Optical system for determining eye characteristics

Claim 1

AN INSTRUMENT FOR DETERMINING VARIOUS REFRACTIVE DEFECTS OF A PATIENT''S EYE, COMPRISING A RAY-SPLITTING SEMI-TRANSMITTING OPTICAL MEANS WHICH SPLIT INCIDENT LIGHT COMING FROM A TEST OBJECT INTO TWO BEAMS OF RAYS OF SIMILAR COLOR AND OF SUBSTANTIALLY HALF OF THE INTENSITY OF SAID INCIDENT LIGHT, EACH OF SAID BEAMS HAVING A DIAMETER LARGER THAN THAT OF THE PUPIL OF SAID EYE INTO WHICH SAID BEAMS ARE DIRECTED AT A SMALL PREDETERMINED ANGLE TO EACH OTHER, EACH BEAM COVERING AND UTILIZING THE FULL SIZE OF SAID PUPIL, SAID BEAMS PROVIDING SIMULTANEOUSLY TWO CONTIGUOUS RETINAL TEST IMAGES OF SUBSTANTIALLY SIMILAR COLOR AND BRIGHTNESS, AND LENS MEANS POSITIONED IN AT LEAST ONE OF SAID BEAMS OF RAYS CAUSING THE RAYS OF ONE BEAM TO DIFFER SPHERICALLY IN VERGENCE FROM THE RAYS OF THE OTHER BEAM WHEN ENTERING THE EYE OF SPHERICAL LENS MEANS IS EMPLOYED FOR THE EXAMINATION OF SPHERICAL EYE DEFECTS, AND TO DIFFER ASTIGMATICALLY FROM ONE ANOTHER IF ASTIGMATIC LENS MEANS IS EMPLOYED FOR THE EXAMINATION OF ASTIGMATIC EYE DEFECT,S THE PATIENT''S EYE FOCUSING SAID BEAMS IN AXIALLY SEPARATED PLANES PERPENDICULAR TO THE VISUAL AXIS, THE SHARPNESS OF SAID CONTIGUOUS IMAGES BEING EASILY COMPARED WITH THE LEAST POSSIBLE EFFORT OF MEMORY.