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Thread: My Laser is Broken!!! Not really, I do have an optics question regarding lens quality

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    Default My Laser is Broken!!! Not really, I do have an optics question regarding lens quality

    Do any of you fine gentlemen know whether higher quality 1/4 or better lambda lenses are a must for a high quality collimated beam, or whether 2 Lambda is perfectly acceptable?

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    mixedgas is online now Creaky Old Award Winning Bastard Technologist
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    Quote Originally Posted by Laser57 View Post
    Do any of you fine gentlemen know whether higher quality 1/4 or better lambda lenses are a must for a high quality collimated beam, or whether 2 Lambda is perfectly acceptable?
    !

    For laser show use, L/2 would not be noticed for throws under say 300 feet. . However if a lens company can not achieve L/4 or better on a cheap product, I'd be worried and wondering why. I typically get L/20 or better these days on anything but the cheapest lenses. ( Is your L/2 optic a cheap plastic lens?????)
    !
    Make sure its AR coated. 8% total Fresnel loss on a uncoated optic starts to add up fast.

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    Thank you for answering!

    I have been collecting lenses for two years, bought a huge lot of them from a guy last year, so I have all kinds of lenses, but I don't have any good aspheric lenses over 1 inch diameter yet. I've been considering larger diameter aspherics because I'm under the impression, perhaps wrongly, that I can get a better low divergence beam out of my laser pointer with less spherical distortion if using a large aspheric. Not that I have a real need for a perfect beam, I want to get mine as close to perfect as I can. I found some 25mm Edmund Optics 4/L 60-40 aspheric lenses on ebay new in the box I just bought for 20 dollars each, a couple of them, their price new on Edmunds is crazy, 225 dollars each in small quantities. http://www.edmundoptics.com/optics/o...-lenses/47730/

    http://www.ebay.com/itm/NEW-IN-BOX-E...-/400276180837

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    For my laser pointers I like to use 2 to 3 inch and larger collimation lenses so I get a nice fat low divergence beam out of them when using a multimode diode, but all of the largest PCX lenses I use for them are photographic condenser lenses. I have no idea how accurate their surfaces are, but they seem to make nice beams. If you happen to know what the common Lambda accuracy is for those kinds of lenses, or in general, most photographic lenses, I'm all ears because I've been searching for that information.

    Click image for larger version. 

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    To see some of my large lens laser pointers,
    wait for this gif to cycle through to them.
    Click on the photo to see higher resolution.

    I might use these 25mm EO lenses with some single mode lower power laser diodes, they don't need huge lenses, 25mm/1 inch ought to make a very low divergence beam for them. You might wonder why I want low divergence? I am fascinated by the idea of my laser pointers being able to go miles and miles without expanding very much.... well, if I can keep the beam down to 10 feet wide for a few miles I'm happy, the smaller the better

    Unfortunately, the EO 25mm aspheric lenses I bought are not coated. I never heard of Fresnel loss before, but I was aware of the loss due to reflection alone.
    Last edited by Laser57; 07-08-2016 at 10:26.

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