[Laser] Non-Imaging Optics

[Thomas Upton]

Reference below:

1) unwanted wavelengths - unwanted by whom?  One apparatus can be used for a variety of
frequencies, rather than changing out filters, etc.

2) Filtering - yes, to deal with noise one must increase the filtering to the precise
frequency desired.

3) Lens focussing is distinct from IR to UV.  Though small, it is measurable and when the
target is a small semiconductor (smaller the better  for increased bandwidth) it is
significant.  Use of a tubular conical mirrored surface, with the radiation entering at the
larger end, and exiting at the smaller end onto the target, could be experimented with for
our amateur purposes.

4) Convex mirrors were only included for the "golly!" factor.  Golly!

B^)  Tom Upton  AD6N

J. Forster wrote:

> Thomas Upton wrote:
>
> > Mentioning again that there is no power loss when the optical filter is a diffraction
> > grating tilted to the frequency desired.  "You want red, you get red", but the rest
> > of the visible or invisible spectrum is still there in a spectrograph within the
> > collector.
>
> True, but the unwanted wavelengths are blocked by the exit slit.
>
> > So other wavelengths should be recovered by putting their particular  receiving
> > element at that portion of the "rainbow" created by the diffraction grating.
>
> True, but you are not proposing wavelength division multiplex. This is a simple link, and
> any wavelengths that are not transmitted are noise. That noise can be eliminated by
> proper selection of  receive filter bandwidth and center frequency.
>
> > When the collecting element is a concave mirror, there is no difference in the focal
> > distance of wavelengths.  Unlike lenses, which bend different wavelengths in
> > proportion to the interaction of the lens and the medium in which it resides.
>
> The wavelength dependence of lenses is usually to small to matter.
>
> > Incidentally, when the collecting element is a convex mirror, the light can become
> > polarized when the mirror is convex in one direction and not in another.  For
> > example, note the light off of a windshield; the sunlight is polarized because it is
> > convex in one plane and not in the other.
>
> Convex mirrors do not 'collect' light. Light can become partly polarized by a perfectly
> flat mirror.
>
> > When that windshield light comes down a dark corridor onto a wall at the end of the
> > corridor, you can see the heat rising off of your hand or a cup of coffee, as well as
> > the cold rising from other sources.  You can even see your own breath, or the
> > moisture rising from your hand.  Very Interesting!
>
> This has nothing to do with polarization. Warm air has a different index of refraction
> than cool air. The effect is called 'seeing' and has to to do with refraction by pockets
> of air of different indexes.-John
>
> > .
> > Tom Upton  AD6N
> >
> > J. Forster wrote:
> >
> > > Bob Williams wrote:
> > >
> > > >Has anybody tried using just a light-bucket approach for receiving diffuse light
> > > from atmospheric scattering - forward scatter, cloudbounce, etc...?
> > >
> > > >With images on the horizon, I think that light interference might make it
> > > pointless.
> > >
> > > You can eliminate much of the interference with a narrow band optical filter on
> > > your receiver, tuned to your transmitter's wavelength.
> > >
> > > -John
> > >
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