Spinning plates on poles used be a popular event, but is now seen as totally passé. (see link) Perpetually Spinning Plates Apparatus is a device which replicates this famous cabaret action performance.
It consists of the poles, spinning plates, and a roving mechanical arm that reaches out periodically to grip then agitate the poles, always just in the nick of time, preventing the most wobbly plate(s) from falling to the ground. A constant rain of falling rice particles adds to the spectacle, as they bounce randomly off the rotating plates, and get flung against the protective glass front.
Sensors combined with motion detection and processor analysis ensure that the whole operation is unpredictable, but fully automated. Place it in a shop window and leave it without explanation to spin away.
Who will build it for me? Ha-- xenzag, Dec 01 2018 Spinning Plates https://m.youtube.com/watch?v=k44uoVm0lPI [xenzag, Dec 01 2018] Er, does this involve bits of buttered bread and cats?-- not_morrison_rm, Dec 01 2018 Eh no, but there could be a human heads on the plates variation - care to offer yours? :-)-- xenzag, Dec 01 2018 Seeing as it's completely empty, it would unbalance the array.-- not_morrison_rm, Dec 01 2018 I don't understand what you are asking me? Could you rephrased your question?-- xenzag, Dec 01 2018 You could bounce lasrs off the plates to make a pretty pattern on the ceiling.
Also, I have some vague memory that IBM made the first barcode scanners with a spinning mirror that directed the laser. Wikipedia says, "Most of them [a particular kind of barcode scanner] use a single rotating polygonal mirror and an arrangement of several fixed mirrors to generate their complex scan patterns-- beanangel, Dec 01 2018 Most (probably all?) laser-based barcode scanners, regardless of manufacturer, do that. Look into the windows of a self-checkout machine next time you use one. There's a spinning polygonal mirror in there (probably hidden, though) and the beam bounces off of that and then off of some more mirrors to generate the pattern of crossed lines. The important thing is that it's still only a single beam, meaning only one point is illuminated at a time, and the length of one of the lines is traced before the beam makes the next line. This converts the spatial reflectance pattern of the barcode, in just about any orientation, to a temporal reflectance pattern, which can be interpreted by the computer.
There are now many handheld barcode scanners that use a 2D camera instead of a scanned laser beam. Also, librarians in my city used to (around 15 years ago) use "pen" barcode scanners that just had an unfocused red light (maybe laser, maybe LED) and they had to swipe the pen along the barcode at a constant rate to scan it.
Laser printers also use polygonal mirror-based laser scanners, though they only scan in one axis and don't use secondary mirrors to break up the pattern.-- notexactly, Dec 07 2018 random, halfbakery