Freeform lens design for light-emitting diode uniform illumination by using a method of source–target luminous intensity mapping

Abstract

We present a freeform lens for application to LED uniform illumination. This lens, which is designed with a method of simple source-target luminous intensity mapping, can produce irradiance uniformity of greater than 0.8 and optical efficiency above 90% with an arbitrary half-beam angle greater than 45 deg. Typically, as compared with a conventional source-target energy mapping method, this design method can achieve better optical performance of lenses for general LED lighting. When a non-Lambertian-type light source is employed, for example, the chip on board LED, the use of the method can result in a compact LED lens without losing the optical performances of high irradiance uniformity and high optical efficiency as yielded by lenses for Lambertian-type LED light sources.

Optical Design of an LED Lighting Source for Fluorescence Microscopes

“…The central illuminance value of its halogen lamp projected on the specimen is approximately 10,578 lux. In order to use LEDs to replace the halogen lamp, we have designed a confocal total internal reflection lens array system (CTLAS), which is composed of a total internal reflection (TIR) lens array [32][33][34][35][36][37][38][39] and a confocal LED array system [40][41][42]. This system can efficiently collect light energy and project it onto the specimen.…”

Ray mapping with surface information for freeform illumination design

“…However, these methods are not easily generalizable to unique circumstances of geometry or desired energy distributions. One way to overcome this difficulty is to allow the problems to be solved in separate steps by first calculating the mapping relationship based on the source and target distributions and then using that relationship to construct a discrete surface from a normal field calculated by Snell's law [4][5][6][7][8][9][10][11][12][13].…”

“…Traditionally the energy distribution of the source used for the mapping relationship is sampled on a dummy surface in front of the lens [4][5][6][7][8][9][10][11][12][13]. Although some of the methods listed determine their sampling in angular space [5,8,10,12,13], one can always construct a dummy surface and select points such that the required angular sampling is achieved.…”

“…Although some of the methods listed determine their sampling in angular space [5,8,10,12,13], one can always construct a dummy surface and select points such that the required angular sampling is achieved. For example, one could use a hemispherical surface with points equally distributed along the azimuthal or polar angles.…”

“…Secondly, when surface information is withheld from the mapping calculation, the relative angular relationship between the surface profile and target plane can only be approximated at best while usually being neglected altogether. Traditionally the input and output distributions are calculated in isolation [4][5][6][7][8][9][10][11][12][13], leaving no ability to incorporate the relative geometries between the two surfaces. A mapping relationship calculated in this manner will be invariant of major changes in the geometry of the system, for example moving the target plane laterally away from the source.…”