Sensor that detects the height of your hand above a given point, ANY IDEAS?

... Does anyone know a sensor that detects the height of your hand above a given point? ...
... Or does anyone know a laser device that can detect the position of the hand above it? ...

>.. I want to apply it on my Laser Harp idea, to control the Volume of the speaker.

Mainly the idea is, the position of the hand above the device that produces a laser line will control the volume; if in high position high volume, if in low position low volume, etc.

>. Tnx if you guys can comment, suggest, advice. XD

Comments

[RavensCraft]

Sounds like you want something similar to a control that might be
found on a theremin.

Lots of theremin plans out there on the net,
so just do a search for "theremin"

[steveastrouk]

Thermin tech would be interesting, when presumably he wants multiple channels of "strings"

[rickharris]

Much depends on what you do with the data after it is sensed.

Ultra sonic
Capacitive over short distances
a series of light beams parallel to the floor you hand interrupts them.
A physical connection turning a pot e.g. a wire attached to you hand/glove.