Types of light sources used in optical microscopes and their respective characteristics
【Electron microscope】
Electron microscopes can be divided into transmission electron microscopes, scanning electron microscopes, reflection electron microscopes and emission electron microscopes according to their structure and use. Transmission electron microscopes are often used to observe those fine material structures that cannot be distinguished by ordinary microscopes; scanning electron microscopes are mainly used to observe the morphology of solid surfaces, and can also be combined with X-ray diffractometers or electron energy spectrometers to form electrons. Microprobes for the analysis of material composition; Emission Electron Microscopy for the study of self-emitting electron surfaces.
【Optical microscope】
There are many classification methods for optical microscopes: Zhitai can be divided into trinocular, binocular and monocular microscopes according to the number of eyepieces used; stereoscopic and non-stereoscopic microscopes can be divided according to whether the image has a three-dimensional sense; according to the observation object can be divided into According to the optical principle, it can be divided into polarized light, phase contrast and differential interference contrast microscope, etc.; according to the type of light source, it can be divided into ordinary light, fluorescence, infrared light and laser microscope, etc.; according to the type of receiver, it can be divided into Visual, photographic and television microscopes, etc. Commonly used microscopes include binocular continuous zoom stereo microscope, metallographic microscope, polarized light microscope, ultraviolet fluorescence microscope, etc.
The binocular stereo microscope uses a dual-channel optical path to provide 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 tubes constitute a viewing angle that is equivalent to the viewing angle formed when people observe an object with both eyes, thereby forming a three-dimensional visual image in three-dimensional space. Binocular stereo microscopes are widely used in slicing operations and microsurgery in the fields of biology and medicine; in industry, they are used for observation, assembly, and inspection of tiny parts and integrated circuits.
A metallographic microscope is a microscope specially used 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 metallography and ordinary microscopes is that the former uses reflected light, while the latter uses transmitted light to illuminate. In the metallographic microscope, the illumination beam is emitted from the direction of the objective lens to the surface of the observed object, reflected by the object surface, 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.
Ultraviolet fluorescence microscopy is a microscope that uses ultraviolet light to excite fluorescence for observation. Some specimens cannot detect structural details in visible light, but after dyeing, they can emit visible light due to fluorescence when irradiated with ultraviolet light, forming a visible image. Such microscopes are commonly used in biology and medicine.
Television microscopes and charge-coupled device microscopes are microscopes with a television camera target or a charge-coupled device as the receiving element. A television camera target or a charge-coupled device is installed at the real image surface of the microscope to replace the human eye as a receiver, and these optoelectronic devices are used to convert the optical image into an image of an electrical signal, and then perform size detection, particle counting and other work. This type of microscope can be used in conjunction with a computer, which facilitates the automation of detection and information processing, and is mostly used in occasions that require a lot of tedious detection work.
A scanning microscope is a microscope in which the imaging beam can perform scanning motion relative to the object surface. In the scanning microscope, the highest resolution of the objective lens is ensured by reducing the field of view. At the same time, the imaging beam is scanned in a larger field of view relative to the object surface by means of optical or mechanical scanning, and information processing technology is used to obtain a composite large-scale image information. This type of microscope is suitable for observations requiring high-resolution, large-field images. Coarse focus screw: move the lens barrel up and down in a wide range.
