3 frequency heterodyne laser interferometer that doubles the resolution

摘要

A 3-frequency heterodyne laser interferometer and a method for measuring length and other physical quantifies by using the interferometer are disclosed. The 3-frequency heterodyne laser interferometer includes; a 3-frequency laser oscillating means; a beam splitter for separating the output laser beams of the oscillating means into reference beams and comparison beams to measure the counted value of secondary beat frequencies; a polarizing beam splitter; first and second corner cubic prisms; first and second polarizer; first and second beam detectors; first and second amplifiers, first and second band pass filters; a 2-channel counter; and a length displaying means. The method for measuring lengths by using the 3-frequency heterodyne laser interferometer according to the present invention, includes the steps of; generating doppler shifts by moving the second corner cubic prism in the 3-frequency heterodyne laser interferometer; and calculating the moving distance of the second corner cubic prism based on the difference between the reference beam counted value and the counted value of the doppler shifted comparison beams, thereby doubling the resolution.