The development of the technology for the CD was — as is often the case in industrial developments — a matter of trial and error. It actually all started with a failure. In 1978, Philips launched a video disc onto the market that was scanned by a laser. The plan was for the video disc player to take up a permanent place alongside the TV, which by then had penetrated almost every living room and every school. ‘Nothing could be more logical than to use all the TVs to play pre-recorded images’, it seemed. But things were to turn out differently.
The predecessor of the CD
Left: First Philips VLP player, right: Philips ALP Pinkeltje development model for compact disc
Video Disc: Predecessor to the CD
In many respects, the video disc was a forerunner of the CD. The video information was recorded on the disc by means of a pattern of pits. The idea of using a laser to read this information without any contact also proved to be a durable concept. The inventors of the video disc therefore also contributed to the invention of the CD later on.
The Evolution of Video Disc Technology: Pioneers and Innovations
But who were they? Was it the Italian Rubbiani who, watched by a Philips researcher, demonstrated a primitive video disc at the Salone Internazionale della Tecnica in 1957? Was it the technologists at the American CBS who a few years later developed a procedure for a video disc? Or perhaps the research group at 3M who in 1964 made a video disc that was plagued by snow in the picture? The answer is yes and no. The inventions of these laboratories bear little resemblance to the video disc that Philips was to develop. Nevertheless, reports about these technologies did encourage Philips researchers to think more deeply about the video disc. Work was already being carried out on video recorders, but a lot of tape was required for a feature film.
Antonio Rubbiani
Antonio Rubbiani, from Modena, Italy, has devised a device that reproduces the image and sound of a pre-recorded television program. The photo shows the inventor during one of the tests of his device.
Antonio Rubbiani
It records photographically the scanning lines of a TV image on a Plexiglas disk, which moves on a turntable, under a high-powered light. A photocell collects the light and transmits it to the receiver to reproduce the image.
Rubbiani states that the distortion seen on the screen is due to the malfunction of the electric motor that drives the turntable.
A Collaborative Effort at Philips Research Laboratories
The research was stimulated initially by a small group of specialists outside Philips Research Laboratories. Wols and his colleagues were responsible for educational equipment within the ELA division. They saw that there was money to be made by combining a cassette recorder and a projector. They were looking for something that could produce both image and sound and that could move quickly backwards and forwards from one part of the program to the other, i.e. a disc with images and sound.
This group contacted Philips Research Laboratories to ask for help. Would it be possible to produce a video disc that would enable any image to be located at random, without the need for extensive winding?
In these early stages the direction of the research was set by a number of Philips employees. Hajo Meyer was one of the directors of Philips Research Laboratories at the time and he was a great inspiration to the research. Piet Kramer, the head of the optical research group at Philips Research Laboratories, conducted research into the technology for the video disc. Klaas Compaan, a technical expert in Wols's group, carried out extensive practical work, and Gijs Bouwhuis, a researcher at Philips Research Laboratories, worked intensively on the necessary optics. Anyone trying to ascertain at what point in time the video disc was invented, and thus also the CD, will inevitably end up in the canteen, which is where ideas are discussed and dismissed, or in meetings, where the experts struggle to solve technical problems. "We met up every Monday morning, some ten of us together, to brainstorm about how we should proceed and what contribution each of us could make," recalls Kramer.
A Pioneering Journey
The first research into the video disc, in 1969, continued along the lines of Rubbiani’s video disc. The surface of the disc was covered entirely by small images. Each film image was thus recorded in its entirety. At that time that was the most obvious way to record the large quantities of information from a feature film. When the film was shown, the images were projected one after the other in quick succession.
In order to keep the disc a convenient size, the images had to be no larger than one square millimeter. "We had a photographic process from the manufacture of the first chips which we were able to use to do this," Piet Kramer explains. "We had all the necessary technology. Within three weeks a prototype was ready."
The German competitor Teldec (Telefunken/Decca) had also shown this with a video disc. They had made a gramophone record with microscopically small grooves. A needle and a piezoelectric recording element were used to reproduce the video signals.
The Race to Revolutionize Video Discs
The greatest problem was how to duplicate the film discs, for that too had to be done photographically. With these microscopically small images it was essential to avoid any dust whatsoever. This would have made the reproduction time-consuming, laborious and expensive. "That is why we never did it," says Piet Kramer. "We didn’t see how it could ever be worthwhile because we knew from our experience with the chips technology what a struggle it would be. That is why we gave up on the idea of recording the images in their entirety. Instead, we decided to find a way to record the image signals, the information from the individual picture lines," says Piet Kramer. After all, using a TV transmitter this method can be used effectively to transmit images at high speed. "We knew from the gramophone record with just what sort of mechanical precision signals can be recorded and reproduced. In a surface like that it is possible to carve details of less than a micrometer. That was enough for a video signal."
However, a disc of this sort is very susceptible to wear. Contactless scanning using light signals seemed a better idea. "We knew it had to be possible. After all, you could see even smaller details using an optical microscope," Piet Kramer points out. Other technologies were not considered appropriate. Magnetic recording, as had been used in the Compact Cassette, was not refined enough to fit sufficient information on a small surface area.
"Teldec was ahead of us. One thing was certain, we had to be better than they were. Without delay we had to show the world that we had something better to offer," says Kramer. Whoever launched the video disc onto the market first would set the standard. That is what happened with cassette tapes and later with video tapes. Whoever came second would only stand a chance if their video discs were available very soon afterwards and were significantly better.
At the time there was only a small research group working on the video disc. The core of the team was made up of seven people, but they could feel the competitors breathing down their neck. It later transpired that the American companies RCA and MCA were working on a video disc, as was the French company Thomson.
1977 - Here at last - video-disc players
Sometime this year, TV viewers in selected areas of the country should be able to schedule their own shows in an entirely new way. They'll select movies, musical per-formances, or other material on video discs, slip the discs into players wired to their receiver's antenna terminals, and push a button to watch the show.
Video Disc players - Popular Science - February 1977
A long list of glittering new video players has been promised. post-poned, or introduced in recent years, only to fade from sight. But there definite signs that at least two major worldwide organizations with the financial muscle and marketing know-how to succeed will begin selling their video-disc players regionally in 1977.
One of them, RCA, is already field-testing a few hundred of its capacitance-sensing Selecta Vision disc players. N.V. Philips, the Dutch firm that brought us the standard audio cassette, and MCA Inc., an American entertainment-oriented firm, also plan to offer an optical video-disc system this year. The latest price estimates: about $500 for the player, and $10 to $18 for a disc or set of discs.
There's even a possibility that a Japanese licensee of a British and German disc venture, the grooved-disc TED system [PS, Nov. '74], could be marketing disc players, too. Players for 10-minute TED discs have been available in Germany since 1975, although only for European TV-signal standards, Sales have been poor. A TED changer that handles 12 discs was recently shown. Spinning on the sidelines are other disc systems still under development see box: "In the labs: machines that record and play discs".
Both the RCA and Philips/MCA players will appear in stores just when new home video-cassette recorders [PS, Dec. '75], video games [PS, Nov. *76], and pay-cable programming are teaching viewers that their TV receivers can easily display something other than fixed-time broadcast fare. What's different about the new disc hardware and programming?
After operating both the RCA and Philips/MCA players, trying some amazing manipulations of TV images, and listening to stereo hi-fi TV sound I found that the new machines offer spectacular gains in performance compared with other home program sources.
Stamping out tons of discs at low cost is the biggest advantage of the new medium. Both Philips/MCA and RCA expect to offer a broad selection of discs when their players appear. MCA, which will manufacture most U.S. discs for the Magnavox-built player, plans 1000 albums initially. MCA discs will include new and old films, ballet, opera, theater, sports, how-to and children's pro-grams, and documentaries. MCA can also make a thin flexible dise that might be inserted in periodi-cals. Discs may also be distributed as entire magazines, catalogs, or talking encyclopedias. Also, a variety of independent companies will add other special-interest dises to catalogs. One firm, Visiondisc Corp. of New York, for example, planned to tape last year's Christmas services and works of art at a large cathedral for transfer to discs.
Here's how the two leading players and disc formats differ:
RCA's SelectaVision
This machine is designed to play a rigid, grooved disc 12 inches in diameter and programmed on both sides with 30 minutes of material. The function of the spiral groove is to guide a stylus, much as in an audio-disc system. But that's the end of any similarity to familiar 33-1/3- or 45-rpm discs. The Selecta Vision player which won't operate unless the lid is closed, spins discs at 450 rpm.
A technician slides a SelectaVision video-disc player into its outer cover at RCA's new plant in Indianapolis
TV signals are encoded as minute rectangular depressions at the bottom of each groove. The slots vary in spacing and width, with some as narrow as 0.25 microns (millionths of a meter). RCA devised a method of producing the slots on a disc master, using a sharply focused electron beam, since required widths are too narrow to be generated optically with light. The discs have a vinyl base topped with thin layers of metal, an insulating plastic (dielectric), and an oil lubricant that reduces stylus wear. Together, the disc and metal-tipped stylus form an electrical cir-cuit. As the slots spin past the stylus, tiny abrupt changes in circuit capacitance occur. These changes detune an oscillator circuit to produce the TV signal.
To compensate for small changes in rotational speed, a tiny trans-ducer, which functions somewhat like a loudspeaker coil and cone, stretches the stylus arm back and forth parallel to the groove. Errors in speed are detected by monitoring the recorded color-burst signal. A close look at a SelectaVision player confirms RCA's disc-system-design philosphy. Components are housed in a simple, inexpensive cabinet with a minimum number of controls. Internal circuit boards and components, prominently displayed on a pegboard in RCA's New York demonstration room, remind you of a Heathkit spread out for assembly.
RCA deliberately designed a player that could be easily mass-produced with relatively standard parts. Care is necessary when loading discs in the machine, since fingerprints or smudges can create inter-ference. Playing dises repeatedly through can remove contaminants from the grooves, but since the $15 stylus must be replaced after 200 to 300 hours of use, it's wiser to take good care of records. Each disc can be played about 500 times.
Pictures I've seen at several demonstrations were excellent. You can rapidly move the tangential stylus arm forward or backward to selected disc areas by pushing but-tons; a lighted index on the panel becomes larger or smaller. A pause button breaks stylus contact. 'The player has two audio channels for stereo or bilingual programming, and audio output jacks for optional connection to a hi-fi amplifier.
Philips/MCA player
This concept differs radically from Selecta Vision. Only the center spindle touches Philips/ MCA discs as they spin at 1800 rpm. An air bearing that develops at that speed aids stabilization. A low-power laser beam, focused to a one-micron spot, strikes the bottom surface of the aluminum disc (see diagram). This highly reflective layer has a clear-plastic protective coating.
An early version of the Philips VLP600
The beam falls on a spiral track that consists of oblong bumps of varying lengths, with flat areas between them. The encoded picture information varies the distance between bumps. Part of the laser light is reflected from the flat area between bumps back through the optics to a light-sensitive diode that detects the TV signal. Only one side of a disc is programmed, with 30 minutes of material. By shifting the beam spot slightly on the spinning disc, three sophisticated servo circuits maintain focus, tracking, and proper speed.
The servos sense deviations by monitoring auxiliary beams reflected from the disc. Corrections are made with electronic signals that can shift the focusing lens up or down; or, to compensate for radial (sideway) and speed errors, two mirrors positioned at right angles to each other can be pivoted to shift the beam spot.
Jolting a player
Despite the extraordinarily small tolerances involved, the servos do their jobs remarkably well. Even a sharp rap on the Philips/MCA player case- -enough to jolt an au-dio-cartridge stylus from its groove- does nothing, or produces only a brief flicker on the picture. Philips/MCA discs can be handled easily without concern for smudges or dust. The thick protective coating keeps blemishes out of focus, which prevents picture in-terference. Discs should last indef-initely, since there's no wear from playback. The helium-neon laser "stylus" lasts a minimum of 10,000 hours before replacement may become necessary.
There's a distinct look and feel of compact precision to the Philips/ MCA player. The front panel is packed with controls that capitalize on the contactless readout and the fact that each revolution of the disc produces one TV picture. One button lets you indefinitely freeze any one of 54,000 picture frames for in-depth viewing on the screen. Other controls enable you to advance the picture sequence manually, frame by frame, forward or backward. A variable-speed control does the same thing automatically.
Counting frames
In the fast-scan mode, pictures become a blur; however, every few seconds one is frozen for an instant to help pinpoint a location. All Philips/MCA discs will be encoded with signals that serve to identify each frame. Tap another button and the frame numbers appear in a corner of the TV screen. The player has stereo hi-fi output jacks and a video-output jack (a non-RF signal).
Both RCA and Philips/MCA have invested perhaps several hundred million dollars without knowing whether consumers will buy the players and discs to program their own shows. If the spectacular climb in sales of video-cassette recorders, TV-game, and pay-cable systems are any indication, the video-dise manufacturers have made a shrewd investment.