Neutral Density Filters

Neutral Density filters are used to decrease the intensity of light by a given amount. The manner in which this is accomplished can be by absorption or reflection.  An absorptive filter reduces stray light by absorbing the unwanted light, but the performance can be changed by changes in temperature and thickness and are best suited for low power or visible systems.  A reflective Neutral Density Filter reflects the unwanted intensity which then needs to be accounted for in the system optical design.