CURVILINEAR LENS DISTORSION video

Curvilinear distortion is a lens aberration in which the focal length varies radially outward from the center of the field. It has the effect of making a straight tangential line in the object appear curved in the image, either convex outward (so called barrel distortion) or concave outward (pincushion distortion). Straight radial lines remain straight in the image. For example, the direct lines in a grid shown in animation, which are running along the main optical axes of a positive biconvex lens, are displayed as straight lines and other lines are curved outward. Choosing the lenses with opposite sign of curvilinear distortion we can correct this type of aberration.

There are several other types of lens aberration: astigmatism; chromatic aberration; coma; curvature of field; spherical aberration. For example, chromatic aberration arises because of the normal increase in refractive index of all common materials toward the blue end of the spectrum. As a result the focal length of a lens turns out to be wavelength-dependent. The change in image size from one color to another is known as lateral color or chromatic difference of magnification. Because of spherical aberration the wide beams of light will focus in a spot, not point. Astigmatism, coma and curvature of field deteriorate the focusing and sharpness of the image for not axial rays.