In geometric optics, distortion is a deviation from rectilinear projection; a projection in which straight lines in a scene remain straight in an image. It is a form of optical aberration.
In pincushion distortion, corners of squares form elongated points, as in a cushion.
With uncorrected barrel distortion (at 26mm)
Barrel distortion corrected with software (this is the ENIAC computer)
In optics, aberration is a property of optical systems, such as lenses, that causes light to be spread out over some region of space rather than focused to a point. Aberrations cause the image formed by a lens to be blurred or distorted, with the nature of the distortion depending on the type of aberration. Aberration can be defined as a departure of the performance of an optical system from the predictions of paraxial optics. In an imaging system, it occurs when light from one point of an object does not converge into a single point after transmission through the system. Aberrations occur because the simple paraxial theory is not a completely accurate model of the effect of an optical system on light, rather than due to flaws in the optical elements.
Image plane of a flat-top beam under the effect of the first 21 Zernike polynomials.
Effect of Zernike aberrations in Log scale. The intensity minima are visible.
Laser guide stars assist in the elimination of atmospheric distortion.
