Design of compact and smooth free-form optical system with uniform illuminance for LED source

Abstract

A feedback modification method based on variable separation mapping is proposed in the design of free-form optical system with uniform illuminance for LED source. In this method, the non-negligible size of LED source is taken into account, and a smooth optical system is established with single freeform surface regenerated by adding feedback to the lens design for a point light source. More rounds of feedback can improve the lens performance. As an example, a smooth free-form lens with rectangular illuminance distribution is designed, and the illuminance uniformity is improved from 18.75% to 81.08% after eight times feedback.

Overall Illuminance Uniformity of IRED Lighting in Nighttime CCTV

“…Reflective surface efficiency is not very high, since it is impossible to cover the whole source emergence spatial angle without any occlusion. Because of this, a lens based on refraction and/or total internal reflection of the freeform surface lens has an potential advantage [5][6][7].…”

Design Method for a Total Internal Reflection LED Lens with Double Freeform Surfaces for Narrow and Uniform Illumination

“…The LED lens can be designed using a differential equation method [8][9][10][11], a parameter optimization method [12][13][14][15], or a simultaneous multiple surface (SMS) method [16][17][18], and it often includes one or more freeform surfaces, for the sake of low price and high efficiency. The differential equation method is an LED lens design method in which differential equations relating to the propagation of rays through an LED lens are solved assuming that one surface of the lens is already known; then the other surface is freeform.…”

“…In this method, first the location of a ray of light emitted from the LED to impinge on a target plane is determined, depending on an illumination model selected to form a desired illuminance distribution on the target plane. Then the surface slope of a corresponding incident point on the freeform surface is determined so that the ray incident upon the surface will pass through a designated point on the target plane [8][9][10][11]. Though the freeform surface is easily determined, as long as the related simultaneous differential equations can be derived completely, the luminous ISSN: 1226-4776(Print) / ISSN: 2093-6885(Online) DOI: http://dx.doi.org/10.3807/JOSK.2016.…”

Parametric optimization method for the design of high-efficiency free-form illumination system with a LED source

“…Among the mapping methods, the variable separation mapping method [5] provides an efficient way of constructing illumination systems with a point light source; discontinuities are introduced onto the free-form surfaces to reduce the accumulated surface normal deviations. However, in the design of micro illumination systems where the size of the LED sources cannot be neglected, mapping methods with point light source approximation are no longer effective [6] . In the design of illumination systems with surfaceemitting light sources, two types of approximate methods may be used.…”

“…In the design of illumination systems with surfaceemitting light sources, two types of approximate methods may be used. One is the simultaneous multiple surface method (SMS) [7] , and the other is the feed-back modification method [6] . The SMS method is specialized for designing free-form surfaces with surface-emitting sources.…”