Source： RUI JIN
As we all know, the wavelength range of the visible light spectrum is 380nm to 760nm, which is the seven colors that the human eye can feel - red, orange, yellow, green, blue, blue, and purple. However, these seven colors of light are each A monochromatic light.
For example, the red light emitted by the LED has a peak wavelength of 565 nm. There is no white light in the spectrum of visible light, because white light is not a monochromatic light, but composite light synthesized by a variety of monochromatic light, just as sunlight is a white light synthesized by seven monochromatic lights, and in a color TV set White light is also synthesized from the three primary colors red, green and blue.
Thus, to make the LED emit white light, its spectral characteristics should include the entire visible spectral range. However, it is impossible to produce LED with this performance under the process conditions. According to people's study of visible light, the white light visible to the human eye requires at least two kinds of light mixing, namely two-wavelength light emission (blue light + yellow light) or three-wavelength light emission (blue light + green light + red light) . Both of the above two modes of white light require blue light, so ingesting blue light has become a key technology for manufacturing white light, namely, the "blue light technology" pursued by major LED manufacturing companies. Internationally, there are only a few companies that have mastered "blue light technology." Therefore, the promotion and application of white LEDs, especially the promotion of high-brightness white LEDs in China, is still a process.
For general illumination, in the process structure, white LEDs are usually formed by two methods. The first is the use of "blue light technology" to form white light with a phosphor; the second is a variety of monochromatic light mixing methods. Both of these methods have succeeded in producing white light devices. The first method to generate white light is shown in Fig. 1. In the figure, the LED GaM chip emits blue light (λp=465 nm). It is encapsulated with a YAG (yttrium aluminum garnet) phosphor and emitted when the phosphor is excited by blue light. As a result of the yellow light, blue light and yellow light are mixed to form white light (the structure constituting the LED is shown in FIG. 2). The second method uses chips of different colors to be packaged together, and the white light is generated by light mixing of each color.
To illustrate the characteristics of white LEDs, first look at the status of the light source used. Incandescent and tungsten halogen lamps have a luminous efficacy of 12 to 24 lumens/watt; fluorescent lamps and HID lamps have an efficacy of 50 to 120 lumens/watt. For white LEDs: In 1998, the efficacy of white LEDs was only 5 lumens per watt. By 1999, it had reached 15 lumens per watt. This indicator is similar to general household incandescent lamps, and in 2000, the efficacy of white LEDs. Has reached 25 lumens / watt, this indicator is similar to tungsten halogen lamp. Some companies predict that by 2005, the luminous efficiency of LED can reach 50 lumens/watt. By 2015, the luminous efficiency of LED is expected to reach 150 to 200 lumens/watt. At that time, the white LED's operating current can reach the ampere level. This shows that the development of lighting sources for white LED writers will become a possible reality.
Although incandescent lamps and tungsten halogen lamps for general illumination are inexpensive, they have low luminous efficacy (thermal effects of lamp consume power in vain), short life span, and large maintenance workload. However, if white LEDs are used for illumination, not only high luminous efficiency, but also longevity Long (more than 10,000 hours of continuous work time), almost no maintenance.
The LED light source has the advantages of using a low voltage power supply, low energy consumption, strong applicability, high stability, short response time, no pollution to the environment, multi-color emission, etc. Although the price is more expensive than the existing lighting equipment, it is still considered to be Inevitably replace existing lighting devices.
The intrinsic characteristics of the LED determine that it is the ideal light source to replace the traditional light source. It has a wide range of uses.
The LED is basically a very small wafer that is encapsulated in epoxy, so it is very small and very light.
Low power consumption
The LED consumes very low power. In general, the operating voltage of the LED is 2-3.6V. The operating current is 0.02-0.03A. This means that it consumes no more than 0.1W of electricity.
With an appropriate current and voltage, the LED can have a lifetime of up to 100,000 hours
High brightness, low heat
The LED is made of non-toxic materials. Unlike fluorescent lamps, mercury can cause pollution, and LEDs can also be recycled.
strong and sturdy
The LED is completely encapsulated in epoxy, which is stronger than bulbs and fluorescent tubes. There are no loose parts in the lamp body. These features make the LED unbreakable.
The biggest advantage of LED lights is energy saving and environmental protection. The luminous efficiency of light reaches 100 lumens/watt or more, ordinary incandescent lamps can only reach 40 lumens/watt, and energy-saving lamps also linger around 70 lumens/watt. Therefore, with the same wattage, LED lights will be much brighter than incandescent and energy-saving lamps. 1 watt LED lamp brightness equivalent to 2 watts of energy-saving lamps, 5 watts LED lamp 1000 hours of power consumption of 5 degrees, LED lamp life can reach 50,000 hours, LED lights without radiation.
Color temperature color
The color temperature of the light source:
People use the absolute temperature of the complete radiator that is equal to or close to the color temperature of the light source to describe the color table of the light source (the color that the human eye sees when looking directly at the light source), also known as the color temperature of the light source. The color temperature is expressed as an absolute temperature K. Different color temperatures can cause people to respond differently to emotions. We generally divide the color temperature of light sources into three categories:
The color temperature of the warm color light is below 3300K. The warm color light is similar to the incandescent light color, and the red light composition is more, giving a feeling of warmth, health, and comfort. It is suitable for homes, houses, dormitories, hospitals, hotels and other places, or temperature Relatively low place.
Warm white light
Also called the middle color, its color temperature is between 3300K-5300K. Warm white light and soft light make people feel happy, comfortable and peaceful, suitable for shops, hospitals, offices, restaurants, restaurants, waiting rooms and other places.
Also called daylight color, its color temperature is above 5300K, the light source is close to natural light, has a bright feeling, and makes people concentrated. It is suitable for offices, conference rooms, classrooms, drawing rooms, design rooms, library reading rooms, exhibition windows, etc. place.
The degree to which the light source presents the color of the object is called the color rendering, that is, the degree of realisticness of the color. The light source with high color rendering performs better on the color, and the color we see is also closer to the natural color.
Low light sources perform poorly on color, and the color deviations we see are also larger.
Why is there a difference in color rendering? The key lies in the spectral characteristics of this light. The wavelength of visible light is in the range of 380nm to 780nm, which is what we see in the spectrum: red, orange, yellow, green, blue and blue. In the range of purple and violet light, if the ratio of the colors of light contained in the light emitted by the light source is similar to that of natural light, the colors seen by our eyes will be more realistic.
We generally use the color rendering index to characterize color rendering. The standard color is defined by a standard light source with a color rendering index of 100. When the color scale is irradiated by the test light source, the degree of visual distortion of the color is the color rendering index of such a light source. The larger the color rendering index, the less the distortion. On the contrary, the greater the distortion, the smaller the color rendering index. Different places have different requirements for the color rendering index of the light source. In the International Lighting Association, the color rendering index is generally divided into five categories:
Category Ra Applicability
1A >90 Art galleries, museums and printing industries and places
2B 80-90 Family, restaurant, advanced textile technology and similar industries
2 60-80 Office, School, Outdoor Street Lighting
3 40-60 heavy industry factory, outdoor street lighting
4 20-40 Outdoor Road Lighting and Some Demanding Places
Common fluorescent lamp
There is a filament on both ends of the fluorescent lamp. The lamp tube is filled with trace amounts of argon and thin mercury vapor. The inner wall of the lamp tube is coated with fluorescent powder. When the gas between the two filaments conducts electricity, it emits ultraviolet rays to make the fluorescent powder soft. Visible light.
Fluorescent lamp working characteristics: When the lamp begins to ignite, it needs a high voltage. When the lamp is normally radiating, only a small current is allowed to pass. At this time, the voltage across the lamp tube is lower than the voltage of the power supply.
LED fluorescent lamp
Led fluorescent lamps are characterized by high quality, durability and energy saving. The projection angle adjustment range is large, and the brightness of 15W is equivalent to ordinary 40W fluorescent lamps. High temperature resistance, moistureproof and waterproof, leakproof. The use of voltage: 110V, 220V optional, optional glass or PC cover material. The lamp head is the same as ordinary fluorescent lamps.
LED fluorescent lamp uses the latest LED light source technology, digital design, saving up to 70%, 12W LED daylight lighting is equivalent to 40W fluorescent tube (for ballasts and starter, 36W fluorescent lamp real consumption Electricity is 42W to 44W). The lifetime of LED fluorescent lamps is more than 10 times that of ordinary lamps, and it is almost maintenance-free. There is no need to frequently replace lamps, ballasts, and starters. The green and environmentally friendly semiconductor electric light source has soft light and pure spectrum, which is beneficial to the user's vision protection and health. The 6000K cold light source gives people a visually cool feeling. The humanized illumination difference design helps to concentrate and improve efficiency.
Compared with ordinary fluorescent lamps, LED fluorescent lamps have the following advantages:
1, energy saving. 2, long life LED lights. 3, Applicability is good, because a single LED's small size can be made into any shape. 4, the response time is short, is the response time of ns (nanoseconds) level, and ordinary lamps and lanterns are the response time of ms (milliseconds) level. 5, environmental protection, no harmful metals, waste is easy to recycle. 6, Colorful, pure color, spectral range, and can be mixed into three colors of red, green and blue into a colorful or white light.
Disadvantages: 1, expensive. 2. There is still a big gap between the light efficiency and the theoretical light efficiency that can be universally achieved. 3, there is still a big gap between the lifespan and theoretical life (10w hours) that can be achieved. 4, there is still a certain amount of heat. 5, light failure can also be greatly reduced.
However, these shortcomings can be overcome through the improvement of the process, so even if the LED light source can not completely replace the existing traditional light source, but with the development of technology, the future must be the world of LED.
Application in Advertising Industry
Mainly in large-character advertising applications. Mostly for large-sized characters and small lights, increase the display effect.