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| Mikko Syrjälahti... |
 Posted: Fri Oct 16, 2009 1:26 am |
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Hello,
I'm looking for a (red) laser module that would output a beam with about 0.1x3mm,
cross sectin, like a line laser but with limited line length. This will be reflected
from several surfaces and then hit a line CCD to measure the positions of reflections.
The intensity of the reflection will also be measured (to +/-10%), so the intensity over the
line should be relatively constant.
The actual application is measuring stress in glass by scanning the beam over a sample.
The beam will be circular polarized and the intensity of reflections (after analyzer) will
change during the scan. (I've got a pat. pending on a device using this and doing something else
in addition.)
The beam may (actually makes pointing easier) widen a little bit in the 3mm direction.
Distance of measurement is 10-200mm, after that the beam quality can be whatever.
I'm currently using in an another device simple module with a slit before the collimating lens.
This of course gives some interference lines and the beam profile is not that good.
Any suggestions on ready modules or ideas customizing are welcome!
--
Mikko |
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| Ron Gibbs... |
| Posted: Fri Oct 16, 2009 8:59 am |
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""Mikko Syrjälahti"" <mikko.syrjalahti at (no spam) NO.tkk.SPAM.fi> wrote in message
news:h4j63afer4z.fsf at (no spam) vipunen.hut.fi...
[quote:ddd43e6e80]Hello,
I'm looking for a (red) laser module that would output a beam with about
0.1x3mm,
cross sectin, like a line laser but with limited line length. This will be
reflected
from several surfaces and then hit a line CCD to measure the positions of
reflections.
The intensity of the reflection will also be measured (to +/-10%), so the
intensity over the
line should be relatively constant.
The actual application is measuring stress in glass by scanning the beam
over a sample.
The beam will be circular polarized and the intensity of reflections
(after analyzer) will
change during the scan. (I've got a pat. pending on a device using this
and doing something else
in addition.)
The beam may (actually makes pointing easier) widen a little bit in the
3mm direction.
Distance of measurement is 10-200mm, after that the beam quality can be
whatever.
I'm currently using in an another device simple module with a slit before
the collimating lens.
This of course gives some interference lines and the beam profile is not
that good.
Any suggestions on ready modules or ideas customizing are welcome!
--
Mikko
You need more than just a laser module for this. Laser beams do not come out[/quote:ddd43e6e80]
this size, and would rapidly diverge (asymmetrically) if they did, by the
fundamental laws of diffraction. You need a proper optical system, properly
designed by a proper optical designer; it's by no means a trivial scanning
system design, from your description.
Ron
--
Gibbs Associates
Optical Design Consultant
www.gibbsassociates.co.uk |
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| AES... |
| Posted: Fri Oct 16, 2009 10:44 am |
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Guest
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In article <4ad88a53$0$677$c5fe31e7 at (no spam) read01.usenet4all.se>,
"Ron Gibbs" <ron.gibbs at (no spam) physics.org> wrote:
[quote:39582fbe79]You need more than just a laser module for this. Laser beams do not come out
this size, and would rapidly diverge (asymmetrically) if they did, by the
fundamental laws of diffraction. You need a proper optical system, properly
designed by a proper optical designer; it's by no means a trivial scanning
system design, from your description.
Ron
[/quote:39582fbe79]
You _might_ be able to cobble up something where you use multiple
reflection in a tilted glass slab with highly parallel faces and a
mirrored back surface to split your initial (circular) laser beam into
half a dozen parallel spots or beams, all (nearly) the same size and
parallel to each other.
You could then view that line of spots as your "line", and maybe use a
reverse beam collimating telescope to demagnify this array of spots down
to the smaller starting size you want.
But, this will be a kludge, and at best a very weak substitute for the
better advice given above. |
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| Bob May... |
| Posted: Fri Oct 16, 2009 3:06 pm |
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Guest
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If you're just looking for stress in the glass, you reeally want a linearly
polarized beam so you can tell the angle of the the null of the beam.
I'd more take a general light sourece the width of the glass, if possible,
with a polariod to linearize the light and look at the glass on the other
side with a camera/linear array with a rotatable polariod filter. At the
right angle of the polarioid, the light will null out and you can see
stresses as light places.
--
Bob May
rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net |
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| Samuel M. Goldwasser... |
| Posted: Fri Oct 16, 2009 5:33 pm |
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AES <siegman at (no spam) stanford.edu> writes:
[quote:9b889c1b68]In article <4ad88a53$0$677$c5fe31e7 at (no spam) read01.usenet4all.se>,
"Ron Gibbs" <ron.gibbs at (no spam) physics.org> wrote:
You need more than just a laser module for this. Laser beams do not come out
this size, and would rapidly diverge (asymmetrically) if they did, by the
fundamental laws of diffraction. You need a proper optical system, properly
designed by a proper optical designer; it's by no means a trivial scanning
system design, from your description.
Ron
You _might_ be able to cobble up something where you use multiple
reflection in a tilted glass slab with highly parallel faces and a
mirrored back surface to split your initial (circular) laser beam into
half a dozen parallel spots or beams, all (nearly) the same size and
parallel to each other.
You could then view that line of spots as your "line", and maybe use a
reverse beam collimating telescope to demagnify this array of spots down
to the smaller starting size you want.
But, this will be a kludge, and at best a very weak substitute for the
better advice given above.
[/quote:9b889c1b68]
Perhaps I misunderstoof the question, but it sounds like you would like
a "sheet" of light, 0.1 x 3 mm maintained over a distance of 200 mm.
If that's the case, you may need to rethink what you want or how it
is spec'd.
Generating a 3 mm long line and maintaining that over 200 mm is not
a big problem. A couple of cylindrical lenses will get close.
But the other dimension is, and you're limited by the laws of physics.
Trying to maintain a 0.1 mm width over 200 mm may be impossible.
At 633 nm, a 1 mm diameter beam will have a diffraction limited
divergence of about 1 miiliRadian (mR). A 0.1 mm beam will have a
divergence 10X larger - 10 mR. This means it's expanding at a rate
of 1 part in 100. Divergence is proportional to wavelength and
inversely proportional to diameter, or in this case, thickness.
So, does the 0.1 mm have to be more or less the same over 200 mm,
or does it only matter at the far end (10-200 mm)?
--
sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html
Important: Anything sent to the email address in the message header above is
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| Mikko Syrjälahti... |
| Posted: Sun Oct 18, 2009 1:02 pm |
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"Ron Gibbs" <ron.gibbs at (no spam) physics.org> writes:
[quote:153332ed5e]""Mikko Syrjälahti"" <mikko.syrjalahti at (no spam) NO.tkk.SPAM.fi> wrote in message
I'm looking for a (red) laser module that would output a beam with about
0.1x3mm, cross sectin, like a line laser but with limited line length.
You need more than just a laser module for this. Laser beams do not come out
this size, and would rapidly diverge (asymmetrically) if they did, by the
fundamental laws of diffraction. You need a proper optical system, properly
designed by a proper optical designer; it's by no means a trivial scanning
system design, from your description.
[/quote:153332ed5e]
I already do have a working system, but by using a narrower beam the device
could measure thinner layers of laminated glass.
The numbers are not exact, I'm looking for preferably a ready-made module with beam
as close to the spec as possible. I've seen one with 130um beam in 50-150mm range, but
that was a part of 5kEUR sensor. My target price for the part/assembly is _about_ 50EUR at (no spam) 200pcs,
much above that may be an obstacle.
I checked your website and if you've done something close to this, send me an email!
--
Mikko |
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| Mikko Syrjälahti... |
| Posted: Sun Oct 18, 2009 1:13 pm |
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sam at (no spam) repairfaq.org (Samuel M. Goldwasser) writes:
[quote:a45f127646]Perhaps I misunderstoof the question, but it sounds like you would like
a "sheet" of light, 0.1 x 3 mm maintained over a distance of 200 mm.
[/quote:a45f127646]
About that, but I can change the specs somewhat through the measurement
geometry if I find something close enough.
[quote:a45f127646]But the other dimension is, and you're limited by the laws of physics.
[/quote:a45f127646]
You're absolutely correct, I should've thought of the diffraction limit
before suggesting the 0.1mm. Thanks for pointing that out!
Thicker beam might also work, as long as it is relatively clean. I think even a 0.3mm
clean beam could work.
[quote:a45f127646]So, does the 0.1 mm have to be more or less the same over 200 mm,
or does it only matter at the far end (10-200 mm)?
[/quote:a45f127646]
All the way. But of course I can move&tilt the laser a little bit further to
set the range to 30-180 (relatively easy).
--
Mikko |
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| Mikko Syrjälahti... |
| Posted: Sun Oct 18, 2009 1:28 pm |
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"Bob May" <bobmay at (no spam) nethere.com> writes:
[quote:b1b3e8a786]If you're just looking for stress in the glass, you reeally want a linearly
polarized beam so you can tell the angle of the the null of the beam.
[/quote:b1b3e8a786]
True, my first approach worked with linear polarization. I used nematic LCD panels
to rotate the polarization to null the beam.
You can also visualize stresses from one side by shining a light through a circular polarizer
and looking at the reflection through the same.
The reason behind circular polarization is that I can combine other measurements
to be done at the same time (conductive layers change ellipticity in a different way
than non-conductive reflections, reflection intensity probably behaves better in
glass-plastic-transitions).
--
Mikko |
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