Abstract
A reflector-based light-emitting diode (LED) luminaire structure that can achieve a large cut-off angle for general lighting is presented in this work. The proposed lighting unit mainly consists of a spherical reflector and a primary packaging lens that contains an aspheric surface and a spherical surface. The light rays emitted from the LED light source are well controlled by the spherical reflector and the aspheric surface of the lens for the purpose of obtaining a uniform illumination on the target surface. Both the ideal Lambertian LED and non-Lambertian LED light sources were employed to validate the proposed structure and the performance of the designed lighting units was analyzed by optical simulation. The results show that the light utilization efficiencies and the estimated uniformities are 92.96% and 91.11% for ideal Lambertian LED-based lighting unit and 93.31% and 91.64% for non-Lambertian LED-based lighting unit, respectively. Further analysis shows that the tolerances of horizontal, vertical, and rotational deviation of the both lighting units were about 2.0 mm, 1.0 mm, and 1.0°, respectively.
Highlights
After years of development, light-emitting diodes (LEDs) have been widely used in the fields of indoor lighting, road lighting, automobile headlights, backlight of liquid crystal display, and so forth [1,2,3,4]
The LED light source is immersed into the primary lens and positioned at the origin O of the coordinates [15,16,17], O is the center of the spherical reflector, and R denotes the radius of the reflector
A reflector-based LED lighting unit structure that can achieve a large cut-off angle for general lighting has been discussed in this work
Summary
Light-emitting diodes (LEDs) have been widely used in the fields of indoor lighting, road lighting, automobile headlights, backlight of liquid crystal display, and so forth [1,2,3,4]. A secondary optical element is generally needed to redistribute the light energy emitted from LED to meet the specific illumination requirements. The optimal cut-off angle of the reflector is limited by the LIDC of the LED light source for the case of uniform lighting [11]. For an ideal Lambertian LED, the largest cut-off angle of the freeform reflector is about 45∘ for uniform illumination [12]. As the cut-off angle of the reflector increased larger than 45∘, the uniformity will deteriorate Such restriction put up some obstacles in using LEDs in the field of general lighting where the cut-off angle of the lighting unit typically defined between 55∘ and 65∘ [12, 13]
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