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Dive into the research topics where S. C. W. Hyde is active.

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Featured researches published by S. C. W. Hyde.


Optics Letters | 1995

Sub-100- mu m depth-resolved holographic imaging through scattering media in the near infrared.

S. C. W. Hyde; N. P. Barry; R. Jones; J. C. Dainty; P. M. W. French

We discuss the compromise between depth and transverse spatial resolution for photorefractive holographic imaging through turbid media. Results from an optimized geometry for a 45°-cut rhodium-doped barium titanate photorefractive crystal are presented, demonstrating two-dimensional imaging through turbid media with both sub-100-μm depth and transverse spatial resolution.


Optics Letters | 1995

DEPTH-RESOLVED HOLOGRAPHIC IMAGING THROUGH SCATTERING MEDIA BY PHOTOREFRACTION

S. C. W. Hyde; N. P. Barry; R. Jones; J. C. Dainty; P. M. W. French; Marvin B. Klein; Barry A. Wechsler

A depth-resolved near-infrared imaging system has been demonstrated for recording three-dimensional images of objects embedded in diffuse media. Time-gated holographic imaging employing rhodium-doped barium titanate as the recording medium is used to acquire whole depth-resolved two-dimensional images in 1 s. Millimeter depth resolution has been achieved with a transverse resolution of ~ 30 microm.


Optics Communications | 1997

2-D fluorescence lifetime imaging using a time-gated image intensifier

K. Dowling; S. C. W. Hyde; J. C. Dainty; P. M. W. French; J.D Hares

Abstract We report a 2-D fluorescence lifetime imaging system based on a time-gated image intensifier and a Cr:LiSAF regenerative amplifier. We have demonstrated 185 ps temporal resolution. The deleterious effects of optical scattering are demonstrated.


Applied Physics Letters | 1996

Holographic storage and high background imaging using photorefractive multiple quantum wells

Richard Jones; S. C. W. Hyde; M. Lynn; N. P. Barry; J. C. Dainty; P. M. W. French; K. M. Kwolek; David D. Nolte; M. R. Melloch

We report holographic, real time, depth‐resolved image acquisition, storage, and reconstruction in photorefractive GaAs/AlGaAs multiple quantum wells under high background radiation conditions. Reconstructed images of 50 μm transverse and depth resolution have been achieved using this device as a coherence gate to image through 9 mean free paths of turbid scattering medial


Journal of Modern Optics | 1999

High resolution time-domain fluorescence lifetime imaging for biomedical applications

K. Dowling; Mark J. Dayel; S. C. W. Hyde; P. M. W. French; M. J. Lever; J. D. Hares; A. K. L. Dymoke-bradshaw

Abstract We report the development of a whole-field fluorescence lifetime imaging (FLIM) system with high temporal resolution based on a time-gated image intensifier. The optimized temporal gate width is < 100 ps, and changes in the environment of a fluorescent phantom, causing lifetime differences less than 10 ps, have been imaged. The versatility of this FLIM system has been demonstrated by measuring both the temporal and spectral profiles of multiple fluorescent samples in a single acquisition. Initial fluorescence lifetime images suggest that this technique can provide a means of distinguishing between different tissue constituents.


Optics Communications | 1996

High resolution depth resolved imaging through scattering media using time resolved holography

S. C. W. Hyde; N. P. Barry; Richard Jones; J. C. Dainty; P. M. W. French

Abstract We report on time-gated holographic imaging at 450 nm using photorefractive media to achieve high depth and transverse resolution through a turbid medium. Using 70 fs pulses from a frequency-doubled mode-locked Ti: sapphire, we have demonstrated that both depth and transverse spatial resolution of 50 μm are achievable through a depth of 10 scattering mean free paths. Whole-field depth-resolved 2-D image planes were acquired in a single integration of a few seconds.


Applied Optics | 1995

Investigation of the temporal spread of an ultrashort light pulse on transmission through a highly scattering medium

Neil C. Bruce; F. E. W. Schmidt; J. C. Dainty; N. P. Barry; S. C. W. Hyde; P. M. W. French

An experimental and theoretical investigation of the temporal spread of an ultrashort light pulse on transmission through a highly scattering medium has been made. For the strongly diffuse light, the transmitted pulse may be described by a universal function whose duration can be directly related to the width of the sample. For sufficiently scattering samples, experimental data and the diffusion approximation indicate that the output pulse duration scales with the square root of the sample width.


Archive | 2001

Imaging Biological Tissue Using Photorefractive Holography and Fluorescence Lifetime

N. P. Barry; M.J. Cole; M. J. Dayel; K. Dowling; P. M. W. French; S. C. W. Hyde; R. Jones; D. Parsons-Karavassilis; M. Tziraki; M. J. Lever; K. M. Kwolek; David D. Nolte; M. R. Melloch; M. A. A. Neil; R. Juškaitis; Tony Wilson; A. K. L. Dymoke-Bradshaw; J. D. Hares

This article reviews two approaches to biomedical imaging, namely photorefractive holography as a means of realising depth-resolved imaging through turbid media and fluorescence lifetime imaging as a spectroscopic imaging modality.


conference on lasers and electro-optics | 1997

Evaluation of photorefractive holographic imaging through turbid media

N. P. Barry; Richard Jones; S. C. W. Hyde; J. C. Dainty; P. M. W. French; S. B. Trivedi; E. Dieguez

We are pursuing high spatial resolution confocal imaging of reflected NIR light as a diagnostic tool. To determine the efficacy of confocal imaging for in vivo pathology, it is critical to know the maximum thickness of scattering tissue through which biological signals can be detected. This limit depends on three factors: the fraction of signal photons generated in the focal region, the attenuation of the light to and from the focal region, and the background signal generated outside the focal region. Previous measurements of this limit used signals from a mirror,l which are much stronger than those expected from biological sources. Our previous Monte Carlo simulations* found that the greatest sources of contrast in reflection confocal imaging are changes in the index of refraction. For the index mismatches found in cells (-0.05),3 using a system NA of 0.4 we estimated these changes could be detected through 2-3 optical depths (ODs) of scattering. In this work, we have measured the maximum depth in ODs at which physiologic index mismatches can be detected. A confocal reflectometer was constructed (NA = 0.8) as shown in Fig. l a with an axial resolution of 4 pm. Two types of samples were investigated: 1) background was measured from homogenous scattering samples and 2) signal plus background was measured from scattering samples containing a planar index mismatch located at variable depths. Scattering was generated by 1-pm diameter latex microspheres. Scattering coefficients were calculated using Mie theory. The background was assessed by translating optically thick samples of scattering gelatin through the focus of the objective while recording the detected signal as function of position. The measured background scans from samples with three different scattering coefficients are plotted in Fig. 2a as a function of optical depth, where OD = (pJ (Depth.) An exponential fit to the background data indicates that each is decaying at eCoD. The initial amplitude of the background signal (B,) is directly proportional to the scattering coefficient (Fig. 2b). These data suggest that the background signal is produced by photons initially scattered outside the focal volume. Confocal signals from inhomogeneous scattering samples were measured by scanning a layered phantom with known optical properties (Fig. Ib). An index mismatch of 0.05 or 0.1 between the scattering gelatin and the scattering index fluid (IF) was used as a signal source at variable OD. The appropriate background was subtracted from each measure(b)


conference on lasers and electro-optics | 1997

High-resolution, whole-field, fluorescence lifetime imaging of fluorophore distribution and environment

K. Dowling; S. C. W. Hyde; N. P. Barry; J. C. Dainty; P. M. W. French; Alun J. Hughes; M. J. Lever; Anthony K. L. Dymoke-Bradshaw; Jonathan D. Hares; Paul A. Kellett

Fluorescence lifetime imaging (FLIM) can provide noninvasive functional/diagnostic imaging by exploiting the sensitivity of fluorescence lifetime to the environmental changes in, for example, ion concentration (e.g., Ca2+), and pH [e.g., Refs. 1 and 2].

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J. C. Dainty

National University of Ireland

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N. P. Barry

Imperial College London

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K. Dowling

Imperial College London

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R. Jones

Imperial College London

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