Abstract
Optical coherence microscopy (OCM) is an interferometric technique providing 3D images of biological samples with micrometric resolution and penetration depth of several hundreds of micrometers. OCM differs from optical coherence tomography (OCT) in that it uses a high numerical aperture (NA) objective to achieve high lateral resolution. However, the high NA also reduces the depth-of-field (DOF), scaling with 1/NA2. Interferometric synthetic aperture microscopy (ISAM) is a computed imaging technique providing a solution to this trade-off between resolution and DOF. An alternative hardware method to achieve an extended DOF is to use a non-Gaussian illumination. Extended focus OCM (xfOCM) uses a Bessel beam to obtain a narrow and extended illumination volume. xfOCM detects back-scattered light using a Gaussian mode in order to maintain good sensitivity. However, the Gaussian detection mode limits the DOF. In this work, we present extended ISAM (xISAM), a method combining the benefits of both ISAM and xfOCM. xISAM uses the 3D coherent transfer function (CTF) to generalize the ISAM algorithm to different system configurations. We demonstrate xISAM both on simulated and experimental data, showing that xISAM attains a combination of high transverse resolution and extended DOF which has so far been unobtainable through conventional ISAM or xfOCM individually.
Highlights
Optical coherence tomography (OCT) has enabled rapid, highly sensitive, in vivo, volumetric imaging of tissues and cells and has been widely applied both in biomedical research and clinical settings [1,2,3,4]
We propose to combine Interferometric synthetic aperture microscopy (ISAM) and xfOCM to simultaneously optimize transverse resolution, DOF and signal-to-noise ratio (SNR) to achieve unprecedented Optical coherence microscopy (OCM) imaging performance
The unprocessed tomogram and the xISAM reconstructed image are shown, as well as the phase associated with an out-of-focus scatterer before and after xISAM processing
Summary
Optical coherence tomography (OCT) has enabled rapid, highly sensitive, in vivo, volumetric imaging of tissues and cells and has been widely applied both in biomedical research and clinical settings [1,2,3,4]. OCM is based on the same principles as OCT but achieves higher transverse resolution by using higher-NA optics. This increase of resolution comes at the expense of a reduced DOF, which is proportional to 1/NA2. Various solutions have been proposed to overcome this inherent trade-off between resolution and DOF. Computational techniques have been developed to obtain a larger DOF [5,6,7,8] (for a review of these methods, see [9, 10]). Developments of ISAM such as real-time [13, 14] or automated ISAM [15] have further extended the capabilities of this method
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