| Author | Message | ||
     lysdexia Unregistered guest |
Look at the Wikipedia article for the Fresnel zone plate. This is a remarkable flat-panel diffractive magnifier. Months ago I decided to calculate some fringe radii because I thought about using a computer drawing program to make the pattern[s] to be printed on a transparency and be used as a solar weapon. But I'm not sure how well-equipped I need to be to pull this off. Can someone finish this list and try making one? r = (nlf)^.5 f = 125 m; l = 555 nm => r[1,...]mm = 8.33, 11.8, 14.45, 16.65, 18.6, 20.4, 22.05, 23.55, 25.0, 26.35, 27.6, 28.85, 30.05, 31.15, 32.25, 33.3, 34.35, 35.35, 36.3, 37.25, 38.15, 39.05, 39.95, 40.8, 41.65, 42.45, 43.3, 44.05, 44.85, 45.6, 46.35, 47.1, 47.85, 48.55, 49.3, 49.95, 50.65, 51.35, 52.0, 52.7, 53.35, 54.0, 54.6, 55.25, 55.85, 56.5, 57.1, 57.7, 58.3, 58.9 (50), 59.5, 60.05, 60.65, 61.2, 61.75, 62.35, 62.9, 63.45, 64.0, 64.5, 65.05, 65.6, 66.1, 66.65, 67.15, 67.65, 68.2, 68.7, 69.2, 69.7, 70.2, 70.7, 71.15, 71.65, 72.15, 72.6, 73.1, 73.55, 74.05, 74.5, 74.95, 75.9, 76.35, 76.8, 77.25, 77.7, 78.15, 78.6, 79.0, 79.45, 79.9, 80.3, 80.75, 81.2, 81.6, 82.05, 82.45, 82.85, 83.3 (100), 83.7, 84.1, 84.55, 84.95, 85.35, 85.75, 86.15, 86.55, 86.95, 87.35, 87.75, 88.15, 88.55, 89.3, 89.7, 90.1, 90.5, 90.85, 91.25, 91.6, 92.0, 92.35, 92.75, 93.1, 93.5, 93.85, 94.25, 94.6, 94.95, 95.35, 95.7, 96.05, 96.4, 96.8, 97.15, 97.5, 97.85, 98.2, 98.55, 98.9, 99.25, 99.6, 99.95, 100.3, 100.65, 101.0, 101.35, 101.65, 102.0 (150), 102.35, 102.7, 103.05, 103.35, 103.7, 104.0, | ||
| Simon Quellen Field (sfield) New member Username: sfield Post Number: 96 Registered: 12-2004 |
Actually, I am working on a project that is using a fresnel zone plate to take photographs and make camera obscuras. There are some great web sites with photographs taken with such plates. They can also be used to focus xrays or radio waves, or even sound waves. A sound wave "lens" made this way would be fun, and should be possible using cardboard and wire screening. You could set up a pair of them at opposite ends of a play ground to make a "whispering gallery" effect. Why did you enter a big list of numbers instead of just the formula, or a short piece of computer code? See this site for the easy way to make zone plates. | ||
| lysdexia Unregistered guest |
I did put the formula in. The site doesn't meet my needs! Its extra large file isn't half the size needed for my plate. And I said that this wasn't for some puny camera, but was for a solar weapon. I couldn't even get the file to download with my specifications. So I need someone to manually complete the list until the differences approach the dot size of the better printers or software, and then manually draw the rings, or at least write a script to enter such values (by formula, sure, but to the right size—about a foot in width) into a drawing. | ||
| lysdexia Unregistered guest |
What's the equation for acoustic loss/drag/damping through a medium? | ||
| lysdexia Unregistered guest |
Do you know how sound waves can be refracted into a focus without much reflecting off a refracting lens in question? | ||
| Simon Quellen Field (sfield) New member Username: sfield Post Number: 98 Registered: 12-2004 |
If you have the formula, just plot it into a speadsheet program like Excel and tell it to plot the result. A fresnel zone plate will only focus half the light that a parabolic mirror will. This is why you see more telescopes and solar concentrators made from parabolic mirrors than from zone plates. And don't shout about free web sites not meeting your needs. If you offer payment, I am certain the author of the site will help you. Just like in physics, you can't get something for nothing. The acoustic equation you are looking for is not likely to be found on a site about toys. There are better places to look, such as message boards about acoustics, or a library. The last question is fairly easy. Reflections are caused by impedance mismatches. For example, a swimmer underwater can't hear you talking because your sound waves bounce off the surface of the water, due to the impedance mismatch between water and air. If you put plastic cling wrap around the small end of a (non-electric) simple megaphone, and speak into the large end while the small end is in the water, the cone will match the impedance, and he can hear you. Edison did this to match the impedance of the air to the impedance of a needle in wax for the phonograph. If you fill a balloon with argon or carbon dioxide and talk at it, it will act as a lens to the person with her ear in the right place. The impedances are not as mismatched as with water. However, you could use cones to match the impedances better anyway. But why not use reflections to do the work instead of fighting them? Just use a parabolic surface. The wavelength of sound at 3,000 hz is about 4 inches, so the surface only has to be parabolic to within a half inch or so to be a 1/10th wave mirror. | ||
| lysdexia Unregistered guest |
If I knew how to do that [with Appleworks only], I wouldn't be asking here. That's not a very good reason, as a zone plate can be made extremely thin, flat, and light... and thus to great sizes. I never mentioned nothing; nothing doesn't exist so it's pointless to talk about it or use it in a premise. Though there are "nothings of convenience", or false nothings, such as the "0 = -n + n" trick I used in my treatise which authorities like you or academics can't deal with. 0 is a limited nothing which is why this operation is defined. Logic and mathematics are above science. If you had bothered to read my work, you wouldn't still be making these silly claims against alternative energy. Besides, my idea of a solar weapon is worth something. You keep mentioning Excel when I know nothing about it, not having it. What are the limits of its plotting? Why do you keep referring to a spreadsheeter when there are calculators around? If you know what I should type to get a polar inequality with such a formula in Graphing Calculator, that'd be much more helpful than pointing me to something I have no access to. I posted and goaded here to share the idea, and if so many people could do that in Excel and are interested in it (why wouldn't they be?), I'm not hearing them. Custom standard reflectors take up more space and weight, and in many cases call for another element to let light in any direction. They also must be shaped precisely on thick media which is very expensive, and are not adjustable or versatile. Sure, I can limit them to a thin rectangle or plate and one transverse or radial axis with a slit, but that isn't as elegant as a sheet I don't need to bend and can make with pennies for precision. A zone plate can be made with an arbitrary proportion of reflective and transparent media and an electric display can be adapted to generate any beam path and shape. (Shoot, did I just blow a patent? I guess it was coming. Nonetheless I did try to novelly explain the Philadelphia Experiment on Wikipedia before they took my contribution off.) That is how diffraction is superior to reflection. Though with the focus I have in mind maybe I need the print on a flat reflector, just to simplify, if that'll work. My question asked for both a large refractance and large transmittance. Looking at the Fresnel reflection equations on Wolfram Research I still wonder if there's a passive system that can achieve this. | ||
| Anonymous |
You can easily find spreadsheet programs like Excel that are free. But someone with your mighty intellect is surely rich by now. At a thousand watts per square meter, you will need a lot of square meters before your weapon has the power of the weapons currently in use. And such a large device will make an easy target, and a difficult one to transport and support and aim. Publishing an idea doesn't harm the patentability of it. But I can't understand why you aren't talking to the people who set up the zone plate site instead of whining here. |
