Deflectometer with synthetically generated reference circle for aspheric surface testing

A deflectometer with a synthetically generated reference circle is proposed for aspheric surface testing. Rotation and translation movements are combined to realize laser scanning and make the measurement of the aspheric surface in polar coordinates. It effectively improves the measurement precision for aspheric surfaces with large relative aperture. The measuring equipment is calibrated using a defocused standard spherical surface, and it achieves a precision of λ/5-λ/10(λ=0.6328 μm), which is close to the precision of the interferometric method (λ/20). This testing technique based on laser deflectometry is capable of measuring most kinds of aspheric surfaces, especially those with large asphericity and those of concave shapes. The feasibility of the technique is shown and experimental results are presented.