Calibration of Interferometer Transmission Spheres

As the tolerances on optical figure get tighter and as the need to provide traceable test methods to fulfill ISO 9000 standards becomes greater, the more there is the need for a robust and reliable method to determine the residual error in interferometer test optics. This paper describes an inexpensive, quick and self-consistent method of calibrating spherical transmission optics where there is a real focus of the diverging test beam outside the transmission optic. The method is self-consistent in the sense that any given test result provides a means of calculating the variance of the result and requires no additional optic that must be calibrated or traced to another standard.