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Hoffman Modulation Contrast Microscopy

Hoffman modulation contrast is an oblique illumination technique that enhances contrast in both stained and unstained specimens by detection of optical phase gradients. This section includes discussions of transmitted and reflected light applications using Hoffman modulation contrast and links to interactive Java tutorials designed to aid in understanding the technique. Also included are virtual microscopes and an image gallery of photomicrographs made using modulation contrast either alone or in combination with other illumination mechanisms.

Hoffman Modulation Contrast Basics - This section introduces the basic concepts in modulation contrast microscopy with numerous illustrations and examples of how the technique is implemented. Links to interactive Java tutorials help to aid the student in understanding complex topics that are difficult to grasp using only text and figures.

Troubleshooting Hoffman Modulation Contrast - Problems with proper slit alignment between the condenser and the objective modulator are the most common source of errors with modulation contrast microscopy. These and other problems are discussed along with suggested remedies.

Interactive Java Tutorials

Optical Sectioning - The ability to focus on a single plane within a specimen without interference from objects above and below is a key feature of Hoffman modulation contrast. This interactive Java tutorial simulates a virtual microscope that provides several examples of specimens in optical section while passing through focus using modulation contrast illumination.

Slit and Modulator Alignment - Aligning the condenser slit with the objective modulator plate is one of the most critical aspects of microscope configuration for Hoffman modulation contrast. Use this interactive Java tutorial to practice this simple, yet often misunderstood, alignment technique.

Image Contrast Adjustment - Hoffman modulation contrast is an oblique illumination technique that allows microscopists to enhance contrast in semi-transparent phase objects, which are difficult to image using conventional brightfield microscopy. This interactive tutorial explores how rotation of the substage polarizing filter affects image contrast in Hoffman modulation contrast microscopy.

Digital Image Gallery

Hoffman Modulation Contrast Image Gallery - Modulation contrast illumination produces a pseudo three-dimensional effect that can be used in combination with other illumination techniques to achieve spectacular images.

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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