Monday, November 26, 2012
DIY X-ray backscatter imaging system (airport body scanner)
I built an X-ray backscatter imaging system from parts found on eBay. This system works by scanning a very thin beam of X-rays across the target, and measures the amount of backscatter for a given beam position. The beam is scanned mechanically by a rotating chopper (collimator) wheel, and by tilting the rotating wheel on an orthogonal axis. The output image is generated on an oscilloscope by matching the horizontal scan speed to the rotating wheel, and using a potentiometer to measure the vertical axis position. The scope's brightness (z axis) is controlled by the amount of backscatter signal received by a large-area detector. Thus, the image is constructed bit by bit. I used a long-exposure shutter on my camera to see the image formed by the moving oscilloscope trace.