Traceable interferometry using binary reconfigurable holograms

Abstract

The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. We describe the characterization of a ferroelectric-liquid-crystal-on-silicon (FLCOS) spatial light modulator (SLM) in the production of holograms for use in interferometric metrology. It has already been shown that such a device can be used in producing small-amplitude arbitrary reference surfaces with small but appreciable errors due to the contaminating effect of higher-order structures being propagated through the spatial filter. Here we further quantify the size of these residuals for increasingly large aberrations up to nine waves rms Zernike astigmatism, showing a Zernike-corrected rms wavefront error of roughly 0.06 waves with high vibrational stability. We also present measurements of a vacuum window element using the FLCOS device to drastically reduce interferometric fringe density, showing a residual wavefront error of 0.046 waves rms with dominant components originating from test piece structure rather than holographic errors.

Near-null interferometric test of aspheric cylinders utilizing a partial null lens

“…This is possible if we use an optimization algorithm to control the AO elements to iteratively generate adaptive nulls until the interferogram fringes can be resolved. This adaptive null method for testing aspheric surfaces and freeform surfaces with base shapes of aspheric surfaces has already been investigated [39][40][41][42][43][44][45][46][47][48][49][50][51][52]. However, to the best of our knowledge, the application of the adaptive null method for testing aspheric cylinders or free-form surfaces with base shapes of aspheric cylinders has never been reported previously.…”

Improved wavefront estimation accuracy in a programmable grating array based wavefront sensor

“…In order to address the issue of presence of higher order spots in the case of conventional PGAWS, we implement random binarisation to the transmittance function of the grating array given by equation (5), such that the higher order spots can be reduced to noise by breaking down the periodicity of the diffraction grating pattern [37][38][39][40]. The presence of higher order spots is basically a result of using highly structured diffraction grating pattern.…”