Characteristics Of Light Source Research Articles

Single photon ionization (SPI) via incoherent VUV-excimer light: robust and compact time-of-flight mass spectrometer for on-line, real-time process gas analysis.

Fast on-line detection of organic compounds from complex mixtures, such as industrial process gas streams, require selective and sensitive analytical methods. One feasible approach for this purpose is the use of mass spectrometry (MS) with a selective and soft (fragment-free) ionization technique, such as chemical ionization (CI) or photo ionization (PI). Single photon ionization (SPI) with vacuum ultraviolet (VUV) light is a particularly sof tionization technique, well-suited for detection of both aromatic and aliphatic species. Problematic, however, is the generation of the VUV light. In general, the vacuum ultraviolet (VUV) light sources for SPI-MS are based either on lasers (e.g., 118-nm radiation generated by frequency-tripling of the third harmonic of a Nd:YAG laser) or on conventional VUV lamps, such as deuterium lamps. Althoughthe laser-based techniques are very sophisticated and expensive, the conventional lamps have serious drawbacks regarding their optical parameters, such as low-output power, low spectral power density, and broad emission bands. In this work, a novel excimer VUV light source, in which an electron beam is used to form rare gas excimer species, is used. The excimer VUV light sourceproduces brilliant and intense VUV light. The novel VUV light source was coupled to a compact and mobile time-of-flight mass spectrometer (TOFMS). A special interface design, including optical (VUV optics) as well as electronic measures (e.g., pulsed ion extraction) was realized. The use of the excimer VUV lamp for SPI will allow the realization of very compact, rugged, and sensitive SPI-TOFMS devices, which preferably will be adapted for process analytical application or monitoring issues (e.g., chemical warfare detection). The excimer VUV-lamp technology delivers VUV light with a good beam quality and high-output power at low costs. Furthermore, it allows changing the emitted wavelength as well as the bandwidth of the excimer VUV lamp in t he 100-200-nm region by changing the gas filling. Consequently, SPI-TOFMS with an excimer light source is a fast detection technique that can be used for online monitoring, for example, in environmental studies or industrial manufacturing processes. In this paper, technology and characteristics of the new excimer light source, as well as the combination with the TOFMS, are presented. Furthermore, a first characterization of the SPI-TOFMS instrument, regarding analytical parameters such as detection limits and selectivity, is given. This includes a discussion of potential improvements that probably will be achievable within a future prototype genertation. Finally, first applications of the system for on-line measurement of organic trace species in a complex gas mixture (here, motorcycle exhaust gas) are presented.

Application of different light sources for polymerization of restorative resins

The aim of this work was the introduction of the basic characteristics of contemporary polymerization light sources for composite resin curing. Two basic groups of available curing technologies are introduced. First are those that produce white light (conventional halogen lamps and plasma arc polymerization units). The second group comprises "blue light" curing devices that produce blue light at the origin of the light source. Lights belonging to this group include the blue LEDs and argon laser. Information about main characteristics of light sources (irradiance, wavelength range) and their proper choice could have a significant impact on polymerization quality and on long-life of composite restoration.

Spectral characteristics of light sources for S-cone stimulation.

Electrophysiological investigations of the short-wavelength sensitive pathway of the human eye require the use of a suitable light source as a S-cone stimulator. Different light sources with their spectral distribution properties were investigated and compared with the ideal S-cone stimulator. First, the theoretical background of the calculation of relative cone energy absorption from the spectral distribution function of the light source is summarized. From the results of the calculation, the photometric properties of the ideal S-cone stimulator will be derived. The calculation procedure was applied to virtual light sources (computer generated spectral distribution functions with different medium wavelengths and spectrum widths) and to real light sources (blue and green light emitting diodes, blue phosphor of CRT-monitor, multimedia projector, LCD monitor and notebook display). The calculated relative cone absorbencies are compared to the conditions of an ideal S-cone stimulator. Monochromatic light sources with wavelengths of less than 456 nm are close to the conditions of an ideal S-cone stimulator. Spectrum widths up to 21 nm do not affect the S-cone activation significantly (S-cone activation change < 0.2%). Blue light emitting diodes with peak wavelength at 448 nm and spectrum bandwidth of 25 nm are very useful for S-cone stimulation (S-cone activation approximately 95%). A suitable display for S-cone stimulation is the Trinitron computer monitor (S-cone activation approximately 87%). The multimedia projector has a S-cone activation up to 91%, but their spectral distribution properties depends on the selected intensity. LCD monitor and notebook displays have a lower S-cone activation (< or = 74%). Carefully selecting the blue light source for S-cone stimulation can reduce the unwanted L-and M-cone activation down to 4% for M-cones and 1.5% for L-cones.

Tolerancing of polarization losses in free-space optical interconnects

A study of polarization losses in free-space optical interconnects is presented. A generic method is used for the prediction of optical power losses originating from fabrication errors in the polarization characteristics of components or light sources in free-space optical systems. The impact of polarization errors is evaluated on an individual level by a sensitivity analysis and on a system level by a Monte-Carlo analysis. The method is demonstrated by application to an optical interconnect example and validated by comparison with experimental results. The simultaneous interaction of multiple tolerance parameters (commonly known as "tolerance stackup") is shown to have a significant impact on polarization losses.

Light measurements of high-luminance LEDs

The achievements of modern optoelectronics have resulted in the widespread use of light-emitting diodes (LEDs) in products designed to visualize information, especially in light devices for use in road-safety systems. These developments highlight the importance of metrological support for measurements of the photometric characteristics of semiconductor light sources. A standard light-source model based on Corvette Light Corporation high-luminance LEDs has been created and studied. The high-luminance LEDs were manufactured to a unique design using planar technology. The results of the study demonstrate the stability of the metrological characteristics of the LED-based standard source.

A study on background subtraction in Auger and photoelectron time coincidence spectroscopy using third generation synchrotron radiation source

Auger and photoelectron time coincidence spectroscopy measurements on Si(100) have been carried out employing third generation synchrotron radiation source. This work has been focused on the particular treatment of the collected data required for this kind of experiment. The time structure characteristics of the European Synchrotron Radiation Facility light source have been taken into account in time coincidence data analysis, and compared with other sources. This study has shown the particular influence of the source in the distribution of accidental coincident events, revealing the need to introduce a suitable method for background subtraction in coincidence spectra.

高周波放電を用いた無電極光源の発光特性

高周波放電を用いた無電極光源の発光特性

Standard Transport Channels of X-ray Beamlines at SPring-8

SPring-8 is constructing most of its beamlines using a combination of standardized components. The structures of the beamlines are also standardized according to the light-source characteristics. Specifications of components as well as the unified method of assembly and alignment are described.

Predicting optical densitometer response as a function of light source characteristics for radiochromic film dosimetry.

Various forms of GAFChromic (GC) film have been used for several years as radiographic media for measuring dose distributions of brachytherapy sources and small radiation fields. In order to optimize the measurement sensitivity and thus improve precision, we describe a method to calculate the dose response curves (net optical density at a give wavelength or spectrum versus absorbed dose) for different densitometer light sources using measured GC film absorption spectra. Comparison with measurements on the latest version of GC film (model MD-55-2) using four types of densitometers [He-Ne laser, broadband (white light) densitometer, and two LED (red-light) filtered densitometers] confirm the accuracy of this predictive model. The linearity and sensitivity of the dose response curves are found to be highly dependent on the light source spectrum. Initial slope is a function of the average weighted absorbance. Early saturation and decreased linearity of the dose response curves are ascribed to the nonuniform transmission of the light source through the GC film. We found that an LED (red-light) source with a narrow bandpass filter centered at 671 nm near the major absorption peak achieves nearly the maximum possible sensitivity (almost four times more sensitive than He-Ne laser, 632.8 nm) and may be suitable for in vivo dosimetry.

Future evolution of fiber optic gyros

Recent research on future evolution of fiber optic gyros is discussed. Research factors to improve the functions of interferometer fiber optic gyros in regard to light-source characteristics, temperature change induced drift, and cost reduction are reviewed, and resonator fiber optic gyros and Brillouin fiber optic gyros are evaluated as next generation configurations.

Elucidation of spectral emission characteristics of medical endoscopic light sources

Elucidation of spectral emission characteristics of medical endoscopic light sources

Effect of oxygen addition to an argon glow-discharge plasma source in atomic emission spectrometry

Small amounts of oxygen gas greatly change the characteristics of the argon plasma light source in glow-discharge emission spectrometry. The influence of oxygen addition on the sputtering rate and the excitation of the analytes in the argon plasma was investigated by employing argon-oxygen binary mixed gases having well-defined compositions. Strong quenching by oxygen was observed from the intensity of the emission lines originating from the analyte element as well as the gas species. The negative effect caused by oxygen gas in analytical applications with the glow-discharge lamp should be noted.

Intensity and spectral emission as factors affecting the efficacy of an insect electrocutor trap towards the house‐fly

AbstractCompetitive tests were used to determine how the quantitative and spectral characteristics of an electrocutor trap light source affected the attraction of the house‐fly, Musca domestica L. It was found that an increase in the radiant flux (Fe) of the trap lamps due to an increase in radiant area (A), caused a much larger increase in catch than if radiant flux was increased through higher radiant emittance (Me). The results from electroretinograms recorded in response to different levels of Me were consistent with the idea that at a given wavelength the attractiveness of a lamp is attributable to the quantitative output perceived by the fly. Of nine fluorescent lamps, the most attractive had peak emission at 340 nm. A blue lamp (peak emission 419 nm) attracted less than a third as many flies as the UV emitting lamps, and a white lamp (peak emission 585 nm) attracted fewer than a quarter as many. The corresponding photoreceptor responses were measured using the electroretinogram. At wavelengths above 400 nm the attractiveness of a lamp to a fly appears to be lower relatively than the photoreceptor response. Within the ultraviolet region (300 nm–400 nm) attractiveness is again attributable to the quantitative output perceived by the fly. It is concluded that there is a genuine behavioural preference for lamp emissions in the ultraviolet region.

Chirping compensation using a two-section semiconductor laser amplifier

Compensation of light source chirping and optical fiber dispersion using semiconductor laser amplifiers (SLAs) is investigated using a modeling equation that describes the opposite phase characteristics of light sources to SLAs with self phase modulation. A two-section SLA was fabricated in order to achieve an amplifier with both high gain and phase compensation properties. Preliminary experimental results are presented, confirming the theoretically derived phase compensation effect. >

Design and simulation of opera lighting and projection effects

A major problem challenging opera designers is the inability to co-ordinate lighting, projection systems, and set designs in the preliminary planning phase. New computer graphics techniques, which provide the set and lighting designer the opportunity to evaluate, test, and control opera designs prior to the construction of full scale systems are presented. These techniques---light source input, simulation of directional lighting, modeling of scenic projection systems, and full three-dimensional simulation---show the potential for the use of computer graphics in theater design.The light source input component consists of a program for assigning light source attributes with a set of theater lighting icons. This module allows a designer to specify light source characteristics in a way familiar to the discipline and to make preliminary evaluations of the lighting conditions.An extended progressive radiosity method is introduced to simulate the directional lighting characteristics which are specified by the input program.A new projection approach is presented to simulate the optical effects of scenic projectors. In addition, a solution to the distortion problem produced by angular projections is described.The above components are integrated to produce full three-dimensional simulations of the global illumination effects in an opera scene.

X-UV Absorption Spectroscopy with Laser-Produced Plasmas: A Review

Exteme-ultraviolet (X-UV) absorption spectroscopy has gained impetus in recent years, spurred on by a growing interest in the physics of core excited atomic, molecular and solid species. Progress in this field has been helped in no small measure by developments in X-UV light sources. One such source is the laser-produced plasma which, by suitable choice of target material, can be used to produce a clean, line free continuum virtually throughout the X-UV and V-UV spectral regions from 40-2000 Å. We briefly address here the issues surrounding the origin and characteristics of laser-plasma continuum light sources. In addition we review progress to date on the application of these sources to the study of the X-UV photoabsorption spectra of atoms, ions and molecules.

美術館・博物館用光源の種類と特性

美術館・博物館用光源の種類と特性

The effect of walls on colour rendering

Colour rendering indices are characteristics of light sources, but nothing is said about the influence of the room where they are used. The walls' effect is analysed using the parametric approach of colour rendering. This formulation affords the possibility to classify the spectral reflection factors. Particularly green and red colours tend to change colour rendering more than blue or yellow ones do. The walls' effect really exists as it is shown in two examples. If it is unwanted, a method is proposed to avoid it by changing the light source or the colour of the walls.

A Comprehensive Light-Source Description for Computer Graphics

For realistic simulation, light source descriptions require definitions of the geometry, the spectral distribution, and the spatial distribution of the luminous intensity. A procedure is described in which these light source characteristics are defined, and the resultant intensity computations are integrated into a testbed ray-tracing system. Point, linear, and area light sources are considered. Results are shown which account for the spectral distribution and illustrate the directional dependence of the intensity calculations. The procedures are applicable to environments of unlimited complexity. Light sources can be arbitrarily placed within the environment and contained within the simulated image.

Exploiting image formation knowledge for motion analysis

Deals with scene sequences showing objects in motion. Gray values of an object surface element, traced through the sequence, will exhibit systematic variations due to changing lighting and viewing conditions. Much of today's understanding of the underlying image formation process is due to Horn, who showed in particular that given sufficient knowledge about imaging conditions, gray values may be used to infer object shape. Assuming certain idealized but unknown object surface properties and light source characteristics it is shown that in general rotation angle increments and projected object surface angles but no absolute angle values may be computed from the observed data. Given additional knowledge about unknown illumination parameters, however, object shape may be determined.