What are the different types of illumination for metallurgical microscopes?
Illumination of metallurgical microscopes
The light path of metallographic microscope has a special illumination system. Most of its illumination light source is installed in the side of the mirror body or the rear of the lower, in order to achieve the purpose of the light can be ingested into the objective lens and then ingested into the eyepiece, it is necessary to install a reflector in the intersection of the two optical axes (plane mirrors or prisms) so that the light is vertically steered, if the light source is designed to be at the bottom of metallurgical microscope, the illumination beam is directly shot to the surface of metallurgical specimens through the objective lens, the surface of the specimen is reflected back to the objective lens and the image, and * and then the reflector for vertical steering. Reflector for vertical steering, because of its role in vertical illumination, it is called "vertical illuminator".
Metallographic microscope is the use of different forms of mirrors to make the beam (or elephant) steering, illumination mode has a bright field and dark field illumination of two kinds.
1,Bright field illumination
Bright field illumination is a kind of illumination commonly used in metallographic microscope, which relies on the vertical illuminator to emit the light from the light source to the objective lens, and then the objective lens will be perpendicular or nearly perpendicular light, irradiated in the metallographic specimen on the grinding surface. Then the light reflected from the specimen grinding surface and vertically through the objective lens to give amplification, then by the eyepiece to be the second magnification. In general metallographic microscope, often choose 45 degrees tilted plane glass and total reflection prism as a vertical illuminator. Large horizontal metallurgical microscope, its bright field illumination system, most have these two kinds of illumination device, it depends on the change of the handle back and forth or left and right to achieve. Plane glass and fully reflective prisms as a vertical illuminator, although both can reflect and transmit light.
2, dark field of view lighting
The difference between the dark field of view and the bright field of view is mainly the distribution of light and lighting effects. Parallel light from the light source is blocked by the ring light bar, the centre of the light can not be passed, the formation of a hollow ring beam into the vertical illuminator, so that the light through the periphery of the objective lens transmits in the special reflective condenser mirror, by which the light will be reflected in the metallurgical specimen on the grinding surface, because of its reflection over the light tilt angle is very large, if the specimen is a polished mirror, so that the light on the specimen is still at a great inclination in the opposite direction Reflection, it is impossible to enter the objective lens, so the field of view is a dark colour, only the specimen of the depression of the light emission into the objective lens, so in the dark field of the microscope to observe the specimen and the bright field of view under the exact opposite.
