Page 1 of 2 12 LastLast
Results 1 to 10 of 12

Thread: fitting beams into smaller scanner mirrors?

  1. #1
    Join Date
    Apr 2016
    Posts
    162

    Default fitting beams into smaller scanner mirrors?

    Watching the video on NUBM44 by planters it looks like the diode gives a 6mmx4mm beam.
    Pretty big but will fit on some scanners.
    But then I see up to 30W (!) blue pure diode modules, how on earth does anyone fit that much power and still end up with 6x6mm beam? The modules get larger with power, so it's unlikely just to be more cooling and overdriving of two PBS cubed beams. But with knife edging how do they end up with a beam that can still fit on a scanner mirror?
    Two lenses could be used to shrink the beam, but from what I know that would create terrible divergence.

    I want to get into building higher power projectors and I just can't get my head around how it's done.
    With blue it's not so bad, 12W with 2 diodes and PBS cube, but how can I go higher than 2W for green and around 2W for red without getting too fat beams or extremely divergent beams?

  2. #2
    Join Date
    Feb 2011
    Location
    New Hampshire
    Posts
    3,513

    Default

    There is no magic solution and you are correct about the increased divergence of a smaller or reduced diameter beam. The only reason that diode powered modules have not simply continued to increase is similar to why computer power has not simply continued to increase and increase... The maximum output for a diode in each of the primary colors is the fundamental limit with the blue diodes being the most fundamentally powerful. Just as with multiple processors, adding diodes of one color together requires optics (inter-connects) that can be optimized to limit wasted space between the added beams, but the beams will grow (the processors will require more complex algorithms to interact) and you reach a practical limit of available scanner mirrors or acceptable divergence.

    The 30 W module will have a proportionally bigger beam and larger divergence than a 10W. If there was a magic solution it would be discovered and hacked and we would talk about it.

    There is an approach, that to my knowledge, is not utilized other than as a curiosity. If your goal is to create the brightest far field projection brightness and scanning performance then use multiple, identical projectors. Building a projector involves some costs that are not simply additive. You could probably build 10 projectors for 3-5 times the cost of a single projector. Carefully aligning each to cover the same pattern will increase the brightness at close to the multiple of the projectors used. A more ambitions and higher performance solution would use a separate controller for each projector(Pangolin will love you). A projection can then be sub divided into separate regions with each region enjoying the average output of a single projector and the scanner throw being much smaller will produce a more flicker-free image and allow a larger mirror set and this will produce a lower divergence beam as well.

  3. #3
    Join Date
    Apr 2016
    Posts
    162

    Default

    Thank you, planters. I stack video projectors regularly but with lasers I usually use them for beams not graphics and beams from different scanners can't be aligned.

    I'm not saying there's a magical solution which isn't discussed, but I feel like there are some techniques not talked about enough or scattered in the forums and hard to search and find unless you have personally engaged in the discussion and know where and what to look for.

    One thing I can't find enough info on is usage of telescopic lenses, where to source them (on eBay?), how much can they shrink the beam and how much scaling the beam down changes the divergence.

  4. #4
    Join Date
    Feb 2011
    Location
    New Hampshire
    Posts
    3,513

    Default

    There are no such techniques. I don't mean to be blunt, just clear. The biggest area available for improvement is quality. Good, well coated optics, including high performance wave plates (under appreciated) and careful alignment are important. Keeping everything clean is also under appreciated because some beams will pass as many as 10 optical surfaces. Even a very small amount of dirt on each will increase scatter and light loss.

    The free lunch that I talk about is implied by your telescope question. If you double the beam size you cut the divergence in half. The result is proportional and linear. An under-discussed area for improvement is again related to quality. The lenses in the telescope can be oriented front to back vs back to front to remove or to counter spherical aberration present in the original laser beam. This is a small improvement, but available for free. You won't notice this improvement until you have the other quality issues nailed down.

    If you want real power and performance then you need to move beyond simple diodes. OPSL lasers offer this solution at considerable cost. Green fiber laser with hundreds of watts are available at incredible cost. There is one gentleman in Britain that is using high power Q switched YAGs to drive dye lasers intend for commercial applications and I am working on the same thing for fun. All of these sources break the fixed limits of the multiple diode beam size vs divergence limitations. but your talking big and expensive.

  5. #5
    Join Date
    Apr 2016
    Posts
    162

    Default

    Quote Originally Posted by planters View Post
    If you double the beam size you cut the divergence in half. The result is proportional and linear.
    Thanks for this info.

    Any ideas where to get telescopic lens?

    PS. Yes, dye lasers and OPSL are not an option for me.

  6. #6
    Join Date
    Feb 2011
    Location
    New Hampshire
    Posts
    3,513

    Default

    Edmund optics
    Thorlabs (less expensive and you get a snack)

    http://www.edmundoptics.com/

    https://www.thorlabs.com/

  7. #7
    Join Date
    Apr 2016
    Posts
    162

    Default

    Both are very professional companies but both are kind of expensive, compared to other laser optics sold on eBay or some sites (Stanwax, Lasershowparts).

    Which types of lens would you recommend for this?

  8. #8
    Join Date
    Jun 2010
    Location
    Youngstown OH temporary
    Posts
    135

    Default

    http://www.surplusshed.com/ has less expensive lenses.
    http://www.nasa.gov/audience/foreduc...Telescope.html explains calculating the focal lengths for the magnification you want.

  9. #9
    Join Date
    Apr 2016
    Posts
    162

    Default

    Surplusshed has great prices but I've read the efficiency if their FS mirrors and optics is not great, somewhere in the 80% range. Meanwhile some eBay sellers (eg. gkphotonics) has reasonably priced mirrors with >90% efficient AR coating. I hope to find something in that range for lenses but closer to eBay numbers than Thorlabs in price.

    Hm, how about using two pairs of cylindrical lenses to shrink the beam? One for the horizontal plane, and then another pair for the vertical? This adds losses but those lenses are easily sourceable.

  10. #10
    Join Date
    Oct 2012
    Location
    Germany
    Posts
    1,385

    Default

    ... I've salvaged some single-element beam-expanders from old NdYAG marking lasers, which I've got for free for scrapping them.

    And some years ago I've got 3 Rodenstock beam-expander telescopes for together 90, what even then seems to be a pretty good deal - an actual search at ebay found them from 200 to 900 USD! ... or 150 to 500 here in Germany.

    So look around, if you can find some old/outsourced gear or low cost offers at ebay ...

    Viktor

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •