Parts of the Microscope



A. Identify and familiarize yourself with the following parts of the microscope and their functions:


1. Power switch - turns the lamp on and off

2. Illumination control

i. controls the brightness of the lamp

ii. on most microscopes it is a continuously variable rheostat, controlled by a sliding switch

3. Illuminator

a. consists of a lamp bulb and one or more lenses to produce a cylindrical beam of light directed toward the base of the condenser

b. may have a ground glass - a frosted sheet of glass that scatters the light from the lamp bulb to provide more diffuse light

c. may have an iris diaphragm, called the field diaphragm

i. controls the diameter of the illuminating beam of light

ii. used as a guide to focus the light from the condenser onto the specimen

4. Condenser - contains a set of lenses that focus the light on the specimen. The condenser has the following components:

a. focusing knob - moves the condenser up and down to adjust the focus of the light on the specimen

b. front lens - the glass surface closest to the specimen. Be careful not to touch this surface as it is easily scratched.

c. iris diaphragm

i. controls the aperture of the illuminating light

ii. used to adjust contrast

d. filter holder

i. located at the base of the condenser

ii. allows insertion of a filter (usually blue) to adjust the color of the illuminating light

5. Revolving nosepiece - holds several objective lenses that can be rotated into position to change the lens

6. Objective lenses - create a magnified image of the specimen

a. 4x lens - used to get an overview of the structures present in o a section and to find areas for more detailed observation

b. 10x lens - the most useful magnification to identify tissues

c. 40x lens - used to see the details of cell and tissue organization

d. 100x lens - because it requires the use of immersion oil, is used primarily to see subcellular details

Note: Most histology is done with the 10x and 40x lenses.

7. Eyepiece - forms an image that can be visualized by the eye or a camera

a. ocular lens - magnifies (typically 10x) and rotates the primary image produced by the objective lens

b. eyepiece tube

i. holds the ocular.

ii. in a binocular microscope, the distance between the two tubes can be adjusted to fit the distance between the observers eyes.

8. Focusing controls - used to raise and lower the specimen stage to focus the image of the specimen

a. coarse focus - used to focus the specimen at 4x and 10x

b. fine focus - used to focus the specimen at 40x and 100x, but only after initially focusing at lower magnification

c. focus stop

i. present on some microscopes to set the highest point to which the stage can be raised

ii. prevents the slide from being pressed against the front of the objective lens

d. tension adjustment of coarse focus - present on some microscopes to adjust the tightness of the coarse focusing knob

9. Specimen stage - holds the microscope slide

a. slide holder - spring-loaded device to hold the microscope slide in place on the stage

b. slide holder travel controls - allow the slide to be moved along two axes: longitudinal and lateral

c. stage verniers - present on some stages to measure the position of the center of the slide


| Cartoons by: Coral McCallister | Copyright by: Paul B. Bell, Jr. & Barbara Safiejko-Mroczka |

The University of Oklahoma

Version: 010507