Method for improving measurement precision by using acousto-optic device in optical heterodyne interferometry

Abstract

A method for improving measurement precision by using an acousto-optic device in optical heterodyne interferometry belongs to the field of measurement precision by using acousto-optic device in optical heterodyne interferometry in precise measurement technology. In the measurement precision by using acousto-optic device in optical heterodyne interferometry by using the acousto-optic device, by changing the polarization direction of the part light beam output during an acoustic-optic interaction process, for instance, by utilizing abnormal Gragg diffraction, the polarization direction of the first-order diffraction light with frequency converted is vertical to other light beams, particularly the polarization direction of the zero-order light with the frequency unconverted; therefore, the crosstalk light is extremely easy to be filtered. Alternatively, the polarization direction of the reference light beam can be adjusted so that the polarization direction of the reference light component in the signal light beam is vertical to the polarization direction of the reference light beam, thus leading the interference signal output by a detector to be the minimum. In conclusion, the difference among the useful light beam, the crosstalk light and the noise light on the polarization direction can be caused; by utilizing the difference, the method can inhibit the effect of the interference light effectively, so as to reduce nonlinearity, improve signal-to-noise ratio and improve the measurement precision by magnitude.

Description

Technical field: [0001] The invention belongs to the field of laser heterodyne interferometry in precision measurement technology. It is a method to eliminate or reduce the nonlinear error of laser heterodyne interferometry using acousto-optic devices. Background technique [0002] Laser heterodyne interferometry can be used to measure displacement and vibration, etc., and is one of the best nanometer measurement methods. This method is to convert the measured displacement into the frequency or phase change of the heterodyne signal, and then measure this change. Since the frequency of the heterodyne signal is much lower than the optical frequency, the photoelectric signal is easily subdivided by electronics. Higher measurement resolution is achieved, and it is easy to handle. Currently, this method can achieve picometer (pm) or better measurement resolution. [0003] However, there are common problems such as nonlinearity in technologies such as optical heterodyne interfer...

AI Technical Summary

Problems solved by technology

But the problem is that if you want to reduce the nonlinear error by an order of magnitude, such as reducing the nonlinear error to one percent, you need hundreds of times the reentrant optical path, and generally speaking, this is difficult

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