What are the factors that affect the resolution of a microscope
1. Color difference
Color difference is a serious defect in lens imaging, which occurs when polychromatic light is used as the light source, and monochromatic light does not produce color difference. White light is composed of seven types: red, orange, yellow, green, blue, blue, and purple. Each type of light has different wavelengths, so its refractive index when passing through a lens is also different. This way, a point in the object may form a color spot in the image.
Color difference generally includes positional color difference and magnification color difference. The positional color difference causes the image to have color spots or halos when observed at any position, making the image blurry. And the magnification chromatic aberration causes the image to have colored edges.
2. Spherical aberration
Spherical aberration is the monochromatic aberration of points on the axis, caused by the spherical surface of the lens. The result of spherical aberration is that after a point is imaged, it is no longer a bright spot, but a bright spot with a bright center and gradually blurred edges. This affects the imaging quality.
The correction of spherical aberration often uses lens combinations to eliminate it. As the spherical aberration of convex and concave lenses is opposite, different materials of convex and concave lenses can be selected to be glued together to eliminate it. The spherical aberration of the objective lens in the old model microscope was not completely corrected, and it should be matched with the corresponding compensating eyepiece to achieve the correction effect. The spherical aberration of general new microscopes is completely eliminated by the objective lens.
3. Wisdom difference
Hui difference belongs to the monochromatic difference of off axis points. When an off-axis object is imaged with a large aperture beam, the emitted beam passes through the lens and no longer intersects at a point. The image of a light point will be in the shape of a comma, resembling a comet, hence the term "coma".
4. Astigmatism
Astigmatism is also an off axis monochromatic difference that affects clarity. When the field of view is large, the object points on the edge are far from the optical axis, and the beam tilts greatly, causing astigmatism after passing through the lens. Astigmatism causes the original object point 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 through complex lens combinations.
5. Field music
Field bending, also known as "field bending". When there is field curvature in the lens, the intersection point of the entire beam does not coincide with the ideal image point. Although clear image points can be obtained at each specific point, the entire image plane is a curved surface. This makes it difficult to see the entire surface clearly during microscopic examination, resulting in difficulties in observation and photography. Therefore, the objective lenses used for studying microscopes are generally flat field objectives, which have already corrected the field curvature.
6. Distortion
The various differences mentioned earlier, except for the field curve, all affect the clarity of the image. Distortion is another property of phase difference, where the concentricity of the beam is not disrupted. Therefore, it does not affect the clarity of the image, but causes distortion in shape compared to the original object.
(1) When the object is located outside the focal length of the lens, a reduced inverted real image is formed within the focal length of the image and outside the focal point;
(2) When the object is located at twice the focal length of the lens, an inverted real image of the same size is formed at twice the focal length of the image;
(3) When the object is located within twice the focal length of the lens and outside the focal point, an enlarged inverted real image is formed outside the focal length of the image;
(4) When the object is located at the focal point of the lens, the image cannot be imaged;
(5) When the object is located within the focal point of the lens object, there is no image formation in the image side, and an enlarged upright virtual image is formed on the same side of the lens object side that is further away from the object.
