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Proceedings Paper

Dispersion formula for the thermo-optic coefficient of optical glasses
Author(s): Hans J. Hoffmann; Werner W. Jochs; Gerhard Westenberger
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Paper Abstract

The refractive index n is known to vary with the temperature. Thus the optical path length and the focusing properties of transmissive optical elements may change with the ambient temperature T. Since there was no reliable dispersion formula of the temperature coefficient dn/dT the manufacturers of optical glasses published data on dn/dT averaged over certain intervals ( +i). These data are available for a small number of discrete wavelengths )k only. To calculate numerically n as a function of T for wavelengths other than ZAk one has to inter polate and to integrate over different intervals of T with the respective average data of dn/dT. In order to avoid this awkward procedure and to reduce the necessary data used for numerical calculations a dispersion formula for dn/dT is developed on the basis of a simple model. This formula has been tested and applied successfully to experimental data of dn/dT both as a function of wavelength ) and of temperature T for more than 140 different opti cal glasses in the visible spectral region and in the range of 400C T 800C. For 22 glasses data are available also for an extended range of temperature _1000C T 1400C. Even in this case the dispersion formula can be applied successfully. Moreover this formula can be integrated easily as a function of T to give immediately the increment of the refrac

Paper Details

Date Published: 1 October 1990
PDF: 12 pages
Proc. SPIE 1327, Properties and Characteristics of Optical Glass II, (1 October 1990); doi: 10.1117/12.22537
Show Author Affiliations
Hans J. Hoffmann, Schott Glaswerke (Germany)
Werner W. Jochs, Schott Glaswerke (Germany)
Gerhard Westenberger, Schott Glaswerke (Germany)


Published in SPIE Proceedings Vol. 1327:
Properties and Characteristics of Optical Glass II
Alexander J. Marker, Editor(s)

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