title: Compact lens with circular spot profile for square die LEDs in multi-LED projectors.
abstract: In the stage illumination industry, LED technology is promising both in terms of energy use and novel features, but it also has inherent issues. This paper presents a solution to the poor color homogeneity arising when multiple rectangular images formed from LED dies are combined into a circular spot profile. Using ray tracing, a nonrotationally symmetric collimating lens was optimized to round off such die images. The result is a high-output lens with an almost perfectly circular spot. In a simulated red green blue color mixing projector with seven LEDs, the lens reduced measurable color inhomogeneity by ≈24.1%, with a 5.3% luminous gain, compared to the best rotationally symmetric benchmark lens.
authors.affiliation: Department of Physics and Nanotechnology, Aalborg University, Skjernvej 4A, DK-9220 Aalborg, Denmark. tkj@nano.aau.dk
authors.forename: Thøger
authors.initials: T
authors.lastname: Kari
authors.forename: Jesper
authors.initials: J
authors.lastname: Gadegaard
authors.forename: Dennis Thykjaer
authors.initials: DT
authors.lastname: Jørgensen
authors.forename: Thomas
authors.initials: T
authors.lastname: Søndergaard
authors.forename: Thomas Garm
authors.initials: TG
authors.lastname: Pedersen
authors.forename: Kjeld
authors.initials: K
authors.lastname: Pedersen