  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.
