Estimation of optical microscope magnification
Optical microscopes can be divided into stereo microscopes, upright microscopes and inverted microscopes. They are widely used in various fields such as biology, materials science, mining, and food safety. Limited by the light source and filling medium used by optical microscopes, the ultimate resolution of optical microscopes can reach as low as 200 nm. Observation objects smaller than 200 nm require laser confocal microscopy, super-resolution fluorescence microscopy, scanning electron microscopy, atomic force microscopy, etc. to observe clearly. The magnification effect of an optical microscope on an object is not to magnify the entire area of the object, but to magnify the length or width of the object. Normally, the smallest object that the human eye can distinguish within the photopic distance range is 0.1-0.3 mm. So when actually using an optical microscope to observe an object, how many times must the object be magnified before the object can be clearly observed with the human eye? This article gives a simple estimate of optical microscope magnification.
There are two calculation methods for the magnification of an optical microscope:
(1) Optical magnification. Optical magnification refers to the magnified effect of an object observed through the microscope eyepiece. This magnification result is called optical magnification. The calculation of optical magnification is relatively simple, that is, objective lens magnification × eyepiece magnification. Taking the magnification calculation of a stereo microscope as an example, if the continuous zoom body is 0.7-4.5 and the eyepiece is 10 times, then the magnification of this stereo microscope is 7-45 times. If the microscope has an objective lens and an eyepiece, then directly multiply the magnification of the objective lens by the magnification of the eyepiece to get the total magnification of the microscope.
(2) Digital magnification. Digital magnification usually refers to the magnification of an object after being imaged by an external device. Currently, there are many trinocular microscopes on the market, which are connected to computers, LCD monitors and other imaging devices through CCD for imaging observation. How many times will the object be magnified after connecting an external device? Two calculation methods are given.
(a) If there is accurate data on the actual size of the object being observed, it can be calculated by the formula: the actual magnification factor of the object = the enlarged size of the object / the actual size of the object. If the actual size of the object is 2 μm, after it is imaged on the monitor, you can use a ruler to measure the length of the imaged object. If the measured length of an object is 2 mm, then the object is magnified 1000 times.
(b) If you do not have a clear idea of the size of the object, you can calculate it with the following formula.
Digital magnification = objective lens magnification × {25.4 × screen size (inches)/length of CCD diagonal} × magnification of the connecting ring
