NICT Universal Media Research Center in Keihanna Research Labs (Kyoto, Japan) is conducting research on ultra-realistic communication systems using natural 3D images without special glasses. NICT has already developed a 70-inch glasses-free 3D display using multiple projectors to determine the basic principles of operation (Figure 1). To achieve high-presence communication using 3D images, we need a large 3D display that allows multiple viewers to simultaneously observe 3D images of large objects, such as life-size people. However, there have been problems related to the appearance of stripe noise, the reduction of 3D image resolution, and unnatural images due to the observer's movement, so it was difficult to enlarge the screen size by using conventional methods.

In our latest research, we numerically analyzed the factors causing the image quality reduction in order to enlarge image size. Methods of improving 3D image quality were studied using the numerical experimental results. The prototype 200-inch display system was designed and fabricated and the large, glasses-free 3D display technology was established (Figure 2).
One of the main impediments to image quality is the stripe noise between parallax images. We determined that the noise is influenced by the uniformities of brightness and color balance in the parallax images. To solve these problems, the brightness uniformities and color balance between projector units were compensated by the power-controlling LED light sources. We were able to reduce the stripe noise by introducing additional functions in each projector unit to adjust with high accuracy the brightness uniformities and color balance of each projected image.
In our method, special diffuser film and a condenser lens are used for the display screen (Figure 1). Light control accuracy of the display screen influences the resolution and natural motion parallax of 3D images. We estimated and selected suitable diffuser film and combined it with an optimally designed condenser lens. As a result, more than 50 parallax images can be displayed on the screen.

In future, we intend to increase the number of effective parallax images to about 200 and enlarge the viewing area so that more people can simultaneously enjoy 3D images (Figure 1). In addition, we will create and display various content that includes not only computer graphics but also actual scenes, such as humans or scenery. This display technology is expected to be used for industrial applications such as design, public viewings, digital signage, and showroom displays. The academic presentations of the related technologies will made at the “IS&T/SPIE Electronic Imaging 2011” conference to be held on January 23–27 in San Francisco. Note that the development of the projector units and display screen was under contract with the Ministry of Internal Affairs and Communications in the “Research and development on Glasses Free 3D Image Technologies” project with JVC KENWOOD Holdings, INC.