Laser circlescope: Visitors From Dreams

The laser's back and this time I'm finally getting around to trying out some real-time effects using JACK. This is a simple circular oscilloscope (look ma, no retrace!) spinning at some multiple of Middle C frequency, which works particularly well for music. I found that chiptunes, due to the simplicity of the waveform, show up in very interesting ways. Keep in mind that this is a crappy 30fps digicam capture; it looks a lot better in real life. The sync is also a wee bit off here, in real life it's perfectly synced by design (audio and laser outputs are synchronous).

The song is Visitors From Dreams by Dma-Sc :)

Although not shown, blanking and brightness modulation also works, though the laser has trouble achieving full power unless it's on 100% of the time. Here (fully on), it's probably putting out 40-50mW or so - I measured 60mW when I got it but I run it a bit lower here for safety.

Note that the room lights were on and the window was fully open when I took this video: I had to turn down the exposure on the camera to reduce the artifacts caused when the image is acquired from the camera sensor. You can still see them somewhat, particularly right at the very beginning, above and below the circle.

Random tidbit: the blink at the beginning was caused by a JACK xrun that occurred as the music started. The safety controller on board the laser kicks in and shuts down the laser at most 0.5ms after it senses a failure of the software, and keeps it that way until it gets a stable signal for a few hundred ms. I do this by dedicating one soundcard channel to a 1Khz pilot signal - when it disappears, even for one cycle, the safety controller powers down the laser. It also does power supply monitoring and short circuits the laser as soon as it senses the main PSU output falling, which hopefully should eliminate any dangerous (for the laser) transients.

Category:

Science & Technology

Tags:

• laser
• scanner
• projector
• oscilloscope
• scope
• chiptune
• JACK

[marcan42]

Makes me want to build 3-8 of these and do one plot per channel for chiptunes. Too much time/money though :( Not sure how good it'll look if I try to fake it by multiplexing between them, it'll lose the "realtime" feel.

[Ivnuk]

@marcan42 : Multiplex the bass channel away from everything else. Then use a beat detector so that when there's a bass-kick, offset the bass-channel to the left (instantly), and the others to the right; then have them come back together between beats. Of course, each channel will probably only be half as bright, but... with a laser, that might not matter so much.

[marcan42]

@Ivnuk Good idea! That is actually impossible to do with the original code (which has laser output that is 1:1 derived from audio, no effects like that possible) but I reimplemented the circlescope as a libol app running withing the full-blown rendering framework for my 27C3 lightning talk, so *now* I can start trying out things like that :)

[NexonPlayerNA]

At first, I thought it was me farting. Then, I thought a black hole was opening up. Then, after reading the description and realizing that full-on lighting was present, I shat out of my man-titties.

[trillhouse992]

Song reminds me of Darwinia... oh wait.. it was in Darwinia ;)

[MrJminecraft]

lol just do some acid and watch that all day..

[grovyle05]

@masterpj55 Yeah... I'd probaby fork out a fortune to get one of these! Marcan should really start selling some.

[Ivnuk]

@marcan42 : Awesome! Well, props on a very cool project. I will keep an eye out for updates. :-)

[VillainousOperative]

Wow, you couldn't have picked a better song. That looks exactly like something out of Darwinia! Epic dude!

[TheLyl4ever]

Epic 10/5

[niaimack]

darwinia