Several Precautions for Proper Use of Optical Microscopes
1、 Correct installation issues
Before using a microscope, first install the eyepiece and objective of the microscope. The installation of the eyepiece is extremely simple, and the main problem lies in the installation of the objective lens. Due to the high value of the objective lens, if the thread is not properly closed during installation, it is easy for students to fall to the ground and cause lens damage. Therefore, for safety reasons, it is emphasized that students use their left index finger and middle finger to hold the objective lens when installing it, and then use their right hand to install it, so that even if it is not properly installed, it will not fall to the ground.
2、 Correct alignment of light issues
Focusing on light is an important step when using a microscope. Some students casually turn an objective lens towards the aperture when focusing on light, rather than using a low-power lens as required. When rotating the reflector, I like to use one hand and often pull it off. So when guiding students, teachers must emphasize using low-power mirrors to aim at 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 reflector. Use both hands to rotate until you see a uniformly bright circular field of view. After aligning the light, do not move the microscope casually to prevent light from accurately entering the aperture through the reflector.
3、 The problem of correctly using the quasi focal screw
Using a quasi focal screw to adjust the focal length and find the object image can be said to be the most important step in the use of a microscope, and it is also the most difficult step for students. Students are prone to the following errors during operation: firstly, directly focusing under a high-power mirror;
The second is that regardless of whether the lens barrel rises or falls, the eye always sees the field of view in the eyepiece; The third reason is that the critical value of the object distance is not understood. When the object distance is adjusted to 2-3 centimeters, it is still upward, and the speed of rotating the quasi focal screw is very fast. The first two types of errors often result in the objective lens colliding with the mount, damaging the mount or lens, while the third type of error is a common phenomenon among students when using a microscope. In response to the above errors, the teacher must emphasize to the students that adjusting the focal length must be lowered at a low magnification. First, rotate the coarse focusing screw to slowly lower the lens barrel, and the objective lens should be close to the glass slide. However, be careful not to let the objective lens touch the glass slide. During this process, the eye should look at the object lens from the side, then use the left eye to gaze into the eyepiece, and slowly reverse adjust the coarse focusing screw to slowly raise the lens barrel until the object image is visible, At the same time, explain to the students that the object distance of a general microscope is about 1 centimeter. Therefore, if the object distance has far exceeded 1 centimeter, but the object image is still not visible, it may be that the specimen is not in the field of view or the coarse focus spiral rotates too fast. At this point, the loading position should be adjusted, and then the above steps should be repeated. When a blurred object appears in the field of view, a fine focus spiral adjustment should be used to narrow the search range, Increase the speed of finding objects.
、 The problem of objective lens conversion
After using a low-power lens and switching to a high-power lens, students often prefer to use their fingers to directly rotate the objective lens, thinking it is more labor-saving. However, this can easily cause the optical axis of the objective lens to deviate, because the material of the converter is soft and has high accuracy, and the thread is easily loosened due to uneven force. Once the thread is damaged, the entire converter will be scrapped. Teachers should guide students to hold the lower rotating lever of the converter to convert the objective lens.
5、 The problem of cleaning optical glass
Optical glass is used for lenses, prisms, lenses, etc. of instruments. During manufacturing and use, it is easy to get contaminated with oil, water-based dirt, fingerprints, etc., which affects imaging and transmittance. To clean optical glass, different cleaning agents, tools, and methods should be selected based on the characteristics and structures of the dirt. Clean lenses coated with antireflective film, such as those of cameras, slide projectors, and microscopes, using a cleaning agent of about 20% alcohol and about 80% ether. When cleaning, use a soft bristle brush or cotton ball with a small amount of cleaning agent, and make a circular motion outward from the center of the lens. Do not immerse such lenses in cleaning agents for cleaning. Do not use force to wipe the lens when cleaning, otherwise it may damage the anti reflective film and damage the lens.
The method of cleaning prisms and flat mirrors can be carried out according to the method of cleaning lenses.
The above cleaning agent can also be used to clean greasy mist, water wet mist, and oil-water mixed mist on optical glass, and the cleaning method is similar to that of cleaning lenses.
Mold on the surface of optical glass is a common phenomenon. When optical glass becomes moldy, light scatters on its surface, blurring the image, and in severe cases, the instrument will be scrapped. The reason for mold formation in optical glass is often due to the presence of microbial spores on its surface. When the temperature and humidity are suitable and there is a need for "nutrients", it will quickly grow and form mold spots. It is particularly important to prevent mold and dirt on optical glass, and once mold spots occur, they should be cleaned immediately.
