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Thread: Any optics experts out there?

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    Default Any optics experts out there?

    I'm working on a simple beam expander for some Taipan lasers. One negative lens and one positive lens with a mechanism to adjust the distance between them. Commercial units all seem to use achromatic lenses. Is there any advantage to using an achromat over a simple (i.e. cheap) spherical lens when working with a single wavelength?

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    ... AFAIK achromatic lenses have better "Depth of Field" with wider beams than spheric ones ...

    Viktor
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    I'm not sure what that means for a collimated beam. I'd guess an aspheric lens would perform better than spherical, but achromatic seems unnecessary for an monochromatic light source.

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    If your running single wavelengths through each telescope your looking for "Aspheric" or " Best Form" lenses to go long distances. Otherwise normal spherical is fine. If you can find an old, old, Melles G catalog the pages on Collimator /Telescope design are worth reading. As achromats are well matched in order to be cemented together, they generally have a better optical form then much cheaper lenses. Beware of putting a laser focal point in the center of the achromat's cement.

    If due to budget reasons, only one lens is "Best Form, or Aspheric" make it the one closest to the cavity.

    Hope all is well, give a ring if you have further questions.

    Steve
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    Quote Originally Posted by mixedgas View Post
    As achromats are well matched in order to be cemented together, they generally have a better optical form than much cheaper lenses.
    That's what I was thinking... It's not that an achromatic lens offers any benefit over a standard aspheric lens when the beam is monochromatic, it's just that as a general rule achromatic lenses tend to be manufactured to higher tolerances than the cheaper, non achromatic aspheric lenses.

    Assuming you sourced a high-quality standard aspheric lens it should perform just as well as an achromatic lens. But I think you're more likely to find superior lenses if you stick with the achromats.

    Adam

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    Pretty much what I figured. I've been using lenses from Thorlabs which seem pretty nice for the price. Maybe I'll get one (expensive) asphere to experiment with.

    Quote Originally Posted by buffo View Post
    That's what I was thinking... It's not that an achromatic lens offers any benefit over a standard aspheric lens when the beam is monochromatic, it's just that as a general rule achromatic lenses tend to be manufactured to higher tolerances than the cheaper, non achromatic aspheric lenses.

    Assuming you sourced a high-quality standard aspheric lens it should perform just as well as an achromatic lens. But I think you're more likely to find superior lenses if you stick with the achromats.

    Adam

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    For lasers the cheap stuff is fine for a single wavelength. Well so long as it handles the power level and has basic quality like most optics today.

    A glued doublet might actually be an issue.

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    "There are painters who transform the sun into a yellow spot, but there are others who, with the help of their art and their intelligence, transform a yellow spot into the sun." Pablo Picasso

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    It's my understanding that achromats are better to use than singlets for monochromatic light because they are also corrected for spherical aberration, allowing much more of the lens to be used.

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    ... yes, this was my intention with "better 'Depth of Field' with wider beams"

    Viktor
    Aufruf zum Projekt "Müll-freie Meere" - https://reprap.org/forum/list.php?426
    Call for the project "garbage-free seas" - https://reprap.org/forum/list.php?425

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