When we first pulled the vacuum fluorescent display (VFD) from an old Canon tuner timer unit, we can see a lot of intricate details inside the sealed glass. We had work to do that day – probing the pinout and such, but part of its overall allure comes from the beauty of details visible within. It is still something of interest, I just had to remember to bring my camera with a close up macro lens to take a few photos.
One of the reasons a VFD is so interesting to look at is the fact the actual illuminating elements sits under other parts which contribute to the process. Closest to the camera are the heating filaments, visible as four horizontal wires. This is where electrons begin their journey to trigger fluorescence.
Between these filaments and individual illuminating segments are our control grids, visible literally as a very fine mesh grid mostly – but not entirely – built on a pattern of hexagons.
And beyond the control grids, our individual phosphor coated segments that we control to illuminate at our command using our prototype driver board. (Once it is fully debugged, at least.) These phosphor elements are what actually emits light and become visible to the user. The grid and filament are thin which helps them block as little of this light as possible.
Fortunately an illuminated VFD segment emits plenty of light to make it through the fine mesh of grids and fine wires of filament. From a distance those fine elements aren’t even visible, but up close they provide a sophisticated look that can’t be matched by the simplicity of a modern segmented LED unit.