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David Paul Gregg

From Wikipedia, the free encyclopedia

David Paul Gregg (March 11, 1923 – November 8, 2001) was an American engineer. He was the inventor of the optical disc (disk). Gregg was inspired to create the optical disc in 1958 while working at California electronics company, Westrex, a part of Western Electric. His patent for a "Videodisk" was filed in March 1962 (USPO 3350503) while working to advance electron beam recording and reproducing.

Gregg went to work at 3M's Mincom division with experienced television videotape engineers Wayne Johnson and Dean De Moss. The three men subsequently filed patents to cover a disc-recording system, a way to duplicate discs, and reproducing TV signals from photographic discs. When Mincom contracted Stanford's SRI to further the research, Gregg left and formed his own company, Gauss Electrophysics.

In 1968 the Gregg and Gauss patents were purchased by MCA (Music Corporation of America), which helped develop the technology further. His designs and patents paved the way for the LaserDisc, which helped with the creation of the DVD, compact discs, and MiniDisc.[1] In 1963 he also invented a video disk camera which could store several minutes' worth of images onto an optical video disk. There was no patent files for the camera and only little is known about it. Gregg died in Culver City, California in November 2001 at the age of 78.[2]

When Gregg had improvised his invention, he imagined himself as a consumer. He interpreted that the LaserDisc (also known as the optical disc), "had to be of extremely low-cost, which implied the utmost simplicity, lowest material and processing costs, and user friendliness."

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Transcription

Laserdisc. A product with an unknown purpose that was both a few years too late and way too far ahead of its time. That’ll make more sense later on, but I want to begin this exploration of the format with my personal astonishment when learning of it. Being a child of the nineties, I fondly remember our first DVD player. It was amazing, you could freeze frame in perfect clarity, search by chapter, change the soundtrack, and enjoy vastly superior picture quality over VHS. Oh, and you didn’t have to rewind. It really was the coolest thing, and I remember the entirety of my fourth grade class considering our teacher a hero for buying a DVD player so we could watch Schoolhouse Rock. Fourth grade was also when I learned what a Laserdisc was. Our class took a trip to the school library to watch a laserdisc teaching us about being safe around electricity. I fully expected “Laserdisc” to be a weird non-specific way to refer to a DVD, and was really surprised when the librarian grabbed this absolutely giant disc from a box and put it in this weird machine to play it. Somehow that memory stuck with me, and in seventh grade I researched what Laserdisc actually was. And boy was I surprised. Laserdisc was THE first optical disc format, providing high resolution analog video, with nearly all the features of my beloved DVD. You had chapter search, you had multiple audio tracks, you had the better picture, you had trick play features on some discs, and more. And you had this starting from 1978! Why hadn’t I heard about Laserdisc before? Why weren’t they more popular? To find out, we need to go back in time to when it was released. Laserdisc was the culmination of the work of many people and companies, with the earliest work being credited to David Paul Gregg in 1958. Maybe. I’m gonna go on a slight tangent here and address some apparent patent and date confusion on Wikipedia’s part that seems to have migrated elsewhere. Although 1958 is referenced as the year Gregg invented it pretty much on any site talking about Laserdisc, there are weird inconsistencies in many places. For example, The Wikipedia entry for Optical Recording again tells us Gregg invented a transparent video disc in 1958, and that it was patented in 1961 and 1990, bizarrely. Now when you scroll down to the actual patent citations, the years right there are 1969 and 1970. Hmm. And the filing date of the videodisc patent was 1967, but that’s good six years off from 1961. The rather sparse article on Gregg himself references a completely different patent. This article says Gregg was “inspired to” create the disc in 1958, so that’s different, and the referenced patent is the earliest one we’ve yet seen, being filed in 1962 (though it’s referenced in the article as 1961). But further muddying the waters, that patent wasn’t too specific on what he intended his technology to be for. Though Wikipedia references US patent 3350503 as being for a “videodisk”, there’s nothing in that patent that exclusively defines it either as being for video or indeed a disc. That patent mainly describes his work using an electron beam and a medium which can modulate a signal by inhibiting secondary emission from that beam as a new means of media storage, different from the then conventional use of ferrous particles in magnetic tape. While video reproduction does seem to be the main goal of this system, the patent drawing and explanation of operation applies this encoding technique to a tape. However, the patent does discuss the possibility of a disc using this new recording technique, and perhaps that’s why it’s referenced. In any case, although this patent doesn’t really relate to Laserdisc that closely, the patent’s main point was that using an electron beam as a scanning method could store information more densely than magnetic tape. It seems likely this revelation led Gregg to his next patent, which is the one we really want to see. US Patent 3430966, filed just over 5 years later in April of 1967, is the one we really need to talk about. This patent describes a transparent disc which reproduces video or other signals by modulating the strength of a light beam shining through it. That’s more like it. Gregg’s concept from this patent is nearly exactly what Laserdisc does. I know patent dates can be confusing, particularly with the differences between priority date, filing date, and actual publication, but there seems to be some very questionable info floating around being regarded as fact. It seems the 1958 date comes from Gregg’s own words, and I did find a source courtesy of the source material from the Today I Found Out article accompanying their recent video on this subject that suggests as much--links are in description for a lot of this. In short, Gregg’s video disc used a light source shining through it to recreate a signal. To quote the patent, Now a funny little fact that I’d like to throw in here is that a somewhat similar system had been in place for audio signals on motion picture film for decades. Lee De Forest, that’s right, the radio guy, had developed a sound-on-film system that first came to commercial use in 1923. In this system the sound signal is photographically etched on the film, and a light source through it with a sensor on the other side, can reproduce honest-to-goodness sound. This very much is the sound waveform with a tiny sliver of light projected through it, and the light sensor on the other side will produce an output which can drive a loudspeaker. And in the ultimate gesture of backward compatibility, later digital sound formats would squeeze their soundtracks between the sprocket holes in the case of Dolby Digital sound and in the tiny space to the left of the sprocket holes for DTS Digital Audio, still leaving room for a stereo analog optical track where it always had been. Now this isn’t to say that Gregg’s work was a rip-off of sound-on-film technologies. Not even slightly. Sound-on-film generally used the width of the track to determine amplitude, and its information density was pretty poor. By confining a light beam to a single spot, a very fine spiral groove could be made, which is much more space efficient. Gregg’s patent image is similar to the pits and lands system that would be incorporated into Laserdisc. The light was either completely blocked or completely unobscured. There were no grey areas, so a half-strength signal would be recorded with a section repeatedly going high-low-high-low, almost like an analog application of pulse-width modulation. In fact, his patent states “optical recordings representative of video signals formed on at least one side of said record member in the form of an intermittent opaque deposit...said opaque deposit selectively interrupting the transparency of said transparent material along said track”. Patent language is fun. MCA, the Music Corporation of America, bought Gregg’s patents in 1968. MCA owned the largest collection of motion pictures at the time, and saw this system as a way to potentially sell movies for home use. The electronics company Philips was simultaneously developing their own system which used a reflective disc. Philips and MCA would team up to produce the first commercially produced system, which was called… Discovision. We’ll need a moment to process that. I..I mean it’s clever, Disc-o-vision, but they went all out on the Disco thing. The original disc jackets featured the movie poster behind a V-neck Disco suit. Ugh. Discovision was released in one test market, the metro area of Atlanta, Georgia, at the tail end of 1978. It would slowly creep out to the rest of the country, but it had a troubled history from the very beginning. The MCA-Philips partnership didn’t last, in part due to production issues that we’ll look at later, and Pioneer of Japan bought the rights to the format, mercifully renaming it Laservision. Not Laserdisc? You ask? Well, Laservision referred to the format’s standard, with all discs and players bearing this mark (similar to the Compact Disc logo). LaserDisc was technically Pioneer’s brand name, with any discs or players featuring the LaserDisc logo being manufactured exclusively by Pioneer. However, the LaserDisc name quickly became a catch-all term for the format, and so it was nearly universally referred to as Laserdisc. But you wouldn’t find Pioneer’s classic beam-split logo anywhere but on their machines. Laserdisc improved upon Gregg’s work in two ways. First was the reflective nature of the discs. The most impactful thing this allowed was a double sided disc, although Greg’s patent did suggest a double sided transparent disc would be possible via changing the the focal point of the projected light beam, sorta like Dual-Layer DVDs. But Gregg hadn’t yet come upon the laser concept, probably because lasers were brand new experimental technology at the time he filed his patent, and this new approach dramatically increased the density of the recording because a laser can be focused down to a tiny tiny spot. Also a minor change that would remain in place for all optical formats going forward was the decision to read the disc from the inside out, unlike conventional records of the time. A Laserdisc is read just like CDs, DVDs, and Blu-Ray discs. A laser focuses a beam of light on a tiny spot, and this beam gets reflected back to an optical pickup, basically a light sensor. The surface of the disc is covered in pits that move the beam’s reflected path away from the light sensor. And these pits create a signal in the optical pickup by continually varying the amount of light it receives. The odd thing about Laserdisc, though, is that the pits produce an analog signal mixed with a whole bunch of other stuff. Digital formats use the pits and lands, lands being flat spots, to encode either zeros or ones. That means there’s only two different results--either the beam is reflected into the sensor, or it isn’t. But the pits of a Laserdisc aren’t encoding zeroes and ones. This is one of those things that’s really mysterious about Laserdisc, particularly when you keep in mind that this stream of pits and lands somehow encoded analog video, two discrete stereo audio tracks with 4 tracks total, indexing information to tell the player where it is along the disc, and later digital sound and even 5.1 channel surround sound. All in a single stream of pits and lands. To roughly equate to analog terms, bright portions of the image will reflect the beam back to the sensor more often, and dark areas won’t reflect much of it at all. Don’t worry too much about what all is tucked into that signal besides the video, because your brain will start to hurt. But one of the coolest side-effects of this analog encoding scheme is that CAV discs, which are the standard play length of 30 minutes per side, allow you to see the structure of an analog video signal. Each of these blocks is an individual scan line, with the gap between them being the horizontal blanking interval. Twice along the disc you see this chunky portion, and this is part of the vertical blanking interval. The scan lines in the vertical blanking interval are all at the blacker than black pulse intensity, and that’s why it stands out so clearly from the rest of the disc. CAV laserdiscs complete one revolution per frame of video, which is why this pattern appears so nicely. You can learn more about analog video through my playlist on Television. Now that you know the basics and early history of the format, it’s time to take a look at one of the earliest Laserdisc players. Ever since I found out about the format, I’ve been transfixed by this particular machine. The Wikipedia article shows a Magnavox player which just looks so radically different than any piece of A/V equipment out there, and I’ll link to a very strangely thought out promo video featuring Leonard Nimoy promoting this new product. Someday I would have to own one of these players. And now, I do! And, uh, it doesn’t work. Which really sucks. But these Magnavox players are notorious for being incredibly unreliable, and I never expected it to. It shows some signs of life, it will spin a disc and its laser works, and it can produce an very unstable black and white image, but that’s it. It’s trying so hard! That’s OK, though, because what I really wanted it for was a display piece, and to make this series of videos. Perhaps I’m the only one with this opinion, but I think this machine is the one of the most beautiful pieces of A/V equipment ever produced. I love how they styled the lid to make it obvious that this plays a disc. It’s simultaneously simple, elegant, industrial, and Starship-Enterprisey. And in a time period filled with simulated wood grain cabinets, its silver and black color scheme set it apart and also in my opinion makes it easier to appreciate today. I’m going to cheat and pretend that this works so you can see how to use it. This machine is a top-loader, another plus in my book, and discs are placed inside like this. The discs, by the way, are 12 inches, or 30 centimeters, across. And MCA likely had a large part in that decision, as it meant the same packaging could be used for Laserdiscs that was already in circulation for 12 inch vinyl records. When the lid is closed this machine automatically beings, trying anyway, to play the disc, and being an early player, it takes a little while for the nearly half pound disc to get up to the almost unsettlingly fast 1,800 RPM, or 30 revolutions per second. (Slow building whirring sound with increasing intensity) The controls on the front all do what they say they do, and this machine enjoyed most of the high-end features Laserdisc had to offer, like video split into chapters, Freeze frame on CAV discs, which also allowed smooth slow motion and fast forward capability, and instant random access to any part on the disc. When you put this machine next to a VCR of similar vintage, the VCR seems almost laughably primitive. And yet, very few people ever purchased a Laserdisc player, well at least few people outside of Japan where the format did achieve modest success. But why? What would make a format with most of the features of DVD, which in case you forgot quickly killed VHS sales once players reached a competitive price-point, fail to capture the imagination of consumers of the time? The most often cited problem was cost. This was very true later on, but initially a laserdisc player was actually much cheaper to own than a VCR, either Beta or VHS. Stay tuned for the next video where I’ll do a deep dive into these two machines, and you’ll soon discover that they never really were competing with each other at all. Thanks for watching, I hope you enjoyed the video. If this is your first time watching Technology Connections, please subscribe so you won’t miss the next ones. This video has been brought to you by supporters on Patreon, and I’d like to give a special shout-out to these patrons who get their names in lights. Patrons of the channel have allowed me to spend more time bringing these videos to you. And if you’re interested in supporting the channel as well, please check out my Patreon page through the link on your screen or down below in the description. Thanks for your consideration, and I’ll see you next time!

See also

References

  1. ^ https://www.mediacollege.com/video/format/laserdisc/patents.html
  2. ^ "David Paul Gregg". AncientFaces. Retrieved 2019-01-07.

External links

Gregg, D. P. (1997). Patents and inventorship issues over the last thirty years of optical storage. Paper presented at the , 3109(1) doi:10.1117/12.280678


This page was last edited on 25 May 2020, at 15:24
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