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