Overview
ISO 8237:2024 - Optics and photonics - Specification of chalcogenide glass used in the infrared spectrum - defines chalcogenide glass from a chemical perspective and specifies how to measure, report and classify basic optical properties for IR use. The standard covers the spectral range 0.78 µm to 25 µm, and is intended to standardize characterization and reporting so manufacturers, designers and test laboratories can communicate reliably about IR optical materials.
Key topics and technical requirements
- Definition of chalcogenide glass: chemical definition (glass comprising at least one non-oxygen chalcogen: S, Se or Te) and naming conventions (sulfide, selenide, telluride).
- Spectral transmittance: measured at 20 °C; standard sample thicknesses (2 ± 0.1) mm, (5 ± 0.1) mm, (10 ± 0.2) mm. Spectral regular transmittance (τr) is to be reported as graphs with uncertainty (error bars or statements). Measurement method: ISO 15368.
- Internal vs. regular transmittance: definitions and relationship for reporting internal losses excluding surface reflections.
- Refractive index (nλ): measured at 20 °C in air, reported as tables or dispersion formulae (e.g., Sellmeier). Measurement method: ISO 17328. Recommended reference wavelengths include 4.00 µm or 10.00 µm when applicable.
- Temperature dependence (Δn/ΔT): recommended measurement and reporting per ISO 6760-1.
- Relative partial dispersion (Pn): formal definition and ordering of wavelengths for partial dispersion reporting.
- Tolerances and quality classes: defined classes for refractive index variation (NP grades with numeric limits), optical homogeneity (NH grades with numeric dn limits), and striae (IRSW grades with wavefront deviation limits, e.g. IRSW 05 ≤ 0.5 λ, IRSW 02 ≤ 0.2 λ, IRSW 007 ≤ 0.07 λ). Guidance on bubbles, inclusions and homogeneity testing is included.
Applications
ISO 8237 is directly applicable to the specification, procurement and quality control of IR optics made from chalcogenide glass, including:
- IR imaging and thermal camera lenses
- Windows and filters for spectroscopy and sensing
- Optical components used as alternatives to germanium, silicon or zinc selenide in mid-IR systems
- Manufacturing quality control and materials data sheets for optical suppliers
Who should use this standard
- Optical material manufacturers and suppliers (to specify and publish material data)
- Lens and system designers (to select materials with predictable refractive index, dispersion and transmittance)
- Metrology and test laboratories (for consistent measurement and reporting)
- Procurement and quality assurance teams in photonics, defense, aerospace and industrial sensing
Related standards
Keywords: ISO 8237, chalcogenide glass, infrared optics, IR transmittance, refractive index, optical homogeneity, striae, mid-IR materials.