The difference between electron microscope and digital microscope
"Digital microscope" is actually a digital imaging device added to the optical microscope, which can directly display the image formed by the microscope on the computer screen. It is based on the optical microscope, and the imaging principle of the electron microscope is fundamental The difference. Here, we need to distinguish between resolution and magnification. When a fine object is zoomed in and imaged, its high resolution depends on the wavelength of the reflected light wave. The shorter the wavelength, the higher the resolution. Electron microscopes use X-ray imaging with a wavelength much shorter than ordinary visible light, of course, has very high resolution, while the magnification of ordinary "digital microscopes" can be large, but the resolution cannot be improved.
The resolution of an optical microscope is related to the wavelength of the light wave. For objects close to and smaller than the wavelength of light, the optical microscope is powerless. The wavelength of electron movement is much shorter than the wavelength of light wave, so smaller objects can be seen. An optical microscope is a magnified imaging system composed of a set of optical lenses, while an electron microscope has electron flow instead of visible light, a magnetic field instead of lenses, and electron movement instead of photons, so that objects smaller than those that can be seen by the optical system can be seen .
An electron microscope is a large-scale instrument that uses electron beams as the illumination source to form images on a fluorescent screen through the transmission or reflection of the electron flow on the sample and the multi-stage magnification of the electromagnetic lens, while the optical microscope uses visible light illumination to form a magnified image of tiny objects optical instruments. In summary, electron microscopes differ from optical microscopes in the following aspects:
1. Different lighting sources. The illumination source used by the electron microscope is the electron flow emitted by the electron gun, while the illumination source of the light microscope is visible light (sunlight or light). Since the wavelength of the electron flow is much shorter than that of the light wave, the magnification and resolution of the electron microscope are significantly higher than that of the light microscope.
2. Different lenses. The magnifying objective lens in the electron microscope is an electromagnetic lens (an annular electromagnetic coil that can generate a magnetic field in the central part), while the objective lens of the light microscope is an optical lens made of glass. There are three groups of electromagnetic lenses in the electron microscope, which are equivalent to the functions of the condenser lens, objective lens and eyepiece in the light microscope.
3. The imaging principle is different. In the electron microscope, the electron beam acting on the sample to be inspected is amplified by the electromagnetic lens and reaches the imaging on the fluorescent screen or acting on the photosensitive film for imaging. The mechanism of the difference in the density of electrons is that when the electron beam acts on the sample to be tested, the incident electrons collide with the atoms of the substance to produce scattering. Since different parts of the sample have different scattering degrees for electrons, the electron image of the sample is presented in shades. . The object image of the sample in the light microscope is presented as a difference in brightness, which is caused by the difference in the amount of light attracted by the different structures of the sample to be inspected.
4. The specimen preparation methods used are different. The preparation procedure of tissue cell specimens used for electron microscope observation is complicated, and the technical difficulty and cost are high. Special reagents and operations are required in the links of material collection, fixation, dehydration and embedding. Finally, the embedded tissue blocks need to be put into Cut into ultra-thin specimen slices with a thickness of 50-100 nm in an ultra-microtome. The specimens observed by light microscopy are generally placed on glass slides, such as ordinary tissue section specimens, cell smear specimens, tissue compression specimens, and cell drop specimens.
