Double-refraction external cavity displacement measuring system

Abstract

The invention belongs to the technical field of laser measurement, and is characterized in that a birefringent external cavity feedback displacement measurement system is formed by using an LD-pumped single-frequency microchip Nd:YAG laser, a birefringent external cavity feedback and a measurement circuit. When the measured object moves along the laser axis, two cosine signals with a phase difference of 90 degrees are obtained in the X and Y directions of the output. Every time the measured object moves by half the wavelength, the output light intensity of the laser changes by one fringe. After the threshold light intensity is introduced, the laser light intensity of one cycle is divided into four polarization regions, each region corresponds to the displacement of one-eighth of the light wavelength of the measured object, and the displacement of the measured object can be obtained by detecting the number of polarization regions; when the measured When the moving direction of the object changes, the order in which the four polarization regions appear in each cycle also changes, so that the moving direction of the object can be judged. The device has the characteristics of compact structure, high cost performance, easy direction determination and small volume.

Description

technical field [0001] The invention belongs to the technical field of laser measurement. Background technique [0002] Laser feedback means that in the laser application system, after the output light of the laser is reflected by an external object, part of the light is fed back to the laser resonator. The feedback light carries the information of the external object and interacts with the light in the cavity to modulate the output of the laser. By demodulating the output light intensity of the laser, the information of the external measured object is obtained. Laser feedback technology, also known as self-mixing interferometry, has the same phase sensitivity and depth as traditional two-beam interferometry. However, the measurement system based on laser feedback technology has only one optical channel, which has the advantages of simple structure, compactness, easy alignment, and high cost performance. It can be applied to the measurement of displacement, velocity, absol...

AI Technical Summary

Problems solved by technology

However, there are three problems in the semiconductor laser feedback phenomenon used for displacement measurement: First, the semiconductor laser has a large divergence angle, and collimating and focusing optical elements must be added to the external cavity, resulting in a complex structure, and it is easy to generate multiple feedbacks, resulting in counting errors

Although the He-Ne laser has good collimation and can realize large-scale measurement without external cavity collimation components, the size of the He-Ne laser is huge, and the resonant cavity is hundreds or even thousands of millimeters long, and the discharge tube of the He-Ne laser It is a large heat source, which affects the stability of laser power, leads to errors in feedback signals, and causes counting errors

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