Classification and use of optical microscopes
There are many classification methods of optical microscopes: according to the number of eyepieces used, it can be divided into binocular microscope and monocular microscope; according to whether the image has a stereo effect, it can be divided into stereo microscope and non-stereo microscope; according to the observation object, it can be divided into biological microscope and Metallographic microscope, etc.; according to the optical principle, it can be divided into polarized light microscope, phase contrast microscope and differential interference microscope; according to the type of light source, it can be divided into ordinary light, fluorescence, ultraviolet light, infrared light and laser microscope, etc.; according to the type of receiver, it It can be divided into visual, digital (video) microscopes, etc. Therefore, before purchasing a microscope, you must decide which microscope is right for you. Commonly used optical microscopes include biological microscopes, stereo microscopes, metallographic microscopes, polarized light microscopes, fluorescence microscopes, phase contrast microscopes, and inverted microscopes.
Microscope
The magnification of biological microscope is generally between 40X-2000X, and the light source is transmitted light. Biological microscopes are used in medical and health institutions, colleges and universities, and scientific research institutes to observe microorganisms, cells, bacteria, tissue cultures, suspensions, sediments, etc. At the same time, other transparent or translucent objects, powders, and fine particles can be observed. The proliferation and division process of cells, bacteria, etc. in the culture medium can be continuously observed. Widely used in cytology, parasitology, oncology, immunology, genetic engineering, industrial microbiology, botany and other fields. It is an inspection equipment for food factories and drinking water factories to carry out QS and HACCP certification.
Stereo microscope
Stereo microscope, also known as "solid microscope" or "dissecting mirror", is a visual instrument with an upright three-dimensional effect. The magnification of the stereo microscope is around 7X-45X, and it can also be enlarged to 90X, 180X, and 225X. Widely used in slice surgery and microsurgery in the biomedical field; in industry, for observation, assembly and inspection of small parts and integrated circuits. It uses a dual channel optical path. The left and right light beams in the binocular tube are not parallel, but have a certain angle - a stereoscopic viewing angle (usually 12-15 degrees), which provides a stereoscopic image for the left and right eyes. It is essentially two single-tube microscopes placed side by side. The optical axes of the two lens barrels constitute the angle of view formed when people use binoculars to observe objects to form a three-dimensional stereoscopic image.
At present, the optical structure of stereo microscopes consists of common primary objective lenses. After imaging the object, the two beams are separated by two sets of intermediate objective lenses, the zoom lens, and the angle of view is integrated and then imaged through their respective eyepieces. Its magnification is changed by changing the intermediate lens group. It is also called "Continuous Zoom Stereo Microscope". Stereo microscopes can be equipped with a wealth of optional accessories according to application requirements, such as fluorescence, photography, imaging, cold light sources, etc.
metallographic microscope
The magnification of the metallographic microscope is in the range of 50X-1000X. It is mainly used to observe various opaque materials such as metal, identify and analyze the internal structure and organization. It is suitable for factories and mines, colleges and universities, scientific research and other departments. The instrument is equipped with a camera device, which can collect metallographic diagrams, measure and analyze diagrams, and perform functions such as image editing, output, storage and management. A metallographic microscope is a microscope specially used to observe opaque objects such as metals and minerals. These opaque objects cannot be observed in ordinary transmitted light microscopes, so metallographic microscopes mainly focus on reflected light. In a metallurgical microscope, the illumination beam is projected from the objective lens to the surface of the object to be observed, reflected by the surface of the object and then returned to the objective lens for imaging. This reflective illumination method is also widely used in the inspection of integrated circuit silicon wafers. Now metallographic microscopes can also choose to have transmitted light, which is convenient for observing transparent objects and some powdery particle samples.
Polarizing microscope
A polarizing microscope is a microscope used to study so-called transparent and opaque anisotropic materials. The focus of polarizing microscopes is to add polarizers and analyzers. For reflective or birefringent samples, it is equivalent to cutting off a part of the stray light to make the product clear, such as ore, crystal, etc. Any substance with birefringence can be clearly resolved under a polarizing microscope. Of course, these substances can also be observed by staining, but some are impossible and must be observed with a polarizing microscope. Converting ordinary light into polarized light is a method used in a microscope to identify whether a substance is singly refracting (anisotropic) or birefringent (anisotropic). Therefore, polarizing microscopes are widely used in minerals, chemistry and other fields. It also has applications in biology and botany.
fluorescence microscope
The fluorescence microscope uses ultraviolet light as the light source to illuminate the object to be inspected to emit fluorescence, and then observe the shape and position of the object under the microscope. Fluorescence microscopy is used to study the absorption and transport of intracellular substances, the distribution and localization of chemical substances, etc. Certain substances in cells, such as chlorophyll, fluoresce when exposed to UV light; some substances cannot fluoresce themselves, but can also fluoresce under UV light if they are stained with fluorescent dyes or fluorescent antibodies. Fluorescence microscopy is the right tool for qualitative and quantitative studies of such substances.
Fluorescence microscopes are generally divided into two types: transmission type and epitaxy type. Transmission type: The excitation light comes from below the object to be inspected, the condenser is a dark field condenser, 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. Difficulty in oil immersion and adjustment operations. It is difficult to determine the illumination range at low magnifications, but a very dark field of view background can be obtained. The transmissive type is not used for non-transparent objects to be inspected. Epi-type: The transmission type has been basically eliminated at present. Most of the new fluorescence microscopes are of the external emission type. The light source comes from above the inspected object. It 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 acts as a condenser, it is not only easy to operate, but also can achieve uniform illumination of the entire field of view from low magnification to high magnification.
Phase contrast microscope
In the development of optical microscope, the invention of phase contrast microscope is an important achievement of modern microscope technology. We know that the human eye can only distinguish the wavelength (color) and amplitude (brightness) of light waves. For colorless and transparent biological specimens, when the light passes through, the wavelength and amplitude do not change much, and it is difficult to observe the specimen in brightfield observation. Phase contrast microscope uses the difference of the optical path of the object to be inspected for microscopic inspection, that is, it effectively uses the interference phenomenon of light to convert the phase difference that cannot be distinguished by the human eye into a distinguishable amplitude difference, even for colorless and transparent substances. can become clearly visible. This greatly facilitates the observation of living cells, so phase contrast microscopy is widely used for inverted microscopes.
Inverted microscope
The composition of an inverted microscope is the same as that of an ordinary microscope, except that the objective lens and illumination system are inverted. The former is under the stage and the latter is on the stage, which is suitable for microscopic observation of tissue culture, in vitro cell culture, plankton, environmental protection, food inspection, etc. in the fields of biology and medicine. In view of the limitations of the above-mentioned sample characteristics, the objects to be inspected are placed in petri dishes (or culture bottles), and the working distance between the inverted microscope objective and the condenser is required to be long, and the inspection objects in the petri dishes can be directly inspected. observation and research. Therefore, the positions of the objective lens, condenser lens and light source are all reversed, so it is called "inverted microscope". Due to working distance limitations, the maximum magnification of inverted microscope objectives is 60X. Inverted microscopes for general research are equipped with 4X, 10X, 20X, and 40X phase contrast objectives, because inverted microscopes are mostly used for colorless and transparent observation of organisms. If the user has special needs, other accessories can also be selected for complete observation, such as differential interference, fluorescence and simple polarization.
