vibration sensivity
Posted by
Elliot Burke
on 1999-07-15 23:55:05 UTC
This isn't really too onerous a constraint. Of course, if you are trying to
measure vibration, interferometry is a good way to go. A classic experiment
measured eardrum displacement invivo on the order of 0.1 nm.
In my experience, most moderately rigid setups and tools are adequately
rigid for interferometry. If there is movement or vibration that you can
feel, then most likely the interferometer will detect it too.
I have frequently made interferometers on 2x4's will excellent results.
Antivibration mounts under honeycomb tables are often sold for
inteferometric applications. These are rarely needed, and serve mostly to
intimidate the uninitiated. Mostly I disconnect the air suspension, since
it makes the table rock when weight is shifted. Things don't get noticably
more stable with the air on.
Elliot Burke
measure vibration, interferometry is a good way to go. A classic experiment
measured eardrum displacement invivo on the order of 0.1 nm.
In my experience, most moderately rigid setups and tools are adequately
rigid for interferometry. If there is movement or vibration that you can
feel, then most likely the interferometer will detect it too.
I have frequently made interferometers on 2x4's will excellent results.
Antivibration mounts under honeycomb tables are often sold for
inteferometric applications. These are rarely needed, and serve mostly to
intimidate the uninitiated. Mostly I disconnect the air suspension, since
it makes the table rock when weight is shifted. Things don't get noticably
more stable with the air on.
Elliot Burke
>Message: 11at
> Date: Thu, 15 Jul 1999 20:17:23 -0700
> From: Bill Martin <wwm@...>
>Subject: Re: counts per inch, my $0.02
>What about them being "too" sensitive, as in picking up all the
>vibrations from the machine, the building, everything moving nearby?
>Bill Martin
>Elliot Burke wrote:
>
> From: "Elliot Burke" <elliot@...>
>
> If the DRO is used with a Twyman-Green interferometer using a HeNe laser
> 632.8 nm wavelength, a fringe count will occur every 312.4 nm, which comessensitvity.
> out to 80278 counts/inch.
> Other types of interferometers may have twice this sensitivity.
> Shorter wavelengths (doubled YAG at 532 nm) will have even more
>aren't
> For those interested in using interferometers to measure distance, a
> suitable laser source costs much less than $100. The optics required
> too complex. Basic precision can be 0.5 ppm, if the temperature and
> humidity of the air path are compensated for.
>
> Elliot Burke