Optical coherence tomography

About: Optical coherence tomography is a research topic. Over the lifetime, 19051 publications have been published within this topic receiving 477433 citations. The topic is also known as: optical coherent tomography.

Optical coherence tomography corneal mapping apparatus

Abstract: Optical coherence tomography ("OCT") corneal mapping apparatus includes an OCT apparatus having a rotating helical mirror for altering a reference beam path in the OCT apparatus; a raster scanner for raster scanning sampling optical output from the OCT apparatus; a curved mirror for transferring the sampling optical output from the raster scanner to an eye and for transferring sampling optical output reflected from the eye back to the OCT apparatus through the raster scanner; and an analyzer, coupled to the raster scanner, the rotating helical mirror, and reference and sampling interaction output from the OCT apparatus. The analyzer causes the raster scanner to scan the sampling optical output to points in a raster; causes the rotating mirror to alter the length of the reference beam path over a predetermined amount at each of the points in the raster; and provides the corneal mapping from the reference and sampling interaction output at the points in the raster.

Ultra-compact fiber-optic two-photon microscope for functional fluorescence imaging in vivo

Abstract: We present a small, lightweight two-photon fiberscope and demonstrate its suitability for functional imaging in the intact brain. Our device consists of a hollow-core photonic crystal fiber for efficient delivery of near-IR femtosecond laser pulses, a spiral fiber-scanner for resonant beam steering, and a gradient-index lens system for fluorescence excitation, dichroic beam splitting, and signal collection. Fluorescence light is remotely detected using a standard photomultiplier tube. All optical components have 1 mm dimensions and the microscope’s headpiece weighs only 0.6 grams. The instrument achieves micrometer resolution at frame rates of typically 25 Hz with a field-of-view of up to 200 microns. We demonstrate functional imaging of calcium signals in Purkinje cell dendrites in the cerebellum of anesthetized rats. The microscope will be easily portable by a rat or mouse and thus should enable functional imaging in freely behaving animals.

Correction of geometric and refractive image distortions in optical coherence tomography applying Fermat’s principle

Abstract: We describe a methodology for quantitative image correction in OCT which includes procedures for correction of nonlinear axial scanning and non-telecentric scan patterns, as well as a novel approach for refraction correction in layered media based on Fermat’s principle. The residual spatial error obtained in layered media with a fan-beam hand-held probe was reduced from several hundred micrometers to near the diffraction and coherence-length limits.

Depth-resolved model-based reconstruction of attenuation coefficients in optical coherence tomography

Abstract: We present a method, based on a single scattering model, to calculate the attenuation coefficient of each pixel in optical coherence tomography (OCT) depth profiles. Numerical simulations were used to determine the model’s response to different depths and attenuation coefficients. Experiments were performed on uniform and layered phantoms with varying attenuation coefficients. They were measured by a 1300 nm OCT system and their attenuation coefficients were evaluated by our proposed method and by fitting the OCT slope as the gold standard. Both methods showed largely consistent results for the uniform phantoms. On the layered phantom, only our proposed method accurately estimated the attenuation coefficients. For all phantoms, the proposed method largely reduced the variability of the estimated attenuation coefficients. The method was illustrated on an in-vivo retinal OCT scan, effectively removing common imaging artifacts such as shadowing. By providing localized, per-pixel attenuation coefficients, this method enables tissue characterization based on attenuation coefficient estimates from OCT data.

Interferometeric imaging with a grating based phase control optical delay line

Abstract: An apparatus for performing high speed scanning of an optical delay and its application for performing optical interferometry, ranging, and imaging, including cross sectional imaging using optical coherence tomography, is disclosed The apparatus achieves optical delay scanning by using diffractive optical elements in conjunction with imaging optics In one embodiment a diffraction grating disperses an optical beam into different spectral frequency or wavelength components which are collimated by a lens A mirror is placed one focal length away from the lens and the alteration of the grating groove density, the grating input angle, the grating output angle, and/or the mirror tilt produce a change in optical group and phase delay This apparatus permits the optical group and phase delay to be scanned by scanning the angle of the mirror In other embodiments, this device permits optical delay scanning without the use of moving parts