National Physical Laboratory

What is an NPL/HSE test slide and where can I obtain one? (FAQ - Length)

The HSE/NPL test slide was developed by the Health and Safety Laboratory (HSL) on behalf of the Health and Safety Executive (HSE) in collaboration with PTR Optics and the National Physical Laboratory. Its purpose is to provide a reproducible phase object to check microscope performance prior to counting asbestos fibre samples. The master engraving was produced by NPL using a ruling engine.

It consists of seven bands of twenty lines with widths ranging from 0.25µm to 1.1µm. The lines were produced using a V shaped inscriber with a depth to width ratio of approximately 1:10. The bands are separated by 20 mm gaps. A test zone is delineated by a rectangle bounded by deep grooves which can be viewed using a microscope with x100 magnification in either dark field or phase contrast mode.

Further information can be obtained from:

PTR Optics
Unit C6
Cross Green Garth
Leeds LS9 0SF, UK
Tel: 0113 249 6973
Fax: 0113 235 0420


Minerals and Fibres Section
Health & Safety Laboratory
Broad Lane
Sheffield S3 7HQ, UK
Tel: 0114 289 2000
Fax: 0114 289 2850

Last Updated: 1 Dec 2010
Created: 1 Dec 2010