CD-ROM and Optical Storage -- A Short History

by

Robert Apple

Cmptr Arch & Operating Systems MCT*611*XP40 < instructor name removed > May 25, 2007

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CD-ROM and Optical Storage

Since the advent of the transistor and integrated circuit in the mid 20th century, the need for information storage and retrieval has grown. This trend has both fueled the innovative process and helped to increase the information explosion. One particular invention, the CD-

ROM, and optical storage as a whole, has had a profound effect on data storage and retrieval, both in the general computer industry as well as other communication arenas, particularly the music industry. It is the intent of this paper to briefly describe the CD-ROM architecture, its development history, some of the market trends driving its development, and its massive impact on society in the electronic age.

The modern read only compact disk (CD-ROM) is a circular disk approximately 12 cm in diameter and 1.2 mm in width. It is composed of injection-molded polycarbonate plastic which has a long spiral of tiny indentations impressed on it in a circular fashion starting from the inside and working its way outward. This string of tiny indentations strung together forms what is called a track. Pressed on top of this polycarbonate plastic is a thin layer of reflective aluminum which covers the indentations. On top of that is a thin acrylic layer which protects the underlying aluminum, and possibly a label on the top of that acrylic layer (Brain, n.d.).

The string of indentations that make up the spiral track of the polycarbonate plastic are extremely close to each other in the spiral, approximately 0.5 microns apart, and the spiral itself is approximately 1.6 microns away from the nearest track next to it. The indentations which make up the track are approximately 0.83 microns long and 125 nanometers deep (Brain, n.d.).

These indentations aren’t always adjacent to each other: sometimes an indent is skipped or multi- skipped and the area between them is left alone. This pattern is referred to as “pits” and “lands”

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(Stallings, 2006, Pg 191). As the layer of aluminum is pressed over this spiral track, it adheres to this pattern and serves as the reflective medium which is utilized in reading this data.

CD-ROMs are read by hardware devices called CD players. These contain a drive motor to spin the disk and a laser/lens system including an optical sensor to read the pits and lands on the disk. As the CD-ROM is placed in the device, the drive motor spins it between 200 and 500 rpm depending on how far the laser is away from the center of the disk (Brain, n.d.). This difference in speed is referred to as constant linear velocity (CLV), and is necessary if the data is to be read at a constant rate. As the track grows and moves away from the center of the disk, the circumference increase results in there being more data on the outer spirals. Thus, to keep the data read speeds consistent, the drive motor slows the speed of the revolutions (Stallings, 2006,

Pg 191).

As the laser shines on the disk surface, it is reflected back and its intensity is read by the optical sensor. If the laser encounters a ‘land’, its intensity remains constant, but if it encounters a ‘pit’, it is refracted slightly and its intensity is weaker. This change in reflected light intensity is interpreted by the CD player as a 1 or 0 (Stallings, 2006, Pg. 193). Through this pattern of ones and zeroes, the ability to store data digitally is achieved and an optical storage device is born.

The CD-ROM can hold enough data to have its data sampled (retrieved) at 44k times per channel per second, 2 channels per sample and at 2 bytes per channel. It can hold a total of 74 minutes worth of data at this sampling rate which totals up to 783,216,000 bytes of total disk capacity (Brain, n.d.). It is amazing that such a thin plastic looking device can hold such a huge amount of data!

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Several important inventions necessary for the CD came about just prior to its invention.

Two of these, the integrated circuit and the laser, both came in 1958 ("The history of CD", 2005).

Then, in 1965 a man named James T. Russell patented the original CD, and during its refinement, mapped the technology to burn the pits into a plastic base using a laser (Amoha,

2005). Soon afterward, a Dutch physicist name Klass Compaan, with the help of a colleague

Pete Kramer, created a glass disk prototype developed at Philips ("The history of CD").

Two general trends, technology and the audio recording industry, combined to create a powerful motivation to develop the CD-ROM. Music, prior to the CD, was either listened to live, or reproduced using a needle record player or some type of a tape player. James Russell was an avid music listener and created his invention originally with the intent of replacing the record player. He was frustrated by how easy it was to damage recordings and also how much quality was lost simply by the records themselves. He envisioned a record device as small as a computer punch card, something Russell was familiar with. Unfortunately, not many people were interested in the invention until Sony and other music vendors realized the potential and began purchasing rights ("James T. Russell", 1999).

In time, Philips and Sony, two large companies with interests in the audio distribution market, began to develop their own standards for the CD. In 1977-78 both companies demonstrated their version of CD prototype, and in 1979 a decision was made that both companies would collaborate on a single “world audio disc standard”. There were several disagreements about everything from sampling size to word length, but in 1980, with some help from the upper management of both companies, consensus was reached and the standards were set (Immink, 1998). This marked a beginning in the explosion of the CD-ROM distribution phenomena.

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Several innovations were needed to keep the product on the market since this technology was very new. In 1983 approximately 1000 CDs were available on the market, and a Sony CD player, the CDP-101, was doing relatively well. However, after the initial success, the market went flat. A man named Katsuaki Tsurushima and his colleagues at Sony Corporation took the task in hand. It was their goal to improve on the CDP-101 device. Most of the purchasers of

CDs were audio enthusiasts, and since the CDP-101 was a larger device that was not hand portable, Tsurushima believed it should be much smaller. During a meeting, a colleague of

Tsurushima held up a piece of wood about the size of 4 CD cases stacked together and said he wanted it that size. His staff was shocked by the aggressive requirement, but worked to produce the results. The D-50, a walkman sized device that played CD-ROM media was the result, and it was introduced to the market in 1984 ("From a small piece", n.d.).

From the humble beginnings and the struggle that companies like Sony went through to keep the product moving forward, the results have been astounding. In 1990, 28% of the households in the US had CDs, 9.2 million players were sold, and world sales of CDs were close to 1 billion ("This history of CD", 2005).

The original CD-ROM has had several progeny, including some that didn’t meet with as much success. In 1987 Philips demonstrated a new type of CD called the CD-I (interactive) to licensees, and in 1988 the first workable players were distributed to developers. This new CD was meant to merge audio, video and text together in ways that would allow interaction, but the marketing program wasn’t successful. In 1994 Philips changed its approach and advertised the

CD-I as a gaming platform, but the change happened too late: Sony Playstation and Sega Saturn systems were the big anticipated releases. In 1996 Philips decided to cut its losses of close to $1 billion and discontinued the CD-I ("History of the phillips", 2005).

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Another descendent of CD-ROM technology is the MiniDisk (MD). This was a Sony development and was complete in 1991. It was advertised as the “new audio standard”. It was smaller than the CD-ROM and enclosed in a permanent case that would be inserted into a player similar to a walkman. Sony explained that the CD-ROM “was for leisure listening and the MD for enjoying music anywhere and anytime.” Though this product received some success in the

Asian markets, it never did catch on in the United States ("From a small piece", n.d.)

There have been some progeny of CD-ROMs that have met with tremendous success.

The CR-R (read) media contains a special dye that changes its reflectivity if exposed to a high level laser. When it is “burned”, it retains its pit/land configuration and becomes a read many, write once CD (Stallings, 2006, Pg 193). Its close cousin, the CD-RW (read and write) is manufactured out of a material that has two different reflectivities in two different phases, and these can, like the CR-R, be affected by the use of a high power laser. But, unlike the CD-R, this media can be written to, erased and overwritten several times, perhaps as many at 500,000 to

1,000,000 (Stallings). Both of these media have tremendous application with the computer environment as they allow for backup and recovery of file systems, and also the copying and sharing of data. Unfortunately, it also opens up the doorway for the illegal duplication of copy- write materials resulting in revenue injury to the CD-ROM industry.

Currently the most important optical storage progeny of the CD-ROM development is the

Digital Versatile Disk (DVD). It looks similar to its ancestor but has a tremendous advantage: its massive storage capacity of at least 7 fold compared to the CD-ROM. Like the CD-ROM, there have been innovations taking the DVD from the ROM level to the write once, ready many and even the read write reusability level. Its versatility and storage capacity are even making the CD family itself obsolete (Jaffe, 2004).

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The CD-ROM, and optical storage as a whole, has had a profound impact on the electronics and music industries. Its innovations continue to progress, and with the billions of

CDs and DVDs owned by the average person today, it is reasonable to assume that optical storage products will be around for a long time. Truly they have made a tremendous contribution in society.

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References

Amoah, Y. (2005, Mar). A brief history of the CD technology. Retrieved on May 24, 2007 from

http://www.ece.drexel.edu/courses/ECE-E443/History_Yoba.ppt#256,1,A brief history of the

CD Technology

Brain, M. (n.d.). How CDs work. Retrieved on May 24, 2007 from

http://computer.howstuffworks.com/cd.html

From a small piece of wood. (n.d.). Retrieved on May 25, 2007 from

http://www.sony.net/Fun/SH/1-21/h1.html

History of the phillips CD-i .(2005). Retrieved on May 25, 2007 from

http://www.philipscdi.com/history.htm

Immink, K. A. S. (1998). The CD Story. Retrieved on May 25, 2007

from http://www.exp-math.uni-essen.de/~immink/pdf/cdstory.pdf

James T. Russell: the digital compact disk (1999, Dec) Retrieved on May 25, 2007 from

http://inventors.about.com/gi/dynamic/offsite.htm?site=http://web.mit.edu/invent/iow/russell.

html

Jafee, J. (2004, Feb). To CD or not to CD: are CD-RW drives obsolete? Retrieved on May 25,

2007 from http://reviews.cnet.com/4520-3207_7-5121193-1.html

The history of CD technology. (2005). Retrieved on May 25, 2007 from

http://www.oneoffcd.com/info/historycd.cfm

Stallings, W. (2006). Computer Organization & Architecture Designing for

Performance. Upper Saddle River, NJ: Pearson Prentice Hall.