Biomedical Engineering Reference
In-Depth Information
To.correct.sample-induced.aberrations.across.the.entire.ield.of.view,.the.light.must.travel.through.an.
“inverse.sample,”.as.shown.in.Figure.15.10,.so.that.the.accumulated.phase.distortions.along.each.ray.are.
reversed..he.inverse.sample.has.the.same.structure.as.the.sample.but.with.the.refractive.index.difer-
ences.reversed..his.inverse.sample.can.be.calculated.from.DIC.image.stacks,.and.could,.in.principle,.be.
constructed.with.photorefractive.materials,.but.this.would.be.diicult.to.say.the.least.
An.approximation.of.an.inverse.sample.can.be.constructed.by.multiconjugate.adaptive.optics.(MCAO).
where.multiple.adaptive.elements,.conjugate.to.diferent.planes.in.the.sample,.are.used.to.approximate.
the.inverse.sample.(Ragazzoni.et.al..2000;.Ragazzoni.et.al..2002)..In.
Figure.15.11
,.we.show.the.results.
(a)
Inverse
sample
Sample
Relay
lenses
Aberrated
image
Tube
lens
Corrected
image
Source
(b)
Multiconjugates
Sample
Relay
lenses
Aberrated
image
Tube
lens
Corrected
image
Source
FIGuRE 15.10
Schematic. optical. setup. for. correcting. sample-induced. aberrations. (Kam. et. al.. 2007).. he. sample. is.
simulated.by.a.set.of.ellipsoids.with.a.refractive.index.diferent.from.the.embedding.medium..Ray.tracing.is.performed.
through.the.sample.volume,.followed.by.the.correcting.optics..In.(a),.the.correction.is.performed.by.a.hypothetical.“inverse.
sample”.with.the.identical.distribution.of.ellipsoids.but.with.the.opposite.refractive-index.contrast..In.(b),.the.inverse.
sample.is.approximated.by.three.adaptive.elements,.shiting.the.phases.of.rays.that.pass.through.them.(Kam.et.al..2007).
