In holographic display, SBP can be represented by the equation, W × θ = λ × N, where W is the image size, θ is the viewing angle, λ is the wavelength, and N is the number of pixels. To generate 4-K (3840 × 2160) ultra-high-definition (UHD) pixel holograms in real-time, a holographic video processor is implemented on a single-chip field programmable gate array (FPGA). All the optical components are designed and fabricated as a slim structure. It is the highest SBP ever achieved for a real-time holographic video system using an SLM. The effective SBP is increased by 30 times compared to the original value by using the S-BLU. To increase effective SBP (Supplementary Note 1), a steering-backlight unit (S-BLU), which consists of a coherent-BLU (C-BLU) and a beam deflector (BD) is introduced. It resolves all the above issues of low SBP, bulky optical system, and enormous computational cost. In this research, a real-time interactive slim-panel holographic video display is demonstrated for the first time. Several studies have been carried out to optimise algorithms and to increase computation speed, but they still require clustered processors or high-performance parallel processing systems to calculate high-quality hologram at video frame rate 11, 12, 13, 14, 15, 16. Last, the calculation of hologram in real-time typically requires huge computational cost, and the amount of computation increases as the SBP increases. It is difficult to realise a holographic video display as slim as flat-panel displays commercialised nowadays. Second, to generate a large coherent backlight, complicated optical components and a considerable space is required for the manipulation of light. It means that only a small size or a narrow viewing angle dynamic hologram can be realised. The SBP of the currently available SLM is generally a few hundred times less than the SBP of the static holographic media. However, SBP is limited by the pixel size and the number of pixels when an SLM is used as a dynamic holographic medium. The static holographic media can produce large holographic images with a large viewing angle, because the information of hologram is recorded in the sub-wavelength density and it can be recorded on the large size film. First of all, there is the limitation of the space-bandwidth product (SBP), which determines both the size of holographic image and the viewing angle. To build a mobile holographic video display, the following barriers need to be overcome. It is expected to require quite an amount of time to reach the mobile holographic video for practical applications. However, it has been demonstrated that vertical parallax only holograms using a bulky optical system. The recent study on a holographic display was reported, including a full-colour 3D computer-generated hologram (CGH) calculated in real-time, and a focus-adjustable reconstructed image 10. Many researches have demonstrated holographic video systems so far, including anisotropic leaky mode 8 and eye tracking 9. By using a spatial light modulator (SLM), which directly modulates the wavefront of light, it is possible to update holograms at video rate. However, those holographic media are non-updatable or have a limited updating frequency 7, causing a fundamental limitation for generating dynamic holograms. Recently, nanophotonics 5 and metasurfaces 6 are also used to reconstruct static holograms. We suggest that the slim-panel holographic display can provide realistic three-dimensional video in office and household environments.īecause of its advantage in 3D image reproduction, the technology for static holograms is quickly developed to a high standard by using hologram recording materials such as silver halide and photopolymer 4. The holographic video processor computes high quality holograms in real-time on a single-chip. The steering-backlight unit enables to expand the viewing angle by 30 times and its diffractive waveguide architecture makes a slim display form-factor. Here we present an interactive slim-panel holographic video display using a steering-backlight unit and a holographic video processor to solve the above issues. However, commercially available holographic video displays have not been introduced yet for several reasons: narrow viewing angle, bulky optics and heavy computing power. at MIT Media Lab developed the first holographic video systems in 1990. Holographic video has been extensively researched for commercialization, since Benton et al. Since its discovery almost 70 years ago, the hologram has been considered to reproduce the most realistic three dimensional images without visual side effects.
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