liquid crystal light valve

This type of valve is often referred to as a liquid crystal light valve.

Liquid crystal light valves work by rotating light between two polarizing filters.

In 1936, the Marconi Wireless Telegraph company patented the first practical application of the technology, "The Liquid Crystal Light Valve".

The basic idea is some device, such as a liquid crystal light valve, is used to produce schlieren distortions in a controlled manner and these are projected on a screen to produce the desired image.