The basic structure and function of the microscope

The optical microscope is a commonly used instrument in biological science and medical research. It is widely used in the teaching and research of cell biology, histology, pathology, microbiology, and other related subjects. It is a powerful tool to study the tissue and cell structure of the human body and other organisms.  An ordinary light mirror is mainly composed of the mechanical system and optical system, and the optical system mainly includes the light source, reflector, concentrator, objective, and eyepiece.  

Have you learned about your microscope?  If not, follow me through this guide to the basic structure and function of a microscope.  

To observe objects with a microscope

Basic structure and function of optical microscope  

(1) Mechanical part  

Lens tube: A cylindrical structure mounted at the top of the microscope or in front of the lens arm, with an eyepiece at the top and an objective converter at the bottom.  

Objective converter: also known as objective converter plate.  It is a disk-like structure mounted under the tube and can be freely rotated clockwise or counterclockwise.  There are 3 ~ 4 round holes evenly distributed on it for loading objective lenses with different magnifications.  By turning the objective plate, the different objective lenses can reach the working position (i.e., align with the axis of the optical path).  

Arm: A curved structure that supports the tube and table and is used to hold the microscope.  The vertical microscope has an oblique joint between the arm and the column below so that the tube can be tilted back by a certain Angle for easy observation. However, the tilt angle should not exceed 45 degrees when used, otherwise, the microscope will easily tip over due to the deviation of the center of gravity.  

Focusing device: also known as focusing screw, for adjusting the focal length of the device, divided into two kinds of the coarse adjusting screw (large screw) and fine adjusting screw (small screw).  The coarse adjusting screw can make the lens tube or object platform with a faster speed or a larger rise and fall can quickly adjust the focal length of the object image in the field of vision, suitable for low-power lens observation of the focus. 

The fine screw can only make the tube or the loading platform slowly or a small range of ups and downs (up or down the distance is not easy to be observed by the naked eye), suitable for high power lens and oil lens focus or observe different levels of specimens, generally in the coarse screw focusing based on the use of fine focusing screw, fine focal length adjustment.  

The loading table: also known as the mirror table, is located in the objective converter below the square platform and is the place to place the glass specimens under observation.  There is a circular hole in the center of the platform, called the light hole, through which light from below hits the specimen.  

Mirror column: the short column where the mirror arm is connected to the mirror base.  

Pedestal: The structure at the bottom of a microscope that forms the base for the entire microscope and supports and stabilizes the lens.  Some microscopes are equipped with lighting sources and other structures in the lens holder.  


(2) Optical system  

The optical system of a microscope mainly includes an objective lens, eyepiece, and illumination device (reflector, concentrator, aperture, etc.).  

Eyepiece: installed on the upper end of the lens tube, it plays the role of further magnifying the object image magnified by the objective lens.  Each microscope is usually equipped with 2 to 3 eyepieces of different magnification. Common eyepieces are 5 x, 10 x and 15 x (x indicates magnification). Eyepieces can be used according to different needs, and the 10 x eyepiece is most commonly used.  

Objective lens: Mounted on the objective lens converter.  Each light mirror generally has 3 ~ 4 different magnification objective lenses, each objective lens is composed of several convex and concave lenses, which is the most important optical component of the microscope and determines the resolution of the light mirror.  The magnification of the common objective lens is 10×, 40×, and 100×.  Generally, an 8× or 10× objective lens is called a low power lens;  40× or 45× is called high magnification;  Call 90× or 100× oil mirror.  

Concentrator: located at the bottom of the light hole of the object platform, composed of condenser and aperture, its main function is to focus the light on the specimen to be observed.  A condenser is a combination of two or three lenses that act as a convex lens to concentrate light into a beam. 

An aperture, also known as a rainbow stop or aperture stop, located at the lower end of the condenser, is a variable stop that controls the size of the light beam entering the condenser.  It is arranged by a combination of more than 10 pieces of metal sheet and become, its outside side has a small handle, the aperture that can make aperture opens big or narrow, to adjust the intensity of the light.  

Reflector: located below the condenser, can rotate in all directions, can reflect light from different directions into the condenser.  The reflector has two sides, one is a plane mirror, and the other is a concave mirror, the concave mirror has the effect of concentrating light, suitable for the use of weak light and scattered light, when the light is strong, the plane mirror is selected.  

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