Transparent Element Surface Measurement Using Binary Pattern in Phase-Measuring Deflectometry

For on-line surface measurement of transparent optical elements, phase measuring deflectometry (PMD) is a very promising method. However, the parasitic reflection from the rear surface is an existing problem for PMD to measure transparent element. A parasitic reflection eliminating method using binary pattern is proposed, the principle of which is described in detail. And the proposed method is implemented on a transparent window glass with a thickness of about 10mm. The surface shape result shows a good agreement with the interferometer data with a sub-wavelength level accuracy.