Modulation transfer function measurement of a multichannel optical system

We present a new method to measure the modulation transfer function (MTF) beyond the Nyquist frequency of a multichannel imaging system for which all the channels have parallel optical axes. Such a multichannel optical system produces a set of undersampled subimages. If the subimages contain nonredundant information, high spatial frequencies are folded between low spatial frequencies, leading to the possible extraction of frequencies higher than the Nyquist frequency. The measurement of the MTF of the multichannel system leads to the estimation of the resolution enhancement of the final image that can be obtained by applying a postprocessing algorithm to the collection of undersampled subimages. Experimental images are presented to validate this method.