Share what we know, what we learn and what we recommend.
In issue # 78 of LpR (LED professional Review: https://lnkd.in/feAvuhe), we proposed and introduced detailedly such a new method of spectral tuning idea with accurate chromaticity control and promising color rendition performance.
This fundamental spectral tuning method can be used in different applications by specific tuning optimizations:
● Matching with the melanopic sensitivity to provide a real human-centric lighting environment.
● Simulating CIE standard illuminates to a precise level for analyzing scientific projects of color.
● Providing to plants with the dynamic light with the most similar features of sunlight.
● Providing high CRI lighting for artistic creation or photography requires a critical color reproduction environment.
What is your idea to apply this new method?
What does a white light with enhanced near-infrared look like?
In recent research, we succeed to synthesize a spectrum with a white light base, enhancing the near-infrared energy significantly. Compared to a standard LED, it increases nearly 50% of the longer wavelength, and compared to the deep red enhanced LED (high CRI), it still increases by 25%.
Will this redefine “full-spectrum”?
The experiment with Linear Variable Bandpass Filters (LVVISBP) from Delta Optical Thin Film A/S gives us the most intuitive effect. The light after this filter presents all detailed peaks and gaps in the original spectrum loyally. By splitting the wavelengths respectively, we can see clearly the benefit of choosing a full and smooth spectrum LED.
The award-winning photographer Al Lapkovsky shared his experience of the shooting task with Yujileds high CRI series flexible strip and COB LED in the post below. With the widely use of LED technology in different lighting applications, now it is well recognized that the critical factors of a suitable LED source for photography should be:
• Excellent color rendition.
This is the key to present the true colors of the photographed subjects.
• The purity of white light.
This is sometimes ignored by photographers, however, it is still crucial that whether you could obtain the final images with desired color tones without complex post-production. Regardless of the warm or cold color, the concept of white purity is universal to create a natural “taste”.
• The flexibility of use, and lighting intensity.
Photography is a kind of creative work. Whether the light source is capable to achieve as highest or lowest intensity, whether it is easy to make light in a narrow corner, whether it can be used as linear, circled or in any specific shapes, these all decide if the feeling is “touching” enough.
The latest project from SAGA Space Architects – LUNARK, aims to challenge the living condition on the moon. Later in 2020, the crews will start the first adventure in northern Greenland, where the environment is most similar to the moon’s surface. They will spend three months in the completely enclosed Habitat for a series of studies. Yujileds is excited to join the team as the LED lighting consultant for providing the circadian lighting environment with a tailor-made LED solution.
During the mission, the circadian rhythm, psychological and biological effects, which are all correlated to the lighting conditions, will be studied further. LED lighting is facing an unprecedented challenge since it is the first time that humans will be separated away to the natural light completely and only rely on the artificial light source for daily life. But we are excited to see the result and expect to reap from the studies by cooperating with different experts and professors in different fields.
In the latest video from the DIY Perks, Yujileds BC160H LED is used for making a true 4K cinema projector. The fact of over 1 million views and 80000 likes within only 3 days once again proves their strong ability to innovate, and the performance of this 4K projector does seem fantastic.
How does the BC160H LED work so well for the projector?
• Based on the flip-chip and eutectic bonding technologies, there is no wire between the LED dies and substrate thus the illumination area is extremely compact (LES=10mm) but the high power is maintained. Strong output and impact size are both the key points to make the projector feasible because these determine the optical design and the entire system.
• It offers the color rendering index above 95 to present the original colors from the screen without losing or deviating any color details.
• 5600K color temperature gives a perfect purity of white, and the chromaticity design of the BC160H LED is optimized without any green or magenta tendency.
In the book of “LED Lighting: Technology and Perception”, the author talks about the relationship between CRI and circadian stimulus (CS) and processes a series of experiments.
The results indicate that CRI (Ra) does not affect the CS as distinctly as CCT (WW = CCT<3500K, NW = CCT 3500K≤NW≤5000K, and CW = CCT≥5000K), essentially it is more about the weighting of the spectral power distribution within the circadian sensitivity.
High CRI indeed brings more comfortable visual feelings and it helps with reducing fatigue of the eyes, but we should differentiate clearly that it would be a different story when talking about circadian lighting.
In the book of “LED Lighting: Technology and Perception”, the author talks about the thermal behavior of color semiconductor LEDs.
In a color tuning system like RGBO (red, green, blue and orange), it is completely flexible to design any color points in the CIE diagram and the precise control of the coordinate can be achieved. However, on account of the different thermal performance of each color semiconductor LED, the color stability in the system could be a mess if the temperature is not controlled.
Taking the orange LED as an example from 40°C to 80°C, the peak wavelength moves ~10nm toward longer, converting to the chromaticity coordinate that the shift is far more than 10-step SDCM. Just thinking how much of the deviation when mixing it with R/G/B LED, and each has different thermal behavior respectively, the final light would never be close to your original design if the thermal management is ignored.
In the recent interview from Hortidaily.com, Daniel Han, the director of the business development of Yujileds, stated his viewpoints and introduced the development of LED spectrum in the horticulture lighting industry.
Meanwhile, he also introduced Yujileds featured technologies and products which have been proved as a powerful boost to make our customers successful in their markets.
In the TM-30 measurement of Yujileds AP series LED. The color fidelity index achieves 98, and looking into more details, we see that the 99 CES colors are all rendered above 95, when compared to a standard high CRI LED, even if the CRI is the same, it is still easy to tell the obvious difference of Rf, especially the 99 fidelity scores, not to mention the standard 80 CRI LED.
With the fast development of spectral engineering technology based on LED, it is more and more difficult to judge the color rendition only by CRI. More comprehensive metrics have to be involved as primary or alternative evaluations.
In the hot market of LED horticulture lighting, we have seen some manufactures are promoting their lights with the spectrum below. It is a bit strange compared to a standard LED because of its continuous peaks at ~630nm. Seems like an extra red LED but is not – this spectral pattern indicates that a special LED phosphor named KSF is mixed in the package.
The KSF phosphor helps improve the efficiency significantly – the reason for being chosen to horticulture light where the photosynthetic efficiency is critical. However, due to the material construction, KSF phosphor is weak at resisting humidity, while the plant growth environments are always with high humidity. According to our data, the KSF LED will decay 7% after 1000 hours in a high humidity environment. This is unacceptable for the DLC certification.
But KSF phosphor is widely accepted in the applications like LED backlight of the display screen where the LED is enclosed without humidity. And combining with the β-SiAlON green phosphor, it can achieve over 100% NTSC color gamut.
When applying the technologies to a completely different industry, we should be careful of the practical problems.
In this video, Matt solves 2 keys factors:
● Light source. Undoubtedly, Yujileds super high density LED with 97 CRI LED has applied again. Not only because of the high output, but the point light source also makes the effect as the real sun. Of course, color rendition, white light purity are critical factors as well.
● Blue sky. Matt uses the soap water to simulate the bluish sky, which is quite smart and the effect is so real.
Talking more about the skylight, it is not just for fun, but is a meaningful way to cure SAD (Seasonal Affective Disorder) which is a kind of depressive disorder. According to the statistics, 4%-6% global population may have this issue and another 10% to 20% may have mild SAD. SAD is four times more common in women than in men. A direct reason for SAD is the lack of sunlight, and the concept of skylight is an ideal solution for helping with the treatment.
The ANSI/IES LM-80 test tells the lumen maintenance and the chromaticity shift but it does not indicate the estimation of the shift, while the TM-35-19 should do so.
In the “Lumen and Chromaticity Maintenance Behavior of Light-Emitting Diode (LED) Packages Based on LM-80 Data” from U.S. Department of Energy, several case studies based on different LED materials (ceramic, CSP, polymer) are introduced.
From the analysis, it is found that the TM-35-19 provides reasonable and often conservative estimates of chromaticity shift magnitude, which is particularly important for some applications.
Do you know in the latest CIE technical report 015:2018, 9 typical LED spectra are firstly mentioned and listed. Standard blue-pumped LED, hybrid-type LED, RGB-type LED and violet-pumped LED are all included.
In this article, the authors analyze the colorimetric data of every LED spectrum and the visual comparisons to CIE A, D50 and D65.
In the LED era, we have the full flexibility that is difficult to imagine in the past. The semiconductor LED chip can “grow” in different chemical compositions that create different wavelengths – the colors.
With LED phosphor development, the combinations become numerous with the chips that much more colors are feasible in different spectral patterns.
In CIE 1931, which stands for the entire color range that human eyes can see, the chip+phosphor combination can achieve pixel-level accuracy to any point, no matter the light is for creating or rendering colors.
With Yujileds phosphor and packaging technology, this specialized LED is available now. Extended 50% in 600nm-800nm than a standard LED and the homogeneous spectral power distribution achieves 90+ CRI.
For horticulture, medical lighting and relevant photoelectric device or instrument, this LED provides more possibilities to design the luminaire and fixture, and the enhanced deep red + near-infrared also brings potential benefits for different applications.
The “dual-chip” is indeed helpful to the flexible design of series or parallel, especially in the luminaire like an A60 bulb, and driving at low current with multiple-chip is generally considered as the natural way to improve the efficacy. It is correct in the past few years but with the quick development of the semiconductor LED die, it is no longer the essential method. For specific wavelengths or radiant powers, only talking about efficacy, sometimes applying the “single-chip” with larger size could achieve the same or even better result, and the cost performance is equal or even better.
Color exists due to the interaction of light sources, objects, and the human visual system.
The first requirement is a source of visible electromagnetic energy necessary to initiate the sensory process of vision. This energy is then modulated by the physical and chemical properties of an object. The modulated energy is then imaged by the eye, detected by photoreceptors, and processed by the neural mechanisms of the human visual system to produce our perceptions of color.
Light sources are quantified through their spectral power distribution and standardized as illuminants. (Standard Illuminants)
Material objects are specified by the geometric and spectral distribution of the energy they reflect or transmit.
The human visual system is quantified through its color matching properties that represent the first stage response (photopigment absorption) in the system.
Since the reflectance feature of objects and color perception of eyes do not change during short time, a reliable standardized light source becomes necessary.
It is great to cooperate with BabelColor, the industrial experts in software, measurement and analysis of color. The lamp is made with Yujileds full-spectrum tunable white LED panel, creating the illumination environment close to a natural light source of the same CCT. During the tuning progress, it also simulates the illuminant A, D50 and D65 to render the object’s colors under relevant standards.
In this application note, BabelColor introduces all details including LED assembly, heatsink, bezel, illuminator characterization and conclusions.