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Proceedings Paper

Experimental research on radius of curvature measurement of spherical lenses based on laser differential confocal technique
Author(s): Xiang Ding; Ruoduan Sun; Fei Li; Weiqian Zhao; Wenli Liu
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Paper Abstract

A new approach based on laser differential confocal technique is potential to achieve high accuracy in radius of curvature (ROC) measurement. It utilizes two digital microscopes with virtual pinholes on the CCD detectors to precisely locate the cat's-eye and the confocal positions, which can enhance the focus-identification resolution. An instrumental system was established and experimental research was carried out to determine how error sources contribute to the uncertainty of ROC measurement, such as optical axis misalignment, dead path of the interferometer, surface figure error of tested lenses and temperature fluctuation, etc. Suggestions were also proposed on how these factors could be avoided or suppressed. The system performance was tested by employing four pairs of template lenses with a serial of ROC values. The relative expanded uncertainty was analyzed and calculated based on theoretical analysis and experimental determination, which was smaller than 2x10-5 (k=2). The results were supported by comparison measurement between the differential confocal radius measurement (DCRM) system and an ultra-high accuracy three-dimensional profilometer, showing good consistency. It demonstrated that the DCRM system was capable of high-accuracy ROC measurement.

Paper Details

Date Published: 30 November 2011
PDF: 11 pages
Proc. SPIE 8201, 2011 International Conference on Optical Instruments and Technology: Optoelectronic Measurement Technology and Systems, 82011W (30 November 2011); doi: 10.1117/12.906384
Show Author Affiliations
Xiang Ding, National Institute of Metrology (China)
Ruoduan Sun, Beijing Institute of Technology (China)
Fei Li, National Institute of Metrology (China)
Weiqian Zhao, Beijing Institute of Technology (China)
Wenli Liu, National Institute of Metrology (China)

Published in SPIE Proceedings Vol. 8201:
2011 International Conference on Optical Instruments and Technology: Optoelectronic Measurement Technology and Systems
Xinyong Dong; Xiaoyi Bao; Perry Ping Shum; Tiegen Liu, Editor(s)

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