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Proceedings Paper

Research and analysis on new test lenses for calibration of focimeters used for measuring contact lenses
Author(s): Jiyan Zhang; Liru Wang; Zhenya Ma
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Paper Abstract

A focimeter is one of the basic ophthalmic instruments used in every optometric practice, and verification of the accuracy and calibration of the instrument are of the utmost importance. For many years the International Standardization for Organization requires that calibrations for all kinds of focimeters shall be accomplished by using test lenses described in ISO 9342:1996. These test lenses must be of high quality and of nominal back vertex power that is known with high accuracy. With the development of science and technology, ISO 9342 was revised in 2005. A new part ISO 9342-2 had been drafted for test lenses used to calibrate focimeters with contact lens measurement, and the original ISO 9342 was turned into the current ISO 9342-1, which could only be used to calibrate fociemters with spectacle lens measurement. As one of the standard drafters, the background for the newly published ISO 9342-2 is introduced in this study, and comparison between test lenses of ISO 9342-1 and ISO 9342-2 is made. Further, the influence of tolerance and uncertainty in design and production of standard test lenses of ISO 9342-2 is analyzed. The paraxial approximation is used to relate the lens parameters with back vertex power and to calculate the uncertainty budget. Moreover, one set of test lenses conforming to ISO 9342-2 is manufactured and experiments are done with it. Results show that test lenses described in ISO 9342-2 can correct the measurement errors of focimeters used for measuring contact lenses well, especially for spherical aberration, and the correction is more effective for spherical contact lenses with high back vertex power.

Paper Details

Date Published: 24 October 2006
PDF: 6 pages
Proc. SPIE 6357, Sixth International Symposium on Instrumentation and Control Technology: Signal Analysis, Measurement Theory, Photo-Electronic Technology, and Artificial Intelligence, 635722 (24 October 2006); doi: 10.1117/12.717110
Show Author Affiliations
Jiyan Zhang, Beijing Institute of Technology (China)
National Institute of Metrology (China)
Liru Wang, National Institute of Metrology (China)
Zhenya Ma, National Institute of Metrology (China)


Published in SPIE Proceedings Vol. 6357:
Sixth International Symposium on Instrumentation and Control Technology: Signal Analysis, Measurement Theory, Photo-Electronic Technology, and Artificial Intelligence
Jiancheng Fang; Zhongyu Wang, Editor(s)

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