Alternate approaches to cloaking

摘要

1. Optical camouflage technology: A modified background image is projected on to a cloak of retro-reflective material (used to make projector screens); the wearer becomes invisible to anyone standing at the projection source. 2. The'mirage effect': An electric current is passed through submerged carbon nanotubes to create very high local temperatures, which causes light to bounce off them, hiding objects behind. 3. Calcite crystal prism: Calcite crystals send the two polarisations of light in different directions. By ueing prism-shaped crystals gether in a specific geometry, polarised light can be directed ound small objects, effectively oaking them.