initial d street stage manual transmission

The low transmission polarizing filters are useful for DIC observation using the 10x and 20x objectives, but severely restrict light transmission at higher magnifications. At the upper end of the magnification range (40x, 60x, and 100x), polarizers with high transmission efficiencies are preferred for DIC because specimen details are more clearly delineated and larger bias retardation values can be utilized for video and digital imaging. The polarizers employed in DIC microscopy are similar or identical to those used for polarized light observations, but many manufacturers offer matched DIC polarizing filters that have both low and high light transmission efficiencies. Finally, the linear polarized light components that emerge from the analyzer recombine through constructive and destructive interference at the image plane in the eyepiece diaphragm (or camera projection lens). The objective Nomarski prism recombines sheared and deformed wavefronts into linear and elliptically polarized light that subsequently passes a component through the analyzer (a second polarizer oriented perpendicular to the substage polarizer) located in an intermediate tube above the objective. Light waves gathered by the objective converge at the rear focal plane where a second Nomarski prism is located. The perpendicular, sheared wavefronts are focused by the condenser lens system into parallel bundles that traverse the specimen plane and respond to refractive index and thickness gradients by deformation according to optical path length parameters of the specimen. A compound Nomarski or Wollaston prism is located in or near the condenser aperture (front focal plane), and serves to align and shear incident polarized wavefronts into two orthogonal components. Semi-coherent wavefronts emitted from localized neighborhoods in the lamp filament pass through a linear polarizer positioned between the light port in the microscope base and the condenser assembly. Presented in Figure 1 is the typical optical train configuration for a transmitted differential interference contrast microscope. Termed Wollaston or Nomarski prisms, these optical beamsplitters (and beam combiners) are positioned to project interference patterns of sheared wavefronts into the condenser front focal plane and the objective rear focal plane. In the standard configuration, a differential interference contrast microscope (see Figure 1) contains the polarizing elements typically encountered on a polarized light microscope and, in addition, two specially constructed birefringent compound prisms. All of the major microscope manufacturers produce DIC accessories for their research-level microscopes, and these are often bundled together as matched kits containing all of the required hardware and optical components.

Initial d street stage manual transmission