A LOW-COST METHOD OF OBTAINING A STABLE ENVIRONMENT FOR A HIGHLY PRECISE DISPLACEMENT-MEASURING LASER INTERFEROMETER

This paper presents a practical and inexpensive method to achieve nano meter stability in laser interferometric displacement measurements in an actual environment, for example, in a machine shop. The system empl oyed here consists of a vacuum chamber, which maintains mechanical con nection between an inside measurement mirror and an outside target, a 6 atm air supply, three air pressure regulators, an air ejector and a 100 litre surge tank. Use of this system reduced the displacement meas urement fluctuation from 35 nm peak-to-valley/70 s in a 146.4 mm long dead path in an ordinary environment to 1.2 nm peak-to-valley/70 s (8. 2 x 10(-9)). The influences of air turbulence and floor vibration were also investigated. The total cost of this system is less than $4000.