A liquid sky scanner is also known as a polygon scanner. Imagine something like a hex-nut that spins. A laser hits the vertical surface and the beam is reflected back. As the surface rotates, the beam sweeps across the plane it is on. Essentially, this is all the scanner is. However, it has a scan rate of over 800hz and a great quality mirrored surface.

And the results:

Powering the scanner can be done with two 9-volt batteries collected in series. From there, simply point the beam at the reflective surface and voila - a nice even beam is projected. There are no visible artifacts produced when the surface is clean. This high quality scanner is easily worth the price. See the video below for it in action