部分相干光束旋转多普勒效应的理论研究

Theoretical research on rotational Doppler effect of partially coherent beam

由于部分相干光较相干光更易获得,且在遥感探测中受大气湍流的影响更小,因此部分相干光的旋转多普勒效应研究更具应用价值.为了丰富部分相干光旋转多普勒效应的研究,本文基于高斯-谢尔模交叉谱密度函数,理论计算了部分相干光束经过旋转物体透射后探测光强的解析表达式,从而系统研究部分相干光的旋转多普勒效应.具体地,选用开口大小可调节的角掩膜,理论上模拟仿真探测光强信号的波形图随光场横截面相干度的变化关系,分析其频谱特性,并探究探测光强的可见度随相干度的变化关系及原因.理论模拟发现:相干度的变化不影响调制频率的大小,进而不影响测量旋转物体转速的准确性;大多数情况下光强信号的可见度会随着相干度的增大而增大,但在某些特殊情况下会存在零点.该理论研究为利用部分相干光的旋转多普勒效应来实现转动的远程遥感测速提供了理论依据.

Relatively to the coherent light,the partially coherent(PC)light appears more readily available and is less affected by the atmospheric turbulence within the realm of remote sensing detection.Due to at least these two trends,the research of rotational Doppler effects of the PC light secures more applications.To fill the gap in the study of PC light rotational Doppler effects,we use the Gaussian-Schell mode beam as the carrier and adopt the cross-spectral density function to theoretically calculate the analytical expression of the detected light intensity of a PC beam transmitted through a rotating object,and theoretically study the rotational Doppler effect of the PC beam.Specifically,an angle mask with adjustable opening size is chosen to simulate the variation of the waveform diagram of the detected light intensity signal with the coherence of the cross-section of the light field,analyze its spectral characteristics,and investigate the variation of the visibility of the detected light intensity with the coherence and the reasons.Theoretical simulations show that the change of coherence does not affect the magnitude of the modulation frequency,and thus does not affect the accuracy of measuring the rotational speed of rotating objects.In most cases the visibility of the light intensity signal will increase with the increase of the coherence,but in some special cases a zero point will exist.This study provides(a)a theoretical basis for the experiment of measuring the rotational speed by using the rotating Doppler effect of PC light and(b)the practical application of remote sensing speed measurement.