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Thread: Beam expander after scanners.. possible?

  1. #11
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    Actually, you can have a fat, parallel beam, being focused just before the scanners to match mirrors size, and then after scanners, you use a big diameter lens to re-expand the beam and make it parallel again.

    Pretty sure I already seen that on LOBO projectors and other ones...

  2. #12
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    Quote Originally Posted by sbk View Post
    Actually, you can have a fat, parallel beam, being focused just before the scanners to match mirrors size, and then after scanners, you use a big diameter lens to re-expand the beam and make it parallel again. Pretty sure I already seen that on LOBO projectors and other ones...
    Wow, great info. This sounds like a much more feasible solution. I suppose it's either this, or just buy a 10mm aperture Scannermax set.

  3. #13
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    The focal plane in this case is limited by the size of the mirrors. The objective lens doesn't care if the beam hits in in the center or the edge - if it comes from the center of the focal plane it's going to be projected perpendicular to the focal plane. It may work after a fashion if you need a truely tiny angle...
    "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

  4. #14
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    For what its worth, back in the day we would actually often correct after the scanheads. The bounce mirrors and dichros would sometimes introduce astigmatism/divergence so we kept a bag of these 3" to 5" diameter lens in the -6 to +6 diopter range in 0.05 diopter increments near zero and .25 diooter increments toward either end. I was told these were uncut blanks for making prescription eyeglasses. It would significantly improve the beam focus spot especially for graphics at long distances without affecting the scan angle or pincushion significantly.

    Lenses looked like

  5. #15
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    Yes's but that has nothing to do with images.
    "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

  6. #16
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    Quote Originally Posted by yaddatrance View Post
    For what its worth, back in the day we would actually often correct after the scanheads. The bounce mirrors and dichros would sometimes introduce astigmatism/divergence so we kept a bag of these 3" to 5" diameter lens in the -6 to +6 diopter range in 0.05 diopter increments near zero and .25 diopoter increments toward either end. I was told these were uncut blanks for making prescription eyeglasses. It would significantly improve the beam focus spot especially for graphics at long distances without affecting the scan angle or pincushion significantly.
    This looks really promising, thanks for sharing. Would you be prepared to elaborate a little more on what is actually going on here, optically? Not understanding how it doesn't affect scan angle... Would you use two lenses or one and could you give an example of a configuration from the top of your head? I am a clueless about optics.

  7. #17
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    Try it and let us know what you get. I thought of this years ago but could not find lens big enough to do it.

  8. #18
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    Quote Originally Posted by laserist View Post
    Yes's but that has nothing to do with images.
    Wasn't Humphry's original post asking about a laser projector? I don't understand why you are concerned with images.?.

    Adam

  9. #19
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    Quote Originally Posted by sbk View Post
    Actually, you can have a fat, parallel beam, being focused just before the scanners to match mirrors size, and then after scanners, you use a big diameter lens to re-expand the beam and make it parallel again.

    Pretty sure I already seen that on LOBO projectors and other ones...
    Unfortunately, there would be no angular scanning action this way.

  10. #20
    Join Date
    May 2018
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