Surface Colour Matching under Conditions of Multiple Illuminants

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 190-190 ◽  
Author(s):  
H Irtel
Keyword(s):  
Light Source ◽  
Green Light ◽  
Light Sources ◽  
Local Contrast ◽  
Colour Constancy ◽  
Lighting Condition ◽  
3 Dimensional ◽  
Special Cases ◽  
Type Pattern ◽  
Light And Shadow

Most theories of colour constancy assume a flat coloured surface and a single homogenous light source. Natural situations, however, are 3-dimensional (3-D), are hardly ever restricted to a single light source, and object illumination is never homogenous. Here, two special cases of secondary light sources with sharp boundaries were simulated on a computer screen: a house-like 3-D object with colour patches in sunlight and shadow, and a Mondrian-type pattern with a coloured transparency covering some of the colour patches. Subjects made ‘paper’-matches between colour patches in light and shadow and between patches under the transparency and without the transparency. Matching did not depend on whether the simulated lighting condition was natural (yellow light, blue shadow) or artificial (green light, magenta shadow). Patches under a coloured transparency produced lightness constancy but subjects could not discount chromaticity shifts induced by the transparency. The number of context patches (2 vs 6) made no difference, and it made no difference whether the transparency covered the Mondrian completely or only partially. These results indicate that subjects were not able to use local contrast cues at sharp illumination boundaries to discount for the illuminant.

scholarly journals Colour Constancy for Image of Non-Uniformly Lit Scenes

Sensors ◽  
2019 ◽  
Vol 19 (10) ◽  
pp. 2242
Author(s):  
Md Akmol Hussain ◽  
Akbar Sheikh-Akbari ◽  
Iosif Mporas
Keyword(s):  
Light Source ◽  
State Of The Art ◽  
Incident Light ◽  
Digital Camera ◽  
Input Image ◽  
Absolute Difference ◽  
Light Sources ◽  
Colour Constancy ◽  
Adjustment Factors ◽  
Camera Sensors

Digital camera sensors are designed to record all incident light from a captured scene, but they are unable to distinguish between the colour of the light source and the true colour of objects. The resulting captured image exhibits a colour cast toward the colour of light source. This paper presents a colour constancy algorithm for images of scenes lit by non-uniform light sources. The proposed algorithm uses a histogram-based algorithm to determine the number of colour regions. It then applies the K-means++ algorithm on the input image, dividing the image into its segments. The proposed algorithm computes the Normalized Average Absolute Difference (NAAD) for each segment and uses it as a measure to determine if the segment has sufficient colour variations. The initial colour constancy adjustment factors for each segment with sufficient colour variation is calculated. The Colour Constancy Adjustment Weighting Factors (CCAWF) for each pixel of the image are determined by fusing the CCAWFs of the segments, weighted by their normalized Euclidian distance of the pixel from the center of the segments. Results show that the proposed method outperforms the statistical techniques and its images exhibit significantly higher subjective quality to those of the learning-based methods. In addition, the execution time of the proposed algorithm is comparable to statistical-based techniques and is much lower than those of the state-of-the-art learning-based methods.

scholarly journals Active Recurrence of Lighting Condition for Fine-Grained Change Detection

2018 ◽  
Author(s):  
Qian Zhang ◽  
Wei Feng ◽  
Liang Wan ◽  
Fei-Peng Tian ◽  
Ping Tan
Keyword(s):  
Change Detection ◽  
Light Source ◽  
Real World ◽  
Reference Image ◽  
Light Sources ◽  
Lighting Condition ◽  
Fine Grained ◽  
Lighting Conditions ◽  
Point Light ◽  
Change Monitoring

This paper addresses active lighting recurrence (ALR), a new problem that actively relocalizes a light source to physically reproduce the lighting condition for a same scene from single reference image. ALR is of great importance for fine-grained visual monitoring and change detection, because some phenomena or minute changes can only be clearly observed under particular lighting conditions. Hence, effective ALR should be able to online navigate a light source toward the target pose, which is challenging due to the complexity and diversity of real-world lighting \& imaging processes. We propose to use the simple parallel lighting as an analogy model and based on Lambertian law to compose an instant navigation ball for this purpose. We theoretically prove the feasibility of this ALR strategy for realistic near point light sources and its invariance to the ambiguity of normal \& lighting decomposition. Extensive quantitative experiments and challenging real-world tasks on fine-grained change monitoring of cultural heritages verify the effectiveness of our approach. We also validate its generality to non-Lambertian scenes. 

Safest light in a combat area while performing intravenous access in the dark

2018 ◽  
Vol 164 (5) ◽  
pp. 343-346 ◽  
Author(s):  
Attila Aydin ◽  
S Bilge ◽  
M Eryilmaz
Keyword(s):  
Light Source ◽  
Blue Light ◽  
Green Light ◽  
Night Vision ◽  
Infrared Light ◽  
Light Sources ◽  
Night Time ◽  
Naked Eye ◽  
Prehospital Management ◽  
Dark Room

IntroductionCannulation for the administration of intravenous fluids is integral to the prehospital management of injured military patients. However, this may be technically challenging to undertake during night-time conditions where the use of light to aid cannulation may give the tactical situation away to opponents. The aim of this study was to investigate the success and tactical safety of venepuncture under battlefield conditions with different colour light sources.MethodThe procedure was carried out with naked eye in a bright room in the absence of a separate light source, with a naked eye in a dark room under red, white, blue and green light sources and under an infrared light source while wearing night vision goggles (NVGs). The success, safety, degree of difficulty and completion time for each procedure were then explored.ResultsAll interventions made in daylight and in a dark room were found to be 100% successful. Interventions performed under infrared light while wearing NVGs took longer than under other light sources or in daylight. Interventions performed under blue light were tactically safer when compared with interventions performed under different light sources.ConclusionBlue light offered the best tactical safety during intravenous cannulation under night-time conditions and is recommended for future use in tactical casualty care. The use of NVGs using infrared light cannot be recommended if there is the possibility of opponents having access to the technology.

scholarly journals Accuracy of the GENEActiv Device for Measuring Light Exposure in Sleep and Circadian Research

2020 ◽  
Vol 2 (2) ◽  
pp. 143-152
Author(s):  
Julia E. Stone ◽  
Elise M. McGlashan ◽  
Elise R. Facer-Childs ◽  
Sean W. Cain ◽  
Andrew J. K. Phillips
Keyword(s):  
Light Source ◽  
Light Exposure ◽  
Red Light ◽  
Spectral Composition ◽  
Green Light ◽  
Well Being ◽  
Infrared Light ◽  
Light Sources ◽  
Lower Accuracy ◽  
The Impact

Light is a variable of key interest in circadian rhythms research, commonly measured using wrist-worn sensors. The GENEActiv Original is a cost-effective and practical option for assessing light in ambulatory settings. With increasing research on health and well-being incorporating sleep and circadian factors, the validity of wearable devices for assessing light environments needs to be evaluated. In this study, we tested the accuracy of the GENEActiv Original devices (n = 10) for recording light under a range of ecologically relevant lighting conditions, including LED, fluorescent, infrared, and outdoor lighting. The GENEActiv output had a strong linear relationship with photopic illuminance. However, the devices consistently under-reported photopic illuminance, especially below 100 lux. Accuracy below 100 lux depended on the light source, with lower accuracy and higher variability under fluorescent lighting. The device’s accuracy was also tested using light sources of varying spectral composition, which indicated that the device tends to under-report photopic illuminance for green light sources and over-report for red light sources. Furthermore, measures of photopic illuminance were impacted by infrared light exposure. We conclude that the GENEActiv Original is suitable for mapping light patterns within an individual context, and can reasonably differentiate indoor vs. outdoor lighting, though the accuracy is variable at low light conditions. Given the human circadian system’s high sensitivity to light levels below 100 lux, if using the GENEActiv Original, we recommend also collecting light source data to better understand the impact on the circadian system, especially where participants spend prolonged periods in dim lighting.

scholarly journals Green-light Supplementation for Enhanced Lettuce Growth under Red- and Blue-light-emitting Diodes

HortScience ◽  
2004 ◽  
Vol 39 (7) ◽  
pp. 1617-1622 ◽  
Author(s):  
Hyeon-Hye Kim ◽  
Gregory D. Goins ◽  
Raymond M. Wheeler ◽  
John C. Sager
Keyword(s):  
Plant Growth ◽  
Light Source ◽  
Blue Light ◽  
Light Emitting Diodes ◽  
Green Light ◽  
Light Sources ◽  
Natural Setting ◽  
Light Emitting ◽  
Fluorescent Lamps ◽  
Green Fluorescent

Plants will be an important component of future long-term space missions. Lighting systems for growing plants will need to be lightweight, reliable, and durable, and light-emitting diodes (LEDs) have these characteristics. Previous studies demonstrated that the combination of red and blue light was an effective light source for several crops. Yet the appearance of plants under red and blue lighting is purplish gray making visual assessment of any problems difficult. The addition of green light would make the plant leave appear green and normal similar to a natural setting under white light and may also offer a psychological benefit to the crew. Green supplemental lighting could also offer benefits, since green light can better penetrate the plant canopy and potentially increase plant growth by increasing photosynthesis from the leaves in the lower canopy. In this study, four light sources were tested: 1) red and blue LEDs (RB), 2) red and blue LEDs with green fluorescent lamps (RGB), 3) green fluorescent lamps (GF), and 4) cool-white fluorescent lamps (CWF), that provided 0%, 24%, 86%, and 51% of the total PPF in the green region of the spectrum, respectively. The addition of 24% green light (500 to 600 nm) to red and blue LEDs (RGB treatment) enhanced plant growth. The RGB treatment plants produced more biomass than the plants grown under the cool-white fluorescent lamps (CWF treatment), a commonly tested light source used as a broad-spectrum control.

Merging of electron-diffraction intensities acquired with a slow-scan CCD camera of crotoxin complex crystals to 3.5Å resolution

1994 ◽  
Vol 52 ◽  
pp. 104-105
Author(s):  
Jaap Brink ◽  
Wah Chiu
Keyword(s):  
Electron Diffraction ◽  
Ccd Camera ◽  
Crystal Thickness ◽  
Local Contrast ◽  
Camera Model ◽  
Data Set ◽  
3 Dimensional ◽  
Diffraction Mode ◽  
Diffraction Patterns ◽  
Complex Crystals

Crotoxin complex is the principal neurotoxin of the South American rattlesnake, Crotalus durissus terrificus and has a molecular weight of 24 kDa. The protein is a heterodimer with subunit A assigneda chaperone function. Subunit B carries the lethal activity, which is exerted on both sides ofthe neuro-muscular junction, and which is thought to involve binding to the acetylcholine receptor. Insight in crotoxin complex’ mode of action can be gained from a 3 Å resolution structure obtained by electron crystallography. This abstract communicates our progress in merging the electron diffraction amplitudes into a 3-dimensional (3D) intensity data set close to completion. Since the thickness of crotoxin complex crystals varies from one crystal to the other, we chose to collect tilt series of electron diffraction patterns after determining their thickness. Furthermore, by making use of the symmetry present in these tilt data, intensities collected only from similar crystals will be merged.Suitable crystals of glucose-embedded crotoxin complex were searched for in the defocussed diffraction mode with the goniometer tilted to 55° of higher in a JEOL4000 electron cryo-microscopc operated at 400 kV with the crystals kept at -120°C in a Gatan 626 cryo-holder. The crystal thickness was measured using the local contrast of the crystal relative to the supporting film from search-mode images acquired using a 1024 x 1024 slow-scan CCD camera (model 679, Gatan Inc.).

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.

scholarly journals Analysis on High-Power Seaport LED Luminaire with Uniform Light Distribution Based on Optimized Lens and Heatsink

2021 ◽  
Vol 11 (9) ◽  
pp. 4035
Author(s):  
Jinsheon Kim ◽  
Jeungmo Kang ◽  
Woojin Jang
Keyword(s):  
Light Source ◽  
High Power ◽  
Heat Dissipation ◽  
Light Emitting Diode ◽  
Light Distribution ◽  
Light Sources ◽  
Led Light ◽  
High Power Led ◽  
Distribution Requirement ◽  
Lighting Application

In the case of light-emitting diode (LED) seaport luminaires, they should be designed in consideration of glare, average illuminance, and overall uniformity. Although it is possible to implement light distribution through auxiliary devices such as reflectors, it means increasing the weight and size of the luminaire, which reduces the feasibility. Considering the special environment of seaport luminaires, which are installed at a height of 30 m or more, it is necessary to reduce the weight of the device, facilitate replacement, and secure a light source with a long life. In this paper, an optimized lens design was investigated to provide uniform light distribution to meet the requirement in the seaport lighting application. Four types of lens were designed and fabricated to verify the uniform light distribution requirement for the seaport lighting application. Using numerical analysis, we optimized the lens that provides the required minimum overall uniformity for the seaport lighting application. A theoretical analysis for the heatsink structure and shape were conducted to reduce the heat from the high-power LED light sources up to 250 W. As a result of these analyses on the heat dissipation characteristics of the high-power LED light source used in the LED seaport luminaire, the heatsink with hexagonal-shape fins shows the best heat dissipation effect. Finally, a prototype LED seaport luminaire with an optimized lens and heat sink was fabricated and tested in a real seaport environment. The light distribution characteristics of this prototype LED seaport luminaire were compared with a commercial high-pressure sodium luminaire and metal halide luminaire.

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.

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