Tolerance eigenmodes of optical systems

We describe an eigenmode analysis technique that can be used to determine how an optical system will react to tolerances. The input stimuli are the tolerances of the system, and the resulting eigenmodes are the aberration patterns that will be "driven" by them. The eigenmodes are orthogonal and include both pupil and field dependencies: field-uniform coma, field-uniform lateral color, and field-linear, field-asymmetric astigmatism are examples. The eigenvalues provide a means of rank-ordering the eigenmodes according to importance when considering a set of alignment compensators that might be included in the system to mitigate the effect of tolerances.