Microscope objective lens introduction
There are many types of objective lenses, which can be classified from different angles: According to the medium between the front lens of the objective lens and the object to be inspected, it can be divided into:
①Dry objective lens uses air as the medium, such as the commonly used objective lens below 40×, the numerical aperture is less than 1.
②Oil immersion objective lens usually uses cedar oil as the medium, this objective lens is also called oil lens, its magnification is 90×~100×, and the numerical aperture value is greater than 1.
Numerical aperture (numerical aperture, N.A.), also known as mirror aperture ratio (or aperture ratio). Both the objective lens and the condenser are marked with their numerical aperture, which is the main parameter of the objective lens and condenser, and is also the most important index to judge their performance. The performance of an objective depends on the numerical aperture of the objective, the larger the numerical aperture, the better the performance of the objective. The numerical aperture is closely related to various properties of the microscope, it reflects the size of the resolution of the objective lens, the larger the value, the higher the resolution.
The working distance refers to the distance between the lower surface of the objective lens and the upper surface of the cover glass when the object image is adjusted clearly; the greater the magnification of the objective lens, the smaller the working distance.
