There are many classification methods for optical microscopes: they can be divided into binocular and monocular microscopes according to the number of eyepieces used; stereoscopic and non-stereoscopic microscopes can be divided according to whether the images have stereoscopic effects; Phase microscope, etc.; according to the optical principle can be divided into polarized light, phase contrast and differential interference contrast microscope; according to the type of light source can be divided into ordinary light, fluorescence, ultraviolet light, infrared light and laser microscope; etc. Visual, digital (camera) microscopes, etc. Commonly used microscopes include binocular stereo microscopes, metallographic microscopes, polarized microscopes, and fluorescence microscopes.
1. Binocular stereo microscope
A binocular stereo microscope, also known as a "solid microscope" or a "dissecting mirror", is a visual instrument with a positive stereoscopic effect. It is widely used in biotechnology and medicine for slicing operations and microsurgery; in the industry for observation, assembly, inspection, etc. of tiny parts and integrated circuits. It has the following characteristics:
(1) Using the two-channel optical path, the left and right beams in the binocular tube are not parallel, but have a certain angle - the body angle of view (generally 12 degrees - 15 degrees), providing a stereoscopic effect for the left and right eyes. Image. It is essentially two juxtaposed microscopes placed side by side. The optical axes of the two barrels are equivalent to the angle of view formed when people observe an object with binoculars, thereby forming a three-dimensional stereoscopic image.
(2) It is erect, easy to operate and dissected, because the prism below the eyepiece reverses the image.
(3) Although the magnification is not as good as that of a conventional microscope, its working distance is very long.
(4) The depth of focus is large, which is convenient for observing the full layer of the object to be inspected.
(5) The diameter of the field of view is large.
At present, the optical structure of the stereoscopic mirror is: a common primary objective lens, the two beams after imaging the object are separated by two sets of intermediate objective lenses---the zoom lens, and integrated into the eyepiece and then imaged by the respective eyepieces. The magnification change is obtained by changing the distance between the intermediate mirror groups, so it is also called "Zoom-stereomicroscope". With the requirements of the application, the current stereo lens can be equipped with a wide range of optional accessories such as fluorescence, photography, camera, cold light source and so on.
2. Metallographic microscope
Metallographic microscopes are microscopes designed to observe the metallographic structure of opaque objects such as metals and minerals. These opaque objects cannot be observed in ordinary transmitted light microscopes, so the main difference between metallographic and ordinary microscopes is that the former reflects light and the latter illuminates with transmitted light. In the metallographic microscope, the illumination beam is directed from the objective lens to the surface of the object to be observed, reflected by the object surface, and returned to the objective lens for imaging. This kind of reflective illumination is also widely used in the inspection of integrated circuit silicon wafers.
3. Polarizing microscope (Polarizing microscope)
A polarizing microscope is a microscope used to study so-called transparent and opaque anisotropic materials. Any substance with birefringence can be clearly distinguished under a polarizing microscope. Of course, these substances can also be observed by dyeing, but some are impossible, and a polarizing microscope must be used.
(1) Characteristics of polarized light microscope
A method of microscopically changing ordinary light to polarized light to identify whether a substance is monorefracted (for each other) or birefringent (anisotropic). Birefringence is a fundamental property of crystals. Therefore, polarized light microscopes are widely used in fields such as minerals and chemistry, and are also used in biology and botany.
(2) The basic principle of polarized light microscopy
The principle of polarized light microscopy is complicated. It is not introduced here. The polarizing microscope must have the following accessories: polarizer, analyzer, compensator or phase plate, special stress-free objective lens, rotating stage.
(3) The way of polarized microscopy
a. Normal phase microscopy (Orthscope): also known as undistorted microscopy, which is characterized by the use of low magnification objectives, without Bertrand lens (BertrandLens), the subject can be directly studied with polarized light. At the same time, in order to make the illumination aperture smaller, the upper lens of the concentrating mirror is pushed away. Positive phase microscopy is used to check the birefringence of an object.
b. Conoscope: Also known as interferometric microscopy, the interference pattern produced by interference of polarized light is studied. This method is used to observe the uniaxial or biaxial properties of an object. In this method, illumination is performed with a strongly concentrated polarized beam.
(4) Requirements for the polarized microscope on the device
a. Light source: Monochromatic light is preferred because the speed of light, the refractive index, and the interference phenomenon vary depending on the wavelength. General light can be used for general microscopy.
b. Eyepiece: An eyepiece with a crosshair.
c. Condenser: In order to obtain parallel polarized light, a shake-out condenser that can push out the upper lens should be used.
d. Bertrand lens: An auxiliary component in the concentrating beam path, which is an auxiliary lens that amplifies all primary phases caused by the object into a secondary phase. It ensures that the eyepiece is used to observe the flat pattern formed in the back focal plane of the objective lens.
(5) Requirements for polarized microscopy
a. The center of the stage is coaxial with the optical axis.
b. The polarizer and the analyzer should be in an orthogonal position.
c. The film should not be too thin.
4. Fluorescence microscope
In a fluorescence microscope, a subject that has been stained with fluorescein is irradiated with a short-wavelength light to be excited to generate long-wavelength fluorescence, and then observed. Fluorescence microscopy is widely used in biology, medicine and other fields.
(1) Fluorescence microscopes are generally classified into two types, transmissive and epi-illuminated.
a. Transmissive type: The excitation light is from below the object to be inspected, and the condensing mirror is a dark field condensing mirror, so that the excitation light does not enter the objective lens, and the fluorescence enters the objective lens. It is bright at low magnification and dark at high magnification. It is difficult to operate in oil immersion and adjustment, especially in low-light illumination range, but it can get a very dark background. Transmissive type is not used for non-transparent objects to be inspected.
b. Falling type: Transmissive type is almost eliminated now. The new type of fluorescence microscope is mostly in the form of a falling beam. The light source comes from the upper part of the object to be inspected and has a beam splitter in the light path, so it is suitable for both transparent and opaque objects to be inspected. Since the objective lens functions as a condensing mirror, it is not only easy to operate, but also can achieve uniform illumination of the entire field of view from low to high.
(2) Precautions for fluoroscopy
a. When the excitation light is irradiated for a long time, the fluorescence is attenuated and quenched, so that the observation time is shortened as much as possible, and when the light is not observed, the baffle is used to cover the excitation light.
b. When using oil mirror observation, apply "no fluorescent oil".
c. Fluorescence is almost weak and should be performed in a darker room.
d. It is better to install the voltage regulator for the power supply. Otherwise, the unstable voltage will not only reduce the life of the mercury lamp, but also affect the effect of the microscopic inspection.
Many emerging biological research fields are currently applied to fluorescence microscopy, such as gene in situ hybridization (FISH) and the like.
5. Phase contrast microscope (Phasecontrastmicroscope)
In the development of optical microscopy, the successful invention of phase contrast microscopy is an important achievement in modern microscope technology. We know that the human eye can only distinguish the wavelength (color) and amplitude (brightness) of the light wave. For the colorless and bright biological specimen, when the light passes, the wavelength and amplitude do not change much, and it is difficult to observe the specimen when viewed in the bright field. .
The phase contrast microscope uses the difference of the optical paths of the object to be examined, that is, the interference phenomenon of the light is effectively utilized, and the phase difference that is indistinguishable from the human eye is changed into a resolvable amplitude difference, even if it is a colorless and transparent substance. Can be clearly visible. This greatly facilitates the observation of living cells, so phase contrast microscopy is widely used in inverted microscopes.
Phase contrast microscopy is different from brightfield on the device and has some special requirements:
a. Ringslit: It is mounted under the concentrating mirror and combined with the concentrating mirror---phase concentrating concentrator. It is installed in a circular disc with different sizes of ring diaphragms, and is marked with 10X, 20X, 40X, 100X and the like on the outside, and is used together with the objective lens of the corresponding multiple.
b. Phaseplate: installed in the back focal plane of the objective lens, it is divided into two parts, one is the part that passes through the direct light, which is a translucent ring, called the conjugate surface; the other is the diffracted light. Part, "compensation surface". The objective lens with phase plate is called "phase contrast objective", and the word "Ph" is often used on the outer casing.
Phase contrast microscopy is a relatively complicated method of microscopy. To get good observation, the debugging of the microscope is very important. In addition to this, you should also pay attention to the following aspects:
a. The light source is strong, and all aperture apertures are turned on;
b. Use a color filter to make the light wave nearly monochrome.
6. Differential Interference Contrast (Differential Interference ContrastDIC)
Differential interference contrast microscopy appeared in the 1960s. It not only can observe colorless and transparent objects, but also the image shows a three-dimensional sense of relief and has some advantages that can not be achieved by phase contrast microscopy. To be realistic.
(1) Principle
Differential interference contrast microscopy uses a special Wollaston prism to decompose the beam. The vibration directions of the split beams are perpendicular to each other and the intensity is equal. The beams pass through the object to be inspected at two points close to each other, and the phases are slightly different. Since the splitting distance of the two beams is extremely small, no ghost phenomenon occurs, and the image exhibits a three-dimensional three-dimensional feeling.
(2) Special components required for differential interference contrast microscopy:
a. polarizer
b. Detector
c. Wollaston prism 2
(3) Precautions for differential interference contrast microscopy
a. Due to the high sensitivity of differential interference, the surface of the sheet should be free of dirt and dust.
b. A substance with birefringence cannot achieve the effect of differential interference contrast microscopy.
c. When using inverted microscopy for inverted microscopy, plastic culture dishes cannot be used.
7. Inverted microscope (Invertedmicroscope)
The inverted microscope is used for microscopic observation of tissue culture, cell culture, plankton, environmental protection, food inspection, etc. in the fields of biology and medicine.
Due to the limitations of the above sample characteristics, the objects to be inspected are placed in a petri dish (or a culture flask), so that the objective lens of the inverted microscope and the concentrating mirror have a long working distance, and can directly perform microscopic examination on the object to be inspected in the culture dish. Observation and research. Therefore, the positions of the objective lens, the condensing mirror, and the light source are reversed, so it is called an "inverted microscope."
Due to the limitation of the working distance, the maximum magnification of the inverted microscope objective is 60X. In general, inverted microscopes are equipped with 4X, 10X, 20X, and 40X phase difference objectives, because inverted microscopes are mostly used for colorless and transparent living observation. If you have special needs, you can also choose other accessories to complete the observation of differential interference, fluorescence and simple polarized light.
The inverted microscope is widely used in the fields of patch-clamp, transgeneICSI and so on.
8. Digital microscope
A digital microscope is a microscope in which a camera (ie, a television camera target or a charge coupler) is used as a receiving element. A camera is mounted on the real image side of the microscope instead of the human eye as a receiver, and the optical image is converted into an image of an electrical signal by the photoelectric device, and then subjected to size detection, particle counting, and the like. This kind of microscope can be used in conjunction with a computer, which facilitates the automation of inspection and information processing, and is often used in applications where a lot of cumbersome inspection work is required.
Rape Seeds,Oil Seed Rape,Colza Seeds,Rapeseed Seeds
XIKE AGRICULTURAL GROUP CO . .LTD. , https://www.laoseed.com