Interference Comparator for the Calibration of Line Standards Directly in Terms of Standard Wavelengths

An interference comparator has been built for the routine calibration of line standards or scales by direct reference to the vacuum wavelength of the 0.606 μ line of Kr86 which has recently become the international standard of length. The principles of construction and the performance of the comparator are given; it is shown to yield an accuracy of calibration which is mostly limited by the nature of present-day line standards or scales, viz., a few hundredths of a micron in lengths up to one meter.