多点协同动态散斑的统计特性

激光散斑被广泛应用于生物医学,成像探测以及无损检测等应用中,为了提升目标在环系统中基于散斑统计特性反馈远场激光聚焦光斑质量的评价效率和精度。提出了多通道协同探测的方法获得回波散斑信号的时间空间融合评价因子,并对散斑场统计理论、多点协同探测系统模型和散斑时间与空间频谱融合统计特性展开深入研究。首先,利用单点探测器探测动态散斑的强度波动信号,对其进行滤波、自相关和傅立叶变换后获得散斑场的功率谱,再乘以权重获得散斑评价因子,探究该评价因子监视远场光斑的可行性。然后,提出对探测面不同空间位点获得的时间信号进行拼接的方法,并列举实现该方法的先决条件。最后,通过仿真与实验验证利用散斑场融合频谱获得评价因子的有效性。结果表明,动态散斑评价因子随目标光斑尺寸的增加而减小,当探测面上4通道协同获取的信号不相关时,评价因子取平均可使精度提高2倍,而时间空间融合频谱获得的评价因子可保证精度的同时使系统带宽提高4倍。综上所述,多点协同获取的散斑评价因子可以更快速的监视远距离运动目标的光斑变化。

Statistical characteristics of multi-channel cooperative dynamic speckle metric

To improve the accuracy and efficiency of the dynamic speckle metric for non-destructively de-tecting far-field target hit-spot intensity in a Target-In-the-Loop(TIL)system,a multi-channel cooperative detection system for acquiring speckle signals is established.The theory of dynamic speckles,the simulation model of this system and the spatial-temporal spectral fusion characteristics are also investigated.As a first step,the power spectrum is obtained by filtering,auto-correlating and Fourier transforming the intensity fluc-tuations of dynamic speckle detected by the point detector.Then,the feasibility of speckle-metric,obtained by multiplying the spectrum with weights,is explored to monitor the target-focused spot.As a second step,the approach of splicing the temporal signals obtained from different spatial locations on the receiving plane is proposed.Moreover,the prerequisites of this approach are listed.Finally,the effectiveness of the proposed speckle metric obtained by fusing the spectrum is verified through simulations and experiments.The results show that the speckle metric decreases with an increase in the hit-spot size,and the four-channel space-aver-aging metric can improve the accuracy by a factor of 2 when each group of signals is uncorrelated.Moreover,the metric obtained by spatial-temporal fusion spectrum not only guarantees accuracy but also quadruples the system’s bandwidth.Therefore,the multi-channel cooperative acquisition of the speckle metric can monitor the hit-spot change of far-field moving targets more rapidly than current solutions.