Absolute distance measurement system based on interferometric phase comparison method

Abstract

The invention discloses a high-precision absolute distance measurement system based on an interferometric phase comparison method, belonging to the technical field of precision measurement. The system equals to the improvement on an absolute distance measurement system based on a traditional frequency scanning interferometry method, and comprises a single frequency tunable external cavity laser, a three-way optical heterodyne interferometer and a phase measurement comparison system. The single frequency tunable external cavity laser is used for laser frequency scanning, the three-way optical heterodyne interferometer is adopted for obtaining heterodyne interference signals of a reference interference arm, a measurement interference arm and a calibration interference arm in the process of laser frequency scanning, then the phase measurement comparison system is used for extracting interference phase drift distances of the calibration interference arm and the measurement interference arm in the frequency scanning process, the interference phase drift distances are in direct proportion with optical path differences of the interference arms, and therefore, the absolute distance can be measured by comparing the interference phase drift distances of the two paths of the interference arms. By adopting the three-way optical heterodyne interferometer and the phase measurement comparison system, the system does not need to measure an air refractive index when compared with the traditional frequency scanning absolute distance measurement systems, the system can overcome frequency drift and avoids the scanned range for measuring laser frequency, and therefore, frequency calibration devices, such as a Fabry-Perot cavity, and the like, are not needed.

Description

technical field [0001] The present invention is an absolute distance measurement system based on the interference phase comparison method, which mainly uses a frequency-sweeping light source and optical heterodyne interference phase detection technology to obtain the absolute distance by comparing the interference phase drift of two interference arms. It belongs to the technical field of precision measurement. It can be used in shape measurement, three-dimensional tracking control and long-distance applications. Background technique [0002] Optical interferometry can be divided into two categories: displacement interferometry and absolute distance interferometry. Displacement interferometry measures relative displacement. During implementation, the length of the interference arm must be continuously changed by using a track and a moving platform. The middle beam cannot be interrupted. On the contrary, the absolute distance interferometry measures the absolute distance. Wh...

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Problems solved by technology

Use multiple lasers to form a synthetic wavelength with a larger wavelength to increase the range of phase unambiguity in interferometry and increase the measurement distance, but the structure is too complicated

[0007] The traditional frequency scanning interferometry uses a single frequency tunable laser, and the absolute distance can be obtained by simultaneously recording the frequency scanning range and the drift of the interference phase during the frequency scanning process. The traditional frequency scanning interferometry has the following deficiencies: (1) The frequency scanning range must be very accurate, so at the beginning and end of the frequency scanning, the frequency tunable laser needs to be precisely stabilized, which requires additional frequency calibration devices to calibrate the starting and ending points of the frequency scanning, usually atomic absorption Spectrum or Fabry Perot cavity, which increases the difficulty and complexity of system control and increases the measurement time

(2) The air refractive index needs to be measured during the absolute distance measurement process, and the measurement accuracy of the air refractive index greatly affects the absolute distance measurement accuracy

(3) The interference phase is often detected orthogonally by using a zero-beat Mach-Zehnder interferometer to monitor the frequency scanning process, which increases the complexity of the system. The zero-beat Mach-Zehnder interferometer uses a polarization Beamsplitters, which lead to nonlinear errors in quadrature detection, need to be compensated by algorithms

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