Photometer using a prism with surface lenticulations

Claim 1

IN A COMPARISON PHOTOMETER INCLUDING A TRANSPARENT TARGET HAVING A REFLECTIVE PATTERN THEREON AND A SOURCE OF LIGHT FOR ILLUMINATING THE PATTERN, THE COMBINATION COMPRISING: (A) MEANS DEFINING AN OPENING FOR ADMITTING LIGHT FROM THE SCENE TO BE PHOTOGRAPHED INTO THE PHOTOMETER; (B) A REFRACTING PRISM ADJACENT SAID OPENING FOR EFFICIENTLY COLLECTING LIGHT FROM THE SCENE, SAID PRISM HAVING A BASE AND PLANAR SURFACES SLOPING DIVERGINGLY AWAY FROM THE SCENE, THE SLOPE OF SAID PLANER SURFACES AND THE BOUNDARIES OF SAID OPENING ESTABLISHING A PREDETERMINED COLLECTION ANGLE FOR LIGHT ENTERING THE PHOTOMETER, SAID BASE HAVING LENTICULAR MEANS FORMED THEREON AND EVENLY SPACED THEREOVER FOR UNIFORMLY DISTRIBUTING THE LIGHT COLLECTED FROM THE SCENE OVER THE AREA OF SAID BASE; (C) MEANS DEFINING A VARIABLE APERTURE ADJACENT SAID BASE, WHEREBY VARYING THE AREA OF SAID APERTURE PRODUCES A PROPORTIONAL CHANGE IN THE AMOUNT OF LIGHT ADMITTED THROUGH SAID APERTURE TO THE TARGET; (D) A DIFFUSER ADJACENT THE TARGET FOR DISPLAYING THE RELATIVE LEVEL OF ILLUMINATION OF THE SCENE; AND (E) AN EYE LENS TO ENABLE THE USER TO FOCUS ON THE TARGET TO COMPARE THE RELATIVE LEVELS OF ILLUMINATION TRANSMITTED THERETHROUGH AND REFLECTED THEREFROM.