Cinema glasses for a 3D movie (master Image) detect the helicity of circularly polarized light, which is produced here by quarter-wave retarder sheet (International Polarizer IP160WR-I) with its fast axis at an angle of 45 degrees on top of the LCD screen of an iPad 2; the background image is <a href="//commons.wikimedia.org/wiki/File:Circular.Polarization.Circularly.Polarized.Light_plane.wave_Right.Handed.svg" title="File:Circular.Polarization.Circularly.Polarized.Light plane.wave Right.Handed.svg">File:Circular.Polarization.Circularly.Polarized.Light plane.wave Right.Handed.svg</a> (PD by <a href="//commons.wikimedia.org/wiki/User:Dave3457" title="User:Dave3457">User:Dave3457</a>).
<a href="//commons.wikimedia.org/wiki/User:Pieter_Kuiper" title="User:Pieter Kuiper">Pieter Kuiper</a>
<span class="int-own-work" lang="en">Own work</span>