Pixel By Pixel: Experiments In Thermal Imaging

This week in Pixel By Pixel we were asked to embark on a project inspired by light phenomena observed on our recent trip to the New York Hall of Science.  As such, I decided to take the museum's thermal camera a step further, and actually create a thermal pixel grid, seen above.  The grid (in theory) would use peltier junctions behind an insulated grid of copper tiles, which one could then heat individually using a microcontroller.

The paper "canvas" frame

Unfortunately, the project had challenges from the outset.  The first was in the initial concept itself:  Once I started testing the copper tiles with the peltier junctions, I discovered that something about the copper tiles, probably reflectivity, caused them to be invisible to the thermal camera.  I tried aluminum as an alternative, and had the same effect.  However, when I used paper, all seemed well, so that was my new solution.

 The four transistors of the circuit

I created a frame for the paper canvas, and then endeavored to complete the full circuit required to power the four peltier junctions.  This was achieved by creating a circuit consisting of four transistors and an external power source.  The power source was required to adequately heat the junctions, and the transistors were used to control the power source's path to each junction.

The fully wired canvas/box

Once the circuit was complete, I mounted it (and the four peltier junctions) to the back of the canvas/box, thus enabling the entire unit to stand largely on its own, with the only outgoing connections being to a power source and the microcontroller.

Once this was complete, I began to test the unit using test patterns, and then the true problem arose:  the peltier junctions function smoothly for 20-30 seconds, but as they begin to retain heat, they begin to lose their ability to turn "off" as pixels, and they simply become a grid of pixels stuck in the "on" position. What's more, the thermal camera itself creates recurring (and irritating) scan lines.  These effects can be seen (along with ITP in-lab antics) in the video grab from the thermal camera above. 

While the end result was ultimately a disappointment, the endeavor was not.  The idea still seems feasible, even if peltier junctions are maybe not the appropriate solution.  What's more, before the pixels fail, one gets a general conception of the idea trying to be achieved, and it's actually quite visually pleasing.  What's more, I feel that the addition of a color camera could further the project to an even greater extent.  Put simply: there are still many aspects to explore.