The early developers of optical media countered objections to the medium's read-only nature by responding that it would be so inexpensive that,. when filed, one would just throw it away like a piece of paper. After all, paper is basically a read-only, throw-away medium. After we write on a page, we discard it rather than erasing and reusing it.
Write-once media that allows users to control what they record on the disc have been relatively expensive, both in terms of the hardware and the discs. CDROM, on the other hand, has served as a publishing medium. The high costs of gathering, organizing, and preparing the data for mastering on the CD-ROM disc account for a large portion of the relatively high prices of these products. Thus, the contents as well as the searchand-retrieval software give die disc its value.
When updates are released, the user generally discards the superseded disc. In cases of licensing agreements, the user returns the superseded disc to the producer, who throws it away. With the information content outdated, the value of the disc decreases dramatically. CD-ROM then becomes a throw-away medium.
ICI Electronics' Digital Paper
ICI Electronics is developing a flexible optical storage medium that it calls Digital Paper. It uses a a polyester substrate (Melinex) which somewhat resembles Kodak's Mylar, the substrate for videotape. The polyester substrate measures between 25 and 75 microns thick. A metallic reflective layer covers the substrate, which then receives a coating of a polymer dye that is sensitive to infrared light. A protective overcoat completes die product.
The process of reading and writing to digital paper resembles that for optical disks. A 780- or 830-narometer solid state laser writes the bits at a spot size of 1.0 micron and a track pitch of 1.4 micron. If an application requires preformatting of data and tracks, the dye/ polymer layer gets embossed.
Advantages of Digital Paper
Digital paper has several advantages, including its variety of physical forms, high recording capacity, compactness, durability, indelible recording, long life, machine readability and low production costs.
The manufacturing process produces digital paper in a continuous web in roll form. This uses less material than rigid media, costs less to produce because of higher production rates and lower handling costs compared with batch manufacturing, and minimizes waste. The manufacturer can then cut sheets of digital paper into a variety of physical formats that include disk, tape, cylinder, card, strip, and tag. The tape could come in reel-to-reel format or get wound into cassettes. This results in a product that is easily transportable without risk of damage.
As optical recording uses higher powered lasers and shorter wavelengths, drive manufacturers hope to improve access times and data storage rates even further. The shorter wavelengths provide greater density and higher speed while the higher powered lasers translate into higher data rates. Because digital paper is another optical medium, it benefits from die same characteristics of durability and indelible recording that characterize the other optical media.
The Optical Tape Format
ICI is currently concentrating its efforts on producing digital paper in optical tape and disk foffnats. Optical tape has many features that translate into a wide array of benefits. High-volume storage density requires less space for swrage and allows for unattended operation because it needs fewer mounts/dismounts. High transfer rates provide more efficient operation and compatibility with existing equipment Fast access time means higher usage resulting from low waiting cost. The variety of forms the medium can take permit the manufacturer to develop alternative packaging that can address different markets.
Digital paper can also support a variety of scanning techniques that include transverse, helical, block parallel, transverse helical, and serpentine. …