Biomedical Engineering Reference
In-Depth Information
2
(1.498
−
1.000)
⎡
⎥
⎤
⎥
=
(b)
R
(1.498
+
1.000)
R
=
0.04
Percentage reflected is 4.0%.
(c) The higher index lens because more light is reflected by its surface.
(d)
n
c
=
√
n
L
n
c
= √1.74
n
c
= 1.32
CHAPTER 15
Aberrations
1. (a) Due to positive spherical aberration, the subject will see two point images.
(b) When the subject occludes the top hole, the upper image disappears. The
rays entering the top hole are focused on the inferior portion of the retina
and are seen as the upper image.
2. No, because Seidel aberrations are present in spherical optical systems.
3. (a) If we ignore the thickness of the lens, we can assume that both the front
and back surfaces of the lens have a power of
+
2.50 DS. The radius of cur-
vature for the front surface is
(
n
′
−
n
)
=
F
r
(1.50
−
1.00)
F
+
2.50 DS
=
r
= +
r
2.50 m or
+
20.00 cm
Therefore
r
1
=
+
20.00 cm and
r
2
=
−
20.00 cm.
(
r
2
+
r
1
)
σ
=
(
r
2
−
r
1
)
(
−
20.00 cm
+
20.00 cm)
σ
=
(
−
20.00 cm
−
20.00 cm)
σ
=
0
(b) Approximately plano-convex.
(c) The front surface should be convex and the back (ocular) surface should be
plano.
