ABSTRACT
In general, the full real aperture of a lens system has to be greater than the diameter of the stop, as shown in Fig. 9.1, in order to allow light beams from off-axis object points to enter the lens. On-axis, the effective clear aperture is smaller than the lens. If we obtain the meridional plot for the full lens aperture with an enlarged stop in contact with the first surface of the lens, or at any other selected place, we obtain a graph like that in Fig. 9.1. After placing the stop with the correct diameter in its final place, only one region of this graph will be used. This kind of enlarged meridional plot is very useful in many systems to determine the best position for the final stop and, by analyzing it, we may obtain the following information:
1. The height TA0 is the lateral image displacement due to distortion. 2. The difference in heights TA0 for several colors is the magnifica-
tion chromatic aberration, if plots for different wavelengths are obtained.
