NetNews Usenet Archive 1992 #16/NN_1992_16.iso/spool/sci/physics/12081

Text File | 1992-07-30 | 3.5 KB | 69 lines

Newsgroups: sci.physics
Path: sparky!uunet!cis.ohio-state.edu!zaphod.mps.ohio-state.edu!usc!sol.ctr.columbia.edu!news.unomaha.edu!unlinfo.unl.edu!cbettis
From: [e-mail] (clifford bettis)
Subject: Re: Magnetic lenses
Message-ID: <[e-mail]>
Organization: University of Nebraska - Lincoln
References: <[e-mail]> <[e-mail]> <[e-mail]> <[e-mail]> <[e-mail]>
Distribution: na
Date: Fri, 31 Jul 1992 00:40:08 GMT
Lines: 57

In <[e-mail]> [e-mail] (clifford bettis) writes:

>In <[e-mail]> [e-mail] (Blair P. Houghton) writes:

>>In article <[e-mail]> [e-mail] (clifford bettis) writes:
>>>The optical phase information is lost in the recording
>>>process (i.e. the TV camera only records intensity) and therefore the
>>>information necessary to reconstruct a complete image is missing.

>>What you're trying to say is that an image is made up of a set of
>>points (small regions of acuity), and your poor vision (due to
>>myopia, the inability to focus properly, such that the virtual
>>image is formed in front of the retina instead of on the retina)
>>turns each point into a blob, covering more retinal receptors than
>>it should, overlapping with blob-smear from adjacent points,
>>creating a fuzzy image; and it is not possible to create an
>>arrangement of points which is then made fuzzy by this myopia, such
>>that this fuzzy image actuall forms some clear image on the
>>retina.

>>Is that what you're trying to say?

>>Phase information isn't an issue.

>>>To make a TV capable of such feats the band width of the signal would
>>>have to be on the order of the frequency of light.

>>It's strictly a pixel problem; bandwidth isn't an issue.
>>If Matisse (or was it Manet?) couldn't do it, we can't.

>>                --Blair
>>                  "What am I saying?"
>As far as what is happening on the retina phase information doesn't
>matter (the individual rods and cones respond to intensity; but as far
>as how that information reaches the retina (as a real image) phase
>does matter.  To deblur an out of focus image you need to do a fourier
>transform (in general a fresnel transform); you can think of a lens as
>a analog device for doing spatial fourier transforms of images.  If
>you are missing the phase information you cannot reproduce the real
>image. Would there be another way to selectively turn on the right
>pixels on the retina without using a lens? I can't think of a pratical
>one; but I suppose you are right, if you could do that you could
>transmit visual images to the optically challenged (such as yours
>truly) that contain only intensity information and "look" in focus.
>Cliff Bettis
I need to correct a mistake in my post. One can deblur an out of focus
image without the original phase information if one has the point
transfer function (this is what is being done to the Hubble images).
However my original point I think is correct. To put it another way:
it is not possible to put a distribution of ink on a sheet of paper so
that it looks like an in focus circular spot to a myopic individual without
using a lens between the eye and the spot. If one had direct access to
the retina and could some how excite the rods and cones of the retina
in the pattern of a deblurred image ... or if somehow the brain could
learn how to deconvolve an out of focus image using the point transfer
function..
Cliff Bettis