Interferometers

I need to measure the travel and tilt of a small stage over a couple mm. Distance resolution of 0.1um and tilt as large as maybe 20 arc minutes. Any recommendations on something suitable?

Here you go- although its only a .5 micron system. Renishaw may have something else to get better resolution, but lots of places offer laser calibration services using the system below.
XL-80 laser measurement system

0.1µm can be done with inductive sensors. Sony, Mahr, Tesa just to name a few. They even go down to 0.01µm.


Nick

Thanks- I figured people here would steer me to some names I don't normally think of, as I tend to work in the small world of HP/Agilent and Zygo. Various schemes using inductive and capacitance sensing have come up, and might save some money over an interferometer based system, but the interferometers seem to be the most integrated and fastest to get set up for my purposes, albeit at a cost.

CH

seem to be the most integrated and fastest to get set up for my purposes,

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Not that I know your setup, but these inductive sensors are stock. Nothing really special in a grinding shop.

This is just an example: http://www.tesabs.ch/multimedia/docs/2008/05/tesa_axial_probes.pdf

Such (0.5µm) a probe costs around $100, the readout about $1000. Just rough numbers, laser would be magnitudes more I guess.

I think Fowler is a competent partner in the USA to ask for help.


Nick

You could also do this with a combination of something like a Heidenhain MT-25 gage head and ND-28x readout for travel distance, and an autocollimator with return mirror on the stage for angle change, like a Leitz or Taylor-Hobson. If I had a distance measuring interferometer setup available to use, I would choose that first, though.

This has to be a non-contact setup due to the very low force driving the "stage". It's not really a stage, but that description will suffice here. It's the usual case of wanting fully automatic testing and data collection, but not wanting to pay a fortune to do it. Manual methods with an autocollimator and various distance probes (cap or ind) work fine but are too time consuming if a lot of measurement points are needed. I know machine beds are characterized for both slope (to get straightness) and distance in one pass, but I don't know who makes the equipment for that. One other requirement- this thing is very tiny, so nothing larger or heavier than a 1/2" diameter mirror can be attached.

CH

I think you could check out Hamar Laser and Optodyne, both of whom make a variety of optical (laser, mostly) calibration systems for machine tool alignments. Zygo also makes (made?) distance measuring interferometers, and HP/Agilent has put together systems for that application in the past, as I recall. Your definition of "pay a fortune" might enter into consideration, and it's not clear to me whether any of that stuff would get you to 0.1 um reliably.
If you wanted to turn it into a DIY project, you could probably do "something" with a CCD camera on an autocollimator, frame grabber card, and PC, with some software expertise to write some code. I'm actually planning a similar type of system for larger XY stage calibration/assessment. Sounds like you've got some fairly small stuff. You might also consider something like an interferometric surface profiler system, if you were able to find something used on eBay with a low-power Mirau or Michelson objective and suitable software applications, with a 0.1 um encoder on the Z-axis.

Conrad Hoffman said:

Thanks- I figured people here would steer me to some names I don't normally think of, as I tend to work in the small world of HP/Agilent and Zygo. Various schemes using inductive and capacitance sensing have come up, and might save some money over an interferometer based system, but the interferometers seem to be the most integrated and fastest to get set up for my purposes, albeit at a cost.

CH

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Just curious, you mentioned Agilent. Do you work with Agilent, or are you talking Agilent lasers? I work at Agilent. My buddy repairs/calibrates the laser measurement systems.

Companies I've worked for used HP/Agilent laser systems in the past, but I don't have such available today. My first thought was to diy something, but those efforts don't come off as low cost as one might think. In a make/buy decision where everything is factored in, especially software, you don't save much. I also don't want to encourage those who think I head out back with a shovel and a forge, to dig up some ore, every time we need a piece of metal. I admit, however, it is my first instinct.

In another life I used to build surface profiling microscopes with Mirau objectives. Really cool stuff. I still remember how to align the objectives, which can get out of whack pretty easily, but they're awfully expensive. I see them every now and then on eBay.

Thanks,
Conrad

I wonder if an optical comparator might work.

Nick Mueller said:

0.1µm can be done with inductive sensors. Sony, Mahr, Tesa just to name a few. They even go down to 0.01µm.


Nick

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0.01um?! Which one does that?