The microscope is a fundamental instrument in clinical laboratories, essential for examining fecal, urine, blood, and cytology samples daily. A thorough understanding of the microscope’s mechanics, operation, and maintenance is crucial for ensuring reliable results and extending the lifespan of this valuable tool.
Parts and Functions of a Compound Microscope
(A) Arm
The arm is designed for carrying the microscope.
(B) Base
The base supports the microscope and houses the light source.
(C) Oculars (Eyepieces)
Oculars, or eyepieces, are the lenses through which the user views the sample. They magnify the image, with common magnifications being 10×. Total magnification is calculated by multiplying the power of the oculars by that of the objective lens.
(D) Diopter Adjustment
The diopter adjustment compensates for differences in vision between the user’s eyes.
(E) Interpupillary Adjustment
This adjustment allows the oculars to be moved closer together or farther apart to match the user’s eye width, ensuring a single, unified field of view and reducing eye strain.
(F) Nosepiece
The nosepiece holds the objective lenses, which are mounted on a rotating turret, allowing for easy switching between objectives. Most nosepieces can accommodate up to five objectives.
(G) Objective Lenses
Objective lenses are positioned closest to the sample and provide varying levels of magnification, such as 4× (scanning), 10× (low power), 40× (high power), and 100× (oil immersion). The total magnification is the product of the ocular and objective lens powers. For instance, a 100× objective lens used with 10× oculars yields a total magnification of 1000×.
(H) Stage
The stage is the platform where the slide or specimen is placed for examination.
(I) Stage Brackets
Spring-loaded brackets, or clips, secure the slide or specimen on the stage.
(J) Stage Control Knobs
Located below the stage, these knobs move the slide horizontally (x-axis) or vertically (y-axis) for precise viewing.
(K) Condenser
Situated under the stage, the condenser focuses and directs light from the illuminator onto the specimen.
(L) Condenser Control Knob
This knob allows for the adjustment of the condenser’s height.
(M) Condenser Centering Screws
These screws center the condenser and the beam of light. Adjustments are typically minimal unless the microscope has been moved.
(N) Iris Diaphragm
The iris diaphragm regulates the amount of light reaching the specimen by adjusting the diameter of the light beam.
(O) Coarse and Fine Focus Adjustment Knobs
These knobs raise and lower the stage to bring the object into focus. The coarse adjustment is used for general focusing under low power, while the fine adjustment is for high-power, precise focusing. Care must be taken to avoid contact between the slide and high-power objectives, which can damage both the slide and the lens.
(P) Illuminator
The illuminator, typically located in the base, is the light source for the microscope. Its brightness can be adjusted according to the viewing requirements.