US 12,253,392 B2
Micro-probe laser frequency modulation interferometric ranging method and system
Yisi Dong, Harbin (CN); Wenrui Luo, Harbin (CN); Wenwen Li, Harbin (CN); Chen Zhang, Harbin (CN); Jinran Zhang, Harbin (CN); and Pengcheng Hu, Harbin (CN)
Assigned to Harbin Institute of Technology, Harbin (CN)
Filed by Harbin Institute of Technology, Harbin (CN)
Filed on Jun. 17, 2024, as Appl. No. 18/744,803.
Claims priority of application No. 202310968558.8 (CN), filed on Aug. 2, 2023.
Prior Publication US 2025/0044128 A1, Feb. 6, 2025
Int. Cl. G01D 5/353 (2006.01)
CPC G01D 5/35306 (2013.01) 8 Claims
OG exemplary drawing
 
1. A micro-probe laser frequency modulation interferometric ranging method, comprising:
S1, activating a laser wavelength modulated light source (2); and outputting, by the laser wavelength modulated light source (2), a laser to an input port of a beam splitter (3);
S2, outputting, by a second output port of the beam splitter (3), a part of the laser to a laser wavelength detector (4); and outputting, by a first output port of the beam splitter (3), another part of the laser to a first port of a fiber optic circulator (5);
S3, outputting, by a second port of the fiber optic circulator (5), the another part of the laser as an output laser to a fiber optic jumper (6), thereby making a fiber optic end surface of the fiber optic jumper (6) reflect a part of the output laser to obtain a first reflected light and making the fiber optic jumper (6) transmit another part of the output laser to a to-be-measured object (8); receiving, by the to-be-measured object (8), the another part of the output laser to reflect from a surface of the to-be-measured object (8) and generate a second reflected light which is returned and coupled to the fiber optic jumper (6); and generating, by interference of the first reflected light and the second reflected light, an interferometric measurement signal in the fiber optic jumper (6);
S4, outputting, by the fiber optic jumper (6), the interferometric measurement signal to the second port of the fiber optic circulator (5); and outputting, by a third port of the fiber optic circulator (5), the interferometric measurement signal to a photodetector (9);
S5, converting, by the photodetector (9), the interferometric measurement signal into an electrical signal; and inputting, by the photodetector (9), the electrical signal to a modulation and demodulation system (1);
S6, obtaining, by the laser wavelength detector (4), a locked acetylene gas absorption peak Px; recording a laser wavelength λ1 corresponding to the locked acetylene gas absorption peak Px by looking up a table; collecting, by the modulation and demodulation system (1), the electrical signal from the photodetector (9) to perform phase generated carrier (PGC) demodulation to obtain current phase information φ1; and transmitting, by the modulation and demodulation system (1), the current phase information φ1 to an upper computer (10) to be recorded;
S7, recording, by the upper computer (10), a demodulation phase output value φ(t) continuously by continuously changing a wavelength of the laser outputted from the laser wavelength modulated light source until a modulation absorption wavelength of the laser wavelength modulated light source (2) is locked to another locked acetylene gas absorption peak Py; recording, by the upper computer (10), a laser wavelength λ2 corresponded to the another locked acetylene gas absorption peak Py by looking up the table; and recording, by the upper computer (10), a current PGC demodulation phase φ2;
S8, calculating to obtain an initial dead-path distance L0 based on recorded parameters; and
S9, measuring, by a fiber optic sensing probe, a relative displacement L(t), and expressing a distance L between the to-be-measured object (8) and a micro-probe fiber optic laser interferometer as follows:
L=L0+L(t).