Optical Recording

The predecessor of the CD

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.

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.

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.

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.

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 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."

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.

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.