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Thread: Polygon scanners from laser printers ?

  1. #1
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    Question Polygon scanners from laser printers ?

    Hi, does anyone have some experience with the polygon scanner assemblies from laserprinters ?
    Most of them are very slim, and I would like to land a multimode beam on them.
    So I'm looking for polygon mirror assemblies that have a aperture at least 4mm high.
    There are lots on ebay and Chinese sellers, but none of them have dimensions. ony fits model XXXX.YY.

    Also some of them appear to have "staggered" facets for raster scanning, I don't want that.
    Als some seem to have concave facets , that's not useful either.

    All info much appreciated.

  2. #2
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    ... have two from older (second gen) laser printers -- one has glass (f-theta) lenses, the other plastic ones, injection molded.

    The polygon mirrors are simple flat, no other tweaks or arrays seen ...

    Viktor
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  3. #3
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    You can find plenty of these for sale on eBay. I wound up purchasing some while I was doing research for my book.

    I don't think many people have explored how these can be used for laser light shows, so this is fertile ground for sure!


    Bill

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    ... I've used them for UV-exposing UV-sensitive films or PCB's - stepper for X, the scanner for Y.

    For lasershows it's not so optimal because of the long distance to the second mirror, if intended for XY-scanning ...

    Viktor
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  5. #5
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    Quote Originally Posted by VDX View Post
    For lasershows it's not so optimal because of the long distance to the second mirror, if intended for XY-scanning ...
    With more mirror facets, wouldn't that cut down the raster scan angle, making it more viable for xy?
    If you're the smartest person in the room, then you're in the wrong room.

  6. #6
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    ... but then it's a complete different scanner-setup - not comparable with the laserprinter ones

    This wouldn't be vector- but raster-scanning -- think about the old-style "laser-TV's" with a tilted polygon-scanner with the polygon for the X-line and tilting to get the Y position ...

    Viktor

    *** EDIT *** -- X/Y-mismatch
    Last edited by VDX; 07-09-2020 at 08:43.
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  7. #7
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    I bought a polygon scanner off E-bay almost 20 years ago for like $30 just to play with. It was a pull from a grocery-store checkout scanner. I think it had 10 mirror facets, and each one was about an inch tall by maybe an inch and a quarter wide. Never did check the RPM, but it was fast! Nice smooth rotor though - once it got up to speed it was very stable.

    Years later I learned that folks were using similar technology to do "laser TV" with the polygon scanner providing the high-speed X-axis raster scanning. The NTSC video spec has the horizontal sync running at 15.7KHz, so to hit that mark with a polygon scanner you take the rotor RPM times the number of facets and divide by 60. That has to equal 15,734, assuming that your Y scanner is only doing 1 line at a time. In practice, this leads to either ridiculously small scan angles (because you have 100 facets or more) or ridiculously fast rotation speeds, or both!

    It's my understanding that the actual laser TV implementation had the Y scanner drawing 4 lines at once, which would reduce the rotor RPM by a factor of 4. Nonetheless, that rotor was undoubtedly still spinning pretty damned fast... And all of this for just 525 lines of resolution.

    Quote Originally Posted by VDX View Post
    For lasershows it's not so optimal because of the long distance to the second mirror, if intended for XY-scanning
    If you are using a polygon scanner for the X axis you are no longer doing vector (XY) scanning. Instead, you're doing raster scanning, and there's going to be some artifacting when you convert the image between the two formats.

    For example, in vector scanning it's possible to scan a truly unbroken line in any direction, but in raster scanning you can only scan an unbroken line horizontally. If you try to raster-scan a vertical line there will be dead space between each successive scan line. (This can be somewhat minimized by reducing the vertical scan angle and relying on divergence to smear out the dead space between each horizontal scan line, but it's never perfect.)

    Regarding the distance between the Y mirror and the scanning polygonal X mirror, I'm not sure what your concern is.?. The only thing that limits how close the Y mirror can get to the polygon scanner is the difference in radius between the middle of a flat mirror face and the protruding corner radius. More importantly, having the Y mirror set back further from the rotor is actually desirable, as this means the Y scanner can operate through a narrower scan angle. True, it takes up more space inside the projector, but that's hardly a major concern.

    No, the real issue was all the custom hardware, software, and firmware you needed to make it all work. From what I remember reading about those early laser TV displays (all of which were one-off, custom rigs), the hassle to keep everything synchronized was only part of the problem. The other big headache was the fact that the color modulation signal was running at Mhz frequencies, and in those days unless you were using a PCAOM the hardware just couldn't keep up. (Although these days with all direct-injection diode lasers I think it could probably be done if you had really good drivers.)

    Quote Originally Posted by absolom7691 View Post
    With more mirror facets, wouldn't that cut down the raster scan angle, making it more viable for xy?
    More facets mean a narrower scan angle, yes. (360 degrees divided by the number of facets equals your theoretical maximum raster scan angle.) But again, it's not XY (vector) scanning at this point, it's raster scanning. So first you need to convert the vector image to a raster image. Then you need to generate new color modulation signals and Y scanner position data for this raster image, and finally you have to synchronize those signals with the rotation of the polygonal scanner in order to display it.

    Adam

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    I used two to make a crude raster laser video projector. worked ok but too slow. still beats scanners and resonant scanners.

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    Quote Originally Posted by VDX View Post
    ... I've used them for UV-exposing UV-sensitive films or PCB's - stepper for X, the scanner for Y.

    For lasershows it's not so optimal because of the long distance to the second mirror, if intended for XY-scanning ...

    Viktor
    I’m trying to do the same using polygon scanners from laser printers. How were you able to do it for sensitizing PCB photoresist?

    Can you share details how you did so?

    Are you using the lens that came with the laser printer? I read that these lens are no good since they are specifically designed for IR laser wavelength.

    Thanks.

  10. #10
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    ... had different optics with plastic- or glas-lenses from old laser printers, which weren't AR coated, so could be used for UV too, but had to adjust the collimaton for the diode to match the f-theta-FL to get a focal plane, as the FL is different than for NIR ... was a bit "tricky" though ... today I have a galvoscanner-head for 355nm, so much easier

    Viktor
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