Importance

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Abstract

Sequential scanned scaled density data representing a varying tone image is electronically screened to form binary element data that when imaged to form an array of orthogonally arranged binary elements on a member produces screened color separation plates of that original image suitable for use as the printing plates in a lithographic printing press. Screening occurs by comparing sequential density data with selected screen matrix data contained in a memory. The matrix data is ordered with density values increasing outwardly from the matrix center to the corners and edges. The matrix data is selected from matrix locations related to the desired screen frequency and angle with the selected matrix locations being determined by the application of fundamental right triangle trigonometric relationships to the matrix. Screening and imaging occurs sequentially with two density data being compared to matrix data simultaneously. The binary elements of the several plates are produced in one pass across the surface of the member.

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First Claim