3D Areal Calibration SpecimensOur 3D calibration specimens are manufactured exclusively by us for the UK National Physical Laboratories (NPL) and include 8 physical material measures (calibration artefacts). They allow users to calibrate the metrological characteristics of areal surface topography measuring instruments. These also enable the adoption of good measurement practice and prepare for the forthcoming ISO standards for determination of 3-D surface texture.

They include 2 areal star patterns (for testing resolution) and the following NPL calibrated samples – optical flat, 3 different pitch areal cross gratings, 5 step heights and 2 irregular samples.

The eight NPL areal calibration specimens and their physical material measures are shown in the table below.

Type Number Artefact Description
600 Flat Optical flat
601 Type ACG-2.1 μm height areal cross grating, with five different pitches –400 μm, 160 μm, 100 μm, 40 μm, 16 μm
602 Type ACG-1.2 μm height
603 Type ACG-0.5 μm height
604 Type ACG-0.03 μm height
610 Type AIR-B40 (40 nm autocorrelation length) areal irregular – characterised by a number of areal surface texture parameters and used as an overall check of the instrument performance
611 Type AIR-B70 (70 nm autocorrelation length)
615 Type ASG-0.2 (200 nm height) areal star pattern


Influence parameters and metrological characteristics

Influence parameters and metrological characteristics


The metrological characteristics of an areal surface texture instrument that will be defined in the forthcoming ISO standards for 3-D surface topography are shown in the table. The areal calibration artefacts have been designed to directly address each of the metrological characteristics.