Basic structure and function of microscope

- Apr 08, 2020-

Optical microscope is a commonly used instrument in the field of biological science and medical research. It is widely used in the teaching and research of cell biology, histology, pathology, microbiology and other related disciplines. It is a powerful tool for studying the tissue and cell structure of human body and other biological bodies. An ordinary optical lens is mainly composed of mechanical system and optical system, while the optical system mainly includes light source, reflector, concentrator, objective lens, eyepiece and other components.

1、 The basic structure and function of optical microscope

1. Mechanical part

Lens barrel: a cylindrical structure installed above the microscope Zui or in front of the lens arm, the upper end of which is equipped with an eyepiece, and the lower end is connected with the objective lens converter.

Objective lens converter: also known as objective lens conversion disk. It is a disc-shaped structure installed under the mirror tube, which can rotate freely in clockwise or counter clockwise direction. There are 3-4 round holes evenly distributed on it, which are used to load objective lenses with different magnification. Rotating the objective conversion disk can make different objectives reach the working position (i.e. the axis of combination with the optical path).

Mirror arm: in order to support the curved structure of the mirror barrel and the mirror platform, it is the part to hold when using the microscope. There is a tilt joint between the mirror arm and the mirror column below the mirror barrel vertical microscope, which can make the mirror barrel tilt backward at a certain angle for convenient observation, but the tilt angle should not exceed 45 degrees when using, otherwise the microscope is easy to overturn due to the center of gravity deviation.

Focusing device: also known as focusing screw. For the device of adjusting focal length, it is divided into coarse adjusting screw (large screw) and fine adjusting screw (small screw). The coarse adjustment screw can make the barrel or the stage rise and fall at a faster speed or a larger range, and can quickly adjust the focal length to make the object image present in the field of vision, which is suitable for the focusing of low power mirror observation. The fine-tuning screw can only slowly or slightly raise or lower the barrel or the stage (the rising or falling distance is not easy to be observed by the naked eye), which is suitable for focusing of high-power mirror and oil mirror or observing different layers of specimen. Generally, the fine-tuning screw is used on the basis of coarse-tuning screw to fine adjust the focal length.

Stage: also known as mirror stage, it is a square platform under the objective lens converter, which is the place to place the observed slide specimen. There is a round hole in the center of the platform, which is called a light hole. The light from the lower part shines on the specimen through this hole.

Mirror column: the short column connecting the mirror arm and the mirror base.

Mirror base: the structure at the bottom of the microscope Zui, which is the base of the whole microscope, used to support and stabilize the mirror body. Some microscopes are equipped with lighting sources and other structures in the mirror base.

2. Optical system part

The optical system of microscope mainly includes objective lens, eyepiece and lighting device (reflector, concentrator and diaphragm, etc.).

Eyepiece: it is installed on the upper end of the lens barrel to further enlarge the object image magnified by the objective lens. Each microscope is usually equipped with 2-3 eyepieces with different magnification. The common eyepieces are 5 ×, 10 × and 15 × (× for magnification), which can be used according to different needs. Zui often uses 10 × eyepieces.

Objective lens: installed on the objective lens converter. Each objective is composed of convex lens and concave lens. It is the main optical component of Zui, which determines the resolution of the lens. The magnifications of common objective lenses are 10 ×, 40 × and 100 × etc. Generally, 8 × or 10 × objective lenses are called low power mirrors (and those below 5 × are called magnifiers); 40 × or 45 × objective lenses are called high power mirrors; 90 × or 100 × objective lenses are called oil mirrors (such lenses need to be immersed in mirror oil when in use).

Concentrator: it is located under the light pass hole of the loading platform and consists of a condenser and an aperture. Its main function is to concentrate light on the specimen to be observed. The condenser consists of two or three lenses, which act as a convex lens and can gather light into a beam. Aperture, also known as rainbow aperture or aperture aperture aperture, is located at the lower end of the concentrator. It is a variable aperture that can control the size of the beam entering the concentrator. It is composed of more than ten pieces of metal flakes, with a small handle on the outside, which can make the aperture of the diaphragm larger or smaller, so as to adjust the intensity of the light.

Reflector: located under the condenser, it can rotate in all directions and reflect light from different directions to the concentrator. There are two sides of the mirror, one is a plane mirror, the other is a concave mirror. The concave mirror has the function of concentrating light and is suitable for use under weak light and scattered light. When the light is strong, the plane mirror is selected (now some new optical microscopes have their own light source, but no reflector; some are equipped with both).