Display Characteristics of a Strain-free Stereoscopic TV

Aiming at natural stereoscopic

Sumio Yano,
Senior Research Engineer,
Three Dimensional Audio-Visual Systems

We have been researching a binocular stereoscopic TV system for future broadcasting services. This system uses two video images, one for each eye to bring a sense of depth to displays. The realization of a stereoscopic TV system will require development of new equipment in a wide range of fields, including program production, signal transmission, and image display. It will also be crucial to study the display characteristics in order to find those most suited to creating natural, strain-free stereoscopic viewing conditions.
The viewing of stereoscopic video images can lead to visual discomfort and may cause visual fatigue. Factors contributing to these problems are thought to include the geometrical gap between the two images, an incongruity in the size or electrical characteristics of the image displays, and crosstalk, i.e., data leakage between images. Experiments have revealed some of the display requirements for reproducing strain-free 3D images. These are shown in the table below.
Another factor causing visual discomfort and fatigue is the difference between the visual faculty used to see an actual object and the mechanism used for stereoscopic viewing. When viewing an actual object, the object is positioned at the point where the visual axes of the eyes intersect, as well as at the accommodation point (Figure a). In stereoscopic viewing, the stereoscopic image is reconstructed at the point where the visual axes intersect, but the accommodation adjustment faculty must work to focus at the display screen, where the actual images are located (Figure b).
However, this accommodation faculty has a depth of focus. Experiments have shown that convergence eye movement,as well as the accommodation faculty within this range, is basically the same as when viewing an actual object. They also indicate the possibility that visual fatigue can be reduced by reconstructing a stereoscopic image within the range of the depth of focus. The degrees of visual fatigue for stereoscopic image viewing are being evaluated under a variety of display characteristics.
Our research is on going and we believe it will one day be the basis for a future stereoscopic TV broadcasting system.

Table: Display characteristics for strain-free 3D images

Figure: Actual object viewing versus stereoscopic viewing

High-Speed Recording on a Phase Change Optical Disk

Challenges facing development of optical disk camera recorder for HDTV news gathering

Kiyohiko Ishikawa,
Recording Technology and Mechanical Engineering

We have been developing an optical disk that is to be used in a next-generation camera recorder for HDTV news gathering. The optical disk is easy to handle and it allows prompter editing at the coverage site in comparison with magnetic recording tape, makes it suitable as a recording medium for camera recorders used for news gathering, which requires high mobility and speed.
The optical disk also has a number of other merits; its noncontact recording and reproduction and good storage durability give it superior reliability, which makes it useful for archiving. Therefore, not only will its implementation enable a better news camera recorder, its storage capability will enable a more tractable use of the medium for material gathering, editing and storage (Figure 1).
The recording rate for the VCR presently used for HDTV news gathering is approximately 200 Mbps. To achieve an equivalent performance using an optical disk, it will be necessary for the recording rate to be approximately ten times that of the current recording rate of rewritable DVDs.
Recently a recording rate of 100 Mbps per channel was achieved, and the prospect exists for a 200 Mbps recording rate by means of parallel 2-channel recording on an optical disk. Figure 2 shows a block diagram of a high-transfer-rate optical disk recording experiment. We prepared an optical disk capable of high-speed recording and had the disk rotate on a prototype optical disk spin stand at a linear velocity of 25 m/s. We used a red laser for recording. As a result of decoding the coded signals with the recently developed PRML (Partial Response Maximum Likelihood) scheme, we obtained a sufficiently low bit error rate (10^-5 or less). This is adequate for video signal recording and reproduction when using error correction coding. We also started high-speed transfer rate recording and reproduction experiments, which utilized a blue laser.
Future work will include increasing the capacity of optical disks for HDTV recordings to longer than 20 minutes and fabricating a 200-Mbps recording rate optical disk system based on two-channel parallel recording technology.

Figure 1: Optical disk application method: from materials gathering to storage

Figure 2: Block diagram of high-transfer-rate optical disk recording experiment