How to Use the Objective and Focusing of a Microscope Well
When using a microscope, the focusing principle of first low magnification and then high magnification is adopted. Focusing under a low magnification objective is equivalent to preliminary focusing on a high magnification objective. When turning a high magnification objective, the lens only needs to be turned directly (i.e., the initial focal length adjusted through low magnification operation is not changed). Under a high magnification objective, tissue can be observed with minimal or no adjustment. However, many operating instructions avoid the specific reference to "low magnification objective".
During the use of a microscope, a 10x objective is the standard and commonly used objective in focusing work. The reason is that there will be no sharp changes in the replacement of lenses from 10x to lower magnification, or from 10x to higher magnification. Another reason is that the focal length of the lower magnification objective lens makes it difficult for the observer's naked eye vision to align well with the focal point, resulting in contact between the sample and the lens when directly transitioning to the higher magnification objective lens.
At the same time, a 10x objective is not only a standard and commonly used objective in focusing work, but also involves a lot in practical work. For example, in many national standards related to metallographic examination, it is common to refer to standard spectra under 100x observation conditions, while obtaining 100x is achieved by combining a 10x objective lens with a 10x eyepiece. Starting from actual operation, as long as it is not arbitrary or malicious, the previous operation behavior should be to keep the objective lens near the focal plane. Under 10 times the objective lens condition, when the sample is placed correctly, there should be blurry images, even relatively clear ones, and slight adjustments can be made.
⑵ Regarding entry and exit
Our experience differs significantly from the introduction in other literature regarding the focusing issue after the conversion from a low-power objective to a high-power objective. Due to the improvement of microscope manufacturing technology, the confocal performance of different lenses in microscopes is relatively good, especially in foreign products. This way, when switching to high magnification observation after clear low magnification, sometimes there is no need to refocus the image to make it clear; Alternatively, by slightly increasing the object distance, the degree of adjustment is not a concept of 1-3 turns, that is, 1-3 degrees (angle), but an extremely small amount of adjustment.
⑶ Regarding the objective lens converter
When converting the objective lens, it is not allowed to directly push the objective lens by hand, otherwise it may cause the screw thread of the fixed objective lens to be loose and cause the optical axis to tilt. The objective lens and microscopic digital camera system of the microscope are tightened onto the objective lens converter. When changing different objective lenses, rotate the objective lens converter to hear a slight "click" sound and a sharp increase in hand resistance as the endpoint. At this point, the objective lens is in its normal working position: perpendicular to the plane of the stage.
The relationship between "forward, backward" and "object distance"
The coarse adjustment and fine adjustment of the rotation direction of the microscope knob are closely related to the increase and decrease of the object distance. The so-called clockwise and counterclockwise are also relative, usually the effect seen from the right side of the microscope; Different models of microscopes require different directions of rotation of the focusing knob when reducing or increasing the object distance, which should be clearly explained in the process of teacher guidance. In ambiguous situations, the relationship between the focusing knob and the object distance must be clearly understood in advance when operating the microscope formally; Never blindly follow the clockwise and counterclockwise characteristics of certain guidance instructions
