Type of optical microscope
Optical microscopes can be classified into three, binocular and monocular microscopes according to the number of eyepieces used; According to whether the image has a three-dimensional sense can be divided into stereoscopic vision and non-stereoscopic vision microscope; According to the optical principle, it can be divided into polarized light, phase contrast, and differential interference contrast microscope, etc.
The type of light source can be divided into ordinary light, fluorescence, infrared light, and laser microscope. The type of receiver can be divided into visual, photographic, and television microscopes. Commonly used microscopes include binocular continuous ploidy microscope, polarizing microscope, ultraviolet fluorescence microscope, etc. Let’s take a closer look at the type of optical microscope.
1. Common microscope
(1) Metal microscope
This is a microscope for looking at metal surfaces. It is a falling illumination microscope, which shines light from the objective side onto the sample and uses the reflected light to look at it.
(2) Biological microscope
This is a microscope mainly used in medicine and biology. It is a transmission microscope.
(3) Open-field microscope
The most basic light microscope. When the sample is irradiated with uniform incident light, the fact that the transmitted light image has contrast is taken advantage of due to differences in light absorption in each part of the sample. Because there is no contrast with small absorptivities of samples to obtain clear images low staining is necessary.
(4) Darkfield microscope
The scattered and reflected light produced by applying light to the sample from an inclined direction is observed. In this method, in contrast to open-field microscopy, the background of the field of view is black and the sample appears to glow. The method can be achieved by inserting a darkfield condenser into an ordinary light microscope. Alternatively, observations can be made by darkfield methods by adjusting the phase-contrast microscope. Although not suitable for observing the fine structure of the surface or interior of an object, it can observe the presence of objects smaller than the wavelength of visible light with high contrast.
(5) Binocular stereo microscope
A microscope with two sets of optical systems that provide a vertical field of view and allow you to view relatively large samples in three dimensions. The observed magnification is usually several to tens of times. Another feature is to allow for viewing large samples and working under a microscope, ensuring the distance between the sample and the objective lens (working distance) (large focal length of the objective lens). Often used for product inspection.
(6) Inverted microscope
A microscope in which the objective lens is located below the object to be viewed. It is used in conjunction with the culture vessel to observe cultured cells and perform microoperations.
(7) Measuring microscope
A microscope was used to measure samples. The platform has a measuring machine and measuring scale, and also displays micrometers and templates in the field of view. There are many examples of systems using telecentric optics, in which the main ray is parallel to the optical axis of the lens in the microscope, which is necessary to minimize image distortion and to observe the accuracy of magnification.
(8) Anatomical microscope
Although it is called a microscope, the magnification is about several times greater, and the magnifying glass is fixed on the workbench.
2. Phase-contrast microscope
A microscope for viewing a colorless transparent sample but having a different refractive index. The phase delay of light passing through a medium with a high refractive index is greater than that of light passing through a medium with a low refractive index. This is a microscope that uses diffracted light associated with the phase difference. The condenser and diffraction light interfere with each other’s objective lens in different phases, which is observed by changing the phase difference. In this way, the internal structure of an almost transparent biological cell can be viewed. Phase-phase condensers and objective lenses are used. 1934  The Dutch Zernick (sieve plate (Frederick) Zernick) was designed. He won the Nobel Prize in physics in 1953.
3. Differential interference microscope
Light polarization properties and interference are obtained by using the properties of colorless transparent cells to observe such horizontal differences and metal surfaces under a microscope. The beam is separated by a polarizing element and a Wollaston prism (A Nomasky prism) and passed through the sample surface, and the differential value of the optical path difference generated in the sample is changed to form a contrast on the image surface. The amount of light separation on the sample surface is called the shear amount and can affect the resolution and contrast.
4. Polarizing microscope
Polarizing microscopes have the property of polarization, which changes the direction of vibration of light depending on the internal structure or crystal structure. This is the way to look at the polarization properties. The polarizer (polarizer) is placed at the concentrator of the optical microscope, the delay plate and polarizer (polarizer) is placed behind the objective, and the polarization and birefringence of the sample are observed as differences in brightness and color. As the polaroid rotates, bright crystals and so on are observed. It is used to observe crystals contained in biological samples, such as rocks and crystalline materials (parts of the extracellular matrix and abnormal deposits).
6. Fluorescence microscope
In fluorescence microscopy, in addition to observing the inherent spontaneous fluorescence of the sample, in some cases, the sample is observed after staining with fluorescent dyes, or through gene recombination for the expression of fluorescent proteins.
Unlike normal open-field microscopes, fluorescence microscopes illuminate samples with the light of a specific wavelength (excitation light). Since the wavelength of the fluorescence emitted from the sample is different from that of the excitation light, only a filter can be used to extract the fluorescence.
A high-pressure mercury lamp is often used as a light source. High-pressure mercury lamps emit light that is a mixture of several specific wavelengths. These are the wavelengths of the mercury emission spectrum, such as 254 nm, 365 nm (ultraviolet), 405 nm (blue), and 546 nm (green). The light is separated by a filter or prism and shines only light with the target wavelength as excitation light.
The light from the source is introduced from the middle of the microscope tube (between the eyepiece and the objective) through a chromatiscope that also acts as a wavelength filter and only reaches the observed portion of the sample through the objective lens. In general, a fall illumination fluorescence microscope that looks at fluorescence through the same objective lens is usually used. In many cases, the fluorescence microscope can be used as a fluorescence microscope by connecting the optional equipment of the fluorescence microscope to the ordinary bright field microscope.
7. Confocal laser microscope
As the light source of the gas laser, the semiconductor laser is used as the light source of the white light source. The laser is scanned from the objective lens, the fluorescence from the excited sample (or the light reflected from the sample) is passed through the pinhole, detected using detection equipment, and the image is reconstructed on a computer.
Since fluorescence from outside the same focal (confocal) plane can be obscured by the use of pinholes, images of optical slices whose thickness depends on the numerical aperture can be obtained. Since the 1990s, it has become very popular in biology, combined with convenient sample preparation compared to transmission electron microscopy. The disadvantage is the high price.
8. Total reflection illumination fluorescence microscope
The invention relates to a method using total reflection irradiation the fluorescence microscope. Total reflection occurs when light enters a medium with a high refractive index at an angle greater than a certain Angle into a medium with a low refractive index. In total reflection, there is light penetration at the interface (evasive wave), preparation, etc., and a glass slide with a large refractive index, so these phenomena also occur at the interface where it is smaller water.
The use of illumination makes it possible to observe only selective fluorescence of the total reflection of the sample near the glass surface with a fluorescence microscope. The ability to detect fluorescence can even be realized by a biomolecule, thus aiding single-molecule cell biology. Developed in Japan in the 1990s.
9. Raman microscope
Raman microscope is also called laser Raman microscope. Images are obtained by detecting Raman scattering light produced when a sample is irradiated with a laser. Raman wavelength scatters light (wavelength offset), molecules present in the sample, bind and crystallize according to material-specific values such as the frequency of the grating. Therefore, the substance contained in the sample can be identified from the Raman scattering spectrum of the sample and its distribution can be observed at the same time.
Raman scattering light is weak, and the time required for detection and imaging was not realistic in the past, but it can be mounted on a microscope by designing an optical system and shortening the computational time associated with processor development. Turned out to be. Some obtain spatial resolution by confocal optical systems, some separate Raman scattered light by narrowband interference filters, and some use nonlinear Raman effects. The ability to identify matter is not as good as mass spectrometry or X-ray elemental analysis, but the ability to observe the viability of untreated objects is a huge advantage.
10. Nonlinear optical microscope
Nonlinear optical microscopy is a microscope that uses nonlinear optical phenomena such as optical harmonic generation, optical mixing, optical parametric effects, multi-photon transitions, nonlinear refractive index changes, and electric-field-related refractive index changes.