一种新型的多普勒调制技术

在传统的斩波器调制技术中,被测对象“被动”地接受外来调制光的照射,由于这种照射一般要经过一定的光学系统来完成,因此,调制照射发生在每一个光束经过的光学元件上,这些元件必定会存在某些加工缺陷,从而产生与调制照射同频率、固定位相差的杂散信号,只要这些信号在探测器的视场里,就会形成背景干扰,从而降低信噪比。利用MichelsonM-orley动态干涉技术,建立了一套基于Doppler频移原理的调制器。与传统的调制技术相比,多普勒调制技术是将被测目标自身运动产生的多普勒频移在干涉仪光路中造成的干涉场的交替变化作为调制频率来实现光的调制,可以有效地消除目标以外一切背景因光调制而产生的噪声影响,极大地改善微弱信号探测的信噪比。实验结果表明:调制信号频率稳定度(相对标准差)可达到±1%左右,能满足锁相放大器参考信号的需要。

New type of Doppler modulating technology

In the traditional modulating technology, the objects are illuminated by the modulated laser beams. In general, this kind of illumination must past through some optics systems. The modulating illumination occurs at every optics component which the modulated laser beams pass through. These optics component must have some blemishes, which could produce the same frequency of the modulated laser beams and idle signals of stable phase. If these signals are in the field of view, they can produce background disturbance, so signal-to-noise becomes low. A new type of Doppler modulator which bases on Michelson-Morlery dynamic interference technology is introduced. Compared with the traditional modulating technology, the Doppler modulating technology is that the Doppler shift of the sample＇s moving leads to alternating variation of coherent field, which is used as modulating frequency. It can decrease effectively the background noise from modulating except for the target. Stabilization of the signal frequency presented by this type of Doppler modulator is about 1%, which could satisfy the need of reference signal of the lock-in amplifier.