Analysis on how to use the objective lens and focusing of microscope well
When use a microscope, that principle of focusing at low pow first and then at high power is adopted. Focusing at low pow objective is equivalent to primarily focusing at high power objective. When turning at high power objective, just turn the lens around directly (i. e. without changing the focal length preliminarily adjusted through the operation of low power lens), and under high power lens, the tissue can be observed with slight adjustment or even without adjustment. However, many operating instructions avoid the specific reference of "low power objective".
In the use of microscope, the 10-fold objective lens is the standard common objective lens in focusing work. The reason is that there will be no sharp change from the 10-fold objective lens to the lower-fold objective lens, or from the 10-fold objective lens to the higher-fold objective lens. Another reason is that the focal depth of the lower power objective lens is long, so it is not easy for the observer's naked eye to focus well, and it is easy for the sample to touch the lens when it is directly converted to the higher power objective lens.
At the same time, the 10-fold objective lens is not only a standard common objective lens in focusing work, but also involves a lot in practical work. For example, in many relevant national standards for metallographic examination, it is the most common to compare the reference standard chart under the condition of 100 times observation, and 100 times is obtained by matching 10 times objective lens with 10 times eyepiece. From the practical point of view, as long as it is not random or malicious, the previous operation behavior should be to make the objective lens near the focal plane. Under the condition of 10 times the objective lens, after the sample is placed correctly, a blurred image should appear, even if it is clear, and a slight adjustment can be made.
(2) Relevant discrepancy
Our experience is quite different from the introduction in other documents on the focusing problem after the conversion from low-power objective to high-power objective. Due to the improvement of microscope manufacturing technology, the focus of different objective lenses of microscope is better, especially for foreign products. In this way, after focusing clearly at low magnification, it is sometimes unnecessary to focus the image again when observing at high magnification. Or, slightly increase the object distance, the degree of adjustment is by no means the concept of 1 ~ 3 turns, that is, the concept of 1 ~ 3 degrees (angle), which is extremely small adjustment.
(3) About objective lens converter
When changing the objective lens, you can't push it directly by hand, otherwise it will easily cause the thread of the fixed objective lens to be loose and the optical axis to be skewed. The objective lens of the microscope and the microscopic digital camera system are screwed on the objective lens converter. When changing different objective lenses, rotate the objective lens converter until the ear hears a slight "click" sound and the hand resistance increases sharply. At this time, the objective lens is in a normal working position: perpendicular to the plane of the stage.
(4) the relationship between "forward and backward" and "object distance"
The coarse adjustment and fine adjustment of the rotating direction of the knob of the microscope are closely related to the increase and decrease of the object distance. The so-called clockwise and counterclockwise are also relative, generally the effect of looking at the past from the right side of the microscope; Different types of microscopes need to rotate the focusing knob in different directions when the object distance is reduced or increased, which needs to be clearly explained in the process of teacher's guidance. In the case of ambiguity, the relationship between the focusing knob and the object distance must be clearly understood in advance when operating the microscope formally; Never blindly follow some instructions for clockwise and counterclockwise special occasions.
