Continuous monitoring of cerebral blood oxygenation is critically important for the management of many lifethreatening
conditions. Non-invasive monitoring of cerebral blood oxygenation with a photoacoustic technique offers
advantages over current invasive and non-invasive methods. We introduce a Monte Carlo XYZ-PA to model the energy
deposition in 3D and the time-resolved pressures and velocity potential based on the energy absorbed by the biological
tissue. This paper outlines the benefits of using Monte Carlo XYZ-PA for optimization of photoacoustic measurement
and imaging. To the best of our knowledge this is the first fully integrated tool for photoacoustic modelling.
We present a novel optical quantum sensor using spectral
hole-burning for detecting signals in ultrasound-modulated
optical tomography. In this technique, we utilize the capability of sub-MHz spectral filtering afforded by a spectral hole
burning crystal to select the desired spectral component from the ultrasound-modulated diffuse light. This technique is
capable of providing a large etendue, processing a large number of speckles in parallel, tolerating speckle decorrelation,
and imaging in real-time. Experimental results are presented.
Broadband RF imaging by spatial Fourier beam-forming suffers from beam-squint. The compensation of this frequency dependent beam-steering requires true-time-delay multiple beam-forming or frequency-channelized beam-forming, substantially increasing system complexity. Real-time imaging using a wide bandwidth antenna array with a large number of elements is inevitably corrupted by beam-squint and is well beyond the capability of current or projected digital approaches. In this paper, we introduce a novel microwave imaging technique by use of the spectral selectivity of inhomogeneously broadened absorber (IBA) materials, which have tens of GHz bandwidth and sub-MHz spectral resolution, allowing real-time, high resolution, beam-squint compensated, broadband RF imaging. Our imager uses a self-calibrated optical Fourier processor for beam-forming, which allows rapid imaging without massive parallel digitization or RF receivers, and generates a squinted broadband image. We correct for the beam squint by capturing independent images at each resolvable spectral frequency in a cryogenically-cooled IBA crystal and then using a chirped laser to sequentially read out each spectral image with a synchronously scanned zoom lens to compensate for the frequency dependent magnification of beam squint. Preliminary experimental results for a 1-D broadband microwave imager are presented.
An optical beamformer capable of controlling a phased array antenna in receive/transmit mode for multiple simultaneous independent rf beams is proposed. The processor can be programmed to sweep the antenna aperture following an independent angular sequence for each rf beam. A two-beam two-channel version of the beamformer has been experimentally demonstrated. The optical beamformer processes two rf beams and it is based on a ternary array of three delay lines. Measurements are performed for both receive and transmit modes and for rf signals between 0.5 and 1.5 GHz. We present beampattern results showing that two independent beams can be steered simultaneously. In the transmit mode both rf beams are characterized for a broadside target position. In the receive mode the beamformer performance is characterized by detecting two rf beams independently.
KEYWORDS: LIDAR, Crystals, Sensors, Signal detection, Holography, Modulation, Laser crystals, Signal processing, High power lasers, Pulsed laser operation
We introduce a new approach to coherent LIDAR remote sensing by utilizing a quantum-optical, parallel sensor based on spatial-spectral holography (SSH) in a cryogenically cooled inhomogeneously-broadened absorber (IBA) crystal that is used to sense the LIDAR returns and perform the front-end range-correlation signal processing. This SSH sensor increases the LIDAR system sensitivity through range-correlation gain before detection. This approach permits the use of high-power, noisy, CW lasers as ranging waveforms in LIDAR systems instead of the highly stabilized, injection seeded and amplified pulsed laser sources required by most coherent LIDAR systems. The capabilities of the IBA media for many 10s of GHz bandwidth and sub-MHz resolution, while using either a coded waveform or just a high-power, noisy laser with a broad linewidth (e.g. a random noise LIDAR) may enable a new generation of improved LIDAR sensors and processors. Preliminary experimental demonstrations of LIDAR range detection and signal processing for random noise and chirped transmitted waveforms are presented.
We present an optical approach to 1-D broadband microwave imaging. The imager uses a Fourier optical beamformer to generate a squinted broadband image which is then spectrally resolved by burning a spatial distribution (an image) of spectral signals into a spectral-hole burning material. This spatial-spectral image corresponds to the spectral content of the image at each resolveable spatial point. These narrowband images may be sequentially read out with a chirped laser, scaled to compensate for beam squint, and summed to form a broadband microwave image.
We present a non-mechanical, dynamically programmable, all-optical image rotator, which can rotate an input image to any angle or a grid given by 360°/2n, where n is the number of stages. The image rotator uses cascaded stages in which each stage rotates the image by an angle given by half the previous stage. Each stage uses an Ferroelectric Liquid Crystal (FLC) polarization switch to select between a straight through path and a deflected path with an odd number of bounces, that when rotated to an angle, operates as an image rotating prism. An FLC is used for each stage to choose the polarization and therefore whether to rotate the image or not. By switching the FLC director orientation by 45 for each stage, images can be rotated to an arbitrary angle at a speed of several KHz.
KEYWORDS: Optical correlators, 3D acquisition, Computer generated holography, Holograms, 3D image processing, Fourier transforms, Signal to noise ratio, Object recognition, Phase only filters, Cameras
A novel optical correlator for three-dimensional (3-D) object recognition is proposed herein. Several projections of a 3-D scene are recorded under white light illumination and fused into a single complex two-dimensional function. After properly filtering this function, it is then coded into a computer-generated hologram (CGH). When the CGH is coherently illuminated, a correlation space between the 3-D tested scene and the reference function is reconstructed, in which light peaks indicate on the existences and locations of true targets in the observed 3-D scene. Experimental results are presented.
We propose a method of synthesizing computer-generated holograms of real-life three-dimensional (3-D) objects. An ordinary digital camera illuminated by incoherent white light records several projections of the 3-D object from different points of view. The recorded data are numerically processed to yield a two-dimensional complex function, which is then encoded as a computer-generated hologram. When this hologram is illuminated by a plane wave, a 3-D real image of the object is reconstructed.
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