ISO 6760-2:2024 PDF

Overview

ISO 6760-2:2024 - "Optics and photonics - Test method for temperature coefficient of refractive index of optical glasses - Part 2: Interferometric method" specifies an interferometric test method to determine how the refractive index of optical glass changes with temperature. Using interferometry (typically a Fizeau setup), the method measures changes in optical path length as temperature is varied continuously. The standard targets measurements across the wavelength range 365 nm to 1 014 nm with an intended accuracy of 1 × 10‑6 K‑1 for the temperature coefficient of refractive index.

Key topics and requirements

• Measurement principle: Count cycles of light/dark fringe changes in an interferometer to quantify optical path length change and derive the temperature coefficient of refractive index.
• Intended ranges: Wavelengths 365–1 014 nm; arbitrary temperature range (as defined by test setup).
• Accuracy and resolution: Intended accuracy within 1 × 10‑6 K‑1; interferometer fringe-count resolution of 0.1 cycle (1/10 cycle) or better.
• Thermal chamber: Must control specimen temperature (±0.5 K stability) and include a thermometer accurate to ±0.2 K; options to use dry air at 0% RH or vacuum (residual pressure