Reeve, C.; Veale, R.
NBS Internal Report 76-993; 30p. January 1976.
Autocolimator; calibration; constant deviation prism; geometrical model; optical square; pentaprism; reflection; refraction; standard deviation; uncertainty.
A pentaprism, or optical square, is one of a class of objects known as "constant deviation prisms" whose purpose is to bend a beam of light exactly 90° regardless of the angle of incidence of the light. It is used in many optical measurements where the line of sight or beam of light must be turned at a right angle. The calibration process which is described is fairly simple and requires two mirrors, two autocollimators, and a surface plate. Consideration is given to the effects of small angular errors in both the internal geometry of the pentaprism and the positioning of the pentaprism relative to an autocollimator. An example of the calibration of the important pentaprism parameters is given. A simple statistical test is employed for testing whether the measurement system is in control.