Laser speckle imaging (LSI) is a full-field blood flow imaging technique with high spatio-temporal resolution and easily controlled imaging area.It has attracted extensiveattention in biomedical application, such as intraoperative imaging, mechanism ofneurovascular coupling and evaluating drug efficiency.However, this method suffers from the problem of shallow sampling depth of blood flow, so it mainly reflects the superficial blood flow information of biological tissue. The main reason is scattering effectof biological tissue,which disturbs the waveftront of theincident laserandseverelyinfluences theimaging qualityandthedetection of the flow signal underthedeeptissue.Recently, somemethods used toimprove the sampling depthofflow signalhave been reported, such as theoptical clearing method. However, it has not been clearlyinvestigated to apply the iterativewavefrontshapingtechniqueinlaser speckle imagingthrough scattering medium.
Prof.Pengcheng Li’s group from Wuhan National Lab for Optoelectronics (WNLO)proposed to combine the iterativewavefront shapingtechnique withlaser speckle contrast analysismethod to detect therelativespeedchangesof moving objectsthrough scattering medium.Phantom experiments were performed to validate our method.After compensating the wavefront distortion caused by scattering medium with SLM,an object can be imaged through the scattering system, such as diffuser. Whentheobject is moving, the motion of scattering particles can cause spatial-temporal intensity fluctuations of imaged speckle when a coherent light is incident ona dynamic turbid medium.Thespeedmap canthenbe obtainedwiththe laser speckle temporal contrast analysis method.The method may havepotentialimplications in astronomy, biomedical imaging, securitysystemand otherrelatedengineering field.
This work, published inOptics Express(Vol. 24,No.8, pp. 8382-8390,2016), was supported in part bythe National Natural Science Foundation of China (Grant Nos. 91332121, 31471083, 61405065) and the Director Fund of Wuhan National Laboratory for Optoelectronics.
Fig. 1. Experimental setup for speed detection of moving object through scattering medium
Fig. 2.The raw imagesandthespeed mapsof moving objectthrough diffuser with wavefront correction and without wavefront correction
