lindsay@k.gp.cs.cmu.edu (Donald Lindsay) (08/16/87)
Mach 1 is irrelevant to a truly advanced read/write laser disk. The first commercial units will spin, but eventually, we will just scan the laser beam across an unmoving disk. ( I expect the "disk" to be the back of a credit card, except of course inside the larger, sealed units. ) The technology for scanning a laser beam already exists: I refer you to your favorite supermarket checkout, or, your favorite laser printer. Techniques such as spinning holograms, and spinning hexagonal mirrors, are the low-tech (but well-proven) techniques. The high-tech methods are diverse and I don't care to predict the winner. Perhaps we modulate an index of refraction by ... ... .... ??!! ...naah. Don -- Don lindsay@k.gp.cs.cmu.edu CMU Computer Science
roy@phri.UUCP (Roy Smith) (08/16/87)
In <1189@k.gp.cs.cmu.edu> lindsay@k.gp.cs.cmu.edu (Donald Lindsay) writes: > eventually, we will just scan the laser beam across an unmoving disk. > ( I expect the "disk" to be the back of a credit card, except of course > inside the larger, sealed units. ) Oh wow, sounds like CRT memories all over again :-) -- Roy Smith, {allegra,cmcl2,philabs}!phri!roy System Administrator, Public Health Research Institute 455 First Avenue, New York, NY 10016
gwu@vlsi.cs.cmu.edu (George Wu) (08/17/87)
There's been all this talk about gaining faster mass storage with
parallel operations, and more recently, optical disks. But it seems to me that
a limiting factor are the mechanical parts, which must physically move. Even
using a scanning laser beam to read optical disks, a mirror must be
manipulated, unless someone has found a way to bend light. Relativity anybody?
But what about non-mechanical storage systems? Are there feasible
magnetic and/or solid state systems out there? I remember there used to be a
big hoopla about bubble memory, but I haven't heard anything recently. And I'm
not sure why, but intuitively, I feel that solid state devices would be even
faster than magnetic ones. Is this just a bias left over from magnetic tapes
and drives?
Georgegrunwald@uiucdcsm.UUCP (08/17/87)
In my supermarket, the 'scanning laser at the checkout line' is operated by the checkout person passing the product over the laser (usually several times) at speeds much less than Mach 1. Are there non-mechanical methods of directing a laser beam? Any pointers to references? Dirk Grunwald Univ. of Illinois grunwald@m.cs.uiuc.edu
chuck@amdahl.amdahl.com (Charles Simmons) (08/17/87)
In article <1075@vlsi.cs.cmu.edu> gwu@vlsi.cs.cmu.edu (George Wu) writes: > > There's been all this talk about gaining faster mass storage with >parallel operations, and more recently, optical disks. But it seems to me that >a limiting factor are the mechanical parts, which must physically move. Even >using a scanning laser beam to read optical disks, a mirror must be >manipulated, unless someone has found a way to bend light. Relativity anybody? > > But what about non-mechanical storage systems? Are there feasible >magnetic and/or solid state systems out there? I remember there used to be a >big hoopla about bubble memory, but I haven't heard anything recently. And I'm >not sure why, but intuitively, I feel that solid state devices would be even >faster than magnetic ones. Is this just a bias left over from magnetic tapes >and drives? > > George How about an optical disk with a laser driven by a phased array (as in phased array radar)? (Is there such a thing as a phased array laser?) Or maybe some other storage medium accessed by a phased array? Such a creature would have no moving parts. A few months ago, Byte magazine had an article on a British company that was working on wafer scale integration. There first product was supposed to be a 7 Megabyte solid-state "disk drive". Access to this memory would be serial, but seek and transfer times were on the order of 1000 times faster than seek and transfer times on vanilla disks. -- Chuck
franka@mmintl.UUCP (Frank Adams) (08/19/87)
In article <1189@k.gp.cs.cmu.edu> lindsay@k.gp.cs.cmu.edu (Donald Lindsay) writes: >Mach 1 is irrelevant to a truly advanced read/write laser disk. >The first commercial units will spin, but eventually, we will just scan the >laser beam across an unmoving disk. Doesn't this severely limit the ability to stack more than one disk surface in a device? How close to the disk does the scanning head have to be? How does this depend on the disk size? -- Frank Adams ihnp4!philabs!pwa-b!mmintl!franka Ashton-Tate 52 Oakland Ave North E. Hartford, CT 06108
farren@hoptoad.uucp (Mike Farren) (08/19/87)
In article <3300009@uiucdcsm> grunwald@uiucdcsm.cs.uiuc.edu writes: > >Are there non-mechanical methods of directing a laser beam? Any pointers to >references? A Bragg Cell is an electro-acoustical device which, when an RF frequency is applied to it, changes its effective index of refraction proportional to the frequency of the applied signal. This does very effective beam manipulation. Sorry, don't have references - try a good electro-optics reference. The technology has been around at least 10 years. -- ---------------- "... if the church put in half the time on covetousness Mike Farren that it does on lust, this would be a better world ..." hoptoad!farren Garrison Keillor, "Lake Wobegon Days"
smith@COS.COM (Steve Smith) (08/20/87)
In article <1075@vlsi.cs.cmu.edu> gwu@vlsi.cs.cmu.edu (George Wu) writes: > There's been all this talk about gaining faster mass storage with >parallel operations, and more recently, optical disks. But it seems to me that >a limiting factor are the mechanical parts, which must physically move. Even >using a scanning laser beam to read optical disks, a mirror must be >manipulated, unless someone has found a way to bend light. Relativity anybody? There's a gizmo called an electro optic modulator that works on nonlinear optical effects in crystals. They will "bend light" and do lots of other tricks with no moving parts. They are also very fast. I don't have any current information, but any of the laser industry rags should have lots of ads. Check Electro Optic Systems Design, Laser Focus, etc. From what I remember on these things, there are some problems: 1. Deflection angles are VERY small (~1 degree) 2. They're VERY expensive 3. They require very fast switching of high voltages This information isn't current; I hope they've improved things. Another system that is cheaper but not so fast is called an accousto (sp?) optic modulator. It uses ultrasonic standing waves in a crystal to do its work. Again, I have no current info. -- __ -- Steve / / \ / "Truth is stranger than S. G. Smith I \ O | _ O \ I fiction because fiction smith@cos.com / \__/ / has to make sense."
lindsay@k.gp.cs.cmu.edu (Donald Lindsay) (08/24/87)
>>The first commercial units will spin, but eventually, we will just scan the >>laser beam across an unmoving disk. >Doesn't this severely limit the ability to stack more than one disk surface >in a device? How close to the disk does the scanning head have to be? How >does this depend on the disk size? An unmoving read/write surface would impose geometrical limitations. However, I presume that we will eventually be able to scan beams far faster than we can ever hope to rotate any (large) object. Plus, we eliminate the disk motor, the bearings, the voice coil (or whatever), the comb (and its bearings). We would expect improvements in weight, power, reliability, component count, ruggedness, manufacturabilty, seek time, and transfer rate. For that, I would give up some density. As for HOW we do it: I believe it is too soon to say. I read "Laser Focus", but I probably misunderstand much of what I read. I get the impression that there are several ways to bend a beam under electronic control. Also, we can now modulate the color of certain lasers: who knows where that leads ? Plus, semiconductor lasers benefit from chip technology, and are most definitely still improving. Eventually, "disk" will just be "nonvolatile memory". Trust me. I do not, repeat, not, make misteaks. -- Don lindsay@k.gp.cs.cmu.edu CMU Computer Science -- Don lindsay@k.gp.cs.cmu.edu CMU Compu F F uld
ccjap@bu-cs.BU.EDU (John Papadopoulos) (08/25/87)
Several years ago when I used to work at the "Magneto-Optical Storage Lab" at BU, I was told about some work that had been done at Xerox (PARC?). They were working on a crystaline structure that could be used as a phased array for a laser. The structural (or optical properties) were modified by electric fields. I think they placed some large number of electrodes on four sides of a cube of the crystal and "modulated" the crystal so that the beam exited the crystal in a predictable direction. I think they were thinking of using for a laser printer mechanism. There are some problems though, such as thermal expansion and contraction of the crstal, "speed" of the crystal, and the voltages required (I think they were quite high). But then at a bit density of ~1 bit/1 micron^2... Given one of these beauties, you could use a small section of a planar thin film of magneto-optical material with the crystal suspended above it. One problem with this is that vertical recording is used in some of the more attractive magneto-optical mediums. This requires that the laser beam be nearly perpendicular to the plane of the medium. This limits the surface area to quite a small section. One way around this is to deposit the thin film on the inside of a hemisphere and place the cystal at the focal point of the hemisphere, thus giving a maximal amount of surface area. One thing that I thought would be neat would be to have planar magneto-optic memories and to lay a blank memory on top of a programmed one and somehow make a "photocopy" of the programmed one onto the blank. Now that I what I call fast backups! -John Papadopoulos Boston University