LIGHT PIPING: A NEW LIGHTING SYSTEM FOR MUSEUM CASES
3 THE LIGHT PIPING ILLUMINATOR
A light piping illuminator consists of a roll of Optical Lighting Film supported by an opaque white plastic tube. The tube acts solely as a rigid support for the film, while its white color helps prevent light from being absorbed. A light piping illuminator is made by cutting a piece of Optical Lighting Film to fit the circumference and length of the tube. It is then rolled and inserted into the tube, with the smooth side of the film facing inward and the prism grooves running parallel to the axis of the tube. A light source is placed at one end of the illuminator, positioned to direct a beam of light into it.
Although the film is flexible, it will crack along the prisms if rolled too tightly. For this reason, the manufacturers do not recommend making illuminators less than 3 in diameter (3M 1988). It is not necessary to affix the roll of film to the tube in any way.
Utilizing different properties of the Optical Lighting Film, a light pipe illuminator can do two things with light. First, it can simply transport the light down the length of the pipe. Second, Optical Lighting Film can also be used to extract light from the pipe anywhere along its length. Before discussing these uses in detail, it is first necessary to look at how the Optical Lighting Film works.