1. In a scanned image system, electrical compensation for the distortion introduced by the limiting size of a scanning aperture. 2. In television technology, restoration of the depth of modulation to the higher (i.e., higher Fourier) frequency components of the video signal, with the objective of achieving a subjective improvement in image quality. Note: Aperture correction is required to compensate for the properties of the camera lens, optical beam-splitting installation, and camera tube, all of which contribute to a reduced signal at higher spatial frequencies. Problems requiring aperture correction arise in a scanning system when the frequency response falls off as the effective wavelength of the detail to be resolved in the image approaches the dimension of the scanning aperture and becomes zero when that effective wavelength equals the dimension of the scanning aperture.