Refractive optics metrology using on-axis deflectometry system

This on-axis deflectometry design utilizes a pattern on a liquid crystal display reflected by a parabolic mirror into a CMOS camera at the mirror's focal point. An initial image is taken in this null configuration and then a second image is taken when a test lens is placed between the mirror and camera. These differences in the two images are used to determine the lower order spatial frequency information about the test sample’s through wavefront error (WFE). The reconstructed WFE maps from the system measurements are compared to the reconstructed WFE maps of the same test sample using a Zygo Verifire interferometer. The placement of the camera at the focal length of the parabolic mirror creates collimated light conditions between the parabolic mirror and the monitor. This removes the local slope calculation dependency on the axial position of the monitor and reduces height-slope ambiguities found in traditional deflectometry systems.