In order to achieve high-accuracy measurement of radius of curvature of optical sphere, ultra-high accuracy radius of curvature testing device is developed by dual-frequency laser interferometer and Fizeau interferometer based on cat’s eye and confocal method. Through analyzing the error source models of radius of curvature testing, optical configuration of the testing device has been optimized. Precise environment control and real-time monitoring system is also established to reduce the errors caused by environment. Through the above processes, the radius of curvature measurement relative accuracy is better than 2 ppm. One optical sphere, R88.5 mm, test aperture 59 mm, has been tested. Testing result is 88499.465 ± 0.176 μm, meeting the design requirement. The method has high accuracy and practical advantages.
References
[1]
Seitz, G., Schulte, S., Dinger, U., et al. (2004) EUV-Microlithography—A Challenge for Optical Metrology. SPIE, 5533, 20-26. http://dx.doi.org/10.1117/12.556317
[2]
Takigawa, Y., Nakayama, S., Yamamoto, T., et al. (2005) Absolute Accu-racy Evaluation of a Spherical Null Testing for EUVL Mirrors. SPIE, 5869, 58690Q-1-58690Q-11.
[3]
Peng, S.J. and Miao, E.L. (2014) Sub-Micron Precision Measurement of Radius of Curvature and Uncertainties Analysis. Acta Optical Sinica, 34, 0512001-1-0512001-8. (In Chinese)
[4]
Chen, L. (2005) The Research of Single Frequency Laser Interference for Spherical Radius of Curvature Measurement. Nanjing University of Science and Technology, Nanjing. (In Chinese)
[5]
Schmitz, T.L., Davies, A.D. and Evans, C.J. (2001) Uncertainties in Interferometric Measurements of Radius of Curvature. SPIE, 4451, 432-447.
[6]
Sun, R.D., Qiu, L.R., Yang, J.M., et al. (2011) Development of Laser Differential Confocal Radius Measurement System. Chinese Journal of Scientific Instrument, 32, 2833-2838. (In Chinese)
[7]
Tian, Z.H., Shi, Z.G., Liu, W.Q., et al. (2013) High-Accuracy Measurement for Radius of Curvature and Its Uncertainties. Optics and Precision Engineering, 21, 2495-2501. (In Chinese) http://dx.doi.org/10.3788/OPE.20132110.2495
[8]
Sha, D.G. (2003) Analysis of Measurement Error and Evaluation of Measurement Uncertainties. Chinese Metrology Press, Beijing. (In Chinese)
[9]
Bobroff, N. (1993) Recent Advances in Displacement Measuring Interferometry. Measurement Science and Technology, 4, 907-926. http://dx.doi.org/10.1088/0957-0233/4/9/001
