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Hologram calculation
Published in Tomoyoshi Shimobaba, Tomoyoshi Ito, Computer Holography, 2019
Tomoyoshi Shimobaba, Tomoyoshi Ito
The holographic display can faithfully reconstruct the light of a three-dimensional object so that it can satisfy all human depth perception (binocular parallax, motion parallax, congestion, adjustment, etc.) and is accepted as an ideal three-dimensional display. This is difficult with other three-dimensional display technologies. In principle, if we develop the holographic display system of Figure 3.1, we can realize an ideal one. However, the following problems are hampering practical application. The range (viewing area) where the observer can see the three-dimensional image is narrow (viewing angle is several degrees and difficult for binocular vision).The size of the reconstructed three-dimensional image (field of view) is small (about several centimeters).Hologram calculation time is enormous.
Dynamic direct-writing optical holographic display based on quantum-dot-doped liquid crystal
Published in Liquid Crystals, 2021
Yunfeng Wang, Yan Li, Junhao Lin, Shuxin Liu, Yikai Su
Holographic display is a true 3D display technology, which provides 3D visual information by reconstructing light wavefront of objects [1,2]. Conventionally, computer-generated holograms (CGHs) are loaded on electrically addressed spatial light modulators (SLMs) to realise dynamic holography [3–6]. Due to the limited spatial resolution of the electrically addressed SLMs, it is difficult to achieve dynamic holographic display with a large viewing angle and high resolution. Optical holography based on photorefractive materials, such as photorefractive polymers [7–10], photorefractive liquid crystals (LCs) [10–15], etc., on the other hand, provides high resolution, low cost and high scalability, and hence is an attractive alternative to realise dynamic 3D display.
Full-color computational holographic near-eye display
Published in Journal of Information Display, 2019
Seyedmahdi Kazempourradi, Erdem Ulusoy, Hakan Urey
On the contrary to stereoscopic displays that provide perspective 2D images, a holographic display generates and presents the viewers directly a portion of the wave field that would emanate from the displayed 3D objects. As a result, viewers see the 3D objects with all natural depth cues. Since the viewers no longer focus on the display panel but rather on the gazed 3D object itself, the vergence-accommodation conflict (VAC) is eliminated. Majority of the proposed holographic display schemes have a table-top television-like configuration and aim to synthesize ghost-like 3D objects floating in mid-air around which several users can move and rotate [15–17]. Though this concept is definitely exciting, it is quite challenging as well. In particular, such schemes require large area SLMs with micron-level pixel pitches, corresponding to enormous SBP requirements that the current state of the SLM technology is far from meeting [4]. Not surprisingly, demonstrations are restricted to quite small objects and narrow viewing zones, with no sign of a significant improvement in the short run. A noteworthy solution is to use eye-tracking proposed by SeeReal Inc. to relieve the space-bandwidth-product (SBP) requirements [18]. SeaReal’s solution does not attempt to deliver the object waves within a large viewing area, but rather provides the object wave merely within two small windows conjugated to and steered with the eyes of the viewer. This way, the spatial bandwidth requirement of the holographic display is significantly reduced. However, the solution still requires a large panel SLM dedicated to a single user. Tracking the eyes of the viewer via cameras located on the distant display panel, which is about an arm’s length from the user, poses another complication. Further, the system allows user motion only within a limited region of space before the display needs to be rotated or translated.