scholarly journals Photopolymerization of dental materials: Types and characteristics of the light sources

2009 ◽  
Vol 56 (4) ◽  
pp. 207-212 ◽  
Author(s):  
Gorjana Popovic ◽  
Roze Djokic
Keyword(s):  
Absorption Spectrum ◽  
Light Source ◽  
Uv Light ◽  
Dental Materials ◽  
Life Time ◽  
Source Spectrum ◽  
Light Sources ◽  
Light Spectrum ◽  
Visible Part ◽  
Short Time

Light from the polymerization source which initiates photopolymerization in the material has its determined wavelength. Photoinitiator, such as camphorhinone, excited by light, can be activated with any of the wavelength from its absorption spectrum. To obtain successful photopolymerization, light source should emit waves of adequate wavelength; light intensity has to be optimal, to have sufficient time of exposure and material up to 2 mm thickness. Photoinitiator inside the material should match light source spectrum and work regime. Halogen lamps have wide spectra of wavelengths in the visible part of the light spectrum. Their spectra are similar to absorption spectrum of camphorhinone. Plasma (xenon) lamps emit blue light. Though their diapason is low, spectra have great intensity. Adequate diapason and easy excitation allow them to have short time of exposure. LED lamps have blue diodes as light source. They do not need filters due to narrow emission spectrum. Laser (argon) lamps are the only that emit linear spectra. Ultraviolet (mercury) lamps are not in use any more in dentistry; theirs initiators were activated by UV light. LED lamps have longer life time; do not change the spectra during time, warm less, do not need filters, allow change of the source for more powerful, more efficient and more advantageous two steps or impulse illumination mode. However, LED lamps can not be used for a material that has photoinitiator(s) activated by light with wavelength above the maximum of the LED spectra.

scholarly journals Towards the Optimum Light Source Spectrum

2010 ◽  
Vol 2010 ◽  
pp. 1-9 ◽  
Author(s):  
Andrew Chalmers ◽  
Snjezana Soltic
Keyword(s):  
Light Source ◽  
Large Scale ◽  
Source Spectrum ◽  
Light Sources ◽  
Luminous Efficacy ◽  
Light Emitting ◽  
Spectral Bands ◽  
Good Energy ◽  
Lighting Systems ◽  
Colour Rendering

This paper is concerned with designing light source spectra for optimum luminous efficacy and colour rendering. We demonstrate that it is possible to design light sources that can provide both good colour rendering and high luminous efficacy by combining the outputs of a number of narrowband spectral constituents. Also, the achievable results depend on the numbers and wavelengths of the different spectral bands utilized in the mixture. Practical realization of these concepts has been demonstrated in this pilot study which combines a number of simulations with tests using real LEDs (light emitting diodes). Such sources are capable of providing highly efficient lighting systems with good energy conservation potential. Further research is underway to investigate the practicalities of our proposals in relation to large-scale light source production.

scholarly journals Impact of different standard lighting sources on red jadeite and color quality grading

2019 ◽  
Vol 23 (4) ◽  
pp. 371-378
Author(s):  
Xin Pan ◽  
Ying Guo ◽  
Ziyuan Liu ◽  
Zikai Zhang ◽  
Yuxiang Shi
Keyword(s):  
Light Source ◽  
Color Space ◽  
Sample Surface ◽  
Color Temperature ◽  
Integrating Sphere ◽  
Light Sources ◽  
Light Spectrum ◽  
Fisher Discriminant Analysis ◽  
Fisher Discriminant ◽  
Quality Grading

The purpose of this paper is to investigate the standard light source for grading and displaying the color of red jadeite and to classify the color. With Raman spectrometer, ultraviolet-visible spectrophotometer and X-ray fluorescence spectrometer, the results show that, the Fe 3+ is the main chromogenic mineral of red jadeite, which negatively correlates with the tonal angle, while the color of red jadeite has a positive correlation with the hematite content. The color of 120 red jadeite samples was examined by collecting the reflective signaled from the sample surface using an integrating sphere with the portable X-Rite SP62 spectrophotometer based on CIE 1976 L*a*b* uniform color space. The color parameters of jadeite samples under D65, A and CWF standard light sources were analyzed. The light spectrum of D65 light source is continuous, relatively smoothed with high color temperature, which makes the sample color close to that under the natural light and can be used as the best evaluation light source. A light source contributes to improve the red tone of jadeite, which is the best light source for commercial display of red jadeite. CWF light source can be used as the auxiliary lighting for color evaluation. The color of red jadeite is divided into five levels from best to worst using K-Means cluster analysis and Fisher discriminant analysis under D65 light source: Fancy Vivid, Fancy Deep, Fancy Intense, Fancy dark and Fancy.

LRT Digest 3: New colour metrics and their use

2019 ◽  
Vol 51 (5) ◽  
pp. 657-681 ◽  
Author(s):  
PR Boyce ◽  
JR Stampfli
Keyword(s):  
Light Source ◽  
Comprehensive Approach ◽  
Source Spectrum ◽  
Light Sources ◽  
Colour Properties ◽  
Executive Summary ◽  
Colour Temperature ◽  
Test Light ◽  
High Level ◽  
Colour Rendering

Executive summary The two metrics traditionally used to quantify the colour properties of light sources are the correlated colour temperature and the CIE General Colour Rendering Index. With the arrival of LEDs as a major light source questions began to be asked about the merits of both of these metrics. The question asked about correlated colour temperature was how far should the chromaticity of a light source be allowed to depart from the Planckian locus before the light emitted could no longer be said to be white? A tolerance to such a departure ( Duv) already existed but now gathered much more attention. The questions asked about the CIE General Colour Rendering Index were more searching. The limitations of the CIE General Colour Rendering Index were explored and, as a result, several alternative approaches to quantifying the colour rendition properties of light sources were proposed. The most comprehensive approach was produced by the Illuminating Engineering Society of North America, first in its Technical Memorandum IES TM-30-15 and more recently in its revision, Technical Memorandum ANSI/IES TM-30-18, which has been accepted as an American Standard. Both these documents describe a system that contains two high-level summary metrics: One for the average fidelity, i.e. how accurately a test light source renders 99 colour samples relative to how they are rendered under a reference illuminant, and the other for the average colourfulness, i.e. the overall increase or decrease in colourfulness of the same colour samples under the same test light source compared to the same reference illuminant. Associated with these overall average metrics are a number of more detailed metrics and graphical presentations. These aim to quantify and illustrate the variations in fidelity and the direction and magnitude of the shifts in chroma and hue around the hue circle. Compared to the CIE General Colour Rendering Index or the CIE Fidelity Index, a metric published by the CIE in 2017, ANSI/IES TM-30-18 provides a more comprehensive approach to quantifying and understanding the effects of light source spectrum on the perception of colour. Unfortunately, the new colour metrics described in IES TM-30-15 and ANSI/IES TM-30-18 have not yet been accepted by the CIE. Despite this, some light source manufacturers have started to provide information on their products expressed in terms of the ANSI/IES TM-30-18 colour metrics and designers are beginning to request them. The expectation is that, eventually, the ANSI/IES TM-30-18 metrics will be adopted by many countries and authorities, because they provide a much more comprehensive description of the colour properties of a light source than the CIE General Colour Rendering Index. This will be of value to light source manufacturers and lighting designers as well as those who prepare lighting codes and guides. It is expected that in the future the minimum set of data considered acceptable for describing the colour properties of a light source are likely to be the correlated colour temperature and the associated Duv value, the CIE Fidelity Index or the matching ANSI/IES TM-30-18 Fidelity Index, together with the ANSI/IES TM-30-18 Gamut Index and the ANSI/IES TM-30-18 Colour Vector Graphic.

COLOUR FIDELITY AND ILLUMINANCE TRADE-OFF: TESTING LIGHTING VALUES

2021 ◽  
Author(s):  
J.A. Veitch ◽  
L.A. Whitehead
Keyword(s):  
Energy Efficiency ◽  
Light Source ◽  
Reflectance Spectra ◽  
Source Spectrum ◽  
Light Sources ◽  
Trade Off ◽  
Luminous Efficacy ◽  
Reading Task ◽  
Colour Appearance ◽  
Effect Of Light

The higher the colour fidelity of a light source, the lower its luminous efficacy of radiation because the light source spectrum must deviate from V(λ) to deliver the higher fidelity. Two experiments probed the trade-off between energy efficiency and colour quality. Experiment 1 required participants to simultaneously view pairs of light sources differing in colour fidelity, at either a higher (346 lx) or lower (277 lx) illuminance. Participants performed a timed reading task and judged the colour appearance of the pair. There were no effects of illuminance, but larger colour fidelity differences between the light sources in the pair correlated with lower appearance judgements. Experiment 2 simulated the effect of light sources on defined reflectance spectra. The results showed that improvements of colour fidelity above what is often considered satisfactory can yield more satisfying illumination while using the same amount of power.

scholarly journals Development of a Hg-free UV light source and its performance in photolytic and photocatalytic applications

2019 ◽  
Vol 18 (2) ◽  
pp. 328-335 ◽  
Author(s):  
Satoshi Horikoshi ◽  
Daisuke Yamamoto ◽  
Kenta Hagiwara ◽  
Akihiro Tsuchida ◽  
Isamu Matsumoto ◽  
...  
Keyword(s):  
Light Source ◽  
Uv Light ◽  
Light Sources ◽  
Photocatalytic Applications

Constraints on light sources that use mercury (arc lamps) are evolving with the establishment of the Minamata Convention, which has led to the proliferation of LEDs.

scholarly journals Performance Modeling of Ultraviolet Atmospheric Scattering of Different Light Sources Based on Monte Carlo Method

2020 ◽  
Vol 10 (10) ◽  
pp. 3564
Author(s):  
Qiushi Zhang ◽  
Xin Zhang ◽  
Lingjie Wang ◽  
Guangwei Shi ◽  
Qiang Fu ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Light Source ◽  
Ultraviolet Light ◽  
Transport Model ◽  
Uv Light ◽  
Probability Method ◽  
Light Sources ◽  
Atmospheric Transmission ◽  
Atmospheric Scattering ◽  
Near Ultraviolet

Since the atmosphere has a strong scattering effect on ultraviolet light, the transmission of non-line-of-sight (NLOS) signals can be realized in the atmosphere. In previous articles, ultraviolet (UV) light atmospheric scattering has been characterized by many scattering models based on spot light sources with uniformly distributed light intensity. In order to explore the role of light sources in atmospheric transmission, this work proposed a UV light atmospheric transport model under different types of light source, including light-emitting diode (LED), laser, and ordinary light sources, based on the Monte Carlo point probability method. The simulation of the light source in the proposed model is a departure from the use of a light source with uniform intensity distribution in previous articles. The atmospheric transmission efficiency of different light sources was calculated and compared with the data of existing models. The simulation results showed that the type of light source can significantly change the shape of the received signal and the received energy density. The Monte Carlo (MC) point probability method dramatically reduced the calculation time and the number of photons. The transmission characteristics of different ultraviolet light sources in the atmosphere provide a theoretical foundation for the design of ultraviolet detection and near-ultraviolet signal communication in the future.

Accessible, large-area, uniform dose photolithography using a moving light source

2021 ◽  
Author(s):  
Alexander Kaltashov ◽  
Prabu Karthick Parameshwar ◽  
Nicholas Lin ◽  
Christopher Moraes
Keyword(s):  
Light Source ◽  
Uv Light ◽  
Movement Pattern ◽  
Exposure Dose ◽  
Light Sources ◽  
Large Area ◽  
Domain Specific ◽  
Conventional Photolithography ◽  
Uv Lamp ◽  
Uv Dose

Abstract Photolithography is an essential microfabrication process in which ultraviolet (UV) light is projected through a mask to selectively expose and pattern a light-sensitive photoresist. Conventional photolithography devices are based on a stationary UV lamp and require carefully-designed optics to ensure that a uniform exposure dose is provided across the substrate being patterned. Access to such systems is typically limited to certain labs with domain-specific expertise and sufficient resources. The emergence of LED-based UV technologies has provided improved access to the necessary light sources, but issues with uniformity and limited exposure sizes still remain. In this work, we explore the use of a moving light source (MOLIS) for large-area lithography applications, in which the light source path speed, elevation, and movement pattern can be used to smooth out any spatial variations in source light intensity profiles, and deliver a defined and uniform cumulative UV exposure dose to a photoresist-coated substrate. By repurposing a 3D printer and UV-LED flashlight, we constructed an inexpensive MOLIS platform, simulated and verified the parameters needed to produce a uniform UV dose exposure, and demonstrate this approach for SU-8 microfabrication of features with dimensions relevant to many areas in biomedical engineering. The ready accessibility and inexpensive nature of this approach may be of considerable value to small laboratories interested in occasional and low-throughput prototype microfabrication applications.

Experimental Research of Visual Performance with Differenet Optical Spectrum Light Sources

2012 ◽  
Vol 433-440 ◽  
pp. 6375-6383 ◽  
Author(s):  
Yong Hong Yan ◽  
Yang Guan ◽  
G. Lee Tang
Keyword(s):  
Light Source ◽  
Optical Spectrum ◽  
Recognition Rate ◽  
Physiological Effect ◽  
Visual Performance ◽  
Light Sources ◽  
Light Spectrum ◽  
Colour Temperature ◽  
Fluorescent Lamps ◽  
Important Field

In order to determine the effect of different light source’s spectrum to a subjects’ visual performance, this experiment examined three fluorescent lamps with a colour temperature of 2700K, 4000K and 6500K and an incandescent lamp. The results were compared to the average recognition rate a “reference person” from different light sources. Experimental results show significant differences in the recognition rate from different optical spectrum light source and recognition rate value. We determined the best combination of ambient and chalkboard light source and propose avoiding combination for classroom lighting that is clearly inferior. This article provides selection reference for optimal classroom ambient and blackboard lighting. In recent years, the study of psychological and physiological effect of light has become one of the most important field in lighting research[1]. Studies has shown that different light spectrum could affect human circadian rhythm, body temperature and alertness, which directly affecting work efficiency and health[2]. The effects by classroom light spectrum on efficiency and health cannot be ignored, as the students are exposed to one particular lighting environment for extended periods of time. Through a systematic survey of classroom lighting in several universities in Chongqing and Chengdu, T5 fluorescent of high colour temperature about 6500K was the predominant choice for classroom general lighting as well as blackboard lighting. Many students complained that they tired easily at this colour temperature. In another study on classroom light source[3] students’ preference for colour temperature is not fixed but varies according to classroom’s function and illuminance level. It was insufficient to choose colour temperature of classroom lighting based on the results of the above questionnaire. We therefore chose and compared T5 fluorescent lamps of 2700K, 4000K and 6500K colour temperature on the visual performance and their effects on study efficiency, asthenopia and physiological rhythm. Due to space limitations this article only discusses the contrast experiment of visual performance.

A new measure of colour discrimination for LEDs and other light sources

2017 ◽  
Vol 51 (1) ◽  
pp. 5-23 ◽  
Author(s):  
T Esposito ◽  
K Houser
Keyword(s):  
Light Source ◽  
Strong Predictor ◽  
Source Spectrum ◽  
Light Sources ◽  
Common Belief ◽  
Colour Discrimination ◽  
Source Spectra

We show conclusively that, contrary to common belief, larger gamut area is not associated with better colour discrimination. We propose a new measure of colour discrimination, Rd, which quantifies the number of cap transpositions in the Farnsworth-Munsell 100 Hue Test (FM-100) that are introduced by a source spectrum. Rd was developed from 480 FM-100 tests (24 light sources × 20 participants per source), where the light source spectra systematically varied in IES Rf (from 65 to 95), Rg (from 80 to 120), and gamut shape. Rd was back tested on more than 200 common light sources to verify accordance with experience and anecdote and is a strong predictor of colour discrimination. We offer a direct way to interpret the Rd score. Light sources with superior colour discrimination have an Rd score of zero, meaning they introduce no transpositions, thus preserving FM-100 cap order. Light sources with average colour discrimination have an Rd score between 4 and 12; sources with poor colour discrimination have an Rd score of 16 or greater.

Organic Light Emitting Diodes - Innovative Light Sources

2019 ◽  
pp. 101-107
Author(s):  
Sergei A. Stakharny
Keyword(s):  
Light Source ◽  
Organic Light Emitting Diodes ◽  
Organic Leds ◽  
Light Sources ◽  
High Quality ◽  
Light Emitting ◽  
Organic Light ◽  
Lighting Systems ◽  
Physical Principles ◽  
Prospects Of Application

This article is a review of the new light source – organic LEDs having prospects of application in general and special lighting systems. The article describes physical principles of operation of organic LEDs, their advantages and principal differences from conventional non-organic LEDs and other light sources. Also the article devoted to contemporary achievements and prospects of development of this field in the spheres of both general and museum lighting as well as other spheres where properties of organic LEDs as high-quality light sources may be extremely useful.

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