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 at
> 632.8 nm wavelength, a fringe count will occur every 312.4 nm, which comes
> 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 sensitvity.
>
> For those interested in using interferometers to measure distance, a
> suitable laser source costs much less than $100. The optics required aren't
> too complex. Basic precision can be 0.5 ppm, if the temperature and
> humidity of the air path are compensated for.
>
> Elliot Burke
>
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