Dynamic beam shaping for LED lighting.

We describe an electrically tunable liquid crystal microlens array with a 65 mm clear aperture that allows the dynamic symmetric broadening of white light without mechanical movements. The fundamental mechanism of broadening is demonstrated to involve a spatial twist of molecular orientation. Continuous variations of the light divergence angle are obtained in a very large dynamic range (from 8° to 50°). Particular attention is paid to maintain the desired intensity and color temperature distributions over the angle. The developed lens may be used in various broadband illumination applications based on light-emitting diode-pumped phosphor sources.