Dual-wavelength superheterodyne-interference wide-range high-precision real-time displacement measuring system and method

Abstract

The invention discloses a dual-wavelength superheterodyne-interference wide-range high-precision real-time displacement measuring system and method. The system is composed of two lasers between which the wavelength difference is deltalambda, three polarization splitting prisms, four splitting prisms, two acousto-optic modulators, four 1/4 waveplates, five planar mirrors, three Polaroids, a super-narrowband filter plate, two large-bandwidth transimpedance photoelectric detectors, two low-bandwidth high-sensitivity photoelectric detectors, a reference reflector, a measured reflector, a signal processing circuit and a host computer. According to the invention, a synthesized wavelength interference signal generated by dual wavelengths is used to improve the measuring range of the system, so that the measuring range of the system is greater than the range of single-wavelength interference; a superheterodyne interference method is used to demodulate and filter output signals, the phase of the synthesis wavelength can be measured directly, and real-time measurement is realized; and the super-narrowband filter plate is used to collect single-wavelength interference signals, and the precision of single-wavelength interference measurement is ensured while the measuring range is widened.

Description

technical field [0001] The invention relates to a displacement measurement system, in particular to a dual-wavelength superheterodyne interference large-scale high-precision real-time displacement measurement system and method. Background technique [0002] Common single-wavelength laser interferometric displacement measurement systems have nanoscale displacement measurement accuracy, but since the single wavelength of laser is usually about 1 μm, the period of its interference signal is only hundreds of nanometers, which limits its measurement range. The displacement measurement system needs to increase the cycle count to accurately record the phase change. Once the displacement changes rapidly or encounters a large absolute displacement change such as steps, phase ambiguity will appear. [0003] In order to solve the range problem of single-wavelength laser interference, Tilford et al. first proposed a method of using dual wavelengths to construct a synthetic wavelength to...

AI Technical Summary

Problems solved by technology

However, with the expansion of the measurement range, dual-wavelength interferometry also faces two new problems: 1. The accuracy of interferometry based on the synthesized wavelength will decrease. Difficult to achieve real-time and fast measurement

In the following decades, the dual-wavelength interferometric displacement measurement has made great progress. For example, the patent No. 02112079. The measurement accuracy is high, but its stability is poor through temperature modulation laser wavelength and other modulation methods, and it is difficult to achieve theoretical accuracy; the superheterodyne interferometry proposed by Dandliker et al. Opt.Lett.13, 339 (1988)) adding different frequency shifts to two laser beams of different wavelengths can realize real-time measurement of synthetic wavelengths, but it still does not solve the problem of the decline in the measurement accuracy of synthetic wavelengths

[0004] Existing technologies cannot solve the two problems caused by dual-wavelength interference at the same time, and meet the needs of large-scale and high-precision real-time interferometry

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