结构光照明技术在二维激光诱导荧光成像去杂散光中的应用

Structured illumination for two-dimensional laser induced fluorescence imaging to eliminate stray light interference

背景杂散光信号的干扰制约了激光片光成像技术的发展,本文将结构光照明技术应用到激光片光成像测量中来消除杂散光的干扰.介绍了基于结构光照明技术的工作原理和实验测量系统,基于Matlab软件理论分析了相位移动结构光照明技术具有完全消除杂散光的作用,并针对稳定罗丹明B溶液进行了二维激光诱导荧光成像实验,进一步验证了相位移动结构光照明技术具有消除杂散光影响、提高二维成像精确度的作用.最后利用基于锁相放大原理的结构光照明技术实现了非稳态扩散罗丹明B溶液的二维荧光瞬态成像实验,并分析了罗丹明B溶液扩散的相关规律.

Laser sheet imaging,also called planar laser imaging,is one of the most versatile optical imaging techniquesand has been frequently used in several different areas.However,when applied to the limited operating spaceand strong light scattering media,the light originating from indirect reflections,multiple scattering andsurrounding backgrounds can produce error especially in intensity-ratio based measurements.This work is motivated by these challenges,with the overall aim of making laser sheet imaging techniqueapplicable for the study of eliminating the stray light interference.Therefore a novel two-dimensional imagingtechnique named structured laser illumination planar imaging(SLIPI)is developed based on planar laserimaging but uses a sophisticated illumination scheme i.e.spatial intensity modulation,to differentiate betweenthe intensity contribution arising from useful signals and that from stray light.By recording and dealing withimages,the SLIPI method can suppress the diffuse light and retain the useful signals.In this paper,we first use the MATLAB software to simulate the phase-shift SLIPI method,and the resultsshow that the stray light interference can be eliminated completely.Furthermore,the phase-shift SLIPI iscombined with the liquid solution(Rhodamine B solution)laser induced fluorescence(LIF)approach to imaginethe concentration distribution.By recording three images,between which this encoding is changed noticeablyonly for the useful LIF signals,the phase-shift SLIPI method is evidenced to be able to remove the diffuse lightcontribution,thus improving and enhancing the visualization quality.The instantaneous SLIPI images ofrapidly moving samples,a key feature to study dynamic liquid solution diffusion behavior,are also acquired.The lock-in amplifier SLIPI technique is then experimentally studied under Rhodamine B diffused solution,andthe phase-shift SLIPI method can remove the unwanted background interferences and achieve the significantimprovements in terms of pronounced concentration distribution within the Rhodamine B solution.The SLIPI technique is relatively inexpensive:the cost does not exceed the cost of an ordinary laser sheetarrangement noticeably,and it can combine with several other linear imaging techniques,such as Rayleighscattering,particle image velocimetry and laser-induced phosphorescence.