Eric Jacobsen wrote:> On Fri, 04 Mar 2005 15:30:54 -0600, Richard Owlett > <rowlett@atlascomm.net> wrote: > > >>After reading Jerry's post, I started to ask a question. >>But read your post and realized I might ask a specialist. >> >>1. Any WEB available references on how to do Fourier transforms optically? > > > It's a single lens. Maybe a search on Fourier Transform Lens will > turn something up. >Several including "An Intuitive Explanation of Fourier Theory" by Steven Lehar [ http://cns-alumni.bu.edu/~slehar/fourier/fourier.html ] I think its good enough that it should make it onto a FAQ links page.> >>1a. Can I assume the typical demo of interference effects from 2 slits >>converting incident plane wave to 2 sources is a Fourier transform of >>something? Can you tell I've not gone to school in decades ;] > > > Not sure I undertand the question here...?Well that makes at least two of us. From reading Lehar's page, I think I was half remembering a description of something like an optical filter.> > >>2. Did it depend on knowing the incoming carrier frequency? >>IE Given an "optical Fourier transformer" as a 2-port black box. >>Could you feed it an audio signal rather than RF and get out the >>appropriate transform? > > > I think so, and Steve indicated that sonar systems used it. > > The link Jerry provided is to a nice article by some guys at Sandia > and has some pretty amazing SAR pics in it (being able to resolve > footprints would've still been classified when I was working in this > area), as well as a diagram showing an optical processing example (but > it's a bit misleading, it doesn't show how the 2D cross-correlation is > done). >I'm going have to get a better PDF reader so I can extract the text to make it easier to read -- ie single column of text.> As long as the input can be modulated as a collimated light beam you > can do the processing optically, so it should be reasonably > independent of carrier frequency or bandwidth. > > > Eric Jacobsen > Minister of Algorithms, Intel Corp. > My opinions may not be Intel's opinions. > http://www.ericjacobsen.orgThanks
How things change
Started by ●March 3, 2005
Reply by ●March 5, 20052005-03-05
Reply by ●March 5, 20052005-03-05
Eric Jacobsen wrote: ...> As long as the input can be modulated as a collimated light beam you > can do the processing optically, so it should be reasonably > independent of carrier frequency or bandwidth.The ratio of image size to real size is determined in part to the ratio if the reconstructing laser's wavelength to that of the radar's. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●March 7, 20052005-03-07
Jerry Avins wrote:> Richard Owlett wrote: > >> Jerry Avins wrote: >> >>> [snip] It strikingly brought the >>> unity home to me, and convinced me that if I couldn't explain >>> something to an intelligent and interested high-schooler, I didn't >>> understand it well myself. Richard Feynman confirmed my opinion about >>> that. >>> >> >> OK, just how did he do it. >> >> Did a Google search on his name and first several hits were on writing >> very very very small. That didn't seem promising. Am I missing something? > > > He was a Nobel laureate in physics, but he was more. Not only an > outstanding teacher who could see to the core of things, but a bongo > player, magician and ... > > Aw crap, He should be remembered for having said, "Physics is like sex. > Sure, it may give some practical results, but that's not why we do it." > > See http://www.amasci.com/feynman.html. > > You would enjoy reading his autobiography, "Surely You're Joking, Mr. > Feynman". At least one misguided bookstore had it in the humor section, > so look sharp.I found it odd how little his children and wives were mentioned. One could say that the man was private about his personal life but he also talks about how to pick up women in bars, how he liked Las Vegas, and how he liked to hang around topless nightclubs.> > Feynman diagrams illustrate parts of quantum mechanics so even I [think > I] can understand them. > > Jerry
Reply by ●March 7, 20052005-03-07
When I was a youngster (in the 80's) I had a book I bought from Radio Shack that described the concept of digital electronics. It then went through a calculation to show how television could never be digital because it would take too much bandwidth. -Kevin Steve Underwood wrote:> While sorting through some old stuff, I came upon the introductory comms > book I used at college. This book was published in 1971. In the section > on information theory it goes through Shannon and Hartley's work on > channel capacity. It then describes one possible way to get close to > that limit, which is pretty much what we call OFDM (though it doesn't > call it that - when was the term OFDM coined?) and says: > > "We shall see that, to obtain errorless transmission for R<C requires > and extremely complicated communication system. In physically realizable > systems, therefore, we must accept a performance less than the optimum." > > In fact, the whole tone of the description it that the system is > implausible to implement. Just 34 year later, I am sending this through > a 54Mbps OFDM link, and then through a 6Mbps OFDM link. They are both > tiny, consume little power, and cost just a few dollars. I guess I would > call that progress. :-) > > Regards, > Steve
Reply by ●March 7, 20052005-03-07
On Fri, 04 Mar 2005 15:30:54 -0600, Richard Owlett <rowlett@atlascomm.net> wrote:> > >After reading Jerry's post, I started to ask a question. >But read your post and realized I might ask a specialist. > >1. Any WEB available references on how to do Fourier transforms optically? > >1a. Can I assume the typical demo of interference effects from 2 slits >converting incident plane wave to 2 sources is a Fourier transform of >something? Can you tell I've not gone to school in decades ;] > >2. Did it depend on knowing the incoming carrier frequency? >IE Given an "optical Fourier transformer" as a 2-port black box. >Could you feed it an audio signal rather than RF and get out the >appropriate transform? >Hi Richard, I'll bet you'll find something useful if you Google on the combination: "spectrum analyzer" "bragg cell" See ya', [-Rick-]
Reply by ●March 7, 20052005-03-07
Stan Pawlukiewicz wrote:> > I found it odd how little his children and wives were mentioned. One > could say that the man was private about his personal life but he also > talks about how to pick up women in bars, how he liked Las Vegas, and > how he liked to hang around topless nightclubs. >Also, how little attention he payed, apparently, to the medical aspects of his first wife's illness, compared to the in-depth research he carried out (much later) on his own. Tragically, although he was not able to affect the progress of his own illness, possibly a more active interest in his wife's illness at the time may have revealed the mis-diagnosis early enough to have done some good. Regards, John
Reply by ●March 8, 20052005-03-08
On Mon, 07 Mar 2005 14:42:39 -0700, Kevin Neilson <kevin_neilson@removethiscomcast.net> wrote:>When I was a youngster (in the 80's) I had a book I bought from Radio >Shack that described the concept of digital electronics. It then went >through a calculation to show how television could never be digital >because it would take too much bandwidth. >-KevinHa ha. Neat story Kevin. Speaking of poor predictions, check out the following. [-Rick-] -------------------- * "Who in their right mind would ever need more than 640k of RAM (memory)!?" -- Bill Gates, 1981 (100 times 640k is now standard on home PCs.) * "Computers in the future may weigh no more than 1.5 tons." --Popular Mechanics, forecasting the relentless march of science, 1949 * "I think there is a world market for maybe five computers." --Thomas Watson, chairman of IBM, 1943 * "I have traveled the length and breadth of this country and talked with the best people, and I can assure you that data processing is a fad that won't last out the year." --The editor in charge of business books for Prentice Hall, 1957 * "But what ... is it good for?" --Engineer at the Advanced Computing Systems Division of IBM, 1968, commenting on the microchip. * "There is no reason anyone would want a computer in their home." --Ken Olson, president, chairman and founder of Digital Equipment Corp., 1977 (Digital Equipment Corp. was once the 2nd largest conmputer company in the world, but it no longer exists.) * "This 'telephone' has too many shortcomings to be seriously considered as a means of communication. The device is inherently of no value to us." --Western Union internal memo, 1876. * "The wireless music box has no imaginable commercial value. Who would pay for a message sent to nobody in particular?" --David Sarnoff's associates in response to his urgings for investment in the radio in the 1920s. * "The concept is interesting and well-formed, but in order to earn better than a 'C,' the idea must be feasible." --A Yale University management professor in response to Fred Smith's paper proposing reliable overnight delivery service. (Smith went on to found Federal Express Corp.) * "Who the heck wants to hear actors talk?" --H.M. Warner, Warner Brothers, 1927. * "I'm just glad it'll be Clark Gable who's falling on his face and not Gary Cooper." --Gary Cooper on his decision not to take the leading role in "Gone With The Wind." * "A cookie store is a bad idea. Besides, the market research reports say America likes crispy cookies, not soft and chewy cookies like you make." --Response to Debbi Fields' idea of starting Mrs. Fields' Cookies. * "We don't like their sound, and guitar music is on the way out." --Decca Recording Co. rejecting the Beatles, 1962. * "Heavier-than-air flying machines are impossible." --Lord Kelvin, president, Royal Society, 1895. * "Drill for oil? You mean drill into the ground to try and find oil? You're crazy." --Drillers who Edwin L. Drake tried to enlist to his project to drill for oil in 1859.
Reply by ●March 8, 20052005-03-08
r.lyons@_BOGUS_ieee.org (Rick Lyons) writes:> [...] > * "We don't like their sound, and guitar music is on the way out." > --Decca Recording Co. rejecting the Beatles, 1962.Ouch! That had to hurt! -- Randy Yates Sony Ericsson Mobile Communications Research Triangle Park, NC, USA randy.yates@sonyericsson.com, 919-472-1124
Reply by ●March 8, 20052005-03-08
Rick Lyons wrote:> On Mon, 07 Mar 2005 14:42:39 -0700, Kevin Neilson > <kevin_neilson@removethiscomcast.net> wrote: > > >>When I was a youngster (in the 80's) I had a book I bought from Radio >>Shack that described the concept of digital electronics. It then went >>through a calculation to show how television could never be digital >>because it would take too much bandwidth. >>-Kevin > > > Ha ha. Neat story Kevin. > > Speaking of poor predictions, check out the following. > > [-Rick-] > --------------------I'd like to add one more. John von Neuman to Jan Rajchman (once, my boss) upon being shown his 8 kiloword memory in a cabinet the size of a large refrigerator and being told that twice that in the same volume was possible: "That's wonderful Jan, but what would anybody use that much memory /for/? Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●March 8, 20052005-03-08
Rick Lyons wrote:> On Fri, 04 Mar 2005 15:30:54 -0600, Richard Owlett > <rowlett@atlascomm.net> wrote: > > > >> >>After reading Jerry's post, I started to ask a question. >>But read your post and realized I might ask a specialist. >> >>1. Any WEB available references on how to do Fourier transforms optically? >> >>1a. Can I assume the typical demo of interference effects from 2 slits >>converting incident plane wave to 2 sources is a Fourier transform of >>something? Can you tell I've not gone to school in decades ;] >> >>2. Did it depend on knowing the incoming carrier frequency? >>IE Given an "optical Fourier transformer" as a 2-port black box. >>Could you feed it an audio signal rather than RF and get out the >>appropriate transform? >> > > > Hi Richard, > > I'll bet you'll find something useful if you > Google on the combination: > > "spectrum analyzer" "bragg cell" > > See ya', > [-Rick-] >Thou art Tantalus ;{ That combo turned up T-O-O many hits. I couldn't figure out how to select elementary ones. Top hits were to specific to particular applications. Search for: "bragg cell" or "bragg cell" physics still too many hits -- "forest concealed by leaves, let alone trees" Searched wikipedia style entries and found "Acoustooptical Tunable Filter" http://scienceworld.wolfram.com/physics/AcoustoopticalTunableFilter.html That seems to be what I was thinking of that triggered my original question. Can anyone point me to web based elementary description of "bragg cell"? [ What I really need is access to a university library. But local state taxpayer supported university does not give mere taxpayers convenient access. They just spent many resources to beguile in changing their name from "Southwest Missouri State University" to something like "Missouri State" ARRRGH! ]
