Led lighting will be widely used in road lighting first. This kind of inference is based on the long life, high efficiency and high light utilization efficiency of LED. Many people have made many attempts to apply LEDs in road lighting, but it is not difficult to see that
LED street lights have not been well developed in the past two or three years. The reasons are: high cost, short life, poor lighting performance (even Poor).
Fortunately, the upstream industry is developing rapidly. The improvement of LED chip light efficiency and price reduction make LED road lighting more and more close. The professional optical design also greatly improves the lighting effect. More manufacturers are making it. In this attempt, this paper proposes a new optical solution - a separate unit of reflectors - aimed at finding a new LED road lighting solution.
Compared with lenses, reflectors are characterized by low cost, high efficiency, and easy assembly.
The common lens material is PMMA. The current technology PMMA material has a transmittance of only 94%. After the lens is made into a lens, there is usually more extra light loss due to the effect of the refraction. The following examples illustrate:
Set a light source to produce 50,000 rays:
When there is no PMMA translucent plate, the efficiency is 100%, and now an ideal state PMMA transparent plate is set in front:
The efficiency has become 94.337%.
(Note: 16808 Rays appears in the figure because a light passing through the interface between PMMA and air may refract and reflect at the same time, thus increasing the amount of light, but a certain loss from the energy point of view.)
If the PMMA material is made into a lens, the loss is greater. The following is an example of a PMMA material lens that is common in the market. (In view of the total light leakage on the back of the lens, the actual light leakage is not available, so the entire system is provided on the back. Absorbing the substrate to enhance the rigor of the data):
Lens outline
Analysis of stray light after passing light through a lens
The lens efficiency is actually only 86%
The relative analysis of the reflective optical system is relatively easy. After analyzing the distribution of the light energy of the light source, the lens suitable for road illumination is designed by redistribution.
Light source Lambertian light mode (ie common Lumileds, CREE , Edison LED), combined with the design of the reflector, the two angles of light output are 50 degrees and 120 degrees, respectively, that is, the street lamp placed at 10 meters pole height can form about 12 × on the ground A uniform spot of 30 meters increases/decreases the number of cells according to the illuminance requirement.
1, light trajectory:
2, single 1W lighting effect map (illuminance distribution):
3. The following is the lighting effect of simulating a section of road:
The road is 15 meters wide, with symmetrical lamp, 10 meters pole height, 32 meters pole distance, the installation angle of the lamp is 5 degrees, and the cantilever length is 1.5 meters. The surface of the road is evenly illuminated, 90% of the light is concentrated on the road, the roadside illumination is gradually decreasing, and there is no hard light edge, which will not cause the driver's visual discomfort.
Efficiency analysis:
The illuminating light passing through the reflective system is divided into "direct light" and "reflected light", that is, part of the light does not need to be directly scattered through the reflective wall, and another part of the light is irradiated to the corresponding position through the reflective wall.
Set the reflective wall to "Perfect Absorber", and then according to the exit efficiency, you can get how much light does not need to be directly irradiated through the optical system:
It can be seen that 41.88% of the light in the optical system is directly irradiated, without going through the optical system, that is, the energy loss is 0, and another 58.12% of the light needs to be reflected by the reflective wall, and the reflection efficiency depends on the reflective wall material and processing. Process. By reinforced aluminum or silver mold, the reflection efficiency can reach more than 90%, so the efficiency of the reflective system can reach and exceed the following values:
41.88%+58.12%×90%=94.19%
It is much higher than the 86% efficiency of the lens method, that is, 100lm light can be used to 94.19~98.84lm.
The biggest advantage of this reflective bowl is its high efficiency. The use of light source is a common Lambertian light-emitting mode LED. A single light source achieves such an effect rather than a combination of arrays, so the number of LEDs can be increased or decreased according to the power of the street lamp.
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