Double-frequency laser interferometry apparatus

Abstract

The invention relates to a double frequency laser interferometry device. The device comprises three parts, i.e. a light source light dividing light path part, a measuring light path part and a 90-degree phase difference signal receiving part. The light source light dividing light path part divides an incident light source into two lasers with frequency difference, and the two lasers enter the measuring light path part; after optical double path is realized by reflections by a measuring reflection mirror and a reference reflection mirror twice, the lasers are received by a photoelectric receiver of the 90 degrees phase difference signal receiving part. The invention adopts an acousto-optical frequency shifting device, so that a measured light and a reference light are separated at the beginning and frequency alias is avoided; and the interferometry device also adopts polarized light splitting and receiving technology, thus the interference signal with good contrast and high subdivisionprecision can be obtained.

Description

technical field [0001] The invention relates to a high-precision and large-range dual-frequency laser interferometry device. Background technique [0002] At present, in single-frequency laser interference, the single-mode frequency-stabilized helium-neon gas laser light source uses the polarization characteristics of the light source itself. In the interferometer, the beam inevitably undergoes a series of reflections and refractions. In this process The polarization state of the medium must change. If the polarization state of the two interfering beams is different, the contrast of the interference fringes will be reduced, and the light energy emitted by the laser will not be fully utilized, and harmful background light will remain. In addition, this type of interferometer is sensitive to changes in external conditions. Due to the diffraction and refraction of the atmosphere, the wavefront of light will be inclined, resulting in fewer interference fringes than the optimal n...

AI Technical Summary

Problems solved by technology

However, when the measurement accuracy is required to be at the nanometer level, the frequency mixing problem of the dual-frequency interferometer cannot be avoided when the longitudinal or transverse Zeeman laser is used, and the nonlinearity of the heterodyne interferometer is too large. The main reason is that the longitudinal and transverse Zeeman The laser polarization state radiated by the He-Ne gas laser is not ideal or unstable, coupled with the unsatisfactory performance and poor adjustment of the optical components in the optical path, the two frequencies of light in the polarization interference optical path cannot be completely separated, resulting in a large periodic error , these errors often reach a few nanometers, or even exceed 10nm, and cannot be eliminated by adjusting the optical path

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