A brief analysis of how to use the objective lens and focus of a microscope
When using a microscope, the focusing principle of low magnification first and then high magnification is adopted. Focusing under a low magnification objective is equivalent to performing preliminary focusing on a high magnification objective. When turning the high magnification objective, simply rotate the lens directly (without changing the focal length initially adjusted through the low magnification operation). Under the high magnification, tissue can be observed with only slight adjustment or even without adjustment. However, many operating instructions avoid the specific reference to "low magnification objective lens".
During the use of microscopes, a 10x objective lens is a commonly used standard lens for focusing work. The reason is that there will not be a drastic change 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 a lower magnification objective lens is longer, making it difficult for the observer's visual acuity to focus properly. This can lead to contact between the sample and the lens when transitioning directly to a higher magnification objective lens.
At the same time, a 10x objective lens is not only a standard and commonly used objective lens 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 compare the reference standard spectrum under 100x observation conditions, and obtaining 100x is obtained by combining a 10x objective lens with a 10x eyepiece. Starting from practical operation, as long as it is not arbitrary or malicious, the previous operation should be to place the objective lens near the focal plane. Under the condition of 10x objective lens, when the sample is placed correctly, there should be blurry images, even relatively clear ones, which can be slightly adjusted and fine tuned.
⑵ Regarding entry and exit
Our experience differs significantly from the descriptions in other literature regarding the focusing issue after the conversion from low magnification to high magnification objectives. Due to the improvement of microscope manufacturing technology, the homogeneity of different objectives in microscopes is relatively good, especially for foreign products. Therefore, when focusing clearly at low magnification and turning to high magnification for observation, sometimes there is no need to focus again, and the image is already very clear; Alternatively, slightly increasing the object distance is sufficient, and the degree of adjustment is not limited to the concept of 1-3 turns, that is, 1-3 degrees (angle), which is an extremely small amount of adjustment.
⑶ Regarding the objective lens converter
When converting the objective lens, do not push it directly by hand, otherwise it may cause the thread of the fixed objective lens to loosen and slide, causing the optical axis to tilt. The objective lens of the microscope and the microscope digital camera system are screwed onto the objective converter. When changing different objective lenses, rotate the objective lens converter until a slight "click" sound and a sudden increase in tactile resistance are heard by the ear. At this point, the objective lens is in its normal working position: perpendicular to the plane of the stage.
