What is the numerical aperture in microscope parameters
1, resolution
Microscope resolution refers to the microscope can be clearly distinguished by the minimum distance between the two object points, also known as the "discrimination rate". The formula is σ = λ / NA where σ is the minimum resolution distance; λ is the wavelength of light; NA for the numerical aperture of the objective lens. The resolution of the objective lens is determined by the NA value of the objective lens and the wavelength of the illumination source.
2, magnification and effective magnification
After the objective lens and the eyepiece of the two magnification, so the total magnification of the microscope is the product of the objective lens magnification and eyepiece magnification, the limit of the microscope magnification that is the effective magnification.
3, numerical aperture (NA)
Numerical aperture abbreviated NA, numerical aperture is the main technical parameters of the objective lens and condenser lens, is to determine the two (especially for the objective lens) the performance of the important signs of high and low. The size of its value, respectively, is engraved on the objective lens and the shell of the condenser lens. It is the object lens before the lens and the object to be examined between the refractive index of the medium (n) and the aperture angle (u) half of the sine of the product. Expressed in the formula as follows: NA = nsinu/2. It is proportional to the resolution, proportional to the magnification, and inversely proportional to the depth of focus, NA value increases, the field of view width and working distance will be correspondingly smaller.
4, 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 of 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.
5. Diameter of the field of view
The bright circular range is called the field of view, its size is determined by the eyepiece in the field of view diaphragm. The diameter of the field of view, also known as the width of the field of view, is the circular field of view seen under the microscope can accommodate the actual scope of the object being examined. The larger the diameter of the field of view, the easier it is to observe.
Field of view diameter = eyepiece field of view / objective lens magnification
6、Coverage difference
Due to the thickness of the coverslip is not standardized, the light from the coverslip into the air after refraction of the light path has changed, resulting in a phase difference, which is the coverage difference. International regulations, the standard thickness of the coverslip is 0.17mm, the license range of 0.16-0.18mm, in the manufacture of the objective lens has been the thickness of the range of phase difference calculated. Objective housing labeled 0.17, that is, the objective lens requires the thickness of the coverslip.
7, working distance (WD)
Working distance, also known as the object distance, that is, the distance between the surface of the lens in front of the objective lens to the object being examined.
