AN IMPROVEMENT OF INTERFEROMETER FOR GAUGE BLOCK CALIBRATION SYSTEM BY USING WAVELENGTH STABILIZED 532 NM, 633 NM AND 780 NM LASERS

摘要

This paper aims at improving an optical interferometer for gauge block calibration. Gauge block calibration technique by using optical interferometric method is considered as an ultimate calibration method because of it enables absolute calibration, high accuracy and ensures direct traceability to the definition of length. Therefore, national institute of metrology, calibration laboratory organization or manufactures of gauge block often adopt this optical interferometric method. We describe introducing iodine stabilized 532 nm Nd:YAG laser, rubidium stabilized 780 nm Nd:YLF laser and offset locked iodine stabilized 633 nm He-Ne laser into the interferometer of gauge block calibration system instead of a conventional standard wavelength lamp. These lasers have well coherent length and enough power to observe a well contrast interferometric fringe pattern for long gauge block. As a result, we obtained the following three improvements. The first, because of the lasers have well coherent length, it allows us direct calibration procedure, and throughput of GB calibration became drastically shortening. The second, by the direct calibration procedure that independent from other comparison GBs, it allows us to determine a coefficient of thermal expansion of the GBs easily and exactly. The third, in this way, we can reduce the uncertainty in measurement of GB calibration approximately a half compare new improved interferometer and previous one.