Similarities and differences between phase contrast microscope, inverted microscope and ordinary optical microscope
These microscopes are all optical microscopes, which use visible light as detection means, and are different from electron microscopes, scanning tunneling microscopes and atomic force microscopes.
Specifically:
Phase contrast microscope, also known as phase contrast microscope. Because the light will produce a slight phase difference when it passes through the transparent sample, and this phase difference can be converted into the change of amplitude or contrast in the image, so the phase difference can be used to image. It was invented by Fritz Zelnik in the 1930s when he was studying diffraction gratings. Therefore, it won the Nobel Prize in Physics in 1953. At present, it is widely used to provide contrast images for transparent specimens such as living cells and small organs and tissues.
Confocal microscope is an optical imaging method that uses point-by-point illumination and spatial pinhole modulation to remove the scattered light from the non-focal plane of the sample. Compared with traditional imaging methods, it can improve the optical resolution and visual contrast. The probe light emitted from a point light source is focused on the observed object through a lens. If the object is just in focus, the reflected light should be converged back to the light source through the original lens, which is called confocal. Confocal microscope adds a half-reflecting mirror to the reflected light path, which refracts the reflected light that has passed through the lens to other directions. There is a Pinhole at its focus, and the pinhole is located at the focus. Behind the baffle is a photomultiplier tube (PMT). It can be imagined that the reflected light before and after the focus of the detection light passes through this confocal system, and will not be focused on the small hole, but will be blocked by the baffle. So the photometer measures the intensity of reflected light at the focus. Its significance is that a translucent object can be scanned in three dimensions by moving the lens system. This idea was put forward by American scholar Marvin Minsky in 1953. After 30 years' development, a confocal microscope conforming to Marvin Minsky's ideal was developed by using laser as the light source.
Inverted microscope: the composition is the same as that of ordinary microscope, except that the objective lens and the illumination system are inverted, the former is under the stage and the latter is above the stage. Convenient operation and installation of other related image acquisition equipment.
Optical microscope is a kind of microscope that uses optical lens to produce image amplification effect. The light incident by the object is amplified by at least two optical systems (objective lens and eyepiece). Firstly, that objective len produces an enlarged real image, and the human eye observe the enlarged real image through an eyepiece which acts as a magnifying glass. The general optical microscope has several replaceable objective lenses, so that the observer can change the magnification as needed. These objective lenses are usually placed on a rotatable objective disc, and rotating the objective disc can make different eyepieces enter the optical path conveniently. Physicists discovered the law between magnification and resolution, and people realized that the resolution of optical microscope is limited. This limit of resolution limits the infinite improvement of magnification, and 1600 times has become the highest limit of magnification of optical microscope, which greatly limits the application of morphology in many fields.
The resolution of optical microscope is limited by the wavelength of light, and generally does not exceed 0.3 micron. If the microscope uses ultraviolet light as a light source or the object is placed in oil, the resolution can be improved. This platform becomes the basis for building other optical microscopic systems.
