Wavefront reconstruction method using the intensity image of phase-shift grating

An improved Hartmann test for wavefront reconstruction and spot diagram building with high spatial resolution is presented, which uses geometrical optics and ray tracing method based on the phase information of phase-shift grating. To improve accuracy and spatial resolution the fringe analysis is used. A liquid-crystal display (LCD) is used as a grating and a phase-shifting device. The sinusoidal grating generated by the computer was displayed on the LCD and illuminated to generate the fringe beam. The fringe beam transmits the lens being tested and the image of the phase-shift grating is projected on a screen. A CCD camera detects the intensity distribution of the images and the fringes become deformed carrying the information of wavefront. The deformed phase distribution can be tested accurately by the phase-shifting technique and then is used for ray tracing. The spot diagram is obtained from the phase distribution contour lines. And the wavefront can be reconstructed because that the light travels in direction normal to the wavefront. In this paper, the method is presented, and the experimental results are shown. (C) 2009 Elsevier Ltd. All rights reserved.