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Results for “Optical Devices”

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At least 541 records · Page 30Linked to original sources
PubMed1999

Optical processing architecture and its potential application for digital and analog radiography.

In this report we introduce the fundamental architectures and the potential applications of optical processing techniques in medical imaging. Three basic optical processing architectures were investigated for digital and analog radiography. The processors consist of a module that converts either the analog or the digital radiograph into a coherent light distribution; a coherent optical processing architecture that performs various mathematical operations; a programmable digital-optical interface and other accessories. Optical frequency filters were implemented for mammographic and other clinical feature enhancement. In medical image processing, digital computers offer the advantages of programmability and flexibility. In contrast, optical processors perform parallel image processing with high speed. Optical processors also offer analog nature, compact size, and cost effectiveness. With technical advances of digital-optical interface devices, the medical image processor, in the foreseeable future, may be a hybrid device, namely, a programmable optical architecture.

Equipment Design↗
PubMed2005

Optical phased-array beam steering controlled by wavelength.

A scheme for optical phased-array beam steering controlled by wavelength is proposed. In this scheme, the optical scanning device consists of arrayed optical waveguides with specific length differences, by which the desired phase slope that results in optical beam steering is formed at the ends of the waveguides and can be changed by varying the optical wavelength. By introducing the concept of irregularly spaced arrays, sidelobes can be dramatically suppressed regardless of large center-to-center interelement spacing. The absolute phase difference between adjacent elements plays a vital role in optical beam steering, and the relation between the nonuniform length difference and the corresponding center-to-center spacing among elements is found.

Journal Article↗
PubMed2002

Polynomial-based optical true-time delay devices with microelectromechanical mirror arrays.

We previously reported optical true-time delay devices, based on the White cell, to support phased-array radars. In particular, we demonstrated a quadratic device, in which the number of delays obtainable was proportional to the square of the number of times the light beam bounced in the cell. Here we consider the possibilities when a microelectromechanical (MEM) tip/tilt mirror array with multiple stable states is used. We present and compare designs for quadratic, quartic, and octic cells using MEM mirror arrays with two, three, and five micro-mirror tilt angles. An octic cell with a three-state MEM can produce 6,339 different delays in just 17 bounces.

Journal Article↗
PubMed2000

[Initial experiences with a new optical target system (SimpliCT) for CT-guided punctures].

PURPOSE: To evaluate the prototype of a new optical target device for CT-guided punctures and interventions. METHODS: An optical target device for CT-guided punctures was applied in 24 interventions. The system consists of a laser target device mounted on a stand. The biopsy needle is adjusted according the course of a laser beam. The target angle has to be adjusted on the laser unit. The laser carrier can be moved along an 90 degrees-angled rail, allowing punctures from any angle in plane. Furthermore, angulation in the z-plane is possible, supporting interventions with gantry tilt. Size and depth of the target lesions, the planned and the actual angle of the inserted needle, the numbers of corrections of the needle position, and the time required for the puncture were evaluated. The user rated the benefit of the system and the ease of the application. RESULTS: All 24 interventions were carried out successfully. The mean difference between the planned and the actual angle of the needle was 1.3 degrees (SD: 0.7 degree). The system was considered as easy to handle and as a valuable aid. CONCLUSIONS: The laser target device is a simple navigation system which allows accurate positioning of a needle. Requiring an acceptable low preparation time, it easily can be integrated into the procedure.

Adult↗
PubMedDate not supplied

Low power lasers in physical therapy: measurement of optical output power of devices.

This report outlines the most essential characteristics of low power lasers commonly used in physical medicine. The optical output power of two Helium-Neon (HeNe) lasers (CW scanner) and two collimated Infrared (IR) laser diodes was measured with a CoherentR Model 212 meter designed to measure output power and its power density. The energy of two collimated IR lasers was measured with a Laser Precision Energy Meter equipped with an RJP-735 probe. The difficulties arising from the large divergence of the laser beam in diode lasers and the importance of the scattering and absorption of laser beams are discussed. The criteria for the evaluation of the lasers as well as the essential parameters for an adequate characterization of laser therapy are given.

Aluminum↗
PubMed2005

Infrared thermography to mass-screen suspected SARS patients with fever.

Fever greater than 38 degrees C is a cardinal sign of patients with the severe acute respiratory syndromes (SARS). To reduce the risk of nosocomial cross infections, screening all patients and visitors who visit hospitals and clinics for fever at the entrance of every hospital building has become a standard protocol in Taiwan during the SARS epidemic from mid-April to mid-June 2003. We used a digital infrared thermal imaging (DITI) system (Telesis Spectrum 9000 MB) to conduct mass screening of patients and visitors who entered the hospital to identify those with fever. The DITI system has two components: a sensor head and a PC imaging workstation. The sensor head is an optic-mechanical device which consists of imagining optics for focusing the infrared source information on the infrared detector. The infrared images are further converted into electrical signals, which are then processed for real-time display on the monitor. During the period from April 13 to May 12 2003, 72,327 outpatients and visitors entered Taipei Medical University-Wan Fang Hospital, Taipei, Taiwan. A total of 305 febrile patients (0.42%) was detected by infrared thermography. Among them, three probable SARS patients were identified after thorough studies including contact history, laboratory tests and radiology examinations. The findings suggests that infrared thermography was an effective and reliable tool ideal for mass-screening patients with fever in the initial phase of screening for SARS patients at a busy hospital which sees approximately 3,000 outpatients every weekday during the SARS epidemic.

Cross Infection↗
PubMed1994

Assessment of chewing efficiency: a comparison of particle size distribution determined using optical scanning and sieving of almonds.

Particle sizes obtained with progressive chewing cycles were quantified by use of an optical scanning device and compared with the sieving method. The aim of this study was to validate the optical method by comparison with sieving using a natural test food, almond. Masticatory efficiency was assessed in six dentate subjects. The almonds were chewed for 1, 4, 8, 16 and 32 chewing strokes. Each experiment was replicated. The chewed material was sieved through a 1 mm aperture sieve on a Büchner funnel and dried after washing with water and 100% alcohol. The dried particles were weighed and scanned by an optical scanning device for number and size. The same samples were sieved and weighed with a conventional sieve method. The results of both methods were described by particle size distributions based on the volume of particles. The results derived from the optical scanning and sieving showed similarity. It can be concluded that the optical method is simple to use, faster than sieving and needs little skill in the use of equipment. The comparison of the results validates both methods.

Adult↗
PubMed2004

Prototype CO2 laser-induced long-period fiber grating variable optical attenuators and optical tunable filters.

Prototype devices capable of variable attenuation at a fixed wavelength, wavelength tuning at a constant attenuation, and combinations of these spectral characteristics are demonstrated in CO2 laser-induced long-period fiber gratings (LPFGs). These devices are based on controlled flexure by means of a piezoceramic platform. CO2 laser-induced LPFG characteristics along with the fabrication and testing processes of these gratings are discussed. Devices with a optical attenuation of 13 dB and a wavelength tuning of 7 nm are reported.

Journal Article↗
PubMed2003

Optical microcavities.

Optical microcavities confine light to small volumes by resonant recirculation. Devices based on optical microcavities are already indispensable for a wide range of applications and studies. For example, microcavities made of active III-V semiconductor materials control laser emission spectra to enable long-distance transmission of data over optical fibres; they also ensure narrow spot-size laser read/write beams in CD and DVD players. In quantum optical devices, microcavities can coax atoms or quantum dots to emit spontaneous photons in a desired direction or can provide an environment where dissipative mechanisms such as spontaneous emission are overcome so that quantum entanglement of radiation and matter is possible. Applications of these remarkable devices are as diverse as their geometrical and resonant properties.

Journal Article↗
PubMed2003

Design of delay elements in a binary optical true-time-delay device that uses a White cell.

A White-cell-based binary optical true-time-delay device has two parts: the controller, or switching engine, and the delay elements. Here we discuss in detail the design of both glass blocks and lens trains as delay elements. Glass blocks can be used in our design for delays ranging from one to a few hundred picoseconds. Lens trains are suitable for longer delays. We also analyze the loss associated with each design and give design limits.

Journal Article↗
PubMed2003

Advanced optical tweezers for the study of cellular and molecular biomechanics.

Optical tweezers are an important tool for studying cellular and molecular biomechanics. We present a robust optical tweezers device with advanced features including: multiple optical traps, acousto-optic trap steering, and back focal plane interferometry position detection. We integrate these features into an upright microscope, with no compromise to its capabilities (differential interference contrast microscopy, fluorescence microscopy, etc.). Acousto-optic deflectors (AODs) steer each beam and can create multiple time-shared traps. Position detection, force calibrations and AOD performance are presented. The system can detect subnanometer displacements and forces below 0.1 pN.

Biomechanical Phenomena↗
PubMed2006

Improving the repeatability of topographic height measurements in confocal scanning laser imaging using maximum-likelihood deconvolution.

PURPOSE: To evaluate maximum likelihood (ML) blind deconvolution as a technique for improving the repeatability of topographic height measurements obtained from scanning laser tomography (Heidelberg Retinal Tomograph [HRT]; Heidelberg Engineering, Heidelberg, Germany). METHODS: ML blind deconvolution is an image-processing technique that estimates the original scene from a degraded image. This technique has been used in confocal scanning laser microscopy to remove "out-of-focus" haze in three-dimensional confocal image stacks. ML blind deconvolution requires no prior estimation of the point-spread function (PSF), as opposed to classic linear deconvolution methods. Instead, the algorithm estimates an initial PSF based on the optical setup of the confocal scanning device and optics of the eye and iteratively proceeds to a solution. The improvement in repeatability of height measurements from mean topography images within scan (intrascan) and between scans (interscan) afforded by ML deconvolution was evaluated in a test-retest series of HRT images from 40 ocular hypertensive and glaucomatous patients with varying degrees of media opacity. RESULTS: There was an improvement in intrascan repeatability in 38 out of the 40 mean topography images (median improvement 2.5 microm, inter-quartile range 2.19, P < 0.001), and an improvement in interscan repeatability in 33 of the 40 mean topographies (median improvement, 1.0 microm, interquartile range 3.49, P < 0.001). There was a positive association between the magnitude of the improvement in repeatability and the level of mean pixel height standard deviation (MPHSD), intrascan (P = 0.004) and interscan (P = 0.002). CONCLUSIONS: ML blind deconvolution algorithm improves the repeatability of topographic height measurements from the HRT. This improvement was greater in patients with poorer quality images.

Algorithms↗
PubMed2005

Fabrication of compact turning mirrors in silicon-on-insulator materials.

A turning mirror is a key component in compact optical waveguide devices and high-density integrated optics. An improved two-step method for fabrication of high-quality, compact turning mirrors in silicon-on-insulator materials is proposed. First, inductively coupled plasma etching is applied to produce the turning mirror, which keeps the turning mirror compact; then silicon wet anisotropic etching is applied to enhance the quality of the turning mirror by of its polishing surface, correcting its orientation, and improving the verticality. The shape of the turning mirror fabricated by the two-step method is hexagonal or octagonal, matching the optical field of the rib waveguide well. A large effective mirror size to reflect light waves and reduced shrinkage of the mirror size during etching guarantee that a mirror produced by this two-step method will be more compact than previously designed mirrors.

Journal Article↗
PubMed2005

In vitro measurements of optical properties of porcine brain using a novel compact device.

Knowledge of the optical properties of tissues can be applied in numerous medical and scientific fields, including cancer diagnostics and therapy. There are many different ways of determining the optical properties of turbid media. The paper describes measurements of the optical properties of porcine brain tissue using novel instrumentation for simultaneous absorption and scattering characterisation of small turbid samples. Integrating sphere measurements are widely used as a reference method for determination of the optical properties of relatively thin turbid samples. However, this technique is associated with bulky equipment, complicated measuring techniques, interference compensation techniques and inconvenient sample handling. It is believed that the sphere for some applications can be replaced by a new, compact device, called the combined angular and spatially resolved head sensor, to measure the optical properties of thin turbid samples. The results compare very well with data obtained with an integrating sphere for well-defined samples. The instrument was shown to be accurate to within 12% for microa and 1% for micro's in measurements of intralipid-ink samples. The corresponding variations of data were 17% and 2%, respectively. The reduced scattering coefficient for porcine white matter was measured to be 100 cm(-1) at 633 nm, and the value for coagulated brain tissue was 65 cm(-1). The corresponding absorption coefficients were 2 and 3 cm(-1), respectively.

Animals↗