Experimental study on Zeeman-birefringence dual-frequency laser interferometer with mid-frequency difference

Abstract

With the development of mechanical engineering, the moving velocity of the machine centers and the CMMs are increased to 1000 mm/s. However, at the present time the measurement speed of the commercial heterodyne interferometer can not meet the requirement. The key element of heterodyne interferometer is a dual frequency laser, which produces two lights with different frequency, whose wavelength is used as basic scale for length measurement. The frequency difference of the dual frequency laser is the primary factor which constrains the measurement speed. A new pressure birefringence dual frequency laser was put forward to be the light source of interferometer. Magnetic field was applied on this laser to eliminate frequency difference lock-in, and therefore dual frequency laser with adjustable frequency ranging from 3 MHz to 40 MHz can be obtained, which is called mid-frequency difference. Using the new laser referred above as the light source, the dual frequency laser interferometer system is constructed. Taking the HP 5528A dual frequency laser interferometer as measuring basis, this dissertation has measured a displacement of 10 mm rang in low speed by experimental system. The standard uncertainty of measurement is less than 0.1 μm, and the linearity is less than 0.002%. Through the measure experiment it is proved that this high speed measurement system is feasible and the system we designed for the new light source is correct. It offers a new way to improve the measurement velocity of dual frequency interferometer system.