chapter  17
14 Pages

Nanophotonics.for.Biomedical.Superresolved.Imaging

The. resolution. of. every. imaging. system. is. limited. by. the. diffraction. spot. size. that. equals.λ/(2. NA),.where.λ.is.the.optical.wavelength.and.NA.is.the.numerical.aperture.of.the.lens..This.limit.is. obtained.due.to.the.wave.nature.of.light,.and.it.is.considered.as.an.unsurpassable.bound.for.most. practical.cases..Nevertheless,. the.resolution.limit. is.obtained.under.certain.assumptions,.such.as. source.monochromaticity,.unpolarized.light,.short.time.imaging,.and.so.on..In.fact,.for.many.practical.situations,.additional.a.priori.information.can.assist.in.surpassing.the.classical.resolution.limit.. This.assertion.is.supported.by.the.classical.works.of.Toraldo.di.Francia.and.Luckosz.[1-3],.describing.a.system.by.the.numbers.of.degrees.of.freedom.it.can.transmit,.instead.of.the.space-bandwidth. product..Later.on,.the.signal-to-noise.ratio.(SNP).of.the.image.was.also.included.in.the.computation. [4]..Thus,.owing.to.the.invariance.of.the.information.throughput.of.a.system,.the.spatial.resolution. of.a. system.can.be.enhanced,.at. the.expense.of.other.degrees.of. freedom.[5]..As.examples,. the. resolution. in.one.axis.can.be.enhanced.by.sacrificing. the. resolution.on. the.orthogonal.direction. [2,6],.or.the.two.orthogonal.polarizations.can.be.used.for.doubling.the.resolution.in.the.case.of.a. polarization-independent.object.[7]..Methods.based.on.extrapolation.of.the.spectrum.(e.g.,.[8]).try. to.squeeze.the.SNR.degree.of.freedom.[5].