26.02.2015
As a light material factory of China, we offer the latest led raw materials to buyers and customers all over the world. Color quality is one of the key challenges facing light-emitting diodes (LEDs) as a general light source. Sources: Manufacturer datasheets for Cree XLamp 7090 XR, Lumileds Luxeon K2 Emitter, Luxeon Warm White Emitter, and Osram Opto OSTAR-Lighting. Visible spectrum, which is also known as visible light or simply light, is a portion of the electromagnetic spectrum that the human eye can perceive.
It lies between the Ultra-violet radiation and Infra red radiation of the electromagnetic radiation [EMR]. Orange color corresponds to the wavelength of 595 -620nm.Red color corresponds to the radiation of minimum frequency (4 x 10^14Hz) and maximum wavelength (760nm). The visible spectrum is a subset of the electromagnetic spectrum that is visible to the human eye. The range of all possible frequencies of electromagnetic radiation is known as electromagnetic spectrum.
Out of seven colors Red, green and blue are known as "primary" colors as their combination produced white color. Visible spectrum is also known as color spectrum as there are seven colors in the color spectrum, violet, indigo, blue, green, yellow, orange and red (VIBGYOR). Of the radiation energy to which we are exposed on a daily base, we are only aware of a small part as light or warmth.
Insects and other arthropods, such as Limulus, the horseshoe crab, often have a compound eye consisting of ommatidia (Eckert, Fig. Very small animals, such as insects, can't use a lens type system due to optical diffraction. Our eye and the eye of the octopus both have a lens which produces an image on a retina which is comprised of an array of photoreceptive cells.
Stomatopods (Mantis shrimp, etc.) have up to 16 different types of receptor cells that are each sensitive to different regions of the UV and visible spectrum. All text and images, not attributed to others, including course examinations and sample questions, are Copyright, 2012, Thomas J. Solar radiation refers to the electromagnetic radiation that reaches the Earth from the Sun. Figure 1 clearly shows that the majority of solar radiation occurs in the short-wave visible and ultraviolet portions of the electromagnetic spectrum.
Ultraviolet (UV) radiation makes up a very small part of the total energy content of insolation, roughly 8%- 9%.
As solar radiation passes through the earth's atmosphere, some of it is absorbed and scattered (25%) by air molecules, small airborne particles, water vapour, aerosols and clouds. It is the scattered component that makes the sky look bright and provides the ambient diffuse daylighting used in buildings.
If you look closely at Figure 1 you will notice significant differences between the spectral content of the radiation reaching the outer atmosphere and that actually reaching us on the surface. The Earth's orbit around the Sun is not circular but elliptical, meaning that it is closest to the Sun in late Summer and farthest away in late Winter. This has an effect because the lower the Sun is in the sky, the more of the Earth's atmosphere the solar radiation has to pass through in order to reach the surface, thus the more scattering and absorption it is subjected to. Figure 4 - When the sun is lower in the sky in winter, solar radiation must travel further through the atmosphere than in summer. The solar radiation that passes directly through to the earth's surface is called Direct Solar Radiation. Anti-Reflection Coating (AR)This type of Optical coating when applied to the surface of a substrate reduces reflection and minimizes light loss thus improving contrast of the image due to the elimination of stray light.
V-coat AR : Type of AR coating which is normally narrow and reflectance curve is shaped like a letter V with the lowest reflectance occurring at the design wavelength. Dual Band AR : Type of AR coating where transmission is optimized at 2 wavelength of interest. Bandpass filters isolate specific regions of the spectrum, simultaneously providing high transmission of desired energy, and deep rejection of unwanted energy. Type of filters which blocks or rejects a specified wavelength range and transmits another.


This paper reviews the basics regarding light and color and summarizes the most important color issues related to white light LEDs. Instead, LEDs emit light in a very narrow range of wavelengths in the visible spectrum, resulting in nearly monochromatic light. When combined with a yellow phosphor (usually cerium-doped yttrium aluminum garnet or YAG:Ce), the light will appear white to the human eye. Electromagnetic radiation in wavelengths from about 380 to 770 nanometers is visible to the human eye. Example of a Typical IncandescentSpectral Power Distribution Incandescent, fluorescent, and high-intensity discharge (HID) lamps radiate across the visible spectrum, but with varying intensity in the different wavelengths. Phosphor-converted chips are produced in large volumes and in various packages (light engines, arrays, etc.) that are integrated into lighting fixtures. Merely wave lengths in a very small interval from 380 to 780nm are normally perceived by humans as visible light.
The wavelength range from about 390 to 750nm and frequency, 400–790Hz is the part of visible spectrum.
Ita€™s the distribution of electromagnetic radiation emitted or absorbed by a given object.
The highest wavelength of radio wave used for radio communication, while the gamma radiations have minimum wavelength and maximum frequency.
They cause a number of photo-chemical processes, have a brief pigment-building effect (sun tan) and can indirectly cause DNA damage and melanomas. McNeill Alexander (Edward Arnold), shows a diagrammatic representation of a compound eye with the individual ommatidia. The octopus eye uses a lens imaging system but using a retina with receptor cells in front. Some cells in the leaf veins and petioles of plants are sensitive to the direction of light, not just its intensity. Herbert and may not be used for any commercial purpose without the express written permission of Thomas J. As discussed in the colour temperature topic, the greater the temperature of an object, the shorter the wavelength of its radiant emissions.
There is some long-wave component of infrared, however large bands of this are absorbed by gasses and particles within the upper atmosphere. Some of the radiation is reflected straight back out into space (usually around 20% but much more with increased cloud cover) whilst the rest arrives somewhere on the Earth's surface. Sometimes less than 50% of the solar radiation arriving at the outer atmosphere actually reaches the Earth's surface. Without it, the sky would look just as black as it does at night, with the sun being a very-very large and bright star occasionally passing through it.
Blue light arrives from all directions after scattering, whilst red and yellow light arrives almost directly from the sun.
This is due to the absorption of some of the radiation when a gas molecule or particle retains some of this energy as heat. Also, the greater the angle the direct radiation makes with the ground, the greater the surface area its energy is spread over, reducing its intensity and its heating capacity as per the Cosine Law. Whilst a cloudy sky can actually increase the amount of diffuse solar radiation, a heavy rain cloud can reduce the direct component to almost zero. The radiation that has been scattered out of the direct beam is called Diffuse Solar Radiation. The general concept is usually based on the periodic layer system composed from two materials, one a high index and the other a low index material. Application can be found on optical lenses, eye glasses, cover window or display glasses, photographic lenses and other application that requires maximum light transmission.
MgF2 is the most popular low index material which performs better on high index glass substrates.
This is why LEDs are so efficient for colored light applications such as traffic lights and exit signs.
A more recently developed approach uses an LED emitting in the near-UV region of the spectrum to excite multi-chromatic phosphors to generate white light.The RGB approach produces white light by mixing the three primary colors red, green, and blue.
The spectral power distribution (SPD) for a given light source shows the relative radiant power emitted by the light source at each wavelength.
RGB systems are more often custom designed for use in architectural settings.Typical Luminous Efficacy and Color Characteristics of Current White LEDsHow do currently available white LEDs compare to traditional light sources in terms of color characteristics and luminous efficacy?


In other words, visible spectrum lies between the frequencies of the ultraviolet rays and infrared waves. Mixing of secondary colors produced tertiary Colors.When white light passes through a prism, it gets dispersed into the colors of the optical spectrum. This varies by around ±2% due to fluctuations in emissions from the Sun itself as well as by ±3.5% due to seasonal variations in distance and solar altitude. Once the radiation arrives at the surface, some of it is immediately reflected back into the sky. It just happens that most of the particles in the atmosphere that are responsible for scattering are around 0.5 microns in size. There are noticeable dips in the solar spectrum that coincide with the absorption characteristics of different gasses.
As there is generally an increase in cloud activity during the colder or wetter months, these factors combine to produce a significant seasonal variation in available solar radiation. The addition of the direct component of sunlight and the diffuse component of daylight falling together on a horizontal surface make up Global Horizontal Solar Radiation.
An example of Long-Wave Pass filter is a Cold Mirror used to cool a Projection System by letting Infra Red (in form of heat) to pass through the filter. Color quality of the resulting light can be enhanced by the addition of amber to “fill in” the yellow region of the spectrum. Incandescent sources have a continuous SPD, but relative power is low in the blue and green regions.
Standard incandescent A-lamps provide about 15 lumens per watt (lpw), with CCT of around 2700 K and CRI close to 100. With increasing wavelength the color impression changes to blue, green, yellow, orange and finally red.
This type of radiation is used for therapeutic purposes, amongst other things, since it has an anti-rachitic effect. In addition to the spectrum of solar radiation there is a spectrum of terrestrial radiation that fills out the far-infrared range spanning from 3 to 75mm. This amount depends on the nature of the actual surface - fresh snow can reflect up to 95% whilst desert sands reflect 35-45%, grasslands 15-25% and dense forest vegetation 5-10%. As radiation with longer wavelengths simply ignores these particles, higher frequency (shorter wavelength) radiation tends to be scattered more. Whilst some of this absorbed heat finds its way to the surface as long-wave radiation, the vast majority is simply re-radiated back out into space.
Both mean that the path of the Sun through the sky changes significantly throughout the year.
An example of a Short-Wave Pass filter is a Hot Mirror that transmits visible light and reflects the heat.
The potential of LED technology to produce high-quality white light with unprecedented energy efficiency is the impetus for the intense level of research and development currently being supported by the U.S.
The typically “warm” color appearance of incandescent lamps is due to the relatively high emissions in the orange and red regions of the spectrum. ENERGY STAR qualified compact fluorescent lamps (CFLs) produce about 50 lpw at 2700-3000 K and CRI at least 80. Radiation differs through frequency, for example, radio waves are of long wavelength, while visual radiation is in the short wave range.
These are basically the heat radiating from the surfaces of materials that have been warmed by the sun.
This is what makes the sky appear blue - as lower frequency red and yellow light pass almost directly through whilst blue light is bounced about all over the place. Typical efficacies of currently available LEDs from the leading chip manufacturers are shown below.
The frequency range of UV radiation only includes a very small part of the electromagnetic range.



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Comments Short wave uv wavelength units

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    For Radio Control Model airplanes that is like a porous solid.