The miner's lamp is very important for the underground work of coal mine workers. Compared with the traditional miner's lamp source, LED has the advantages of high luminous efficiency, long life, small volume, and low junction temperature during operation, which is not easy to ignite explosive gas. Approximate point light source, which is convenient for the design of optical system, makes LED miner's lamp become the hot spot of current miner's lamp development. In view of the particularity of LED light source, the design of LED miner's optical system is reflective, transmissive, etc. At present, LED miner's lamp has shortcomings such as poor light collecting performance, large lens volume and high optical loss in practical applications. This paper proposes a new type of LED miner's lamp optical system, which provides the necessary supplement for the optical design method of existing LED miner's lamp.
Second, the existing LED miner's lamp optical system
The national standard "MT 927-2004 KL miner's lamp" stipulates that the miner's lamp with a rated capacity of 7Ahd has a central illumination of 350 lx at 1 m. To meet this requirement, an LED light source with a light intensity distribution similar to the Lambertian distribution requires an efficient optical convergence system to reduce stray light. The comparative study of different configurations of LED miner's optical systems is as follows.
Figure 1 shows a conventional catadioptric reflector. The cylindrical lens and the reflector are used together to distribute all the light into parallel light. However, the height and diameter of the reflector are large, and the lens can be improved in structure.
2 is a total reflection collimating lens, which has the advantages of compact structure, no need for an inner plating reflective layer, and is convenient for forming a luminaire, but the concentrating performance of the lens is lower than that of the existing refracting reflector, and the structure of the lens also exists. Unnecessary material waste and volume can be further reduced.
Third, the optical system design of the new LED miner's lamp
In order to solve the defects of high reflector and large refractor in the existing LED miner's optical system, this paper proposes an optical system of a new LED miner's lamp, which is mainly composed of a novel free-form curved reflector, including a refractor and a free-form surface. reflector. As shown in Figure 3.
1. Refractor design
The refractor includes a free-form surface type refractive surface, a zigzag curved surface, and a concave hemispherical shell. The refractive surface emits 0Â° to 20Â° and 20Â° to 40Â° light rays from the light source to form a parallel light of 0Â°; zigzag type The curved surface is located inside the upper part of the refractor for reducing the volume of the refractor; the recessed hemispherical shell is located at the bottom of the refractor and matches the bottom of the reflector to support the refractor.
As shown in Fig. 4, point O is the LED light source; Î¸i and Î¸i+1 are the angles between the ith and i+1 rays emitted by the light source and the Y axis; OM is the edge ray of the refracting surface; point A (xi, Yi) and B (xi+1, yi+1) are the intersection of the ray and the lens bus; Î²i is the angle between the tangent and the horizontal line at point A; Î±i is the incident angle at point A; Î´i is the exit angle at point A.
For more information, please refer to the "High-tech LED - Technology and Applications" January issue
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