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Thread: Galvo blanking mounts?

  1. #1
    Join Date
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    Default Galvo blanking mounts?

    I was doing some studying on galvo blanking.

    Long story short: Have a laser that cannot blank with large size mirrors (10mm) that I want to blank with an additional scanset.
    Have no problem getting 3 galvos but figuring out how to safely galvo blank is what mystifies me.

    What's the mirror arrangement like for galvo blanking and what's the beam path like? I've read things about galvo blanking before a telescope to galvo blanking using a retro reflector with a mirror setup to ensure movements are small.
    What for instance stops the beam from sliding across the X galvo (which can create the beam from reflecting somewhere undesired because it's coming in from a different angle on the on the x galvo briefly).
    Can some intensity fading be achieved using galvo blanking or is it TTL only?

    This is all I could find video wise showing a galvo blanking setup:


    I know the intensity line on the ilda pinout is made for this exact purpose.
    Is there any more information out there?

  2. #2
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    Default

    You can set it up however you like, but here's an example:

    Click image for larger version. 

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    You will get some intensity modulation but if the beam is round it won't be linear.
    "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

  3. #3
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    So these are some images I've gotten by asking around:

    The one with the telescope in theory seems the easiest ... BUT with large powers focusing down on a mirror seems like a good way to instantly fry/puncture the mirror and even worse if you have q-switching.
    Click image for larger version. 

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    There is also this using a retroreflector which requires a much larger mirror to handle both bounces. I reckon it's a fair bit slower then the galvo + telescope approach but at least it doesn't have the issues that come with reducing the size of the beam and offers more intensity control by slicing into the beams width.. *I think* (Unless one would move the galvo further away from the focal point with the telescope to have less energy density on the mirror and more control.
    Click image for larger version. 

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    I would like to try the retroreflector approach however my experience with retro reflectors other then beam brush is very little..let alone sourcing them. It is also said this method creates tails because of the position moving on the mirror the beam comes in.

    I think the telescope approach might be the most feasable one for me if an offset from focal point would still be something that would work..

  4. #4
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    I can share an alternate method that photonbeam came up with that we used for a few years before we got our hands on some A/O cells. I provide a diagram and/or photos later today that used one GS-120PD scanner, no mirrors or optics and a small, thin piece of aluminum can, brass sheeting or similar. It was surprisingly effect for a desperate solution.

    more coming...

    I finally found the "aluminum can" blanking arm (2 versions of it) that were first used by photonbeam (pre- A/O days). I too, used it briefly when photonbeam and I worked together. Here are some photos of the two variations, one longer, one shorter, taken against a .1" grid, .5" major division background. We epoxied the angled-arm onto the shaft of a GS G-120PD scanner, although a GS-G115 scanner is shown in these pics I took tonight. How we glued the angled-arm exactly centered on the galvo shaft is top secret and can never be discussed. The galvo mount shown with the galvo sitting in it is the optics table mount we used. The blanking arm is made from either a 12 oz Dr. Pepper or beer can, formed then spray painted with flat black krylon paint.

    The beam is aligned to just pass between the two vertical blanking faces when the galvo is energized at zero volts by rotating the galvo in it's mount until each vertical face's edge just misses the beam. When the PD galvo scan amp input is at 5 volts (TTL), the gain of the amp is set to precisely occlude the beam.
    Attached Thumbnails Attached Thumbnails BeamOccluder-1c.jpg  

    BeamOccluder-2c.jpg  

    BeamOccluder-3c.jpg  

    Last edited by lasermaster1977; 01-11-2021 at 20:36.
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