Measurement of the Absolute Diameter of Cylindrical Gauges by Grazing Incidence Interferometry

1.0 Introduction Grazing incidence interferometry has been applied successfully to the measurement of the form of cylindrical parts [1]. An extension of this technique for the measurement of absolute diameter by comparison with a calibrated artifact of similar diameter (typically within 4-10 μm) has been described previously [2]. This limitation is directly attributable to the 2π phase ambiguity inherent in this kind of measurement, and necessitates the use of a series of calibrated artifacts to cover a range of diameters. This paper describes a further extension that permits absolute diameter measurements over an extended dynamic range (over 25 mm with sub-micron resolution) using only one calibration master. Sources of measurement uncertainty are identified and discussed briefly. Results of absolute diameter measurement are compared with traditional two-point contact measurements and are observed to agree to better than ±0.1μm.