Testing an aspheric mirror based on phase measuring deflectometry

A method based on basic phase measuring deflectometry is proposed for testing the aspherical mirror. The method uses a reference screen in two different distances from the mirror under test. The sinu- soidal, intensity-modulated patterns generated by the computer are dis- played on the LCD screen, and the camera observes the patterns re- flected off the testing mirror. The observed pattern appears distorted depending on the shape of the mirror. Using the phase-shifting tech- nique, the original ray of every image point and its corresponding de- flected ray can be constructed. Their intersection points and the surface normal are obtained. Then the mirror surface is reconstructed with high accuracy by numerically integrating the surface normals. The proposed method is robust against noise and can test the mirror full field. In this work, the method is introduced, and computer simulation and experi- mental results are shown. © 2009 Society of Photo-Optical Instrumentation