Darkfield model autocollimator is perfect for measuring small, flat mirrors.
Nikon's 6B autocollimator checks alignment and measures very small angular deviations to measure flatness or height by simple geometry. The 6D darkfield model projects a bright crossline and is the most popular model because the bright-line cross is the easiest to see. Provides measuring accuracy down to 0.5 arc seconds.
Applications: Surface Analysis