Page 120 - Modern Optical Engineering The Design of Optical Systems

The Primary Aberrations 103

R

R R
R COMA T

(COMA − R)
T
2R
R

60°

COMA T LOCUS of
marginal zone rays

LOCUS of
0.707 zone rays

LOCUS of
COMA S 0.50 zone rays

Figure 5.26 Details of ray placement geometry in a drawing
of the ray pattern for third order coma.

2
longitudinal spherical is reduced by (10/20) from 2.0 to 0.5; the coma is
2
reduced by (10/20) from 2.0 to 0.5, and X T is unchanged at 2.0. When the
field is reduced to 2.5 , the spherical is unchanged at 0.5; the coma is reduced
2
by (2.5/5) from 0.5 to 0.25; X T is reduced by (2.5/5) from 2.0 to 0.5.
Thus we have:
spherical coma tan field
original 1.0 1.0 1.0
(a) 0.5 0.25 0.5
(b) 2.0 4.0 2.0