Line scales such as engineering rules and steel tapes are still used for many routine measurements despite the existence of more sophisticated devices. MSLNZ's Automatic Line Scale Measuring Instrument is based on a heterodyne laser interferometer used in a configuration that compensates for Abbe errors. The position of each scale graduation is detected by monitoring the change in the diffuse reflection of a focused line of diode laser light, as a motorized trolley travels along above the scale. The signal from the diffuse reflection is used to trigger the laser measurement system at the edge of each graduation. The instrument is capable of measuring the position of every graduation on a rigid scale up to four meters in length with an uncertainty of Q(10e-6 m, 7.5e-6L) (95% confidence level). Measurement time (after set up) for a one-meter scale is less than 2 minutes.

Date Published: 22 October 2001
PDF: 8 pages
Proc. SPIE 4401, Recent Developments in Traceable Dimensional Measurements, (22 October 2001); doi: 10.1117/12.445611

Published in SPIE Proceedings Vol. 4401:
Recent Developments in Traceable Dimensional Measurements
Jennifer E. Decker; Nicholas Brown, Editor(s)