| 摘要 |
A Michelson-type self-aligning interferometer utilizes a laser to produce an output beam of light that is split into signal and reference beams. The signal beam is directed through a Bragg-cell, for heterodyne detection, and a beam expander, for facilitating target acquisition, toward a retroreflector located on a target body. The signal beam is thereby reflected back through the beam expander and Bragg-cell toward the resonance mirror of the laser, and is now shifted in frequency by 2 OMEGA . The returning signal beam remains co-linear with the output beam since it returns over the same path and through the same optical elements, especially the laser resonance mirror. Thus, the interferometer can accommodate a significant amount of component misalignment without loss of operation. The signal beam, once reflected from the resonance mirror of the laser and partially reflected by the beam splitter, is co-linear with the reference beam. The signal beam and reference beam are directed into a detector to produce an electrical signal. A frequency divider and a phase demodulator extract the phase of the electrical signal through heterodyne detection, the phase being proportional to the position of the retroreflector and, hence, the target body.
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