Owing to the inhomogeneity of the refractive index inside the sample (e.g. biological tissue) or on the surface of the sample(e.g. ground glass), light will be strongly scattered when it propagates through the sample. Therefore, we can hardly obtain the information about the objects behind the scattering medium, except for only a complex speckle pattern. To date, many approaches to realize focusing and imaging through scattering medium have been put forward. The traditional method mainly utilizes ballistic photons for imaging through scattering medium. Since the ballistic light is attenuated exponentially with the increase of depth of propagation in the scattering medium, the reconstruction from the speckle formed by scattered light is more conducive to practicability such as deep biomedical imaging. Typically, the wavefront shaping, optical transmission matrix and speckle correlation techniques which can successfully recover hidden object from the speckle, are valuable in biomedical imaging field. However, both optical transmission matrix and wavefront shaping rely on the coherence of light waves. The physical model of speckle correlation imaging is limited by the similarity of the point spread function of the imaging system. Thus, it is restrictive to achieve imaging through random scattering medium with broadband light illumination by using the current techniques.
In this paper, we present a broadband scattering imaging method based on common-mode rejection of polarization characteristic. In order to solve the problem that current scattering imaging methods are limited by the spectral width of the light source illumination, the polarization characteristic of the speckle field is explored in depth. We qualitatively analyze the difference in polarization information between the hidden object and the background noise in the speckle field. Notably, owing to the differences among autocorrelation functions of the speckle field intensity with different rotate angles of polarization, we can obtain two images where the object information contained in the speckle field and the background noise are dominant. Specifically, two speckle patterns are selected according to the maximum value and minimum value of the peak-to-correlation energy of the different speckles’ intensity autocorrelation. Afterwards, the serious background noise caused by the broadband light illumination is significantly suppressed by using polarization speckle difference imaging, and then the hidden object is reconstructed, with basic phase retrieval algorithm combined.
Comparison with conventional speckle correlation imaging technique, the value of peak signal-to-noise ratio and structural similarity index of reconstructions through using the proposed method are improved significantly, and the fitting curves are stabilized. Emphatically, the background noise item is physically handled by developing a novel physical imaging model. Furthermore, the proposed method is highly efficient and universal to recover different types of the hidden objects with better quality under broadband light illumination. Therefore, the proposed method has more potential applications in scattering imaging and biomedical imaging.
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