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Unformatted text preview: Differential Interference Contrast (Nomarski) Microscopy 3 In a Differential Interference Contrast (DIC) or Nomarski microscope, the fraction of the power (intensity) transmitted through crossed polarizers at any point in the image is given by the transmittance T = I out I in = sin 2 Γ 2 where Γ is the phase retardation for that point in the image as viewed between the crossed polarizers. The phase retardation is given by Γ = Γ bias + 2 π λ Δ nL where Γ bias is the bias phase retardation, Δ n is the refractive index difference for the two orthogonally polarized rays in the DIC microscope, and L is the distance over which this difference occurs. Phase retardation has the units of radians. The optical path dif- ference ( o.p.d. ) or retardation, R , is given by o.p.d. = R = Δ nL and has the units of length. A particular DIC microscope has a modified Wollaston beam splitter that pro- duces a lateral displacement (shear) of 0 . 25 μm between the two orthogonally polarized beams. The resolution of the objective used is 0beams....
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- Spring '08
- Wavelength, differential interference contrast, phase retardation