New Approach in Interferometric Length Measurements

Interferometric length measurements without parallax error, based on the phenomenon of the reproducible wringing, are demonstrated. Using reproducible wringing together with the slave-block technique, accuracy level below 1 nm can be obtained for blocks of a few mm length with small flatness deviation. Phase change correction determination with sub-nm uncertainty is achieved for blocks up to 100 mm. Comparing the results of the double-ended method on a transparent reference plate with the reproducible wringing results, measurements without parallax error can be performed in the general case with a nm uncertainty.