Improved measurement accuracy in heterodyne laser interferometer using WDF

2009 ◽  
Vol 45 (21) ◽  
pp. 1085 ◽  
Author(s):  
W. Lee ◽  
J. Lee ◽  
K. You
Keyword(s):  
Measurement Accuracy ◽  
Laser Interferometer ◽  
Heterodyne Laser Interferometer

Detection of Seismic Wave with Laser Interferometer

2014 ◽  
Vol 681 ◽  
pp. 66-69
Author(s):  
Woo Ram Lee ◽  
Eun Hwan Oh ◽  
Min Woo Lim ◽  
Kwan Ho You
Keyword(s):  
Kalman Filter ◽  
Extended Kalman Filter ◽  
Seismic Wave ◽  
Measurement Accuracy ◽  
Laser Interferometer ◽  
Nonlinearity Error ◽  
Detection Process ◽  
Wave Detection ◽  
Wave Measurement ◽  
Heterodyne Laser Interferometer

In this paper, we propose a seismic wave detection process using a laser interferometer as a seismometer. The laser interferometer system is an important equipment with its remarkable accurate capability for displacement measurement. During the process of the seismic wave measurement, however, environmental and nonlinearity error are occurred in a heterodyne laser interferometer. Through the extended Kalman filter compensation, the distortion is reduced. With a recursive STA/LTA algorithm, the PS-time of the seismic wave is determined and then the epicenter distance can be derived. Through some simulations, it is demonstrated that the proposed algorithm can reduce error factors and improve the measurement accuracy of a seismometer.

TDC Implementation Based on Internal Delay Module of FPGA

2013 ◽  
Vol 816-817 ◽  
pp. 1063-1068
Author(s):  
Rou Gang Zhou ◽  
Yun Fei Zhou ◽  
Guang Dou Liu ◽  
Xiao Tu
Keyword(s):  
Nuclear Physics ◽  
Measurement Accuracy ◽  
Laser Interferometer ◽  
Interpolation Method ◽  
Time Measurement ◽  
Clock Signal ◽  
Signal Delay ◽  
Digital Conversion ◽  
Sampling Points ◽  
Stable Performance

Currently the time to digital converter (TDC) integrated in FPGA performs time-to-digital conversion in the carry chain mode and inter-slot offset is caused to be severe by internal wiring in the FPGA. Based on the carry chain interpolation method, this paper proposes the method for using a delay module in FPGA to achieve accurate signal delay. By calculating the phase difference of multi-clock signal between two latch sampling points, the interval between two sampling points was obtained. Experimental results indicate a measurement accuracy of 78ps or 52ps can be reached by precisely collecting time through the delay module in FPGA. Compared to the carry chain interpolation method, this method is significantly advantageous in small inter-slot offset, stable performance and convenient design and can meet the requirement for time measurement or requirement by laser interferometer with a nm-level accuracy in nuclear physics.

Model and Measurement Method of Optical Nonlinearities Caused by the Heterodyne and Homodyne Interference Terms in the Heterodyne Interferometer

2014 ◽  
Vol 613 ◽  
pp. 58-63
Author(s):  
Hai Jin Fu ◽  
Jiu Bin Tan ◽  
Peng Cheng Hu ◽  
Zhi Gang Fan
Keyword(s):  
Measurement Method ◽  
Laser Interferometer ◽  
Optical Nonlinearity ◽  
Laser Source ◽  
Optical Nonlinearities ◽  
Laser Polarization ◽  
Heterodyne Interferometer ◽  
Optical Mixing ◽  
Ultra Precision ◽  
Heterodyne Laser Interferometer

The heterodyne laser interferometer is widely applied in ultra-precision displacement measurement, but its accuracy is seriously restricted by the optical nonlinearity which arises from the optical mixing in the reference and measurement arms. In an ideal heterodyne laser interferometer, the beam from the laser source consists of two orthogonally linear-polarized components with slightly different optical frequencies and the two components can be completely separated by the polarizing optics, one traverses in the reference arm, the other traverses in the measurement arm, both of them are in the form of a pure optical frequency. However, in a real heterodyne laser interferometer, due to the imperfect laser polarization, the optics defect and the misalignment, the two components of the laser beam cant be perfectly separated, therefore both of the reference arm and the measurement arm contain a portion of the two laser components, which leads to an optical mixing in the two arms of the heterodyne interferometer and causes the cyclic nonlinearity of several to tens of nanometers.

Key technologies analysis and design of ultra-clean & ultra-stable spacecraft for gravitational wave detection

2021 ◽  
pp. 2140021
Author(s):  
Kun Chen ◽  
Xiaofeng Zhang ◽  
Tong Guo ◽  
Zhi-Ming Cai ◽  
Keyword(s):  
Gravitational Wave ◽  
Measurement Accuracy ◽  
Laser Interferometer ◽  
Gravitational Interaction ◽  
Thermal Control ◽  
Theory Of Relativity ◽  
Gravitational Wave Detection ◽  
Analysis And Design ◽  
Wave Detection ◽  
Key Technologies

The observation of gravitational wave enables human to explore the origin, formation and evolution of universe governed by the gravitational interaction and the nature of gravity beyond general theory of relativity. The groundbreaking discovery of Gravitational Wave by Laser Interferometer Gravitational-Wave Observatory provides a brand-new observation way. While detecting gravitational wave on ground is limited by noises and test scale, space detection is an optimized alternative to learn rich sources in range of 0.1 mHz–1 Hz. Considering the great significance of space gravitational wave detection, ESA proposed LISA project, CAS also proposed Taiji project. Due to the extremely weak gravitational wave signal and high measurement accuracy requirement, the spaceborne GW observation antenna is accomplished by three spacecrafts constitute isosceles triangle formation intersatellite interferometer. The arm length of the interferometer reaches millions of kilometers between them, and the measurement accuracy reaches pico-meter magnitude. There are many key technologies including pm magnitude space laser interferometer metrology, drag-free control using TM of Gravity Reference Sensor, [Formula: see text]N micro thruster, ultra-clean & ultra-stable spacecraft, etc. This paper focuses on key technologies of the ultra-clean & ultra-stable spacecraft, analyzing the design of mechanical, thermal control and magnetic clean. Moreover, it reports the preliminary results of the technological breakthrough.

A digital heterodyne laser interferometer for studying cochlear mechanics

2009 ◽  
Vol 179 (2) ◽  
pp. 271-277 ◽  
Author(s):  
Stefan Jacob ◽  
Cecilia Johansson ◽  
Mats Ulfendahl ◽  
Anders Fridberger
Keyword(s):  
Laser Interferometer ◽  
Cochlear Mechanics ◽  
Heterodyne Laser Interferometer

The Analysis and Design of a Large Stroke with High-Precision Polarized Laser Interferometer System

2016 ◽  
Vol 679 ◽  
pp. 129-134
Author(s):  
Wan Duo Wu ◽  
Qiang Xian Huang ◽  
Chao Qun Wang ◽  
Ting Ting Wu ◽  
Hong Xie
Keyword(s):  
High Precision ◽  
Measurement Accuracy ◽  
Laser Interferometer ◽  
Laser Interferometry ◽  
Phase Shifting ◽  
Single Frequency ◽  
Rejection Method ◽  
The Common ◽  
Frequency Laser ◽  
Polarization Phase

The technique utilizing single-frequency laser interferometry has very high measurement accuracy, but it has rigorous requirements for optical design which is affected by many factors. In order to achieve single-frequency laser interferometry with large stroke and high precision, the integral layout, the polarization phase shifting technique and the common mode rejection method are adopted to design the length interferometry system. This paper analyzes factors and design requirements which affect measurement accuracy with large stroke. Based on polarization phase shifting technique, the system employs the four-beam-signal detection technique and the common mode rejection method, to make a differential processing of four mutually orthogonal signals. Thus, the influences of zero-drift of intensity and environmental change on system are reduced. Combined with a 200 phase subdivision, the system achieves the resolution with 0.8 nm. Under the VC++ environment, the displacement measurement results are compensated and corrected according to the environmental parameters. Compared with the Renishaw XL-80 laser interferometer, the system has better stability in short term. In the measuring range of 60 mm, the effectiveness of the system is verified.

A heterodyne laser interferometer for dilatometer measurements

2009 ◽  
Vol 52 (12) ◽  
pp. 1319-1327 ◽  
Author(s):  
V. P. Kulesh ◽  
L. M. Moskalik ◽  
A. A. Sharov
Keyword(s):  
Laser Interferometer ◽  
Heterodyne Laser Interferometer
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