Questions on choosing a rotary stage
Questions on choosing a rotary stage
(OP)
Hi...
Do you guys happen to know any good rotary stages that would work in the vertical plane? I searched Physics Instrument, Zaber and New Port etc. but mostly they only specify a maximum load weight so I assume they would only work well in the horizontal plane.
I am designing an automated "goniometer" to make optical scattering measurement. The key part is an aluminum BAR1 carrying a small optical tube assembly (telescope) pointing at ground to collect scattered light. Let X and Y be Cartesian coordinate in horizontal and Z along the vertical up (X cross Y = Z), then BAR1 will rotate around axis-Y in the X-Z plane and my telescope will always point to X=Y=Z=0. Let Theta be the angle the BAR1 makes with axis-Z, and my measurement would require Theta ranges from (-80, 80) deg., with angular resolution about 0.05 deg. Such a configuration would require a rotary stage working in the vertical plane (X-Z) with a load up to ~80Nm (I can add some counter-weight to reduce the torque caused by BAR1's weight and its telescope).
I would be very grateful for your suggestions/recommendations on the followings:
(1) a rotary stage working in vertical plane with angular resolution ~0.05 deg. and a torque load of ~80 Nm;
my BAR1 rotating speed doesn't need to be too fast (b/c I need to record scattering at each desired annular position), e.g., 0.1 deg/s; so worm gear is a good idea?
(2) as the whole optical system would be sitting on one whole bench, for the motor the quieter the better. Should I choose a DC servo or a stepper?
(3) to prevent BAR1 from hitting my incident optics (BAR2 fixed at another angle between (-80, 80) deg), what possible mechanism would be best?
Many thanks!
Do you guys happen to know any good rotary stages that would work in the vertical plane? I searched Physics Instrument, Zaber and New Port etc. but mostly they only specify a maximum load weight so I assume they would only work well in the horizontal plane.
I am designing an automated "goniometer" to make optical scattering measurement. The key part is an aluminum BAR1 carrying a small optical tube assembly (telescope) pointing at ground to collect scattered light. Let X and Y be Cartesian coordinate in horizontal and Z along the vertical up (X cross Y = Z), then BAR1 will rotate around axis-Y in the X-Z plane and my telescope will always point to X=Y=Z=0. Let Theta be the angle the BAR1 makes with axis-Z, and my measurement would require Theta ranges from (-80, 80) deg., with angular resolution about 0.05 deg. Such a configuration would require a rotary stage working in the vertical plane (X-Z) with a load up to ~80Nm (I can add some counter-weight to reduce the torque caused by BAR1's weight and its telescope).
I would be very grateful for your suggestions/recommendations on the followings:
(1) a rotary stage working in vertical plane with angular resolution ~0.05 deg. and a torque load of ~80 Nm;
my BAR1 rotating speed doesn't need to be too fast (b/c I need to record scattering at each desired annular position), e.g., 0.1 deg/s; so worm gear is a good idea?
(2) as the whole optical system would be sitting on one whole bench, for the motor the quieter the better. Should I choose a DC servo or a stepper?
(3) to prevent BAR1 from hitting my incident optics (BAR2 fixed at another angle between (-80, 80) deg), what possible mechanism would be best?
Many thanks!





RE: Questions on choosing a rotary stage
RE: Questions on choosing a rotary stage
Parker is another: http://di
TTFN
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RE: Questions on choosing a rotary stage
Have you looked at www.Thorlabs.com or www.Standa.lt
RE: Questions on choosing a rotary stage
2) We were collecting low energy scattered light and motor noise was not an issue. If noise is a problem can you pause the motor to make a measurement?
3) The interface was nice as far as the software (we used labview) so software stops could be used to limit travel. Not sure if that is failsafe enough for you but you could add proximity switches as well.
Harold
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RE: Questions on choosing a rotary stage
http://ne
RE: Questions on choosing a rotary stage
Counterweights are usually used to minimize linear perturbations that affect angular stability, but ensuring that the CG is as close to the rotation axis as possible.
As for type of motor, a servo is preferrable, since a stepper will inject mechanical impulses into the optical bench. However, if your setup is done with a plausible massive tabletop, the injected impulses should affect angular behavior, particularly if your angular resolution requirements are only 0.05 deg.
TTFN
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RE: Questions on choosing a rotary stage
How can the telescope make a fixed angle to Z axis if it is in the x-z plane. Do you mean it makes an angle to the Y axis.?
I like a stepper for this since you have only modest speed requirements and you can even run it open loop
That means a 1.8 deg stepper would need a GR of 18:1 .and assuming.001" backlash in the final stage, a 5" dia gear would have an error of about .001/2.5*180/Pi= .024 deg.
RE: Questions on choosing a rotary stage
I don't think what the OP requires can't be done with an off-the-shelf stage. In order to point to a fixed spot on the ground, the center of rotation needs to at ground level.
I think what he's actually asking for is something that looks like a semicircle, whose center is what he wants to point at, and the telescope travels along the semicircle, with the telescope pointed at the center.
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RE: Questions on choosing a rotary stage
IRstuff,
So, are you saying that the Z axis is the axis of rotation and the telescope is an element of the truncated cone of partial revolution?
RE: Questions on choosing a rotary stage
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What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Questions on choosing a rotary stage
So, picture a semicircular arch and it's radii, pointing to the semicircle's center, located on the ground. The telescope must align to each of the arch's radii as it traverses along the arch. That's my interpretation of the OP. What that requires is a rotation of the telescope and a translation, so a goniometer won't do the job by itself.
TTFN
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RE: Questions on choosing a rotary stage
zekeman: IRStuff's answer is correct; the telescope makes an angle Theta with the vertical Z-axis and Theta varies from [-80, 80] degs. To better illustrate my setup, the basic layout can be found in Fig. 1 (page 5221) in the following free online article:
ht
(just click the "View Full Text: Acrobat PDF")
In the above primitive setup, I record scattering data at each desired viewing angle theta, and manually rotate the gonio bar to the next angular position. My goal now is to use a motor-rotary stage-controller system to control the rotating bar carrying the "viewing tube assembly" in Fig.1.
IRStuff: (1)once I have set up the system, my sample holder will be fixed at the center of the semi-circle and no translation will be needed (this will be a laboratory-based device not field one, sorry I did not point this out earlier).
(2) Also thanks for pointing out the torque thing; yes I did mean to make the CG closer to the rotation axis after adding the counter-weight so that the whole system would be more stable; and such an addition would indeed increase the inertia...I'm digging out my Mechanics notes right now....:)
(3 in your 2nd reply post, "..impulses should affect..." should be "...impulses should not affect....", right?
Cheers!
RE: Questions on choosing a rotary stage
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RE: Questions on choosing a rotary stage
3> yes, should NOT, but it depends on the stepper impulse size and how criticalthe angular stability is.
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RE: Questions on choosing a rotary stage
Harold
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Dell 690, Xeon 5160 @3.00GHz, 3.25GB RAM
nVidia Quadro FX4600
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RE: Questions on choosing a rotary stage
IRStuff: Now I see....; in remote sensing often times people only need to measure scattering at a couple incident angles, say 0 deg (normal), 30 deg and 60 deg, in contrast to the denser viewing angles desired; so to reduce cost and complexity I would fix my collimator arm by using some clamping mechanism. But it's good to know your suggestion.
Harold: I guess my (-80, 80) notation was confusing...sorry about that; what I really meant was viewing the sample from normal to 80 deg, with minus angles clockwisely and plus ones counter-clockwisely (or the other way) . In reality there are "forbidden" angular areas where the telescope arm would mechanically interfere with the collimator arm. Also very likely I will end up with 65 deg or so, as the cosine response of my radiometer (telescope) would yield poor signals above 70 deg., no matter how hard I try...
Cheers!
RE: Questions on choosing a rotary stage
The setup is similar to an ellipsometer, and in my dusty recollection, the viewing assembly(detector) and laser source for an ellipsometer were mounted on radial arms pivoting on an axis going through the top of the sample stage.
In your case, if the source and viewing angles are independent, you would need two rotation stages that could handle large cantilevered loads. Both would parallel and have their centers of rotation go through the sample position. If you imagine arms that goto each assembly in your Fig 1, and imagine rotation stages centered at the sample location, you get the idea. You would need to elevate the sample stage sufficiently off the tabletop to allow the rotation stages to extend below below the sample stage. It'll look like a two-wheeled cart with radial arms extending upward from each wheel when you're done.
Any of the suppliers cited above should work, depending on the actual weights you might have for the two assemblies, and the distance you need from the sample.
TTFN
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RE: Questions on choosing a rotary stage
Second, if the measurements are being taken at fixed increaments, the telescopes might be cheaper than the rotary stages. Why not make a few?
Harold
SW2010 SP1.0 OPW2010 SP1.0 Win XP Pro 2002 SP3
Dell 690, Xeon 5160 @3.00GHz, 3.25GB RAM
nVidia Quadro FX4600
www.lumenflow.com
RE: Questions on choosing a rotary stage
Given what he needs to do, it's not clear that horizontal would be an improvement, since that would make the sample sit vertically, blowing it the figurative breeze, and the other rotation stage would have to be mounted and cantilevered about the sample.
TTFN
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RE: Questions on choosing a rotary stage
Harold: IRstuff already answered the fixed position question, here are something more; indeed some designs of the BRDF instrument do use fixed viewing positions; for example, if we can fix many viewing fibers (on a dome for example) all pointing to the sample surface collecting the scattered radiance, no moving parts would be needed (isn't that nice?); an example instrument can be found here:
htt
However, such a design is usually for faster field instrument when higher angular resolution is not needed (remember the angular resolution is determined by the ratio of the aperture stop diameter to the distance to sample surface); if one wants to look at some subtle angular structures such as the rainbow (by transparent and spherical grains), a much finer angular step would be desired.
As for why a horizontal sample surface: I will be mostly dealing with particulate samples: sand, soil, volcanic ashes.... i.e., a packed surface will be measured. If only air-suspended particles (e.g., aerosol jet) are desired, a horizontal gonio layout would suffice, see e.g.:
1. http
2. "Experimental determination of scattering matrices of dust particles at visible wavelengths: The IAA light scattering apparatus
Munoz et al
Journal of Quantitative Spectroscopy and Radiative Transfer
Volume 111, Issue 1, January 2010, Pages 187-196
Cheers!
RE: Questions on choosing a rotary stage
But, you can see how that might work with the sample horizontal, and you would need to have the stationary bases of the rotary stages on either side of the sample, and the viewer and source outboard on their arms.
TTFN
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