We are engaged in international standardization activities for 3D displays. We consider that for a sound development of
3D displays' market, the standards should be based on not only mechanism of 3D displays, but also human factors for
stereopsis. However, we think that there is no common understanding on what the 3D display should be and that the
situation makes developing the standards difficult. In this paper, to understand the mechanism and human factors, we
focus on a double image, which occurs in some conditions on an autostereoscopic display. Although the double image is
generally considered as an unwanted effect, we consider that whether the double image is unwanted or not depends on
the situation and that there are some allowable double images. We tried to classify the double images into the unwanted
and the allowable in terms of the display mechanism and visual ergonomics for stereopsis. The issues associated with the
double image are closely related to performance characteristics for the autostereoscopic display. We also propose
performance characteristics, measurement and analysis methods to represent interocular crosstalk and motion parallax.
A display system with lens arrays at the front of a high-resolution LCD has been known as a method to realize an
autostereoscopic three-dimensional (3D) display. In these displays, a light ray overlap between neighboring parallax
images affects the image quality. In this study, the overlap effects were investigated for the one-dimensional (horizontal
parallax only) integral imaging (1D-II) method. We fabricated samples of 1D-II displays with different levels of light ray
overlaps and evaluated the 3D image by subjective assessment. It is found that the 1D-II display utilizing the proper
parallax overlaps can eliminate banding artifact and have good 3D image quality within the wide range of a viewing area.
We analyzed resolution characteristics of a lenticular-sheet 3D display system. The measured samples are onedimensional
integral imaging (1D-II) display systems of 9-18 parallaxes with slanted/vertical lenticular sheet. The
measured contrast ratio curves of various sinusoidal patterns as functions of depth are in good agreement with the
theoretical resolution limit for both vertical and slanted lenticular-sheet types. The 1D-II display systems with parallel
beam configuration show spatial distribution of resolution in the horizontal direction corresponding to parallax crosstalk.
If the parallax crosstalk is not designed properly, this distribution is observed as moiré pattern and degrades 3D image
quality. When the gap between the lenticular sheet and the elemental image plane changes in the depth direction, the
apparent resolution curve shifts in the same direction; if the gap is large, objects displayed at the near side have higher
resolution, and if the gap is small, objects displayed at the far side have higher resolution. This phenomenon is also
explained by an effect of the parallax crosstalk caused by defocusing.
We propose a new capturing system to realize capture of elemental images for an autostereoscopic display based on a
one-dimensional integral imaging (1D-II) method. In order to realize a capturing system for the 1D-II display, capturing
elemental images with fine pith and containing much horizontal parallax information with wide angle are important. The
optical system composed of a cylindrical lens, a focusing lens and an imaging device can capture elemental images
having these two features with scanning over an object. Furthermore, the system size can be small by adapting a
compact scanning optical system of a copy machine. We captured 200 elemental images at a fine scan pitch of 0.5 mm.
There were 92 horizontal pixels on each elemental image. The number of horizontal pixels correspond the number of
parallaxes. The angle range of the captured parallaxes was 42 degrees. Using the autostereoscopic display based on the
1D-II method, the synthesized image can be observed to be a correct three-dimensional (3-D) image.
We have developed prototypes of flatbed-type autostereoscopic display systems using one-dimensional integral imaging
method. The integral imaging system reproduces light beams similar of those produced by a real object. Our display
architecture is suitable for flatbed configurations because it has a large margin for viewing distance and angle and has
continuous motion parallax. We have applied our technology to 15.4-inch displays. We realized horizontal resolution of
480 with 12 parallaxes due to adoption of mosaic pixel arrangement of the display panel. It allows viewers to see high
quality autostereoscopic images. Viewing the display from angle allows the viewer to experience 3-D images that stand
out several centimeters from the surface of the display. Mixed reality of virtual 3-D objects and real objects are also
realized on a flatbed display. In seeking reproduction of natural 3-D images on the flatbed display, we developed
proprietary software. The fast playback of the CG movie contents and real-time interaction are realized with the aid of a
graphics card. Realization of the safety 3-D images to the human beings is very important. Therefore, we have measured
the effects on the visual function and evaluated the biological effects. For example, the accommodation and convergence
were measured at the same time. The various biological effects are also measured before and after the task of watching
3-D images. We have found that our displays show better results than those to a conventional stereoscopic display. The
new technology opens up new areas of application for 3-D displays, including arcade games, e-learning, simulations of
buildings and landscapes, and even 3-D menus in restaurants.
We have developed a flatbed-type autostereoscopic display system showing continuous motion parallax as an extended form of a one-dimensional integral imaging (1D-II) display system. The 1D-II display architecture is suitable for both flatbed and upright configurations. We have also designed an image format specification for encoding 1D-II data. In this parallax image array format, two (or more) viewpoint images whose viewpoint numbers are separated by a constant number are paired, and all of the paired images are combined to obtain an image the same size as the elemental image array. By using the format, 3-D image quality is hardly degraded by lossy codec. The conversion from this format to the elemental image array is simple and does not depend on changes in the viewing distance and associated changes in camera number. Decoding and converting speeds are sufficiently high due to utilization of middleware based on
We have developed some prototypes of a one-dimensional integral imaging (1-D II) autostereoscopic display. Generally, II is one of the most promising methods for realizing an autostereoscopic display. However, a lens or barrier pitch is wide and obtrusive because this method requires many parallaxes. In this case, slanting lens or barrier is undesirable because the pattern is asymmetrical. From the result of examination about the display resolution of the autostereoscopic display, we adopted an LCD with mosaic color filter arrangement and a vertical lenticular sheet. We changed the color filter to the mosaic arrangement for two types of LCD. One was an LCD of 20.8-inch diagonal size with QUXGA resolution (3200 x 2400 pixels) and another was an LCD of 15.4-inch diagonal size with WUXGA resolution (1920 x 1200 pixels). The typical specifications of the prototypes of the autostereoscopic display were 32 parallaxes with 300 horizontal resolution for the 20.8-inch size and 18 parallaxes with the same resolution for the 15.4-inch size. We confirmed these prototypes showed good appearance and stereoscopic display properties due to the symmetrical lens pattern.
We propose a novel algorithm to maximize the viewing zone of integral 3-D imaging (II) display. In our algorithm, the elemental image array consists of two kinds of elemental images whose numbers of sub-pixels are <i>N</i> and (<i>N</i>+1). The pitch of exit pupils was set to be <i>N</i> times the width of the sub-pixel and an average width of elemental images was designed to exceed the pitch of the exit pupils to a small extent by distributing the elemental images consisting of (<i>N</i>+1) sub-pixels. Under this condition, all light rays generated from elemental images can be introduced to the viewing zone width (viewing width) on the viewing line at the distance <i>L</i> without converging points of light rays at around <i>L</i>. This algorithm was applied to one-dimensional II system with 32 parallax light rays using a 20.8”-QUXGA-LCD (192 ppi) equipped with a lenticular sheet. Then, the viewing width at 1.5 m was expanded to 500 mm, a value almost five times larger than the width of a conventional display system. Even if hardware configurations are fixed, our algorithm enables a viewing zone to be the maximum at a certain <i>L</i>.