Biomedical Engineering Reference
In-Depth Information
A
H
′
f
H
′
c
Violet
image
F
′
f
F
′
c
Red
image
Lateral
chromatic
aberration
B
H
′
f
H
′
c
Longitudinal
chromatic
aberration
Violet
image
Red
image
f
′
1
+
f
′
2
2
Figure F-2.
A.
An achromatic doublet has no longitudinal chromatic aberration when
the separation of the principal planes for 486 and 656 nm (
H
′
f
and
H
′
c
) results in the
focal points for these wavelengths being coincident. When this occurs, however, there
is substantial lateral chromatic aberration.
B.
When two lenses are separated by an
appropriate distance, lateral chromatic aberration is eliminated. Under these condi-
tions, there may be substantial longitudinal chromatic aberration.
Adding together the powers of the three interfaces, we obtain a total power of
approximately
6.00 D. This calculation shows that when the back surface of the
first lens has the same radius as the front surface of the second lens, the combined
power of two lenses in air is the same as when they are joined together.
+
