V-Block Refractometer

The most common identifying features for characterizing an optical glass are the refractive index nd in the visible spectrum’s mid-range and the Abbe number νd = (nd - 1)/(nF - nC) as a measure for dispersion. The difference nF - nC is referred to as the principal dispersion.

To economically determine the refractive index and dispersion of small test samples, the V-block refractometer is recommended with up to ± 2 · 10–5 accuracy in the refractive index and ± 1 · 10–5 in the dispersion. Due to a high degree of automation, up to 10 samples of various sizes can be combined in a V-block stack and measured during a single measurement sequence.

For the best possible determination of the refractive index and dispersion, up to 11 spectral lines between 365 nm and 1014 nm are used. Tolerances for the refractive index and dispersion for standard delivery quality are nd ± 5 · 10–4 and νd ± 0.5 %.

On request, materials with narrower tolerances can be provided. Selected glass can be provided with tolerances nd ± 1 · 10–4 and νd ± 0.1 %. For all deliveries of fine annealed optical glass, standard test reports according to ISO 10474 are provided.

On request, test certificates with even greater accuracy (nd ± 2 · 10–5 and νd ± 1 · 10–5) can be provided for individual glass parts.

These certificates also list the constants of the Sellmeier dispersion formula for the applicable spectral range.