Device and method for restraining de-coherence effect in heterodyne detection based on CCD camera

Abstract

The invention discloses a device and a method for restraining a de-coherence effect in heterodyne detection based on a CCD camera. The device comprises a laser device, a first beam splitter, a local oscillator light path acousto-optic frequency shifter, a signal light path acousto-optic frequency shifter, a second beam splitter, an optical antenna, a reflector, a third beam splitter, the CCD camera, an image signal processing system and a signal-to-noise ratio feedback system. The frequency of an intermediate-frequency heterodyne signal is reduced to be in a range detectable for the CCD camerathrough the two frequency shifters; a phase difference between the optical heterodyne signals of different pixels is recognized through an image processing technology, and an image signal output sequence is adjusted according to the phase difference, so that all pixel output signals are subjected to in-phase stacking and output; and meanwhile, a heterodyne signal output sequence can be adjusted again according to a signal-to-noise ratio of the heterodyne signal, and the signal-to-noise ratio of the optical heterodyne signal can be calculated again according to the adjusted heterodyne signal output sequence, until the output signal-to-noise ratio of the optical heterodyne signal is larger than or equal to a threshold value, so that the signal-to-noise ratio of the heterodyne detection is obviously improved.

Description

technical field [0001] The invention relates to the technical field of laser heterodyne detection, in particular to a CCD camera-based device and method for suppressing the decoherence effect in heterodyne detection. Background technique [0002] Laser heterodyne detection has many advantages, but the performance of this technology is restricted by various factors. Among them, in a research document published in 2013 (Dang Wenjia et al. The decoherence effect of rough targets on synthetic aperture lidar echoes [J]. Acta Physica Sinica. 62(2):024204), it was discussed that due to the target surface The decoherence effect caused by roughness leads to a decrease in the signal-to-noise ratio of heterodyne detection. The decoherence effect can be described as the mismatch between the light field of the signal light and the local oscillator light, and this phenomenon of light field mismatch is caused by the rough surface of the target. The modulation effect of the rough surface ...

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Problems solved by technology

The shortcomings of this method are: firstly, the array detection device proposed in this invention has a complex structure and is not easy to integrate, and the system of this invention needs to add a programmable amplifier at the back end of each array element of the detector array, which makes the system cost extremely high. Therefore, the inventive method has great difficulty in practice; secondly, the system uses a single-chip MCU module for a large number of division operations, and using the MCU module for division operations will introduce additional errors, and the accumulation of errors in different detection elements will reduce the stability of the system and eventually lead to signal noise. The effect of improving is not obvious

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