Index of physics articles (A)

Aberration in optics refers to imperfections in the image formed by an optical system, such as a lens or mirror. These imperfections cause a blurring or distortion of the image, preventing it from being perfectly sharp and clear. Aberrations arise from the limitations of real optical elements and their inability to perfectly focus all light rays from a single point onto a single point on the image plane. Different types of aberrations exist, each with its own characteristic effect on the image quality.

Several factors contribute to optical aberrations. These include:

• Monochromatic Aberrations: These aberrations occur even when using light of a single wavelength. They include:

  • Spherical Aberration: Rays passing through the outer zones of a lens or mirror focus at a different point than rays passing through the center, resulting in a blurred image.
  • Coma: Off-axis points appear as comet-shaped blobs rather than sharp points. This is due to different magnification for rays passing through different zones of the lens.
  • Astigmatism: A point off-axis is imaged as two short lines at different focal lengths, one tangential and one sagittal. This results in a blurred, smeared appearance.
  • Field Curvature: The image plane is not flat, but curved. This means that only a portion of the image is in sharp focus at any given time.
  • Distortion: The magnification varies across the field of view, causing straight lines to appear curved in the image. This can be either barrel distortion (lines curving inwards) or pincushion distortion (lines curving outwards).

• Chromatic Aberrations: These aberrations arise from the fact that different wavelengths of light are refracted differently by the lens material. This leads to a color fringing effect around the image. The two main types are:

  • Axial Chromatic Aberration (Longitudinal Chromatic Aberration): Different colors of light focus at different distances along the optical axis.
  • Lateral Chromatic Aberration (Transverse Chromatic Aberration): Different colors of light are magnified differently, resulting in colored fringes around the edges of objects.

Optical designers employ various techniques to minimize or correct these aberrations. These include using multiple lenses with different properties, aspherical lens surfaces, and specialized lens coatings. The level of aberration correction required depends on the specific application and the desired image quality. High-precision optical systems, such as those used in telescopes and microscopes, require very careful aberration correction to achieve optimal performance.