Precise interferometric length and phase-change measurement of gauge blocks based on reproducible wringing

Abstract

A modern fringe-pattern-analyzing interferometer with a resolution of 1 x 10(-9) and without exclusion of systematic uncertainties owing to optic effects of less than 1 nm was used to test a new method of interferometric length measurement based on a combination of the reproducible wringing and slave-block techniques. Measurements without excessive wringing film error are demonstrated for blocks with nominal lengths of 2-6 mm and with high surface flatness. The uncertainty achieved for these blocks is less than 1 nm. Deformations of steel gauge blocks and reference platens, caused by wringing forces, are investigated, and the necessary conditions for reproducible wringing are outlined. A subnanometer uncertainty level in phase-change-correction measurements has been achieved for gauge blocks as long as 100 mm. Limitations on the accuracy standard method of interferometric length measurements and shortcomings of the present definition of the length of the material artifact are emphasized.

<title>Interferometric length and roughness measurements with nanometer accuracy level</title>

“…Assuming polishing for the two sides of the 5-mm block to be equal, we obtain the mean value of the correction p5S13 = -20.06 nm. Comparing this value with the result for the 2-mm block (-20.03 nm) [11], we find that the assumption of equal polishing is reasonable. So, for the 2-mm and 5-mm tungsten carbide blocks wrung to the steel plate the phase change correction on reflection is about -20.04 nm, with the uncertainty level, probably, well below I nm.…”

Practical aspects of phase correction determination for gauge blocks measured by optical interferometry

“…He based the values of phase correction on the measurements of surface roughness determined using both a Talystep profiling instrument and a two-beam interferometer, with further visual analysis of histograms of surface heights measured using the interferometer. Titov [6] presented the slave-gauge technique as a way of reproducible wringing, which is a basis of determining phase correction. Due to the differences in global phase correction declared by different NMIs, EUROMET organized an interregional comparison of the phase correction in the field of gauge block interferometry in 1997 [7].…”

Nanometrology and high-precision temperature measurements under the temperature conditions varying in time temperature conditions

“…With the development of parallax-free methods in optical interferometry [1][2][3][4], the regime of Nanometrology can be achieved in length measurements of gauge blocks with nominal lengths in the range of 2-6 mm [3][4][5]. This becomes possible both for the measurements on steel or tungsten carbide plates [1,5], and also for doublesided measurements on quartz plates [2,4].…”

“…For the oblique incidence we have 0.1 nm and 0.2 nm for the aperture correction. It is worthy of note that both of these corrections, together with the corresponding uncertainties, can be further significantly reduced, relative to the illumination regime used in [6,7], by application of the technique of highly collimated laser beams [12,1]. The corresponding procedures were described in detail in [12,1].…”