Micrometers, or microscopic rulers, are a little expensive; something like $15 each. But they're really helpful for measuring the scale of (i.e. calibrating) a microscope, as in these activities:
I wonder if it'd be possible to print a micron scale on a DVD or blu-ray disc using one of these DIY techniques?
I think there are other programs out there to do this too; it's just hard to search for them because "burn image onto DVD" usually means like a JPG image file, not a visible image... haha.
If we could print a square checkerboard grid with 10 micron resolution, it'd be pretty cheap to make lots of these. It might be necessary to peel the disc in half to use it, but that might be a good idea anyways to cut it into multiple calibration slides.
Looking at this image, i think it's possible either a DVD or Blu-ray disc could make a useful 10 micron scale ruler... though it'd be a little rough to look at... like, would it be squares of smooth and pitted regions, alternating?