Small Pitch Tool for Removing Middle Spatial Frequency Errors

Abstract:

More and more optical elements are needed in modern industry, which is reflected by both the bigger amount of requirement, and more complicated designed surface such as asphere and even free form surface. As a result, optical polishing using small tools on CNC machines is applied widely in the whole world, which has a lot of advantages such as fast speed, high accuracy, high flexibility and so on. But the small tool polishing can also cause in some problems. For example, the middle spatial frequency errors (MSFE) may be increased during the polishing. The reasons may consist of the following aspects: 1) the positional error of the workpiece; 2) the mistake of error data input; 3) the unexpected stop of the polishing process; 4) the stabilization of the slurry density during the process; 5) the temperature change of the contact area between the tool and the workpiece and so on. As is known, pitch is usually used in traditional optical manufacture, and it can reduce the middle and high spatial frequency errors in a large extent because of the different removal rate between the high points and low points on the optical surface. Therefore, the application of the combination of pitch and small tool is described in this paper in order to solve the MSFE problem, and we have got good polishing results of reducing the error from 2.155nm to 0.267nm by using the new pitch tool on the CNC machine after two runs.

• Periodical: Key Engineering Materials (Volume 552)
• Pages: 137-141
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.552.137
• Online since: May 2013
• Authors: Gao Wen Wang
• Keywords: Middle Spatial Frequency Errors, Pitch, Small Tool Polishing

References

[1] X. Zhang. Computer simulation and technology experiment for CCOS [J]. Opt. Precision Eng., 1993, 1(5):64-68.

[2] J. Yu, X. Zhang, X. Sun, et al.. On the technology computer controlled optical surfacing. Optical Technology, 1998, 5(3):6-8.

[3] D. M. Aikens, C. R. Wolfe, and J. K. Lawson. The use of Power Spectral Density (PSD) functions in specifying optics for the National Ignition Facility [C]. SPIE, 1995, 2576: 281-292.

DOI: 10.1117/12.215604

[4] X. Zhou, S. Li, Y. Dai, et al.. Correcting errors in definite area: a new method for controlling mid-spatial-frequency errors in optical surface [J]. Opt. Precision Eng., 2007, 15(11):1668-1673.

[5] Y. Han, F. Wu, Y. Wan et al.. Research on mid-frequency errors smoothing with a passive semi-rigid lap [J]. High Power Laser and Particle Beams, 2010, 22(2): 319-322.

DOI: 10.3788/hplpb20102202.0319

[6] P. K. Mehta, P. B. Reid. A mathematical model for optical smoothing prediction of high-spatial frequency surface errors [C]. SPIE, 1999, 3786:447-459.

[7] T. T. Michael, H. B. James, B. Anderson. Aspheric optics: smoothing the ripples with semi-flexible tools [J]. Opt. Eng., 2002, 41(7): 1473-1474.

DOI: 10.1117/1.1481898

[8] R. A. Jones. Computer simulation of smoothing during computer controlled optical polishing [J]. Appl. Opt., 1995, 34(7): 1162-1169.

DOI: 10.1364/ao.34.001162

[9] F. W. Preston. The theory and design of plate glass polishing machines [J]. J. Soc. Glass Technology, Vol. 11 (1927).