Fresnel lens with collimating lens set-up

Hi. Boatingman here. When I joined Instrucables several years ago, there was a post showing a fresnel lens salvaged from an old TV, then set up with the mirror from the same TV, and then set up with a set of collimating lenses. Now, of course, this didn't make an actual laser, but it did extend the useful range of the focal point and, thanks to the mounting system shown, could actually be aimed. I can't locate this "Instructable", so if anyone out there does have it (or if you have done something similar), could you please let me know. Thank you.    Ed

Topic by boatingman   |  last reply


where can i get a focusing lens for my 1000mW burning laser?

I just bought this laser diode http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item;=270664621237 but when i first used it, with me not knowing that it didnt come with a lense to allow it to burn things from a distance less that 1 mm. i was unable to use it properly, due to it not having a focusing lens, instead nwhat i get is a spray of light in a large rectangle sort of shape. so now im stuck with the dilema, where can i get a focusing lens for it so it makes a dot like any normal laser, WITHOUT  using the laser flashlight hack, as i dont want to spend that much money, i just want to buy a lens, or ripp one form a dvd player , and thats it done, i can use the laser to light viscus fuse from at least 20m please help me, and whoever gives me a best answer without mentioning a thing about lasers being dangerous and stuff like that, i promise will get a best answer. also i will flagg any answers that are intentionally not answering my questions and say, as i statyed above, "this is dangerous, you could poke your eye out with viscus fuse" . and " lasers are dangerous dont use them". or other pointless warnings i have already read on line. i have bought infrared laser safety goggles that came with my laser diode that are strong enough to withstand being directly shon at in the eyes with the 1 wat laser and not see a thing, or so ive heard, im not taking that chance. just to be clear i know what kind of lens i need, i just dont know WHAT lens i need

Question by oldmanbeefjerky   |  last reply


High Power LED Collimating optics for projector project.? Answered

Greetings; My projector currently has a high pressure fancy schmancy bulb and when it goes (after another few thousand hours hopefully) I want to replace it with a high power (~100 watt) LED.  That's the easy part.  I can interface with the projector and convince it there is a real bulb firing up - but I need the optics.  Basically, it's a DLP projector so all the light has to be focussed on just under a 2x2cm square hole to hit the colour wheel.  The LED in question is already over that size on the diode die alone.  There are parabolic reflectors available (I think my best option) but they still have a positive beam spread - I need a shrinking beam.  It doesn't have to be perfectly collimated, but I bet that helps.  The original lamp definitely has a converging beam but its hard to measure as you can't operate the lamp with the cover open (safely). SO I'm thinking diode >> reflector (like flashlight) >> convex or fresnel lens. I can't get better measurements at the moment for I'm not near the machine and its finnicky to take off the ceiling.  Penny for your engineering thoughts? What I need but have never seen commercially:  http://en.wikipedia.org/wiki/File:CollimatingLensSVG.svg LED to use: http://www.dealextreme.com/p/prime-100w-7000lm-led-emitter-metal-plate-warm-white-42807 dimensions about 5x5.5cm Reflector I have in mind: http://www.dealextreme.com/p/20-100w-silver-plated-plastic-smooth-reflector-58mm-39963 (rather wide beam still) Alternate reflector: http://www.dealextreme.com/p/20-100w-silver-plated-plastic-smooth-reflector-50mm-39974 So...what I need are lens options.  Based on my estimations I'll have several cm (up to 10cm) to come up with a good focus distance.

Question by frollard   |  last reply


What's the best broadband collimated light source?

I am measuring the transmittance of different glass samples using integrated sphere and a radio spectrometer.... the light source that I am using currently is a Halogen car head light... but it is neither collimated nor bright enough.....  Could you please suggest what light source shell I be using... Moreover could you please have a look at the pic attached and suggest any improvements in my method of transmittance measurement.. I'll be very thankful to you for any assistance in this regard. Kind Regards

Question by raishikoh   |  last reply


I accidentally invented a device to collimate any light source into a concentrated beam... what should I do with it?

I've been umming and ahhing about what to do with this for the couple of weeks since I accidentally invented the thing (I was working on a solar energy device), and I thought you guys may be your usual well-spring of help and advice. Basically I seem to have designed a device which will collimate an extended light source. Any light source. So you could, for example, turn a 100 Watt light bulb into a 100 Watt laser. Or a square meter of sunlight into a kiloWatt. I haven't made it, but simming on the computer gives an optimal blow out rate of about 1/2 meters per kilometer, so over a range of meters or tens of meters it's pretty much as accurate as a normal laser. The only upper limit I can see on how much power you could put through this thing is when the materials start melting, which would probably be pretty high. There's really nothing fancy about it, it's just a shape. You could print it out easily on a 3d printer and fill it with some kind of settable glass for the total-internal-reflection. It would weigh about as much as a 2 litre bottle of water and be about the same size. I was concerned about it being weaponisable, but even at a kiloWatt the lethal range would probably be less than 100 meters, in which case you might as well just get a gun. I don't know if anyone's already done something like this, I can't find anything online, and people kept telling me it was supposed to be impossible. So, um, yeah...

Topic by SolarFlower_org   |  last reply


What is the optimum solar cell sample size that I should select while testing it with PASAN SunSim 3B Sun Simulator?

I have to suggest sample sizes in order to generate some I-V curves using PASAN SunSim 3B Sun Simulator. The issues with the size and other things was about difference in distance to the light source, and the fact that the light source is not collimated and we can't collimate it, so we need to workout the tolerance. The distance between the external lamp and the sample is about 7 meters. External Lamp consists of 4 lamps connected to a single square shaped holder. The dimensions specs of the external lamp as given in the attached images. What if the sample size is smaller than the light source? What is the optimum solar cell sample size that I need to select? What parameters will be effects if the sample size is not optimized? "Please Keep In Mind That The Sample Size Should Be As Small As Possible". The attached images with help you in getting an idea, how the sun simulator looks like and what are the dimensions of external lamp

Question by raishikoh 


What fun project can I do with around 300 Liconix high powered laser lenses Collimator ,optic lenses, Optic Filter..etc

Old Neighbor of mine was a Senior Laser Technician for Liconix about 10-15 years ago probably still works there. Anyhow he always would always be working on lasers Argon, Helium, Krypton, and his classic cars and overtime his family became sort of family to me. I would watch in awe as he worked trying to learn as much as possible. So I would help him work on his cars or Fix a PC for him here and there or take care of his son. I was only 13 at the time, but he was nice enough to give me a couple lasers for helping that his work was going to discard, some helium, Argon. I had to give the Argon back though because he sold his house and was moving to a better neighborhood. Plus it kept blowing the fuses in my parents'house from the power load. PGE was getting angry cause for some reason the street light sensors in my neighborhood were somehow getting burned out all the time *shrug* I don't know how and had to keep repairing them. Before he left he gave me some extra tubes for when my others eventually died. Most helium and tons of lenses of various sizes which are all tucked away in a box. In my dad's Garage of Death yeah he's a pack rat. But I found a couple of the lenses when I came to visit that I had sitting around the house and thought to myself time to dig the box out, so I'm slowly digging my way to it. Just don't know what fun project to do with all of it other than making a Laser Beam of doom or putting them on Sharks with fricken laser beams attached to their heads I also have a Fresnel lens from a 45 inch rear projection TV. Any Idea what fun project I should make with all of it ? I bet it would make one hell of a laser pointer for my Celestron GPS-GOTO C11 Telescope haha.Thanks for any idea's.

Question by Laser_PewPew   |  last reply


Laser Tag Hacking

I've been toying with this idea for a while, but I can't go anywhere with it until I get some programming experience (I'm taking a class on it next year, so I'll be able to do it then). I was thinking of this as a potential way to cheat at laser tag (or make it more interesting at least). get a microcontroller, a photoresistor, and plenty of cheap laser diodes with collimators, lenses, etc (a bunch of cheap laser pointers would work for this). use the photoresistor to have the microcontroller "learn" your laser's signal (so that you can get credit for your tagging), and then reproduces that signal at the press of a button. put all the lasers facing outward in a ball and presto, a laser tag grenade. just wondered if anyone could think of a good way to do this.

Topic by codongolev   |  last reply


How do I construct a maser?

So I have mentioned before about my plans to build a HERF gun using a magnetron powered by a highspeed motor w/ permanent magnets that serves as a generator(it's driven by a minature gas turbine engine). But the issue of collimating the microwaves into a beam that can travel at least 4 miles without significant diffraction is an issue I'm still working on. Now magnetrons have an efficient of roughly 70%.  So here's the idea: The magnetron's output coupling loop(antenna) will be inserted into a highly tempered glass cylinder that is attached to the top of the magnetron and the cylinder will be filled with either hydrogen gas or (anhydrous)ammonia. The oscillating RF field will pump the gas molecules at their microwave region resonant frequencies(if I use ammonia that will mean I need the magnetron to produce peak power at 24 GHz)and stimulate microwave emission by the molecules(population inversion). Has this technique ever been demonstrated experimentally? I know that RF radiation can be used to heat up hydrogen gas into plasma but maybe there are some references to masers constructed in this fashion.

Question by YugZ0h0th   |  last reply


What is the axial orientation of Polaris with respect to the Earth? Answered

So... I know the Earth's axis of rotation currently points (roughly) at Polaris, the North Star. (which, of course, is why we can navigate by it here on Terra Firma).  I also know that Polaris is about ~500 ly from us,  has a rotational period (hence an axis), that it's a transitional Cepheid (sp) (a star that varies between a larger, brighter state and a smaller, denser one) , that it has at least two l known, low-output companion stars, and that since the ~1940s it has undergone visible changes in its rotational period and its output. My excuse and reason  for asking... First, I did google it. Either no one has asked the question(doubtful), it can't really be determined with our present level of science (could be, idk), or I just didn't use the right search  terms to find the answer (the usual culprit ime) , but in any case, after an off and on search that's spanned the past ~year, I think it's time I ask. Secondly, the inspiration. I enjoy amateur astronomy.  However, time and equipment and location often limit my grand delusions for the next "Citizen challenges Hubble with stunning new photo of Zeta p3044-a!" award hahahaha.  But the real problem is most often because of my mid-level scope's somewhat limited ability (in comparison to a German equatorial mount) to track consistently and smoothly, and as a result, Polaris becomes an easy target when I get frustrated with the scopes performance on a given night (sometimes it does track brilliantly... for a stepper-driven alt-z, but only sometimes and even then only to the limits of the steps) because the only thing the scope has to track when pointed at the North Star is rotation, which it seems to handle better than both directions of movement (probably needs a new gear or the motor is wearing or my expectations are simply higher than that of my equipment ...). Of course, I also quite often choose to shoot Polaris when conditions are such that it's the only viable target (for instance, when I'm stuck imaging from my backyard, I have a postage stamp size hole that happens to point at Polaris... which of course basically "doesn't move", pretty much everything else is shrouded by century old, 8-100 ft tall forest during the warmer months, and when I can't drive out to a more suitable location, it's a lucky night when everything is "right", I can even align the mount (it uses a goto controller that requires a 3 star alignment for tracking with any accuracy). So Polaris is a no-brainer, (take some images for arts sake, fine tune the in-situ collimation, data-reduction test sets, etc.) . Either that or do something else...  Anyway, as a result of all of this, I'm found myself enjoying the simplicity of shooting the North Star and the area around it, and having fun with image processing and even optical train modifications to further the artistic side. And I've read a few articles about it's variability and the ~relatively significant changes in its behavior that have been occurring during the past 50 years that got me to thinking What I'm wondering is that when I image Polaris, am I looking at it "on its side?", "on axis?", or at some other viewing angle? Not that I'm going to be able to literally "view it on its side" or something, since optically imaging the star beyond that roughly of a point-source isn't practical, but just to know, since the darned question won't get out of my head. (been asking it for the past year quietly to myself and google. I hate to think how many cumulative hours I've spent at it...) thanks!

Question by seandogue   |  last reply


Observing single photons (may be future Instructable)

In a thread on building a DIY Geiger counter, I mentioned that it's possible to do an experiment to see single photons directly with your eyes. This is a lab we did when I was an undergraduate, more than 20 years ago. I haven't done the setup myself since then, so I'm just going to describe it; if I have the opportunity run it again, then I'll make an I'ble.If someone else decides to tackle it, please feel free to write it up yourself!The human eye detects light via a family of proteins called opsins. Different forms of photopsins are sensitive to different wavebands, which is what gives us color vision. Rhodopsin is sensitive mainly to greenish-blue light, and provides us with monochromatic night vision. Rhodopsin works by changing its conformation when it absorbs a photon; that change of conformation allows ions to flow through the rod cell's membrane and generate a signal. The signal from each rod cell is processed through the retina and passed to the visual cortex, where a representation of the visual field is constructed.Human rhodopsin has a quantum efficiency of about 25% (there's a 25% chance a single photon will be absorbed and produce the rod-cell signal). By comparison, cat rhodopsin is more than 90% quantum efficient. 25% QE is sufficiently high to be observable -- a source of single photons can be seen by a dark-adpated person with normal vision.You'll need a steady source of well-collimated photons. A green laser pointer (~532 nm) will do nicely. But how many photons does it generate? A wavelength of 532 nm corresponds to 3.53×10-19 joules. So a small 1mW laser pointer puts out 2.8×1015 photons per second (watt = joule/s). How do you reduce that to one photon at a time? With filters. An ND3 neutral density filter reduces the output light by 10-3 compared to the input, so a stack of just five ND3's in front of this laster pointer would result in (on average) just 2.8 photons per second! A stack of four ND4's would give you 0.28 photons/s on average.If you don't have neutral density filters, you can make a decent approximation, by stacking sheets of black trash-bag plastic. To make this work you have to measure the attenuation yourself, so you'll need a photodetector, something which gives an output (voltage, resistance, current, whatever) proportional to the intensity of light.Once you have your single-photon source, you need to set it up in a completely dark room. If you have access to an old-style photographic darkroom, use it. Otherwise, use thick (3-5 mm) black felt and gaffer's tape to seal any windows and doorframes. Put the laser on a table or stand pointed at your face, with the stack of NDs (or trash bags) in front of it. If you're doing this by yourself, you may want to have a piece of tape set up to hold the pointer's button down. Otherwise, your lab partner will take care of it.Sit in the dark for 20 to 30 minutes. This will seem like forever, so you may want something to help you keep track of the time. A standard CD will be about half finished, or you can get through ten pop sons on your iPod, when your eyes become dark adapted.Turn on the laser. You'll see intermittent flashes all coming from nearly the same place in your visual field; if you turn your head, the location will move in the opposite direction. If you've used filters to get down to a few flashes per second, POV will make them easier to see. At less than one photon per second, you'll see them individually.

Topic by kelseymh   |  last reply