scholarly journals Evaluation of Visual and Nonvisual Levels of Daylight from Spectral Power Distributions Considering Orientation and Seasonality

2021 ◽  
Vol 11 (13) ◽  
pp. 5996
Author(s):  
Silvia Ezpeleta ◽  
Elvira Orduna-Hospital ◽  
Justiniano Aporta ◽  
María José Luesma ◽  
Isabel Pinilla ◽  
...  
Keyword(s):  
Power Distribution ◽  
Evaluation Method ◽  
Spectral Power ◽  
Lighting Design ◽  
Simple Method ◽  
Colour Temperature ◽  
Spectral Power Distribution ◽  
Best Parameter ◽  
One Year ◽  
The City

The evaluation of both visual and nonvisual effects from the spectral power distribution (SPD) of outdoor light is critical in lighting design. The dome-light SPD characteristically changes continuously depending on the seasonality, orientation, altitude of the sun or hour of the day. Traditional photopic parameters, such as the illuminance, luminance or correlated colour temperature (CCT), have been widely studied, but presently, there is no melanopic measurement or evaluation method. This article discusses the processes involved in establishing a simple method to determine the SPD of daylight and solar radiation over the skydome in a location to accurately account for the effects of both photopic and circadian levels around a location. Once per month for one year, natural daylight was spectrally measured in the city of Zaragoza (Spain); radiometric and photometric characteristics were analysed by season; and circadian effects were calculated in terms of standard parameters described by the Commission International de l’Eclairage (CIE), factors recommended by normative and scientific backgrounds. Finally, we suggest that the best parameter is the melanopic versus photopic irradiance ratio, which achieves reliable results at simplifying and correlating calculations.

scholarly journals Optimising the illumination spectrum for enhancing tissue visualisation

2017 ◽  
Vol 51 (1) ◽  
pp. 99-110 ◽  
Author(s):  
J Shen ◽  
S Chang ◽  
H Wang ◽  
Z Zheng
Keyword(s):  
Biological Tissue ◽  
Power Distribution ◽  
Spectral Reflectance ◽  
Evaluation Method ◽  
Multispectral Imaging ◽  
Spectral Power ◽  
Light Sources ◽  
White Led ◽  
Spectral Power Distribution ◽  
Visual Entropy

In operations, light reflected from biological tissue can be used for disease detection. In this paper, we used a visual entropy evaluation method to design the optimal illuminant to improve colour discriminability of biological tissue. The optimal spectral power distribution of the illuminant was obtained by maximising the visual entropy value of sample tissue based on the human visual system. In the experiment, multispectral imaging was used to measure the spectral reflectance of the tissue and colour clustering was conducted to extract its colour features. To verify the effectiveness of this method, simulated tissue images under illuminations with optimised spectral power distributions were compared with those under other light sources such as the standard illuminant D65 and white LED light sources. Results show that the sample under optimised illumination has a higher visual entropy value with better perceptual visibility.

Absolute radiometry by means of a black body source

1973 ◽  
Vol 335 (1602) ◽  
pp. 369-386 ◽  
Keyword(s):  
Power Distribution ◽  
Temperature Scale ◽  
Spectral Power ◽  
Freezing Temperature ◽  
Black Body ◽  
Practical Realization ◽  
Colour Temperature ◽  
Spectral Power Distribution ◽  
Absolute Radiometry ◽  
Photometric Scale

The use of a black body lamp whose temperature is established by means of optical pyrometry can conveniently provide a standard spectral power distribution that is known in absolute terms. The degree of reproducibility demonstrated in the present work suggests that a practical realization of the candela by this method may be preferable to the conventional approach using freezing platinum. The experiment described interrelates four of the basic scales maintained by the N. P. L. (and other national laboratories): these are the temperature scale, the photometric scale, the colour temperature scale and the radiometric scale. One interpretation of the results is that the freezing temperature of platinum implicit in the photometric scale is about 3K higher than that realized in recent temperature scale work. On the other hand, a previously established relation between the photometric and radiometric scales tends to support the lower value for T Pt .

LED chip-on-board package with high colour rendering index and high luminous efficacy

2017 ◽  
Vol 50 (3) ◽  
pp. 482-488 ◽  
Author(s):  
Z Zhou ◽  
H Wang ◽  
J Zhang ◽  
J Su ◽  
P Ge
Keyword(s):  
White Light ◽  
Power Distribution ◽  
Spectral Power ◽  
White Led ◽  
Phosphor Powder ◽  
Phosphor Layer ◽  
Luminous Efficacy ◽  
Colour Temperature ◽  
Spectral Power Distribution ◽  
Colour Rendering

Existing white light LED technology uses a blue light LED chip to stimulate a phosphor powder to form white light. The phosphor layer on the surface directly affects the colour rendering index, luminous efficacy and colour temperature of the LED. We propose a high power, white LED, chip-on-board package technology to achieve high colour rendering index and high luminous efficacy by optimising the spectral power distribution. The chip-on-board package light source can achieve a colour rendering index over 90 and a luminous efficacy over 90 lm/W while the power is 45W. It can be widely used in commercial lighting applications.

Supercontinuum laser-based monochromatic radiant source for detector spectral responsivity characterization in the range 0.9–1.6 μm using absolute cryogenic radiometer

2020 ◽  
pp. 28-33
Author(s):  
A. Yu. Dunaev ◽  
A. S. Baturin ◽  
V. N. Krutikov ◽  
S. P. Morozova
Keyword(s):  
Power Distribution ◽  
Spectral Power ◽  
Feedback System ◽  
Operating Mode ◽  
Spectral Responsivity ◽  
Spectral Power Distribution ◽  
Cryogenic Radiometer ◽  
Supercontinuum Laser ◽  
Radiant Power ◽  
Double Monochromator

An improved monochromatic radiant source with spectral bandwidth of 4 nm based on supercontinuum laser and a double monochromator was included in absolute cryogenic radiometer-based facility to improve the accuracy of spectral responsivity measurement in the range 0.9–1.6 μm. The developed feedback system ensures stabilization of monochromatic radiant power with standard deviation up to 0.025 %. Radiant power that proceeds detector under test or absolute cryogenic radiometer varies from 0.1 to 1.5 mW in dependence of wavelength. The spectral power distribution of its monochromatic source for various operating mode is presented.

scholarly journals Influences of Spectral Power Distribution on Circadian Energy, Visual Comfort and Work Performance

2021 ◽  
Vol 13 (9) ◽  
pp. 4852
Author(s):  
Jack Ngarambe ◽  
Inhan Kim ◽  
Geun Young Yun
Keyword(s):  
Light Source ◽  
Power Distribution ◽  
Work Performance ◽  
Spectral Power ◽  
Light Emitting Diode ◽  
Essential Element ◽  
Visual Comfort ◽  
Light Emitting ◽  
Organic Light Emitting Diode ◽  
Spectral Power Distribution

Spectral power distribution (SPD) is an essential element that has considerable implications on circadian energy and the perception of lit environments. The present study assessed the potential influences of SPD on energy consumption (i.e., considering circadian energy), visual comfort, work performance and mood. Two lighting conditions based on light-emitting diode (LED) and organic light-emitting diode (OLED) were used as proxies for SPDs of different spectral content: dominant peak wavelength of 455 nm (LED) and 618 nm (OLED). Using measured photometric values, the circadian light (CL), melatonin suppression (MS), and circadian efficacy (CE) of the two lighting sources were estimated via a circadian-phototransduction model and compared. Additionally, twenty-six participants were asked to evaluate the said lit environments subjectively in terms of visual comfort and self-reported work performance. Regarding circadian lighting and the associated energy implications, the LED light source induced higher biological actions with relatively less energy than the OLED light source. For visual comfort, OLED lighting-based conditions were preferred to LED lighting-based conditions, while the opposite was true when considering work performance and mood. The current study adds to the on-going debate regarding human-centric lighting, particularly considering the role of SPD in energy-efficient and circadian lighting practices.

scholarly journals The spectral power distribution of light and twilight photometry

2017 ◽  
Vol 0 (1) ◽  
pp. 43-52
Author(s):  
Леонід Андрійович Назаренко ◽  
Тетяна Можаровська ◽  
Дмитро Усиченко
Keyword(s):  
Power Distribution ◽  
Spectral Power ◽  
Spectral Power Distribution

LED for hyperspectral imaging – a new selection method

2018 ◽  
Vol 63 (5) ◽  
pp. 529-535 ◽  
Author(s):  
Tobias Heimpold ◽  
Frank Reifegerste ◽  
Stefan Drechsel ◽  
Jens Lienig
Keyword(s):  
Hyperspectral Imaging ◽  
Power Distribution ◽  
Spectral Power ◽  
Selection Process ◽  
Selection Method ◽  
Light Emitting ◽  
Spectral Power Distribution ◽  
Forward Current ◽  
Efficient Selection ◽  
Selection Of

AbstractHyperspectral imaging (HSI) has become a sophisticated technique in modern applications such as food analyses, recycling technology, medicine, pharmacy and forensic science. It allows one to analyse both spatial and spectral information from an object. But hyperspectral cameras are still expensive due to their extended wavelength range. The development of new light-emitting diodes (LED) in the recent past enables another approach to HSI using a monochrome camera in combination with a LED-based illumination. However, such a system has a lower spectral resolution. Additionally, the growing supply of LED on the market complicates the selection of LED. In this paper, we propose a new time efficient selection method for the design process of an illumination. It chooses an optimised LED combination from an existing database to match a predefined spectral power distribution. Therefore, an algorithm is used to evaluate various LED combinations. Furthermore, the method considers the spectral behaviour of each LED in dependence of forward current and temperature of the solder point. Our method has already shown promise during the selection process for even spectral distributions which is demonstrated in the study. Additionally, we will show its potential for HSI illuminations.

AN OVERVIEW OF THE IMPACT OF STRAY LIGHT FROM COMMERCIAL GREENHOUSES

2021 ◽  
Author(s):  
K. Bertin ◽  
G. Zissis ◽  
G. Salas ◽  
P.M. Raynham ◽  
A. Moutsi ◽  
...  
Keyword(s):  
Power Distribution ◽  
Spectral Power ◽  
Stray Light ◽  
Significant Problem ◽  
Light Sources ◽  
Spectral Power Distribution ◽  
Outdoor Work ◽  
Local Residents ◽  
The Impact ◽  
Current Standards

Stray light from commercial greenhouses is becoming a significant problem causing disruption to wildlife activity and annoyance for local residents. To quantify the amount of stray light from a typical large greenhouse the authors have modelled several lighting installations based on a range of generic horticultural light sources. The impact of the stray light is dependent on the spectral power distribution of the sources employed, the intensity and distribution. Current standards for obtrusive light from outdoor work places do not seem to be suitable when applied to greenhouses.

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