Biomedical Engineering Reference
In-Depth Information
1
0.9
1
0.8
0.8
0.7
0.6
0.6
0.5
0.4
0.4
0.2
0.3
0
0.2
2
2
0.1
0
0
−2
0
−2
0
1
2
3
λ
/
D
FIGURE 1.7
The normalized point-spread function (PSF) of a circular aperture is an Airy disk. Angular units of the hori-
zontal axes (
x
,
y
directions) are radians; to convert from angular to linear units, multiply by the focal length of the lens.
1
0.9
1
0.8
0.8
0.7
0.6
0.6
0.5
0.4
0.4
0.2
0.3
0
1
0.2
1
0.1
0
0
0
−1
−1
0
0.5
1
D
/
λ
FIGURE 1.8
The normalized magnitude of the OTF of a circular aperture. This magnitude is typically abbreviated MTF.
Spatial frequency units of the horizontal axes (
u
,
v
directions) are cycles/radian.
so some authors use the area under the MTF
curve as a figure of merit. However, this is often
too simple an approach, and a more application-
specific comparison of MTFs may be warranted.
Each PSF in the spatial domain for each com-
ponent of an optical system is associated with
an MTF in the spatial frequency domain, and
the MTFs are all combined into an overall MTF
