The proper matching of objective and eyepiece of optical microscope
There are two main considerations when selecting objectives and eyepieces:
First, matching in category. That is, all flat-field objective lenses should be used with special flat-field eyepieces.
Second, a reasonable match in magnification. In a certain magnification, objective lenses and eyepieces can be arbitrarily combined, but the combination of the premise is mainly to consider the effective magnification, which is the correct use of the microscope is an important law. Effective magnification of the microscope for the use of the objective lens numerical aperture 500 to 1000 times, that is, the product of the magnification of the objective lens and eyepiece is equal to the objective lens numerical aperture of 500 to 1000 times.
If you use a 40X objective lens with a numerical aperture of 0.65 to observe a specimen, how large should you choose?
The total effective magnification is first calculated based on the effective magnification, and then divided by 40, which is the magnification of the eyepiece to be selected. The calculation process is: (0.65×500～0.65×1000)÷40≈8～16. That is to say, if the numerical aperture is 0.65, the eyepiece should be selected to match with the effective magnification (500～1000 times) in the range of 8～16 times. If the eyepiece magnification is too low, the total magnification is too small, the resolution of the objective lens can not give full play to the details that can be recognized, due to the total magnification is too small, crowded together and difficult to distinguish. And higher than 16 times the eyepiece magnification is called "empty magnification", the impact of the details of the resolution, not the slightest improvement, but the depth of clarity is small, can not clearly reflect the structure of different levels.
