Devices or devices that convert electric energy into light energy are called electric light sources.
The study of electric light source began at the end of the 18th century.At the beginning of the 19th century, H. David of England invented the carbon arc lamp.In 1879, T. A. Edison of the United States invented the carbon filament incandescent lamp with practical value, which enabled mankind to enter the era of electrical lighting from the long flame lighting.In 1907, the drawn tungsten wire was used as the incandescent body.In 1912, I. Langmuir of the United States and others conducted research on gas filled incandescent lamps, which improved the luminous efficiency of incandescent lamps, extended their life, and expanded the application range of incandescent lamps.In the early 1930s, the low-pressure sodium lamp was successfully developed.In 1938, Europe and the United States developed fluorescent lamps, whose luminous efficiency and life are more than three times that of incandescent lamps, which is a major breakthrough in electric light source technology.In the 1940s, the high-pressure mercury lamp entered the practical stage.At the end of the 1950s, tungsten halogen lamps with very small volume and light attenuation came out, changing the slow progress of thermal radiation light source technology, which is another major breakthrough in electric light source technology.Developed in the 1960sMetal halide lampAnd high-pressure sodium lamp, its luminous efficiency is far higher than high-pressure mercury lamp.In the 1980s, small diameter compact energy-saving fluorescent lamps, low-power high-pressure sodium lamps and low-power metal halide lamps appeared, making the electric light source enter a new era of miniaturization, energy-saving and electronization.
The invention of electricity has brought mankind into a new era. The birth of electric light source has made a great leap for artificial light source.In the form of electricity, the light source can emit bright light continuously and uninterruptedly.It is also very convenient to control and use the light source.The electric light source has high conversion efficiency, stable power supply, convenient control and use, safety and reliability, and can easily calculate energy consumption with meters. Therefore, it has quickly gained popularity in more than 100 years since its inception.It not only becomes a necessity of human daily life, but also plays an important role in industry, agriculture, transportation, national defense and scientific research·
The development speed of electric light source is faster than any kind of artificial light source before.In particular, modern times, based on the latest science and technology and process equipment, have seen more and better new electric light sources.At present, there are tens of thousands of electro-optic source products in the world, with an annual output of tens of billions. The maximum power of the electric light source exceeds 200kW, while the smallest product is only a few milliwatts.[1]
Classification of electric light sources
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Electric light sources can generally be divided into lighting sources and radiation sources.
The lighting source is an electric light source that radiates the visible spectrum (wavelength 380~780nm) mainly for human vision for the purpose of lighting. It has a wide range of specifications, power from 0.1W to 20kW, and output accounts for more than 95% of the total output of electric light sources.
The radiation light source is not intended for illumination, and can radiate a large amount of ultraviolet spectrum (1~380nm) and infrared spectrum (780~1 × 10sixNm), which includes ultraviolet light source, infrared light source and visible light source for non illumination.
The above two types of light sources are incoherent.There is also a kind of coherent light source, which emits light through excited state particles under the action of stimulated radiation. The wavelength of output light wave ranges from short wave ultraviolet to far infrared. This kind of light source is called laser light source.
Different types of electric light sources have different structures, but generally have the following parts:
① Emitter: filament, electrode, phosphor.
② Emitter shell: glass, translucent ceramic tube, quartz tube.
③ Lead wire: guide wire, core post, lamp holder.
④ Filling materials: various gases, mercury, metals and halides.
⑤ Others: degassing agent, various coatings, insulating parts and adhesives, etc.[1]
Basic requirements for electric light source
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Electric light source converts electric energy into light energy, radiating energy from infrared, visible light to ultraviolet light.There are many kinds of electric light sources with different uses and different technical requirements. But in general, there are mainly the following aspects.
High luminous efficiency
Improving luminous efficiency has always been the main subject of electric light source research.If we divide the electric light source according to the luminous efficiency, we can call the incandescent lamp of 10-20 lm/W the first generation electric light source, the fluorescent lamp and high-pressure mercury lamp of about 50 lm/W the second generation light source, and the high-pressure sodium lamp and metal halide lamp of 80-100 lm/W the third generation light source.Now, the metal halide lamp with ultra-high luminous efficiency and high-pressure sodium lamp, which have been successfully developed internationally, can be regarded as the fourth generation light source with luminous efficiency exceeding 130 lm/W.We believe that with the in-depth study of light sources and the development of science and technology, there will be more efficient fifth and sixth generation new light sources.Improving the luminous efficiency is of great significance for saving energy.
High color rendering
With the improvement of lighting technology, people's requirements for electric light sources have gradually increased. Not only the luminous efficiency should be high, but also the color of the light emitted should be good. The color distortion of the illuminated object is very small, that is, the color rendering of the light source should be high.Especially in some special lighting occasions, such as industrial lighting such as textile, printing and dyeing, and printing, lighting in exhibition halls, museums, shopping malls, and art lighting such as film, television, stage, and photography, the requirements for color rendering of light sources are more stringent.Recently, progress has been made in the development of high color rendering light sources. For example, high color rendering fluorescent lamps that have been successfully developed can have a color rendering index of more than 90.In addition, while maintaining high luminous efficiency, metal halide lamps have made great progress in improving their color rendering.
Long life
The life of light source is an important economic and technical index in artificial lighting.Extended life can reduce the cost of light source and save resources.In addition, it is also very important to simplify the installation, maintenance and use of lighting.Prolonging life is of practical significance only on the premise of ensuring high luminous efficiency and high color rendering.At present, with the adoption of new materials and new processes, the rated life of ordinary incandescent lamps has been extended from 1000h to 2000h, and the life of fluorescent lamps can reach more than 10000h.The service life of high-pressure sodium lamp can reach 20000h, that of metal halide lamp can reach 10000h, and that of tungsten halogen lamp has also increased significantly.
low cost
To reduce the cost of light sources, the first is to reduce the cost of light source materials and replace rare and precious materials with cheap and easily available materials. The second is to optimize the structure of light sources, improve production efficiency, and use efficient automated production lines.
To reduce costs, in addition to considering the simple structure of the light source, it is also necessary to make its accessories and accessories as few and simple as possible. The light source accessories should be miniaturized, lightweight and universal.
Although incandescent lamps have low luminous efficiency, due to their high degree of production automation, the automatic line can produce more than 4000 lamps per hour. At the same time, because of the cheap materials, simple structure, convenient use, and no accessory devices and accessories, compared with efficient gas discharge lamps, incandescent lamps still have strong vitality and a wide market. The total annual output is still the largest among all kinds of electric light sources.Although some new light sources have high luminous efficiency, good color rendering and long service life, they cannot be popularized quickly due to high cost and complicated use, and can only be used in special occasions.
It is conducive to environmental protection, safety and reliability
The hue of ambient lighting will cause visual maladjustment due to the difference in color rendering of light sources.Low pressure sodium lamp and high pressure mercury lamp with poor color rendering are distorted when illuminating objects, which makes the originally colorful and dynamic world dull and dull.People feel depressed when they move under this light. They look ugly, feel uncomfortable, and look sick.This is that light and color "pollute" the environment.
Mercury in mercury lamp and other harmful materials not only pollute the environment, but also directly endanger human health.At present, the mercury used in discharge lamps accounts for about 0.3% of this resource. Although some effective measures have been taken against mercury pollution, such as the use of closed production devices, highly automated unmanned operation, the use of amalgam and mercury compounds and other methods, due to the treatment of mercury light sources (such as waste fluorescent tubes, high-pressure mercury lamps, metal halide lamps, etc.) after use,So far, there is no ideal method.
Some high-intensity gas discharge lamps will free the oxygen in the air when they work, producing a large amount of ozone with special smell, which is harmful to people's nose and throat.This is mainly caused by the short wave ultraviolet radiation of the discharge.When some electric light sources are working, they will radiate a large amount of infrared and ultraviolet rays harmful to human body in addition to visible light.When some gas discharge lamps are working, the electromagnetic waves generated by their accessories have an impact on normal radio communication, broadcasting, television, etc.Some ultra-high voltage discharge lamps will explode due to their quality or operation problems when they are used, damaging people.
Therefore, we need light pollution free green light sources in our life.This needs to take effective measures such as using environment-friendly materials and increasing radiation protection measures in the manufacturing process of light sources, and pay enough attention to them in use to eliminate unsafe factors.[1]
Development trend
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It is mainly to improve the luminous efficiency, develop efficient and energy-saving light sources with small size, improve the color rendering performance of electric light sources, and extend the service life.The specific way to achieve the above goal is to develop new materials, adopt new processes, further study new light-emitting mechanisms, and develop new electric light sources. The most realistic way is to improve the manufacturing technology of existing electric light sources and use new production equipment with good automation performance.
