This paper describes a method for testing a right angle prism,
or any other optical component having a right angle, to subarcsecond
accuracy. The method makes use of Haidinger fringes and is simple to
use. Unlike autocollimation and Fizeau interferometer methods, it does
not involve an expensive optical setup and has no aperture restriction.
The sensitivity of the method can be suitably modified by changing the
test setup parameters.