The spatial frequency response of the pixelated phase mask sensor has been investigated both theoretically and experimentally. Using the small phase step approximation, it is shown that the instrument transfer function can be approximated as the product of the system optical transfer function and the spatial carrier processing filter transfer function. To achieve optimum performance it is important that the bandwidth of the optical imaging system is adequate so that the limiting factor is the detector pixel width. Actual measurements on a commercial Fizeau interferometer agree very well with the theory, and demonstrate detector limited performance. The spatial resolution of the calculated phase map is algorithm dependent; however, both the 2x2 and 3x3 convolution algorithms result in a frequency response that is significantly more than what would be obtained by a simple parsing of the image. Therefore, a 1k x 1k sensor has a spatial frequency response that is approximately equal to the detector limited resolution of a 700 x 700 array with its frequency response extending to the full Nyquist limit of the 1k x 1k array.
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