It is shown that the deviation from the Abbe's sine condition upon the stigmatic imaging of an axial point is equivalent to the deviation from unity of the ratio of distances from the optical axis of the system to the intersection points of the extreme beam with the front and rear principal spheres, respectively. The suggested interpretation of the deviation from the sine condition adequately reflects physics of this phenomenon and allows one to obtain expressions for the meridional and sagittal coma for both the stigmatic imaging of the axial point and residual spherical aberration.
展开▼
