aberration

The term aberration is used for compact discs(CD), DVDs and for lenses of cameras and projectors and describes the defocusing of the laser beam or the aberration of lenses. Imaging errors are deviations from the ideal optical image.

1. In the case of DVDs and compact discs (CD), defocusing of the scanning beam can cause imaging errors when reading optical storage media. The defocusing can be caused by the lens system or by the composition of the substrate.
2. In digital photography, image blur is referred to as chromatic aberration( CA), spherical aberration and image field curvature. This occurs particularly with wide-angle lenses and telephoto lenses. Lenses are subject to chromatic dispersion and refract the different wavelengths differently. As a result, the different colors of the image are not projected exactly on top of each other on the CMOS sensor and the image has a slight blur in the colors. These errors show up as violet and greenish color fringes at light-dark transitions. These blurs can be compensated for with special low-dispersion lenses or by stopping down. Such lenses are called ED lenses, which stands for Extra-Low Dispersion. They are shaped so that the wavelengths of different colors are refracted to the same extent and are concentrated at the focal point.