Abstract
Multiple scattering is a major barrier that limits the optical imaging depth in scattering media. In order to alleviate this effect, we demonstrate aberration-diverse optical coherence tomography (AD-OCT), which exploits the phase correlation between the deterministic signals from single-scattered photons to suppress the random background caused by multiple scattering and speckle. AD-OCT illuminates the sample volume with diverse aberrated point spread functions, and computationally removes these intentionally applied aberrations. After accumulating 12 astigmatism-diverse OCT volumes, we show a 10 dB enhancement in signal-to-background ratio via a coherent average of reconstructed signals from a USAF target located 7.2 scattering mean free paths below a thick scattering layer, and a 3× speckle contrast reduction from an incoherent average of reconstructed signals inside the scattering layer. This AD-OCT method, when implemented using astigmatic illumination, is a promising approach for ultra-deep volumetric optical coherence microscopy.
Highlights
Deep imaging inside scattering biological media is desirable for many applications
The level of multiple scattering (MS) rejection can be further enhanced through the combination of a confocal and coherence gate, which is beneficial for higher numerical aperture (NA) optical coherence tomography/microscopy (OCT/optical coherence microscopy (OCM)) [9]
The slight reduction in peak signal at the USAF target plane can be attributed to signal variations from different point spread function (PSF) passing through the scattering medium, and fluctuations in the system
Summary
Deep imaging inside scattering biological media is desirable for many applications. Such a capability could extend the investigation of biological systems into new regimes. It can be beneficial for both fundamental in vitro studies in engineered cell cultures or animal models of disease in vivo, as well as for clinical diagnostics or monitoring of therapies. In label-free coherent imaging at optical frequencies, e.g. with optical coherence tomography (OCT), the imaging depth within scattering tissues is limited to ~1-2 mm [1,2,3]. The level of MS rejection can be further enhanced through the combination of a confocal and coherence gate, which is beneficial for higher numerical aperture (NA) optical coherence tomography/microscopy (OCT/OCM) [9]. Longer wavelengths that have a lower scattering coefficient in tissue have been shown to provide increased imaging depth in coherent imaging [10,11,12], as well as nonlinear microscopy [13, 14]
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