The objective lens is the key component of the optical system. Its performance has a decisive influence on the performance of the metallographic microscope. When the system is determined, the correct operation of the objective lens is an important measure to improve the quality of the instrument, protect the performance of the instrument, improve the working efficiency and prolong the service life.

The focus of the objective lens is performed after the position of the illumination source has been adjusted. When focusing, the operator should be familiar with the working distance of the objective lens and operate according to the working distance of the objective lens. Since the working distance of the low power objective lens is longer, it is better to use the low power objective lens first when focusing.

The steps of focusing are: first, rotate the upper low-power objective lens of the converter to the working position, put the metallographic sample on the loading table, and cover about 1/3 of the light through hole. Then, the distance between the objective lens and the sample is observed through the light hole of the uncovered part of the object platform. At the same time, the coarse-motion focusing handwheel is rotated to make the object platform slowly decrease in level until the distance between the objective lens and the sample is slightly shorter than the working distance of the objective lens. Then move the sample to completely cover the stage through the light hole, observe the field of view of the eyepiece with your eyes, and slowly rotate the coarse focusing hand wheel, so that the stage back up. When the outline of the object appears in the eyepiece field of view, the coarse-motion focusing is stopped, and the operation is carried out by the micro manual wheel until the clear image is seen in the eyepiece field of view of the metallographic microscope.