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The aperture diaphragm (also called an iris diaphragm) controls contrast, and is found in the condenser, which sits right below the stage in line with the microscope objectives. The condenser may be movable, both in the horizontal and vertical directions.


Condenser Aperture Diaphragm Function On upright microscopes, the condenser is located beneath the stage and serves to gather wavefronts from the microscope light source and concentrate them into a cone of light that illuminates the specimen with uniform intensity over the entire viewfield.


In this post, the function of the condenser aperture diaphragm is explained. The purpose of the condenser is to concentrate the light onto the specimen, its diaphragm regulates resolution, contrast and depth of field. Many modern course microscopes are equipped with a condenser and an associated condenser diaphragm.


Condenser Aperture Diaphragm Control Of Specimen Contrast. The aperture diaphragm acts essentially as a control for resolution and contrast in optical microscopy. By varying the size of the diaphragm opening, the illumination cone projected into the objective is changed.


Condensers typically consist of a variable-aperture diaphragm and one or more lenses. Light from the illumination source of the microscope passes through the diaphragm and is focused by the lens(es) onto the specimen. After passing through the specimen the light diverges into an inverted cone to fill the front lens of the objective.


Köhler Illumination: Interactive Java Tutorials Aperture and Field Diaphragm Adjustment in Reflected Light. This tutorial simulates the operation of a reflected light microscope and allows students to experiment with various settings for the sample focus, field diaphragm iris size and position, and the opening size of the aperture iris diaphragm.


Students may attempt to find the focus with the condenser aperture diaphragm all the way open. This is difficult if the sample is very thin or weakly stained or the microscope is not equipped with parfocal objectives. Remember, an open condenser aperture diaphragm results in a low depth of field.


The tutorial initializes with the field and aperture diaphragms opened about 80-percent of their maximum values. Ray traces are illustrated originating from a focal point in the field diaphragm plane (Image Plane (1)), traveling through the condenser aperture diaphragm and lenses, and converging onto a focal point in the specimen plane (Image Plane (2)).


The numerical aperture of a microscope objective is a measure of its ability to gather light and resolve fine specimen detail at a fixed object distance. Image-forming light waves pass through the specimen and enter the objective in an inverted cone as illustrated in Figure 1. ... Careful positioning of the substage condenser aperture diaphragm ...


Usage notes The aperture of microscopes is often expressed in degrees, called also the angular aperture, which signifies the angular breadth of the pencil of light which the instrument transmits from the object or point viewed; as, a microscope of 100° aperture.