We present a single-shot wide-field CCD based coherence-gated imaging technique that utilizes spatially separated phase-stepped images and requires only one CCD camera to achieve simultaneous acquisition of four phase-stepped images. This technique provides a relatively low cost system for depth-resolved imaging of dynamic samples. We demonstrate real-time coherence-gated imaging of a moving watch cog, 3D reconstructions of a coin, phase measurements of the surface of a test-chart and depth-resolved imaging in a weakly scattering sample of onion.

Wide-field low coherence photorefractive holography has the potential to acquire coherence gated images at over 1000 frames/second, including through scattering media. We demonstrate photorefractive holography using a photorefractive multiple quantum well device and we demonstrate that it can be applied to real-time imaging of a moving watch cog. The use of higher frame rate of the CCD cameras will permit imaging at even greater frame.

Low-coherence photorefractive holography has the potential to acquire wide-field coherence-gated images at frame rates approaching 1000 frames/s, including through scattering media. We present a quantitative analysis of the system optimization and limits of performance for coherence-gated imaging through scattering media using photorefractive holography and compare this performance to direct CCD detection. We show that, for high optical quality recording photorefractive multiple quantum well devices, photorefractive holography has the potential to provide a higher dynamic range than is possible with direct CCD-based detection.

We present a characterization of high-speed wide-field coherence-gated imaging using photorefractive holography with GaAs/AlGaAs Photorefractive Multiple Quantum Well (PRWQ) devices. Results are obtained with broadband c.w. laser illumination. The limitations of photorefractive holography using PRQW devices in our non-degenerate four-wave mixing geometry are discussed in terms of typical PRQW device parameters. We discuss the effect of the sensitivity and dynamic range of the CCD camera used to record the diffracted image and how the performance of PRQW devices may be improved in the future. We also present a spatial multiplexing technique for achieving phase-stepped single-shot wide-field coherence-gated imaging using a single CCD camera.

The parallel pixel acquisition inherent in wide-field coherence-gated imaging techniques offers the possibility of high-frame-rate imaging and volumetric imaging, including through scattering media. We discuss photorefractive holography using sensitive, dynamic photorefractive multiple quantum well (PRQW) films as a promising approach and, after reviewing the factors that determine the sensitivity of this technique, we demonstrate that high-frame-rate wide-field coherence gated imaging is possible at 830 frames per second with PRQW devices using a non-intensified camera to record the diffracted signal.

We have demonstrated real-time, wide-field depth-resolved imaging by combining the techniques of structured illumination and photorefractive holography. These proof of principle experiments illustrate the potential for providing real-time three-dimensional photorefractive holographic imaging with both reflected light and fluorescence.

This article describes a wide-field time-domain fluorescence lifetime imaging (FLIM) microscope with optical sectioning. The FLIM system utilizes a wide-field time-gated optical image intensifier, with a minimum gate width of 85 ps, to achieve high temporal resolution of fluorescence decays induced by ultrashort laser pulses. Different configurations, using excitation pulses of picojoule energy at 80 MHz repetition rate and of nanojoule energy at 10 kHz, are compared. The instrument has a temporal dynamic range spanning from 100 ps to tens of μs and is shown to have a temporal discrimination better than 10 ps. When applied to laser dye samples, it has produced FLIM maps demonstrating sensitivity to variations in both chemical species and local environment, e.g., viscosity. Wide-field optical sectioning is achieved using the technique of structured illumination, which is applied to remove out-of-focus light that can result in lifetime artifacts. The sectioning strength, which may be adjusted by choosing an appropriate spatial modulation frequency, is characterized and shown to be comparable to that of a confocal microscope. Practical considerations concerned with improving the quality of sectioned fluorescence lifetime maps, including using a large bit depth camera, are discussed.

Wide-field low coherence photorefractive holography has the potential to acquire depth-resolved images at up to 1000 frames/second, including through scattering media. We have applied it to microscopy using a diverse range of light sources.

In this paper, we briefly review our work on low-coherence photorefractive holography and report on the current state of the art. We present what is, to the best of our knowledge, the fastest-ever three-dimensional (3-D) imaging system and present results obtained with imaging at 470 frames/s (fps). We demonstrate the versatility of photorefractive holography using various sources, including LEDs, high-power diode arrays, and a novel, all solid-state broad-band laser. We present preliminary results obtained by combining the technique of structured illumination with photorefractive holography for the first time. We demonstrate that this novel holographic optical sectioning technique may be implemented for both reflection and fluorescence imaging.

We report a whole-field fluorescence imaging microscope that combines 3-D spatial resolution by optical sectioning, using structured illumination, with fluorescence lifetime imaging and spectrally-resolved imaging. We show the potential of this technique in the elimination of common artefacts in fluorescence lifetime imaging and apply it to study the dependence of the lifetime on the emission wavelength in biological tissue.

Whole-field photorefractive holography can be combined with low-coherence interferometry for three-dimensional imaging and other applications, including imaging through turbid media, but the off-axis holographic recording geometry results in a limited field of view when light of low temporal coherence is used. We show that tilting the energy fronts with respect to the wave fronts by use of prisms can eliminate this problem and point out that this approach will be useful for many linear and nonlinear wave-mixing experiments.

We report a whole-field fluorescence imaging microscope that combines 3-D spatial resolution by optical sectioning, using structured illumination, with fluorescence lifetime imaging and spectrally-resolved imaging. We show the potential of this technique in the elimination of common artefacts in fluorescence lifetime imaging and apply it to study the dependence of the lifetime on the emission wavelength in biological tissue.

Photorefractive holography can provide a whole-field coherence-gated 3-D imaging technique, applicable through turbid media, which offers a unique mechanism to discriminate against diffuse light. We demonstrate that, since all pixels are interrogated in parallel, it may be implemented at high frame rates as high as 462 frames/s using semiinsulating MQW devices and can utilize light sources of almost arbitrary spatial coherence, including low-cost LED's to achieve sub-5 (am sectioning and high power broad stripe multi-mode diode lasers or fibre-coupled diode arrays that can provide several watts of average power with a spectral widths > 3 nm. We discuss design considerations for low coherence imaging configurations, including tilting the energy-fronts using appropriate prisms to compensate for walk-off when interfering low-coherence beams offaxis.

We report high speed (~ 470 frames/s) 3-D imaging using photorefractive holography with sources of diverse temporal and spatial coherence and discuss design considerations for real-world high bit-rate imaging systems. We also propose a new real-time optical sectioning technique based on structured illumination with photorefractive holography to detect fluorescence.

We demonstrate a novel high power broadband laser source for low coherence interferometry that is based on a simple three mirror diode-pumped c.w. Cr3+ laser. The cavity design utilises a single intracavity prism to spatially disperse the oscillating laser mode within the pumped region of the laser crystal in order to counteract spectral gain narrowing. We demonstrate continuous wave spatially coherent output beams with spectral widths as wide as 37 nm, which are tunable across the gain linewidth of the laser. Using a single 100 μm stripe width 670 nm diode pump laser we obtained output powers up to 105 mW for incident pump powers of 410 mW. We demonstrate the application of this source (adjusted for a 13 nm bandwidth output) to 3-D imaging through a diffuse medium using photorefractive holography.

We demonstrate the application of a time-domain 2D fluorescence lifetime imaging (FLUVI) system to microscopy of biological tissue. We report the extension of this work to 3D FLIM microscopy. (C) 1999 Optical Society of America.