MAS-Net OCT: a deep-learning-based speckle-free multiple aperture synthetic optical coherence tomography.

High-resolution spectral domain optical coherence tomography (SD-OCT) is a vital clinical technique that suffers from the inherent compromise between transverse resolution and depth of focus (DOF). Meanwhile, speckle noise worsens OCT imaging resolving power and restricts potential resolution-enhancement techniques. Multiple aperture synthetic (MAS) OCT transmits light signals and records sample echoes along a synthetic aperture to extend DOF, acquired by time-encoding or optical path length encoding.

Snapshot Photoacoustic Topography Through an Ergodic Relay for High-throughput Imaging of Optical Absorption.

Current embodiments of photoacoustic imaging require either serial detection with a single-element ultrasonic transducer or parallel detection with an ultrasonic array, necessitating a trade-off between cost and throughput. Here, we present photoacoustic topography through an ergodic relay (PATER) for low-cost high-throughput snapshot widefield imaging. Encoding spatial information with randomized temporal signatures through ergodicity, PATER requires only a single-element ultrasonic transducer to capture a widefield image with a single laser shot.

Understanding optical reflectance contrast for real-time characterization of epithelial precursor lesions.

Detecting early-stage epithelial cancers and their precursor lesions are challenging as lesions could be subtle and focally or heterogeneously distributed over large mucosal areas. Optical coherence tomography (OCT) that enables wide-field imaging of subsurface microstructures in vivo is a promising screening tool for epithelial diseases. However, its diagnostic capability has not been fully appreciated since the optical reflectance contrast is poorly understood.

Geometry-Dependent Spectroscopic Contrast in Deep Tissues.

Nano-structures of biological systems can produce diverse spectroscopic effects through interactions with broadband light. Although structured coloration at the surface has been extensively studied, natural spectroscopic contrasts in deep tissues are poorly understood, which may carry valuable information for evaluating the anatomy and function of biological systems. Here we investigated the spectroscopic characteristics of an important geometry in deep tissues at the nanometer scale: packed nano-cylinders, in the near-infrared window, numerically predicted and experimentally proved that transversely oriented and regularly arranged nano-cylinders could selectively backscatter light of the long wavelengths.

Contrast of nuclei in stratified squamous epithelium in optical coherence tomography images at 800 nm.

Imaging nuclei of keratinocytes in the stratified squamous epithelium has been a subject of intense research since nucleus associated cellular atypia is the key criteria for the screening and diagnosis of epithelial cancers and their precursors. However, keratinocyte nuclei have been reported to be either low scattering or high scattering, so that these inconsistent reports might have led to misinterpretations of optical images, and more importantly, hindered the establishment of optical diagnostic criteria. We disclose that they are generally low scattering in the core using Micro-optical coherence tomography (μOCT) of 1.

Cellular resolution corneal imaging with extended imaging range.

Current optical coherence tomography (OCT) technology, which is used for imaging the eye's anterior segment, has been established as a clinical gold standard for the diagnosis of corneal diseases. However, the cellular resolution level information that is critical for many clinical applications is still not available. The major technical challenges toward cellular resolution OCT imaging are the limited ranging depth and depth of focus (DOF).

Extending the depth of focus of fiber-optic optical coherence tomography using a chromatic dual-focus design.

We report a dual-focus fiber-optic probe designed to extend depth of focus (DOF) in high-resolution endoscopic optical coherence tomography. We exploited the broad spectral bandwidth of a supercontinuum source and, in the fiber probe, the foci of the 750-1000 nm and 1100-1450 nm inputs were axially chromatically shifted. The interference signals from the two spectral bands were measured with a Si camera-based spectrometer and an InGaAs camera-based spectrometer, respectively.

Extending axial focus of optical coherence tomography using parallel multiple aperture synthesis.

Compromising the inherent trade-off between transverse resolution and depth of focus (DOF) remains a long-standing issue in optical coherence tomography (OCT). In this work, we report a novel technique-parallel multiple aperture synthesis (pMAS) to simultaneously generate multiple optical apertures in an OCT sample arm by employing a two-surface coated mirror. In the proposed pMAS, the DOF is extended by a factor of 16.

Multiple aperture synthetic optical coherence tomography for biological tissue imaging.

An inherent compromise must be made between transverse resolution and depth of focus (DOF) in spectral domain optical coherence tomography (SD-OCT). Thus far, OCT has not been capable of providing a sufficient DOF to stably acquire cellular-resolution images. We previously reported a novel technique named multiple aperture synthesis (MAS) to extend the DOF in high-resolution OCT [Optica4, 701 (2017)].

Visualizing Micro-anatomical Structures of the Posterior Cornea with Micro-optical Coherence Tomography.

Diagnosis of corneal disease and challenges in corneal transplantation require comprehensive understanding of corneal anatomy, particularly that of the posterior cornea. Micro-optical coherence tomography (µOCT) is a potentially suitable tool to meet this need, owing to its ultrahigh isotropic spatial resolution, high image acquisition rate and depth priority scanning mode. In this study, we explored the ability of µOCT to visualize micro-anatomical structures of the posterior cornea ex vivo and in vivo using small and large animals.

Endomicroscopic optical coherence tomography for cellular resolution imaging of gastrointestinal tracts.

Our ability to detect neoplastic changes in gastrointestinal (GI) tracts is limited by the lack of an endomicroscopic imaging tool that provides cellular-level structural details of GI mucosa over a large tissue area. In this article, we report a fiber-optic-based micro-optical coherence tomography (μOCT) system and demonstrate its capability to acquire cellular-level details of GI tissue through circumferential scanning. The system achieves an axial resolution of 2.

Single-camera full-range high-resolution spectral domain optical coherence tomography.

We developed spectral domain optical coherence tomography using a dual-channel spectrometer for complex conjugate artifacts (CCA) suppression. We used a three-line charge coupled device to simultaneously detect two interferometric spectra with 2π/3 phase difference. The complex interferometric signal was reconstructed by trigonometric manipulation of two real interferometric spectra, and then full-range images were obtained by use of inverse Fourier transform.

Multifiber angular compounding optical coherence tomography for speckle reduction.

We report on an integrated fiber optic design to implement multifiber angular compounding optical coherence tomography, which enables angular compounding for speckle reduction. A multi-facet fiber array delivers three light beams to the sample with different incident angles. Back-reflective/back-scattered signals from these channels were simultaneously detected by a three-channel spectrometer.

Spectral-domain optical coherence tomography with dual-balanced detection for auto-correlation artifacts reduction.

We developed a spectral domain optical coherence tomography (SD-OCT) to reduce auto-correlation artifacts (AC) using dual-balanced detection (DBD). AC were composed of the interference signals between different sample tissue depths, and shown up as artifacts in OCT images. This system employed a free-space Michelson interferometer, at the refraction plane of whose beam splitter, the light reflected experienced a π/2 phase shift with respect to the light transmitted.

Sinusoidal phase-modulating fiber-optic interferometer fringe with a feedback control system.

A displacement measurement system using a fiber-optic interferometer fringe projector with a feedback control system is presented and demonstrated. The system utilizes the integrating bucket method to detect the desired phase or the displacement and Fresnel reflection signal to realize measurement of the disturbance and feed it back to the modulated signal of the laser at the same time. The continuous signal truly reflects the error information, as the output light and reflected light share the same optical path.