what does the iris diaphragm do on a microscope

The iris diaphragm is an important component of a compound microscope that controls the amount of light that passes through the specimen and the condenser. It is located just below the stage and above the condenser, and it can be adjusted to change the size of the opening between the specimen and the condenser, which controls the amount of light that reaches the specimen. By opening or closing the iris diaphragm, the user can adjust the amount of light that passes through the specimen, which can help to improve the contrast and clarity of the image. The iris diaphragm is also sometimes referred to as the luminous-field diaphragm, and it determines which portion and size of the specimen is illuminated. The aperture diaphragm of the condenser is imaged on the pupil of the objective and regulates the illumination of this pupil. In summary, the iris diaphragm controls the amount of light that passes through the specimen and the condenser, which can help to improve the quality of the image.