Inelectronics, distortions are signal distortions caused by passive and active circuits and components. A distinction is made between linear and non-linear distortions. In projection technology, there are a wide variety of optical distortions caused by geometric imaging errors.
Signal distortions caused by electronic components
Linear distortions are those in which the signal shape is not changed, but the signal merely becomes larger or smaller. Such linear distortions are due to frequency-dependent attenuation or gain. They can be reversed by level or frequency enhancements. A well-known method for this is emphasis with pre-emphasis and de-emphasis.
In contrast to linear distortions, nonlinear distortions generate additional unwanted signal components, for example harmonics, phase shifts, group delays, which result from nonlinear characteristics. The nonlinear distorted waveform is not identical to the original signal, nor can it be reproduced into the original waveform. In acoustics, these distortions are expressed in the distortion factor. Distortions are uniquely determined by the distortion factor, the ratio of harmonic signal frequencies to the total signal.
Image distortion in projection technology
In projection technology, geometric image distortions occur when the projection axis is not centered and perpendicular to the center of the projection surface. If the projection axis is aligned perpendicularly but not centrally, black edges will occur. These depend on whether the projection axis is too far to the right, left, top or bottom. If the projection axis is not aligned vertically, then trapezoidal distortions occur.
Other projection distortions are barrel and pincushion distortions. These are caused by changes in scale that depend on the distance of the image point from the projection axis. The projected images become smaller or larger towards the corners and resemble the shape of a barrel or a cushion.