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Topic: laser harp plans and code from Steve Hobley (Read 6 times) previous topic - next topic

jaaroson

looking for somebody who has the plans to the laser harp that Steve Hobley made because he has sold the rights to it to some company and can no longer distribute them.

Anything would help

thanks

cr0sh

The basics of it seem simple - a powerful laser or lasers, beams split in a fan pattern, with a web camera or wii camera positioned to see the dot of light on the performer's hands; the laser really is only powerful in order to show the fan for the audience, and to an extent the performer as well, so he knows where to "pluck". However, a basic model (with invisible beams, unfortunately) could be made with a simple red or green laser pointer; with the appropriate filter over the camera, even a <5mw dot will be visible on the camera. Later you can upgrade to a more powerful laser.

The difficult part is the software - you need software that can see the dot or dots, locate them in 3-space, and then use that information to play a midi note (which is then sent on to the rest of your midi stack); this requires a PC running some vision software; its like a Sega Activator on steroids. If I were building one of these, or experimenting with the idea, I would first look into doing a single beam, using a cheapo webcam-based laser rangefinder like this:

http://sites.google.com/site/todddanko/home/webcam_laser_ranger

That would be the starting point. Once you had that working, you would need to set it up so there was as wide a field-of-view (FOV) for the camera as possible, then generate multiple beams with a beam-splitter or some other means; you could potentially use a mechanical scanner to scan a beam, and pulse the laser on/off at various points, tracking the angle of the shaft of the scanner so you knew which "string" was being generated, then the dot on the hand, picked up by the camera, could be figured out (distance) using the info in the above link...

Alternatively, one could steady-state the beam fan, then use one or more cameras and some vision software (like OpenCV), plus a ton of custom coding to locate the dot in 3-space, etc.

I know the above isn't what you wanted, but maybe it will give you or someone else some ideas on how such a system can be implemented...

:)
I will not respond to Arduino help PM's from random forum users; if you have such a question, start a new topic thread.

jaaroson

thanks for the info.  I don't want to have to re-engineer this and was hoping to build one for a Worship group before Oct this year.  I will be buying a 100mw green laser with blanking feature so to do this up right.  I need all his plans and code to save time essentially.  

mowcius

Quote
I will be buying a 100mw green laser with blanking feature so to do this up right.  I need all his plans and code to save time essentially.

I think his laser was more like >200mW as when you split it up the power decreases on each 'string'/line

The webcam could be connected to processing to analyse the light position and then output a MIDI value to some other software. Should be simple.

Mowcius

T.J.L.

#4
Jul 21, 2010, 01:33 pm Last Edit: Jul 21, 2010, 01:35 pm by T.J.L. Reason: 1
[OT]Couldn't you aim the laser beam at LDRs or LEDs and use them as light sensors for detecting if the laser beam is interrupted or not? I guess that would be much more simple than image recognition with camera. Or does the harp need to detect at which point the beam is interrupted?[/OT]

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