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Results for “Optical Devices”

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At least 811 records · Page 45Linked to original sources
PubMed2006

Liquid crystal polarization-converting devices for edge and corner extractions of images using optical wavelet transforms.

Optical properties of radially polarized light generated by liquid crystal (LC) polarization-converting devices with two LC molecular orientations (+/-180 degrees and +/-90 degrees twist modes) are measured and the applicability to optical wavelet transforms (WTs) are discussed. It is found that the radially polarized lights in both the +/-180 degrees and +/-90 degrees twist modes can be regarded as wavelets. Based on the principle of WT, feature extractions of a simple binary image are carried out by applying the LC polarization-converting device to a shadow-casting system. Unique feature extraction properties of the shadow-casting system using the LC polarization-converting device and a LC microlens array are discussed. It is experimentally confirmed that edge and corner features are successfully extracted using the LC polarization-converting device with +/-180 degrees and +/-90 degrees twist modes, respectively.

Journal Article↗
PubMed1995

Side-firing devices for laser prostatectomy. An overview.

Transurethral laser coagulation of the prostate has become an accepted treatment for benign prostatic hyperplasia (BPH). The most common method is the use of a sideward-firing fiber that, once inserted in the prostatic area, irradiates the abundant prostatic tissue with Nd:YAG laser light. In this study, eight different side-firing fibers that are commercially available were evaluated. The devices can be characterized by the way laser light is deflected sideward and by their thermal behavior. Most of the eight devices differ with regard to the angle at which the laser beam is deflected, the spot size on the irradiated tissue surface, and the heating of the device itself. Implementation of the optical and thermal characteristics of each device in the treatment protocol will contribute to the optimal use of laser energy for prostatectomy.

Equipment Design↗
PubMed2005

Coherent analysis of quantum optical sideband modes.

We demonstrate a device that allows for the coherent analysis of a pair of optical frequency sidebands in an arbitrary basis. We show that our device is quantum noise limited, and hence applications for this scheme may be found in discrete and continuous variable optical quantum information experiments.

Journal Article↗
PubMed2006

Latex immunoagglutination assay for a vasculitis marker in a microfluidic device using static light scattering detection.

We have developed a microfluidic immunoassay device using fiber optics to detect static light scattering (SLS) of latex microsphere agglutination. A 400-mum silica fiber was used to deliver blue light emitting diode (LED) or red laser light sources. A miniature, portable spectrometer was used to measure forward light scattering intensity collected by the same type of multi-mode fiber. To first show feasibility, anti-mouse IgG were used as target biomolecules and highly carboxylated polystyrene latex microspheres (510 nm) coated with mouse IgG were used as probes. Next, we tested for the vasculitis marker, anti-PR3, using the same type of microspheres coated with PR3 proteins. No false negatives or positives were observed. A limit of detection (LOD) of 50 ng mL(-1) was demonstrated for the vasculitis marker, anti-PR3. (Plasma samples from patients with vasculitis exhibited anti-PR3 at a median level of 380 ng mL(-1).) The optical detection system works without any fluorescence or chemiluminescence markers. The entire system proposed here is cost effective, small in size, and re-usable with simple rinsing. This may eventually lead to a portable, low-cost, re-useable, microfluidic, point of care immunoassay device.

Antibodies↗
PubMed1981

Optic nerve clipping for hemostasis during enucleation.

An instrument is described for sectioning the optic nerve during enucleation that has several advantages over presently used techniques. the instrument applies a nonreactive, tantalum clip around the optic nerve, and a built-in knife blade transects the nerve anterior to the clip. In addition to providing rapid and effective hemostasis of the vessels within and surrounding the optic nerve, the device cuts only tissue that is encompassed by the clip and not extraneous structures.

Hemostasis, Surgical↗
PubMed2005

High-energy quasi-phase-matched optical parametric oscillation in a periodically poled MgO:LiNbO3 device with a 5 mm x 5 mm aperture.

Fabrication of a 5 mm thick periodically poled MgO-doped LiNbO3 device with a 32.1 microm period for mid-infrared generation was demonstrated. The periodic structure was evaluated by measurement of second-harmonic generation with the d31 coefficient. Optical parametric oscillation using this device with an uncoated 5 mm x 5 mm aperture and a 36 mm effective length realized a high-energy output of 77 mJ for both signal (wavelength 1.83 microm) and idler (2.54 microm) waves with a 72% slope efficiency at 110 mJ pumping of a Q-switched Nd:YAG laser with a 12 ns pulse duration.

Journal Article↗
PubMed2007

Realization of an optical communication tunable filter using a diffraction-based optical system.

Optical bandpass tunable filters are key elements for dense WDM optical communication systems. Recently, a realization of optical linear transformation using a spatial diffraction optical system was presented and theoretically analyzed [J. Opt. Soc. Am. A21, 732 (2004)]. We present an optical bandpass tunable filter based on this optical system and a spatial light modulator. The mathematical analysis and additional computer simulations for testing the filter's basic parameters using the Fresnel diffraction theory are presented. Some newly obtained laboratory experimental results of the device in the optical visible spectrum will be shown.

Journal Article↗
PubMed2003

Preliminary results using ultrasound transmission for image-guided thermal therapy.

The feasibility of using an acoustic camera as a real-time imaging device for thermal surgery was investigated. The study compares camera images of tissue samples taken before, during and after a volume of tissue was thermally coagulated using focused ultrasound (US). This apparatus has analogous acoustic counterparts to an optical charge couple device (CCD) camera. The setup was operated in transmission mode, with a tissue sample placed between the camera and a 10-MHz illuminating transducer. A high-intensity continuous-wave US signal from a therapeutic transducer was focused inside the sample tissue. A reversible, time-dependent variation in image intensity was observed in the region of the therapeutic sonications in all tissues tested: bovine fat and porcine and rabbit livers. Correlations between image intensities and temperatures were shown; rabbit liver resulted in a correlation coefficient (R(2)) of 0.6694 and bovine fat resulted in an R(2) of 0.9455. When temperatures high enough to coagulate tissue were reached, permanent changes in the images were observed. Lesion locations and dimensions from the images were found to be comparable to the sectioned tissue samples. An R(2) of 0.919 resulted when lesion size detected from the camera was compared to the actual lesion size. Preliminary results may indicate that the camera has an application for monitoring thermal surgery.

Animals↗
PubMed2000

Gigantic optical nonlinearity in one-dimensional Mott-Hubbard insulators

The realization of all-optical switching, modulating and computing devices is an important goal in modern optical technology. Nonlinear optical materials with large third-order nonlinear susceptibilities (chi(3)) are indispensable for such devices, because the magnitude of this quantity dominates the device performance. A key strategy in the development of new materials with large nonlinear susceptibilities is the exploration of quasi-one-dimensional systems, or 'quantum wires'--the quantum confinement of electron-hole motion in one-dimensional space can enhance chi(3). Two types of chemically synthesized quantum wires have been extensively studied: the band insulators of silicon polymers, and Peierls insulators of pi-conjugated polymers and platinum halides. In these systems, chi(3) values of 10(-12) to 10(-7) e.s.u. (electrostatic system of units) have been reported. Here we demonstrate an anomalous enhancement of the third-order nonlinear susceptibility in a different category of quantum wires: one-dimensional Mott insulators of 3d transition-metal oxides and halides. By analysing the electroreflectance spectra of these compounds, we measure chi(3) values in the range 10(-8) to 10(-5) e.s.u. The anomalous enhancement results from a large dipole moment between the lowest two excited states of these systems.

Journal Article↗
PubMed2001

The optical stretcher: a novel laser tool to micromanipulate cells.

When a dielectric object is placed between two opposed, nonfocused laser beams, the total force acting on the object is zero but the surface forces are additive, thus leading to a stretching of the object along the axis of the beams. Using this principle, we have constructed a device, called an optical stretcher, that can be used to measure the viscoelastic properties of dielectric materials, including biologic materials such as cells, with the sensitivity necessary to distinguish even between different individual cytoskeletal phenotypes. We have successfully used the optical stretcher to deform human erythrocytes and mouse fibroblasts. In the optical stretcher, no focusing is required, thus radiation damage is minimized and the surface forces are not limited by the light power. The magnitude of the deforming forces in the optical stretcher thus bridges the gap between optical tweezers and atomic force microscopy for the study of biologic materials.

3T3 Cells↗
PubMed1997

Towards amperometric immunosensor devices.

In contrast to optical immunosensors, the electrochemical detection of an immunanalytical reaction does require a labeling, but allows an easier discrimination of specific and non-specific binding. We present a concept and first results for a multivalent amperometric immunosensor system which is based on silicon technology. The capture molecule streptavidin, covalently immobilized on silica, allows the immobilization of biotinylated antigens at a defined density. A nanostructured gold electrode serving as a stable network of nanowires is expected to be beneficial for the electrochemical detection of bound ferrocene-labeled antibody molecules. The results presented focus on site-specific immobilization of streptavidin on silica and reduction of non-specific binding of proteins.

Bacterial Proteins↗
PubMed2005

Polaron delocalization in ladder macromolecular systems.

Organic macromolecules with conjugated building blocks have been the focus of extensive research that is motivated, in part, by the potential to create optical and electronic devices. We have shown that palladium-catalyzed amination can assemble triarylamine ladder materials with extended structures. Two ladder macromolecules have been prepared in high yields by a series of twelve or sixteen C-N coupling reactions. Studies of the electronic and optical properties of neutral and oxidized forms of the ladder structures were conducted. The optical and electronic properties of the ladder systems are compared to those of the linear tetra-phenyl-p-phenylenediamine as well as the tetra-p-anisyl-p-tetraazacyclophane. The electrochemistry of the ladder systems consists of a multiwave voltammogram with a relatively low first oxidation potential. Electron paramagnetic resonance spectroscopy of the ladder systems suggests the presence of a large density of delocalized polarons. Linear absorption measurements of the chemically oxidized ladders revealed both polaron and intervalence absorption bands. Steady-state and time-resolved fluorescence measurements were also carried out to characterize the dynamics in these novel systems.

Amines↗
PubMedDate not supplied

[CAD/CAM technology-elaboration of electronic model through optical impression in the fabrication of the dental prostheses by a computer assisted device].

In modern CAD/CAM technology of dental prosthetics, the "optical impression" taken by special video cameras deploying 3D-recording of the oral situation (Cerec 1, Cerec 2) initiates the computer-generated production of a digital model. The computer receives and renders the digital data obtained through "optical impression" i.e. data acquisition not as a "negative" of the oral situation but as a "positive" copy of it, namely as a digital model in a virtual environment which can be displayed on the screen and be further used in the fabrication of dental prostheses by means of a computer-assisted device (CAM or CIM).

Computer-Aided Design↗
PubMed2004

Formation of Langmuir layers and surface modification using new upper-rim fully tethered bipyridinyl or bithiazolyl cyclodextrins and their fluorescent metal complexes.

Seven new amphiphilic cyclodextrins bearing bipyridyl or bithiazolyl moieties at the narrow rim and free hydroxyl or methoxyl groups at the wide rim of the cyclooctaamylose crown were synthesized using a one step "phosphine imide" approach. These ligands form metal complexes that have fluorescence properties with potentials for optical applications. Here, the cyclodextrin derivatives were used as probes for evaluating the role of different moieties in the self-assembly process, providing crucial information in creating functional devices. The behavior of these molecules and of complexes with EuIII in some cases was studied in Langmuir films using surface pressure (pi) and surface potential (deltaV) measurements performed as a function of film compression (compression isotherms). For chosen cyclodextrins, Brewster angle microscopy (BAM) in monolayers was performed. Films formed with derivatives 1, 3, 7, and 2compl were transferred on mica using the Langmuir-Blodgett technique. The properties of the films deposited on mica were analyzed with fluorimetry and, in the case of derivative 7, using fringe of equal chromatic order technique (FECO). The monolayer structure and the fluorescence properties of the Langmuir-Blodgett films indicate that the derivatives studied can be used for preparing cyclodextrin-based optical devices.

Cyclodextrins↗
PubMed2005

Use of real-time magnetic resonance image guidance in endoscopic sinus surgery.

We evaluated the effectiveness of magnetic resonance image (MRI) guidance using an optical tracking system (MRI-guided therapy: MRT) in performing endoscopic sinus surgery (ESS). The profiles of the fourteen patients in the present study were as follows: eleven with mucocele in the paranasal sinus, one with recurrent chronic sinusitis, one with maxillary cancer, and one with Graves' ophthalmopathy. Preparation of the MRT system required an additional 54 min in cases involving general anesthesia, and an additional 17 min in cases involving local anesthesia, in comparison with corresponding control groups undergoing ESS in a traditional operating room. We developed nonmetal probes that were visualized in a real-time mode and assistive devices for the optical tracking system that were equipped to avoid obstruction caused by surgical instruments as well as by the hands of surgeons. Using these unique devices, anatomic landmarks were visualized using the present MRT system. The prognosis of patients was favorable, and in particular, no patients with sinus mucocele showed a recurrence of their lesions. We concluded that the MRT system used here for performing ESS was beneficial, especially in terms of the intranasal marsupialization of sinus mucoceles and for the verification of orbital contents.

Journal Article↗