How to Calculate the Area of View under a Microscope
Reading pathological films under a microscope is one of the most important tasks in the work of pathologists. The results of microscope observation and recording are the scientific basis for clinical diagnosis. Correct and standard use of microscope, observation and recording of reading results are scientific. As we all know, the imaging of the microscope is first magnified and imaged by the objective lens, and then magnified by the eyepiece once to be observed by the naked eye. The field of view that can present an image is determined by the field of view of the eyepiece. It should be noted that the observation and recording described in this article are based on the observation and recording of the microscope through the eyepiece. Other optical paths that do not observe through the eyepiece are used to collect and record images, such as CCD, digital camera, and image collection by software operation, etc. The field number (field number, FN) of the microscope eyepiece is different, and the size of the field of view that can be seen under the microscope is different. Different areas have an impact on the count of the positive rate under the microscope. We should understand the relationship between the field number of the eyepiece and the area of the field of view . If the number of fields is small, the area of the field of view that can be seen is small; on the contrary, if the number of fields of view is large, the area of the field of view that can be seen is large.
1 Marking of the field number of the eyepiece
Microscope design and production have international standards, and the number of field of view will be marked on the eyepiece of the microscope, such as the Olympus BX50 microscope, the number of field of view of the eyepiece is 22 (the English and number marks before the value of 22 are the classification name and magnification of the eyepiece).
2 Actual field of view and calculation formula
On the specimen plane, the area (circular area) that the microscope can observe is called the actual field of view, also known as the field of view. Use the following formula to calculate the size of the area.
3 Objective lens magnification
The objective lens is an important optical component for microscope imaging. The commonly used objective lens magnifications of biological microscopes are 4, 10, 20, 40 and 100. The commonly used high magnification objective lens for pathological counting refers to 40.
4 intermediate magnification
View directly through the eyepiece regardless of intermediate magnifications. The intermediate magnification refers to the magnification of the CCD interface, photographic eyepiece and CCD components added to the optical path. Because most of the microscopes in use today are infinity imaging systems, with additional fluorescence observation, intrinsic difference observation, differential interference observation, etc., the components will not change the magnification and do not need to be considered.
5 Field of view under common eyepieces
The most commonly used eyepiece field number is 22. Various microscope manufacturers have successively designed and produced wide-field eyepieces with a field number of 25, and ultra-wide field eyepieces with a field number of 265. There are also eyepieces with smaller field numbers of 18 and 20.
