Biomedical Engineering Reference
In-Depth Information
(Porter.2006)..he.aberrations.in.biological.specimens.vary.from.specimen.to.specimen,.as.discussed.
in.Chapter.4..Here.phase-stepping.interferometry.has.been.used.to.measure.wavefront.aberrations.in.
diferent. biological. specimens.. he. stroke. requirements. for. biological. imaging. are. currently. met. by.
low-stroke. MEMS. DMs;. however,. larger. stroke. will. become. necessary. for. imaging. more. deeply. into.
tissue.samples.for.correction.of.aberrations.that.increase.with.the.optical.path.length,.such.as.spherical.
aberration.that.arises.due.to.mismatches.between.the.lens,.the.immersion.media.(e.g.,.water.or.index.
matching.oil),.and.the.sample..Here.either.large-stroke.DMs,.or.woofer-tweeter.mirror.combinations,.
will. be. required.. A. signiicant. fraction. of. the. stroke. in. an. MEMS. continuous. facesheet. DM. can. also.
be.used.up.for.correction.of.the.microscope.optics.and.optical.alignment,.even.before.using.stroke.for.
correction.of.specimen-induced.wavefront.aberrations..An.additional.portion.of.the.stroke.will.also.be.
used.to.latten.the.DM.if.it.has.residual.deformations.from.stress.and.stress-gradients.that.arise.during.
manufacture.and.packaging.of.the.mirror.
8.10 Microelectromechanical System Mirror Solutions
A.number.of.the.MEMS.mirror.component.suppliers.have.either.ofered.their.own.MEMS.AO.optical.
systems.or.partnered.with.larger.optical.companies.to.ofer.full.AO.systems.including.both.MEMS.DMs.
and.wavefront.sensors.
Boston.Micromachines.has.partnered.with.horlabs.to.ofer.an.AO.kit.that.includes.a.DM,.32.actua-
tors. or. 140. actuators,. a. Shack-Hartmann. wavefront. sensor,. intervening. imaging. optics. (collimation.
and. relay. optics),. and. stand-alone. control. sotware.. he. sotware. is. capable. of. minimizing. wavefront.
aberrations.by.analyzing.the.signals.from.the.Shack-Hartmann.wavefront.sensor.and.using.those.sig-
nals.to.determine.the.appropriate.drive.signals.to.send.to.the.DM.actuators..he.mirror.can.then.com-
pensate. for. the. measured. wavefront. aberrations.. he. control. sotware. allows. the. user. to. monitor. the.
wavefront.corrections.and.intensity.distribution.in.real.time..In.addition,.user-deined.aberrations.can.
Objective
pupil
Deformable mirror
Sample
L1
Objective
Tube lens
Primary image
plane
L2
Pupil conjugation
plane
CCD
Secondary image
plane
FIGuRE 8.42
he.MicAO.system.from.Imagine.Optics..he.system.is.an.afocal. system,.which. consists.of.two.
identical.lenses.(L1,.L2)..he.distances.between.the.deformable.mirror.(DM).and.the.lenses.are.equal.to.the.focal.
length.of.the.lenses.(
f
.)..In.the.same.way,.distances.between.the.primary.and.secondary.image.planes.and.L1.and.L2,.
respectively,.are.also.equal.to.(
f
.)..he.DM.is.positioned.in.the.focal.plane.of.L1,.which.corresponds.to.the.conjugate.
plane.of.the.objective.lens.pupil..he.DM.(mirao™.52-e.from.Imagine.Eyes).has.52.actuators.controlled.electromag-
netically,.which.provides.high.deformation.dynamics.(up.to.±35.μm.of.focus.on.a.15.mm.mirror.aperture)..(From.
Andilla,.J..and.X..Levecq,.MICAO:.irst.universal.all-in-the-box.adaptative.optics.plug-in.accessory.for.standard.
high.resolution.microscopy..
Imaging, Manipulation, and Analysis of Biomolecules, Cells, and Tissues VIII
,.edited.by.
Daniel.L..Farkas,.Dan.V..Nicolau,.Robert.C..Leif,.
Proc SPIE
..Vol..7568,.75680U1-8,.2010.)
