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Köhler Illumination

Interactive Java Tutorials

We have constructed a variety of Java tutorials designed to help students grasp the fundamental details of Köhler illumination and how a microscope is adjusted for this purpose. Please use the links below to visit the tutorials in our collection.

Condenser Alignment - Learn to align the most important optical components in a microscope with this tutorial. Students can practice centering the condenser and setting the field diaphragm to its optimum size for photomicrography.

Condenser Light Cones - This tutorial explores how changes in the size of the condenser aperture affect the shape and size of the light cone (and numerical aperture) emitted from the condenser.

Condenser Aperture Diaphragm Adjustment - Discover how the aperture diaphragm of the substage condenser can be monitored with a Bertrand lens (or by removing the eyepiece) to optimize numerical aperture, image resolution, depth of field, and overall image quality.

Conjugate Planes - Discover how various conjugate plane sets pass through focus together when a microscope is properly aligned for optimum Köhler illumination.

Condenser Aperture Diaphragm Control Of Specimen Contrast - This tutorial explores how condenser aperture diaphragm opening size affects specimen contrast at medium to high (10x through 100x) magnifications.

Lamp Filament Alignment - Alignment of the lamp filament is one of the first and most crucial steps in achieving proper Köhler illumination. This tutorial explores all of the aspects of adjusting both the voltage and the position of the lamp filament, and ensuring that the filament completely fills the back focal plane of the objective.

Substage Condenser Numerical Aperture - The condenser aperture diaphragm controls the numerical aperture of the optical system of a microscope. This tutorial demonstrates changes in condenser light cones as a function of numerical aperture settings.

Eyepiece Diopter Adjustment - Eyepieces in modern microscopes have both interpupillary and individual diopter adjustments that help adjust the eyepieces for comfort and to correct for near and far sightedness.

Contrast Adjustment At Low Magnifications - Specialized condensers suited for low magnification (5x objectives and less) microscopy rely on the field diaphgram for adjustment of specimen contrast. Some general purpose condensers have a swing-out lens for use with low magnification objectives, and these also rely on the field diaphragm.

Aperture and Field Diaphragm Adjustment in Reflected Light - Reflected light microscopes are adjusted for Köhler illumination in a manner similar to transmitted light microscopes. This tutorial examines how the aperture iris diaphragm is used to vary specimen contrast and image quality, and how the field diaphragm is manipulated for optimum reduction of glare and scattered light.

Reflected Light Illuminators - Discover how light travels through a reflected light illuminator with this interactive Java tutorial.

Contributing Authors

Mortimer Abramowitz - Olympus America, Inc., Two Corporate Center Drive., Melville, New York, 11747.

Kirill I. Tchourioukanov and Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.


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