Biomedical Engineering Reference
In-Depth Information
r
= +129.2 cm
Crown glass
Flint glass
r
= + 6.4 cm
r
= - 6.4 cm
Figure F-1.
An achromatic doublet formed by cementing a biconvex crown glass lens
to a minus flint glass lens. Radii of curvature are given for the surfaces.
Substituting, we have
F
Lens1
v
Lens1
F
Lens2
v
Lens2
= −
F
Lens1
59
F
Lens2
37
= −
F
Lens1
=
(
−
1.59)(
F
Lens2
)
and
F
Ach
=
F
Lens1
+
F
Lens2
6.00 D =
F
Lens1
+
F
Lens2
Therefore
+
+
6.00 D
= −
(1.59)(
F
Lens2
)
+
F
Lens2
F
Lens2
= −
10.17 D
and
+
6.00 D
=
(
F
Lens1
)
+
(
−
10.17 D)
16.17 D
These calculations tell us that the power of the crown glass lens in air is
F
Lens1
= +
16.17 D
and the power of the flint glass lens in air is -10.17 D. To create an achromatic
doublet with a combined power of
+
+
6.00 D, these two lenses are cemented together.
Assume that the plus crown glass lens is equiconvex. What are the radii of curva-
ture of the four lens surfaces?
