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Thread: Modulation using an MTS110-a3-vis AOM.

  1. #11
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    Yes, in a lab on an optical bench. But would it stay aligned when built into a projector ?
    Would it survive a moderate car trip?

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    Quote Originally Posted by sugeek View Post
    If you can go over your adjustments of the driver I would appreciate it.
    Assuming that your positional and angular settings are fairly optimised.

    Start off with the power and bias pots in the middle.
    Apply a 100Hz 1 volt triangle-wave to the input of the driver and to the X-channel of your scope in x/y mode.
    Connect the signal of a photo detector with the 1st order signal to the Y-channel.
    Then follow this picture:
    Click image for larger version. 

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    These are actual measurements, and converted to percentual values to fit one graph. You'll get the message.

    Surely you can do this with a dc source and a powermeter, but it will drive you insane especially without an analogue readout.

  3. #13
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    I'll do the three point RF one at lunch time. I'm already insane, but you can do it with the dummy load as well, without catching my insanity.

    Steve
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    Quote Originally Posted by -bart- View Post
    Yes, in a lab on an optical bench. But would it stay aligned when built into a projector ?
    Would it survive a moderate car trip?
    Yes, no problems, its a Newport mount.

    I've never had quality problems with good tip/tilt mounts in the field, I have one on my pcaom, which meets the data sheet if I do, but doesn't if I do not. Here is the issue, PLers want their projectors to be point and shoot. Mine need the hood popped for US QC requirements and beam table alignments anyways, so its never a issue. Having the good positioning gear actually makes sense, you can pop the laser in and out quicker and come back to the sweet spot. However my baseplate is one .375 inch plate with a .25 inch plate underneath it, on a frame with L channel stiffeners running along the sides, so mine doesn't flex as much as a thin plate, ie it is a optical table.

    Its amazing what simply mounting a pair of 25 mm by 25 mm standard AL bar stock to the bottom of your baseplate along two sides does for stiffness in both axis. And you can thin them out on a mill or drill for less weight. My first two projectors used 1/8th inch jig plate and had the stiffeners and its worth it.

    []__________[] drawn upside down here.

    In a university lab, with a 5 axis mount, we exceeded the specs on a NEOS pcaom, by 5%.

    You probably only need pitch the cell in one axis for that last 5%. And the only reason your going for the last 5% is the
    reduced time between alignments.

    Steve
    Last edited by mixedgas; 02-03-2010 at 06:27.
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    Hey! Awesome info thread and review, thanks guys

    I just got one of these AOM's too, and i'm wondering what kind of mount i should pick up... i'm on a bit of a budget (<£100-ish? is that too cheap?), but would like something fairly sturdy. Are there any out there someone could recommend?

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    Quote Originally Posted by robotarmy View Post
    Hey! Awesome info thread and review, thanks guys

    I just got one of these AOM's too, and i'm wondering what kind of mount i should pick up... i'm on a bit of a budget (<£100-ish? is that too cheap?), but would like something fairly sturdy. Are there any out there someone could recommend?

    AOM mounts are not a standard part. Your options are 1. adapt existing mirror mount or other scientific angle mount 2. Make your own.

    Make your own is simple in concept. look at the bottom of the AO. See a hole for a pivot pin?
    That is the point the AO needs to rotate about. The simplest way is to make a base plate with a pin sticking out, and a top plate that the AO mounts to, the top plate has a hole for the pin to go through.
    You have slots or large holes for locking screws to go thru the top plate and into threaded holes in the bottom plate. So you then bolt the AO to the top plate, mount it on the pivot, stick it into the beam , align for best power, and lock down the top plate. Your top plate will of course, have to have, countersunk holes in it to bolt the AO with.

    This is a highly simplified explantion. I'm at work, and cant take pics right now.

    I do something a little more sophisticated, adding a instrument grade ball bearing, a spring, and a 80 pitch screw.. They are cheap and make things considerably better...


    Steve
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    Quote Originally Posted by mixedgas View Post
    AOM mounts are not a standard part. Your options are 1. adapt existing mirror mount or other scientific angle mount 2. Make your own.

    Make your own is simple in concept. look at the bottom of the AO. See a hole for a pivot pin?
    That is the point the AO needs to rotate about. The simplest way is to make a base plate with a pin sticking out, and a top plate that the AO mounts to, the top plate has a hole for the pin to go through.
    You have slots or large holes for locking screws to go thru the top plate and into threaded holes in the bottom plate. So you then bolt the AO to the top plate, mount it on the pivot, stick it into the beam , align for best power, and lock down the top plate. Your top plate will of course, have to have, countersunk holes in it to bolt the AO with.

    This is a highly simplified explantion. I'm at work, and cant take pics right now.

    I do something a little more sophisticated, adding a instrument grade ball bearing, a spring, and a 80 pitch screw.. They are cheap and make things considerably better...


    Steve
    I absolutely get you, i just did the drawings for it in my head. Where do you put the bearing, spring and screw? Are they there to adjust angle?

    Would it be worth putting the whole thing on top of some other mount to adjust it in other axes? Why the hell are AOM mounts not standardized components? I guess they're pretty rare these days since direct modulation seems to be more popular.

  8. #18
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    Quote Originally Posted by gogu View Post
    Thanks for sharing bart, great info!

    i found a picture of this ao mount, but don't know where to find one. maybe someone knows:
    I've totally seen that somewhere before too. I'd love to know where this mythical beast came from, is there any other info on the site you found that on?

  9. #19
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    Quote Originally Posted by gogu View Post
    robotarmy, this is the website. its a college lab on ao/q-switchinig
    http://technology.niagarac.on.ca/cou...SwitchAOM.html

    i couldn't find any more info on the mount itself.
    Yeah! That's where i saw it. Looks like it could be a custom part, who knows tho. I'll see what i can dig up, maybe holler at the professor and see what he says, might have a few surplus

  10. #20
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    Quote Originally Posted by robotarmy View Post
    Yeah! That's where i saw it. Looks like it could be a custom part, who knows tho. I'll see what i can dig up, maybe holler at the professor and see what he says, might have a few surplus
    '

    You guys are going overboard here. That is a isomet factory mount. They are kinda custom produced for large volume customers.

    Robotarmy, I put the bearing under the pivot point. The bearing outer is friction fit in the lower block. Its shaft is press fit in the upper block You can skip the translate shown in that mount, it doesn't buy you much. The screw adjusts the angle. The spring pulls against the screw:

    here is a screw:

    Thorlabs.com, look at part number FAS100

    It mounts in a mounting boss: N80L5

    Here is a bearing assembly:




    I use surplus cam followers, they have nice instrument grade needle bearings and a precision shaft. I don't use the threaded ones. I bought a tube of 20 of them with one half inch OD bearings for 5$ at a hamfest. Robotics parts stores stock the bearings for about 5-10$ and the shaft material for about 3$.
    I dont use the threaded shafts, I use drills that are undersize 4-5 thousanths of a inch and press in the shaft and friction fit the bearing.

    You mount the assembly in the projector using a half inch post and post holder, and a mounting foot:

    Thorlabs:

    http://www.thorlabs.com/NewGroupPage...tGroup_ID=1982

    Since the post holder now comes with the proper mounting foot that lets you slide it, you dont need something like this:

    http://www.thorlabs.com/newgrouppage...p_id=47&pn=Ba2

    But a BA1 is the right idea for getting the beam in the right place..

    In a lab you would use a modified one of these: http://www.thorlabs.com/thorProduct....tNumber=KM100P

    The KM100P would work, but it doesnt put the pivot exactly under the crystal.

    or one of these:

    http://www.thorlabs.com/newgrouppage...ctgroup_id=990


    Neos used to sell their PCAOM mounts for 75$. I imagine the price has went up, since I havent bought one in 5 years.

    more to follow.

    Steve
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