I’ve had a bunch of requests from people (mostly via YouTube) asking about my laser harp, so I thought it might be useful rather than constantly repeating myself to make this FAQ page.
Q: Did you build it yourself, can I see the plans you used?
A: Unfortunately I was not able to build it myself. The main reason for this is that plans to build a laser harp are no longer available. Why? The short version of the story is; originally detailed plans were created by Genesis for general use. A few years later Steven Hobbley published his own version. These plans were then sold to a commercial company, at which point they were taken down from the web, since they then became copyrighted by that company. Other plans are availble by Andrew Kilpatrick (http://www.andrewkilpatrick.org/?p=laser_harp), however, in my view the end product is inferior to the original project and the plans are not quite as comprehensible.
Meanwhile, an Italian engineer decided to make his own version of the laser harp in a more portable and durable form factor, the kromalaser ( http://www.kromalaser.com ). After a few discussions between him and I, I was convinced that this was the device I had been searching for. It has many benefits over both Stephen and Andrew’s design, and furthermore I was able to contact the UK distributer for the kromalaser and meet with him for a test-drive of the harp.
Q: Where can I buy a laser harp?
A: As above, I’d recommend the kromalaser ( http://www.kromalaser.com ). It is, to my knowledge, the best laser harp available today. If you are in the UK, the distributer you should contact is Tim at CMTEvents http://cmtevents.co.uk/ – Tell him that Greig at thereminhero.com sent you and you might get a discount
Q: How much does a laser harp cost?
A: This depends on many factors. If you are building one yourself, a professional green laser with enough power to create a visible 13-split beam with minimal amount of smoke should be at least 200mW, in my opinion. So for the laser alone you should be prepared to pay $300 or around £200. This is just the start however. There is a great amount of extra electronics and programming knowledge, time and effort involved in making a laser harp. The parts alone will almost certainly double this price. Not to mention that if you want some of the extra features that the kromalaser gives you, such as a solid portable form factor, an additional red laser to mark which beams are the “black notes on the piano”, and a pedal control – you may be looking at a total of over $1000. At this point you also need to consider how much time it will take, which I have no experience of – but I should say that the engineer behind the kromalaser spent more than 5 years perfecting his design. I also can give no garauntee of how complete the available plans are, or how readily available the parts are. That said – if you are a keen engineer, go for it!
With respect to the RRP of the kromalaser, I am not able to give a definite figure. You will certainly looking at more than $800, further than that I am unable to say.
Q: How does your laser harp work?
My laser harp is a frameless type. Frameless laser harps differ from framed harps in that they do not require anything overhead to detect the beams; everything is placed on the floor. This allows you to get creative with the beams overhead (Maybe using mirrors to bounce them over the audiences heads), and does not require expensive trussing or alignment.
To understand how a frameless harp works, first you’ll need a basic understanding of how galvanometer scanners work..
The laser is a single beam, which uses a galvanometer scanner (essentially a very fast moving mirror) which scans the beam left and right about 60 times a second. The laser is then quickly switched on and then off at the exact right moment every time the scanner reaches the correct position of where we want one of the beams to appear. It does this a total of 13 times every time the laser scans, to give the illusion of 13 standing beams (i.e. a full octave).
For note detection, there is a photodiode mounted at a 45 degree angle just behind the source of the laser, which is part of the laser harp controller. It is angled to detect any bright spots of light in the area where the beams are broken. in other words, it looks for the reflection of the laser beams from your hands.
The photo diode doesn’t directly detect which note was played, though. It is not a camera. Instead, this is done in a much smarter way. Since the laser is scanning, and it takes time for the laser to get to the correct position of one of the beams, so the photo dioide only detects the reflected dots at specific times. So as long as we can synchronise the scanning speed with the detection time, we know which note is being played. The laser is only “on” for a specific period of time for each note. The photodioide is fast enough to detect this and the controller can accurately tell what position the scanner was in at the point when the laser was “on” and the reflected dot was seen. This tells us which of the 13 beams was being broken at the time and therefore what note to play. This also allows for polyphonic playing since the timings of two or more beams can be broken at once, but in reality they are reflecting back at different times.
Q: How well can you see the laser beams (with or without smoke)?
A: In a bright room, it is not possible to see the beams at all without a little smoke. In a dark room, you may be able to see the beams but it depends on how dusty the room is (the light needs something to reflect off) and they will still be quite faint. Generally a little smoke is always required to play. A low but constant output smoke machine with haze fluid works well, since big puffs of smoke are undesirable. “Smoke in a can” also works but it is not as effective as a smoke machine.
Q: What is a Theremin? Is a laser harp a type of theremin?
A: A laser harp is *NOT* a theremin. It is true that both instruments are played without touching anything (although you could argue light is touchable) but that is where the similarities end. If you would like to know more about theremins and how they work, check the wikipedia article or watch my theremin videos.