Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/3/84; site teddy.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxn!ihnp4!qantel!dual!lll-crg!seismo!harvard!talcott!panda!teddy!rdp From: rdp@teddy.UUCP Newsgroups: net.space Subject: Re: potential space product Message-ID: <1383@teddy.UUCP> Date: Thu, 3-Oct-85 15:58:32 EDT Article-I.D.: teddy.1383 Posted: Thu Oct 3 15:58:32 1985 Date-Received: Sun, 6-Oct-85 05:39:59 EDT References: <3725@mordor.UUCP> Reply-To: rdp@teddy.UUCP (Richard D. Pierce) Organization: GenRad, Inc., Concord, Mass. Lines: 43 In article <3725@mordor.UUCP> @S1-A.ARPA,@MIT-MC.ARPA:john%taveis.DEC@decwrl.ARPA writes: > > Luneberg expanded on Maxwell's work. He found a scheme where a perfect >image could be produced of an object at infinity, with both the image and >object in air (i.e. n=1). His lens is a sphere with an index of refraction >that varies with the distance from the center of the sphere (r) as > >n(r) = (2 - r^2 / a^2) ^1/2 r < 1 > = 1 r > 1 > >where 'a' is a constant. > > The varying index was thought to make the lens impractical. However, >n can be changed by doping glass with various impurities, and in fact this >is done regularly in fiber optics. How, though, can this be done for a >sphere instead of a fiber? > > By building it in weightlessness. The sphere would float in the middle of a >vacuum chamber. Glass would be deposited on it one layer at a time, with each >layer having the appropriate index. The glass vapor would flow into the >chamber continuously, and its doping would vary continuously. The >weightlessness would give perfect spherical symmetry. Glass deposition is a >standard feature of semiconductor processes; equipment for it is readily >available. Building up a sphere of any size, however, might take some time. > Several optical manufacturers have been doing research along these lines, with names like Canon and Nikon coming to mind. In fact, variable refractive index lenses have been done for some time, under normal, gravity-laden conditions. The technique involves taking a lens blank and "cooking" it in a silver-salt (silver halide) soup for some time. Appropriate ions diffuse into the glass from the surfaces at a rate determined by, among other things, concentration, glass characteristics, temperature, surface area, and so forth. The technique has been suffiently perfected to make it commercially (albeit expensively) feasable, although I am not specifically aware of actual products that utilize this technique. I myself developed a simple technique for lower the diffraction of so-called "difraction limited" optics, thus raising the resolving power, but I will not digress because a) this is probably the wrong news group, b) It might be something really neat, and patentable (but I don't think so), and c) I don't feel like it right now :-). Dick Pierce Brought to you by Super Global Mega Corp .com