A method for testing fast aspheric convex surfaces with dynamic null screens using LCD's is shown. At the present method a flat null screen displayed on a LCD monitor is proposed; the position of the spots on the LCD can be changed in a dynamic way, for doing the point shifting of the image spots. As it was shown before, this reduces the truncation error during the integration procedure improving in this way the sensitivity of the test. The dimensions of the LCD give the test area on the surface. The positioning accuracy for the screen spots is related to the LCD spatial resolution. Results of the evaluation of a parabolic convex surface with F/#=0.22 are shown.
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