How to use the quasi-focus screw in the tool microscope
It is an important step in the use of tool microscope to adjust the focal length and find the object image by using quasi-focal screw. Never make the following mistakes in operation: First, focus directly under a high-power mirror; Second, no matter whether the lens barrel rises or falls, the eyes always see the field of vision in the eyepiece; Third, I don't know the critical value of the object distance. When the object distance is adjusted to 2~3 cm, it is still upward, and the speed of rotating the quasi-focus screw is very fast. The first two kinds of errors often cause the objective lens to collide with the mounting and damage the mounting or lens, while the third kind of error is the most common phenomenon when using a microscope.
When adjusting the focal length, you must lower it in the low-power lens. First, turn the coarse quasi-focus screw to make the lens barrel slowly descend, and the objective lens is close to the glass slide, but don't let it touch the glass slide. During this process, your eyes should look at the objective lens from the side, then look into the eyepiece with your left eye, and slowly adjust the coarse quasi-focus screw reversely to make the lens barrel slowly rise until you see the object image. At the same time, the object distance of the general microscope is about 1 cm, so if the object distance is far more than 1 cm, you still can't see the object. It may be that the specimen is not in the field of vision or the coarse quasi-focus screw is rotating too fast. At this time, the loading position should be adjusted, and then the above steps should be repeated. When there is a fuzzy object image in the field of vision, it is necessary to switch to the fine quasi-focus screw adjustment. Only in this way can we narrow the search range and improve the speed of finding the object image.
