2/ Inhomogeneity and striae

Code 2/ limits refractive-index inhomogeneity and striae in the glass. Homogeneity comes first, then striae, separated by a semicolon.

Standard: ISO 10110-18:2018

Decode a callout →Use it in a drawing →Build a 2/ callout

Syntax

2/A;B	A = homogeneity class, B = striae class.
2/A−F;B	Optional −F after A: the focus term (Zernike Z(2,0)) may be removed.
02/ · 12/	Raw material · finished assembly.

Worked examples

2/ 1;3	Homogeneity class 1 (Δn ≤ 40 × 10⁻⁶ PV), striae class 3 (striae ≥ 30 nm OPD in ≤ 2 % of the area).
2/ 3;4	Class 3 (Δn ≤ 4 × 10⁻⁶), striae class 4 (≤ 1 % of the area).
2/ 0;1	Loosest common requirement: NH100, striae class 1.

Click an example to open it in the decoder.

Common values and typical grades

Class 0 / NH100	Δn ≤ 100 × 10⁻⁶ (PV)
Class 1 / NH040	Δn ≤ 40 × 10⁻⁶
Class 2 / NH010	Δn ≤ 10 × 10⁻⁶
Class 3 / NH004	Δn ≤ 4 × 10⁻⁶
Class 4 / NH002	Δn ≤ 2 × 10⁻⁶
Class 5 / NH001	Δn ≤ 1 × 10⁻⁶
Striae classes 1–4	area fraction with striae ≥ 30 nm OPD ≤ 10 %, 5 %, 2 %, 1 %
Striae class 5	extremely low striae, details in a note

Striae classes 1–5 are the legacy classes, still accepted for backward compatibility. ISO 10110-18 also defines new striae class indicators verify.

Common mistakes

Swapping the order. Homogeneity comes first: 2/ 1;3 is homogeneity 1, striae 3.
Writing a comma instead of the semicolon between the two classes.
Asking for class 4 or 5 homogeneity on a small lens where it does not affect performance; it limits glass choice and raises cost.

Questions

What does 2/ 1;3 mean?

Homogeneity class 1 (NH040, index variation ≤ 40 × 10⁻⁶ peak-to-valley) and striae class 3 (striae of 30 nm OPD or more in no more than 2 % of the area).

What is NH040?

The ISO 10110-18 name for homogeneity class 1: maximum peak-to-valley refractive index variation of 40 × 10⁻⁶.

Sources

ISO 10110-18:2018 (homogeneity and striae; replaces ISO 10110-4); glass maker technical notes. Full list and edition status: Sources & editions.

An unofficial summary written from public previews of the standards and reputable secondary sources. It does not reproduce the ISO text. Items marked verify could not be fully confirmed. Check against the current edition; see Sources & editions.