what is the function of the diaphragm on a microscope

The function of the diaphragm on a microscope is to regulate the amount of light passing through the specimen. The diaphragm is located under the stage and can be adjusted to vary the intensity and size of the cone of light that is projected through the slide. Closing or opening the condenser diaphragm controls the angle of the light rays emerging from the condenser and reaching the specimen from all azimuths. The luminous-field diaphragm determines which portion and size of the specimen is illuminated, and the aperture diaphragm of the condenser is imaged on the pupil of the objective and regulates the illumination of this pupil. The primary function of the diaphragm is to change the angular aperture of the cone of light that is produced after the light travels through the condenser. Depending on the type of diaphragm and the settings applied to the diaphragm, this can have minute but important effects on the quality of the image.