Microscopy - Operation of a Brightfield Microscope

The goal of microcopy is to create a magnified image of objects too small to be seen with the eye alone.

Brightfield microscopes use a combination of glass lenses and light to view the specimen.

Microscopes are often used to study bacteria, cells, and tissues.

Fields of study where a microscope is a necessary tool include:

• Cytology

• Histology

• Pathology

There are three factors that determine the quality of a microscopic image:

• Magnification is the apparent increase in image size.

• Resolution is the ability to distinguish fine detail

• Contrast refers to the ability to distinguish objects, such as cells, from the background.

The microscope you are using has four objective lenses to magnify the image: 4X, 10X,40X, and 100X. When focusing on a slide, start on the scanning, or low power, objective lens. The lower the power objective, the greater the field of view. The field of view is the amount of the slide you’re able to see through the eyepiece.

Total magnification is the overall enlargement of the image of a specimen. To calculate total magnification, multiply the magnification of the ocular lens (10X) with the magnification of the objective lens.

Often what you want to visualize is not in the middle of the field of view and you must move the slide around to find what you want to study. To move the slide, you move the stage. As you look at the microscope the stage knob on the top moves the stage forward and back. The stage knob on the bottom moves the stage side to side.

Additional adjustments to the microscope can be made regarding the lighting.

• As magnification of the image increases, the light intensity decreases and will have to be adjusted.

• The condenser lends focuses the light on the side.

• The sliding bar on the condenser lens is the aperture. As you move the aperture to decrease the light to the slide, the contrast increases. As you move the aperture to increase the light to the slice, the contrast decreases.