A Rewritable, Higher-Capacity Compact Disk

Optical disks hold much more data than conventional magnetic hard or floppy disks, the alternative data-storage technology. The optical devices employ the same technology used with music CDs: a laser stores the data by pitting the disk surface in a pattern that can be read by another laser. When it was introduced, a conventional plastic CD-ROM could hold 650 megabytes of data, whereas typical hard disks then held fewer than 50 megabytes. Optical disks, however, could be written only once, and the drive mechanism was much slower than magnetic hard disk drives.

New technology is addressing both deficiencies. Optical-disk-drive speeds have increased substantially, and several techniques for enabling the device to write new data are now commercially available. This project with ETOM Technologies, a small start-up company, developed technology that greatly increases the amount of data that can be stored on optical disks.

Large Jump in Storage Capacity

The ETOM technology uses a glass, rather than plastic, disk onto which is laid a light-sensitive substrate that can be written and read by the lasers in conventional CD-ROM drives. The core technology is called electron-trapping optical memory (ETOM). Data are "written" to the substrate by a low-power laser tuned to a specific frequency. The laser light raises individual electrons in the substrate to an elevated energy level, where they are trapped indefinitely. The data are "read" by a second laser, which releases the trapped electrons to return to their lower energy state, emitting a light signal in the process.

In addition to being a write-and-read device, the ETOM disk is able to store data at multiple energy levels, giving it the ability to use "multiple-ary" digits, as opposed to the binary digits (having two energy levels) used in conventional magnetic data storage. This capability greatly increases the amount of data that can be placed on the disk. For example, a byte (group of eight digits) using binary digits can store 256 different numbers. A byte using a multiple-ary digit with three energy levels, however, can store 6,561 numbers. Thus, the use of just three different energy levels instead of two increases the disk's storage capacity more than 25 times.

Unforeseen Obstacles Block Commercialization

The company planned to manufacture and sell ETOM-based digital video recording products if the technology could be successfully developed. The technology was developed. But barriers arose that made it impossible to offer a cost-effective video CD-ROM. The company needed a green laser, but a commercial supply of them did not materialize as expected. Nor did the market materialize for a video-on-demand device, which would have used the video CD-ROM to temporarily store movies and other videos downloaded by viewer request from a cable-TV company.

After attempting to develop additional technologies to enable it to survive, ETOM ran into severe financial problems in late 1997. Private investors in ETOM decided it could not continue to operate without the business from a partnership to commercialize one of these technologies - a deal that ultimately fell through - so they decided to close ETOM. It ceased operations in January 1998 and filed for bankruptcy two months later.

ATP Critical to Developing New Technology

ETOM reports that if it had not received the $1.4 million ATP award, it could not have performed the research and probably would not have survived as a company long enough to conduct the research. It encountered difficulties in bringing to market an optical disk device incorporating its new technology. Even though the company is no longer in business, the new approaches developed in this ATP project may eventually be picked up and used by some other company.

Go to other sections of Chapter 7: INFORMATION, COMPUTERS, AND COMMUNICATIONS
	Computer Recognition of Natural Handwriting
	Chinese Character-Recognition Methods for Computer Data Entry
	Three-Dimensional Anatomy of Human Body, With Animation, for Medical Training
	Packing More Data Into Optical Data-Storage Disks
	Mathematical Technology to Restore or Enhance Movies
	A User-Friendly Programmer's Tool for Writing Parallel-Processing Software