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Thread: Beam positionning before the dichro?

  1. #1
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    Default Beam positionning before the dichro?

    It's not the first time that I see this organization of the blue beam before entering the dichro filter, and I'm wondering why spend a extra mount and a mirror, instead of directly reflect the blue with the dichro?
    Is it to have a better angle for the input of the green beam?

    (I ask coz I'll soon receive my blue laser )


  2. #2
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    Thats a pretty messy set up imo.

    Your best bet, is to get edmond's 45 degree dichros, and get the beam heights of the 3 lasers the same.

    then you only need 2 dichros, and no bounce mirrors
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  3. #3
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    HA!!! You should see mine... and I have it set up the way you state... MY set up is MESSY! but I got a nice lil piece of aluminum from astroguy, so it should get cleaned up... sometime soon.

    If I had a table like that though my set up would be CLEAN... That's looks like a nice table there.
    Love, peace, and grease,

    allthat... aka: aaron@pangolin

  4. #4
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    Aaron;

    Your setup might be "ghetto-fabulous", but you're still using 45 degree dichros, right? And your lasers are the same height off the table.?.

    I think Dave was talking about the needless addition of a bounce mirror in the blue beam path. His point was, why introduce an additional souce of loss when blue is so expensive to generate in the first place. (It looks like they're using it to get the blue beam height down to match the green, but it would have been better to adjust the height of the laser itself.)

    Adam

  5. #5
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    Im not sure that bounce mirror is to lower the blue beam. Think about it. If you took that beam and aimed it down at a few degrees when it hit the dichro it would reflect off at an equal angle - and would end up as a nice blue blob on the breadboard, unless the dichro was angled upwards -which it does not appear to be.
    I think its used to match the angle of the highest reflectivity of the dicro. The laser is mounted nice and square but this allows the beam to hit the dichro at a shallow angle - that certainly aint 45 degrees (note also the dichro istelf is angled slightly to assist in getting the right angle to run it along the greenies path). Tha alternative would be to place the Blue where the bouncer is and there clearly is not enough room - and making enough would have expanded the whole system bay quite some margin.

    Rob

  6. #6
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    Quote Originally Posted by stanwax View Post
    Im not sure that bounce mirror is to lower the blue beam. Think about it. If you took that beam and aimed it down at a few degrees when it hit the dichro it would reflect off at an equal angle - and would end up as a nice blue blob on the breadboard, unless the dichro was angled upwards -which it does not appear to be.
    Well, you must have hawk-eye vision because I certainly can't tell from looking at the pic. Although I've got fucky eye sight...

    I'd say more likely than not, its to lower the beam. Even if it's only by a couple of mm, you wouldn't be able to tell that from looking at a birds eye view photo.
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  7. #7
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    Rob;

    I dissgree; from the picture it looks to me like the green/blue dichro is mounted at an angle, and the mount is clearly adjustable. Since you need two reflections to adjust beam height, that's what I'm assuming they're doing here. The first mirror brings the beam down, and the second reflection (off the face of the dichro) evens the beam back level with the green.

    If they just wanted to optimise the angle, they could have re-shuffled the positions of the lasers inside the case... (Or purchased a 45 degree dichro in the first place.) Why add an extra reflection if you don't have to?

    Adam

  8. #8
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    Quote Originally Posted by Buffo View Post
    Why add an extra reflection if you don't have to?
    Adam
    It's more beautiful to see the beam reflect as this? Lol

    But the more probable is to adjust height of the blue beam, since the lasers seems to be placed directly on the base plate, they probably don't have the same height...
    And if it's a proper mirror, they only lose 1-2% on the blue.

  9. #9
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    I would only put it together like that if I had a head height missmatch & the only available dichro worked more effeciently at that acute angle.

    IMHO the first mirror the blue hits looks tilted upwards a tad.

    Pit.
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  10. #10
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    We figured the easiest way to avoid using extra height compensating dichros, whilst at the same time keeping it all neat was to get different thickness aluminum "riser" plates machined up for us.

    We then just use a big heatsink under the beam table. This allows us to seal off the optical chamber so we don't get nightclub fuzz all over the optics...

    We smeared the aluminum riser plates with a load of sticky icky white stuff for better heat transmission...

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