How to change a microscope's low-magnification lens for a high-power lens
As we all know, in the process of using a microscope, it is generally observed clearly with a low magnification lens, then the sample to be magnified and observed is moved to the center of the field of view, and finally the high magnification lens is replaced for observation, so there is a conversion between low magnification and high magnification during use. , which is what we often say to find the field of view with a low magnification lens, and observe the sample with a high magnification lens. This is also the most basic common sense for microscopes, but the methods used are different. How to use between mirrors.
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. When it is not in use, it is usually packed and placed in a box. When it is used, it is taken out and opened. Keep it 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. Slowly during the rotation, when you hear the click button, open the aperture, raise the collector, and turn the reflector to the light source, observe on the eyepiece with the left eye (do not close the right eye), and adjust the reflector at the same time direction 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 the point where the objective lens is about 5 mm away from 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 and lowering the position of the light collector or opening and closing the size of 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 If the operation fails this time, it should be operated again, and the stage must not be raised impatiently and blindly.
2. How to use the high power lens
When the object needs to be further magnified for observation, it can be observed with a high-magnification lens.
(1) High magnification lens focusing
When the low magnification lens is adjusted, the high magnification objective lens can be replaced at this time 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 slide), such as the high magnification lens If it touches the glass slide, it means that the focal length of the low-magnification mirror has not been adjusted properly, and the operation should be repeated.
(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 generally see a not very clear object image. You can move the screw of the fine adjuster counterclockwise for about 0.5-1 circle to obtain a clear object. For example, if the brightness of the field of view is not suitable, adjust it with the light collector and aperture. 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 types of objective lens multiples, but when the objective lens reaches 100, cedar oil or fir oil is needed as the objective lens, so the objective lens with a factor of 100 or more is an oily objective lens, which is generally marked with "oil". The medium used is not air but cedar oil or fir oil, because the refractive index of oil is higher than that of air, which improves the resolution of the lens, but we should pay attention to the method when using oil lenses, otherwise the effect will be counterproductive.
(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, then adjust the thick and thin focus screw, and move the objective lens down slowly until it touches the cedar oil on the cover glass. Be careful during this process, 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 dry lens cleaning paper to absorb the oil on the lens, and then use the lens cleaning paper soaked in xylene Wipe it clean, and finally wipe it with a dry lens tissue.
