Determination of phase change correction on gauge block measurement in two different interferometric measurement systems

Abstract

Phase change correction (PCC) is an important correction value of the end effect in an optical interferometry system. Normally, this value is used to compensate for gauge block measurement by an optical interferometry system based on ISO 3650:1998. Two different interferometric measurement systems in terms of fringe fraction measurement were performed to determine the phase change correction by a five-stacking method. These results are used to determine the length measurement of gauge blocks in an optical interferometer technique and consequently, to evaluate the uncertainty of gauge blocks measurement. The preliminary results for steel gauge block are shown that the value of phase change correction in a phase shift gauge block interferometer (PSGBI) system and a standard uncertainty are 35.2 nm and 5.8 nm, respectively. In contrast, the values from an average slits gauge block interferometer (ASGBI) system and a standard uncertainty are 66.0 nm and 6.0 nm, respectively. We found that the phase correction from the PSGBI system is lower than ASGBI about 0.53 - 0.56 times because the different of wave front correction in two interferometric systems. However, the lengths of gauge blocks of all materials measured by the two systems were consistent as assessed by En number. According to the study, we can conclude that phase change correction is based on the characteristics of each GBI system, surface texture characteristic in term of wringing condition and material types of gauge block and optical plates such as the fringe fraction measurement technique, and wave front error compensation. Consequently, measurements that require a high accuracy should determine the phase change correction before each measurement due to this value is not interchangeable.