Method of and apparatus for measuring of the contrast-transmission function of an optical system

Claim 1

AN APPARATUS FOR MEASURING THE PERFORMANCE OF AN OPTICAL SYSTEM, PARTICULARLY AS A LENS, COMPRISING A RECTANGULAR WAVE TEMPLATE, A MEMBER DEFINING A SLIT, A LENS POSITIONED BETWEEN SAID TEMPLATE AND SAID SLIT AND RECEIVING LIGHT PASSING THROUGH SAID TEMPLATE AND DIRECTED ONTO SAID SLIT, A PHOTOSENSITIVE CELL RECEIVING LIGHT PASSING THROUGH SAID SLIT, MEANS FOR MOVING SAID RECTANGULAR WAVE TEMPLATE IN A PLANE TO PROVIDE A SCANNING MOTION AND AT SUCH A RATE THAT THE SCANNING SPEED IS CHANGED IN RESPONSE TO THE CHANGING SPATIAL FREQUENCY OF SAID MOVING TEMPLATE, WHEREBY THE ELECTRICAL RECTANGULAR WAVE SIGNAL OUTPUT FROM SAID PHOTOELECTRIC CELL IS OF CONSTANT TIME FREQUENCY, A FILTER REMOVING HARMONICS FROM SAID RECTANGULAR WAVE SIGNAL AND TRANSFORMING THE LATTER TO SINUSOIDAL FORM, AND MEANS FOR DISPLAYING THE FINAL SINUSOIDAL SIGNAL TO VIEW ITS AMPLITUDE AND PHASE.