Some Considerations for Proper Use of an Optical Microscope
1. The problem of correct installation
Before using the microscope, first install the eyepiece and objective lens of the microscope. The installation of the eyepiece is very simple. The main problem lies in the installation of the objective lens. Since the objective lens is expensive, if the screw is not closed properly when the student installs it, it is easy to fall to the ground and cause damage to the lens. Therefore, for the sake of safety, it is emphasized that students use Hold the objective lens with the index finger of the left hand and the middle finger, and then install the objective lens with the right hand, so that even if it is not installed, it will not fall to the ground.
Second, the problem of correct light
Aiming at the light is a very important step when using a microscope. Some students just turn an objective lens to face the light hole when they are at the light, instead of using a low-power lens to align with the light as required. I like to use one hand when turning the mirror, and it often turns the mirror down. Therefore, when teachers instruct students, they must emphasize the use of low power mirrors to face the light. When the light is strong, use a small aperture, flat mirror, and when the light is weak, use a large aperture, concave mirror, and the reflector should be turned with both hands. Until a uniformly bright circular field of view. Do not move the microscope casually after the light is aligned, so as to prevent the light from entering the light hole accurately through the mirror.
3. The problem of using the quasi-focus helix correctly
Using the quasi-focus screw to adjust the focal length and find the object can be said to be the most important step in the use of the microscope, and it is also the most difficult step for students. Students are prone to the following mistakes in operation: one is to directly adjust the focus under a high-power lens;
The second is that regardless of the rise or fall of the lens barrel, the eyes always look at the field of view in the eyepiece; the third is that the critical value of the object distance is not understood, and the object distance is adjusted to 2 ~
At 3 cm, it is still adjusted upwards, and the speed of turning the focus screw is very fast. The first two kinds of error results often cause the objective lens to interfere with the mounting film and damage the mounting film or lens, while the third error is the most common phenomenon when students use the microscope. In response to the above mistakes, the teacher must emphasize to the students that the adjustment of the focal length must be done at a lower magnification, first turn the coarse and accurate focus screw, so that the lens barrel slowly descends, and the objective lens is close to the glass slide, but be careful not to let the objective lens touch the slide glass In this process, the eyes should look at the objective lens from the side, and then stare into the eyepiece with the left eye, and slowly adjust the coarse quasi-focus screw in reverse, so that the lens barrel slowly rises until the object image is seen, and at the same time point to the students Note that the object distance of a general microscope is about 1 cm, so if the object distance is far more than 1 cm, but the object image is still not seen, it may be that the specimen is not in the field of view or the coarse and accurate focus helix is turned too fast. At this time, it should be adjusted Install the film position, and then repeat the above steps. When blurred objects appear in the field of vision, it is necessary to switch to the fine-focus screw adjustment. Only in this way can the search range be narrowed and the speed of finding objects can be increased.
4. The problem of objective lens conversion
After using a low magnification lens and switching to a high magnification lens, students often prefer to push and turn the objective lens directly with their fingers, thinking that this is more labor-saving, but it is easy to deflect the optical axis of the objective lens because the material of the converter is softer and the precision is higher. , the thread is uneven and easy to loosen. Once the threads are broken, the entire converter is scrapped. The teacher should instruct the students to hold the lower layer of the converter and turn the switch to convert the objective lens.
Five, the problem of optical glass cleaning
Optical glass is used for lenses, prisms, lenses, etc. of instruments. During manufacturing and use, it is easy to be stained with oil, water-wet dirt, fingerprints, etc., which will affect imaging and light transmittance. To clean optical glass, you should choose different cleaning agents, use different cleaning tools, and choose different cleaning methods according to the characteristics and structure of the dirt. To clean lenses coated with anti-reflection coatings, such as cameras, slide projectors, and microscope lenses, use about 20% alcohol and about 80% ether to prepare cleaning agents for cleaning. When cleaning, apply a soft brush or cotton ball with a small amount of cleaning agent, and make a circular motion from the center of the lens outward. Do not soak this type of lens in cleaning agent, and do not wipe it hard when cleaning the lens, otherwise it will damage the anti-reflection coating and damage the lens.
The method of cleaning prisms and plane mirrors can be carried out according to the method of cleaning lenses.
The above cleaning agent can also be used to clean the greasy mist, water wet mist and oil-water mist on the optical glass. The cleaning method is similar to that of cleaning the lens.
Mold on the surface of optical glass is a common phenomenon. When the optical glass is moldy, the light will scatter on its surface, making the image blurred, and in severe cases, the instrument will be scrapped. The reason for mold on optical glass is mostly because of the microbial spores attached to the surface. When the temperature and humidity are suitable and the required "nutrients" are available, they will grow rapidly and form mold spots. It is especially important to prevent mildew and pollution on optical glass. Once mildew occurs, it should be cleaned immediately.
