RESUMO
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.
RESUMO
Electrically tunable liquid crystal lens with 30 mm diameter is presented based on the refractive Fresnel concept. Relatively large optical power variation range (from - 0.74 to +0.71 Diopters) is demonstrated along with very low root mean square aberrations (≤0.15 µm). Optical characterizations, including with Snellen chart, show that good vision recovery may be obtained with fast response time (under 500 msec) and relatively low haze. The proposed design is very simple and may be fabricated by using single step lithography. Perspectives on its applications are discussed.
RESUMO
We report on the study of light polarization behavior in random anisotropy scattering media. It is shown that, in the case of low scattering events, the degree of polarization (DOP) demonstrates oscillatory behavior due to the coherent character of light scattering. A strong increase in the DOP is demonstrated by using electro-optic fine tuning of the refractive index modulation depth of the scattering media.
RESUMO
Electro-optic interferential quenching of light scattering is observed in microsphere and nematic liquid-crystal dispersions. The used drop-filled and nonaligned liquid-crystal matrix allows the formation of large orientational clusters responsible for this phenomenon, which is interpreted according to the single-scattering model.