The most complete classification of microscopes

Optical microscope can be divided into binocular and monocular microscope according to the number of eyepieces used; stereovision and non stereoscopic vision microscope according to the stereoscopic sense of image; biological and metallographic microscope according to observation object; polarized light, phase contrast and differential interference contrast microscope according to optical principle; ordinary light and fluorescence according to light source type According to the receiver type, it can be divided into visual microscope, digital (camera) microscope, etc. The commonly used microscopes include comparison microscope, binocular stereomicroscope, metallographic microscope, polarizing microscope, fluorescence microscope, etc.

1. Comparison microscope

The comparison microscope is a new kind of microscope which uses a set of eyepieces to observe the left and right field of view at the same time, and uses the method of field cutting, docking and overlapping to compare two (or more) objects. It is an ideal instrument for public security, procuratorial, court and colleges to compare and detect bullets, tool marks, fingerprints, seals, characters, patterns, money, etc. it is also suitable for electronic, biochemical, agricultural, archaeological, banking, customs and other needs for comparative detection of objects Identified industries and sectors.

2. Binocular stereomicroscope

Binocular stereomicroscope, also known as "solid microscope" or "anatomical microscope", is a kind of stereoscopic vision instrument with positive image. It is widely used in biological and medical fields for slicing operation and microsurgery, and for observation, assembly and inspection of micro parts and integrated circuits in industry. It uses a dual channel light path, and the left and right beams in the binocular lens tube are not parallel, but have a certain angle body angle (generally 12 degrees to 15 degrees), providing a stereoscopic image for the left and right eyes. In essence, two single tube microscopes are placed side by side. The optical axis of the two tubes is equivalent to the angle of view formed when people use binocular to observe an object, so as to form a three-dimensional stereo vision image.

At present, the optical structure of the body mirror is: a common primary objective lens. After imaging the object, the two beams are separated by two groups of intermediate objective lens, namely zoom lens, and the viewing angle is formed by the respective eyepiece. Its magnification change is obtained by changing the distance between the intermediate lens groups, so it is also called "zoom stereomicroscope". With the requirement of application, there are many optional accessories for stereoscope, such as fluorescence, photography, photography, cold light source and so on.

3. Metallographic microscope

Metallographic microscope is a kind of microscope used to observe the metallographic structure of opaque objects such as metals and minerals. These opaque objects can not be observed in ordinary transmission light microscope, so the main difference between metallographic microscope and ordinary microscope is that the former uses reflected light, while the latter uses transmission light for illumination. In the metallographic microscope, the illumination beam shoots from the objective direction to the observed object surface, and then returns to the objective lens for imaging after being reflected by the object surface. This kind of reflective illumination is also widely used in the detection of integrated circuit wafers.

4. Polarizing microscope

Polarizing microscope is a kind of microscope used to study the so-called transparent and opaque anisotropic materials. All materials with birefringence can be distinguished clearly under a polarizing microscope. Of course, these substances can also be observed by dyeing method, but some of them are impossible, and the polarizing microscope must be used. The method of changing ordinary light into polarized light for microscopic examination to identify whether a substance is single refraction (isotropic) or birefringence (anisotropic). Birefringence is the basic characteristic of crystal. Therefore, polarizing microscope is widely used in the fields of minerals, chemistry, biology and botany.

5. Fluorescence microscope

Fluorescence microscope is to irradiate the detected object stained with fluorescein with short wavelength light, and then generate fluorescence of growth wavelength after being excited, and then observe. Fluorescence microscope is widely used in biology, medicine and other fields.

Fluorescence microscope is generally divided into two types: transmission type and falling type. Transmission type: the excitation light comes from the lower part of the inspected object, and the condenser is a dark field condenser, so that the excitation light does not enter the objective lens, but the fluorescence enters the objective lens. It is bright at low power, but dark at high power. It is difficult to operate when it is immersed in oil and adjusted in the middle. It is difficult to determine the illumination range at low power, but it can get a very dark background. Transmission type is not used for non transparent objects. Falling beam type: transmission type is almost eliminated at present. Most of the new fluorescent microscopes are of the falling type. The light source comes from the top of the tested object, and has a spectroscope in the light path, so it is applicable to both transparent and opaque objects. Because the objective lens acts as a condenser lens, it is not only easy to operate, but also can realize uniform illumination of the whole field of view from low power to high power.

At present, many emerging biological research fields have been applied to fluorescence microscopy, such as gene in situ hybridization (FISH) and so on.

6. Phase contrast microscope

In the development of optical microscope, 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 light waves. For colorless and transparent biological specimens, when the light passes through, the wavelength and amplitude change little, so it is difficult to observe the specimen in the bright field. Phase contrast microscope uses the optical path difference of the object to be examined, that is to effectively use the interference phenomenon of light to change the phase difference that can not be resolved into the amplitude difference that can be resolved. Even the colorless and transparent material can be clearly visible. Therefore, phase contrast microscopy is widely used in inverted microscope.

7. Differential interference contrast microscope

Differential interference contrast microscopy appeared in the 1960s. It can not only observe the colorless and transparent objects, but also has the stereoscopic effect of relief. It has some advantages that phase contrast microscopy can not achieve, and the observation effect is more realistic. Differential interference contrast microscopy uses a special Wollaston prism to decompose the light beam. The vibration directions of the split beams are perpendicular to each other and the intensity is equal. The beams pass through the object at two points close to each other, and there is a slight difference in phase. Because the split distance between the two beams is very small and there is no ghost phenomenon, the image presents a three-dimensional sense.

8. Inverted microscope

Inverted microscope is used to observe tissue culture, cell culture in vitro, plankton, environmental protection, food inspection and other fields in biology and medicine.

Due to the limitations of the above sample characteristics, the tested objects are placed in the culture dish (or culture bottle), which requires a long working distance between the objective lens and the condenser of the inverted microscope, so that the microscopic observation and research can be carried out directly on the tested objects in the culture dish. Therefore, the position of objective lens, condenser and light source is reversed, so it is called "inverted microscope".

Due to the limitation of working distance, the maximum magnification of inverted microscope objective is 60x. Generally, inverted microscope is equipped with 4x, 10x, 20x and 40x phase contrast objective lens, because the inverted microscope is mostly used for colorless and transparent in vivo observation. If the user has special needs, other accessories can be selected to complete differential interference, fluorescence and simple polarization observation.

Visual inverted microscope is widely used in patch clamp, transgene ICSI and other fields.

9. Digital microscope

Digital microscope is a kind of microscope with camera (i.e. TV camera target or charge coupler) as receiving element. A camera is installed on the real image surface of the microscope instead of the human eye as the receiver. The optical image is converted into the image of electrical signal by this photoelectric device, and then the size detection and particle counting are carried out. This kind of microscope can be combined with computer, which is convenient to realize the automation of detection and information processing. It is often used in the situation where a lot of tedious work is needed.

At present, there is a portable digital microscope camera, referred to as digital micro camera. It combines microscope and digital camera to meet the requirements of micro preview and micro photography at the same time. The highest microscope magnification of the objective lens can reach 150x. The body is compact and easy to carry. It has its own light source and can be used in many occasions. It can be directly connected with computer, printer (without computer), TV (without computer).