Laser harp

This style of laser harp is generally built using a single laser, splitting its beam into an array of beams in parallel or fan arrangement. Playing the actual sound is usually handled by connecting the laser harp to a synthesizer, sampler or computer.

This frameless design is more elaborate than the framed style, relying on reflecting the light back to a single photodiode. The fan of laser beams is actually a single beam scanned into a fan pattern. By matching the timing of the reflected beam, the instrument can determine which beam the player is blocking and sound the corresponding note. Alternative designs use multiple lasers. In these designs, each laser can be independently controlled (pulsed on and off) to simulate playback of prerecorded notes.

Several techniques generate more control data, such as a continuous range of values like those in typical MIDI controllers:

• An infrared or ultrasonic rangefinder attached to the instrument that determines the position of the hand that blocks a beam
• A laser-based rangefinder that determines the distance from the hand to the laser's starting or ending point (and possibly using this laser itself as the string)—or a variation of this that uses the intensity of the sensor signal itself
• A camera that tracks position and motion of the laser dot on the hand, or length of the exposed beam if visible, then calculates a continuous value based upon a reference

The first of these is relatively inexpensive and straightforward to implement, and can use the same micro-controller that drives the lasers and reads the detectors.

The advantage of a dedicated sensor mechanism is that the instrument can be self-contained, as opposed to requiring a computer to control it with input from an ILDA interface and USB camera. The PC-based approach, however, offers more flexibility and can be constructed with mostly off-the-shelf hardware.

Unframed laser harps benefit from the use of higher-power lasers, as they facilitate easier detection by the sensor system. As the sensor is exposed to all ambient light, it can be swamped by stage lighting behind the artist if the sensitivity is too high. To avoid this, the system can use ambient light sensors to reject ambient light. The player may use white or light-coloured gloves to improve performance by scattering more light off the player's hands to provide the sensor with a higher signal-to-noise ratio with respect to ambient light. Furthermore, the gloves protect the player's skin from potentially hazardous laser radiation and give audiences a more visual impression of the instrument.

In 2008, Maurizio Carelli, an Italian software and electronic engineer, had the idea of a bicolour (red and green) laser harp. This device features a configurable full octave with green beams for any diatonic note and red ones for any chromatic note for full Diatonic and Chromatic scale.[1] In this way any musician can easily play a laser harp, fully polyphonic. This machine became the first portable bicolor laser harp, and it is still in production. In the second half of 2010, Carelli also designed an ILDA full color laser harp controller.

In 2005, a multicolour laserharp free project using ILDA interface is shared on laser discussion boards and exposed same year at a German meeting.

Beams at the laser harp controller (Genesis controller)

Since the project grows and a software came up to control the hardware. Now it's possible to get color change, patches with visual effects, vibrating beams, and even sound modulation with hand height

The image recognition laser harp is also an unframed design, but uses a high-speed USB camera connected to a laptop computer, instead of a photodiode to detect the reflected light from the hand breaking the beam. The digital picture is analyzed by the computer software to determine which beam is broken and send the appropriate MIDI signal back to the synthesizer, which is responsible for creating the sound. The computer also controls the laser projector via an ILDA USB laser controller.

The framed style, which is often created to look like a harp with strings, uses an array of photodiodes or photoresistors inside the upper or lower part of the frame to detect blocking of the laser beams. The framed harp built by Geoffrey Rose in 1975–76 was an octagonal shape with a 5×5 matrix of laser beams. The lasers can be mounted on the 'neck' or upper side of the harp, shining down, or on the body, shining up. Typically, the lasers used are very low-powered 5 mW red or green lasers, which are considered safe for public interaction by the FDA. Any number of laser beams can be arranged in this type of laser harp, from as few as one or two, up to 32 or more, depending on the capacity of the MIDI controller(s) and software being used. This style of Laser Harp can be created in any size, from a lap sized harp to a room sized installation, or larger, like the installations seen at Burning Man. In this design, only an analog trigger is created by the breaking of the beam (and the DC circuit made by the beam shining on the optic sensor), which is sufficient to trigger any number of events (musical or otherwise) as determined by the data analyzer or software in question. In the MIDI controller, this analog DC current interruption is converted to a digital signal, which is then used to trigger many possible events or actions. Some software comes equipped with full wave file editors and synthesizers, and can also trigger video and still imagery via projection units.