Re: Acousto optic scanner

Andrew Resnick <[EMAIL PROTECTED]> wrote in message news:<[EMAIL PROTECTED]>...
> In <[EMAIL PROTECTED]> Helpful person 
> wrote:
> > I have an application that requires scanning a laser beam over angles
> > of about +/- 1 degree at a rate of 60Hz.  I am presently using a
> > mechanical scanner.  It is theoretically possible to use an acousto
> > optical device in reflection mode to perform such a scan.  In
> > reflection mode one should be able to steer the laser by adjusting the
> > Bragg planes while maintaining reflectivities of greater than 99%. 
> > However, I have been unable to find an off the shelf device configured
> > for this application.
> 
> You didn't mention the wavelength, but there are to companies I know 
> that make acousto-optical deflectors (transmission):
> 
> http://www.intraaction.com/
> http://www.eopc.com/
> 
> I suspect the diffection efficiency is less than you would like.  A-O 
> systems are generally used for kHz-MHz scanning rates, so maybe A-O 
> devices are not really what you want.  What's wrong with the system you 
> have now?

The wavelenght I am interested in is at the red (or near infra red)
part of the spectrum.  The specific wavelength should not be important
because if such a device exists, it would be a fairly simple task to
change its geometry to accomodate a wavelength change.  A transmission
device is probably not practicle due to the sensitivity of eficiency
with respect to the number of Bragg planes and the refractive index
variation within the device.

A thick hologram using materials such as DCG (dichromated geletin) can
in practice have diffraction efficiency very close to 100%.  This
should be possible to achieve in an acousto optical device where the
refractive index variation would be small with a large number of Bragg
planes.  Unlike a transmission hologram, the thickness of a reflection
hologram is not critical.

AO devices do usually have a higher bandwidth than I need.  However,
this is an advantage, as they should work well at the lower bandwidth
requirement.

I would like a scanner with no moving parts, hence the desire to get
away from a mechanical mirror.