See-Through Holographic 3D-Display

Projection-type see-through holographic 3D display technology. (Source: NICT)

Projection-type see-through holographic 3D display technology. (Source: NICT)

Researchers at the National Institute of Infor­mation and Communi­cations Techno­logy NICT, Japan, has newly developed a projection-type see-through holo­graphic 3D display techno­logy that allows to design freely both the display size and the visual angle inde­pendently of see-through holo­graphic 3D image recon­struction. For the purpose of creating a new optical techno­logy, the Electro­magnetic Appli­cation Labo­ratory at NICT started the holo­graphic printing techno­logy (“HOPTECH”) project in 2014. As a part of this project, a hologram printer for recording a digitally designed wavefront was developed. This printer can not only print 3D data for 3D visua­lization but also fabricate a holo­graphic optical element (HOE) with an arbitral reflection function. This kind of hologram are called a digitally designed holo­graphic optical element (DDHOE).

The new approach was achieved using two key technologies: digital holo­graphic pro­jection to enlarge the display size and fabri­cation of an optical screen of DDHOE that reflects the light of a projected holographic 3D image to a target obser­vation area to increase the visual angle. A digital holo­graphic projector was developed by modifying NICT’s previous holo­graphic 3D display system with a pro­jection lens. The appro­priate reflection function, namely, the function to con­centrate the light of a projected holo­graphic 3D image to the target observation area, of DDHOE was once calculated as wavefront infor­mation (amplitude and phase distr­ibution of the light) consi­dering the pro­jection para­meters.

The wavefront of that reflec­tion function was then implemented into a holo­graphic recording film by using a hologram printer. In comparison with conven­tional approaches that use a concave mirror or a convex lens to increase the visual angle of a holo­graphic 3D image, the new approach can achieve a higher degree of freedom of display size and visual angle. These para­meters are important for practical display use, by using only a thin film of DDHOE. Additionally, this film has high transparent charac­teristics at visible light wavelength. This work will open up the real holo­graphic 3D display of some appli­cations such as in-car head-up displays, smart glasses, head-mounted displays and digital signage.

NICT will optimize the full-color display system by upgrading the hologram printer. Multiple holo­graphic pro­jections from different incident direc­tions to the DDHOE will also be focused on to extend the obser­vation area. (Source: NICT)

Reference: K. Wakunami et al.: Projection-type see-through holographic three-dimensional display, Nat. Comms. 7, 12954 (2016); DOI: 10.1038/ncomms12954

Link: Applied Electromagnetic Research Institute, National Institute of Information and Communications Technology NICT, Tokyo, Japan

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