, WHEREIN THE MAIL IS MARKED WITH A FLURESCENT MATERIAL EMITTING RAYS, UPON EXCITATION, HAVING WAVE LENGTHS LONGER THAN 550 MILLIMICRONS, THE COMBINATION WHICH COMPRISES: MEANS FOR MOVING THE MAIL TO BE SORTED ALONG A PRESELECTED PATH; MEANS SPACED FROM SAID PATH FOR PRODUCING RAYS HAVING WAVE LENGTHS OF SUBSTANTIALLY 254 MILLIMICRONS; TRANSFORMING MEANS ARRANGED BETWEEN SAID RAY PRODUCING MEANS AND SAID PRESELECTED PATH FOR TRANSFORMING SAID RAYS INTO EXCITING RAYS AND DIRECTING SAID EXCITING RAYS TOWARDS SAID PATH SO AS TO IMPINGE ON THE FLUORESCENT MATERIAL MARKED ON THE MAIL, SUBSTANTIALLY ALL OF SAID EXCITING RAYS HAVING WAVE LENGTHS LARGER THAN 254 MILLIMICRONS; FILTER MEANS ARRANGED BETWEEN SAID TRANSFORMING MEANS AND SAID PRESELECTED PATH, SAID FILTER MEANS HAVING A HIGH TRANSMISSION CHARACTERISTIC FOR RAYS HAVING WAVE LENGTHS IN THE REGION BETWEEN 300 AND 400 MILLIMICRONS AND HAVING A LOW TRANSMISSION CHARACTERISTIC FOR ALL OTHER RAYS; AND DETECTING MEANS FOR DETECTING ANY RAYS EMITTED FROM SAID FLOURESCENT MATERIAL DUE TO THE IMPINGEMENT OF SAID EXCITING RAYS THEREON, SAID DETECTING MEANS HAVING A BROAD RECEIVING SPECTRUM THE SHORT-WAVE LIMIT OF WHICH IS APPROXIMATELY 550 MILLIMICRONS.