Biomedical Engineering Reference
In-Depth Information
3.14
−
3.14
λ
= 675 nm
(A)
λ
= 635 nm
(B)
rad
2
1
0
10
70
60
50
40
70
30
60
50
20
40
0
30
10
20
10
0
(C)
0
Figure 7.18
3D holographic imaging of cells: (A) phase image at 635 nm, (B) phase image at 675 nm, (C) 3D
pseudo-color rendering of dual-wavelength unwrapped phase image. All images are
78
μ
m
78
μ
m.
3
Figures 7.18 and 7.19
show the phase images of actual cells, acquired by our digital
holographic microscope. Examining single wavelength images in
Figure 7.18A and B
, one
could determine that the maximum value of
m
2
could be set to 2, since the height map
clearly does not extend beyond two wavelengths. By applying the linear regression method,
the final unwrapped image free of discontinuities (
Figure 7.18C
) is obtained.
Λ
Finally, while the object in
Figure 7.19
is twice the height of the synthetic wavelength
12
,
it is still unwrapped correctly. Therefore, there is generally no need to use three or more
wavelengths
[12]
, as adding more wavelengths complicates the optical system and can
actually lead to higher noise due to misalignment.
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