Abstract
The halftone screen with fine vertical gratings is often used to modulate images in the printing technology. When the halftone screen is disturbed by the jitter in horizontal direction we observe the lattice fringe (called banding) in the horizontal direction. Surprisingly, any frequency component does not exist in the spatial frequency domain of the banding. Also, the banding is detected even when the spatial frequency of the halftone screen exceeds the frequency limit of the visual sensitivity, where the gratings (carrier) are the longitudinal waves of the horizontal direction and the jitter (side band) are transversal waves of the vertical direction. A doubly periodic function takes place above as etiology, and then higher harmonics occur. This complicates an argument. We validated the banding appearance by the carrier grating of the single frequency (69 cpd) and jitter (5.2 cpd) as the side band that removed higher harmonics, to find a response curve by 2AFC in experiment. The correlation between the response curve and the cross term of the jitter spectrum and grating spectrum is absolutely high. So the presence of the nonlinear response is indicated in the early stage. We applied a nonlinear function to the above stimulation to evaluate nonlinearity. As a result, we think the banding spectrum is generated by the configuration of nonlinearity and the spatial frequency characteristic in the early stage.