Biomedical Engineering Reference
In-Depth Information
Table 4.3
Correction Beneit for Diferent Degrees of Correction
Specimen
Number
Correction
Up to mode
Mean
Mean
Mean
Median
S
ini
S
corr
F
sig
F
sig
1
12
0.40
0.49
4.47
1.80
18
0.40
0.54
5.50
2.24
22
0.40
0.65
7.57
3.48
37
0.40
0.66
7.88
3.81
2
12
0.47
0.51
4.00
1.10
18
0.47
0.58
6.13
1.38
22
0.47
0.62
6.27
1.63
37
0.47
0.65
7.02
1.78
3
12
0.32
0.52
5.30
2.90
18
0.32
0.57
6.35
3.36
22
0.32
0.65
7.84
4.39
37
0.32
0.72
8.98
5.79
4
12
0.48
0.63
2.15
1.86
18
0.48
0.78
3.13
2.58
22
0.48
0.81
3.35
2.76
37
0.48
0.84
3.66
2.97
5
12
0.46
0.59
7.31
1.29
18
0.46
0.60
7.13
1.39
22
0.46
0.71
9.65
1.98
37
0.46
0.78
12.66
2.28
6
12
0.47
0.58
1.83
1.47
18
0.47
0.62
2.11
1.69
22
0.47
0.72
2.80
2.27
37
0.47
0.77
3.21
2.64
denoted by the numbers listed in
Table 4.2
. Signiicant spatial variations of the initial Strehl ratio are
evident in all specimens. It is important to note this phenomenon. he measured intensity displayed in
a standard CFM image is normally regarded as a quantity that represents luorophore concentration.
he results of this study indicate that aberrations, and not just the luorophore concentration, afect the
measured intensity. his has important implications for quantitative luorescence microscopy.
We note that in some cases the specimen does not ill the whole ield of view and
F
sig
is smaller in the
areas adjacent to the specimen. he calculated mean
F
sig
was typically in the range between 2 and 10 for
a correction of the Zernike modes 5 through 22. he median value is listed as this tends to be less sensi-
tive to extreme values.
4.15 Effect of the Numerical Aperture on Aberrations
Another aspect investigated was the efect of the NA on the size of the aberrations and the beneit of
modal adaptive correction. Wavefront data for diferent NAs can be extracted from the interferograms
by analyzing an aperture subregion of smaller radius. Our data sets were recorded with a physical NA of
1.2 and data analysis was performed for the NAs 1.2, 0.9, and 0.6 for a correction up to Zernike mode 37;
the results are shown in
Table 4.4
(see
Table 4.2
for specimen numbers). he magnitude of aberrations,
especially higher orders, increases with NA. As an example, the phase function corresponding to spheri-
cal aberration (Booth and Wilson 2000; Török et al. 1995a,b) rises sharply toward the edge of a high NA
