OPTIKA MICROSCOPES B-500DK Manual De Instrucciones página 5

2.0 PRINCIPLES OF IMMERSION MICROSCOPY
Modern substage condensers often have a high degree of correction with numerical aperture values
ranging between 1.0 and 1.40. In order to effectively utilize all the benefits of oil immersion, the in-
terface between the substage condenser front lens and the underside of the microscope slide con-
taining the specimen should be also be immersed in oil. An ideal system is schematically diagramed
in Figure 2, where immersion oil has been placed at the interfaces between the objective front lens
and the specimen slide and also between the front lens of the condenser and the underside of the
specimen slide.
This system has been termed a Homogeneous Immersion System and it is the ideal situation to
achieve maximum numerical aperture and resolution in an optical microscope.
In this case, the refractive index and dispersion of the objective front lens, immersion oil, substage
condenser front lens, and the mounting medium are equal or very near equal.
In this ideal system, an oblique light ray can pass through the condenser lens and completely throu-
gh the microscope slide, immersion oil, and mounting medium undeviated by refraction at oil-glass
or mounting medium-glass interfaces.
When using high-power achromat oil immersion objectives, it is sometimes permissible to omit the
step of oiling the condenser top lens. This is because the condenser aperture diaphragm must often
be reduced with lesser-corrected objectives to eliminate artifacts and provide optimum imaging. The
reduction in diaphragm size reduces the potential increase in numerical aperture (provided by oiling
the condenser lens) so the loss in image quality under these conditions is usually negligible.
Figure 2 Homogeneous immersion system
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