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Proceedings Paper

Development of optical surface-profiling instrumentation
Author(s): Yao Lin; Peter Z. Takacs; Thomas Tsang; Karen Furenlid; Runwen Wang
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Paper Abstract

A novel non-contact optical profiler described in this paper is designed and made for measuring the surface characteristics of optical parts. Measurements are based on a combination of an optical heterodyne technique and a precise phase measurement procedure without the need of a reference surface. A Zeeman-split He-Ne laser is employed as the light source which offers two common-path polarized beams. The frequency difference between the beams is 1.8 MHz. A special optical head is designed and fashioned as a beam splitter which contains a birefringent lens and an objective. The whole optical system is completely common- path. This allows the optical common-mode rejection technique to be applied in the system for minimizing the environmental effects in measurements such as air turbulence, vibrations and temperature variations. To keep the sample surface focused on the ordinary rays in the optical head, an astigmatic autofocus system is employed. A stepping micro-stepping system can move the optical head in the range of 25 mm with 0.1 micrometers resolution. A data acquisition system is made to control the auto-focus system, data receiving and analyses. This makes the measurement automatically while the sample is being scanned. The characteristics of the surface can be displayed on the computer screen. The theoretical and experimental analyses of the profiler are completed. The profiler measures samples with 1.1 angstroms height accuracy and 4 micrometers lateral resolution when a 40X objective is used in the optical head. The accuracy comparisons of the profiler with different objectives 5X, 10X, 20X, and 40X are shown in good agreement. The advantages of the present profiler are presented. Based on the autofocus system, the profiler optical system will be designed to mount on a large linear air-bearing slide, so that it is capable of scanning over a distance covering from 4 micrometers to 1 m.

Paper Details

Date Published: 15 December 1992
PDF: 9 pages
Proc. SPIE 1776, Interferometry: Surface Characterization and Testing, (15 December 1992); doi: 10.1117/12.139242
Show Author Affiliations
Yao Lin, Brookhaven National Lab. (United States)
Peter Z. Takacs, Brookhaven National Lab. (United States)
Thomas Tsang, Brookhaven National Lab. (United States)
Karen Furenlid, Brookhaven National Lab. (United States)
Runwen Wang, Shanghai Institute of Optics and Fine Mechanics (China)

Published in SPIE Proceedings Vol. 1776:
Interferometry: Surface Characterization and Testing
Katherine Creath; John E. Greivenkamp, Editor(s)

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