Design and production of a free-form lens for long range LED illumination

In this study, a procedure for designing a free-form lens for long-range LED illumination is presented. The geometrical form of the proposed lens is obtained by minimizing optical path lengths of the rays emitted from a point-like light source. Optical ray tracing simulations of two different LEDs and the free-form lens are performed by using Zemax OpticStudio. In addition, the prototype of the free-form lens is manufactured by the plastic injection molding method using PMMA material. Nine of the lenses are used to build an LED projector in the form of a 3x3 lens matrix. The optical measurements of the projector are compared with the results predicted in the simulations. It is found that the beam divergence of the projector is less than 10 degrees when using suitable LEDs in visible and near infrared regions.