Eyepieces and Objectives for Metallurgical Microscopes
The diameter of the magnified real image of the old-fashioned objective lens is only 18 mm~20 mm, and the plan achromatic objective lens delineates: the diameter of the highly corrected magnified real image is 28 mm. That is, the area of the image field has doubled, and the curvature of the image field has been well corrected.
Now there are 100x, 150x, 200x, and even 250x dry objective lenses. Using this dry objective lens can easily make the total magnification far exceed the traditionally specified 1100 na, which further proves the above point.
In order to prevent the objective lens from being damaged due to accidentally touching the sample or being heated during work, a long working distance objective lens is designed, so that the distance between the front lens of the lens and the sample is increased by about 10 times compared with the conventional lens. Although the numerical aperture of the lens is different Decreased, but image quality is still good.
The na value of the traditional high-magnification (100x) oil-immersion objective lens can reach 1.4, but the oil on the front lens of the objective lens and the sample must be wiped clean after use. Nowadays, this lens has been listed as an optional item, and the standard setting is changed. It is a high-magnification dry objective lens, and its na value is between 0.90 and 0.95. Although there is a lot of reduction, it is convenient for operation.
The diameter of the field diaphragm of the old-fashioned eyepiece is only 16 mm, and the diameter of the field diaphragm of the new microscope wide-field eyepiece is normally 22 mm, and can reach as large as 26.5 mm. Make full use of the expanded image field area of the plan objective lens.
Using the optical system different from the ordinary objective lens, transparent and easily reflective objects can be clearly displayed under this objective lens. There are two optical path channels outside the objective lens. Inner ring and outer ring light path. The principle of the inner ring light path is the same as that of ordinary objective lens, which is called bright field. The outer ring light path uses multiple groups of prisms to make the light path enter the line of sight through the outer ring. The line of sight of the observed object is just surrounded by the outer ring light, which is called dark field. However, the bright and dark field objective lens is used less in industry, and the cost is much higher than that of ordinary objective lens.
When observing microscopic structures, the distance between the eye and the eyepiece lens. Old-fashioned eyepieces are defined as ≯10 mm. If you do not take off the glasses for observation, the field of view will be affected. For high-eyepoint eyepieces, this distance can be increased to ≯20 mm, so that people who wear diopter glasses do not need to take off the glasses for observation, and the image quality is not affected by eye defects.
