ISO 12123:2018

Overview

ISO 12123:2018 - Optics and photonics - Specification of raw optical glass - provides standardized rules and guidance for specifying raw optical glass (strip, pressings, castings) used to manufacture finished optical elements. It complements the ISO 10110 series (finished-element specifications) by addressing the different shapes, sizes and tolerancing needs of raw glass. The 2018 (third) edition introduces definitions, grade designations and reference data to improve communication between glass suppliers and optical element manufacturers.

Key topics and technical requirements

• Principal refractive index (nd / ne): How to specify the reference refractive index of glass and the environmental reference (typically 20 °C and 1013 hPa).
• Refractive index variation: Tolerancing across delivery lots vs. within a single piece (optical homogeneity).
• Abbe number (vd / ve): Standardized measure of glass dispersion for chromatic performance.
• Spectral internal transmittance & UV cut-off / colour code: Ways to describe bulk transmission, the UV transmission edge and its slope.
• Optical homogeneity: Peak‑to‑valley refractive index span (important to specify the intended usable aperture to avoid over‑specification).
• Striae, bubbles and inclusions: Short‑range refractive index variations and material contiguity descriptors and inspection directions.
• Stress birefringence: Polarization homogeneity tolerances and measurement considerations.
• Partial and relative partial dispersion / deviation from normal line: Definitions, normal-line reference curves (standard crown and flint), and ΔP calculation to evaluate suitability for higher-order colour‑aberration correction across 365 nm–1014 nm (dispersion data referenced to 20 °C; method provided for other temperatures).
• Tolerance grades and ordering indications: Grade abbreviations for main properties and recommended information to include when ordering raw glass (examples and guidance in Clause 6 and Annex A).

Practical applications and who uses this standard

ISO 12123:2018 is used by:

• Glass manufacturers and suppliers - to publish consistent material data and tolerance grades.
• Optical designers and lens manufacturers - to translate element requirements into realistic raw‑glass specs (see Annex A for guidance).
• Procurement and QA teams - to write purchase orders, check certificates and avoid costly over‑specification.
• Metrology and test labs - for standardized measurement definitions (refractive index, homogeneity, transmittance, birefringence).

Note: For specific application domains (e.g., lasers, infrared systems) this standard forms a basis but may require supplementary specifications.

Related standards

• ISO 10110 series - specifications and notations for finished optical elements.
• ISO 7944, ISO 1 and other referenced measurement standards for environmental conditions and refractive index practice (see document for details).

Keywords: ISO 12123:2018, specification of raw optical glass, refractive index, Abbe number, optical homogeneity, partial dispersion, raw optical glass specification.