A brief analysis of how to use the objective and focus a microscope well
When using a microscope, the principle of focusing first at low magnification and then at high magnification is adopted. Focusing with a low magnification objective lens is equivalent to preliminary focusing of a high magnification objective lens. When switching to a high magnification objective lens, you only need to turn the lens directly over (that is, without changing the focus). The focal length is initially adjusted through low-magnification operation). Under high-magnification, the tissue can be observed with only slight adjustment or even no adjustment. However, many operating instructions avoid the specific meaning of "low magnification objective lens".
In the use of microscopes, the 10x objective lens is the standard commonly used objective lens in focusing work. The reason is that there will be no drastic change when changing from a 10x objective lens to a lower magnification objective lens, or from a 10x objective lens to a higher magnification objective lens. Another reason is that the focal depth of the lower-magnification objective lens is long, and it is difficult for the observer's naked eye vision to focus properly. When subsequently switching directly to the high-magnification objective lens, it is easy for the sample to come into contact with the lens.
At the same time, the 10x objective lens is not only a standard commonly used objective lens in focusing work, but also involves a lot in practical work. For example, in many relevant national standards for metallographic inspection, it is most common to compare the reference standard chart under 100x observation conditions, and 100x is obtained by combining a 10x objective lens with a 10x eyepiece. Starting from the actual operation, as long as it is not random or malicious, the previous operation behavior should be to keep the objective lens near the focal plane. Under the condition of the 10x objective lens, after the sample is placed correctly, a blurred image should appear, or even a relatively clear, slightly blurry image. Just adjust finely.
⑵Related discrepancies
Regarding the focus adjustment issue after converting a low-magnification objective lens to a high-magnification objective lens, our experience is quite different from that introduced in other literature. Due to the improvement of current microscope manufacturing technology, the parfocality of different objective lenses of microscopes is relatively good, especially foreign products. In this way, after focusing clearly at low magnification, when switching to high magnification for observation, sometimes the image is already clear without having to focus again; or, Just slightly increase the object distance. The degree of adjustment is by no means the concept of 1 to 3 turns, that is, the concept of 1 to 3 degrees (angle), which is an extremely small amount of adjustment.
⑶About the objective lens converter
When changing the objective lens, do not push the objective lens directly with your hands, otherwise it will easily cause the thread fastening the objective lens to become loose and cause the optical axis to skew. The objective lens of the microscope and the microscope digital camera system are screwed on the nosepiece. When changing between 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 the normal working position: perpendicular to the plane of the stage.
⑷The relationship between "forward and reverse" and "object distance"
The direction of rotation of the coarse adjustment and fine adjustment knobs of the microscope is closely related to the increase or decrease of the object distance. The so-called clockwise and counterclockwise are also relative, and generally refer to the effect of looking at the past from the right side of the microscope. Different models of microscopes require different directions of rotation of the focusing knob to reduce or increase the object distance. This needs to be determined by the teacher. The guidance process is clearly explained. In the case of ambiguity, the relationship between the focus knob and the object distance must be understood in advance when formally operating the microscope; one must not blindly rely on certain instructions for clockwise or counterclockwise special occasions.
