Frequency modulated continuous wave (FMCW) laser radar high-accuracy signal measurement method based on phase demodulation method

A laser radar and phase demodulation technology, applied in radio wave measurement systems, instruments, etc., can solve the problems of limited signal subdivision, signal quality and low measurement accuracy, and achieve the effect of improving measurement accuracy and overcoming signal quality

Inactive Publication Date: 2013-06-19
HARBIN INST OF TECH
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Problems solved by technology

[0004] In order to solve the existing laser radar signal measurement method based on FMCW technology for workpiece shape detection, the demodulation technology for extracting beat frequency signal frequency is affected by the nonlinearity of laser frequency modulation, and when extracting beat frequency signal frequency The number of signal subdivisions is limited by imperfections in the signal quality over the entire sampling period, thus making the measurement less accurate

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  • Frequency modulated continuous wave (FMCW) laser radar high-accuracy signal measurement method based on phase demodulation method
  • Frequency modulated continuous wave (FMCW) laser radar high-accuracy signal measurement method based on phase demodulation method
  • Frequency modulated continuous wave (FMCW) laser radar high-accuracy signal measurement method based on phase demodulation method

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specific Embodiment approach 1

[0043] The specific embodiment one, the FMCW laser radar high-precision signal measurement method based on the phase demodulation method described in the present embodiment, it is realized by the following steps:

[0044] Step 1. Use the laser to measure the laser radar optical path based on FMCW technology. During the measurement, perform linear chirp modulation on the laser, and the frequency modulation function of the laser output by the laser is:

[0045] f(t)=f 0 +αt+f e (t)

[0046] Where: f 0 is the initial laser frequency, α=Ω / T m , Ω is the frequency modulation range, T m is the chirp modulation period, f e (t) is a frequency modulation nonlinear term, and t is time;

[0047] Step 2, using the phase demodulation method to obtain the relationship between the phase change of the beat frequency signal in the FM laser radar optical path and the time delay τ of the measurement optical path relative to the reference optical path, the specific method is:

[0048] Calc...

specific Embodiment approach 2

[0069] Embodiment 2. The difference between this embodiment and the FMCW laser radar high-precision signal measurement method based on the phase demodulation method described in Embodiment 1 is that in step 3, according to the phase variation of the beat frequency signal and the measurement optical path relative to The relationship between the time delay τ of the reference optical path is used to calculate the measured distance R through the formula:

[0070]

[0071] achieved;

[0072] Where: c is the speed of light, Ω is the range of frequency modulation.

[0073] The present invention compares the frequency modulation function of the laser with various curves of beat signals under nonlinear conditions and ideal conditions: when the frequency modulation range Ω=0.25GHZ, the frequency modulation period T m =5ms, nonlinear rate η=10%, where η=max(f e (t)) / Ω, the measured distance R=12m, the ideal beat frequency is f 0 =4kHz. When the laser is nonlinear, such as Figure...

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Abstract

The invention discloses a frequency modulated continuous wave (FMCW) laser radar high-accuracy signal measurement method based on a phase demodulation method, relates to a signal demodulation method for resisting laser frequency modulation nonlinear interference, and aims to the problem of low measurement accuracy due to the influence of laser frequency modulation nonlinearity of a beat frequency signal frequency demodulation technology in a conventional FMCW-technology-based laser radar signal measurement method for detecting the appearance of a workpiece, and due to the limitation of signal quality in the whole sampling time period on signal subdividing number during the extraction of beat frequency signal frequency. By using the phase demodulation method, a relationship between a beat frequency signal phase variation in a frequency modulation laser radar light path and the time delay tau of a measurement light path relative to a reference light path is obtained, a measured distance value R is calculated, and the FMCW laser radar high-accuracy signal measurement method is implemented. The method is applied to the field of high-accuracy FMCW laser radar distance measurement.

Description

technical field [0001] The invention relates to a high-precision FMCW laser radar signal measurement method based on a phase demodulation method, in particular to a signal demodulation method for resisting laser frequency modulation nonlinear interference, and belongs to the field of high-precision FMCW laser radar distance measurement. Background technique [0002] Workpiece shape detection is becoming more and more common in modern technology applications, such as the shape of large aircraft fuselage, the shape of large steam turbine blades, automatic assembly of workshop machinery, etc. are extremely frequent tasks in various fields. At present, the methods used to detect the three-dimensional coordinates of large workpieces mainly include visual measurement systems, laser trackers, three-coordinate machines, and photoelectric theodolites. Coherent detection lidar based on frequency modulated continuous wave technology (FMCW) combines the advantages of high precision, non...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01S7/48
Inventor 甘雨陈凤东唐烽刘国栋刘炳国庄志涛
Owner HARBIN INST OF TECH
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