Biomedical Engineering Reference
In-Depth Information
FIGuRE 8.41
High-stroke,. high-order. MEMS. deformable. mirror. fabricated. in. a. high-aspect-ratio. microma-
chining.process..he.gold.mirror.surface.is.deposited.on.top.of.a.16.×.16.array.of.X-beam.actuators.fabricated.in.
gold.on.a.WMS-15.glass-ceramic.substrate..he.efect.of.the.tensile.stress.in.the.electrodeposited.gold.mirror.layer.
can.be.seen.along.the.edges.where.the.edge.of.the.mirror.appears.to.be.serrated..Rows.of.test.X-beam.actuators.
can.be.seen.outside.the.mirror.area..(From.Fernandez,.B..R..and.J..Kubby,.
J Micro/Nanolitho MEMS MOEMS.
,.9,.
041106-1,.2010.)
on.the.mirror.surface.by.the.support.posts.as.the.mirror.shrinks.to.relieve.tensile.stress.ater.release..
hese.deformations.can.be.decreased.by.decreasing.the.residual.tensile.stress.or.by.applying.more-rigid.
boundary.conditions.along.the.edges.of.the.mirror.
8.9 comparison of Microelectromechanical System Mirrors
An.optical.system.designer.has.a.considerable.number.of.DMs.to.choose.between.that.are.now.available..
here.have.been.some.reviews.comparing.diferent.MEMS.mirror.options.in.vision.science.(Dalimier.
2005;.Daly.2006).and.which.have.also.been.extended.to.applications.in.astronomy.(Devaney.2008)..Both.
segmented. and. continuous. facesheet. MEMS. DMs. have. been. used. in. vision. science,. but. most. imag-
ing.applications.in.astronomy.have.used.continuous.facesheet.mirrors..Nonetheless,.segmented.MEMS.
DMs.have.been.used.for.correcting.the.laser.guide-star.uplink.in.astronomical.AO..he.mirrors.used.in.
vision.science.tend.to.require.a.large-stroke.to.it.a.wide.population.distribution,.but.only.require.low-
order.correction.since.most.of.the.common.vision.science.aberrations.such.as.astigmatism.and.focus.
can.be.corrected.with.low-order.Zernike.modes..Applications.in.astronomy.typically.require.high.order.
for.high-contrast.imaging.(e.g.,.Gemini.Planet.Imager).(Poyneer.2011).but.not.high.stroke..Nonetheless,.
the.need.for.high.stroke.in.astronomy.will.develop.as.larger.diameter.telescopes.are.built.since.they.will.
view.more.of.the.sky.and.thus.require.higher-amplitude.wavefront.correction.
So.far.no.standards.have.been.developed.for.the.application.of.MEMS.DMs.in.biological.imaging..
Similar. to. vision. science,. most. of. the. aberration. in. biological. imaging. occurs. at. lower. order,. so. low-
order.MEMS.DMs.can.be.used.to.correct.most.wavefronts..However,.there.are.no.standard.models.for.
biological. aberrations. as. there. are. now. for. astronomy,. where. the. Kolmogorov. spectrum. is. typically.
used. (Kolmogorov. 1941). or. the. population. distributions. that. have. been. determined. in. vision. science.
