Formula for the biological microscope's eyepiece micrometer
When using a biological microscope, it is sometimes necessary to measure the length of an object to be observed. Since the observed object is very small, it is impossible to measure it directly with conventional measuring tools, so we need to use a special micrometer for the microscope. To measure the length of the object to be inspected, two tools are needed, one of which is installed in the eyepiece, which is called the eyepiece micrometer; the other is placed on the stage, which is a special cover glass. You can see that there is a small circular area in the middle of it, with a small scale engraved inside. The general total length is 1mm, and there are 100 small grids in total, that is, the distance between each small grid is 10um. Its function is to determine the length of each grid of the eyepiece micrometer under biological microscope observation.
When in use, we need to put the eyepiece micrometer into the eyepiece tube. The specific operation is: first pull the eyepiece out of the microscope, there is a gear-shaped circular structure at the end away from the lens (that is, the place we usually look at when observing), unscrew it, and then put the eyepiece micrometer into it. Note that the front side should be placed on the field diaphragm, then screw it back, and put it back into the eyepiece. Some microscopes are not allowed to be disassembled due to their precise structure, and need to be specially equipped with eyepieces with micrometers. Then put the micrometer scale on the stage, adjust the focal length of the microscope until the clear scale of the scale can be seen. At this time, adjust so that one end of the two rulers coincides on the full scale, and then find where the other end coincides, and count the number of grids of their overlap to calculate the actual magnification of the eyepiece micrometer under magnification.
The specific calculation formula is as follows:
Each division of eyepiece micrometer = (number of overlapped rulers X10) ÷ number of overlapped divisions of the eyepiece ruler. As shown in the figure above, the number of overlapping grids of the stage ruler is 4 grids, and the number of overlapping grids of the eyepiece micrometer is 10 grids. From this, the length represented by each grid of the eyepiece micrometer can be calculated as: (4X10)/10=4um.
After determining the length represented by each grid of the eyepiece micrometer, remove the ruler, and then use it to determine the actual length of the object to be inspected. Since the biological microscope has multiple objective lenses, each objective lens has a different magnification, and the actual length represented by the eyepiece micrometer is different under different magnifications, so it should be recalibrated when switching magnifications.
