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Results for “Optical Devices”

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At least 775 records · Page 43Linked to original sources
PubMed1997

A head motion measurement system suitable for emission computed tomography.

Subject motion during brain imaging studies can adversely affect the images through loss of resolution and other artifacts related to movement. We have developed and tested a device to measure head motion externally in real-time during emission computed tomographic (ECT) brain imaging studies, to be used eventually to correct ECT data for that motion. The system is based on optical triangulation of three miniature lights affixed to the patient's head and viewed by two position-sensitive detectors. The computer-controlled device converts the three sets of lamp positions into rotational and translational coordinates every 0.7 seconds. When compared against a mechanical test fixture, the optical system was found to be linear and accurate with minimal crosstalk between the coordinates. In a study of two subjects, comparing the angular motions measured by the optical device and a commercially available electromagnetic motion detector, the two systems agreed well, with an root mean square (rms) difference of less than 0.6 degree for all rotations.

Algorithms↗
PubMed2007

Electrically tunable Bragg gratings in single-mode polymer optical fiber.

We present what is to our knowledge the first demonstration of a tunable fiber Bragg grating device in polymer optical fiber that utilizes a thin-film resistive heater deposited on the surface of the fiber. The polymer fiber was coated via photochemical deposition of a Pd/Cu metallic layer with a procedure induced by vacuum-ultraviolet radiation at room temperature. The resulting device, when wavelength tuned via joule heating, underwent a wavelength shift of 2 nm for a moderate input power of 160 mW, a wavelength to input power coefficient of -13.4 pm/mW, and a time constant of 1.7 s(-1).

Journal Article↗
PubMed2001

Aligned microcontact printing of biomolecules on microelectronic device surfaces.

Microcontact printing (muCP) of extracellular matrix proteins is a fascinating approach to control cell positioning and outgrowth, which is essential in the development of applications ranging from cellular biosensors to tissue engineering. Microelectronic devices can be used to detect the activity from a large number of recording sites over the long term. However, signals from cells can only be recorded at small sensitive spots. In this paper, we present an innovative setup to perform aligned muCP of extracellular matrix proteins on microelectronic devices in order to guide the growth of electrogenic cells specifically to these sensitive spots. Our system is based on the combination of a fine-placer with redesigned micro stamps having a rigid glass cylinder as backbone for attachment in the alignment tool. Alignment is performed moving the device with an optical table under microscopic control of the superimposed images from stamp and device surface. After successful alignment, the stamp is brought into contact with the device surface by means of a high-precision lever. With our setup, we were able to pattern up to 40 devices per hour. A lateral alignment accuracy of < 2microm has been achieved. Aligned neuronal growth on patterned devices was demonstrated with dissociated hippocampal neurons.

Animals↗
PubMed1992

Sens-A-Ray. A new system for direct digital intraoral radiography.

A new system for direct digital intraoral radiography, Sens-A-Ray, is presented. This system is based on a detector with a charge-coupled device that was designed especially for direct exposure to x-ray radiation. The system also includes interface electronics and an IBM AT-compatible personal computer with a digital I/O with frame memory, a super VGA graphics board, a high-resolution monitor, and software for the exposure, capture, storage, and enhancement of images. An external optical mass storage device is used for permanent storage of images in digital format. A video printer may be used to create hard copies. The system produces radiographic images at a significantly lower exposure than required for E-speed intraoral film. Applications of the system are exemplified, and its basic properties are discussed.

Computer Graphics↗
PubMed1987

Optical biosensors for immunoassays: the fluorescence capillary-fill device.

This paper reports, for the first time, details of a novel type of optical biosensor for immunoassays, the fluorescence capillary-fill device (FCFD). This is based on a straightforward adaptation of the technology used to mass manufacture liquid-crystal display (LCD) cells to give cheap disposable immunosensors. These merely require contact by the sample to give a result in about a minute, and use certain principles of optical fibres and waveguides to avoid the need for operator attention, for physical separation methods or for washing steps. After a very brief introductory review and classification of optical biosensors, the main features of the FCFD and its associated instrumentation are described. The optical characteristics of the FCFD are then described, followed by accounts of the immunoassay method, the measurement system used in the experiments, the fabrication of FCFD sensors and a detailed description of the design of a competitive immunoassay for human immunoglobulin G (hIgG). The experimental details and the results of a first attempt at such an assay are then presented and discussed. It is concluded that the demonstration of this assay is a significant achievement, because the format of the FCFD, its manufacturing process and its instrumentation are completely novel. Certain problem areas have been identified and quantified; intended further work on these is outlined.

Animals↗
PubMed2004

Production and characterization of spiral phase plates for optical wavelengths.

We describe the fabrication and characterization of a high-quality spiral phase plate as a device to generate optical vortices of low (3-5) specified charge at visible wavelengths. The manufacturing process is based on a molding technique and allows for the production of high-precision, smooth spiral phase plates as well as for their replication. An attractive feature of this process is that it permits the fabrication of nominally identical spiral phase plates made from different materials and thus yielding different vortex charges. When such a plate is inserted in the waist of a fundamental Gaussian beam, the resultant far-field intensity profile shows a rich vortex structure, in excellent agreement with diffraction calculations based on ideal spiral phase plates. Using a simple optical test, we show that the reproducibility of the manufacturing process is excellent.

Journal Article↗
PubMed1998

Applications of Ion Microscopy and In Situ Electron Microscopy to the Study of Electronic Materials and Devices.

: We discuss the application of ion microscopy and in situ electron microscopy to the study of electronic and optical materials and devices. We demonstrate how the combination of in situ transmission electron microscopy and focused ion beam microscopy provides new avenues for the study for such structures, enabling extension of these techniques to the study of dopant distributions, nanoscale stresses, three-dimensional structural and chemical reconstruction, and real-time evolution of defect microstructure. We also discuss in situ applications of thermal, mechanical, electrical, and optical stresses during transmission electron microscopy imaging.

Journal Article↗
PubMed2005

Single cell manipulation, analytics, and label-free protein detection in microfluidic devices for systems nanobiology.

Single cell analytics for proteomic analysis is considered a key method in the framework of systems nanobiology which allows a novel proteomics without being subjected to ensemble-averaging, cell-cycle, or cell-population effects. We are currently developing a single cell analytical method for protein fingerprinting combining a structured microfluidic device with latest optical laser technology for single cell manipulation (trapping and steering), free-solution electrophoretical protein separation, and (label-free) protein detection. In this paper we report on first results of this novel analytical device focusing on three main issues. First, single biological cells were trapped, injected, steered, and deposited by means of optical tweezers in a poly(dimethylsiloxane) microfluidic device and consecutively lysed with SDS at a predefined position. Second, separation and detection of fluorescent dyes, amino acids, and proteins were achieved with LIF detection in the visible (VIS) (488 nm) as well as in the deep UV (266 nm) spectral range for label-free, native protein detection. Minute concentrations of 100 fM injected fluorescein could be detected in the VIS and a first protein separation and label-free detection could be achieved in the UV spectral range. Third, first analytical experiments with single Sf9 insect cells (Spodoptera frugiperda) in a tailored microfluidic device exhibiting distinct electropherograms of a green fluorescent protein-construct proved the validity of the concept. Thus, the presented microfluidic concept allows novel and fascinating single cell experiments for systems nanobiology in the future.

Animals↗
PubMedDate not supplied

The challenge of quality assurance for emission flux measurements of large area sources by optical remote sensing.

Monitoring the emissions flux of contaminant gases from large area sources requires measurement of concentrations from an optical remote sensing device and reconstruction of the plume. Path integrated concentrations are determined using multiple optical beam paths. The spatial distribution of concentrations is generated for a plane perpendicular to the direction of the wind. Estimates of the emission flux are determined by integrating the product of the calculated concentrations and wind speeds over the plane. No standard method exists for the complete process, defensible estimates of the uncertainty of the final emission flux have not yet been developed, and a data validation procedure is needed. Auditors are challenged to configure an adequate performance evaluation standard that is representative of a large area source.

Air Pollutants↗
PubMed2005

Optical properties of low band gap alternating copolyfluorenes for photovoltaic devices.

In a joint experimental and theoretical work the optical response and excited-state character of two novel conjugated polymers for photovoltaic applications are studied. The polymers, alternating polyfluorene (APFO) Green 1 and APFO Green 2, are both copolymers of fluorene, thiophene, and electron accepting groups. The band gaps are extended into the red and near infrared with onsets of 780 and 1000 nm, respectively, due to alternating donor and acceptor moieties along the polymer chain. Spectroscopic ellipsometry and subsequent modeling made it possible to extract the dielectric function in the range of 260-1200 nm. Semiempirical quantum chemical calculations (ZINDO) revealed the character of the main electronic transitions in the studied spectral region. The spectral band just above 400 nm was assigned to a delocalized pi-pi* transition for both polymers. The red band lying at 622 and 767 nm in the two polymers corresponds to an electronic state mainly occupying the acceptor units and having a strong charge-transfer character. We show that the ZINDO transition energies are valuable input to the application of Lorentz oscillators in modeling of the dielectric function of the polymer material.

Caprylates↗
PubMed2000

Macular pigment optical density measurement: a novel compact instrument.

A compact device to derive the optical density of human macular pigment (MP) using heterochromatic flicker photometry is described. The validity of the system is assessed by measuring the optical density spectra of MP in 12 healthy subjects and comparing this with well-established previously published values. The mean spectral absorbance characteristics of MP across subjects corresponds well with accepted values. As reported in other studies, our measurements show a wide variation of MP optical densities between individuals. In our technique within-subject variability is low; standard deviations are between 0.025 and 0.15 in most cases. The overall optical density of MP ranged from 0.08 to 0.84 with a mean of 0.496 and standard deviation of 0.257 at 460 nm. The stimulus size was 0.95 degrees. The unique feature of the technique is that it allows free viewing (not Maxwellian View) of the stimulus, it can be conducted easily and quickly and does not need frequent re-calibration.

Humans↗