Biomedical Engineering Reference
In-Depth Information
3.14
−
3.14
λ
= 675 nm
λ
= 635 nm
(A)
(B)
rad
2
0
72
70
60
50
40
70
30
60
50
20
40
0
30
10
20
(C)
10
0
0
Figure 7.19
Two KB cells (marked) with a substrate inserted at an angle: (A) phase image at 635 nm,
(B) phase image at 675 nm, (C) dual-wavelength unwrapped phase image. All images are
78
μ
m
78
μ
m.
3
7.5 Conclusions
Phase unwrapping of biological cell images presents several challenges. While the cells are
typically positioned on a flat substrate, which can be used as a reference for the unwrapping
algorithm, the various cells organelles often scatter most of the light, so no coherent signal
can be obtained from some parts of an image frame. As a result, these areas often become
the source of unwrapping errors, which propagate to the other parts of the image as well.
By using the varying reconstruction distance algorithm, we can effectively bypass the areas
of phase noise and unwrap the cellular phase images “layer by layer.” Also, the cell
membrane is sometimes oriented almost perpendicularly to the substrate, resulting in
sudden vertical changes in the height of an object, which cannot be correctly unwrapped
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