Taking Pictures with a DRAM Chip

 

DRAM Image

This picture was taken by using a DRAM chip as an image sensor (translated). A decapped 64k DRAM chip was combined with optics that could focus an image onto the die. By reading data out of the DRAM, the image could be constructed.

DRAM is the type of RAM you find on the RAM cards inserted into your motherboard. It consists of a massive array of capacitors and transistors. Each bit requires one transistor and one capacitor, which is quite efficient. The downside is that the memory needs to be refreshed periodically to prevent the capacitors from discharging.

Exposing the capacitor to light causes it to discharge faster. Once it has discharged past a certain threshold, the bit will flip from one to zero. To take a picture, ones are written to every bit in the DRAM array. By timing how long it takes a bit to flip from one to zero, the amount of light exposure can be determined. Since the DRAM is laid out in an array, each bit can be treated as a pixel to reconstruct the image.

Sure, modern CCDs are better, cheaper, and faster, but this hack is a neat way to totally re-purpose a chip. There’s even Turbo Pascal source if you’d like to recreate the project.

Thanks to [svofski] for the tip.

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