The phase measuring deflectometry is a powerful technique for the in-situ measurement of of complex optics. Its measurement accuracy is comparable with conventional interferometry, but with higher flexibility, stability and efficiency. The three main challenges in the deflectometric measurement, namely the position-angle uncertainty in calculating the pixel correspondences, height-slope ambiguity in specifying the normal vectors, and rank deficiency in surface reconstruction are analyzed. Some significant error factors and effective solutions are introduced. The measuring accuracy of complex surfaces can achieve a level of 100 nm RMS.
Deflectometry is a powerful measuring technique of complex optical surfaces. Usually a series of binary patterns or sinusoidal fringes are displayed on a screen, and correspondences are established between the screen and camera points according to their gray levels or phases. The image associated with a screen pixel is blurred due to the defocus and aberrations of the off-axis imaging system, and the calculated location of the correspondence point will in turn be biased. The space variant point spread function associated with the catadioptric system is analyzed based on the light field method, and the resulting blurring effect is then addressed using Wiener deconvolution algorithm. Henceforth the phase errors in the captured images can be compensated effectively. Experimental results are presented to demonstrate the feasibility and effectiveness of the proposed method.
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