According to Wikipedia (Source: en.wikipedia.org/wiki/Laser_harp), a laser harp is an electronic musical instrument consisting of several laser beams to be blocked, in analogy with the plucking of the strings of a harp, in order to produce sounds.
It was popularized by Jean Michel Jarre, and has been a high profile feature of almost all his concerts since 1981. It has subsequently been used in a number of different designs, including a MIDI version invented by Philippe Guerre.
Laser harps are usually built as Framed style or Unframed style harps, also known as “Infinite Beam” laser harps.
Framed style laser harps are built to resemble a classical harp with strings. Photodiodes as well as low-powered lasers (usually around 5mW) are set inside a frame. Number of lasers can vary from a simple harp with one or two lasers up to 32 or more, depending on the complexity of MIDI hardware and software.
Unframed style harps usually consist of three components – laser projector, controller and a sensor. First versions of unframed laser harps had all three elements set in a single box. Recently however, laser harps are built in a way that the three components can be placed independently and connected by proper cables. Best example of such technology is Prolight’s Laser Harp Controller.
Laser projector and sensor are positioned facing each other and both are connected to the controller box. This gives the whole system more versatility since you can use any kind of laser projector (usually high-powered lasers are used, from 5 to 20W or more) and place the components in any way you desire. The controller box is essentially a MIDI controller that sends MIDI signals. Unframed laser harps are more complicated to build than the framed style harps but they offer much more flexibility and adaptability.
Laser projects an array of beams into a fan arrangement. When the sensor detects a blocked laser beam it sends a signal to the Laser Harp Controller which, in turn, sends a MIDI signal to the synthesizer, sampler or a PC sound card which is responsible for playing the desired sound according to the information received.
Benefits from using high-powered lasers are multiple since they make it easier for the sensor to detect an interrupted laser beam and they provide a more compelling visual experience for the audience.
Laser harp performers usually wear white gloves to improve the sensor’s ability to pick up the reflected light and as a protection from potentially hazardous laser radiation as well as to give an audience a more impressive visual performance.