Re: [CAD_CAM_EDM_DRO] Ref: Laser Metrology

The problem with solid state lasers is that their coherence
distance is short. That is the distance that the beam travels
before the mix of light frequencies mismatch by 180 degrees.
All lasers are a mix of light frequencies. The frequency range
is related to the laser resonant cavity length. In a solid state
laser the cavity is very short so the coherence length is short.
Gas lasers are much better in this application.

Laser interferometry is hard to do and that is why it is expensive.

Pete.

----- Original Message -----
From: dickw@...
To: CAD_CAM_EDM_DRO@yahoogroups.com
Sent: Monday, April 07, 2008 3:52 PM
Subject: Re: [CAD_CAM_EDM_DRO] Ref: Laser Metrology


Ultrasound wavelengths are probably too long.

I was thinking more in terms of some hack using a DVD laser and some of
the junk optics associated with it. A good setup could drive servos
without encoders and provide amazing repeatability.

D.