Important Precautions for Microscope Operation
The objective lenses mainly include 4×, 10×, 40× and 100× oil immersion objectives. The operating rule is to observe from low magnification to high magnification. When examining tissue sections, start with the 4× objective (yielding a total magnification of 40× when paired with a 10× eyepiece). Turn the coarse focusing knob until the image of the section appears. The light source intensity may be adjusted at this stage. Then switch to the 10× objective (100× total magnification), and turn the fine focusing knob until the image becomes sharp.
Beneath the circular opening of the stage is a condenser for gathering and regulating light. Below the condenser is an iris diaphragm. Its control lever adjusts the aperture size. Together with the light source, it controls the intensity of light passing through the condenser onto the underside of the slide. Excessively bright light reduces contrast and blurs the specimen. In this case, narrow the iris diaphragm for better observation.
To use the 100× objective (1000× total magnification), first rotate away the current objective. Place a small drop of immersion oil on the coverslip. The immersion oil has a refractive index close to glass to prevent light scattering and deliver clearer images. Gently rotate the objective until it nearly touches the coverslip. The lens sits very close to the coverslip. Take extreme care during focusing to avoid contact between the lens and coverslip, which may break the slide.
When working with the oil immersion objective (1000×), use the fine focusing knob to raise the stage until the coverslip lightly touches the objective lens. Then slowly lower the stage with the fine focusing knob to search for focus. If the objective separates from the oil and coverslip, repeat this step.
After finishing work with the oil immersion lens, wipe it repeatedly with lens tissue moistened with 95% or 99.5% alcohol, then polish thoroughly with clean dry lens tissue.
After use, lower the stage to the minimum position, turn off the light source, and fit the dust cover.
