The main structure of a metallographic microscope
(1) Mechanical part of metallographic microscope
1. The mirror base is the base of the entire metallographic microscope. Usually horseshoe-shaped or rectangular, it is used to support the stability of the entire scope. Some microscopes are equipped with lighting devices in the lens holder.
2. Mirror column is the upright part above the mirror base, used to connect and support the mirror arm.
3. The mirror arm is the upward curved part of the mirror column. Some microscopes that are held when using the microscope have a movable joint between the mirror arm and the mirror body, called a tilt joint. The mirror can be tilted backward for easier observation.
4. Lens tube is a cylinder connected to the front of the lens arm, generally 160mm in length. Some lens tubes are fixed, and some can move up and down. The upper end of the lens tube is equipped with an eyepiece, and the lower end is connected to the objective lens converter.
5. The adjuster is a large and small screw mounted on the mirror arm or mirror column. When rotated, the lens barrel or stage can be moved up and down to adjust the distance between the objective lens and the specimen, that is, to adjust the focal length. The coarse adjustment screw has a large up and down movement range when rotating, and can quickly adjust the distance between the objective lens and the specimen to bring the object image into the field of view. When the fine-tuning screw rotates, the lifting range is small. Generally, on the basis of coarse adjustment spiral focusing or when using a high-power lens, it is used for more precise adjustment, so as to obtain a completely clear object image, and to observe the structure of different levels and depths of the specimen.
6． The objective converter (rotating disk) is a freely rotatable disk connected to the lower end of the lens barrel. It has 3-4 circular holes. The objective lens is installed in these circular holes. The objective lens of different magnifications can be exchanged by rotating the rotating disk. When the objective lens is turned to the working position (that is, aligned with the optical axis), the notch on the edge of the rotating disk must be engaged with the fixed buckle on the base, otherwise the specimen cannot be observed.
7． Metallurgical microscope stage is a square or circular platform under the lens barrel for placing slide specimens. There is a circular light hole in the center of the platform, and the light from below shines on the specimen through this hole. The specimen slide pusher is installed on the stage. The curved spring clip on the left side is used to fix the specimen slide. Turning the two screws on the right side can move the specimen forward, backward, left and right. Some propellers also have scales that can calculate the distance moved by the specimen and determine the location of the specimen.
(2) Metallurgical microscope lighting part
A lighting device is installed under the stage, which consists of a condenser, an iridescent light detector and a reflector:
1. The reflector is a double-sided mirror with one side flat and the other side concave. It is installed at the base of the mirror base and can rotate in any direction. Its function is to change the direction of the light source and reflect it to the condenser, and then illuminate the specimen through the light hole. The concave surface of the reflector has strong light-gathering power and is suitable for use when the light is weak. When the light is strong, a flat mirror is suitable.
2. The light collector, also known as the light collector, is located on the bracket below the stage and consists of a light collecting mirror and an iridescent aperture. The adjustment screw under the mirror table can be used to control its lifting and lowering to adjust the intensity of the light.
(1) Concentrating mirror A ship is composed of two or three lenses, which function as a convex lens and have the function of concentrating light into bundles to enhance illumination.
(2) The iridescent aperture is located below the condenser, also called the aperture, and consists of more than a dozen metal sheets. A handle extends from its outside. Push this handle to change the size of the aperture to adjust the amount of light. Some microscopes are also equipped with filter glass support frames under the iridescent diaphragm, which can accommodate filter glass glasses of different colors.
(3) Optical part of metallographic microscope
1. Eyepiece, also called eyepiece, is mounted on the upper end of the lens barrel and usually consists of two lenses. There is a diaphragm made of metal between the upper and lower lenses or below the lower lens, which determines the size of the field of view, so it is called the field diaphragm. An eyepiece micrometer can also be installed on the surface of the aperture and human hair can be pasted on the aperture as a pointer to indicate the observation target. A microscope is always equipped with 2-3 eyepieces, which are engraved with symbols such as 5x, 10x, and 15x to indicate their magnification. You can choose to use them. The commonly used eyepiece magnification is 10x.
2. Objective lens, also called objective lens, is installed on the objective lens converter, and there are usually 3-4 of them. The objective lens is a set of lenses strictly composed of several convex lenses and concave lenses. It is a key component for the resolution performance of the microscope. The main performance indicators are usually marked on the objective lens - magnification and lens opening ratio (such as 10/o.25, 40/o.65 and 100/1.25), lens barrel length and required cover glass thickness ( Such as 160/0.17). Depending on the magnification, it is customary to call those below 10 times a low-power lens, 40 times a high-power lens, and 90 or 100 times an oil immersion objective lens called an oil lens. In order to facilitate the distinction, a circle of different colored lines is often used as a special mark on high-power lenses and oil lenses.
The lens aperture ratio (numerical aperture, abbreviated as N.A) can reflect the resolution of the objective lens. The larger the number, the higher the resolution.
The working distance refers to the distance between the surface of the lens below the objective lens and the upper surface of the cover glass when the microscope is in working condition (the object image is adjusted clearly). The greater the magnification of the objective lens, the smaller the working distance
