Design and analysis of an alignment procedure using computer-generated holograms

A procedure that uses computer-generated holograms (CGHs) to align an optical system's meters in length with low uncertainty and real-time feedback is presented. The CGHs create simultaneous three-dimensional optical references, which are decoupled from the surfaces of the optics allowing efficient and accurate alignment even for systems that are not well corrected. The CGHs are Fresnel zone plates, where the zero-order reflection sets tilt and the first-diffracted order sets centration. The flexibility of the CGH design can be used to accommodate a wide variety of optical systems and to maximize the sensitivity to misalignments. An error analysis is performed to identify the main sources of uncertainty in the alignment of the CGHs and to calculate the magnitudes in terms of general parameters, so that the total uncertainty for any specific system may be estimated. A system consisting of two CGHs spaced 1 m apart is aligned multiple times and re-measured with an independent test to quantify the alignment uncertainty of the procedure. The calculated and measured alignment uncertainties are consistent with less than 3 mu rad of tilt uncertainty and 1.5 mu m of centration uncertainty (1 sigma). (C) 2013 Society of Photo-Optical Instrumentation Engineers (SPIE)