SPIE Proceedings [SPIE 4th International Symposium on Advanced Optical Manufacturing and testing technologies: Optical Test and Measurement Technology and Equipment - Chengdu, China (Wednesday 19 November 2008)] 4th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment - Quantitative measurement of Φ140mm F/2 parabolic surface with Ronchi grating test method