Gabriel Fielding

Aliasing and Reconstruction Distortion in Digital Intermediates

This paper addresses two types of artifacts associated with the image sampling and reconstruction process, namely, aliasing and reconstruction distortion. Aliasing is an artifact that results from sampling a continuous signal at too low of a spatial rate relative to the input frequency content. Shannons sampling theorem states that discrete sampling of a signal at a uniform rate higher than twice the highest frequency in the signal, called the Nyquist rate, will allow a perfect reconstruction of the original continuous signal. However, image displays do not reconstruct images according to the ideal reconstruction equation, and, in many cases, the display uses nothing more than a sample-and-hold reconstruction. It has long been known that nonideal reconstruction can lead to distortion of the image data at frequencies below the Nyquist rate. Proper recognition of the distinction between aliasing and reconstruction errors can mean the difference between accepting and avoiding artifacts.