The performance of an optical imaging system depends not only on the accuracy of figure of its individual components, but also on the accuracy of alignment of the assembled components. Provision for achieving alignment can be made by having the appropriate number of centring and tilt adjustments. However, the number of adjustments can be advantageously reduced by coupling centring and tilt so as to constrain adjustment to rotation about a chosen neutral point, thus optimizing the alignment achieved for a given effort. The concept can be implemented by using spherical interfaces, or reference mounting surfaces, and is discussed in relation to several x-ray imaging devices. Some wider applications, such as scanning and steering optics, are also discussed.
M. Stedman, M. Stedman,
"Spherical Interfaces In The Assembly And Alignment Of Multicomponent Optics", Proc. SPIE 0235, Aspheric Optics: Design, Manufacture, Testing, (13 May 1981); doi: 10.1117/12.958972; https://doi.org/10.1117/12.958972