So this is a thing called a Vidicon tube. When we got shown this in our visit to the ‘Museum of Redundant Media’ I was immediately fascinated by it, but I’m now slightly regretting my decision to research it after reading its Wikipedia page about five times and still not getting it.
There’s a whole lot of confusing science-y explanations involved, but my general understanding is that it is a ‘cathode ray tube’ which turns light energy into electrical energy. It converts optical images into electrical signals which can then be scanned. An electronic charge image is formed that corresponds with the optical image, and then a current is produced. This current then produces the video-signal output of the camera.
Here’s a diagram that I don’t completely understand but may or may not help anyway:
Or a video that explains how it works in a much better way than I have:
