Biomedical Engineering Reference
In-Depth Information
hese.partitions.are.not.entirely.arbitrary..In.the.irst.group,.there.are.the.low-order.aberrations.that.
dominate. many. optical. microscopy. systems,. including. astigmatism. and. coma.. In. the. second. group,.
there. is. the. irst-order. spherical. aberration. that. is. expected. to. be. particularly. relevant. to. subsurface.
imaging..In.the.third.group,.there.are.higher-order.aberrations,.including.the.second-order.spherical.
aberration,.that.deine.the.highest.relevant.spatial.frequency.that.is.controllable.with.the.DM.
12.4 optical System Design
he. irst. TPSL-FM. was. pioneered. by. Denk. and. Webb. [36].. he. noninvasive. imaging. technique. has.
been.used.in.an.exponentially.increasing.number.of.applications.in.recent.years.for.biomedical.imaging.
[37-46].
Figure.12.7.shows.the.actual.optical.layout.of.the.BU-Wellman.Center.for.Photomedicine.two-photon.
luorescence. imaging. system. with. AO. and. the. optical. system. magniication.. he. constructed. optical.
system.occupies.1.5X1.square.meters.optical.bench..he.apparatus.includes.four.main.components:.the.
light.source,.raster.scanning,.light.detection,.and.wavefront.correction.
Due.to.the.nonlinear.nature.of.the.luorescence.excitation,.a.high-power.illumination.laser.density.is.
essential.for.the.practical.two-photon.microscope.setup..In.practice,.a.pulsed.laser.can.provide.a.factor.
of.
10
4
.or.
10
5
.times.more.luorescence.excitation.than.a.continuous.wave.laser.with.the.same.amount.of.
average.power,.due.to.the.temporal.focusing.
Light.is.delivered.from.a.solid-state.mode-locked.Ti-sapphire.laser.and.an.optical.parametric.oscil-
lator. with. a. combined. tuning. range. from. 700. to. 1300. nm. (Newport. Corp.,. CA).. Laser. power. varies,.
depending.on.the.output.wavelength..For.example,.at.920.nm,.the.laser.is.capable.of.providing.up.to.
1.3 W.output.power..he.pulse.width.is.100.fs,.with.a.repetition.rate.of.80.MHz..A.pair.of.linear.rotatable.
polarizers.was.installed.to.perform.beam.intensity.control.at.the.output.of.the.laser..he.constructed.
system.has.a.throughput.of.7%..he.maximum.power.that.can.be.reached.at.the.surface.of.biological.
sample.is.close.to.100.mW.
he.entrance.pupil.is.deined.by.the.MEMS.DM.(Boston.Micromachines,.MA)..he.MEMS.DM.has.
clear. aperture. of. 4.8.×. 4.8. mm. occupied. by. the. 12.×. 12. actuator. array.. To. create. precise. Zernike. term.
L1
L2
M1
L3
L8
Objective
M3
M2
DM
L4
L7
Polygon
scanner
Galvanometer
scanner
L6
L5
y
z
L3
L8
L2
L6
L7
L4
L1
L5
Polygon
scanner
DM
Galvanometer
scanner
Objective
FIGuRE 12.7
he.optical.layout.of.two-photon.scanning.laser.luorescence.microscope.with.adaptive.optics..Top:.
the.design.model.in.ZEMAX..Bottom:.the.system.magniication.of.the.lens.system,.shown.unfolded..Lens:.L1-L8..
Mirror:.M1-M3.
