Motion-Based Sensing and Imaging in Scattering Media Using Speckle Intensity Correlation
Abstract
Optical sensing and imaging inside heavily scattering media are of intense interest because of their importance in biomedical, environmental, and material inspection applications. When coherent light interacts with scatterers, bright and dark intensity regions form, a phenomenon known as speckle. Often viewed as being detrimental, speckle can be exploited to yield useful information with a correlation analysis. A coherent method is presented for the imaging of a hidden object moving within thick and randomly scattering media using speckle intensity correlations over object position, with the possibility of accessing super-resolution information. With prior information about the moving object’s motion, spatial speckle intensity correlations as a function of object position can reveal the hidden object’s relative refractive index distribution. Our experimental evidence shows that it is feasible to image complex aperture-type moving objects and circular patches inside scatter that is a magnitude of order heavier than other comparable imaging modalities. Images of the moving object were obtained from speckle intensity correlation data using phase retrieval. Biological tissue was used to demonstrate the possibility of in vivo deep-tissue imaging. Speckle intensity correlations are shown to be sensitive to both the scattering strength of the embedded object and the environment, both of which are useful for sensing. We present a general theory that describes this influence of the background scattering medium and allows for imaging a hidden moving object. Additionally, we present a method to improve the sensitivity of speckle correlography in remote optical metrology. By placing a scattering slab in front of the detector, we demonstrate enhanced sensitivity, detecting the subwavelength in-plane displacement of a remote diffuse object.
Degree
Ph.D.
Advisors
Webb, Purdue University.
Subject Area
Optics|Analytical chemistry|Chemistry|Electromagnetics|Physics
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