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.

DIY TSA Backscatter Body Scanner

[Ben Krasnow] built his own version of the TSA’s body scanner. The device works by firing a beam of x-rays at at target. Some of the beam will go through the target, some will be absorbed by the target, and some will reflect back. These reflected x-rays are called ‘backscatter‘, and they are captured to create an image.

In [Ben]’s setup a rotating disk focuses x-rays into beams that travel in arcs across the X-axis. The disk is moved along the Y-axis to fill in the scan. On the disk assembly, there is a potentometer to measure the y-axis position of the beam, and an optical sensor to trigger an oscilloscope, aligning the left and right sides of the image. Using these two sensors, the scope can reconstruct an X-Y plot of the scan.

To detect the x-rays, a phosphorous screen turns the backscattered x-rays into visible light, and a photo-multiplier amplifies the light source. A simple amplifier circuit connects the photo-multiplier to a scope, controlling the brightness at each point.

The result is very similar to the TSA version, and [Ben] managed to learn a lot about the system from a patent. This isn’t the first body scanner we’ve seen though: [Jeri Ellsworth] built a microwave version a couple years ago.

The impressive build does a great job of teaching the fundamentals of backscatter imaging. [Ben] will be talking about the project at EHSM, which you should check out if you’re in Berlin from December 28th to the 30th. After the break, watch [Ben]’s machine scan a turkey in a Christmas sweater.

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Poor man’s thermographic camera

thermographic camera

Using an IR thermometer, there are two ways to go about building a thermographic camera. The first uses a pan and tilt head. Scan lines are emulated, as a computer controls panning from left to right, taking a temperature sample from each step. Vertical resolution is accomplished by tilting. Another method uses a web cam attached to the thermometer. The thermometer’s laser pointer is captured with temperature annotations, as the computer records the field of view. We think the best outcome can be found with a combination of both methods. The video embedded below demonstrates the results. This would be a good addition to the Autonomous paintball sentry.

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