Research On Non-invasive Imaging Through Scattering Media

Non-invasive optical imaging has important applications in various fields ranging from biotechnology to optical detection.However,inhomogeneous samples,such as biological tissues,scatter light,which results in a complex speckle pattern on the detector.With increasing depth,separating the low amount of ballistic light from the scattered light becomes a big challenge.Several techniques have been proposed to focus light by making use of feedback signals to optimize the incident wavefront to recreate a focus that is then used for rasterscanning microscopy.These techniques require access to both sides of the scattering layer to optimize the wavefront,which strongly limits their application in real-case scenarios.To overcome this,other strategies have been proposed based on wavefront shaping and various feedback signals such as fluorescence or ultrasound signals.However,these approaches either require long acquisition times,entail the use of interferometric detection systems,or are limited to small fields of view(Fo V).Therefore,those techniques are difficult to meet the requirements of practical applications,such as biomedical imaging applications.Inspired by the optical memory effect,researchers have proposed a speckle correlation imaging technique,which enables non-invasive imaging through scattering media.Furthermore,it is verified that the speckle correlation imaging technique based on the optical memory effect also has a high temporal resolution.Although the current approaches can achieve non-invasive imaging through scattering media,they are suffering from the following challenging problems:(i)The existing speckle correlation imaging methods based on optical memory effect require retrieving the fourier phase information of the hidden object using a phase retrieval algorithm,the direction of the hidden target is often ignored,which makes it difficult to extend the method to color imaging?(ii)The field of view of the speckle correlation imaging method is limited by the optical memory.Due to the limitation of the physical characteristics of the effect,it is difficult to achieve non-invasive imaging with a large field of view?(iii)The optical memory effect range of the scattering medium decreases with the increase of depth.When imaging is performed at a certain depth through the scattering medium and the system When there are multiple targets,the multi-target information aliasing and the sharp reduction of the optical memory effect range bring great challenges to this method.Aiming at the shortcomings of the existing non-invasive scattering imaging methods,this paper mainly does the following research:(1)Aiming at the current problems of speckle correlation imaging and spectral reconstruction of spectral transmission matrix,the basic principles of spectral reconstruction of spectral transfer matrix and speckle autocorrelation imaging are studied,and they are verified numerically and experimentally respectively.Further,we successfully reconstruct the image of the hidden object using the extended spectral transmission matrix technique.(2)A color imaging through scattering media based on phase retrieval with triple correlation is proposed.The core of this joint work lies in the mutual independence of the triple correlation phase recovery and amplitude recovery steps,which realize the deterministic recovery of the target direction information.For the first time,color imaging through scattering media has been demonstrated in a non-invasive manner without a wavefront shaping technique.Compared with the traditional color imaging method through a scattering medium,this skill does not require correcting the wavefront of the incident beam and has more advantages in terms of timeliness.At the same time,this technique can be effectively combined with traditional spectral imaging approaches to achieve spectral imaging.(3)A large field-of-view non-invasive imaging through scattering layers using fluctuating random illumination is put forward.The technique achieves this by demixing speckle patterns emitted by a fluorescent object under variable unknown random illumination,using matrix factorization and a fingerprint-based reconstruction.(4)We proposed a multi-optical memory effect ranges imaging method through the scattering media using multi-frame speckle illumination.In this method,the speckle fingerprints of different point sources are achieved by using a demixing algorithm,and then the speckle fingerprints are classified by the speckle classification approach.Image reconstruction was performed separately for the optical memory effect range.At the same time,the application field of this method is not limited to the spatial optical memory effect,but also applies to the time-dimensional optical memory effect and the spectral-dimensional optical memory effect.