Design and analysis of reflector for uniform light-emitting diode illuminance

A light-emitting diode (LED) projection system is proposed, composed of an LED chip and a variable-focus-parabolic (VFP) reflector, in which the focal length varies as a function of the vertical displacement of the incidence point relative to the horizontal centerline of the LED chip. The light-ray paths within the projection system are analyzed using an exact analytical model and a skew-ray tracing approach. The profile of the proposed VFP reflector and the position of the LED chip are then optimized in such a way as to enhance the uniformity of the illuminance distribution on the target region of the image plane. The validity of the optimized design is demonstrated by means of ZEMAX simulations. It is shown that the optimized VFP projector system yields a significant improvement in illuminance uniformity compared to conventional spherical and parabolic projectors and therefore minimizes the glare effect.