Optical Beamformer

I was wondering if it was possible to have an optical beamformer. I
have done a search on Google and found microwave beamformers but no
optical ones.
I thought you might use say 8 lenses and fibre optics to get the
delays.
You would then focus the images together to get the sum (delay and sum
type).
It should give us a type of telescope with optical gain and attenuate
all light to the right or left. Also this could work in reverse but I
am not sure what would happen here. I am assuming this is quite
commonplace in say astronomy?

Tom

Jerry Avins wrote:

> Tom wrote:
> > I was wondering if it was possible to have an optical beamformer. I
> > have done a search on Google and found microwave beamformers but no
> > optical ones.
> > I thought you might use say 8 lenses and fibre optics to get the
> > delays.
> > You would then focus the images together to get the sum (delay and sum
> > type).
> > It should give us a type of telescope with optical gain and attenuate
> > all light to the right or left. Also this could work in reverse but I
> > am not sure what would happen here. I am assuming this is quite
> > commonplace in say astronomy?
> >
> > Tom
> At optical frequencies it's called an interferometer.

I suppose it is Jerry but from I remember of Interferometers they have only
two 'arms' (rather than an array) and don't they normally measure movemement
(vibration etc)?

Tom

Tom wrote:
> I was wondering if it was possible to have an optical beamformer. I
> have done a search on Google and found microwave beamformers but no
> optical ones.
> I thought you might use say 8 lenses and fibre optics to get the
> delays.
> You would then focus the images together to get the sum (delay and sum
> type).
> It should give us a type of telescope with optical gain and attenuate
> all light to the right or left. Also this could work in reverse but I
> am not sure what would happen here. I am assuming this is quite
> commonplace in say astronomy?
> 
> Tom
At optical frequencies it's called an interferometer.

Jerry
-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������

Tom wrote:
> 
> Jerry Avins wrote:
> 
> 
>>Tom wrote:
>>
>>>I was wondering if it was possible to have an optical beamformer. I
>>>have done a search on Google and found microwave beamformers but no
>>>optical ones.
>>>I thought you might use say 8 lenses and fibre optics to get the
>>>delays.
>>>You would then focus the images together to get the sum (delay and sum
>>>type).
>>>It should give us a type of telescope with optical gain and attenuate
>>>all light to the right or left. Also this could work in reverse but I
>>>am not sure what would happen here. I am assuming this is quite
>>>commonplace in say astronomy?
>>>
>>>Tom
>>
>>At optical frequencies it's called an interferometer.
> 
> 
> I suppose it is Jerry but from I remember of Interferometers they have only
> two 'arms' (rather than an array) and don't they normally measure movemement
> (vibration etc)?
> 
> Tom
> 
> 

If I recall correctly, at least one of the proposed Hubble replacements 
is based on getting a bunch of small mirrors to coherently sum.  If you 
look around on the net, I think it would easy to find out more.

I'm  no expert on optical fibre, but I recall that they are (or at least 
  were) dispersive.  You also have an issue  with insertion losses.

There  are of course applications that use fibre bundles, like endoscopes.

Tom <somebody@nOpam.com> wrote in message news:<3F961433.1659333C@nOpam.com>...
> Jerry Avins wrote:
> 
> > Tom wrote:
> > > I was wondering if it was possible to have an optical beamformer. I
> > > have done a search on Google and found microwave beamformers but no
> > > optical ones.
> > > I thought you might use say 8 lenses and fibre optics to get the
> > > delays.
> > > You would then focus the images together to get the sum (delay and sum
> > > type).
> > > It should give us a type of telescope with optical gain and attenuate
> > > all light to the right or left. Also this could work in reverse but I
> > > am not sure what would happen here. I am assuming this is quite
> > > commonplace in say astronomy?
> > >
> > > Tom
> > At optical frequencies it's called an interferometer.
> 
> I suppose it is Jerry but from I remember of Interferometers they have only
> two 'arms' (rather than an array) and don't they normally measure movemement
> (vibration etc)?

I think one important point would be the technology that make the different 
instruments work. I don't know anything about optical interferometers, but 
as far as I know, the wavelengths of the (visible) light is on the order 
500 nm - 900 nm (yes, a gross estimate, I know, but I think the numbers are 
good) which means wave cycles on the order of 1.5e-15 s - 3e-15 s, or said 
in yet another way, the light operates at a frequency on the order of a 
million gigahertz. 

I know there have been some advances in microprocessor technology recently, 
but I wouldn't expect processors capable of handling these types of signals 
by means of "standard technology" to be available during the next few 
months. 

On second thought, wouldn't the delay-and-sum principle implemented by 
means of current optical technology, be just a lens?  

Rune

Hello Tom,
You may want to check out chara (Center for High Angular Resolution
Astronomy) operated by Georgia State University. Details can be found
at:

http://www.chara.gsu.edu/CHARA/

It uses multiple telescopes with their light beams combined after
being passed through optical trombones. When I did my Astronomy
courses there, I got to see a lot of the equipment being fashioned in
the shop before being sent out to Mt. Wilson. I even got to touch one
of the primary mirrors (before polishing and metal overcoating).

You also may wish to look at the Starfire system. Either a guidestar
or a synthetic guidestar (laser) is used to track the turbulance. The
main mirror is actively deformed by piezo transducers.

Clay

p.s. One of the most interesting astronomy courses I took was Binary
Stars where speckle interferometry is used to better "see" the star
systems. We calculated orbital paramters from system observations. The
deployment of Chara promises to allow us to dicern the width of a
nickle at 10000 miles!




Tom <somebody@nOpam.com> wrote in message news:<3F961433.1659333C@nOpam.com>...
> Jerry Avins wrote:
> 
> > Tom wrote:
> > > I was wondering if it was possible to have an optical beamformer. I
> > > have done a search on Google and found microwave beamformers but no
> > > optical ones.
> > > I thought you might use say 8 lenses and fibre optics to get the
> > > delays.
> > > You would then focus the images together to get the sum (delay and sum
> > > type).
> > > It should give us a type of telescope with optical gain and attenuate
> > > all light to the right or left. Also this could work in reverse but I
> > > am not sure what would happen here. I am assuming this is quite
> > > commonplace in say astronomy?
> > >
> > > Tom
> > At optical frequencies it's called an interferometer.
> 
> I suppose it is Jerry but from I remember of Interferometers they have only
> two 'arms' (rather than an array) and don't they normally measure movemement
> (vibration etc)?
> 
> Tom

Tom wrote:

> 
> Jerry Avins wrote:
> 
   ...
>>
>>At optical frequencies it's called an interferometer.
> 
> 
> I suppose it is Jerry but from I remember of Interferometers they have only
> two 'arms' (rather than an array) and don't they normally measure movemement
> (vibration etc)?
> 

I guess you're right. "Interference device" would be better, but it's
not used. A diffraction grating is a frequency-sensitive beamformer with
lots of elements, don't you think? When the spacing is systematically
altered, it becomes a hologram.

Jerry
-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������

allnor@tele.ntnu.no (Rune Allnor) wrote in message news:<f56893ae.0310220628.678e165b@posting.google.com>...
> Tom <somebody@nOpam.com> wrote in message news:<3F961433.1659333C@nOpam.com>...
> > Jerry Avins wrote:
> > 
> > > Tom wrote:
> > > > I was wondering if it was possible to have an optical beamformer. I
> > > > have done a search on Google and found microwave beamformers but no
> > > > optical ones.
> > > > I thought you might use say 8 lenses and fibre optics to get the
> > > > delays.
> > > > You would then focus the images together to get the sum (delay and sum
> > > > type).
> > > > It should give us a type of telescope with optical gain and attenuate
> > > > all light to the right or left. Also this could work in reverse but I
> > > > am not sure what would happen here. I am assuming this is quite
> > > > commonplace in say astronomy?
> > > >
> > > > Tom
> > > At optical frequencies it's called an interferometer.
> > 
> > I suppose it is Jerry but from I remember of Interferometers they have only
> > two 'arms' (rather than an array) and don't they normally measure movemement
> > (vibration etc)?
> 
> I think one important point would be the technology that make the different 
> instruments work. I don't know anything about optical interferometers, but 
> as far as I know, the wavelengths of the (visible) light is on the order 
> 500 nm - 900 nm (yes, a gross estimate, I know, but I think the numbers are 
> good) which means wave cycles on the order of 1.5e-15 s - 3e-15 s, or said 
> in yet another way, the light operates at a frequency on the order of a 
> million gigahertz. 
> 
We just need to use fibre optic cable to get a delay as far as I know.

Tom

"Clay S. Turner" wrote:

> Hello Tom,
> You may want to check out chara (Center for High Angular Resolution
> Astronomy) operated by Georgia State University. Details can be found
> at:
>
> http://www.chara.gsu.edu/CHARA/
>
> It uses multiple telescopes with their light beams combined after
> being passed through optical trombones. When I did my Astronomy
> courses there, I got to see a lot of the equipment being fashioned in
> the shop before being sent out to Mt. Wilson. I even got to touch one
> of the primary mirrors (before polishing and metal overcoating).

That's what I had in mind. Does it work in reverse?

Tom

aberdonian_2000@yahoo.com (Tom) wrote in message news:<e1b1658f.0310221235.1a9b2934@posting.google.com>...
> allnor@tele.ntnu.no (Rune Allnor) wrote in message news:<f56893ae.0310220628.678e165b@posting.google.com>...

> > as far as I know, the wavelengths of the (visible) light is on the order 
> > 500 nm - 900 nm 
...
> We just need to use fibre optic cable to get a delay as far as I know.

You are probably right. The beamformers I know, usually operate on phase 
differences less than a wavelength (actually less than half a wavelength),
so you may find it a bit cumbersome to fine-tune your fibers to within 
a few hundred nanometers... but then, I don't know much about what can 
and can not be done with optics.

Rune