Objective lens is to determine the performance of the microscope is the most important component, installed in the objective converter, close to the object being observed, so it is called the objective lens or objective lens.
1, the classification of the objective lens
objective lens according to the different conditions of use can be divided into dry objective lens and immersion objective; which can be divided into water immersion objective lens and oil immersion objective lens (commonly used magnification of 90-100 times) according to the different magnification can be divided into low-magnification objective lens (10 times the following), in the magnification of the objective lens (20 times or so) high-magnification objective lens (40-65 times).
2, the main parameters of the objective lens
objective lens main parameters include: magnification, numerical aperture and working distance
①, magnification refers to the eye to see the size of the image and the size of the corresponding specimen ratio. It refers to the length of the ratio rather than the area of the ratio. The total magnification of a microscope is equal to the product of the magnification of the objective lens and the eyepiece.
②, the numerical aperture, also called the mirror mouth rate, abbreviated NA or A, is the main parameter of the objective lens and the concentrator, and is directly proportional to the resolving power of the microscope.
(iii) The working distance is the distance from the front lens of the objective lens to the top of the coverslip of the specimen when the observed specimen is clearest. The working distance of the objective lens is related to the focal length of the objective lens, the longer the focal length of the objective lens, the lower the magnification, the longer the working distance. 10 times the effective working distance of the objective lens is 6.5mm, 40 times the effective working distance of the objective lens is 0.48mm. 3, the role of the objective lens.
3, the role of the objective lens
objective lens is the role of the specimen for the first time for magnification, it is to determine the performance of the microscope's most important components - the level of resolution. Resolving power is also known as resolution or resolving power. The size of the resolving power is expressed in terms of the value of the resolving distance (the smallest distance between the two object points that can be resolved). In the visual distance (25cm), the normal human eye can see the two object points 0.073mm apart, the value of 0.073mm, that is, the normal human eye resolving distance. The smaller the resolving distance of the microscope, the higher its resolving power, that is, the better its performance. The size of the resolving power of the microscope is determined by the resolving power of the objective lens, which is determined by its numerical aperture and the wavelength of the illumination light.
