Close Encounters of the Third Kind - Scanner Effect

From the book "Close Encounters of the Third Kind - The Making of Steven Spielberg's Classic Film" by Ray Morton

"Another important lighting effect on the underbelly was the scanner- a series of white lights that rotate around the circular cutout from which the hatch emerges. To create the scanner, a piece of fiber-optic cable was attached to a tiny motorized arm that circled around the cutout at the rate of one revolution per frame. The cable was threaded down through the underbelly and attached to a motorized grip that moved back and forth on a track set up in front of a very bright light source. Robert Swarthe cut several zigzag patterns out of pieces of shiny black paper, which were then mounted in glass and placed between the light source and the motorized grip. During filming, the grip would move past the patterns. The black paper would block the light coming from the source, but when the grip moved over an open area in the pattern, the light would shine through and the fiber optic would transmit it to the scanner arm. This on-again, off-again pattern broke the scanner line into segments. The long exposures employed to shoot each frame caused the lights to streak a bit. As a result, some of the scanner lights appeared to expand and contract, while others appeared to merge with and separate from one another. Like the other light patterns, the scanner effect was filmed in its own separate pass."