Before the assembly of the objective lens of metallographic microscope, all the optical parts and metal parts are strictly cleaned. During the assembly, the position of each lens group is well fixed, and it is not easy to loose. If it can be used properly and kept properly, it is not easy to cause failure. In improper use or storage, it will cause mildew, fog, oil (or water) in the optical parts of the objective lens, the front lens falling off, or even the lens breaking and other phenomena, so that the image quality significantly deteriorated, the objective lens needs to be removed and repaired.

When disassembling the objective lens of the metallographic microscope, attention should be paid to the placing order and direction of each lens group in the lens simple. When disassembling the lens group, mark it on the lens base with a pencil to avoid confusing the sequence of the lens group. When the lens group fixed by the wrapping method is found to have each point or fog point, the lens and lens holder can be carefully and gradually wiped by picking up the absorbent cotton core with the most mixed solvent with the cotton swab. But the front lens should be cleaned by toluene instead of alcohol diethyl ether mixture, so as not to dissolve the dry solid glue and fall off the lens.

The reasons for oil infiltration inside the objective lens are as follows: the glue layer between the front lens and the metal base is not adhered firmly, or the glue layer is dissolved by misuse of sprinkling essence to wipe the front lens, and the oil seeps into the lens through the empty space, or too much oil drips into the inside from the edge of the front lens base when using the oil lens.

If the oil in the objective lens, the front lens falls off and the lens breaks and so on cannot be repaired, it can be sent back to the manufacturer for repair.