Sure it is a cheap stage trick, but using a lenticular lens at the right angle and in ... You can see some details about the shield along with some demonstrations in the video below.

Two or more views of a scene are printed on a thermoplastic sheet of lenticular (concave) lenses that look like parallel ridges (see below). In order to align the image to the lens array ...

Lenticular 3D uses a convex lens to direct the eyes appropriately. Left and right frames appear as columns of pixels or blocks of pixels for multi-view images. THIS DEFINITION IS FOR PERSONAL USE ...