Biomedical Engineering Reference
In-Depth Information
PSF
(a)
(c)
(b)
4
3
2
1
10
0
5
- 1
0
y μ m
- 2
- 5
- 3
x μ m
- 10
- 4
Ideal PSF
Calculated PSF
Corrected(14) PSF
1
1
1
0.5
0.5
0.5
0 - 4
0 - 4
0 - 4
- 2
0
x μ m
(d)
2
4
- 2
0
x μ m
(e)
2
4
- 2
0
x μ m
(f )
2
4
FIGuRE 17.10 PSF.analysis..(a).Calculated.using.a.lat.wavefront..(b).Calculated.using.the.wavefront.shown.in.
Figure.17.8 . .(c).Calculated.by.removing.the.irst.14.Zernike.modes.of. Figure.17.8 . .(d).Cross-sectional.view.of.(a)..(e).
Cross-sectional.view.of.(b)..(f).Cross-sectional.view.of.(c).
be.seen.from. Figures.17.8 . and. 17.9 , .astigmatism.and.spherical.aberrations.dominate.the wavefront.error..his.
is.mainly.due.to.the.index.mismatches.in.the.optical.path.and.the.curved.body.of.the.embryo,.which.mostly.
introduced.the.lower-order.aberrations..Note.that.the.optical.aberrations.due.to.the.coverslip.and.air-glass.
interface,.including.tip,.tilt,.and.focus,.have.been.removed.by.the.reference.image..A reassuring.sign.shown.in.
Figure.17.9 . is.that.the.amplitude.of.the.higher-order.aberrations.are.decreasing,.and.therefore,.by.correcting.
a.inite.number.of.Zernike.modes,.the.imaging.qualities.of.the.optical.system.can.be.expected.to.improve..
Note.that.the.spatial.resolution.for.the.wavefront.measurement.setup.for.the.20×.objective.with.a.limiting.
aperture. D .=.5.9.mm.is.the.Zernike.mode.200.so.that.the.decreasing.amplitudes.shown.in. Figure.17.9 . are.not.
an.artifact.of.the.sensor..he.spatial.resolution.of.the.SHWF.sensor.is.directly.proportional.to.the.number.of.
degrees.of.freedom.(i.e.,.the.number.of.subapertures.inside.the.pupil).(Porter.et.al..2006).
Figure.17.10a.shows.the.PSF.for.an.optical.system.with.no.aberrations..Figure.17.10b.displays.the.PSF.
calculated.by.using.Equation.17.5.and.the.wavefront.shown.in. Figure.17.8 ..he.Strehl.ratio.is.deined.
as.the.ratio.of.the.peak.intensity.of.the.PSF.relative.to.the.peak.intensity.of.the.difraction-limited.PSF.
(Porter.et.al..2006)..Figure.17.10e.shows.that.the.Strehl.ratio.is.approximately.0.37..he.efect.of.remov-
ing.the.irst.14.Zernike.modes.can.be.seen.in.Figure.17.10c.and.f..Using.this.simulation,.we.can.estimate.
that.correcting.the.irst.14.Zernike.modes.will.improve.the.Strehl.ratio.to.0.70.
Table.17.1 . shows.the.statistical.data.gathered.from.the.measurements.taken..Each.measurement.comes.
from. diferent. luorescent. microspheres. ranging. in. depth. from. 40. to100.μm. below. the. surface. of. the.
 
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