How do the Strings Work?

A project log for Litar: LiDAR Air Guitar

Compact, handheld air guitar with four LiDAR strings and Bluetooth

bleckyBlecky 03/18/2018 at 13:000 Comments

The sensor array on the Litar has been designed to allow for the lowest latency and best accuracy possible when obtaining a string interaction. Each string has a specific geometry that allows them to be easy to play and makes them large enough to pluck.

The sensors are aligned in such a way that three sensors see a single string in space; two sensors define the string border and a third sensor obtains the string distance. This enures that you don't get miss plucks and it also allows the strings to be packed tighter together over one or two sensor setups (the sensors have a 25 degree field of view). To visualise this, the image below shows the sensor field of views, with the grey areas highlighting the virtual strings:

To obtain the strings, the data from the sensors is brought into an array of sensor distances over time and placed through a rapid-change detection algorithm. The algorithm scans each combination of sensors which create a string and then obtains the correct distance for the string being plucked. It does this by looking at the most recent value as well as its history to determine which string has been plucked, with the latency of a single distance measurement. With this you can also obtain entrance to the string area velocity information, without increasing latency.

And that's how the Litar gets its strings.