Screening system and method for color reproduction in offset printing
AssigneeMiles Inc.
InventorPaul A. Delabastita
Life of this patent
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Abstract
A screening system and method are disclosed for reproduction of images in printing. The screening angles that are used are close, but not identical to conventional screening angles. The reproduction is nevertheless Moire free by the fact that the deviations in angles from the conventional system are exactly offset by the deviations in line rulings. The screening system is particularly advantageous when used for combinations of screens with rational tangent angles. The Moire free combination of rational tangent screens can be rotated by a constant angle with the amount of rotation controlled in small increments.
Claims11
A screening system for printed reproduction of images comprising first, second and third separation screens having different screen angles and each having rulings with at least two of the screen rulings being different and with at least one vector sum of two frequency components of one pair of screens being equal to at least one frequency component of the other screen or to a multiple or submultiple of said at least one frequency component of the other screen, but not including screens having screen angles that are offset by thirty degrees or a multiple thereof and in which vector lengths of the frequency components are identical.
A screening system for printed reproduction of images comprising first, second and third separation screens having different screen angles and each having rulings with at least two of the screen rulings being different and with a multiple of at least one vector sum of two frequency components of one pair of screens being equal to a multiple of at least one frequency component of the other screen, but not including screens having screen angles that are offset by thirty degrees or a multiple thereof and in which vector lengths of the frequency components are identical.
A screening system for printed reproduction of images comprising first, second and third separation screens having different screen angles and each having rulings with at least two of the screen rulings being different and with a submultiple of at least one vector sum of two frequency components of one pair of screens being equal to a submultiple of at least one frequency component of the other screen, but not including screens having screen angles that are offset by thirty degrees or a multiple thereof and in which vector lengths of the frequency components are identical.
A method for producing half-tone screen function values comprising the steps of:
- A. generating a rectangular tile having dots that are preangled under a rational tangent angle;
- and,
- B. sampling said rectangular tile under a different rational tangent angle to produce half-tone screen function values.
Dependencies are inferred from the claim text.