Freeform alignment is critical and challenging, often relying on mechanical fixturing. We discuss an optical approach based on deflectometry. A pattern on a screen is imaged through the freeform under investigation and the distortion in the pattern is a combination of the freeform surface shape and the alignment condition. The misalignment is evaluated using a Zernike analysis of the image distortion, knowledge of the surface shape, and an empirically-determined misalignment dependence. The approach is investigated through simulation in the context of segment misalignment in a segmented mirror, showing that 5 degrees of freedom of misalignment can be determined with micrometer-scale and micro radian-scale sensitivities.
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