Optical microscope mainly consists of objective lens group and eyepiece, which are usually equipped with lens groups with different magnification. Through combination, a very large-span magnification range can be formed. This configuration is because although the details of the high-power lens group are clearly displayed, the field of view and depth of field are narrow and it is not convenient to move in different target areas. Although the magnification of the low-power lens group is small, the field of view and depth of field are large, which is convenient for searching for targets in a wide range. Besides, some specific samples do not need large magnification, but all the targets in the field of vision are required to be as clear as possible, so the low-power lens group is also useful. The combination of the two can obtain perfect and clear imaging.

Objective lens group: such as 100x, 200x, 300x, 600x, etc.

Eyepiece group: such as 5x, 10x, 15x, 20x, etc.

According to experience, change into low-power objective lens group and appropriate eyepiece lens group.

Replace the appropriate high-power objective lens and eyepiece, and focus carefully by fine adjusting the handwheel.

Skills of focusing: When fine-tuning focusing, there must be a process of blurring-clearing-re-blurring, in order to confirm the most accurate focus, so it is necessary to overdo it a little and then turn back to the clear focus position.