Site: Pioneer Corporation
Corporate R&D Laboratory
6-1-1 Fujimi, Tsurugashima
Saitama 350-02, Japan
Date Visited: 30 March 1998
In the field of optical disk data storage, Pioneer is a manufacturer of CD-ROM, DVD-ROM and DVD-R media. Presently it is engaged to establish the DVD-RAM version 1.0 and 2.0 (2.6 GB and 4.7 GB) specifications in the DVD Forum working group 5, but its main focus is developing a 4.7 GB DVD-RW disc and drive as well as next generation 15 GB DVD-RW disc and drive.
Pioneer laboratories are engaged in a number of research activities at the leading edge of modern optical technology. For example, they are developing blue lasers for various applications using both the technique of second harmonic generation (SHG) and direct fabrication of blue semiconductor lasers based on III-V materials (GaN-based system). They are also active in developing new display technologies based on a class of organic electroluminescent materials. At the time of this visit their R&D laboratories employed a total of 165 researchers.
In the area of optical data storage, Pioneer's research seems to be focused on DVD-ROM and rewritable DVD systems. Pioneer has an in-house mastering facility for producing high-density disks for research and development purposes. The hosts mentioned their plans to bring out the 15 GB DVD-ROM by the year 2001. This system, which is intended for high definition TV (HDTV), will use low-power blue lasers, and will employ actively controlled liquid crystal (LC) elements for aberration correction and for tilt servoing. The use of a 410 nm blue laser and a 0.6 NA objective lens will allow a capacity of only 9 GB on a 12 cm platter. To get to 15 GB, Pioneer researchers plan to use a number of advanced techniques, including 2D equalizer, cross-talk canceller, adaptive tangential equalizer, and Viterbi decoder.
Pioneer's prototype 15 GB DVD-ROM system uses a three-beam cross-talk canceller, which also provides the feedback signal to the radial tilt correcting servo based on an LC element. Although in principle this liquid crystal element can also do automatic correction for the tangential tilt, in practice the speed of switching the LC is not sufficient for high-speed applications. The tangential tilt correction is therefore done by electronic equalization. The details of this equalizer (which the hosts referred to as "super equalizer") were not discussed because Pioneer is applying for a patent on this technology.
To produce the 15 GB master for second-generation DVD-ROM, Pioneer researchers used a photo-bleachable dye layer on top of the photoresist. Only the central region of the focused spot is strong enough to bleach the dye layer and, therefore, expose the photoresist layer below. In this way, the researchers could achieve super-resolution and create well-defined pits. They estimated that the use of the photo-bleachable layer had improved their cutting resolution by about 20%. Their mastering machine used a 0.9 NA lens and a 351 nm laser, and created DVD masters with a track pitch of 0.37 microns and minimum mark length (3T) of 0.25 microns.
In the area of rewritable DVD the hosts mentioned Pioneer's DVD-R/W format based on rewritable phase-change media, with a limited number of write/erase cycles (around 1,000). This product is intended for the consumer market (as opposed to the computer market), for which the limited cyclability is acceptable. Compatibility with DVD-ROM was highly emphasized. Pioneer researchers' material of choice for DVD-R/W is InAgSb, which is the same material used in CD-R/W. They said that they have confirmed a jitter value of less than 7% in this material at 4.7 GB capacity and over 100 times cyclability, which is better than what DVD-RAM can claim at the moment. Pioneer researchers hoped to develop the 4.7 GB DVD-R/W before the end of 1998. They maintained that of all the issues facing rewritable DVD, probably the copy protection issue is the most significant stumbling block.
Pioneer researchers gave the WTEC team a tour of their laboratories, where they showed the various technologies developed for the second generation DVD-ROM and DVD-RW. In particular, team members saw the improvement of the read signal due to the LC-based tilt servo, and the improvement of the eye-pattern by the so-called "super equalizer."
As for life after 2001, Pioneer researchers showed the WTEC team preliminary examples of techniques that will be used in the 50 GB DVD-ROM. Unless some new technologies are developed in the next few years, it seems likely that electron beam lithography will be needed to create 50 GB master disks.
Pioneer researchers have investigated both magneto-optical and phase-change media in the past but seem determined to move towards phase-change technology in their consumer-oriented strategy. They maintained that the "advanced storage magneto-optical disk" (ASMO, a.k.a., MO7) seems to have the support of the disk manufacturers but not the support of drive manufacturers in Japan. They also seemed to think that there are certain problems with the development of the ASMO technology, especially as related to the thin disk.