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Date: 24 May 2007 00:22:59
From: Farsang
Subject: Commercial Telescope for high Power Beam
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Hi:
We have a fiber with a 300 Watts output at 900 nm, we'd like to
collimate this output and generate a spot of about 5 Cm dia. at 1 Km
away. Are there commercial telescopes that we could modify its
input optics (to couple in the fiber output) to achieve this and can
they handle 300 Watts light power?
I was thinking of a reflective Newtonian Telescope with its eyepiece
replaced by an imaging optics that images the fiber's core onto the
focal plane of the telescope primary mirror. This imaging optics
would have an appropriate ouput numerical aperture to create a
collimated beam of 5 Cm dia. coming out of the the telescope primary
mirror. Is this feasible and can the telescope optics handle 300
watts ( the primary mirror probably has an enhanced aluminum coating)?
Alternatively we could collimate the fiber output and send it into a
Galilean beam expander (refractive type) but our preference is a
commercial telescope (preferably with a tracking capability) that
could with some modification give us this 5 Cm output beam.
thanks for your comments and suggestions.
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Date: 24 May 2007 20:10:36
From: rmigliac@yahoo.com
Subject: Re: Commercial Telescope for high Power Beam
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I happen to have a 20X SORL Beam expander for sale on Ebay.
Item number: 140120742585
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ih=004&sspagename=STRK%3AMESE%3AIT&viewitem=&item=140120742585&rd=1&rd=1
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Date: 24 May 2007 14:32:17
From: Jamie
Subject: Re: Commercial Telescope for high Power Beam
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Sorry but you can't magically reduce the fiber's cone angle with a
lens without increasing the apparent size of the of the fiber tip.
This is due to a little 'gotcha' called the Lagrange Invariant. It's a
fundamental aspect of first order optics and can ultimately be traced
to the conservation of energy and thermodynamics. The more esoteric
'optics' explanation would be conservation of radiance.
Basically if you reduce the fiber's exit cone angle by a factor of X
with a lens system, the image of the fiber tip will increase in size
(magnification) by the same factor X. Then the angular divergence of
the light from the collimator (that's essentially imaging the fiber
tip to infinity) increases by X as well.
If your fiber tip core is 500 um, then the system that I described
must be scaled by 10x. That's a tall order even for custom optics and
a generous budget.
Good luck in your endeavors.
James Carter
http://www.jacarter3.com
http://www.opticalconsulting.com
>
> Hi James:
>
> 1- If most of the commercial telescopes primary element focal length
> is 1m, we don't necessarliy need an 40 - 50 cm aperture dia to fit in
> 0.22 NA of the fiber. We could reduce this input NA by imaging the
> fiber output with some magification, say 3, this gives 0.22/3 = 0.73
> for input NA into the telescope primary.
>
> Taking your 1m focal length example for the primar, in order to get a
> collimated beam of 5 Cmm we need an input NA of about 0.025 (= 2.5Cm/
> 100 Cm). To achieve this we need to image the fiber output by a
> magnification of
> 8.8 ( = 0.22/0.025 ), this probably could be done with two lenses with
> focal ratio (f2/f1) of 8.8. This is what I meant by modifying input
> optics of a commercial telescope, in case of a Newtonian telescope
> (with a primary of 1m focal length) we replace its eyepeice with this
> imaging optics. This is in theory, the question was if this is
> practical with commercial telescopes and if such telescopes are
> available and can handle 300 W light power.
>
> 2- You are right the fiber is a mutimode fiber ( with a core dia = 500
> um ).
>
> 3- The experiment will be conducted in a closed enviroment for a
> shorter distance (i.e < 1Km) to check the feasibilty.
>
> thanks
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Date: 24 May 2007 08:58:49
From: Farsang
Subject: Re: Commercial Telescope for high Power Beam
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On May 24, 6:08 am, Jamie <jacart...@earthlink.net > wrote:
> With 300 watts at the distal end, the fiber must undoubtedly be
> multimode. In oder to get a 5 cm spot at 1km the output divergence
> must be less than 50 micro-radians, ignoring atmospherics such as
> turbulence. Given a multimode fiber that is 50/125, you will need a
> collimator with an effective focal length of 1m (quite reasonable for
> a commercial telescope primary element) and an aperture of at least 40
> to 50 cm to pass the output cone of the fiber, assumed to have an
> numerical aperture of 0.2 to 0.22, without loss. A commercial
> telescope with an aperture of 16 to 20 inches is quite rare.
>
> You may be able to buy an off-axis parabola (OAP) from SORL (Space
> Optics Research Labs athttp://www.sorl.com/productline/oaps/offaxisparabolas.htm)
> but their catalog listing only goes to 8 inches at 1m focal length. I
> would contact SORL and some other OEM reflective optics vendors for
> capabilities and, if appropriate, quotes.
>
> With an OAP, all you need is the fiber mount (I am assuming a bulkhead
> mating connector), the OAP and mount and a platform to support both of
> these with the proper geometry.
>
> It is also important that you don't light this contraption up anywhere
> that is not a closed range as the potentials for human injury and even
> fire hazards are too great. If you point this into the sky anywhere
> that is not consider closed and monitored air space and without the
> proper clearances, chances are you won't be caught, but if you are,
> the penalties would be dire.
>
> James Carterhttp://www.jacarter3.comhttp://www.opticalconsulting.com
>
> On May 24, 2:22 am, Farsang <youzpal...@netscape.net> wrote:
>
>
>
> > Hi:
>
> > We have a fiber with a 300 Watts output at 900 nm, we'd like to
> > collimate this output and generate a spot of about 5 Cm dia. at 1 Km
> > away. Are there commercial telescopes that we could modify its
> > input optics (to couple in the fiber output) to achieve this and can
> > they handle 300 Watts light power?
>
> > I was thinking of a reflective Newtonian Telescope with its eyepiece
> > replaced by an imaging optics that images the fiber's core onto the
> > focal plane of the telescope primary mirror. This imaging optics
> > would have an appropriate ouput numerical aperture to create a
> > collimated beam of 5 Cm dia. coming out of the the telescope primary
> > mirror. Is this feasible and can the telescope optics handle 300
> > watts ( the primary mirror probably has an enhanced aluminum coating)?
>
> > Alternatively we could collimate the fiber output and send it into a
> > Galilean beam expander (refractive type) but our preference is a
> > commercial telescope (preferably with a tracking capability) that
> > could with some modification give us this 5 Cm output beam.
>
> > thanks for your comments and suggestions.- Hide quoted text -
>
> - Show quoted text -
Hi James:
1- If most of the commercial telescopes primary element focal length
is 1m, we don't necessarliy need an 40 - 50 cm aperture dia to fit in
0.22 NA of the fiber. We could reduce this input NA by imaging the
fiber output with some magification, say 3, this gives 0.22/3 = 0.73
for input NA into the telescope primary.
Taking your 1m focal length example for the primar, in order to get a
collimated beam of 5 Cmm we need an input NA of about 0.025 (= 2.5Cm/
100 Cm). To achieve this we need to image the fiber output by a
magnification of
8.8 ( = 0.22/0.025 ), this probably could be done with two lenses with
focal ratio (f2/f1) of 8.8. This is what I meant by modifying input
optics of a commercial telescope, in case of a Newtonian telescope
(with a primary of 1m focal length) we replace its eyepeice with this
imaging optics. This is in theory, the question was if this is
practical with commercial telescopes and if such telescopes are
available and can handle 300 W light power.
2- You are right the fiber is a mutimode fiber ( with a core dia = 500
um ).
3- The experiment will be conducted in a closed enviroment for a
shorter distance (i.e < 1Km) to check the feasibilty.
thanks
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Date: 24 May 2007 06:08:16
From: Jamie
Subject: Re: Commercial Telescope for high Power Beam
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With 300 watts at the distal end, the fiber must undoubtedly be
multimode. In oder to get a 5 cm spot at 1km the output divergence
must be less than 50 micro-radians, ignoring atmospherics such as
turbulence. Given a multimode fiber that is 50/125, you will need a
collimator with an effective focal length of 1m (quite reasonable for
a commercial telescope primary element) and an aperture of at least 40
to 50 cm to pass the output cone of the fiber, assumed to have an
numerical aperture of 0.2 to 0.22, without loss. A commercial
telescope with an aperture of 16 to 20 inches is quite rare.
You may be able to buy an off-axis parabola (OAP) from SORL (Space
Optics Research Labs at http://www.sorl.com/productline/oaps/offaxisparabolas.htm)
but their catalog listing only goes to 8 inches at 1m focal length. I
would contact SORL and some other OEM reflective optics vendors for
capabilities and, if appropriate, quotes.
With an OAP, all you need is the fiber mount (I am assuming a bulkhead
mating connector), the OAP and mount and a platform to support both of
these with the proper geometry.
It is also important that you don't light this contraption up anywhere
that is not a closed range as the potentials for human injury and even
fire hazards are too great. If you point this into the sky anywhere
that is not consider closed and monitored air space and without the
proper clearances, chances are you won't be caught, but if you are,
the penalties would be dire.
James Carter
http://www.jacarter3.com
http://www.opticalconsulting.com
On May 24, 2:22 am, Farsang <youzpal...@netscape.net > wrote:
> Hi:
>
> We have a fiber with a 300 Watts output at 900 nm, we'd like to
> collimate this output and generate a spot of about 5 Cm dia. at 1 Km
> away. Are there commercial telescopes that we could modify its
> input optics (to couple in the fiber output) to achieve this and can
> they handle 300 Watts light power?
>
> I was thinking of a reflective Newtonian Telescope with its eyepiece
> replaced by an imaging optics that images the fiber's core onto the
> focal plane of the telescope primary mirror. This imaging optics
> would have an appropriate ouput numerical aperture to create a
> collimated beam of 5 Cm dia. coming out of the the telescope primary
> mirror. Is this feasible and can the telescope optics handle 300
> watts ( the primary mirror probably has an enhanced aluminum coating)?
>
> Alternatively we could collimate the fiber output and send it into a
> Galilean beam expander (refractive type) but our preference is a
> commercial telescope (preferably with a tracking capability) that
> could with some modification give us this 5 Cm output beam.
>
> thanks for your comments and suggestions.
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Date: 24 May 2007 11:17:55
From: Roger Hamlett
Subject: Re: Commercial Telescope for high Power Beam
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"Farsang" <youzpalang@netscape.net > wrote in message
news:1179991378.922314.208020@r3g2000prh.googlegroups.com...
> Hi:
>
> We have a fiber with a 300 Watts output at 900 nm, we'd like to
> collimate this output and generate a spot of about 5 Cm dia. at 1 Km
> away. Are there commercial telescopes that we could modify its
> input optics (to couple in the fiber output) to achieve this and can
> they handle 300 Watts light power?
>
> I was thinking of a reflective Newtonian Telescope with its eyepiece
> replaced by an imaging optics that images the fiber's core onto the
> focal plane of the telescope primary mirror. This imaging optics
> would have an appropriate ouput numerical aperture to create a
> collimated beam of 5 Cm dia. coming out of the the telescope primary
> mirror. Is this feasible and can the telescope optics handle 300
> watts ( the primary mirror probably has an enhanced aluminum coating)?
>
> Alternatively we could collimate the fiber output and send it into a
> Galilean beam expander (refractive type) but our preference is a
> commercial telescope (preferably with a tracking capability) that
> could with some modification give us this 5 Cm output beam.
>
> thanks for your comments and suggestions.
There is much more to this than you think...
The actual 'collimation', is _easy_. 5cm, at 1km, is 'only' 12arc seconds.
However the big problem will be the 'seeing'. If you look through a good
rifle site at a target this sort of distance away, on a good day, it'll be
quite easy to see, and stable. However on most days, the actual target,
will be jumping around in the view, as heated air in the path between,
makes it's effects felt. Expert shots, use the image processing in their
brain, to average the target position, and look for the stable
'moments'...
Commercial systems to achieve this sort of spot size, and accuracy, use
adaptive targetting. I was involved in a system some years ago, that put
10KW, into a slightly smaller spot size. The main beam, was accompanied by
two reference beams, that 'scanned' a small distance up/down, and across
respectively, and these carried a phase modulated signal, reflecting their
scan 'position'. At the receive end, a detector picked up how far off the
system was aiming, and sent a control signal back, to adjust the aim of
the source. The whole system detected and adjusted it's aim, at over 1KHz.
At times, the aim was moving several arc minutes from the initial point
(there was a 'shutdown', on the beam, if the system could not correct fast
enough to keep it inside the target). We also had to have reflection
detection at the source, to shutdown the beam, when it went misty, since
otherwise backscatter was dangeroous...
At night, after the air has cooled, or in the very early morning, what you
have in mind will work, but at midday, in most climates, the movement will
be massive. Commercial versions of several scopes have been used for this
type of work (open tube RC's in particular), but normally with optics at
the receiver, that will accept quite large beam shifts.
Best Wishes
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Date: 24 May 2007 03:12:33
From: Richard J Kinch
Subject: Re: Commercial Telescope for high Power Beam
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Farsang writes:
> We have a fiber with a 300 Watts output at 900 nm, we'd like to
> collimate this output and generate a spot of about 5 Cm dia. at 1 Km
> away.
Impossible to say without details on the "fiber".
Consider that focusing a laser to 5 cm at 1 km can be pretty challenging.
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