Interactive effect of illuminance and correlated colour temperature on colour preference and degree of white light sensation for Chinese observers

Optik ◽  
2020 ◽  
Vol 224 ◽  
pp. 165675
Author(s):  
Yu Wang ◽  
Qiang Liu ◽  
Wenyu Gao ◽  
Michael R. Pointer ◽  
Zheng Huang ◽  
...  
Keyword(s):  
White Light ◽  
Interactive Effect ◽  
Colour Preference ◽  
Colour Temperature

Colour preference, naturalness, vividness and colour quality metrics, Part 3: Experiments with makeup products and analysis of the complete warm white dataset

2016 ◽  
Vol 50 (2) ◽  
pp. 218-236 ◽  
Author(s):  
TQ Khanh ◽  
P Bodrogi
Keyword(s):  
Linear Combination ◽  
White Light ◽  
Light Sources ◽  
Complex Phenomenon ◽  
Cosmetic Products ◽  
Colour Preference ◽  
Colour Temperature ◽  
Cognitive Components ◽  
Warm White Light ◽  
Moderate Range

Light source colour quality is a complex phenomenon with several visual and cognitive components. Subjective colour preference, naturalness and vividness assessments of reddish cosmetic products in a viewing booth lit by light sources with a correlated colour temperature of 3200 K and to 550 lx were analysed and modelled by a new combined colour quality formula – a linear combination of a colour fidelity index and a measure of chroma change. Results of the warm white light sources described in all three parts of this work were merged. They were modelled by optimising the parameters of the same formula. The formula supports multi-LED light sources with moderately accentuated local spectral maxima to enhance object chroma over a moderate range.

scholarly journals Colour Temperature Tuning to Improve Efficacy of White Light

2016 ◽  
Vol 24 ◽  
pp. 1186-1193 ◽  
Author(s):  
Saijo Prathap ◽  
Sonia Sunny ◽  
Aju S. Nair
Keyword(s):  
White Light ◽  
Colour Temperature ◽  
Temperature Tuning

Towards a user preference model for interior lighting, Part 3: An alternative model

2019 ◽  
Vol 52 (2) ◽  
pp. 189-201
Author(s):  
TQ Khanh ◽  
P Bodrogi ◽  
X Guo
Keyword(s):  
Alternative Model ◽  
User Preference ◽  
Colour Preference ◽  
Type Representation ◽  
Contour Map ◽  
Preference Model ◽  
Colour Temperature ◽  
Independent Variables ◽  
Interior Lighting ◽  
Present Part

In Parts 1 and 2 of this work, an experiment was described in which subjects assessed their visual impressions of scene brightness (B), visual clarity (VC), colour preference (CP) and scene preference (SP) in a real room. In this room, the horizontal illuminance ( Ev), the correlated colour temperature (CCT) and the level of chroma enhancement caused by the spectrum of the light source (Δ C*) were changed systematically. In the present Part 3, these mean subjective B, VC, CP and SP scale values are re-analysed in terms of an alternative model based on a different set of independent variables: CCT, Δ C* and the circadian stimulus (CS). Contour map diagrams resulting from the new modelling equations are shown and compared with the conventional Kruithof-type representation.

Colour preference, naturalness, vividness and colour quality metrics, Part 1: Experiments in a room

2016 ◽  
Vol 49 (6) ◽  
pp. 697-713 ◽  
Author(s):  
TQ Khanh ◽  
P Bodrogi ◽  
QT Vinh ◽  
D Stojanovic
Keyword(s):  
Quality Metrics ◽  
Saturation Effect ◽  
Light Sources ◽  
Quality Indices ◽  
Colour Preference ◽  
Colour Temperature ◽  
Semantic Categories ◽  
Interval Scales ◽  
Office Lighting ◽  
Spectral Design

In Part I of this work, observers scaled colour preference, naturalness and vividness visually on interval scales (0–100) labelled by semantic categories (e.g. ‘moderate’, ‘good’ and ‘very good’) in the context of office lighting. Five customary light sources without object saturation effect illuminated a table with coloured objects in a real room. The observers’ assessments were predicted by recent colour quality indices and selected pairs of indices combined linearly. Criterion values of the indices for ‘good’ colour preference and vividness were determined to provide a usable acceptance limit for the spectral design and evaluation of light sources. To predict colour preference, correlated colour temperature turned out to be useful. In Part 2 of this work, another experiment with the same method but using multi-LED spectra with more object saturation will be analysed and the two datasets will be merged.

A white–cyan-red LED system for low correlated colour temperature lighting

2015 ◽  
Vol 49 (3) ◽  
pp. 343-356 ◽  
Author(s):  
M Chakrabarti ◽  
A Thorseth ◽  
DD Corell ◽  
C Dam-Hansen
Keyword(s):  
White Light ◽  
Colour Temperature ◽  
White Leds ◽  
Geometrical Modelling ◽  
Red Led ◽  
Colour Gamut ◽  
Museum Display ◽  
Colour Rendering ◽  
Red Leds ◽  
Planckian Locus

A white LED complemented by cyan and red LEDs is a good candidate for achieving high colour rendering at low correlated colour temperatures. This is usually very difficult with commercially available white LEDs. In addition, the system is able to replace incandescent lighting in many applications; for example, the lighting for museum display cases. To investigate and optimize the colour and light distribution properties, both spectral and geometrical modelling are used. Mapping of the possible combinations of LEDs is used to locate the optimal solutions within the colour gamut, with emphasis on chromaticity and colour rendering indices. A geometric optical model is used to design and optimize the homogeneity of the colour and light intensity distribution as a function of angle. The resulting system produces diffused homogeneous white light with a tunable correlated colour temperature from 2000 K to 2400 K. Within this range the white light is characterized by a high general colour rendering index (Ra > 90), special colour rendering indices for saturated red objects (R9 > 85), and low chromaticity distance (Duv) from the Planckian locus (Duv < 2 × 10−3).

Operating Control of Photobiological Safety of LED Luminaires

2019 ◽  
pp. 37-42
Author(s):  
Alexander V. Karev ◽  
Dmitry S. Dmitry S. Lyoskin
Keyword(s):  
White Light ◽  
Laboratory Testing ◽  
Risk Level ◽  
International Electrotechnical Commission ◽  
Special Equipment ◽  
Experimental Assessment ◽  
Russian Market ◽  
Colour Temperature ◽  
Safety Requirements ◽  
Hazard Level

Photobiological safety has become an integral part of safety requirements to general use luminaires including during certification. In that context, the necessity to control this parameter in the course of designing and manufacturing of lighting devices (luminaires) as well as sales of imported devices in the Russian market has increased dramatically. In the meantime, experimental assessment of this indicator in accordance with requirements of IEC62471Р¦2013 standard is rather hard requiring application of special equipment and certified personnel. This circumstance makes operating control of photobiological safety by manufacturers almost impossible. The foreign practice of application photobiological safety-related standards confirms this problem. In 2014, International Electrotechnical Commission has published a handbook for application of the standard provisions, which significantly simplifies the procedure of such assessments: IEC/ TR62778:2014. The article describes the method of application of provisions of this handbook as an operating tool in the course of development of general use LED luminaires with white light LED. The provisions consist of assessment of hazard level in terms of illuminance in the area of the most possible location of a spectator and colour characteristics of a light source. A calculation method of risk level assessment on the basis of spatial light distribution and correlated colour temperature of LED luminaires is proposed, the results of calculations are compared with the results of laboratory testing.

Colour preference, naturalness, vividness and colour quality metrics, Part 4: Experiments with still life arrangements at different correlated colour temperatures

2017 ◽  
Vol 50 (6) ◽  
pp. 862-879 ◽  
Author(s):  
TQ Khanh ◽  
P Bodrogi ◽  
QT Vinh ◽  
X Guo ◽  
TT Anh
Keyword(s):  
Quality Metrics ◽  
Still Life ◽  
Colour Preference ◽  
Colour Temperature ◽  
Led Light ◽  
Significant Dependence ◽  
Subjective Judgments ◽  
Light Engine

Subjective colour preference, naturalness and vividness assessments of two different colourful still life arrangements viewed in a real room were analysed and modelled with the aid of the Rf colour fidelity metric combined with a chroma difference metric. Coloured objects were illuminated by a four-channel LED light engine with 36 different spectra at four correlated colour temperatures and nine object oversaturation levels. Results imply a significant dependence of the subjective judgments on correlated colour temperature.

scholarly journals Low-Cost Extra-Low Voltage LED Dimmer for Tuneable White Lighting

2019 ◽  
Vol 25 (3) ◽  
pp. 43-49
Author(s):  
Roman Hrbac ◽  
Tomas Mlcak ◽  
Vaclav Kolar ◽  
Tomas Vantuch
Keyword(s):  
White Light ◽  
Low Voltage ◽  
Low Cost ◽  
Light Output ◽  
Electrical Performance ◽  
Light Sources ◽  
Colour Temperature ◽  
Lighting Systems ◽  
Module Efficiency ◽  
The Right

The colour appearance of light sources has a major impact on how people perceive space. With LED illumination lighting, the colour output can be tuned to virtually any perceivable colour, including any hue of white light. It has been established that the right shade of white light during the 24-hour day cycle has a positive effect on the human body's biological system. For this reason, it is very important to focus on the development and application of new lighting systems that have dynamically variable light outputs in order to imitate the sunlight. Circadian regulation is most responsive to short-wavelength light (460 nm = blue colour). This paper describes the development of a low-cost extra-low voltage LED dimmer for tunable white lighting systems aiming to achieve maximum electrical performance and light-output. This dimming module has two independent LED control channels and allows for a variable colour temperature control from warm white to cold white light. Experimental results of the dimming module efficiency measurements, correlated colour temperature (CCT), colour rendering index (CRI), illuminance and power consumption of the luminaire depending on the duty cycle for different control frequencies (200 Hz, 1.5 kHz, 5 kHz, 10 kHz and 20 kHz) are presented. The paper further describes the principle of creating control curves for an independent regulation of correlated colour temperature and illuminance. In the form of a table, the control curve outputs may be uploaded into a microcontroller. The paper details the construction, function and the advantages of this LED dimmer prototype.

Thermally Stable Encapsulation Material Based on Green and Red Lanthanide Phosphor for White Light Emitting Diodes

2015 ◽  
Vol 815 ◽  
pp. 182-187
Author(s):  
Wedianti Shualdi ◽  
Nik Mohd Azmi ◽  
Nurul Huda Yusoff ◽  
Nor Adhila Muhammad ◽  
Khairuldin Mohd Isha
Keyword(s):  
White Light ◽  
Sol Gel ◽  
Junction Temperature ◽  
Integrating Sphere ◽  
Light Emitting ◽  
Colour Temperature ◽  
Uv Led ◽  
Lanthanides Complexes ◽  
The Stability ◽  
White Light Emitting Diodes

This study reported thermal stability of hybrid sol-gel encapsulation materials doped with lanthanides complexes for generating white light. Red and green lanthanide phosphor, Eu (tta)3phen and Tb (4DBBA)3TPPO were incorporated into VTES:TEOS hybrid sol-gel and dispensed into 360 nm to 390 nm UV LED packages. Thermal properties of developed encapsulation material were analysed by TGA. A thermal aging test up to 96 hours was done to check the stability of developed encapsulation material towards UV LED junction temperature of 120°C and the luminescence properties changes was observed using photoluminescence measurement. To check the encapsulation material stability on forward voltage, the operation voltage has been increased from 3.0V to 4.0V. The photometric measurement were recorded using integrating sphere for the properties of Colour Rendering Index (CRI), colour temperature and Commission Internationale de L’Eclairge (CIE) colour coordinates. Based on the results, developed encapsulation material produced white colour with CIE colour coordinate of (0.32, 0.35), CRI up to 75 and colour temperature around 6000K.

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