Projection-type See-through Holographic 3D Display Technology

NICT has newly developed a projection-type see-through holographic 3D display technology that allows us 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 (EMA) laboratory in 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 [see Fig. 3] but also fabricate a holographic optical element (HOE) with an arbitral reflection function (we call this kind of hologram a digitally designed holographic optical element (DDHOE)).

A 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 [see Fig. 2]. A digital holographic projector was developed by modifying NICT’s previous holographic 3D display system^[1] 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 [see Fig. 4]. Additionally, this film has high transparent characteristics at visible light wavelength [see Fig. 5]; 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 [see Fig. 2].

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.