Design and Performance of the 1-Metre Line-Standard Interferometer at the National Standards Laboratory, Sydney

A detailed description is given of a 1-metre line-standard interferometer which has been constructed at the National Standards Laboratory, Sydney. The results of a recent series of calibrations of standard scales are reported. A precision of 10 7 has been obtained. The existence of a difference between the optical metre as defined in 1960 and the prototype metre is confirmed, and the optical metre is found to be 0.38 μm shorter than the prototype.