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CED Patents Table

RCA was always heavily into patents, as the corporation had derived a great deal of licensing revenue from these over the years, first with radio and broadcasting patents and later with television patents. RCA had a Patents Operation Division directly under a Vice President to ensure that everything which could be patented was patented. Thus, there are CED patents covering a wide range of system parameters, both in the manufactured product and in the processes used to manufacture it. At first glance some of the patents in the table may appear to have nothing to do with CED, as some of the early manufacturing processes were abandoned and other processes deal with the manufacture and testing of discs and player parts and were well-known only to RCA employees. These processes include:

• Electron Beam and Optical Recording Techniques: RCA experimented with both of these techniques to make CED masters during the design phase, but chose electromechanical recording for the final product.

• Injection Molding of Discs: Another technique experimented with but abandoned. The final product used compression molding.

• Metallized Dielectric Discs: Initially the system used plastic discs with a very thin metallized layer topped with another thin dielectric layer. RCA later found the disc could be made from homogeneous PVC doped with conductive carbon black particles, and this was used for the manufactured discs. Oddly enough, some later research found the discs could be manufactured less expensively using a modified composite structure, which may have been implemented if the system had survived longer.

• Glow Discharge Techniques: RCA had to invent the techniques necessary to machine diamond styli at microscopic dimensions, and among these was the glow discharge of silicone dioxide onto discs used to lap the diamond blanks. Glow discharge was also used to deposit dielectric layers in the early CED system.

• Optical Scanning and Playback of Discs: These patents may at first seem to relate to MCA/Philips LaserDisc technology, but RCA had two major areas of research relating to optical disc techniques. The first, which applies directly to CED, was for the optical playback and scanning of CED masters, intermediaries, and finished discs. The copper masters were quite reflective, and RCA developed laser playback systems that could play these back to a video monitor to check for defects. This allowed the masters to be thoroughly tested without any influence to the surface prior to the additional replication steps. Optical techniques were also used to scan for defects on random samples of finished discs. Patents relating to these CED optical techniques are included in the CED Patents Table.
  RCA's other major area of research in optical disc technology was for their Read/Write Trilayer Optical Disc system, in which a laser at high intensity writes the disc, and the same laser at lower intensity is able to read back the high density recording. Patents relating to this system are not included in the CED Patents Table, but many can be found from the patent links on the biography pages of Robert Bartolini and Alan Bell, who were the two principal RCA researchers in the technology.

• Charge-Coupled Device Technology: CCD's are most commonly associated with the imaging elements in compact camcorders and digital cameras, but early on, RCA's development of CCD's for use in television comb filters made possible the Buried Subcarrier encoding used on CED's. This allowed the CAV discs to spin at a comparatively slow 450 RPM while still providing a 3 MHz luminance bandwidth with the chrominance subcarrier "buried" inside the luminance frequency band.

• Piezoelectric Recording Techniques: The piezoelectric effect wherein a crystal produces a voltage related to mechanical stress is commonly associated with the Teldec VideoDisc system, which was the first modern VideoDisc system to be marketed starting in 1975. This system reproduced the video signal by applying varying pressure to a piezoelectric transducer skimming over the disc surface. RCA also used the piezoelectric effect for master recording, but in a reverse sense, i.e. a mechanical deformity occurs in the CED cutting element proportional to the electric field applied.

While researching the CED patents to include in this table, I came across a number of patents relating to other VideoDisc technologies that emerged about the same time as CED, like the Teldec system mentioned above. These patents are not included in the CED Patents Table except in rare instances where I thought their inclusion was important such as an early Sanyo patent dealing with caddy-housed Piezoelectric VideoDiscs that may have influenced RCA's later decision to use caddies; or the Toshiba patent on a recordable VideoDisc system they demonstrated at the 1983 CES, which some in the technology press dubbed "The Recordable CED" when the technology was semiconductor-based rather than capacitive.

Since I sometimes get email asking where to find information on the various VideoDisc technologies that emerged around the time of CED, I'm including a separate table for finding patents related to these other VideoDisc formats. Searching the patent databases for the term "VideoDisc" is often ineffective for early patents as the term was not widely used at the time. RCA called them "High Density Information Records," and other terms I've seen include "Audiovisual Records" and "Picture/Sound Records." A more effective search technique is to use the Assignee field (typically the company receiving the patent, like RCA) to search through all the patents issued to the company backing the VideoDisc system of interest over the span of years the system was being developed and patented (early 1970's to mid 1980's for most of these). Then any patent that from the title appears to be VideoDisc related can be investigated further. Another search method that is faster, but may miss some relevant patents is to do an AND search where the Assignee field is ANDED with the Title or Abstract field on terms like "Disc," "Disk," and "Record." The table below lists the various VideoDisc technologies contemporary to CED, the common names for the technologies, and the major assignees:

• Delphion Intellectual Property Network:
  IBM was the first provider of patents on the Internet, and Delphion is a spin off formed in 2000. This was my preferred way to browse patents and used to be free, but the company has since imposed a monthly fee if you want to see more than the first page of the patent. The first page is in PDF format, which may be easier for some browsers to view than the TIFF format used by the US Patent Office.

• US Patent & Trademark Office:
  The USPTO now provides the means to view all CED patents, where previously it only went back to 1976. Patents back to 1976 can be viewed either in full text or as images, while those prior to 1976 (marked with asterisks in the table) can be viewed as images only. The USPTO web site allows all the CED patents to be viewed in their entirety for free.