Twiddle factor neutralization velocity measurement method and device

Abstract

The invention provides a twiddle factor neutralization speed measuring method and device. The device is composed of a fiber laser, a fiber circulator, a fiber probe, a tunable laser, a 90-degree fiber optic bridge and a photoelectric detector. According to the speed measuring method, light reflected back by an object to be measured and reference light are received by the 90-degree fiber optic bridge, four paths of interference signals with the phase difference being 90 degrees are generated through interference, frequency spectra of the four signals are analyzed through the discrete Fourier transform, then, the four frequency spectra are added together to obtain a total frequency spectrum, calculation errors mainly caused by the twiddle factor are neutralized and averaged, and finally the signal frequencies are calculated by fitting the total frequency spectrum with a curve. The performance of the speed measuring device can be improved substantially, the calculation accuracy of different frequencies can be improved by several times to dozes of times, and the km / s level high speed measurement with the 100ps level time resolution and the m / s level speed resolution can be carried out.

Description

Technical field [0001] The invention belongs to the field of laser measurement, and specifically relates to a rotation factor neutralization speed measurement method and device. Background technique [0002] In shock wave physics and detonation physics, it is often necessary to measure the velocity profile. At present, a laser interferometer based on the Doppler principle is often used. The method is to illuminate a beam of laser light on the surface of the moving object to be measured, and the reflected light has a small frequency change due to the Doppler effect. If the reflected light and another reference beam are coherently detected, take out the reflected light and the reference light The frequency difference of, can calculate the speed change process of the moving object surface. This is a non-contact, non-interference test technology that can continuously monitor displacement, velocity and acceleration. [0003] At present, laser interferometers generally use a detector t...

AI Technical Summary

Problems solved by technology

[0003] At present, the laser interferometer velocimeter generally uses a detector to record the interference signal, and uses discrete Fourier transform to analyze the signal frequency. Due to the rotation factor ( , where f is the frequency, t is the time, i is the imaginary number unit, e is the natural exponent, π is the pi), the error is large when calculating the signal spectrum, and the difference between time and frequency in Fourier analysis Determining the relationship such that current interferometric velocimeters do not simultaneously have very high time and velocity resolution in high-speed measurements

Although some instruments use devices such as 3×3 couplers to generate 120-degree phase shift signals, and then use the absolute light intensity to calculate the speed, this makes them susceptible to factors such as intensity noise and device consistency, and cannot obtain very high Velocity and Time Resolution

The current laser interferometer velocimeter can achieve m / s-level velocity resolution at the time scale of 1 ns, but the velocity resolution deteriorates to tens of m / s at the time scale of 100 ps. However, the multi-scale study of the dynamic properties of materials As well as the development of ultra-high strain rate loading technology (such as pulsed laser loading), there is an urgent need for high-speed (km / s-level) measurement methods with very high time resolution (100ps level) and velocity resolution (m / s level), Provide data support for shock wave physics and detonation physics research

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