RESUMO
A LCD backlighting device that uses a diffractive light extractor has been developed for applications in which pointlike light sources are employed. The novel system eliminates the images of light sources, which appear as bright lines emanating from each source in the conventional diffractive approach. In addition, the system illuminates the LCD uniformly: Modulation of the diffractive structure as a function of position is used to control the output field of this extended planar light source.
RESUMO
Tailoring of the transverse intensity profiles of propagation-invariant optical fields is considered. The design of diffractive elements capable of realizing such fields by Fourier synthesis is discussed. High-efficiency realization of finite-aperture approximations of the constructed fields is demonstrated in a system consisting of two multilevel diffractive elements. The first element is a diffractive toroidal lens, which focuses the incident field into a ring pattern. The second diffractive element, located at the focal plane of the first element, introduces the phase modulation necessary to realize the desired transverse intensity profile behind a separate collimating lens. The influence of the fabrication errors of the diffractive elements on the fidelity of the propagation-invariant spot array is simulated, and system-integration aspects based on substrate-mode planar-integrated optics are considered.