A research team led by Professor Park Yong-geun of the Korea Advanced Institute of Science and Technology (KAIST) has developed a technology that can reproduce three dimensional (3D) holographic displays without glasses.
This technology has improving 3D display technology one step further by taking an ultra-thin structure, being compatible with conventional display production process, and securing a large-area wide viewing angle.
A holographic display that can reproduce realistic 3D images without special glasses has long been regarded as a dream technology. However, the 3D image created by the conventional technology is very small in size and the viewing angle is also limited, so it is practically difficult to be implemented.
To create a 3D hologram, both the intensity of the light and the direction in which the light travels must be precisely modulated. Precise modulation of the direction of light propagation is achieved by a spatial light wave front controller.
In order to precisely control the direction in which the light travels from a wide angle, the spatial light wavefront controller must be made of many pixels. However, the number of pixels of the conventional wavefront controller is insufficient to create realistic 3D images. That is, the light can be modulated only within a very limited angle.
Under these conditions, the 3D image that can be made with the current technology is limited to about 1 centimeter (cm) in size and a viewable angle of about 3 degrees, making it practically impossible to be commercialized.
Instead of constructing a complex optical system, the team developed a 3D image with greatly improved performance compared by adding LCD panels and unperiodically designed thin films. Thin films consist of numerous apertures (pinholes) arranged in an unperiodical fashion, and the pinholes spread the light at a wide angle, forming a 3D image that can be seen from a wide angle.
The researchers attached the thin film designed according to the theory to the LCD panel of the conventional display and succeeded in developing a 3D holographic image with a viewing angle of about 30 degrees on a screen of about 3 cm × 3 cm. This is about 400 times more than the space bandwidth that can be represented by a full HD holographic display. They also implemented dynamic holograms with three colors (red, green, blue) operating at 60 Hz.
Dr. Park Jong-chan, the first author of the paper, said, "In order to commercialize a holographic display, it is necessary to maintain a small form factor as well as a wide viewing angle and a large image size. In this study, we created a large-area wide viewing angle holographic display in a flat display." He added, "We expect that this will be a foundation technology for implementing holographic displays in portable devices, such as smartphones and tablets."
The result of this research led by Park (formerly a researcher at the KAIST Physics Department, currently a researcher at the University of Illinois at Urbana-Champaign) was published in the online edition of Nature Communications on March 21.