Square wave transformation amplitude measuring device and method based on self-mixing interference

Abstract

The invention discloses a square wave transformation amplitude measuring device based on self-mixing interference. The device comprises a light source unit, a signal processing unit and a data processing unit, wherein the signal processing unit introduces a hysteresis comparator to process signals so as to output required square wave signals, and the data processing unit searches for turning points for the output square wave signals so as to calculate the vibration amplitude of an object according to the number of fringes in the same inclined direction between adjacent turning points. The invention also discloses a square wave transformation amplitude measurement method based on self-mixing interference. According to the invention, the hysteresis comparator circuit with adjustable upper and lower limits is adopted to perform square wave transformation on an obtained laser self-mixing signal, so that the influence of external noise on the measurement stability and accuracy is effectively reduced. The self-mixing interference principle is adopted with no specific requirement on the coherence of the laser light source, so that the laser has large selection freedom. Meanwhile, the amplification factor of the signal is controllable, the measurable minimum amplitude value can reach a nanometer level, and wide-range real-time measurement is easy to realize.

Description

technical field [0001] The invention relates to the technical field of optical nanometer measurement, in particular to a square wave transform amplitude measurement device and method based on self-mixing interference. Background technique [0002] Nano-vibration measurement is becoming more and more important in many applications such as high-precision engineering technology, precision machining, and aerospace. At present, researchers have proposed some meaningful methods for measuring the amplitude of weakly vibrating objects. Among them, the measurement method based on optical technology has the advantages of non-contact and high precision, and has attracted much attention. [0003] Commonly used optical vibration measurement methods include geometric optics and optical interferometry. However, most of the reported geometric optics methods require complex and precise optical adjustment systems; in the field of laser interferometry, due to its simple optical structure and...

AI Technical Summary

Problems solved by technology

[0004] The frequency domain measurement method is sensitive to external noise and has high requirements on the signal-to-noise ratio of the signal. When the noise becomes larger, the spectrum will be unstable, and useful frequency components are easily covered by the noise spectrum, and the measurement results will become inaccurate.

The traditional fringe counting method is divided into manual counting and automatic counting. The manual counting method is time-consuming when the vibration amplitude of the measured object is large, while the traditional automatic counting method tends to count the noise voltage fluctuation at the threshold as an effective fringe, resulting in relatively large large count error

At the same time, the accuracy of the fringe counting method can usually only reach λ / 2, so it is not suitable for simple and stable measurement in real time and applications requiring nanometer-level high-precision resolution

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