Operation of the Oil Immersion Objective Lens of an Optical Microscope
(1) Identification of oil lenses:
The magnification of each objective lens can be identified by its shape. The longer the lens length, the smaller the lens diameter, and the higher the magnification factor; On the contrary, the magnification factor is small. The length of an oil lens is greater than that of a low or high magnification lens, and the lower edge of the lens is generally engraved with a circle of black or white lines, as well as words such as 100 x, 1.25 or oil.
(2) Usage of oil mirror:
1. When using a microscope oil mirror, the microscope must be upright on the table, and the mirror arm must not be bent, causing the stage to tilt, in order to avoid the overflow of asphalt, affecting observation, and contaminating the table.
2. Regarding light:
When using natural light as the light source, it is advisable to use a flat reflector; If artificial lighting is used, use a concave mirror. Firstly, open the aperture and rotate the reflector to concentrate the light on the collector. You can move the collector up and down and zoom the aperture as needed to achieve the best brightness.
When observing objects with low or high magnification mirrors or examining unstained specimens with oil microscopes, it is necessary to lower the collector and appropriately reduce the aperture to weaken the brightness; When examining stained specimens with an oil microscope, the brightness should be strong. The brightness switch of the microscope should be set to * bright, the aperture should be fully opened, and the collector should be raised to be level with the stage.
3. Focus adjustment:
A, Place the specimen on the stage, fix it with a specimen pusher, and move the part to be examined under the objective lens. First, use a low-power microscope to locate the position of the specimen, then raise the lens barrel and apply a drop of mirror oil to the specimen to be examined, and then change the oil microscope for observation.
B, Rotate the coarse adjuster to slowly raise the stage (or gradually lower the lens barrel) until the oil lens is submerged in oil. At this point, the eyes should be observed from the side to avoid crushing the specimen and damaging the lens.
C, Then move both eyes to the eyepiece, observe from the eyepiece while slowly rotating the coarse adjuster (descending stage, or ascending tube) in the opposite direction. When a blurry object image appears, switch to the fine adjuster and rotate until the object image is clear
D, After observation, the lens barrel should be raised and the oil lens twisted to one side before removing the specimen. After using the oil lens, immediately wipe off the oil on the lens with lens cleaning paper. If the lens oil is viscous and dry on the lens, you can use lens wiping paper dipped in a little xylene to wipe the lens, and then use dry lens paper to wipe off the remaining xylene to prevent xylene from penetrating and dissolving the gum used to fix the lens, causing the lens to shift or fall off.
(3) The principle of using oil mirrors:
The lens of the oil lens is very small. When light passes through the air between the glass slide and the oil lens, it undergoes refraction or total reflection due to different medium densities, reducing the amount of light entering the lens and making the object image unclear. If cedarwood oil (n=1.515) with a refractive index similar to that of glass (n=1.52) is added between the oil mirror and the glass slide, it will increase the amount of light entering the lens, enhance the brightness of the field of view, and make the object image bright and clear.
