ISO 6760-1-2025 PDF

Full title and description

Optics and photonics — Test method for temperature coefficient of refractive index of optical glasses — Part 1: Minimum deviation method. This International Standard specifies a measurement method that determines the temperature coefficient of refractive index of optical glass by measuring refractive index change with temperature using the minimum-deviation prism technique.

Abstract

This document defines the procedure to calculate the temperature coefficient of refractive index (dn/dT) by measuring refractive index versus temperature using the minimum-deviation method. The method is intended for measurements in the temperature range −40 °C to +80 °C and the wavelength range 365 nm to 1 014 nm, with an intended accuracy on the order of 1×10⁻⁶ K⁻¹.

General information

• Status: Published.
• Publication date: July 14, 2025 (Edition 2, 2025-07).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 37.020 (Optics and photonics).
• Edition / version: Edition 2 (2025).
• Number of pages: 24.

Scope

This part of ISO 6760 specifies a laboratory test method based on the minimum-deviation prism technique to measure how the refractive index of optical glass varies with temperature and to derive the temperature coefficient of refractive index. It covers specimen preparation, measurement wavelengths (365 nm to 1 014 nm), applicable temperature range (−40 °C to +80 °C), measurement procedure, uncertainty assessment and reporting requirements for results intended to an accuracy of about 1×10⁻⁶ K⁻¹.

Key topics and requirements

• Measurement principle: minimum-deviation prism method for refractive index versus temperature.
• Intended temperature range: −40 °C to +80 °C and specified temperature control/stability requirements.
• Wavelength range: 365 nm to 1 014 nm (spectral selection and source requirements).
• Target measurement accuracy and uncertainty evaluation: on the order of 1×10⁻⁶ K⁻¹ with documented uncertainty analysis.
• Specimen preparation, geometry and optical quality requirements for prism samples.
• Calibration, instrument verification and traceability measures for angle, wavelength and temperature sensors.
• Required test-report content and result presentation (dn/dT values, test conditions, uncertainty budget).

(Key technical limits and intent summarized from the published standard.)

Typical use and users

Used by optical glass manufacturers, optical component producers, independent calibration and metrology laboratories, research institutions and quality assurance teams to characterise glass materials for lens design, optical system thermal modelling and component specification. The standard supports material data tables, design verification and inter‑laboratory comparison.

Related standards

ISO 6760 is a multipart series. Part 2 (ISO 6760-2:2024) specifies an interferometric method for measuring the temperature coefficient of refractive index and complements Part 1; both parts are maintained under ISO/TC 172/SC 3 (Optical materials and components). Other ISO/TC 172/SC 3 standards on optical materials and test methods may be relevant for broader material characterization.

Keywords

refractive index, temperature coefficient, dn/dT, optical glass, minimum deviation, prism method, interferometry, metrology, ISO 6760, optical materials.

FAQ

Q: What is this standard?

A: ISO 6760-1:2025 is an International Standard that specifies a laboratory test method (minimum-deviation prism technique) to determine the temperature coefficient of the refractive index of optical glasses.

Q: What does it cover?

A: It covers the measurement procedure, applicable temperature and wavelength ranges (−40 °C to +80 °C; 365 nm to 1 014 nm), accuracy targets (≈1×10⁻⁶ K⁻¹), specimen requirements, calibration and uncertainty reporting necessary to produce reliable dn/dT data.

Q: Who typically uses it?

A: Optical glass and component manufacturers, testing and calibration laboratories, research labs, optical designers and organisations that require traceable material data for thermal behaviour of optical systems use this standard.

Q: Is it current or superseded?

A: ISO 6760-1:2025 is the current published edition (Edition 2, published July 2025). The earlier 2024 edition was withdrawn and replaced by the 2025 publication.

Q: Is it part of a series?

A: Yes. ISO 6760 is a multipart standard. Part 1 covers the minimum-deviation method; Part 2 (ISO 6760-2:2024) covers an interferometric method for the same property. Both are under ISO/TC 172/SC 3.

Q: What are the key keywords?

A: Refractive index, temperature coefficient, dn/dT, optical glass, minimum deviation, interferometric method, prism, metrology, ISO 6760.