In-situ measurement of aspherics with sub-aperture deflectometry for precision optical manufacturing

The measurement of aspheric optics has attracted intensive attention in precision engineering, and efficient in-situ measurement technologies are required urgently. Phase measuring deflectometry is a powerful measuring method for complex specular surfaces. In this paper, an in-situ measurement method is developed based on the sub-aperture deflectometry. A complete measuring procedure is developed, including initial calibration, self-adaptive calibration, route planning, imaging acquisition, phase retrieval, gradient calculation, surface reconstruction and sub-aperture stitching. Several key points concerning the sub-aperture measurement are investigated, and effective solutions are proposed to balance the measuring accuracy and aperture, to overcome the height/slope ambiguity and to eliminate the stitching errors caused by point sampling and measuring errors. The measuring flexibility and stability can be greatly improved compared to the existing SCOTS measuring approach.