Current medical imaging technologies allow visualization of tissue anatomy in the human body at resolutions ranging from 100 micrometers to 1 millimeter. These technologies are generally not sensitive enough to detect early-stage tissue abnormalities associated with diseases such as cancer and atherosclerosis, which require micrometer-scale resolution. Here, optical coherence tomography was adapted to allow high-speed visualization of tissue in a living animal with a catheter-endoscope 1 millimeter in diameter. This method, referred to as "optical biopsy," was used to obtain cross-sectional images of the rabbit gastrointestinal and respiratory tracts at 10-micrometer resolution.

In Vivo Endoscopic Optical Biopsy with Optical Coherence Tomography

Optical reflection, or in other words the loss of reflection, from a surface becomes increasingly crucial in determining the extent of the light-matter interaction. The simplest example of using an anti-reflecting (AR) surface is possibly the solar cell that incorporates an AR coating to harvest sunlight more effectively. Researchers have now found ways to mimic biological structures, such as moth eyes or cicada wings, which have been used for the AR purpose by nature herself. These nanoscopic biomimetic structures lend valuable clues in fabricating and designing gradient refractive index materials that are efficient AR structures. The reflectance from a selected sub-wavelength or gradient index structures have come down to below 1% in the visible region of the spectrum and efforts are on to achieve broader bands of such enhanced AR regime. In addition to the challenge of broader bands, the performance of AR structures is also limited by factors such as omnidirectional properties and polarization of incident light. This review presents selected state-of-the-art AR techniques, reported over the last half a century, and their guiding principles to predict a logical trend for future research in this field.

Anti-reflecting and photonic nanostructures

We describe a high-speed optical coherence domain reflectometer. Scan speeds of 40 mm/s are achieved with a dynamic range of >90 dB and a spatial resolution of 17 μm. Two applications are presented: the noninvasive measurement of anterior eye structure in a rabbit in vivo and the characterization of reflections and interelement spacing in a multielement lens.

High-speed optical coherence domain reflectometry

This paper shows the technique of optical coherence tomography in the frequency domain Handbook of Optical Coherence Tomography, MarcelDekker. Simulation of polarized OCT signal is performed using vector approach V. V. Tuchin, Handbook of Coherent Domain Optical Methods: Biomedical Diagnostics. In a little over two decades, optical coherence tomography (OCT) has become an indispensable imaging diagnostic service in eye care. This dramatic rise has. The promising potential of CP OCT combined with image analysis in human “Optical Coherence Tomography in Dentistry,” in Handbook of Biophotonics. Here are the playlist of handbook of retinal oct optical coherence tomography 1e download MP3. Before play or download some content related with handbook.

Handbook of optical coherence tomography.

Optical coherence tomography (OCT) and optical coherence microscopy (OCM) are novel techniques for noninvasive biomedical imaging based on low-coherence interferometry. OCT achieves high-spatial resolution ( 100 dB) in a fiber-optically integrated system which is suitable for application in minimally invasive diagnostics, including endoscopy. The technique of OCM combines the depth-ranging capability of OCT with the micron-scale resolution imaging capability of confocal microscopy to extend the available imaging depth of confocal microscopy up to several hundred micrometers deep in highly scattering tissues. The theoretical and technical bases for OCT and OCM imaging are described. Example OCT images are provided in gastrointestinal (GI) tissues to illustrate contrast between histological layers of the GI mucosa and differentiation of the mucosa from submucosa. Example OCM images revealing cellular-level microstructure up to several hundred micrometers deep in GI tissue are presented for the first time. The potential applications of OCT and OCM imaging in clinical diagnsotic medicine are discussed.

Optical Coherence Tomography and Microscopy in Gastrointestinal Tissues

We have implemented an all-fiber optical delay line using two linearly chirped fiber Bragg gratings cascaded in reverse order and all-fiber optics components. The features of the proposed all-fiber based technique for variable delay line are discussed theoretically and demonstrated experimentally. The non-invasive cross-sectional images of biomedical samples as well as a transparent glass plate obtained with implemented all-fiber delay line having the axial resolution of 100 mum and the dynamic range of 50dB are presented to validates the imaging performance and demonstrate the feasibility of the delay line for optical coherence tomography.

All-fiber variable optical delay line for applications in optical coherence tomography: feasibility study for a novel delay line

We demonstrate the enhancement of light extraction in 633 nm AlGaInP light-emitting diodes (LEDs) with antireflective subwavelength structures (SWS). From the contour plots by the rigorous coupled wave analysis method, it is found that the reduction of the internal reflection strongly depends on the period of SWS. The Ag nanoparticles formed by thermal dewetting were used as an etch mask for dry etch process to fabricate antireflective SWS on the LED surface. The tapered pillars on the GaP were fabricated, on average, with distances below 200 nm, satisfying the required antireflection condition at the emission wavelength. The improvement in light output power by approximately 26.4% was achieved for the fabricated AlGaInP LEDs with SWS compared to the conventional LEDs due to a strongly reduced Fresnel internal reflection at the GaP/air interface. The improved directionality in the far-field pattern was also obtained due to the directional light extraction enhancement.

Light-extraction enhancement of red AlGaInP light-emitting diodes with antireflective subwavelength structures.

We report a fabricated photonic crystal fiber (PCF) coupler, which has a rather flat coupling ratio over a 400 nm spectral range and enabled a 3-/spl mu/m resolution. It might enable a white-light as the source for biological samples.

Optical coherence tomography implemented by photonic crystal fiber

A novel all-fiber optical delay line for an advanced optical coherence tomography (OCT) system is proposed. Using the distributed reflectance characteristic of a chirped fiber Bragg grating (CFBG), the optical delay can be obtained without leaving the fiber that forms the system. The proposed delay line consists of a pair of identical CFBGs. The gratings are cascaded in reverse order to cancel the inherent wavelength dependency of CFBGs. Tunable optical delay is obtained by applying small strain on one of the CFBGs through an attached piezo actuator. The small displacement induced by the piezo actuator is amplified by a factor of up to 100 due to the distributed reflectance characteristic of the CFBGs. This principle and characteristics of the proposed optical delay line are analyzed in detail.

Novel Optical Delay Line for Optical Coherence Tomography System

The axial resolution of optical coherence tomography (OCT) is closely related to the light source spectrum width. Unfortunately, most basic sources providing the required power for decent OCT image have narrow spectra, which generate a resolution loss. Assuming the OCT system is linear shift-invariant, we can consider the system output as the convolution of the theoretical signal with a system impulse response due to this spectrum narrowness. It becomes then possible to enhance this resolution through iterative deconvolution methods (IDM). However those methods have a significant drawback, as they usually significantly enhance speckle, which is another consequence of the source spectrum narrowness. To compensate this, we rely on preliminary speckle filtering, and especially the adaptative ones, which allow tackling the speckle without blurring the image. We first studied enhancement proposed by most popular IDMs on OCT images, and then the effect of preliminary adaptive speckle filtering (ASF) by different common adaptive methods. Then, among those methods, we combined Frost filter and Richardson-Lucy deconvolution in the appropriated way; this way we both enhanced resolution by 2 and reduced speckle (raising CNR from 0.7 to 1.3)

EunSeo Choi

Papers

All-fiber variable optical delay line for applications in optical coherence tomography: feasibility study for a novel delay line

Light-extraction enhancement of red AlGaInP light-emitting diodes with antireflective subwavelength structures.

Optical coherence tomography implemented by photonic crystal fiber

Novel Optical Delay Line for Optical Coherence Tomography System

Advantages of Adaptive Speckle Filtering Prior to Application of Iterative Deconvolution Methods for Optical Coherent Tomography Imaging