scholarly journals Evaluation of Material Appearance Under Different Spotlight Distributions Compared to Natural Illumination

2019 ◽  
Vol 5 (2) ◽  
pp. 31
Author(s):  
Takashi Yamazoe ◽  
Tomohiro Funaki ◽  
Yuki Kiyasu ◽  
Yoko Mizokami
Keyword(s):  
Power Distribution ◽  
Spectral Power ◽  
Light Emitting Diode ◽  
Food Samples ◽  
Viewing Condition ◽  
Lighting Condition ◽  
Natural Illumination ◽  
Spectral Power Distribution ◽  
Material Appearance ◽  
Lighting Conditions

Solid-state lamps including Organic Light Emitting Diode (OLED) lighting could facilitate a wide variety of lighting conditions by controlling the spectral power distribution and the spatial distribution of the light source. The appearance of the surface of an object is significantly influenced by the lighting conditions and the constituent materials of the objects. Therefore, appearance of objects may appear to be different from expectation. Lighting condition leads to important part of accurate material recognition. We investigate whether it is possible to determine the lighting condition that results in the intended material appearance by the evaluation of this parameter under different lighting distributions compared to natural illumination. The viewing conditions of three spotlight sizes and three illuminance levels were investigated. The participants selected the viewing condition for which the appearance of fruits and vegetable food samples was the closest to the impressions learned from observing and freely holding these objects under natural reference illumination. Participants also evaluated their impressions of stimuli in each viewing condition by responding to twelve questions. The results show that the wide spotlight size condition with higher diffuseness of the illumination was selected more frequently than the narrow spotlight conditions. This suggests that the diffuseness of illumination influences the appearance of the object’s material. The results of seven-point scales suggest that their impression of stimuli was influenced by the surface properties of the objects as well as the lighting distributions. It was suggested that it is possible to set an appropriate lighting condition to facilitate material appearance similar to the expected appearance under natural illumination.

Evaluation of whiteness metrics

2016 ◽  
Vol 50 (3) ◽  
pp. 429-445 ◽  
Author(s):  
S Ma ◽  
M Wei ◽  
J Liang ◽  
B Wang ◽  
Y Chen ◽  
...  
Keyword(s):  
Power Distribution ◽  
Spectral Power ◽  
Light Sources ◽  
Lighting Condition ◽  
Spectral Power Distribution ◽  
White Region ◽  
Lighting Conditions ◽  
Fluorescent Whitening Agents ◽  
Different Levels ◽  
Psychophysical Study

Whiteness is an important characteristic for surface colour, which is affected by the spectral power distribution of the illumination due to the fluorescent whitening agents contained in many white objects. The CIE whiteness metric has been widely used but is known to have limitations. For example, the boundary noted by the metric is not considered large enough, because, in many cases, a surface whose chromaticity lies outside the boundary can still be perceived as white. Further, the metric is only defined to characterize the whiteness of a surface under CIE Illuminant D65, and thus it should not be applied in other lighting conditions or to other light sources. This paper describes a psychophysical study, investigating the whiteness of 50 samples (12 paper and 38 textile samples) under 12 lighting conditions with different levels of correlated colour temperature and ultraviolet radiation. An optimized whiteness metric and a boundary of the white region based on the CIE whiteness metric were derived from the results, which can be used to precisely measure the whiteness of a surface under any lighting condition and to guide spectral engineering for LED sources.

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.

Indoor Lighting Workplaces

2021 ◽  
pp. 243-258
Author(s):  
David Baeza Moyano ◽  
Roberto Alonso González Lezcano
Keyword(s):  
Power Distribution ◽  
Spectral Power ◽  
Light Emitting Diode ◽  
Working Environment ◽  
Office Work ◽  
Light Emitting ◽  
Spectral Power Distribution ◽  
Indoor Lighting ◽  
New Criteria

Office work has so far been carried out in company buildings and was largely based on the use of paper on a horizontal surface. Due to multiple reasons, more workers are working in their homes with electronic devices. As a result, both the working environment and personal tools are changing. Since the discovery about 20 years ago of the non-visual ways of light absorption, it was known that apart from the image forming effects (IF) of light from which the criteria for correct lighting have been developed, non-image forming effects (NIF) of light exist. The discovery of NIF has enhanced researcher belief in the importance of daylighting and has raised new criteria to be taken into account for proper interior lighting. Due to all the factors mentioned above, the parameters to be met by a luminaire and its environment for proper lighting of the workstation have been modified and expanded. The rapid advance in the development of new light-emitting diode (LED) luminaires with which the spectral power distribution (SPD) can be practically created opens the door to a genuine technological revolution comparable to the invention of electric lighting around 150 years ago. The authors of this study will review the latest published studies on the importance of light in our lives, IF and NIF effects of light, the parameters which from these effects are suggested to be taken into account for a correct indoor lighting, the regulations in force on indoor lighting workplaces, and proposals to improve indoor lighting and therefore the quality of life of workers.

Modeling and Parametric Study of Light Scattering, Absorption and Emission of Phosphor in a White Light-Emitting Diode

2015 ◽  
Author(s):  
Jiaqi Wang ◽  
Jeffery C. C. Lo ◽  
S. W. Ricky Lee ◽  
Feng Yun ◽  
Mian Tao
Keyword(s):  
Power Distribution ◽  
Spectral Power ◽  
Light Emitting Diode ◽  
Optical Parameter ◽  
Optical Parameters ◽  
Peak Wavelength ◽  
Spectrum Prediction ◽  
Light Emitting ◽  
Spectral Power Distribution ◽  
Radiant Power

In this study, we proposed and demonstrated an effective approach to model and predict spectral power distribution (SPD) for a phosphor-converted light emitting diode (pc-LED). For emission and excitation, broadband diffuse transmittances of 1 mm YAG:Ce phosphor plates with different concentrations were measured by a spectrophotometer. For emission, it was found that transmittance for all wavelengths was almost identical. This result indicates that emission spectrum prediction could be simplified by simulating the radiant power of the peak wavelength only. At the peak wavelength (560 nm), our simulation results, in which optical constants were calculated by the Lorenz-Mie theory, agreed well with our measurements. For excitation, a novel transmittance measurement setup based on an LED goniophotometer was proposed to obtain the absorption coefficient. By adjusting the optical parameter in our ray-tracing model to fit measured transmittances, accurate absorption coefficients were determined. Based on our calculation and measured optical parameters, we simulated the radiant power of the blue light and yellow light of commercial white LED packages. By expanding the total blue and yellow power into linear combinations of wavelengths in both regions, we successfully predicted the SPD of our LED package. Our predicted SPD has good agreement with the measured results.

scholarly journals Effective Radiant Flux for Non-image Forming Effects – is the Illuminance and the Melanopic Irradiance at the Eye Really the Right Measure

2018 ◽  
pp. 68-74 ◽  
Author(s):  
Kai Broszio ◽  
Martine Knoop ◽  
Mathias Niedling ◽  
Stephan Völker
Keyword(s):  
Power Distribution ◽  
Ganglion Cells ◽  
Spectral Power ◽  
Radiant Flux ◽  
Measured Quantity ◽  
Spectral Power Distribution ◽  
Spatially Resolved ◽  
Lighting Conditions ◽  
The Right ◽  
Office Lighting

Research indicates that intrinsically photosensitive Retinal Ganglion Cells are not evenly distributed or evenly sensitive throughout the retina. Still, most research looking into non-image forming (NIF) effects uses an integral measured quantity, illuminance or melanopic weighted irradiance, to represent the amount of light at the participantsХ eye level. This paper describes a theoretical approach to define the effective radiant flux for stimulating the ipRGCs, taking into account a spatially resolved sensitivity. Research on retinal sensitivity is scares and not yet substantial, but the methodology can easily be adopted when areas of specific sensitivity are set. Preliminary results indicate that, with similar vertical illuminances and spectral power distribution, typical office lighting solutions might have a lower NIF effectiveness than settings with higher luminances in the central part of the field of view. This could explain why research on NIF effects is inconclusive, even though reported lighting conditions are similar.

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