Proceedings of the
9th International Conference of Asian Society for Precision Engineering and Nanotechnology (ASPEN2022)
15 – 18 November 2022, Singapore
doi:10.3850/978-981-18-6021-8_OR-11-0246
Radial Shearing Interferometer for Reconstruction of Wavefront by Fringe Modeling
1Department of Mechanical System Design Engineering, Seoul National University of Science and Technology, 232 Gongneung-ro, Nowon-gu, Seoul, 01811, Korea
2 School of Mechanical Engineering, Hanoi University of Science and Technology, 01 Dai Co Viet Road, Ha Noi, Viet Nam
ABSTRACT
A perfect aspherical lens design significantly enhances the performance of an imaging system. However, the trend of device miniaturization makes this surface measurement becomes a challenge. In this study, a novel waviness profile metrology method for an aspheric surface is proposed by fringe modeling of a radial shearing interferometer (RSI) to reconstruct a wavefront. An RSI experiment is conducted with a small shearing amount to minimize the asphericity and a dynamic interferometer using a polarizing camera is combined to obtain the wavefront by the phase-shifting technique. Fringe modeling of the interferometer is realized by Ray-tracing software and the wavefront is extracted to compare with the respective wavefront in the experiment. The parameters of modeling are optimized iteratively with a good wavefront agreement between modeling and experiment to obtain a testing surface. The waviness surface profile expects to achieve the nanometer scale and this potential method is powerful for applying to surface metrology as a new measurement standard.
Keywords: Radial shearing interferometer, Fringe modeling, Waviness surface profile
1Department of Mechanical System Design Engineering, Seoul National University of Science and Technology, 232 Gongneung-ro, Nowon-gu, Seoul, 01811, Korea
2 School of Mechanical Engineering, Hanoi University of Science and Technology, 01 Dai Co Viet Road, Ha Noi, Viet Nam
ABSTRACT
A perfect aspherical lens design significantly enhances the performance of an imaging system. However, the trend of device miniaturization makes this surface measurement becomes a challenge. In this study, a novel waviness profile metrology method for an aspheric surface is proposed by fringe modeling of a radial shearing interferometer (RSI) to reconstruct a wavefront. An RSI experiment is conducted with a small shearing amount to minimize the asphericity and a dynamic interferometer using a polarizing camera is combined to obtain the wavefront by the phase-shifting technique. Fringe modeling of the interferometer is realized by Ray-tracing software and the wavefront is extracted to compare with the respective wavefront in the experiment. The parameters of modeling are optimized iteratively with a good wavefront agreement between modeling and experiment to obtain a testing surface. The waviness surface profile expects to achieve the nanometer scale and this potential method is powerful for applying to surface metrology as a new measurement standard.
Keywords: Radial shearing interferometer, Fringe modeling, Waviness surface profile