Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!henry
From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: net.space
Subject: Re: potential space product
Message-ID: <6023@utzoo.UUCP>
Date: Fri, 4-Oct-85 15:37:01 EDT
Article-I.D.: utzoo.6023
Posted: Fri Oct  4 15:37:01 1985
Date-Received: Fri, 4-Oct-85 15:37:01 EDT
References: <3725@mordor.UUCP>
Organization: U of Toronto Zoology
Lines: 21

> [How can one make a lens with continuously-varying index of refraction?...]
> By building it in weightlessness.  The sphere would float in the middle of a
> vacuum chamber.  Glass would be deposited on it one layer at a time, with each
> layer having the appropriate index.  The glass vapor would flow into the
> chamber continuously, and its doping would vary continuously. The
> weightlessness would give perfect spherical symmetry...

One very serious problem that I can see is crystallization, also known to
the glass community as "devitrification".  Glass is an amorphous solid,
essentially an extremely viscous liquid.  But most glass-forming materials
will form crystals as well.  Laying it down from vapor strikes me as a
good way to get a mass of polycrystalline junk rather than smooth glass.
My understanding is that the semiconductor people do *not* lay down glass
from vapor; they oxidize the silicon surface to produce it.

Possibly devitrification can be suppressed by careful control of conditions.
This is the sort of detail that is highly proprietary, so it's hard to say
much without being an insider.  But the problem is serious, perhaps fatal.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry


Brought to you by Super Global Mega Corp .com