Biomedical Engineering Reference
In-Depth Information
were measured.by.changing.the.applied.phase.to.the.subzone.N.times.till.the.maximum.was.reached,.
and. the. applied. phase. was. recorded. for. that. particular. subzone.. he. second. method. was. through. a.
reconstruction.of.the.phase.by.noting.that.changing.the.phase.implies.a.focus.shit.in.the.rays.focused.
by. the. .subzone.. It. is. therefore. possible. to. reconstruct. the. appropriate. phase. applied. such. that. all. the.
foci. belonging. to. each. subzone. would. intersect. at. the. focus.. he. former. method. results. in. a. smaller.
RMS. wavefront. error,. although. at. a. cost. of. extra. computation. required. by. changing. and. applying.
N
.
.number.of.phase.changes.to.determine.the.maximum.signal..his.method.was.shown.to.be.successful.
at.improving.the.signal.level.recorded.while.imaging.through.a.slice.of.mouse-brain.tissue.250-450.µm.
in.thickness..An.image.correlation.method.was.used.to.average.the.aberrations.over.the.various.zones,.
thereby.resulting.in.only.one.correction.being.used.over.the.entire.scanned.ield.(45.×.165.µm).
In.a.inal.example.of.the.recent.developments.in.AO,.a.recent.development.utilizing.AO.in.imaging.is.
not.so.much.for.correcting.for.a.good.image.but.rather.for.a.large.scanned.ield.of.view.[86]..In.this.par-
ticular.case,.the.system.was.designed.to.have.a.large.scanned.ield..his.of.course.meant.that.the.image.
quality.was.compromised.by.aberrations.near.the.edges..To.correct.for.this,.Potsaid.et.al..designed.the.
system.from.scratch.using.ray-tracing.sotware,.allowing.for.suicient.aberrations.that.were.corrected.
by. incorporating. AO. rather. than. going. for. broke. with. a. difraction-limited. design.. he. system. was.
called. the. adaptive. scanning. optical. microscope. (ASOM). and. was,. at. one. point,. commercialized. by.
horlabs™.
7.4 conclusion
Adaptive.optics.has.been.used.successfully.in.the.area.of.ophthalmologic.examination.of.the.eye..his.
is.evident.by.the.various.techniques.that.exist.and.use.AO..Some.examples.of.these.techniques.are.the.
AOSLM.and.the.AO-OCT..However,.the.implementation.in.microscopy.is.less.straightforward.as.it.is.
diicult.to.insert.a.wavefront.sensor.within.the.imaging.system..his.can.be.overcome.through.various.
methods.of.deining.an.image.metric.or.by.using.the.backscattered.light.and.detecting.with.a.wavefront.
sensor..he.high.scan.speeds.of.laser.scanning.microscopy.also.mean.that.feedback.and.optimization.
of.the.aberrations.based.on.various.imaging.metrics.are.slower.by.several.orders.of.magnitude..While.
lookup.tables.and.various.algorithms.can.help.speed.up.the.optimization,.recent.research.has.also.indi-
cated.that.as.the.aberrations.induced.are.oten.dependent.on.imaging.depth.rather.than.the.ield,.it.is.
possible.to.implement.a.single.correction.for.a.particular.scanned.area.without.having.to.continually.
change.the.mirror.shape..In.this.manner,.the.demand.on.the.refresh.rate.of.the.DM.can.be.decreased.
references
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