A glancing incidence interferometric test for large x-ray mirror mandrels, using two computer generated holograms (CGH s), is described. The two CGH s are used to form a double pass glancing incidence system. One layout of the CGH-cavity glancing incidence interferometer is studied and factors relating to its first order design are analyzed. A semi-analytical expression for the phase function is derived which avoids high-order ripple errors and improves the efficiency of the CGH pattern generation. A system of coarse and fine fiducials for the alignment of both CGHs and the tested mandrel is discussed. Compared with the traditional methods such as coordinate measuring machines (CMM s) or other scanning metrology systems, the CGH-cavity glancing incidence interferometric test can measure a mandrel surface without mechanical contact, at a high sampling spatial frequency sampling, lower uncertainty, and high speed.
Citation: Optical Engineering
Pub Type: Journals
CGH, mandrel, x-ray optics, optical testing, interferometry