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Laser Harp

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Niks

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Hey everyone, hope all is well...

I am constructing a laser harp instrument for one of my university projects and as you guys are more experienced with lasers, I thought i'd seek your help.

Well first of all, i am working within a budget so I cannot afford a big laser device so probably something like a 100mW or 200mW green laser will have to do.

One of the things I would like to know is, what can I use or where can I get a lens/device that can split a single beam into 12 different separate beam?

I'd really appreciate it if anyone could kindly help me out.

Many Thanks,

Niks
 





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SenKat

Guest
Sounds like a really interesting project you have there ! :cool:

O would imagine, photodiodes would be required for feedback - the interruption of the beam to create the music, etc...you could use a controlled diffraction grating of some sort, possibly - otherwise, too many beamsplitters, and I think the cohesiveness of the beam might be an issue...I am not too sure how to go about even starting this ! Chime in folks - see if you can offer some advice !
 
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Niks

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Yea basically the beams will feed into a series of photosensor diodes, which will feed an on/off analogue signal into a midi sense board that basically converts that analogue on/off signal into MIDI information. This midi information then can be read by computer music programs or synthesizers. Concept is really simple, but its just getting hold of the components that is the issue.

I understand that using a whole series of beam splitters will effect the brightness of the laser beam down the line...so I wanted to avoid going down that road if possible. Ideally using a diffraction grafting lens would be even better. Does anyone have a clue where I could get my hands of a 12-way diffraction grafting lens?

Thanks

Niks
 
T

timelord

Guest
I'm a big fan of the Laser harp i've been live to see the man Jean Michel Jarre when he came to Houstan and i went to the gig in paris.
 

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timelord

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Niks

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Thanks mate, that does help alot but im still a bit confused when hes talking about the beam splitters and glueing them onto a metal plate?
 
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stevetexas

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Niks said:
Hey everyone, hope all is well...
Well first of all, i am working within a budget so I cannot afford a big laser device so probably something like a 100mW or 200mW green laser will have to do.

One of the things I would like to know is, what can I use or where can I get a lens/device that can split a single beam into 12 different separate beam?
Niks
Click to expand...

One option may be to get a dozen Leadlight pointers, and mod them up (if you can and use 12 separate sources).  A single laser powerful enough to work may cost $750 or more.  A dozen leadlights can be bought for around $45-50 each ($600) and save the hassle of a beamsplitter and redirecting the beams. (also, much cheaper to replace if one dies)  You'd probably have to get some sort of active cooling to keep them on more than a few minutes.

The problem I see with the leadlights is duration of time needed to play anything....  You may be better off getting a Laserglow Aries or, better yet, Hercules.
 
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timelord

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With an Aries or a Herc you will most definately need gloves and goggles even with my 125mw Viper it burns your skin. :eek:
 
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stevetexas

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Maybe I'm missing something. I thought he wanted a beam from a "big" laser split into 12 different beams. Wouldn't that decrease the power significantly?? Even if he got a 400 mW Herc, assuming a linear power drop, 400 mW / 12 beams = 33 mW per beam.

(I'm sure there is something technical I'm missing...)
 
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SenKat

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According to the article (quoted above from Wiki...) it says 20mw or above, so maybe it would work ? I don;t know - I think I will search for a free video of this thing in action - looks VERY intriguing !
 
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pseudonomen137

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I'm not sure what you meant about a beamsplitter decreasing power down the line. It may lose some power if not AR coated, but I think you'd get less losses with beamsplitters than diffraction gratings. The problem with beamsplitters is both that they can be somewhat expensive to get that many, and just might be a pain to set up.

The problem with a diffraction grating though is that the line in the center will get the most power, then the lines around that get 2nd most, etc till the most spread out lines are receiving next to none of the original power. You might just try getting some regular single-axis diffraction gratings and trying them out. I'd suggest getting one that splits it into a lot more than 12 beams, and then blocking out the extras on the sides so that the 12 beams that do pass don't seem too different from each other. Good luck with your project!
 
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Niks

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Actually I never thought of that. So basically how it could work is this...

First of all the laser is fired from the side at the bottom of the frame... which then gets redirected 90 degrees by a right angle mirror... then through the driffraction grafting lens. That would work really well. I think the only problem is that... will the diffraction lens send the beams in all different directions or just all in a single line?

I see the problem here... if i do end up using beam splitters, i guess it will split the power of the beam in half or something each time it passes through one. Therefore by the time it gets to the 10th splitter...the photocell diode probably wont even pick it up. In this case, a more powerful laser would be needed...which means more money...which means im gonna have a deep hole in my pocket!!! which means i can forget the project altogether!!!! LOL!

But using a diffraction grafting lens, I could perhaps stick to a more suitable 100mW green laser module or a 125mW dragon laser pointer.
 
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