Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!ucsd!ogccse!blake!wiml
From: wiml@blake.acs.washington.edu (William Lewis)
Newsgroups: sci.electronics
Subject: Re: Batty monitors and cheap video
Summary: Cheap video, mostly
Message-ID: <3863@blake.acs.washington.edu>
Date: 30 Sep 89 05:15:25 GMT
References: <1989Sep28.122217.26867@watcsc.waterloo.edu> <57732@psuecl.bitnet>
Reply-To: wiml@blake.acs.washington.edu (William Lewis)
Distribution: sci.electronics
Organization: University of Washington, Seattle
Lines: 50

In article <57732@psuecl.bitnet> peg@psuecl.bitnet writes:
>> Now, regarding a cheap lo-rez video input, a mech eng friend of mine once
>> told me of this thing called a RAMera....
>
>Yes, and you can see why he is an ME, can't you?  ;-)
>
>> First of all, take a 4kX1 bit DRAM and somehow expose the silicon.  I suppsose
>> you could pop the top of  an old ceramic or plane the top layer off a plastic.
>
>Do you have a clean room handy? :-)
>
>> To use the thing as a camera, just charge up the thing to all 1's, wait for a
>> bit, and then check which bits are discharged by the ambient light.
>
>Well, this actually works, in a manner of speaking.  The devices are called
>CCD's, charged coupled devices, and are used for picture tubes in most
>camcorders and video cameras.  As for making one from an actual RAM, I
>seriously, seriously, seriously doubt that you can get ANYTHING useful by
>opening up a RAM chip, but you are welcome to try.

   Nope, RAM chips work, and are cheaper. Less sensitive, no doubt, but
for normal room lighting it works. I described this to the
original asker of the question, but since it has sprung up in public here,
I may as well post...

   Micron Technology used to, and hopefully still does, market the IS32
Optic Ram. This is a normal 32k RAM chip packaged with a quartz window like
an EPROM. This has two rows of 256x512 cells apiece, with a dead zone
down the middle, but the rectangles are perfectly fine for image sensing.
The address & data lines need to be `descrambled' because the cells aren't
arranged "normally" inside the chip, but this isn't hard. This chip
was the basis of the Oct/Nov '83 Circuit Cellar project (BYTE magazine)
and I would guess the heart of the commercial product called the "Microneye".

   I *have* heard several places that merely popping the top off a RAM
chip (dynamic of course -- the refresh line is your `shutter') will
work, although I would put something across the opening before
imaging seascapes.... 

   The advantages of this (as I originally said in email) are that it's
small, cheap, low power and already a completely digital signal. The
chief disadvantage seems to be that it's slow; each exposure is
black&white (not black-gray-white), so for grayscales you need to make
several exposures and hope the scene doesn't change. And Micron Tech. may
not still be around. Does anyone know? 

   --- phelliax

-- 
wiml@blake.acs.washington.edu        (206)526-5885      Seattle, Washington