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Yan X.,CAS Xian Institute of Optics and Precision Mechanic | Yan X.,University of Chinese Academy of Sciences | Yang J.,CAS Xian Institute of Optics and Precision Mechanic | Zhang G.,Xian ZKMT Electronic Technology Equipment Co. | And 4 more authors.
Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering | Year: 2012

According to the design principle of ideal light source, a method to obtain freeform surface generatrix based on energy compensation and coordinate iteration was proposed. Freeform surface LED reflectors for uniform illumination were designed. Firstly, the geometrical model of illumination system was established in two-dimensional coordinate system, in order to get uniform illumination. The directly incident energies were compensated by the reflected rays. Concretely, the rays were refected into the upper verge of the reflector to the verge area of the target plane, and go down to the bottom of the reflector along with the rays, approaching the middle of the target plane. Based on Snell equation and geometrical relation, choosing the point on the top of freeform surface generator as the initial point, the coordinates of all points on the freeform surface generator were obtained by iteration method, which could be rotated or extended into the freeform surface. The simulations of the designed LED reflectors with Tracepro software show that the illumination uniformity of either the circle or the square target plane is higher than 85%, and the energy efficiency which was affected only by the LED's emitting angle and the reflectivity of the reflector surface can be high. These peculiarity enable LED light source to be applied in wide range lighting system. Source

Yan X.,CAS Xian Institute of Optics and Precision Mechanic | Yan X.,Chinese Academy of Sciences | Yang J.,CAS Xian Institute of Optics and Precision Mechanic | Bu F.,CAS Xian Institute of Optics and Precision Mechanic | And 2 more authors.
ICEOE 2011 - 2011 International Conference on Electronics and Optoelectronics, Proceedings | Year: 2011

Traditional LED (light emitting diode) packaging always adopts hemisphere lens, and can ensure high light output efficiency, but its radiation pattern yields Lambert distribution and is non-uniformity. To enable LED light sources be applied in uniform illumination system, a method to obtain freeform LED lens based on energy equipartition and tangent iteration is proposed. Firstly, according to the Lambertian distribution of LED light intensity and its rotationally symmetric peculiarity, the LED emission angle is divided into N parts in Two-dimensional coordinate system, and the energy contained in each part is equal; Secondly, the target plane is divided into N equal areas along its radii, and the discrete points are corresponding to the N parts of emission angle. So that if the energy in each divided solid angle is controlled to illuminate the equal divided area, the illumination of each corresponding micro-belt on the target plane will be uniform; Finally, to avoid the total reflection of large emission angle rays, the designed lens will refract the rays with 0∼450 emission angle and reflect the rays with 450∼900 emission angle. Choosing an initial point on the freeform generatrix, and using Snell equation and tangent iteration method, the coordinates of all points on the freeform generatrix are obtained, which could be rotated into the freeform surface of the lens. The simulation results using the designed LED lens show that for a rotationally symmetric target plane the illumination uniformity is near to 90% and the energy efficiency is higher than 95%. © 2011 IEEE. Source

Yan X.-T.,CAS Xian Institute of Optics and Precision Mechanic | Yan X.-T.,University of Chinese Academy of Sciences | Yang J.-F.,CAS Xian Institute of Optics and Precision Mechanic | Xue B.,CAS Xian Institute of Optics and Precision Mechanic | And 3 more authors.
Optoelectronics Letters | Year: 2013

A novel element for collimating LED light is designed based on non-imaging optics. It is composed of a refraction lens and a reflector. The upper surface of the lens is freeform and calculated by geometrical optics and iterative process. The lens makes the rays in the range of 0°-45° from the optical axis collimated. The rays in the range of 45°-90° from the optical axis are collimated by the reflector. The inner surface of the reflector is parabolic with its focus located in the LED chip. The designed element is applicable to LED source of any emitting type. For a certain application, the simulation results of the designed element in Tracepro show that it has a very compact structure and good collimating performance. Just investigating the loss in the lens surfaces, this element has high light output efficiency of nearly 99%. Most lighting area radii are no more than 20 mm when the illuminated plane is 5 m away from the LED source. © 2013 Tianjin University of Technology and Springer-Verlag Berlin Heidelberg. Source

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