Re: Beam expander and focusing system for scanning head
From: Jamie Carter (jacarter3_at_onebox.com)
Date: 10/05/04
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Date: 5 Oct 2004 06:19:34 -0700
Marco,
I have designed three element f-theta lenses that maintained spot size
over about +/-12 degree scan angles. These were small optics for
applications that scanned a limited physical distance. Larger versions
have been made that used rectangular aperture lens elements for large
scan distances without huge circular lenses.
You application in the LWIR limits the choice of materials that can be
used and these are generally quite expensive (material and
fabrication). Does this system scan in two axes? What is the actual
scan angle range? What calibrated focal length are you trying to
achieve (calibrated focal length is the slope of the f-theta
distortion curve)?
Fortunately, your application is narrow band (depending on the flavor
of the CO2 laser); so the design may be straight-forward. Not to
mention that these elements may be diamond turned and allow for more
complicated surfaces in a simpler package. I do not have any
experience with the GSI Lumonics product that Leonard alludes in his
post. They must have had a reason to move a lens with a galvo, but I
can't fathom a reason for this without a lot more information.
There are many vendors that market scan lenses and scan systems. You
might check with the Lincoln Laser Co., they specialize in polygonal
scanners, but also have experience in the optical design of scan
lenses.
James Carter
http://www.jacarter3.com
marco@marylon.com (Marco) wrote in message news:<ae17182d.0410041335.6c8121b8@posting.google.com>...
> Hi, thanks for help. I'm an electronic enginner working in the
> automation idustry, where I have to deal with lasers and scannig
> heads. I've been asked, as I'm getting deeper inside optics by my own,
> to take a look to a pre-focused scanning head project made few years
> ago for a CO2 laser. The system has three elements, a moving biconcave
> followed by a closed doublet with a meniscus and a plano-convex ZeSe
> lenses, but has not been done for constant spot size all over the
> field. I'm trying to get some tips, suggestions or whatever to, on one
> side, learn the way such a constant spot size configuration should be
> done and, on the other side, to better understand optics. I ask you
> even more, some titles you think I should read to build good optics
> knowledge funded on solid basis, at the moment I'm reading Smith,
> Fischer, Hecht, Pedrotti, Siegman, I've got Born-Wolf as a reference
> and look forward to get Goodman.
> Thanks, Marco
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