Magnification and effective magnification of optical microscope performance
The total magnification Γ of the microscope should be the product of the objective lens magnification β and the eyepiece magnification Γ1: Γ = βΓ1, because of the two magnifications by the objective lens and the eyepiece.
Obviously, a microscope can have a much higher magnification compared to a loupe, and the magnification of a microscope can be easily changed by switching the objective and eyepiece with different magnifications.
Magnification is also an important parameter of a microscope, but one should not blindly believe that the higher the magnification the better. The limit of microscope magnification is the effective magnification.
Resolution and magnification are two different but related concepts. There is a relationship between: 500NA<Γ<1000NA
Elected objective lens numerical aperture is not large enough, that is, the resolution is not high enough, the microscope can not distinguish between the microstructure of the object, even if the magnification is increased excessively, can only get a large outline but the details of the image is not clear, known as the invalid magnification. Conversely, if the resolution has to meet the requirements of the magnification is not enough, the microscope has the ability to distinguish, but because the image is too small and still can not be clearly seen by the human eye. So in order to give full play to the resolving power of the microscope, should make the numerical aperture and the total magnification of the microscope reasonable match.
Depth of Focus
Depth of focus for the focal depth of the abbreviation, that is, in the use of microscopes, when the focus is aligned with an object, not only is located in the plane of the point of the points can be seen clearly, but also in the upper and lower part of the plane within a certain thickness, but also can be seen clearly, this clear part of the thickness is the depth of focus. Depth of focus is large, you can see the whole layer of the object being examined, while the depth of focus is small, you can only see a thin layer of the object being examined, depth of focus and other technical parameters have the following relationship:
1, the depth of focus and the total magnification and the numerical aperture of the objective lens is inversely proportional.
2, the focal depth is large, the resolution is reduced.
Because of the large depth of field of the low-magnification objective lens, it causes difficulties when taking photographs with the low-magnification objective lens. In micrography will be described in detail.
