Teleportal Face-To-Face System.

A teleportal system which provides remote communication between at least two users. A projective display and video capture system provides video images to the users. The video system obtains and transmits 3D images which are stereoscopic to remote users. The projective display unit provides an augmented reality environment to each user and allows users to view, unobstructed, the other local users, and view a local site in which they are located. A screen transmits to the user the images generated by the projective display via a retro-reflective fabric upon which images are projected and reflected back to the users eyes

System Design And Optimization Of Optical Coherence Tomography

Optical coherence imaging, including tomography (OCT) and microscopy (OCM), has been a growing research field in biomedical optical imaging in the last decade. In this imaging modality, a broadband light source, thus of short temporal coherence length, is used to perform imaging via interferometry. A challenge in optical coherence imaging, as in any imaging system towards biomedical diagnosis, is the quantification of image quality and optimization of the system components, both a primary focus of this research. We concentrated our efforts on the optimization of the imaging system from two main standpoints: axial point spread function (PSF) and practical steps towards compact low-cost solutions. Up to recently, the criteria for the quality of a system was based on speed of imaging, sensitivity, and particularly axial resolution estimated solely from the full-width at half-maximum (FWHM) of the axial PSF with the common practice of assuming a Gaussian source power spectrum. As part of our work to quantify axial resolution we first brought forth two more metrics unlike FWHM, which accounted for side lobes in the axial PSF caused by irregularities in the shape of the source power spectrum, such as spectral dips. Subsequently, we presented a method where the axial PSF was significantly optimized by suppressing the side lobes occurring because of the irregular shape of the source power spectrum. The optimization was performed through optically shaping the source power spectrum via a programmable spectral shaper, which consequentially led to suppression of spurious structures in the images of a layered specimen. The superiority of the demonstrated approach was in performing reshaping before imaging, thus eliminating the need for post-data acquisition digital signal processing. Importantly, towards the optimization and objective image quality assessment in optical coherence imaging, the impact of source spectral shaping was further analyzed in a task-based assessment method based on statistical decision theory. Two classification tasks, a signal-detection task and a resolution task, were investigated. Results showed that reshaping the source power spectrum was a benefit essentially to the resolution task, as opposed to both the detection and resolution tasks, and the importance of the specimen local variations in index of refraction on the resolution task was demonstrated. Finally, towards the optimization of OCT and OCM for use in clinical settings, we analyzed the detection electronics stage, which is a crucial component of the system that is designed to capture extremely weak interferometric signals in biomedical and biological imaging applications. We designed and tested detection electronics to achieve a compact and low-cost solution for portable imaging units and demonstrated that the design provided an equivalent performance to the commercial lock-in amplifier considering the system sensitivity obtained with both detection schemes

Estimation Of Longitudinal Resolution In Optical Coherence Imaging

The spectral shape of a source is of prime importance in optical coherence imaging because it determines several aspects of image quality, especially longitudinal resolution. Wide spectral bandwidth, which provides short coherence length, is sought to obtain high-resolution imaging. To estimate longitudinal resolution, the spectral shape of a source is usually assumed to be Gaussian, although the spectra of real sources are typically non-Gaussian. We discuss the limit of this assumption regarding the estimation of longitudinal resolution. To this end, we also investigate how coherence length is related to longitudinal resolution through the evaluation of different definitions of the coherence length. To demonstrate our purpose, the coherence length for several theoretical and real spectral shapes of sources having the same spectral bandwidth and central wavelength is computed. The reliability of coherence length computations toward the estimation of longitudinal resolution is discussed. © 2002 Optical Society of America

Task-Based Optimization And Performance Assessment In Optical Coherence Imaging

Optimization of an optical coherence imaging (OCI) system on the basis of task performance is a challenging undertaking. We present a mathematical framework based on task performance that uses statistical decision theory for the optimization and assessment of such a system. Specifically, we apply the framework to a relatively simple OCI system combined with a specimen model for a detection task and a resolution task. We consider three theoretical Gaussian sources of coherence lengths of 2, 20, and 40 μm. For each of these coherence lengths we establish a benchmark performance that specifies the smallest change in index of refraction that can be detected by the system. We also quantify the dependence of the resolution performance on the specimen model being imaged. © 2005 Optical Society of America

Effect Of Source Spectral Shape On Task-Based Assessment Of Detection And Resolution In Optical Coherence Tomography

We demonstrate the effect of the spectral shape of broadband light sources in a task-based approach for assessment of signal detection and resolution in optical coherence tomography. We define two binary tasks: The signal is either present or absent and the signal can be either resolved or not. In a transparent sample bounded by two uniform interfaces we study the minimum detectable change in the index of refraction as well as the minimum resolvable distance between the layers in correlation with the source spectral shape and power. Results show that the area under the receiver operating curve (AUC) for a signal-detection task is not affected by the shape of the spectrum but solely by its optical power, whereas spectral shaping has an effect, which we quantify, on the AUC for the resolution task. Moreover, the AUC is demonstrated in relation to the concept of system sensitivity for a signal-detection task. © 2005 Optical Society of America

Dispersion Control With A Fourier-Domain Optical Delay Line In A Fiber-Optic Imaging Interferometer

Recently, Fourier-domain (FD) optical delay lines (ODLs) were introduced for high-speed scanning and dispersion compensation in imaging interferometry. We investigate the effect of first- and second-order dispersion on the photocurrent signal associated with an optical coherence imaging system implemented with a single-mode fiber, a superluminescent diode centered at 950 nm ± 35 nm, a FD ODL, a mirror, and a layered LiTAO3 that has suitable dispersion characteristics to model a skin specimen. We present a practical and useful method to minimize the effect of dispersion through the interferometer and the specimen combined, as well as to quantify the results using two general metrics for resolution. Theoretical and associated experimental results show that, under the optimum solution, the maximum broadening of the point-spread function through a 1-mm-deep specimen is limited to 57% of its original rms width value (i.e., 8.1 μm optimal, 12.7 μm at maximum broadening) compared with approximately 110% when compensation is performed without the specimen taken into account. © 2005 Optical Society of America

Dispersion Manipulation In Optical Coherence Tomography With Fourier-Domain Optical Delay Line

In the last decade, Fourier-domain optical delay lines (FD-ODL) based on pulse shaping technology have emerged as a practical device for high-speed scanning and dispersion compensation in imaging interferometry such as optical coherence tomography(OCT). In this study, we investigate the effect of first- and second-order dispersion on the photocurrent signal associated with a fiber-optic OCT system implemented using a superluminescent diode centered at 950nm±35nm, an FD-ODL, and a mirror and a layered LiTaO 3 which owns suitable dispersion characteristics to model a skin specimen. We present a practically useful method associated with FD-ODL to minimize the effect of dispersion through the OCT system and the specimen combined, and quantify the results using two general metrics for axial resolution

Spectral Shaping To Improve The Point Spread Function In Optical Coherence Tomography

We demonstrate inhibition of the sidelobes of the axial point spread function in optical coherence tomography by shaping the power spectrum of the light source with a remaining power of 4.54 mW. A broadband amplified spontaneous emission source radiating at 1565 ± 40 nm is employed in a free-space optical coherence tomography system. The axial point spread functions before and after optical spectral shaping are presented. Results show that spectral shaping of the source can inhibit sidelobes of the point spread function up to 12.9 dB, with an associated small increase of 2.2 dB in noise floor in the far field. The effect of spectral shaping on axial resolution is demonstrated according to three metrics. Image quality improvement is also illustrated with optical coherence tomography images of an onion before and after spectral shaping. © 2003 Optical Society of America