Biomedical Engineering Reference
In-Depth Information
θ
θ
B
x
θ
C
x
θ
Figure 11-6.
A.
The diagram on the left shows the diffraction pattern formed on the
retina when viewing through a small diameter aperture. To its right is an intensity
profile of the diffraction pattern. Peaks represent bright areas and troughs represent
dark areas. The distance from the center of the light peak to the first trough (dark ring)
is often referred to as the radius of Airy's disk and is designated as
θ
.
B.
Two objects
cannot be resolved unless the peaks of the two Airy's disks are separated by at least
the radius of Airy's disk (i.e., the peak of one disk falls on the trough of the other disk).
In this diagram, where the retinal images are separated by the distance
x
, the radii of
the Airy's disks are too large to allow resolution.
C.
For a larger pupil size, the radii
of the Airy's disks are smaller. Here, the peak of one disk falls on the first trough of the
other disk; therefore, resolution is not limited by diffraction.
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