Using lenses to bend light, YouTuber Brusspup makes a ruler, a knife, a spoon, a hand, and a laser completely disappear from view. Invisibility lenses create the illusion, an optical trick based on The Rochester Cloak, multidirectional cloaking experiments from the University of Rochester.
Brusspup describes what’s happening in the video notes:
It uses 4 lenses to control light in such a way that it renders an object invisible. When the light enters the first lens, it flips the image upside down. The second lens sends the light straight into the 3rd lens. The 3rd lens focuses the light into a point about 3 inches past the lens. Since the light is focused into a point, any object placed around that point cannot be seen when looking through the lenses. The light is essentially bending around the object. Once the light hits the point just past the 3rd lens, it then flips back right side up. This allows the background image to pass through all of the lenses without warping or being seen as upside down.
This Outrageous Acts of Science video explains further:
And this University of Rochester video demonstrates the original work:
Follow these with this 2013 uni-directional demonstration of optical cloaking.
Plus, create pattern distortions seen through a glass of water, the Reversing Arrow Illusion, and another illusion: How to make a 3D “hologram” using your smartphone & a CD jewel case.