Applied Optics 1 March 2023 – The wavefront distortion (WFD) of a surface with an optical filter coating is ideally measured at the operating wavelength and angle of incidence of the filter. However, this is not always possible, requiring that the filter be measured at an out-of-band wavelength and angle. Since the transmitted wavefront error (TWE) and reflected wavefront error (RWE) can depend on the measurement wavelength and angle, an out-of-band measurement may not give an accurate characterization of the WFD. In this paper, we will show how to predict the wavefront error (WFE) of an optical filter at the in-band wavelength and angle from a WFE measurement at an out-of-band wavelength and different angle.

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