Determination of phase correction arising at the interface of base platen and slip gauge material in gauge-interferometry

摘要

In gauge-interferometry if the gauge material and the base platen material are different the optical length O and the practical length L no longer remains the same and phase correction phi is to be introduced so that L = O + phi. In the commonly used method phi is found out by selecting 5 different lengths of slip gauges and finding out one- fourth of the difference between the combined optical length and the sum of the individual optical lengths. measurement being carried out at different temperatures and for that matter at different environ mental conditions. This method encompasses the problem of observation at different temperatures as well as at different environmental conditions and naturally embraces the possibility of errors associated with all the different temperatures as well as all the associated environmental parameters. In the method devised and discussed here. this problem has been taken care of very well and the gauges under observation have been subjected to the same temperature and same environmental conditions, so that the contribution of these factors towards the measurement errors is drastically reduced and the measurement error remains the minimum possible. [References: 5]