High-Precision Aspheric Surface Measurement Using Scanning Deflectometry: Three-Dimensional Error Analysis and Experiments

Abstract

Interferometers are widely used to measure large aspheric surfaces because of their high accuracy and high efficiency. However, they cannot be used for aspheric surfaces with large curvature and asphericity. In this paper, we propose a method for measuring aspheric surfaces using scanning deflectometry with an autocollimator. A rotary stage is used to enlarge the measurement range of the autocollimator, so that aspheric surfaces with large slope changes can be measured. Three-dimensional error analysis is performed. We use an autocollimator with a measurement range of 21500 μrad (4500 arcsec) to measure a spherical surface with a curvature radius of 400 mm to perform the experiment. Experimental results showed that the average root-mean-square error was approximately 100 nm.