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Thread: Maximizing Scanner Apature

  1. #1
    Join Date
    Feb 2011
    Location
    New Hampshire
    Posts
    3,513

    Default Maximizing Scanner Apature

    I'll post some pics as soon as I can clean the set up and make this idea easier to see, but I noticed that even my large aperture Eye Magic scanner mirrors will leak an expanded beam(to reduce divergence) especially at larger scanning angles. And especially from the second mirror in the series to receive the beam. What I discovered is that by setting this mirror at significantly less than the standard 45 degrees, as in 15 degrees, all I had to do to correct for the table directed output was to set an adjustable third steering mirror nearly flat below the scanners and send a non-distorted image to the projection screen across the room. The leakage disappeared and the effective aperture on this mirror went from 8.5mm to 12mm!
    OK, so I then tried to adjust the first mirror in the series, but this is more complicated because with minimal separation between the mirrors (also important) the output from the first mirror now must strike the second at an oblique angle and the image projected on the screen from the third steering mirror is bowed. Fortuitously, the oblique beam reflects off the second mirror down and away from the scanners and I was then able to set the second mirror's AOI all the way to 0 degrees and limit the distortion to only one axis. The length of the second mirror allows me to reduce the first mirror's AOI to 30 degrees and increase it's effective aperture from 8.5mm to 11mm. I believe the Pangolin software and maybe other packages can correct for geometric distortions similar to what I see in the projected test patterns. I haven't explored these more advanced features that they say are included to compensate for curved or highly angled projection screens, but maybe someone else has.

    Has any one tried this?

  2. #2
    Join Date
    Feb 2008
    Location
    Northern Indiana
    Posts
    921

    Default

    Cambridge builds XY mounts with the X scanner at an angle. I assume larger aperture is the intent. Also, I think it would allow the mirrors to be mounted closer together, thereby allowing for a shorter Y mirror.

    How do you like your Greeks? What is the best speed and angle you get with those mirrors?

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

    Default

    I like them. I had a set of DT 20 scanners with 10mm mirrors and both these and the EMs preformed similarly and handled 18-20 K speeds without any distortion or tails at approximately 40 degrees. The Eye Magics come factory tuned; I haven't had to adjust them yet. The amps run hot and need a good fan, but I now think the benefit of the rear stud for mounting makes it easy to customize each mount and allow independent mounting. I would buy them again.

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

    Default

    It works! I love Pangolin. With 5 min. of tweaking in the geometric correction window the test grids are symmetrical, non-rotated and essentially perfect. I now have at least 11mm aperture scanners ( dynamic and not just the square root of 2 x the static mirror width) and I didn't pay extra. I can't wait for my prisms.

  5. #5
    Join Date
    Apr 2006
    Location
    Miami, FL
    Posts
    3,590

    Default

    I have the 6.5mm aperture eyemagics and can scan at 30k without issue? not the ilda test pattern but regular graphics shows etc at huge angles

    I like them a lot

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