Biomedical Engineering Reference
In-Depth Information
Specimen number
N
Initial Strehl
Corrected Strehl
Signal factor
Initial Strehl
Corrected Strehl
Signal factor
0
1
0
1
0
Max
0
1
0
1
1
Max
N
=
1
N
=
4
Max
=
10
Max
=
5
N
=
2
N
=
5
Max
=
5
Max
=
20
N
=
3
N
=
6
Max
=
10
Max
=
5
Signal factor distribution
N
=
1
N
=
2
N
=
3
N
=
4
N
=
5
N
=
6
40
60
50
40
30
70
50
40
30
20
10
0
25
20
60
30
30
20
10
0
20
15
10
5
0
15
10
5
0
20
10
0
20
10
0
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
Figure 4.18
Maps of the initial Strehl ratio
S
ini
, the Strehl ratio
S
corr
ater correction up to Zernike mode 22, and
the derived signal correction factor
F
sig
. he distribution of
F
sig
is shown in a histogram for each of the specimens.
he nonuniform histogram intervals are A:[0, 1.5); B:[1.5, 3); C:[3, 5); D:[5, 10); E:[10, 40); and F: [40, ∞]. he vertical
axis shows percentage of pixels within the range. he maximum of the range for each
F
sig
plot is shown below the
plot and values larger than this maximum are shown in white.
pupil. Since a lower NA objective accepts only the central portion, the efects of spherical aberration are
correspondingly reduced. he dependence of other, higher-order aberration modes is conceptually simi-
lar. herefore, in a low NA system, the aberrations tend to be smaller in amplitude and the initial Strehl
ratio is correspondingly higher. his is supported by the experimental results. As a consequence, the ben-
eit of correction for lower NA was found to be smaller. For the particular case of the mouse oocyte (speci-
men 2), the mean of
F
sig
for NA = 0.6 is largest but this is because of a few locations with very large values
of
F
sig
. However, the median value of the distribution for NA = 0.6 is lower than that for the higher NAs.
4.16 Discussion and Conclusion
We can conclude that the specimen-induced aberrations lead to reduced signal levels and deterioration
in image quality in optical microscopy, especially in confocal microscopy and two-photon microscopy
(TPM). he specimen-induced aberrations that occur with various biological specimens have been clas-
siied and quantiied for the most relevant condition of high NA. he above approach provides detailed
information about the variation of each Zernike coeicient across the scan. Our calculation of the cor-
rection beneit is based on the assumption that a correction would be applied at every position within
the scanned area. he feasibility of this assumption depends on the bandwidth of the wavefront sensing
and correction devices and the scan speed. In some cases, it may be required to either reduce the scan
speed or update the aberration correction every few pixels only.
