Adaptive Phase Correction for Phase Measuring Deflectometry Based on Light Field Modulation

The phase measuring deflectometry is a powerful measuring method for complex optical surfaces, which captures the reflected fringe images associated with a displaying screen and calculates the normal vectors of the surface under test (SUT) accordingly. The captured images are usually set conjugate to the SUT, which in turn makes the screen defocused. As a result, the blurring effect caused by the point spread function (PSF) of the off-axis catadioptric imaging system can bias the solved phases. In order to correct the phase errors, a light field is constructed based on the Fourier compressive sensing method to describe the light transmission between the screen and camera pixels. Fringe modulation is conducted to enhance the robustness against noise, and then, space-variant PSFs can be extracted from the light field. The true phases are obtained by solving a Wiener deconvolution problem, with the merit function adaptively regularized by adjusting the damping parameter. The proposed method can correct adaptively the phase errors induced by the complex aberrations. Compared to the reference measurements, the form accuracy can be improved by four times.