Biomedical Engineering Reference
In-Depth Information
Table 4.4
Correction Beneit at Diferent Numerical Apertures
Specimen
Number
NA
Mean
Mean
Mean
Median
S
ini
S
corr
F
sig
F
sig
1
1.2
0.40
0.66
7.88
3.81
0.9
0.62
0.76
2.24
1.37
0.6
0.70
0.82
1.81
1.18
2
1.2
0.47
0.65
7.02
1.78
0.9
0.55
0.73
6.18
1.58
0.6
0.60
0.79
9.02
1.49
3
1.2
0.32
0.72
8.98
5.79
0.9
0.63
0.85
2.16
1.59
0.6
0.78
0.90
1.42
1.33
1.2
0.48
0.84
3.66
2.97
4
0.9
0.60
0.85
2.19
1.98
0.6
0.75
0.92
1.57
1.49
5
1.2
0.46
0.78
12.66
2.28
0.9
0.64
0.87
4.15
1.68
0.6
0.75
0.90
2.32
1.07
6
1.2
0.47
0.77
3.21
2.64
0.9
0.66
0.84
1.71
1.58
0.6
0.76
0.89
1.40
1.29
he measurements indicate signiicant variations of the uncorrected Strehl ratio throughout the
specimen, which could inluence quantitative luorescence measurements in an uncorrected system. We
showed that low-order aberration correction based on the Zernike modes provide signiicant recovery
of signal levels in confocal microscopy and TPM, even if the difraction limit is not restored. For the six
specimens examined, the mean
F
sig
was in the range between 2 and 10 for a correction of the Zernike
modes 5 through 22 at an NA of 1.2. Note that the quoted values refer to frame averages and the factors
in speciic areas might be even higher. It should be pointed out that the set of biological specimens inves-
tigated is necessarily incomplete and diferences between biological specimens can be large. However,
the beneits for these specimens would be highly signiicant in confocal microscopy and TPM since light
budgets are typically tight and eicient use of available photons is crucial to minimize photobleaching
and phototoxic efects (Manders and Cook 1999).
As expected from theory, lower NA systems are less susceptible to aberrations than high NA systems
under otherwise similar conditions. Low-order correction would still provide beneits, even though
the initial aberrations are smaller. he results presented here quantify the beneit of adaptive optics for
biological microscopy and provide the bounds within which these systems must operate.
References
Booth, M., M. Neil, and T. Wilson (2002). New modal wave-front sensor: application to adaptive confocal
luorescence microscopy and two-photon excitation luorescence microscopy.
J. Opt. Soc. Am. A 19
(10), 2112-2120.
———(1998). Aberration correction for confocal imaging in refractive-index-mismatched media.
J.
Microsc. 192
(2), 90-98.
