Page 168 - Modern Optical Engineering The Design of Optical Systems

Prism and Mirror Systems 151

Figure 7.36 Possible orientation paths for the reflecting sys-
tem exercise in text.

has the proper orientation, but the light is traveling away from the
screen. If we add a mirror to reverse the direction of propagation, we
will have both orientation and direction as required. To accomplish
this without directing the light back through F, we must resort to a
figure 4 arrangement as shown in Fig. 7.37, which diagrams the entire
system.
It is quite apparent that Fig. 7.37 represents only one of the many
possible arrangements of mirrors which could be utilized to accomplish
this same end result. The reader may also have noticed that the dis-
cussion has been limited to reflections for which the plane of incidence
lay in one of the cartesian reference planes, and also that first conside-
ration was given to reflections which deviated the axis by 90°. For the
novice, these restrictions have much to recommend them; one is well

Figure 7.37 One possible solu-
tion to the exercise in the text.