How to change a microscope's low-magnification lens for a high-power lens
As we all know, the microscope is generally observed clearly with a low magnification lens, and then the sample to be magnified and observed is moved to the center of the field of view, and finally replaced with a high magnification lens for observation, so there is a conversion between low magnification and high magnification during use, which is what we often say.
1. How to use the low magnification lens
When observing any specimen, you must use a low-power lens first, because its field of view is large, and it is easy to find the target and determine the part to be observed.
(1) Mirror taking and placement
The microscope is a high-precision optical experimental instrument. It is usually packaged and placed in a box when it is not in use. When it is used, it is taken out and opened. When taking out the mirror, hold the mirror arm tightly with your right hand and hold the mirror base with your left hand to keep the mirror body upright to prevent the mirror and eyepiece from slipping out. Gently place the microscope on the laboratory table, usually on the left side, 3 to 4 cm away from the edge of the table, with the mirror arm facing your chest for easy observation.
(2) cleaning
Check whether the microscope is faulty and clean. If there is dust on the metal part, wipe it with a clean soft cloth. If the lens is dirty, wipe it with lens cleaning paper, never with a handkerchief, if there is glue or dirt, clean it with a small amount of xylene.
(3) Lighting steps
Raise the lens barrel to a distance of 1-2 cm from the stage, and rotate the objective lens converter to turn the low-power mirror to the stage and align it with the central light hole. Turn slowly, and when you hear the click sound, open the aperture, raise the light collector, and turn the reflector to the light source, observe with the left eye on the eyepiece (don’t close the right eye), and adjust the direction of the reflector at the same time until the light in the field of view is uniform and bright.
(4) Place slide specimens
Take a slide specimen and place it on the stage. Note that the side with the cover glass must face up, otherwise the focus cannot be adjusted when observing with a high-power lens, and the slide specimen is easily damaged. Then clamp the glass slide with a slice clamp, turn the helix of the platform mover, and align the part to be observed with the center of the light hole.
(5) Adjust the focal length
Turn the coarse adjuster counterclockwise with your left hand to slowly raise the stage to a distance of about 5 mm from the objective lens to the specimen. Be careful not to observe on the eyepiece when raising the stage. Be sure to watch the stage rise from the right side, so as not to rise too much and cause damage to the lens or specimen slides. Then, open both eyes at the same time, observe on the eyepiece with the left eye, and slowly turn the coarse adjuster clockwise with the left hand to lower the mirror stage slowly until a clear object image appears in the field of vision.
Note: If the object image is not in the center of the field of view, you can adjust the pusher to adjust it to the center (note that the direction of moving the slide is opposite to that of the object image in the field of view). If the brightness in the field of view is not suitable, it can be adjusted by raising or lowering the position of the light collector or opening and closing the aperture. If when adjusting the focal length, the mirror stage has descended beyond the working distance (>5.40mm) and no object image is seen, it means that the operation failed, and the operation should be repeated. Do not raise the mirror stage blindly.
2. How to use the high power lens
When the object needs to be further magnified for observation, high-power lens observation can be carried out.
(1) High magnification lens focusing
When the low magnification lens is adjusted, the high magnification objective lens can be replaced for observation. First, turn the converter. When switching to the high magnification lens, the rotation speed should be slow, and observe from the side (to prevent the high magnification lens from colliding with the glass slide).
(2) Adjust the focal length
After switching to the high-magnification lens, use the left eye to observe on the eyepiece. At this time, you can usually see a not-so-clear object image. You can move the screw of the fine adjuster counterclockwise for about 0.5-1 turn to obtain a clear object image. If the brightness of the field of view is not suitable, use the light collector and aperture to adjust it. If you need to replace the slide specimen, you must turn the coarse adjuster clockwise (do not turn in the wrong direction) to lower the mirror stage before removing the slide specimen.
3. How to use the oil lens
There are many multiples of the objective lens, but when the objective lens reaches 100, it needs cedar oil or fir oil. Therefore, the objective lens with more than 100 times is oily objective lens, which is generally marked with "oil".
(1) Before using the oil lens, you must first find the object under inspection through a low-power lens, and then use a high-power lens to adjust the focus. After the object under inspection is adjusted to the center of the field of view, change the oil lens for observation.
(2) When using an oil lens, be sure to add a drop of cedar oil (lens oil) on the cover glass before using it. Turn the objective lens so that the oil lens turns to the optical axis, and then adjust the thick and fine focus screw, so that the objective lens moves down slowly until it touches the cedar oil on the cover glass. Be careful during this process, and try to avoid the lens from crushing the cover glass or specimen. At this time, observe the eyepiece, rotate the fine-focus screw until a clear specimen image can be seen in the field of view, and adjust the condenser to change the intensity of the light. When observing specimens with an oil immersion lens, the coarse adjustment wheel is not allowed, and only the fine adjustment wheel can be used to adjust the focus. If the cover glass is too thick, it cannot focus and needs to be replaced, otherwise it will crush the glass or damage the lens.
(3) After the observation, the oil on the lens should be wiped off in time. The method is to lower the objective stage to separate the specimen from the objective lens. First, use a dry lens tissue to absorb the oil on the lens, then wipe it with a lens tissue soaked in xylene, and finally wipe it with a dry lens tissue.
