US 12,247,824 B1
Heterodyne interferometer based on multi-target opposite displacement measurement and measurement method thereof
Haijin Fu, Harbin (CN); Xiaobo Su, Harbin (CN); Liang Yu, Harbin (CN); Pengcheng Hu, Harbin (CN); Zhaochen Pan, Harbin (CN); and Zhiwei Wang, Harbin (CN)
Assigned to HARBIN INSTITUTE OF TECHNOLOGY, Harbin (CN)
Filed by HARBIN INSTITUTE OF TECHNOLOGY, Harbin (CN)
Filed on Mar. 4, 2024, as Appl. No. 18/595,312.
Claims priority of application No. 202311538447.X (CN), filed on Nov. 17, 2023.
Int. Cl. G01B 11/14 (2006.01); G01B 9/02002 (2022.01)
CPC G01B 11/14 (2013.01) [G01B 9/02002 (2013.01)] 5 Claims
OG exemplary drawing
 
1. A heterodyne interferometer based on multi-target opposite displacement measurement, comprising a laser source for providing two spatially separated beams with different frequencies; the two spatially separated beams with different frequencies are defined as a first input beam with frequency f1 and a second input beam with frequency f2, respectively;
an output path of the laser source is sequentially arranged with a first beam splitter (PBS1) and a second beam splitter (PBS2) arranged in parallel, and the second beam splitter (PBS2) is arranged on a right side of the first beam splitter (PBS1), and both of the first beam splitter (PBS1) and the second beam splitter (PBS2) are polarization beam splitters;
the first beam splitter (PBS1) is used to divide the two spatially separated beams into two reference beams and two measurement beams;
the second beam splitter (PBS2) is used to achieve that a relative displacement in optical path of an object opposing one or both of the two measurement beams, and the splitting direction of the second beam splitter (PBS2) is perpendicular to a splitting direction of the first beam splitter (PBS1);
a first reflector (FR1) is arranged above the first beam splitter (PBS1) in a reflected light emission direction of the first beam splitter (PBS1), a third reflector (FR2) is arranged on a right side of the second beam splitter (PBS2), a second plane reflector (M2) is arranged in front of the second beam splitter (PBS2) in a reflected light emission direction of the second beam splitter (PBS2), and a first plane reflector (M1) is arranged behind the second beam splitter (PBS2) in the reflected light emission direction of the second beam splitter (PBS2); the first plane reflector (M1) and the second plane reflector (M2) jointly constitute a second reflector group; a front end face of the second beam splitter (PBS2) is attached with a second quarter-wave plate (QWP2), and a rear end face is attached with a first quarter-wave plate (QWP1);
the first reflector (FR1) and the second reflector group are used for reflecting the two reference beams and the two measurement beams;
the third reflector (FR2) is used to achieve optical path layering;
a left side of the first beam splitter (PBS1) is provided with a first photodetector (PDm) and a second photodetector (PDr);
the first photodetector (PDm) and the second photodetector (PDr) are used to detect interference signals related to the two reference beams and the two measurement beams after reflection.