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Abbe number of glass for thermal infrared

  • April 11, 2025
  • 1 reply
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Hello,
I have a question about a glass for the thermal infrared region, specifically IRG26 glass, present in the SCHOTT_IRG catalog.
The Tolerance Wizard is not able to insert the tolerance on the Abbe number of this glass. Why? If the Abbe number is not clearly defined, can we trust the raytrace and therefore the evaluation of the chromatic aberrations?

Thanks!

 

Best answer by Sean Turner

Abbe number is just a reference value in OpticStudio, so it has no impact on index of refraction calculation or ray tracing. The Abbe number of a glass is specified at d-light in Zemax OpticStudio (587.6 nm).

F, d, C are all wavelengths below the minimum wavelength for IRG glasses, so this value cannot be defined by OpticStudio. This is why it can’t be used in tolerancing. 

If you want to define your own shifted Abbe number, choose a center, short, and long wavelength for your design band. Then calculate your value using this equation. While it may not help you with tolerancing, it could give you a better idea for which glasses could improve your design.

 

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Sean Turner
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  • April 11, 2025

Abbe number is just a reference value in OpticStudio, so it has no impact on index of refraction calculation or ray tracing. The Abbe number of a glass is specified at d-light in Zemax OpticStudio (587.6 nm).

F, d, C are all wavelengths below the minimum wavelength for IRG glasses, so this value cannot be defined by OpticStudio. This is why it can’t be used in tolerancing. 

If you want to define your own shifted Abbe number, choose a center, short, and long wavelength for your design band. Then calculate your value using this equation. While it may not help you with tolerancing, it could give you a better idea for which glasses could improve your design.

 


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