A Fresnel lens with electrically-tunable diffraction efficiency while possessing high image quality is demonstrated using a phase-separated composite film (PSCOF). The light scattering-free PSCOF is obtained by anisotropic phase separation between liquid crystal and polymer. Such a lens can be operated below 12 volts and its switching time is reasonably fast (~10 ms). The maximum diffraction efficiency reaches ~35% for a linearly polarized light, which is close to the theoretical limit of 41%.

Electrically switchable Fresnel lens using a polymer-separated composite film.

A scattering-free, polarization controllable Fresnel zone plate lens is demonstrated using a photo-induced alignment of the dye-doped liquid crystal film. This photo-aligned liquid crystal zone plate provides orthogonal polarization states for odd and even zones. The different focus orders can be separated because of their different polarization states. The fabrication process is relatively simple and the operation voltage is less than 5 Vrms.

https://lcd.creol.ucf.edu/publications/2006/Opt%20Express%20Lin%20Fresnel.pdf

Polarization controllable Fresnel lens using dye-doped liquid crystals.

Fabrication of an all-optical switchable holographic liquid crystal (LC) Fresnel lens based on azo-dye-doped polymer-dispersed LCs is reported using a Michelson interferometer. It is found that, upon circularly polarized photoirradiation, the diffraction efficiency of the fabricated Fresnel lens was increased significantly in a reversible manner. We believe this is due to the anisotropy induced by reorientation of the LC molecules coupled with azo-dye molecule orientation due to trans–cis–trans photoisomerization, which modulates the refractive index of the LC-rich regions. We also studied the effect of azo dye on the polarization dependency of the fabricated lens.

All-optical switchable holographic Fresnel lens based on azo-dye-doped polymer-dispersed liquid crystals

This investigation elucidates a Fresnel lens using a simple approach that is based on a homogeneously aligned liquid crystal (LC) film with a preformed polymer relief pattern. Experimental results demonstrate that the LC Fresnel lens has polarization-dependent and electrically switchable focusing features. The LC lens has the further advantages of a weak operated field (~1.3 V/µm), and high diffraction efficiency (~34%).

Electrically switchable fresnel lens based on a liquid crystal film with a polymer relief pattern

This work reports a Fresnel zone plate in a circularly symmetric hybrid-aligned liquid crystal (LC) film with a photoconductive polymer layer. An ultraviolet-induced electrodelike pattern of polymer layer under a zone plate photomask results in alternating major and minor portions of external voltage dropping on LC layer in conductive and nonconductive regions, respectively. These effects cause the discrepancy in LC reorientation between adjacent zones, generating a Fresnel zone plate. The focusing of the zone plate is electrically controllable and polarization independent. Additionally, the zone plate has advantages of a zero focusing in the voltage-off state and a very small operating dc field range from 0to0.3V∕μm.

/pdf/electrically-controllable-and-polarization-independent-3w7pfe7fko.pdf

Electrically controllable and polarization-independent Fresnel zone plate in a circularly symmetric hybrid-aligned liquid crystal film with a photoconductive polymer layer

In this paper, a real-time incoherent 3D imaging and display system using the modified triangular interferometer is optically implemented The incoherent holographic system based-on this modified triangular interferometer employs the superposition of Fresnel zone patterns, in which the respective positions and intensities of the 3D object points are uniquely encoded and from this system the complex holograms without bias and conjugate images for the 3D object can be obtained In addition, the real and imaginary parts of a complex hologram are obtained by subtracting and adding two hologram patterns Then, illuminating them coherently and recombining the light passing through the transparencies by the use of the beam splitter allows the complex addition to be performed Then, the desired 3D image is reconstructed through Fresnel diffraction From some experiments with a 3D object of "dies", it is found that the incoherent 3D imaging and display system without the bias and conjugate image can be optically implemented in real-time by using a modified triangular interferometer© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering Downloading of the abstract is permitted for personal use only

Sang Eun Lee

Papers

Optical implementation of real-time incoherent 3D imaging and display system using modified triangular interferometer