What are the common aberrations of machine vision lenses?

Aberration is an important factor affecting image quality. The image quality of different machine vision lenses is also different. Even if the same type of industrial lens is used, the quality of the image obtained is due to the relationship between processing precision, lens structure and material. Has changed. Because of this, the price of industrial lenses also has a gap between one hundred yuan and ten thousand yuan. When we select industrial lenses, the first thing we must consider is aberration, which is an important factor affecting image quality. Common machine vision lens aberrations include the following six types: 1. Ball difference The monochromatic conical beam emitted from an object point on the main axis to the optical system, after being refracted by the optical series, if the original light beams with different aperture angles cannot be crossed at the same position on the main axis, and even the ideal image on the main axis At the plane, a diffuse light spot (commonly known as a fuzzy circle) is formed, and the imaging error of this optical system is called spherical aberration. 2. coma The monochromatic conical beam emitted from an off-axis object point located outside the main axis toward the optical system, after being refracted by the optical series, cannot form a clear point at the ideal image plane, but forms a bright tail. Coma spot, the imaging error of this optical system is called coma. 3. Astigmatism The oblique monochromatic conical beam emitted from an off-axis object point located outside the main axis towards the optical system, after being refracted by the optical series, cannot form a clear image point, but can only form a diffuse spot. The imaging error of the optical system is called astigmatism. 4. Field song A clear image formed by a plane object perpendicular to the main axis through the optical system, if it is not in an image plane perpendicular to the main axis, but on a curved surface symmetrical about the main axis, that is, the best image plane is a curved surface. The imaging error of the optical system is called curvature of field. When the image at the center of the screen is focused to be clear, the images around the screen are blurred; and when the image at the center of the screen is focused to become clear, the images at the center of the screen begin to blur again. 5. Distortion The straight line outside the main axis in the plane of the object becomes a curve after being imaged by the optical system, and the imaging error of this optical system is called distortion. Distortion aberration only affects the geometric shape of the image, not the sharpness of the image. This is the fundamental difference between distortion and spherical aberration, coma, astigmatism, and curvature of field. 6. Chromatic aberration A white light is emitted from a white object to the optical system. After being refracted by the optical system, the light of each color cannot converge on one point, and a colored image spot is formed, which is called chromatic aberration. The cause of chromatic aberration is that the same optical glass has different refractive indexes for light of different wavelengths, the refractive index of short-wave light is large, and the refractive index of long-wave light is small.