From:	Adam Getchell <acgetchell@*******.EDU>
Subject:	Re: Ultrasound vision
Date:	Thu, 4 Feb 1999 11:44:33 -0800

>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.

Well, you'll have to read the paper then. I'm working on research that does
diffuse realtime imaging of the body using far IR. This is essentially the
same problem as reconstructing the temperature distribution (spatial and
temporal) of a candle on one side of a metal bar, given the temperature
distribution of the other end.

Since it is a diffuse source, the "lens" is linear algebra translation
matrices (which is how lenses are treated in optics texts). I suggest
"Introduction to Optics and Optical Imaging" by Craig Scott. Of particular
relevance to the discussion is Chapter 14, "A Sampling of Optical
Information Processing Systems Based on Fourier Plane Filtering". The
optical Fourier transform mentioned replaces the sequence of delta
functions in the mathematical transform with a finite grid of spots.
Processing time would be incredible compared to FFT algorithms.

With good results and proper computer programming this stands the chance of
replacing X-rays mammography as a realtime imaging tool without the
drawbacks of ionizing radiation.

So yes, realtime diffuse imagery (a step harder than what you were talking
about) using light without a lens is possible and practical. The technique
would obviously have implications elsewhere.

When I get unburied again, I think Ultrasound II would be an interesting
output of all this physics. ;-)

>Regards
>
>- David Woods

--Adam

acgetchell@*******.edu
"Invincibility is in oneself, vulnerability in the opponent." --Sun Tzu