Use and Maintenance of Biological Microscope Correct Focusing of Objective Lens
After the light is completed or the appropriate light is adjusted, raise the lens barrel or lower the stage, clamp the specimen slide on the mover, that is, the specimen holder, and move the part to be inspected to the center of the light hole of the stage. Then start focusing.
No matter what kind of inspection is done, it should start with a low power lens. When focusing, use the coarse handwheel to lower the lens barrel so that the distance between the front lens of the low-magnification mirror and the cover glass is slightly smaller than the working distance of the objective lens (below 5mm). In order to avoid the objective lens pressing on the specimen slide, peep from the side. Then, while observing the field of view from the eyepiece, use the coarse handwheel to slowly raise the lens barrel. After seeing the object image for the first time, use the fine handwheel to fine-tune the focus until the object image is the clearest. The field of view of the low magnification objective lens is large, which is conducive to observing the whole picture of the specimen. You can also use the mover or adjust the handwheel vertically and horizontally to find the observed target. If necessary, the found target can be moved to the center of the field of view, ready for high-power lens observation.
When converting from a low-magnification objective lens to a high-magnification objective lens, if the objective lens is the original equipment of the microscope, and the slide glass and cover glass used meet the standards, "equal-height conversion" can generally be performed. That is, after the conversion, you can see a clear image as long as you slightly adjust the fine-tuning knob. But the oil lens does not insist on parfocality. It is best to raise the lens barrel before switching, and finally refocus according to the focusing method of the low-power lens.
The method of using the oil lens is as follows: first raise the lens barrel, remove the specimen slide, lower the condenser slightly, and drop two drops of cedar oil on the lens of the condenser (there should be no air bubbles in the oil. If any, It can be removed with a small wooden stick), then put the specimen slide back to its original position, and raise the condenser so that the bottom surface of the slide is in contact with cedar oil. In this way, the oil immersion of the condenser is completed. Next, drop 1 drop of cedar oil on the cover slip. Then peep from the side, use coarse adjustment to lower the lens barrel as far as possible, until the front lens of the oil lens is immersed in the cedar oil (but not yet in contact with the glass slide), thus completing the oil immersion of the objective lens. Then, while observing from the eyepiece, use the micro handwheel to slowly raise the lens barrel (be careful not to twist the wrong direction and crush the cover glass) until the clearest object image appears in the field of view.
The oil immersion of the condenser can also adopt another method of dripping oil: that is, instead of directly dripping the oil on the lens of the condenser, turn the slide over and drop the oil on the bottom surface of the slide, and then Turn it over again, align and place it on the concentrator, and then raise the concentrator to complete the oil immersion of the concentrator. Although this method is not so smooth, it is more applicable. Some people use a glass rod to directly contact the condenser to apply cedar oil. This method is easy to scratch the lens and should not be used.
When using an oil lens, it is allowed not to add cedar oil between the condenser lens and the specimen, that is, air is still used as the medium on the condenser lens, but this will sacrifice the resolution of the objective lens.
If you need to switch back to the high-magnification objective lens for observation after using the oil lens, wipe off the oil on the cover glass to avoid contamination of the high-power objective lens. However, the oil on the concentrator does not need to be wiped, as long as the aperture is properly reduced a little.
After the oil lens is used, the cedar oil should be wiped clean in time. The lens can be wiped with a clean lens tissue for 1 or 2 times to wipe off most of the oil. Then wipe it twice with a lens tissue wetted with xylene, and finally wipe it clean with a lens tissue. The cleaning method of the condenser is the same. If the specimen needs to be preserved, the cedar oil on the glass slide can be wiped clean by "pulling paper". Cover the glass slide with lens cleaning paper, drop a drop of xylene on the paper, drag the paper strip while it is wet, and wipe it clean several times in a row.
Finally, it is pointed out that during the entire focusing process (especially the focusing of high-magnification objective lenses and oil lenses), every movement must be performed slowly. Otherwise, the object image will flash by and the target of observation cannot be found.
