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Common term definitions for microscopes
Do you know the names of the microscope explain?
1. Refraction and Refractive Index: Light is transmitted in a uniform isotropic medium with a straight line between two points. When passing through a transparent object of different density medium, refraction occurs due to the propagation speed of light in different media. Caused by the difference. When light that is not perpendicular to the transparent object is incident on a transparent object (such as glass) by air, the light changes direction at its interface and forms a refraction angle with the normal.
2. Chromatic aberration: Chromatic aberration is a serious defect in lens imaging. In the case where polychromatic light is a light source, monochromatic light does not produce chromatic aberration. White light consists of seven kinds of red orange, yellow, green, blue, and purple. The wavelengths of various light are different, so the refractive index is different when passing through the lens. Thus, one point on the object side may form a color spot on the image side.
3. Ball  difference : The spherical aberration is the monochromatic phase difference of the points on the axis, which is caused by the spherical surface of the lens. The result of the spherical aberration is that after a point is imaged, it is not a bright spot, but a bright spot whose middle bright edge is gradually blurred. Thereby affecting the image quality.
4. Astigmatism: Astigmatism is also a single-phase difference in the off-axis point that affects sharpness. When the field of view is large, the object point on the edge is far from the optical axis, and the beam is tilted greatly, causing astigmatism after passing through the lens. The astigmatism causes the original object to become two separate and perpendicular short lines after imaging, which are combined on the ideal image plane to form an elliptical spot. Astigmatism is eliminated by a complex combination of lenses.
5. Universal Infinity Correction Optical System: It is the most advanced optical path design at present, which reflects the superiority of infinity correction mode. After passing through the objective lens, the light passes through the lens barrel and refracts at the image lens or completes the intermediate image without phase difference. An optical attachment can be added between the objective lens and the lens of the observation cylinder without affecting the total magnification. In addition, this optical system does not require the installation of an additional correction lens to achieve an optimal microscopic image.
6. Numerical aperture: The numerical aperture is abbreviated as NA. The numerical aperture is the main technical parameter of the objective lens and the condensing mirror. It is an important indicator for judging the performance of both (especially for the objective lens). The values ​​of the values ​​are respectively on the outer casing of the objective lens and the condenser. As the NA value increases, the field of view width and working distance will decrease accordingly.
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7. Resolution : Also known as discrimination rate resolution. It is another important technical parameter to measure the performance of the microscope. It is determined by two factors: the NA value of the objective lens and the wavelength of the illumination source. The larger the NA value, the shorter the wavelength of the illumination light, and the smaller the d value, the higher the resolution.
8. Magnification: Magnification is the magnification. It refers to the ratio of the size of the final image seen by the human eye to the size of the original object after being magnified by the objective lens and enlarged by the eyepiece. It is the magnification of the objective lens and the eyepiece. product.
9. Working distance: The working distance is also called the object distance, which refers to the distance between the surface of the front lens of the objective lens and the object to be inspected. At the time of microscopy, the object to be inspected should be between one and two focal lengths of the objective lens. Therefore, it and the focal length are two concepts. The usual focus is to adjust the working distance. In the case where the numerical aperture of the objective lens is constant, the working distance is short and the aperture angle is large. A high magnification objective lens with a large numerical aperture has a small working distance.
10. Condenser: Condenser, also known as concentrator, is mounted below the stage. Small microscopes often have no concentrating mirrors, and when using an objective lens with a numerical aperture of 0.40 or more, it is necessary to have a condensing mirror. The condensing mirror not only compensates for the lack of light and appropriately changes the properties of the light emitted from the light source, but also focuses the light on the object to be inspected for the best illumination. There are many kinds of structures of the condensing mirror, and according to the numerical aperture of the objective lens, the requirements for the condensing mirror are different accordingly.
11. Abbe concentrator: This is by Master Ernst of the German Optical University. Abbe design. Abbe condenser is composed of two lenses, which has better concentrating ability, but when the numerical aperture of the objective lens is higher than 0.60, the chromatic aberration and spherical aberration are displayed. Therefore, it is mostly used on ordinary microscopes.
12. Transmissive illumination : sub-center illumination and oblique illumination:
A. Center lighting : It is divided into: Critical lighting: and Kohler lighting.
a. Critical lighting : This is a common lighting method. This kind of illumination is characterized in that the light source is imaged on the object to be inspected after being condensed, and the beam is narrow and strong, which is its advantage.
b. Kohler illumination: Kohler illumination overcomes the shortcomings of critical illumination and is the ideal illumination method for research microscopes. This illumination method not only has good observation effect, but also is an illumination method necessary for successful photomicrography.
B. Oblique illumination : The central axis of the illumination beam is not in line with the optical axis of the microscope, but is obliquely illuminated on the object at an angle to the optical axis, thus being obliquely illuminated. Phase contrast microscopy and dark field microscopy are oblique illumination.
13. Epi-illumination : The beam of such illumination comes from above the object through the objective lens and then onto the object to be inspected, so that the objective lens acts as a condenser. This method of illumination is suitable for non-transparent objects such as metals, minerals and the like.