Computational holography becomes highly complicated and demanding when it is employed to produce real three-dimensional (3D) images. Here we present a novel algorithm for generating a full parallax 3D computer generated hologram (CGH) with occlusion effect, which is an important property of 3D perception, but has often been neglected in most CGH related works. The ray casting technique is introduced to handle the occlusion issue. Horizontally and vertically distributed rays are projected from each hologram sample to the 3D objects to obtain the complex amplitude distribution. The proposed algorithm has no restriction on-or approximation to-the 3D objects, and it can produce reconstructed images with correct shading effect and no visible artifacts. An optical experiment is performed to validate our approach, using a phase-only spatial light modulator to optically reconstruct a 3D scene. The experimental result confirmed that the CGHs produced by our algorithm can successfully reconstruct 3D images with full parallax and occlusion effect.
We have fabricated a series of polymer stabilized chiral nematic test cells for use as flexoelectro-optic devices. The
devices fabricated were based on commercial chiral nematic mixtures which were polymer stabilized so as to enhance
the uniformity and stability of the uniform lying helix texture in the cells. During fabrication and test procedures a series
of unusual scattering states have been observed within the devices at different viewing angles. The observations made so
far indicate that the properties of the scattering state lies somewhere between the focal conic texture and the Grandjean
or planar texture and that the devices exhibit both a helical pitch selective reflection and scattering effect. What is even
more dramatic is that the wavelength selectivity of the scattering effect can be tuned by an applied field. In addition, we
show that it is possible to achieve good uniform lying helix textures from such devices. Moreover, we show that in
certain cases the spontaneous alignment of the helix in the plane of the device opens up the possibility of a new mode of
switching.
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