Biomedical Engineering Reference
In-Depth Information
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Figure 7.5
Background removal for simulated cells. (A) Simulated cells on the flat substrate, (B) single
wavelength (635 nm) simulated phase images with added phase, (C) dual-wavelength unwrapped
phase image, and (D) dual-wavelength unwrapped phase image with background removed.
first iteration (dotted line), while removing the original peaks, also “dives” under the
original curved profile near the ends of the frame. As a result (dashed line), the curvature is
overcompensated. However, it can be fixed by modifying the algorithm's step 2 in the
following way:
2a. Compare the polynomial surface with the original image.
2b. Find the maximum difference between the fit and the original profiles.
2c. Add a fraction of that maximum difference to the polynomial surface.
This modification, although making the convergence much slower, does result in a flat
background (see
Figure 7.6
—solid line). The fraction, used in step 2c can be as high as
95% and is limited only by computational rounding error as well as the computational
speed (the higher is the number, the longer it takes for the method to converge). The result
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