Material basis of lighting is light, the human daily life nearly half the time in the sun, which is a natural source. But led street lights price humans need artificial light for illumination. After a long phase of artificial light from the burning wood, oil, gas and produce light, the 1879 Edison invented the incandescent electric light artificial light from entering the era, to achieve a qualitative leap. Existing electric light including incandescent, halogen, represented by thermal radiation source, and gas and fluorescent lamps, high pressure mercury lamp, high pressure sodium, metal halide light sources as the representative of the discharge. In LED solid-state lighting is represented in recent years, the rapid development of lighting technology disciplines.
Photometric lighting disciplines to develop and improve basic around 1760, scientists Lambert (Lambert) has made major contributions to this. This time, due to human has not yet entered the era of electric light, which photometry is leaving the imprint of that era, such as candle (candela). Colorimetry was initially established in the 1930s, after 70 years of perfect. Practice has proved that, photometry, colorimetry suitable for natural light, artificial light, thermal radiation, including lighting, gas discharge light source and other traditional sources of electricity.
In recent years, with advances in solid-state lighting technologies such as LED, LED has received a lot of humanity in the field of visual applications, including display and general lighting, but also a lot of non-application of human vision. If we illuminate subjects defined as "direct application of research source science and technology," the subject, then the visual and non-visual application source applications will be subject areas of study lighting, light vision applications can be called a vision lighting discipline (illumination science), or narrow lighting disciplines, while the lighting disciplines include visual and non-visual applications application called generalized (lighting science).
As a new light source, LED light source is different from the traditional principle. And thermal radiation source depend on the material high-temperature heat radiation, gas plasma gas discharge light source emitting different rely, LED by electrical injection, the electrons and holes injected from the opposite direction to a specific light-emitting area, i.e., the light-emitting layer, and the light-emitting layer composite light. This new LED light principle decision has the following characteristics:
1.1 Small
The LED may be very small, the current 0.5mm * 0.5mm is very easy to do. Due to small size, in three-dimensional space concept LED is expected to meet any demands. You can almost say, in three-dimensional space, LED is a basic element of this element can be used to piece together any shape luminous body. For example, if you need to use 6 LED to piece together a complete luminous body, then we can achieve a variety of possible shapes shown in Figure 1, this is only the plane, as well as three-dimensional three-dimensional case.
1LED can do little
LED small volume of a further advantage is that due to the small size LED, luminous dots smaller. It's almost understandable in optical design for a point source, while the second optical design point source is convenient, therefore, will determine the LED light distribution to fit almost any requirement. Figure 2 is a free-form surface plus LED optical lens to achieve special spot pattern.
2LED add free-form surface to achieve special optical lens flare pattern
1.2 narrow spectrum
In principle from the LED light, LED essentially monochromatic emission spectrum, but because of spectral broadening of a certain width, typically 20 nm ~ 30nm. And now has a band of various monochromatic LED, as shown in FIG.
3 narrow spectrum
Since the LED of monochromatic, therefore, in this space spectrum, using a plurality of LED can be composed of almost any desired spectral shape, and this combination is no loss of efficiency. In other words, LED in this one-dimensional spectrum, LED has the concept as an essential element to achieve the various needs of unlimited possibilities. Traffic lights, backlight RGB system is a typical application.
1.3LED switch short time
LED ns switching time is orders of magnitude. Therefore, this is equivalent to this space at the time, LED has the basic elements and the illumination of the function, that is, on the time scale, LED is arbitrary. This bio below includes humans, plants of light intervention, there will be a lot of applications.
The above analysis of the LED is small, pure spectrum, switching time is short features, which are different from the traditional LED light source, the most important feature, it is these advantages, creating a LED unlimited application possibilities and the possibility of future as a mainstream source. If these three LED unlimited flexibility painting into a three-dimensional space, as shown in Figure 4, then the reality of the vast majority of lighting applications should be able to find the appropriate place in this space.
4LED short switching time
However, unlimited application possibilities of this LED to be a reality for mainstream applications require multiple conditions, including higher compared with the existing light source efficiency, lower prices. Currently on the market has been very easy to buy light efficiency 120lm / W of LED, higher than most of the traditional light sources, LED lamps and some prices have been close to the level of traditional light fixtures. Meanwhile, with the advances in technology LED light efficiency still further improved, prices are rapidly declining. Therefore, LED light source into the mainstream already foreseen. Because LED high degree of flexibility, therefore, LED will have a profound impact on the light source illuminating the material basis for discipline.
LED lighting to expand the connotation of discipline
It should be said, the limitations of traditional light sources, lighting the traditional discipline is to study the visual lighting, because the main purpose of the light source is to help people clear seeing the world, although there are a small number of other uses, but compared to the vision applications, it is much smaller . Therefore, in practice, in fact it is the traditional lighting discipline discipline vision lighting, in which the colorimetric main theories are published by the International Commission on Illumination (CIE) and finalized, therefore, CIE is an authority in this area of the world monopoly in the field say.
However, as mentioned earlier, LED determine the characteristics of it in addition to doing visual purposes, there are many applications are not visual purposes, namely non-visual applications. Now known mainly include agriculture,, medical. If the light used in these areas are known as generalized lighting disciplines, then the connotation that the lighting disciplines will greatly get extended.
2.1LED application in agriculture
LED applications in agriculture, including LED fill light for plants. Because sunlight rely on photosynthesis for plant growth, biological statistics show that the majority of green plants, which contain chlorophyll a and chlorophyll b. Chlorophyll a and chlorophyll b is selective absorption spectrum, as shown.
5LED application in agriculture
Figure 5 shows that contain chlorophyll a and chlorophyll b plants, which absorb green light is very small, green is most reflective, thus appears to be green. The main absorption peaks are 650nm and 440nm two peaks nearby, and chlorophyll a and chlorophyll b wash absorption peaks different but relatively close. Therefore, we can consider the growth of plants is absorbed mainly by these spectra for photosynthesis. Further studies showed that the absorption and photosynthesis of plants to different wavelengths of light are not the same. This from different plants have different colors (i.e., the reflected sunlight portion) can also be understood.
As the LED spectrum has great flexibility, so we can choose the right plants for different spectral irradiation plant, it is conceivable that such plants fill light than conventional light sources would have great efficiency advantages. In this LED applications, establishing different spectral efficiency curve plant photosynthesis is the basis of efficiency, this with the human eye see the function curve is a concept, but for different purposes only. Therefore, with the current Visual Sciences correspondence, whether the plant will produce photosynthesis science?
led street light wholesale in agriculture also includes many aspects, such as pesticides, antibacterial. Such as certain insects to certain spectrum, fungi inhibited, then this inhibition study as great significance. Another type of lighting will be born this research.
LED in the animal breeding is also great utility. Currently LED used to study animal breeding, including chicken, fish and so on. In these applications, light is used to give an animal to create a bright environment, this is similar to human light environment. However, different light environment whether different animals have different growth-promoting effect? If so, then the LED light unlimited flexibility in the manufacturing environment, and thus there may be a different species preferred illumination light environment. This will also be illuminated scientific study.
2.2LED application in medical care
LED applications in medical care, including light therapy and rehabilitation, health care and so on.
Phototherapy (light therapy) principle is: the ability of a specific wavelength of monochromatic light on the biological behavior of cells, while no significant injury. As has long been irradiated with laser light, however, due to its bulky, expensive, and only a small point of light emitted can not be irradiated with a large area of the wound, while in addition to expensive for the limited wavelength tunable laser laser has a value generally, and therefore can not achieve the irradiation light wavelength is preferably, and the laser is an energy inefficient light source, such that these problems in the medical laser applications is limited.
Compared with the laser, LED light source is small, relatively cheap, and has a variety of spectrum, which can be arranged with multiple LED arrays used in large-area wounds irradiation characteristics, through the choice of a different wavelength LED light therapy can be achieved preferably the wavelength, plus LED light efficiency, so that the LED on the light therapy has great potential. LED applications in medical care and rehabilitation is also based on the same reasoning.
In the above medical applications of these LED, there is a LED illumination same preferred problem, that is, for a particular treatment, what type most suitable spectrum? What kind of strength, such as how the exposure mode steady pulse mode or the most appropriate way? How best irradiation cycle? These are all worthy of scientific research are broad subject areas lighting.
LED applications in medical and agriculture on a little different. Application in agriculture, light may be selectively for one or more objects. As far as the effect of a positive, or a positive effect plus one or a few negative effects, such as inhibition of the growth of certain plants. However, in medical applications, due to the human body with a variety of organizations, then LED lighting not only to consider promoting growth of certain tissues, but also consider the damaging effects of a variety of other organizations. Therefore, LED-disciplinary research in medicine and more complex. If this is included in the lighting disciplines, then this part of the lighting disciplines will be a long research process, will produce a series of illuminating subjects branch.
With the development of LED technology, in addition to the above, LED will be in many areas of the birth of a variety of applications. Studies of these applications will also greatly enrich the connotation of lighting research disciplines.
It is worth mentioning that, LED and communications technology combine to produce an LED visible light communication technology, and there is a great prospect. With the development of electronic technology, wireless communication technology has become the main communication. However, wireless communication is the need to allocate channels, and thus the channel will become increasingly nervous. The use of LED fast switching characteristics, when the switching frequency is higher than the human eye blink frequency identification, can be realized by fast switching LED transmission signal, a visible light communication technology is the LED. With the development of LED technology, as the mainstream light source for general lighting around the corner, so the load on the LED lighting LED communication would be a cheap and reliable means of communication at the same time secure. However, the need of special note, in the communication LED, LED is just a carrier. Thus, although the future of which is associated with the lighting of a cross-disciplinary, however, strictly speaking, this does not belong to a part of the lighting disciplines, but rather part of the communication disciplines.
LED lighting subject to change focus
Lighting disciplines is photometry, colorimetry for discipline based. Which photometric Lambert (Lambert) was founded in 1760 by scientists, and colorimetry experienced relatively lengthy process of improvement, from CIE1931, CIE1964, CIE1976 repeatedly CIE chromaticity correction system, while the color of the evaluation index had experienced the same long process until 1974 was basically finalized. However, after nearly four decades since, lighting discipline itself is not much progress. This is mainly because, as the material basis of illumination, including thermal radiation source, a gas-discharge light source, because of its light-emitting principle basically established, and there are no major changes in the basic form of the spectrum, and thus to photometry, colorimetry based lighting disciplines can basically meet the needs of the practice of using these sources of illumination. However, this time, the light source technology is always in progress, despite this progress is slow. The main highlight of the light source is to improve the efficiency, life, color and so on. Specific research is to find a new light-emitting substance or a new excitation light source. Compact fluorescent lamps are very important inventions during this time, which in the 1980s, during the past decade, research studies since then makes it light efficiency, especially in the life of color to get a lot of progress, so that by far the CFL the main sources of indoor lighting. Began in the 1960s HID light source, until the early 2000s has been a hot research sources, and get a lot of progress in the lamp light effect, color, and other aspects of life. Research in this area is also the birth of another important international conferences and organizations in the field of lighting, namely LS: XX Conference and FAST-LS, and LS meeting as the most important international conferences in the field of lighting in addition to CIE.
Therefore, nearly 40 years, has been the focus of the lighting disciplines as the material basis of illumination light source, rather than the lighting itself. However, LED's appearance will change this situation.
In recent years, the United States, Japan, Europe, South Korea and China, including China, Taiwan and other regions, have invested in the government's support for LED research, and LED technology to get a lot of progress, including LED light effect, from ten years ago 10lm / W or so to the current commercial products 130lm / W, while the laboratory sample has reached 300lm / W or more, and the price dropped to an acceptable degree of market fundamentals. At the same time due to the longevity of LED devices, and so has been greatly improved reliability, thus LED in scale space, unlimited flexibility in spectrum space and time and space are increasingly shown its advantages. Currently LED signal display and other areas also include a backlight display applications, has become a mainstream source. In the visual field of lighting, including lighting indoor, outdoor, etc., LED has gained more and more market share, and these could have been the main application areas of traditional light sources. And the field of agriculture, health, communications and other front analysis in recent years, the rapid growth. These are due to the infinite flexibility of the three LED scale space, time and space, due to spectral space. However, because these three unlimited flexibility, LED in all of these applications, in most cases there will be an optimal solution of the problem. And this problem is to conduct research on academic need. Thus, with LED visual and non-visual field applications continue to expand the depth and breadth, has also given a lot of development opportunities lighting disciplines, these are lighting the discipline itself, rather than the material basis of lighting - light.
When the above discussion LED limitless future prospects, are based on three LED unlimited flexibility. However, the current development of LED and LED not fully achieve this flexibility, especially LED spectrum unlimited flexibility. LED current spectral half width of 20 ~ 30nm, and the LED by varying the doping material can achieve most of the visible spectral range. Each center is currently achievable wavelength photoelectric efficiency LED is different, in particular a very low efficiency of the green LED.
6LED unlimited future prospects
Figure 6 is the year 2007 Krames and other external quantum efficiency of map drawing, although in recent years, LED efficiency has been greatly improved, but the efficiency of the green part of the LED remains low, the current commercial products are still below 20%. Therefore, the present LED device to realize a monochromatic LED spectrum unlimited flexibility, i.e., by assembling a plurality of single-color LED to achieve a variety of spectra, and if it contains a green LED, the assembly will lower the spectral efficiency, in order to As for the practical significance will be greatly reduced. Thus, a green LED to improve photoelectric efficiency will be achieved by LED true spectrum unlimited flexibility necessary condition. Before the green LED efficiency has not yet been greatly improved, research to improve the photovoltaic efficiency green LED accent lighting will be a research subject.
No comments:
Post a Comment