Formula for biological microscope eyepiece micrometer
When using a biological microscope, it is sometimes necessary to measure the length of the object being observed. Due to the small size of the observed object, it is not possible to directly measure it using conventional measuring tools, which requires the use of a microscope specific micrometer. To measure the length of the object being tested, two tools are needed, one of which is installed in the eyepiece and is called the eyepiece micrometer; A piece placed on the stage is a special cover glass, with a small circular area in the middle that is engraved with a small scale. The total length is generally 1mm, with a total of 100 small grids, which means the distance between each grid is 10um. Its function is to determine the length represented by each grid of the eyepiece micrometer under biological microscopy observation.
When using, we need to first install the eyepiece micrometer into the eyepiece tube. The specific operation is to first remove the eyepiece from the microscope, and there is a gear shaped circular structure at one end away from the lens (which is the place we usually observe). Unscrew it, then install the eyepiece micrometer into it, making sure to place the front side on the field of view diaphragm, then screw it back and put it back into the eyepiece. Some microscopes, due to their precise structure, do not allow disassembly and require specialized eyepieces equipped with micrometers. Then place the micrometer ruler on the stage and adjust the focal length of the microscope until a clear scale of the ruler can be seen. At this point, adjust so that one end of the two rulers coincides with the entire scale, then find where the other end coincides, and count the number of grids where they overlap to calculate the actual magnification of the eyepiece micrometer under magnification.
The specific calculation formula is as follows:
Each grid of the eyepiece micrometer is equal to (the number of overlapping grids of the platform scale X10) ÷ the number of overlapping grids of the mesh scale. As shown in the above figure, the overlapping grid of the ruler is 4 grids, and the overlapping grid of the eyepiece micrometer is 10 grids. From this, it can be calculated that the length represented by each grid of the eyepiece micrometer is (4X10)/10=4um.
After determining the length represented by each grid of the eyepiece micrometer, remove the ruler and use it to determine the actual length of the object being tested. Due to the fact that biological microscopes have multiple objective lenses, each with different magnifications, the actual length represented by the eyepiece micrometer varies at different magnifications. Therefore, recalibration is necessary when switching magnification.
