Realizing subnanometer accuracy level in gauge block measurements

A new fringe-pattern analyzing interferometer, featuring ultimate resolution of a few parts in 109, stability of readings of about 0.1 nm and non-excluded systematic uncertainties due to optic effects of less than 1 nm, has been study some systematic effects in gauge block length measurements. Measurements on steep and quartz plates are analyzed. Limitations of the present definition of the length of the block are outlined. Stability and reproducibility of the wringing procedure for steel and quartz plates are reported. A new double-ended method in length measurements of gauge blocks has been realized. It includes determination of the corrections for non-ideal optics of the interferometer, curvature of the pate and deformations of the quartz plate due to wringing of the block to its surface. The result of the length measurement is not affected, in the first approximation, by deformation of the pate and the quality of wringing.