Abstract

We present a Fourier-transform analysis of the moiré-pattern formation commonly observed in images reconstructed from scanned halftone pictures. The analysis takes into account the halftone screen frequency, the scanner sampling frequency, the nonzero size of the scanner aperture, the angle between the scan direction and the halftone screen and the shape (square or parallelogram) of the scanner sampling lattice. A fortran program based on the mathematical analysis is shown to permit not only simulation of a wide variety of moiré phenomena actually observed in practice but also explanation of their origin. Several important observations are discussed, including the following: (1) Moiré fringes can result from the beating together of clusters of Fourier spatial frequencies. (2) Moiré patterns other than square-grid fringe arrays are associated with parallelogram (nonsquare) sampling lattices. (3) Fixed-value thresholding intensifies moiré patterns.

© 1982 Optical Society of America

Halftone method with edge enhancement and Moiré suppression

Paul G. Roetling
J. Opt. Soc. Am. 66(10) 985-989 (1976)

Minimizing stochastic moiré in frequency-modulated halftones by means of green-noise masks

Daniel L. Lau, Arif M. Khan, and Gonzalo R. Arce
J. Opt. Soc. Am. A 19(11) 2203-2217 (2002)

Random quasiperiodic halftone process

J. P. Allebach and B. Liu
J. Opt. Soc. Am. 66(9) 909-917 (1976)

Moiré and higher grating harmonics

Olof Bryngdahl
J. Opt. Soc. Am. 65(6) 685-694 (1975)

Hidden images in halftone pictures

Joseph Rosen and Bahram Javidi
Appl. Opt. 40(20) 3346-3353 (2001)