Observation instrument with image converter tube and prism anamorphosers

Claim 1

AN OPTICAL OBSERVING INSTRUMENT COMPRISING AN IMAGE CONVERTER HAVING A PHOTOCATHODE AND A FLUORESCENT SCREEN, A FIRST OPTICAL SYSTEM HAVING AN OPTICAL AXIS FOR PROJECTING AN IMAGE OF A SCENE TO BE OBSERVED ONTO SAID PHOTOCATHODE, SAID FIRST OPTICAL SYSTEM INCLUDING AN OBJECTIVE LENS AND A FIRST PRISM ANAMORPHOSER IN STATIONARY RELATION TO SAID PHOTOCATHODE TO COMPRESS THE IMAGE ON SAID PHOTOCATHODE IN ONE FIXED MERIDIAN PLANE, AND A SECOND OPTICAL SYSTEM HAVING AN OPTICAL AXIS FOR OBSERVING THE FLUORESCENT IMAGE FORMED BY SAID IMAGE CONVERTER ON SAID FLUORESCENT SCREEN, SAID SECOND OPTICAL SYSTEM INCLUDING A SECOND PRISM ANAMORPHOSER IN STATIONARY RELATION TO SAID FLUORESCENT SCREEN DISPOSED SO AS TO HAVE AN ANAMORPHOSING EFFECT OPPOSING THAT OF SAID FIRST PRISM ANAMORPHOSER IN THE SAME FIXED MERIDIAN PLANE WHEREBY SAID FLUORESCENT IMAGE IS DECOMPRESSED, SAID FIRST AND SECOND PRISM ANAMORPHOSERS EACH EXHIBITING SIGNIFICANT VARIATIONS IN ANAMORPHOTIC MAGNITIFICATION ACCORDING TO THE INCLINATION OF INCIDENT PENCILS TO THE RESPECTIVE OPTICAL AXES, THE VARIATIONS IN ANAMORPHOTIC MAGNIFICATION OF SAID FIRST PRISM ANAMORPHOSER BEING IN A SUBSTANTIAL DEGREE COMPENSATED BY THE VARIATIONS IN ANAMORPHOTIC MAGNIFICATION OF SAID SECOND ANAMORPHOSER.