Nice LED interference patterns through a glass jar - needs a slow actuator

[RoGeorge]

Was testing some 0.2W SMD power LEDs, and noticed interesting light patterns through the irregularities of a glass jar.  The interference patterns are even more mesmerizing when the LED is slowly moved inside the jar.  Almost any cylindrical glass seem to produce such patterns:  jars, glasses, bottles, etc.



Would like to make a few decorative light jars, similar with a lava lamp but with interference.

Any idea for a slow and silent actuator, so to smoothly move a LED hidden in the lid of a jar?

[ajb]

Neat!  The optical term for that effect is a 'caustic (video)', essentially the glass acts like a lens that instead of having a focal point has a focal curve.  When used for abstract visual effect, it's generally referred to as "lumia", after the work by Thomas Wilfred starting in the 1920s.  He was of course using incandescent light sources and colored filters: https://americanart.si.edu/videos/thomas-wilfreds-lumia-unit-86-154416.  In the 70s it became a key part of a lot of planetarium laser shows, taking advantage of the vibrant colors that Wilfred never had access to.  There are still some dedicated folks building new and unique lumia generators for lasers: https://www.youtube.com/watch?v=uJrP585lT4A.   Of course now you can also buy all kinds of cheap mood lights from the usual websites that use the LEDs and rotating lenses. 

Very low speed DC gearmotors would be the default actuator for this sort of thing, like 10RPM or even less, although the ideal speed depends on the optical components you're using and what kind of effect you want.  I know a couple people who have seen good results with geared stepper motors for extremely low speed effects, although they require drivers.  Most people move the lens rather than the light source, but either way works.  You can also add a moving component between the fixed light source and the lens, which is a common technique for creating more intricate effects.  Honestly a lot of this really comes down to playing around with variables until you get something that looks interesting. 

[themadhippy]

How about a microwave turntable motor,low voltage versions are  available reasonable cheap.