Biomedical Engineering Reference
In-Depth Information
(a)
(e)
Microscope
Microscope
L
(b)
(f)
Signal
Microscope
Microscope
Phase of L
R
(c)
(g)
Signal
Microscope
Microscope
Phase of R
(d)
(h)
Microscope
Microscope
FIGuRE 13.3 Schematics. illustrating. the. pupil-segmentation-based. AO. approach. using. three. subregions,.
.represented.by.three.beamlets..(a).Aberrated.wavefront.leads.to.an.aberrated.image..(b-d).Images.acquired.with.
the.let,.center,.and.right.subregions.illuminated,.respectively,.allow.the.tilt.of.each.beamlet.to.be.measured.from.
the displacement.of.the.image..(e).Beamlets.intersect.at.a.common.point,.ater.proper.phase.gradients.are.applied.
at.the.SLM.to.steer.each.beam..(f).Let.beamlet.interferes.with.central.reference.beamlet,.determining.the.optimal.
phase.ofset.(dashed.vertical.line)..(g).he.same.procedure.is.used.for.the.right.beamlet..(h).Final.corrected.wave-
front.and.recovered.difraction-limited.focus.provide.an.aberration-free.image..If.phase.reconstruction.is.used,.the.
phase-measurement.steps.(f.and.g).are.skipped..(Ji,.N.,.et.al.,. Nat. Meth .,.7,.2,.141-147,.2010.).
images.(the.direct.approach.requires.6N.images.for.N.pupil.subregions—N.images.for.beam.delection.
measurement.and.5N.images.for.the.itting.of.interference.curves—whereas.the.phase-reconstruction.
method.needs.N.images.for.N.pupil.subregions).
he.above.pupil-segmentation.approach.is.zonal.by.nature,.reminiscent.of.a.Shack-Hartmann.sensor.
in.that.it.divides.the.wavefront.into.zones.and.measures.the.local.wavefront.tilt.of.each.zone.by.image.
shit,.but.without.the.requirement.for.a.transparent.sample..Similar.to.the.Shack-Hartmann.sensor,.it.
works.well.with.point.sources.or.sparsely.labeled.structures..However,.by.illuminating.one.pupil.seg-
ment.at.a.time,.each.image.is.taken.under.a.much.lower.NA..he.resulting.increase.in.the.focal.volume.
of.the.excitation.light,.in.particular.the.increase.in.its.axial.extent,.causes.a.problem.in.densely.labeled.
samples—the.luorescent.structures.that.are.originally.outside.the.excitation.volume.under.full-pupil.
illumination.now.contribute.to.the.images.taken.at.diferent.pupil.segments,.and.thus.may.make.image.
shit.measurement.diicult.
 
 
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