Re: Simple Still Camera components?

On Jul 29, 9:46 pm, Vladimir Vassilevsky <antispam_bo...@xxxxxxxxxxx>
wrote:

Take 4164 in ceramic package. Carefully open the cover so the crystal is
exposed. Project a light image to the crystal. Generate DRAM signals by
a microcontroller. Fill DRAM with ones (or with zeroes - I don't
remember). Switch off refresh for some time. Then read DRAM. You will
get a pretty clear black and white bitmap picture.

Tried that once... harder than it sounds.

Due to the disabling refresh, you can't have the chip in a computer as
memory, but must build your own interface circuit.

Then you also have to play with lenses and get moderately reasonable
image projection at an appropriate power desnity onto the "active"
area of the die even for initial tests. You can't just shine a
flashlight at it and mask off half the cells and expect to see a
difference, because the output transitor when uncovered becomes a
phototransistor - and that may at some light level go for the address
decode logic too.

.

Relevant Pages

  • Poor Mans image sensor; Was: Re: Simple Still Camera components?
    ... Project a light image to the crystal. ... Fill DRAM with ones. ... Do it again with different waiting times (note, once you've read out a pattern, you've lost the charge stored in the cells, you have to start again, you can't read the chip repeatedly without filling it with 1's), combine the resulting bit patterns to get a sort-of grey scale image. ...
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