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A novel optical coherence tomography system that can perform scanless two dimensional imaging without Fourier transform is proposed and demonstrated. In the system, a convex cylindrical mirror generates an extended spatial distribution of optical delay in the reference arm and a cylindrical lens is used to form a focused line beam in the sample arm. A charge-coupled device camera captures the two dimensional tomographic image of a sample in a snap-shot manner. Due to its simple configuration and operation, the system is suitable for developing a compact device for tomographic imaging and measurement.

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The application of optical absorption spectra in prognostic prediction has hardly been investigated. We developed and evaluated a novel two dimensional absorption spectrum measurement system (TDAS) for use in early diagnosis, evaluating response to chemoradiation, and making prognostic prediction. The absorption spectra of 120 sets of normal and tumor tissues from esophageal cancer patients were analyzed with TDAS ex-vivo. We demonstrated the cancerous tissue, the tissue from patients with a poor concurrent chemoradiotherapy (CCRT) response, and the tissue from patients with an early disease progression each had a readily identifiable common spectral signature. Principal component analysis (PCA) classified tissue spectra into distinct groups, demonstrating the feasibility of using absorption spectra in differentiating normal and tumor tissues, and in predicting CCRT response, poor survival and tumor recurrence (efficiencies of 75%, 100% and 85.7% respectively). Multivariate analysis revealed that patients identified as having poor-response, poor-survival and recurrence spectral signatures were correlated with increased risk of poor response to CCRT (P = 0.012), increased risk of death (P = 0.111) and increased risk of recurrence (P = 0.030) respectively. Our findings suggest that optical absorption microscopy has great potential to be a useful tool for pre-operative diagnosis and prognostic prediction of esophageal cancer.

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A prototype of a profilometer was built with the technique of composite interferometry for measurement of the distribution of both the amplitude and phase information of the surface of a material simultaneously. The composite interferometer was composed of a Michelson interferometer for measuring the surface profile of the sample and a Mach-Zehnder interferometer for measuring the phase deviation caused by the scanning component and environmental perturbations. A high-sensitivity surface profile can be obtained by use of the phase compensation mechanism through subtraction of the phases of the interferograms detected in the two interferometers. With the new design and improvement of robustness of the optical system, the measurement speed and accuracy were significantly improved. Furthermore, an additional optical delay component results in a higher sensitivity of the interference signal. This prototype of vibration-immune profilometer was examined to have a displacement sensitivity of 0.64 nm.

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We proposed and demonstrated a fiber-based composite interferometer, which can perform surface profile measurements with sensitivity at the nanometer scale. With the proposed phase-compensation mechanism, the phase deviation due to the instability of the optical delay component and environmental perturbations can be simultaneously compensated. The measurement sensitivity and imaging speed can be significantly improved such that the system can be used as a high-speed, high-resolution, and wide-field dynamical imaging system. The axial precision of the system was examined to be 0.82 nm. High-resolution time-lapsed dynamical imaging of onion cells during dehydration processes were performed with this system with one frame captured in 75 s.

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We proposed and demonstrated a low-cost optical system for surface profilometry with nanometer-resolution. The system is based on a composite interferometer consisting of a Michelson interferometer and a Mach-Zehnder interferometer. With the proposed phase compensating mechanism, the phase deviation due to the instability of the optical delay system and environmental perturbation can be compensated simultaneously. The system can perform a wide-field imaging in the millimeter range and a measurement with the axial resolution within +/-5 nm without special shielding and protection of the system as well as any special preparation of the sample.

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A polarization-sensitive optical coherence tomography (PSOCT) system using a femtosecond-laser as the broadband light source is implemented with the axial resolution of 5 microm in free space. Through the design of path-length difference between the two polarization inputs and the modulation of one of the polarization inputs, the PSOCT images of various input and output polarization combinations can be distinguished and simultaneously collected. The PSOCT system is then used for in vitro scanning of the myocardium tissues of normal and infarcted rat hearts. The destruction of the birefringence nature of the fiber muscle in the infarcted heart can be clearly observed.

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We propose and demonstrate what is to our knowledge a novel technique of improving the spatial resolution of an optical coherence tomography (OCT) system given a non-Gaussian light source spectrum. By using dispersive materials in the reference arm of the OCT system, the resultant dispersion variation led to a full-width at half maximum (FWHM) of the interference fringe envelope smaller than the Fourier transform-limited value of a Gaussian spectral shape with the same spectral FWHM, at the expense of significant tails. The effects of the tails, which would blur the OCT images, were tremendously reduced with a retrieval algorithm. Simulation results and processed OCT scanning images have shown the capability of the proposed technique.