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09252007, 06:53 PM  #17  
 
Class 3B Laser Join Date: Jul 2007 Location: Berkshire UK
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Thanks Pseudo, that makes things much clearer Regards rog8811
__________________ See all of my videos on Vimeo http://www.vimeo.com/4454150 Lots of tutorials and information on lasers http://www.rog8811.com/ In the land of the blind the one eyed man..... is most likely holding the laser  
09252007, 07:46 PM  #18  
 
Class 3R Laser Join Date: Jun 2007
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Meshtel.com 50$ beam expander/collimator
 
09262007, 01:31 PM  #19  
 
Class 2 Laser 
For U math wizzards here's the formulas for Expanders/collimators ;D http://www.edmundoptics.com/techSupp...?articleid=270 ENERGY>)]<[)====TARGET(OUCH) :'( Use the shorter Gallian type to burn something good at any distance because its adjustable. [smiley=2vrolijk_08.gif] [smiley=beer.gif]  
09262007, 02:01 PM  #20  
 
Junior Member Join Date: Sep 2007
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Since this topic is explaining basically what I would like to know, i'm going to ask in here... I'm looking at expanding a beam as well, but from a basic laser pointer size beam (a Aixiz 650nm 10mw 12mm X 30mm case with a DVD burner diode) up to 4050mm in diam. if that is possible. Is there expanders that would expand that much or is there some other way of doing it?  
09262007, 03:36 PM  #21  
 
Class 3R Laser Join Date: Oct 2006
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09262007, 08:59 PM  #22  
 
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Thanks for the reply I was looking at this (I can't posts links  But it's a 50mm diam/35mm FL aspheric lens) to converge the beam after it had been spread, I just couldn't find anything that seemed suitable to diverge it though. The diverging lens needs to be able to spread the beam from it's original diam. to 4050mm within the 35mm focal distance of the 2nd lens. The beam doesn't need to be PERFECT, it's just a little project where i'd like to make up a Maglite housing and have a wide straight beam out of it.  
09272007, 02:03 AM  #23  
 
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I have been using the formula above in the picture to estimate the lens I require... Since I can estimate the input beam diam, output beam diam, and the secondary lens I can rearrange the formula to work out the FL primary lens I need. Since the output is d and the input is (f2 / f1) * d, I can call the input "y"... So I need to know f2. y = (f2 / f1) * d y / d = f2 / f1 (y / d) * f1 = f2 f2 = (2mm / 40mm) * 35mm f2 = 0.05 * 35 f2 = 1.75mm That seems like an unrealistic focal length for an aspherical or concave lens like in the above diagrams... Or is it possible?  
09272007, 02:36 AM  #24  
 
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That is a pretty small focal length. I found some that are 3.3 mm here thorlabs.com/NewGroupPage9.cfm?ObjectGroup_ID=16 although that would only give you a 21 mm beam. 1.75 mm might be something that is possible with a microscope lens or something. Unfortunately with a 35 mm that is what is needed to get your desired magnification. There is a 3 lens system that uses a converging followed by a diverging followed by another converging lens that would allow you to create an arbitrary magnification within the size limitation of the lenses, but it would require more space. If you would like I can draw a picture of it and maybe that senkat guy can make it into a link you can click on.  
09272007, 02:45 AM  #25  
 
Class 3R Laser Join Date: Jun 2007
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Save yourself some headaches by using this applet http://www.lightmachinery.com/gausbeam.php If you are unsure how to use it I will help you through it stone Quote:
 
09272007, 07:58 AM  #26  
 
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Thanks for the replies... It looks like I might have to resort to making my project a bit longer to keep the cost and availability of the lens easier to work with. If we disregard my length limitations, is there any common and cheap lenses that would work for me? The only store i've looked at is Surplus Shed as their lenses seem quite cheap. If I was to use the common 6mm FL lens mentioned, i'd need a 120mm FL secondary lens, that's 126mm between 2 aspheric or 114mm between a concave and aspheric. My secondary lens MUST be 5052mm in diam. Steve... I don't understand that beam program, just due to not knowing the terms "separation length" and "Rayleigh range", but I can do a search [edit] I've been Googling lens suppliers and i've found many small 23mm FL lenses from various suppliers but the prices seem rather expensive. As this is just project has no real use other than me wanting to make a wide beam, I don't really want to spend a fortune on it.  
09272007, 07:35 PM  #27  
 
Class 3R Laser Join Date: Jun 2007
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and 3 for the one below. these numbers are based upon a laser I have. This is the approximate beam diameter and beam divergence as it exits the crystal. Focal lengths of the lenses can be any length. First lens separation can any length. for this run through use 1mm First lens focal length 6mm Second lens focal length 20 mm Second lens separation start with 20 mm Decrease the distance of the 20mmEFL lens in 1 mm increments then in smaller increments Repeat this procedure again, but this time change the 20EFL mm to 48mm. Start the second lens at 48 mm distance. Then start to decrease the distance 1 mm at a time then in smaller increments. Watch how the Rayleigh range increases dramatically. There will be a point where the beam is optimally collimated as indicated by the graphic display. Now for the 3rd exercise add a second 6mm EFL lens with a separation of 9mm from the first Change the positive lens too 126mm EFL repeat the same step as before until you if you position the lens 121. 725 mm from the second negative lens you'll get a Rayleigh Range of 254451.824mm or 834.815696 feet To know the beam expansion power divide the positive lens by the negative lens. Beam Diameter at Surface means, beam diameter is at the positive lens Rayleigh range is the distance over which the beam expandes the square root of 2 or 1.41 times it's initial diameter. Beyond that point the beam will expand linearly with distance.  
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