Proceedings PaperQuantum Efficiency And Phase In Modulation Transfer Function (MTF) Measurement
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This paper gives design considerations for a new MTF machine (ODETA V). The new machine measures optics, but most important feature is rapid MTF measurement of low light level devices like Image Intensifier Tubes. Photon and Detector noise are of paramount importance. A variety of MTF measuring methods is evaluated for noise. They include TV pickup tubes and self scanning photo detector arrays, slit scanning of the line spread function and mask scan methods: Pseudo Noise masks, Hadamard and Moire Sine Wave masks. A new Moire pattern generator is shown. New ODETA V is a programmable MTF machine. It provides a complete MTF read out on CRT (for focussing), X-Y recorder and digital printer. Scan speed (photon integration) is variable in a 20 to 1 range for optimum noise. Single frequency read out can be programmed at up to 5 user selectable frequencies. In this mode very few photons are wasted on the unwanted intervening frequencies. A PTF module is available as an optional extra. Phase is believed to be not really necessary for Image Quality Assessment. It is shown that phase (PTF) is not independent of amplitude. Constraints exist. An ideal MTF precludes bad phase response.