Phase Contrast Microscopy
Interactive Java Tutorials
Apodized Phase Contrast
In apodized phase contrast microscopy, halo attenuation and an increase in specimen contrast can be obtained by the utilization of selective amplitude filters located adjacent to the phase film in the phase plates built into the objective at the rear focal plane. These amplitude filters consist of neutral density filter thin films applied to the phase plate surrounding the phase film as illustrated in the tutorial window.
Illumination from the light source passes through a hypothetical spherically-shaped specimen (phase object), whose size is adjustable with the Specimen Size slider. The tutorial initializes with the specimen set to the smallest size (the left-hand side) by the slider. As the thickness of the specimen is increased by moving the slider to the right, the phase difference between the specimen and the surrounding medium increases and the angle of light diffracted by the specimen becomes smaller. This diffracted light passes through an apodized phase plate (located in the rear focal plane of the objective) that contains two neutral density filter rings having a 50% transmittance value. The width of the apodization absorption rings is based on the diffraction angle according to the calculation:
sin(q) µ 1/d
Where q is the angle of diffraction and d is the phase difference between the specimen and the surrounding medium. Contrast is controlled by the transmittance of both the apodized (50% transmittance) and the DL phase (25% transmittance) rings. Most of the light diffracted through large specimens passes through these phase rings, while much of the light diffracted through small specimens occurs at higher angles and passes through transparent portions of the phase plate. Light passing through the phase plates is attenuated and is represented by a decrease in color saturation for the arrows and waves in this tutorial.
Mortimer Abramowitz - Olympus America, Inc., Two Corporate Center Drive., Melville, New York, 11747.
Matthew J. Parry-Hill and Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.
BACK TO PHASE CONTRAST MICROSCOPY
BACK TO SPECIALIZED TECHNIQUES
Questions or comments? Send us an email.
© 1995-2013 by
Michael W. Davidson
and The Florida State University.
All Rights Reserved. No images, graphics, software, scripts, or applets may be reproduced or used in any manner without permission from the copyright holders. Use of this website means you agree to all of the Legal Terms and Conditions set forth by the owners.
Last modification: Wednesday, Mar 26, 2014 at 02:23 PM
Access Count Since November 10, 2000: 14483
For more information on microscope manufacturers,
use the buttons below to navigate to their websites: