Optical Design Of Uniform Illumination System Based Large-size LED Light Source

At present, the government has been vigorously promoting energy conservationand emission reduction. In the area of lighting, LED is, with high brightness, lowpower consumption, pollution-free, long life and so on, increasingly favored. Inrecent years, optical design of lighting system based on LED light sources was paidmore and more attention. Because LED light intensity distribution and other opticalproperties is different from the traditional light source, LED-based optical design, notlike the traditional optical design, cannot be suitable for the imaging optics theory.When carry on LED-based optical design, we can, according to the light intensitydistribution, obtain the requested light angle through designing optical system tocontrol ray trend. Currently most optical designers assume LED to a point lightsource, but for a large-size LED light source, such as integrated packaging LEDsource and LED array, this supposition can’t be suitable. Therefore, the research onthe optical design of a large-size LED source not only has theoretical value but alsopractical significance.This paper provides two optical design method of large-size LED light source. Onemethod is how to design rotationally symmetric lens for integrated packaging LEDlight source. According to edge-ray theory, oppositely extend the ray line of surceedge and lens edge to intersect at a point. Define the point of intersection as pointsource, and then combine with the Snell law of refraction in vector form and iterationmethod, calculate the lens’free curve. Through the software modeling and simulation,the results show that this method designing the rotationally symmetric lens canrealize a uniform circular facula.The other method is how to design optical system for LED-arrays to realizefar-field large area uniform illumination. This paper takes the circular LED-arrays asthe light source and the main theoretical basis is the principle of image optics andnon-image optics. We establish the model of the circular LED-arrays and determinethe near-field location of the uniform illumination surface according to the theoreticalcalculations. Define the near uniform illumination surface of the circular LED-arrays as the virtual surface light source. In order to achieve a far uniform illumination,design spherical lens or aspherical lens, which enlarge the image of the virtual surfacelight source. Then design reflector, which collimated the ray, so that collectsufficiently light source. Through optic software simulation, the results prove thefeasibility of this design method, achieving the far uniform illumination of the largesize light source.