Over the past couple of years, gadgets have become much more touchy-feely. Apple's iPhone and Microsoft's Surface (an interactive table) are two of the most celebrated examples. Now, Microsoft has added a twist to Surface that makes for an impressive demo.

Microsoft announced the upgrade to Surface, called SecondLight, at the company's Professional Developers Conference in Los Angeles on Wednesday. As the video above demonstrates, in this new version of Surface, a secondary image is projected above the main display. A person views the second image by holding a semi-opaque object, such as a piece of paper above the display. The idea is to provide a second layer of information: labeled constellations on top of photographs of stars or street names on top of maps, for instance.

SecondLight uses a neat trick to produce this second layer. The original Surface used a projector below a glass tabletop to create an image and infrared cameras underneath to detect fingers and objects in contact with the surface. With SecondLight, Microsoft has replaced the glass top with a liquid crystal display (LCD), but kept the projector underneath. The LCD flickers on an off and, during alternate frames the projector sends the secondary image through the display. This happens too fast for your eyes to catch it unless you hold up an opaque object, like a piece of paper.