HDTenEightyP/NetNews huggingface dataset:
From: schumach@convex.com (Richard A. Schumacher)
Subject: Re: Do I want flat-field binoculars?
Organization: CONVEX Computer Corporation, Richardson, Tx., USA
Date: Sat, 23 Jan 1993 19:26:36 GMT
X-Disclaimer: This message was written by a user at CONVEX Computer
              Corp. The opinions expressed are those of the user and
              not necessarily those of CONVEX.

"Flatness of field" in binocs has nothing to do with distance to
the subject. (Would that it did! Astronomical use would be much
easier...) It has to do with whether
focus is maintained across the field of view. And do not
confuse "flatness of field" with "depth of field", as did a previous
poster.

By all means, try and compare before buying,
Newsgroups: sci.optics,rec.boats
From: zpope@osf.org (William Pope)
Subject: Re: Do I want flat-field binoculars?
Reply-To: zpope@osf.org
Organization: Open Software Foundation
Date: Fri, 22 Jan 1993 16:41:42 GMT


In article <1993Jan21.205839.6212@nynexst.com> rsilvers@cirrus.nynexst.com (Robert Silvers) writes:

>	   I need to decide between two Fujinon binoculars.  They
>   are identical in quality, but one has more eye relief and is
>   of flat-field design.  The flat-field ones cost more, $500 instead
>   of $400.  I understand what this means, but aren't most camera
>   lenses curved field?  (except for copy-stand cameras?)  Is this
>   something I should care about?  

Try them.  I prefer the non-flat field and I do wear glasses.  Go to the
store take them (and a salesman) outside and try them.  If the store won't
let you do this go somewhere else.

=bill
--
============================================================================
William Z. Pope                                     Phone: +1 (617) 621-8889 
Open Software Foundation                              Fax: +1 (617) 621-0584
11 Cambridge Center                                     Email: zpope@osf.org
Cambridge, MA  02142                             OSF DME Integration Project
From: mcdonald@aries.scs.uiuc.edu (J. D. McDonald)
Newsgroups: sci.optics
Subject: Re: Use of Thorium Oxide in lenses ??
Date: 24 Jan 93 18:50:47 GMT
Organization: UIUC SCS

In article <1993Jan24.175205.5263@ultb.isc.rit.edu> dxa8439@ultb.isc.rit.edu (D.X. Axelrad) writes:
>From: dxa8439@ultb.isc.rit.edu (D.X. Axelrad)
>Subject: Use of Thorium Oxide in lenses ??
>Date: Sun, 24 Jan 1993 17:52:05 GMT
>A friend of mine recently brought something interesting to my attention.
>He has found several common point and shoot cameras which displayed
>unusually high levels of radioactivity.  The cause of this was
>determined to be Thorium Oxide which seems present only in the lens.
>
>Does anyone know why this isotope might be used?  Would the Thorium
>Oxide be integrated into the glass its self, or be used as a coating?
>Does anyone know of anyother instances of radioactive materials being
>used in commercially available lenes/cameras?
>

The older Schott Glass catalogs has a special column in them that
had "Th" in it if the glass had Thorium Oxide in it. Many rare earth
glases did. Then, recently, those glasses disappeared from the catalog,
apparently done in by OSHA (in the US). They or similar ones must
still exist in Japan or other oriental camera making countries. It was
in the glass itself. These glasses looked, on the "usual suspect" charts,
to be quite valuble (optically speaking that is, not to mention the
sometimes astronomical prices.) I've personally never bought a lens
(i.e. a single custom lens for my laser system) from such a glass.

And yes, Thorium Oxide as well as Thorium Fluoride are used in lens
coatings, though mostly in "hard" coatings for laser purposes.

Why? Inside glass, it would be used to change the relationship between
index of refraction and dispersion. 

As a coating, ThO2 has a moderately high index of refraction and
a good wide spectral bandpass in the visible and UV, and is often
used along with Al2O3, SiO2, and ZrO2 in hard coatings. ThF4 has a
much higher index than other fluorides (except lead fluoride, which is
seriously water soluble) and goes far into the IR. It's great used
on ZnSe. Or as a protective overcoat for silver.

Doug McDonald
Newsgroups: sci.optics
From: sprent@sol.surv.utas.edu.au (Tony Sprent)
Subject: Re: Looking for REFLECTIVE liquid..(like mercury,but..)
Organization: University of Tasmania
Date: Thu, 28 Jan 1993 04:30:03 GMT

In article <1993Jan22.164917.25317@netcom.com>, ccat@netcom.com (Chris Beaumont) writes:
> 
> I'm looking for a reflective liquid,like mercury,but hopefully nontoxic.
> Perhaps a extremely high density solvent might do the trick...or
> a mylar film over water...
> Or is there a way to dye water silver....(!?)  or maybye a way to coat water
> with a film that wouldn't mix with it..
> Chris


You might like to investigate the use of Woods Metal. This is a low melting 
point metal alloy with a silvery surface. It has a melting point of 70C and 
is used for various purposes - fusable links etc. It has a composition of
   Bismuth  50%
   Lead					25%
   Tin      12.5%
   Cadmium  12.5%

It is certainly less toxic than mercury but I have no idea of its refective
quality.

You don't mention what your application is. Maybe you could use the same trick 
that early surveyors in Australia had as a reflective liquid surface. They 
used a pannikin of tea as an artificial horizon to reflect an image of the sun
which they then viewed together with the real sun through a sextant. 
They used this for determining latitude and longitude during exploration.
(I suppose that beer would work just as well though I am not sure whether the
 bubbles would cause a systematic angular shift. Drinking it would!)

 ________________________________________________________
| Tony Sprent                                             |
| Department of Surveying and Spatial Information Science | 
| University of Tasmania                                  |     
| GPO Box 252C Hobart        _--_|\                       |
| Tasmania*                 /      \                      |
| Australia   7001          \_.--._/   )                  |
|                                 *   /                   |
| Phone 61-02-202110 Fax 61-02-240282  International      |
|         002-202110       002-240282  Australia          |
| email  sprent@surv.utas.edu.au                          |
|_________________________________________________________|
From: hnr@ecs.soton.ac.uk (Harvey Rutt)
Newsgroups: sci.optics
Subject: Re: Optical computing
Keywords: Optical Computing
Date: 21 Jan 93 16:03:27 GMT

I wonder when it will sink in that statements re fibre optics and
optical computing such as 

"An optical computer uses the basic unit of light, called a photon,
instead of electrons. Photons move at 10 times the speed of
electrons,"

are complete rubbish and irrelevant. Its not the speed of the electron
that matters (its a lot less than c/10!) but the speed of the e/m wave
- as it is for light!

The velocity of propagation in fibre & coax are very similar!

The non-interaction, bandwidth & image parallelism are of course for
real - if they can be effectively used & interfaced to the outside
world.


Turning from fact to opinion, I personally do not believe it is
remotely likely that we will see  'an optical 486' ie general purposae
optical computing, in the forseeable future. On the other hand there
*do* appear to be niche areas, especially in massively parallel, image
processing etc where the optical computer may find a use, so I would
not agree with consigning it all to alt.media.hype
Have *you* never hyped you idea to boost the funding...???

Harvey Rutt
Southampton UK
Newsgroups: sci.optics
From: archana@hkusub (The HK Connection)
Subject: Pulse lasers for HOlography ?
Organization: The University of Hong Kong
X-Newsreader: TIN [version 1.1 PL6]
Date: Tue, 26 Jan 1993 04:12:57 GMT




We are looking to buy a pulsed laser system for dynamic holographic
interferometry. If any one is using such a system or knows of one can
you send me some info. The places that w know of as of now are Lumonics
In Canada and a local chinese manufacturer. I will compile a list if
there is sufficient feedback
Thanks




$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
$$$$$                                                                   $$$$$$$
$$$$$ Dr. Anand Asundi           <<..>>	email: archana@hkusub.hku.hk    $$$$$$$
$$$$$ Department of Mechanical Engineering	archana@hkuxa.hku.hk    $$$$$$$
$$$$$ Haking Wong Rm 7-22			aasundi@hkumea.bitnet   $$$$$$$
$$$$$ Pokfulam Road				archana@hkucc.bitnet	$$$$$$$
$$$$$ The University of Hong Kong		Tel:8592638		$$$$$$$
$$$$$ Hong Kong					fax:8585415		$$$$$$$
$$$$$									$$$$$$$	
$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
Newsgroups: sci.optics
From: samw@colorado.edu (Sam Weaver)
Subject: Re: Projection Based Holography?
Organization: University of Colorado, Boulder
Date: 21 Jan 93 15:38:43

In article <64j3v!h@rpi.edu> mortea@rs6304.ecs.rpi.edu 
(Alan O. Mortensen) writes:

   I have been looking for information on projection based holograms for some
   time.  I know Disney has been working on it, as has MIT, but I cannot find
   any information on it outside of who's doing it.  I was hoping someone from
   this group could help. I'll take about anything, a lead, a press release, 
   or in the best case a public research paper or book.  

   Please respond, this is getting very fustrating.


In the Journal of the Optical Society of America, Vol. 9, No. 11, Nov.
1992, pp. 1969-1977 is an article titled _Synthetic aperture
holography: a novel approach to three-dimensional displays_ by
Hilaire, Benton, and Lucente.  This work is from the MIT Spatial
Imaging Group in the MIT Media Laboratory.  It has 20 references, some
of which will give you further infomation on real-time holographic
display.  

Sam Weaver 
samw@boulder.colorado.edu


--
Newsgroups: sci.optics
From: ccat@netcom.com (Chris Beaumont)
Subject: Looking for REFLECTIVE liquid..(like mercury,but..)
Organization: Netcom - Online Communication Services (408 241-9760 guest)
Date: Fri, 22 Jan 1993 16:49:17 GMT

I'm looking for a reflective liquid,like mercury,but hopefully nontoxic.
Perhaps a extremely high density solvent might do the trick...or
a mylar film over water...
Or is there a way to dye water silver....(!?)  or maybye a way to coat water
with a film that wouldn't mix with it..
Chris
ccat@netcom.com

-- 
__
 "I guess that's what happens when you let Puritans found their own country."
From: dxa8439@ultb.isc.rit.edu (D.X. Axelrad)
Newsgroups: sci.optics
Subject: Use of Thorium Oxide in lenses ??
Date: 24 Jan 93 17:52:05 GMT
Organization: Rochester Institute of Technology

A friend of mine recently brought something interesting to my attention.
He has found several common point and shoot cameras which displayed
unusually high levels of radioactivity.  The cause of this was
determined to be Thorium Oxide which seems present only in the lens.

Does anyone know why this isotope might be used?  Would the Thorium
Oxide be integrated into the glass its self, or be used as a coating?
Does anyone know of anyother instances of radioactive materials being
used in commercially available lenes/cameras?

Thanks, 
Dan    :)


<><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
<>           Dan Axelrad           <> Rochester Institute of Technology <>
<> IN%"dxa8439@ritvax.isc.rit.edu" <>      Imaging and Photographic     <> 
<>       " Why ????????? "         <>         Technology Program        <>
<><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
From: hnr@ecs.soton.ac.uk (Harvey Rutt)
Newsgroups: sci.optics
Subject: Re: Looking for REFLECTIVE liquid..(like mercury,but..)
Date: 27 Jan 93 15:49:04 GMT

In <1993Jan22.164917.25317@netcom.com> ccat@netcom.com (Chris Beaumont) writes:

>I'm looking for a reflective liquid,like mercury,but hopefully nontoxic.
>Perhaps a extremely high density solvent might do the trick...or
>a mylar film over water...
>Or is there a way to dye water silver....(!?)  or maybye a way to coat water
>with a film that wouldn't mix with it..
>Chris
>ccat@netcom.com

>-- 
>__
Gallium melts at 29.8 C. Its not very toxic anyway, and has negilable
vapour pressure.
If 29.8 wont do there are In-Ga and Sn-Ga eutectics which melt lower,
& a ternary Ga-Sn-In mix melts arround 11C if I remember correctly.
Ga is expensive, so a problem if you want a lot.
The mix (& Ga itself) do tend to wet things easily, & you might need
to keep it under N2 to prevent an oxide film dulling it.
I used these as a non-toxic liquid metallic conductor some years back.
Harvey Rutt
Southampton UK
From: kwdelon@snll-arpagw.llnl.gov (delong kenneth w)
Newsgroups: sci.optics
Subject: Re: Optical computing
Summary: A real live optical computer exists
Keywords: optical computing
Date: 20 Jan 93 19:00:30 GMT
Expires: 31 Dec 69 23:59:59 GMT
Distribution: na
Organization: Sandia National Laboratories

My opinion was also that optical computers were a boondoggle, having
worked in the field myself.  However, I just got back from the SPIE
conference in LA, and I saw a talk where a working optical computer
was *demonstrated* executing the SPARC RISC instruction set.  This
preliminary model was operating in a burst mode, where a bunch of
microcode was downloaded to the high speed memory on the optical
processor, and then let the thing run.  Speeds were tremendous, I
forget how fast, but way faster than equivalent execution on a 
SPARC silicon-based machine.  I won't say anything more for fear of
screwing up the details, but I'll give you the company's name:

OptiComp Corp., somewhere in Colorado, contact Peter Guilfoyle.

Ken Delong
Sandia Natl Labs
Newsgroups: sci.optics
From: bauer@informatik.uni-ulm.de (Christian Bauer)
Subject: Re: Optical computing
Followup-To: sci.optics
Organization: University of Ulm
Date: Tue, 26 Jan 93 13:04:55 GMT

In article <1993Jan21.064547.22468@Princeton.EDU>,
ajackson@ernie.Princeton.EDU (Andrew William Jackson) wrote:
> 
> In article <1993Jan20.210811.26931@EE.Stanford.EDU> siegman@EE.Stanford.EDU (Anthony E. Siegman) writes:
> >> >		[ much deleted ]
> >   To respond to a slightly different thread, not only did big
> >companies like IBM, Dec and Intel decide not to pursue digital optical
> >computing, but there's been little interest from small or venture
> >capital firms either -- no digital optical Apple's, or Microsofts, or
> >similar startups appearing out of any garages either.
> >
> 
> Excellent observation!  There are no high-tech startups because there is no 
> useful optical computing technology now in existance - useful meaning faster 
> or cheaper or in any way better (besides cooler and newer) than semiconductor 
> based computing.
> ajackson@ernie.princeton.edu
perhaps development will arrive through the backdoor. IBM is about in
realizing an optical bus which will have parts of it in optical elements.
If it is not a misleading roumor perhaps in some years an FDDI
chipset will have an optical arbiter to achieve 1GBit throughput.
And if it is not a revolution this startpoint can mark the beginning
of an evolution in optical computing. (I know a receiver is far from
being a real computer but who knows sometimes the differences will 
vanish).

Just an opinion

BTW does anyone no the optical specification of SCSI 3?

bauer@informatik.uni-ulm.de
Newsgroups: sci.optics,rec.boats
From: dpbsmith@world.std.com (Daniel P. B. Smith)
Subject: Re: Do I want flat-field binoculars?
Organization: The World Public Access UNIX, Brookline, MA
Date: Sat, 23 Jan 1993 14:56:22 GMT

You must try them.  You MUST try them.  You must TRY them.

Binoculars, like many other products (perhaps all) can't be accurately
and succinctly characterized by a marketeer's catalog description.  It's
an easy trap to fall into.  I find myself falling into it myself all
the time.  Don't buy any binoculars you haven't tried, and try HARD to
make good comparisons between the models you're really interested in.
Buying a pair of binoculars you haven't tried would be a FAR worse
mistake than picking the wrong "features."

Here's my GUESS as to what "flat-field" means.  It probably means that
if something is in focus in the center of the field, and you swing the
binoculars a bit so it's at the edge of the field, it has less of a
tendency to go out of focus.  (At binocular distances, over binocular
fields of view, I don't believe there's any meaningful difference between
a truly flat surface at 100 meters and a spherical surface of 100 meter
radius centered on the viewer!).

In practice, desirable features don't just add, they always trade off.
For example, the "flat field" design might have more lenses in it, which
would explain the extra cost.  But more lenses would mean more light loss
and flare.  It's also possible that the flat field design would somehow
appear less sharp or crisp in the CENTER, when compared side-by-side with
the non-flat.

When we went shopping for binoculars, a LONG time ago, we were absolutely
astonished at the lack of correlation between what we saw and price, type,
maker, or product line.  We were ready to buy some $250 ultracompact
binoculars, even though we didn't want to pay for compactness, because
they just plain had a better image than the $100 models we were looking at...
then we found a $100 non-compact model that was just fine.  The funny
thing was that the $100 model, which happened to be a 9X magnification,
was terrific, but similarly priced, similarly "featured" 7X models from
the same manufacturer were not so hot.

I wear glasses but I don't have much astigmatism.  I don't like high
eye relief models because I find that you have to get your eyes in just
the RIGHT place behind the eyepiece; and they're STILL not good enough to
clear my eyeglass lenses; and I like to have eyecups screening my eyes
from the side.  So I take off my glasses when I use binoculars and one
of the things I look for is convenient diopter adjustments that fit MY
eyes.  My eyes are pretty far apart, and some binoculars don't feel as if
their interpupillary wants to get set quite that far.  The point is that
I could NEVER find that out from a description!



-- 
Daniel P. B. Smith
dpbsmith@world.std.com
Newsgroups: sci.optics,rec.boats
From: dont@StarConn.com (Don Tuite)
Subject: Re: Do I want flat-field binoculars?
Followup-To: rec.boats 
Summary: REI monocular 
Organization: Starnet-Public Access UNIX--Los Altos, CA  415-949-3133
Date: Sat, 23 Jan 1993 22:12:52 GMT

Try the monocular at REI.  Minolta, I think.

Don Tuite
Newsgroups: sci.optics
From: monkey@quip.eecs.umich.edu (Monkey King)
Subject: Commercial camera optics quality?
Organization: University of Michigan EECS Dept., Ann Arbor, MI
Date: Mon, 25 Jan 1993 05:34:43 GMT

I have a question regarding commercial optics -- those found in Nikon, Canon,
etc, cameras.  What are the general specs for surface figure and flatness?
As a comparison, a laser optic, say a mirror substrate from CVI, may have
10-5 (scratch-dig) and lambda/10 @ 633 nm, and sell for a few tens of dollars
for 1" dia.

-- 
Monkey King                 | This message printed on 
monkey@engin.umich.edu      | recycled material.
Newsgroups: sci.optics
From: mcdonald@aries.scs.uiuc.edu (J. D. McDonald)
Subject: Re: Looking for REFLECTIVE liquid..(like mercury,but..)
Organization: UIUC SCS
Date: Mon, 25 Jan 1993 17:22:40 GMT

In article <mancini-250193111953@usx221.fysik.uu.se> mancini@fysik.uu.se (Derrick C. Mancini) writes:
>From: mancini@fysik.uu.se (Derrick C. Mancini)
>Subject: Re: Looking for REFLECTIVE liquid..(like mercury,but..)
>Date: 25 Jan 93 10:24:57 GMT
>In article <1993Jan23.213030.17788@Princeton.EDU>,
>ajackson@ernie.Princeton.EDU (Andrew William Jackson) wrote:
>> 
>> In article <1993Jan22.164917.25317@netcom.com> ccat@netcom.com (Chris Beaumont) writes:
>> >I'm looking for a reflective liquid,like mercury,but hopefully nontoxic.
>
>Gallium or Indium or Tin are possible, since their melting points
>are relatively low.  You would have to keep your mirror hot, though!
>Tin would be pretty much non-toxic I think.  But the vapor of any
>metal would be bad to inhale.
>

Indium and gallium are good because they have very low vapor pressures,
reducing the poison problem. Both of these metals must be somewhat
toxic, but I doubt that that has been investigated very much as
they are rather uncommon (except in the semiconductor industry of
course, where they are used in compounds that most certainly are 
really nasty.)

But both tend to form non-adherent scaly films in air.

Also, you might note that alloys of sodium and potassium can be liquid
at room termerature, and have high reflectivity. :-) due to the
obvious reactivity problems.


Doug McDonald
Newsgroups: sci.optics
From: ajackson@ernie.Princeton.EDU (Andrew William Jackson)
Subject: Re: Looking for REFLECTIVE liquid..(like mercury,but..)
Originator: news@nimaster
Organization: Princeton University
Date: Sat, 23 Jan 1993 21:30:30 GMT

In article <1993Jan22.164917.25317@netcom.com> ccat@netcom.com (Chris Beaumont) writes:
>I'm looking for a reflective liquid,like mercury,but hopefully nontoxic.
>Perhaps a extremely high density solvent might do the trick...or
>a mylar film over water...
>Or is there a way to dye water silver....(!?)  or maybye a way to coat water
>with a film that wouldn't mix with it..
>Chris
>ccat@netcom.com
>


Mercury has been sucessfully used to make parabolic surfaces for telescope
mirrors.  I seem to remember they used a flat mirror(s) to look at
places in the sky other than straigt up.  I do not think you will find
anything better.  I am not sure what you want to do, but maybe you could just 
dye some water a very dark color and put it in a pan painted black on the
inside.  I don't think this would make a very good telescope mirror though.

ajackson@ernie.princeton.edu

Newsgroups: sci.optics
From: mortea@rs6304.ecs.rpi.edu (Alan O. Mortensen)
Subject: Projection Based Holography?
Keywords: computers, the future
Reply-To: mortea@rpi.edu
Organization: Rensselaer Polytechnic Institute, Troy, NY.
Date: Thu, 21 Jan 1993 18:36:00 GMT

I have been looking for information on projection based holograms for some
time.  I know Disney has been working on it, as has MIT, but I cannot find
any information on it outside of who's doing it.  I was hoping someone from
this group could help. I'll take about anything, a lead, a press release, 
or in the best case a public research paper or book.  

Please respond, this is getting very fustrating.


******************************************************************************
(no sig, just a line)