ChromaDepth (TM) glasses for a 3D effect with a Christmas tree card

Viewing the Christmas tree card through the special spectacles which consist of blazed-gratings makes the red decorations appear in the foreground. If you are interested in the physics behind this effect there is much information to be found on the web. John Davenport purchased the spectacles and card from Tim Rowett at the International Puzzle Party 31 in Berlin in 2011.


Date Circa 2011
Key Phrases
Ref no N1587