Sounds something like “nulling”. Astronomers have been using the technique for a long time.
“A nuller is a tool used to block out a strong source so that fainter signals near the source can be observed. An example of a nuller is being employed on the Keck Interferometer. This causes the light from a star to destructively interfere, effectively cancelling out the star’s image. The faint light from an orbiting ring of dust can then be detected. This project is part of a scientific effort to detect and observe nearby planets.”
http://en.wikipedia.org/wiki/Nuller
My hand is a “nuller” when I want to look at an item near the sunset.
bm