Asymmetric reflector aberrations worsen illuminance uniformity and distort illuminance pattern. Using trough reflector
design as an example, the aberrations are found significant in the design where the β angle coverage is in low number
zones. In that situation an alternative approach could be used to achieve the same if not better illuminance uniformity.
Besides target position, optical planning is also found a factor influencing the actual illuminance distribution although
its impact is limited. An intensity-based reflector design method with both normalizing factor and reflector reflectance
incorporated as variables is applied to compare all the designs. A new calculation method using α angle to acquire (x, y)
coordinates is used to generate the reflector profiles.
How to design and calculate asymmetric reflectors using an equation method is presented here. Isotropic linear source used with trough reflector and side emitting cylindrical source used with revolution reflector are given as examples. All results are presented for side-illuminating configurations that may require converging optical plans.
A reflector design method that follows the standard reflector design principle but uses equations to match incident angles and reflected angles is presented. Using this method, errors introduced by traditional graphic approach are minimized if not eliminated in many cases. The resolution of the reflector profile is no longer limited. A calculation method that is capable of generating reflector profiles in (x,y) form is also presented. The methods and all results are
presented for symmetric reflector configurations.
This study investigates illuminators composed of light emitting diode (LED) array sources and side-emitting light guides to provide efficient general illumination. Specifically, new geometries are explored to increase the efficiency of current systems while maintaining desired light distribution. LED technology is already successfully applied in many illumination applications, such as traffic signals and liquid crystal display (LCD) backlighting. It provides energy-efficient, small-package, long-life, and color-adjustable illumination. However, the use of LEDs in general illumination is still in its early stages. Current side-emitting systems typically use a light guide with light sources at one end, an end-cap surface at the other end, and light releasing sidewalls. This geometry introduces efficiency loss that can be as high as 40%. The illuminators analyzed in this study use LED array sources along the longitude of a light guide to increase the system efficiency. These new geometries also provide the freedom of elongating the system without sacrificing system efficiency. In addition, alternative geometries can be used to create white light with monochromatic LED sources. As concluded by this study, the side-emitting illuminators using LED sources gives the possibility of an efficient, distribution-controllable linear lighting system.
KEYWORDS: Optical components, Light sources, Light emitting diodes, Waveguides, Computer simulations, Monte Carlo methods, Ray tracing, Light sources and illumination, Optical simulations, RGB color model
An experimental study was conducted to investigate the possible use of light guides as mixing elements for mixed color white LED systems. In this study two types of light guides, one with a square cross section and the other with a circular cross section, were systematically analyzed for color mixing. Past literature suggested that square shaped light guides are better color mixers than circular light guides. This study was comprised of two parts: a computer simulation using a commercial ray tracing software package; and an experimental study verifying the results obtained from the simulation. Beam uniformity, in terms of illuminance and color, did not improve significantly with the light guides. System efficiency dropped as a function of length. The measured results matched the simulation results well. Circular and square light guide geometries showed similar performance, contrary to what was suggested in previous literature. Significant improvement of the illuminance and color uniformity was noted when the output ends of the light guides were diffused. This introduced only a small additional loss (6%) in system efficiency.