| From: | David Woods <david@*******.FREESERVE.CO.UK> |
|---|---|
| Subject: | Re: Ultrasound vision |
| Date: | Thu, 4 Feb 1999 18:23:32 +0000 |
>
> Moving along to technology that will be present, and should be present in
> Shadowrun, we have interesting research conducted jointly by Scripp's
> Oceanographic Institute (aka UC San Diego) and the U.S. Navy on "acoustic
> daylight".
>
> These are sensors (using no lenses, I might add, in reference to someone
> who thought it was impossible to make an image without a lens in
> contravariance with linear algebra transmission matrices) that use the
> background ambient sounds in the ocean to "see", in much the same way as
> our eyes use background light.
This method of sonic imaging is obviously possible. A microphone's
(hydrophone) output signal the superposition of the wavefronts
incident on it. The resulting waveform can be deconstructed and
individual
sources isolated. Due to the low speed of sound waves (even in water),
discerning time of arrival differences between sensors would be easy.
Using
just three such sensors it is possible to find the position of any
isolatable source.
It is perfectly feasible that an array of a million such sensors could
provide enough information to build a picture of it's surroundings.
However,
we were discussing light and light is very different from sound.
To use the same signal processing techniques you would need a detector
capable of outputting the superposition of light waves incident apon it
(petaHz+ response). You would then need to read out the resulting
waveform
into your processor. This is Star Trek technology and it is not
plausible.
Photodetectors provide an rms amplitude, integrated over a very long
(compared to light frequencies) time period. If the passive sonar
described
above had to use microphones only capable of giving a rms amplitude over
a 2
second period, no image could be derived. No matter how clever your
processor, the information is degenerate and any number of 'scenes'
could
give rise to the same response.
You will have to propose a plausible method by which a detector array,
without a mirror or a lens, can image a scene using light. You have not
done
this yet. Good luck.
Regards
- David Woods
