[Ben Krasnow] is quite possibly the only hacker with a Scanning Electron Microscope (SEM) collection. He’s acquired a JEOL JSM-T200, which was hot stuff back in the early 1980’s. [Ben] got a great deal, too. He only had to pay shipping from Sweden to his garage. The SEM was actually dropped during shipment, but thankfully the only damage was a loose CRT neck plug. The JSM-T200 joins [Ben's] homemade SEM, his DIY CT scanner, the perfect cookie machine, and a host of other projects in his lab.
The JSM-T200 is old tech; the primary way to store an image from this machine is through a screen-mounted Polaroid camera, much like an old oscilloscope. However, it still has a lot in common with current SEMs. In live video modes, an SEM can only collect one or two reflected electrons off a given section of a target. This creates a low contrast ghostly image we’ve come to associate with SEMs.
Attempting to fire more electrons at the target will de-focus the beam due to the electrons repelling each other. Trying to fire the electrons from higher voltages will just embed them into the target. Even SEMs with newer technology have to contend with these issues. Luckily, there is a way around them.
When “writing to photo”, the microscope switches to a slow scan mode, where the image is scanned over a period of a minute. This slower scan gives the microscope extra time to fire and collect more electrons – leading to a much better image. Using this mode, [Ben] discovered his microscope was capable of producing high-resolution digital images. It just needed a digital acquisition subsystem grafted on.
Click past the break to see how [Ben] modernized his microscope!
Using the schematic, [Ben] connected his Tektronix MDO3000 series oscilloscope to the video signal of his SEM. Tek was kind enough to give this model to [Ben], [Dave Jones], and several other prominent hackers. We’d love to try one out too, but we’re pretty sure we’ve been permanently placed on their naughty list.
By triggering on the SEM’s vertical refresh, [Ben] was able to capture an entire image into the scope’s memory. He exported the data to a USB stick and loaded it into GNU Octave, He wrote a simple script to search for the horizontal refresh pulse and build up a raster image. The results are stunning, to say the least. [Ben's] was able to capture the classic fly eye without first plating the fly with metal, as is normally required for SEMs.
We can’t wait to see what [Ben] comes up with next!