Biomedical Engineering Reference
In-Depth Information
1
1
Corrected
Uncorrected
0.8
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0
0
0
2
4
6
8
0
5
10
15
X distance (µm)
A
B
C
Z distance (µm)
D
(a)
(b)
FIGuRE 10.1
Examples.of.the.correction.of.aberrations.in.multiphoton.microscopes.using.sensorless.adaptive.
optics..(a).hird.harmonic.generation.images.of.a.5.5-day-old.live.mouse.embryo.with.correction.of.only.system.
aberrations. (
let
). and. ater. additional. correction. of. specimen-induced. aberrations. (
right
).. he. dashed. lines. show.
where.the.
xy
.and.
xz
.planes.intersect..Also.shown.are.intensity.proiles.along.the.solid.lines.AB.and.CD.as.drawn.in.
the.images..(Reproduced.from.Jesacher.et.al.,.
Opt. Lett.
,.34,.20,.3154-3156,.2009.).(b).Two-photon.excitation.luo-
rescence.images.of.a.mouse.embryo:.upper,.before.correction;.lower,.ater.correction)..(Reproduced.from.Débarre.
et.al.,.
Opt. Lett.
,.34,.16,.2495-2497,.2009.)
region. of. the. specimen.. As. most. wavefront. sensors. have. no. mechanism. for. discriminating. between.
in-focus.and.out-of-focus.light,.the.sensor.readings.can.be.ambiguous..For.this.reason,.most.adaptive.
microscope.systems.have.“sensorless”.AO.systems,.in.which.the.correction.aberration.is.inferred.from.a.
collection.of.image.measurements,.where.each.image.is.acquired.with.a.diferent.aberration.introduced.
by.the.adaptive.element..We.refer.to.these.additional.aberrations.as.bias.aberrations..As.in.any.AO..system,.
the.goal.of.a.sensorless.AO.system.is.to.ind.a.DM.shape.that.cancels.all.other..aberrations.in.the.system.
or. at. least. reduces. them. to. an. acceptable. level.. he. sensorless. AO. scheme. must,. therefore,. be. able. to.
.determine.from.a.set.of.aberrated.images.what.the.optimal.correction.aberration.is.or,..equivalently,.what.
the.system.aberration.is..We.explore.the.principle.behind.this.approach..We.also.describe.the..methods.
that. can. be. used. to. design. eicient. sensorless. adaptive. schemes. by. appropriate. choice. of. .aberration.
modes.
10.2 indirect Wavefront Sensing
As. aberrations. afect. the. imaging. quality. of. a. microscope,. some. information. about. the. nature. of. the.
aberrations.must.be.encoded.in.the.images..herefore,.one.should.expect.that.some.of.this.information.
could.be.extracted.indirectly.from.an.aberrated.image.or,.more.readily,.from.a.collection.of.aberrated.
images..his.is.the.principle.behind.sensorless.AO.
Mathematically,.an.image.is.a.function.of.both.the.object.structure.and.the.imaging.properties.of.
the.microscope..For.example,.in.the.case.of.a.confocal.luorescence.microscope.(an.incoherent.imaging.
