Eyepiece and objective of metallographic microscope
The diameter of the enlarged real image in the old style objective is only 18 mm~20 mm, while the diameter of the enlarged real image in the flat field achromatic objective is defined as 28 mm after height correction. The area of the image field has doubled and the curvature of the image field has been well corrected
At the beginning, there were already 100x, 150x, 200x, and even 250x dry objective lenses. By using this type of dry objective lens, the total magnification can easily exceed the traditional limit of 1100 nm, further confirming the aforementioned viewpoint
In order to prevent damage to the objective lens due to accidental contact with the sample or heating during operation, a long working interval objective lens is designed, which increases the gap between the front lens and the sample by more than 10 times compared to conventional lenses. Although the numerical aperture of the lens has been reduced, the imaging quality is still good
The traditional high-power (100x) oil immersed objective has a na value of up to 1.4. However, after use, the front lens of the objective and the oil on the sample must be wiped clean. Nowadays, this type of lens has been listed as an optional part, and the standard setting has been changed to a high-power dry objective, with a na value between 0.90 and 0.95. Although there is a significant reduction, it is convenient to operate
The field aperture diameter of the old eyepiece is only 16 mm, while the field aperture diameter of the new microscope wide field eyepiece is normally 22 mm and can reach up to 26.5 mm. Fully utilized the image field area expanded by the flat field objective.
By utilizing an optical system that differs from ordinary objective lenses, transparent and easily reflective objects can be clearly displayed under this type of objective lens. There are two optical channels on the outside of the objective lens. Inner and outer ring optical paths. The principle of the inner ring light path is similar to that of a regular objective lens, known as the bright field. The outer ring light path uses multiple sets of prisms to allow the light path to enter the line of sight through the outer ring. The observed object's line of sight is also precisely surrounded by the outer ring light, known as the dark field. However, the use of light and dark field objective lenses is limited in industrial applications, and their cost is significantly higher than that of ordinary objective lenses.
The distance between the eye and the eyepiece lens when observing microscopic structures. The old-fashioned eyepiece is defined as ≤ 10 mm, and if the glasses are not removed for observation, the field of view will be affected. For high eye point eyepieces, this interval can be increased to not more than 20 mm, so that those wearing refractive glasses do not need to remove their glasses for observation, and the moral character of the object is not affected by eye defects.
