Spread spectrum digital screening
DC CAFCFirst Claim
1. A digital screening mask comprising:
- a computer readable memory for storing data, wherein stored in the memory is a two dimensional array of optical density threshold values, each value being in a range between a minimum value and a maximum value, wherein a frequency domain plot of said array of threshold values is characterized by a function in magnitude independent of angle within a band of frequencies between a minimum frequency and a maximum frequency, the minimum frequency normally being imperceptible to humans and the maximum frequency being a frequency within the ability of a printing press to print.
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Abstract
A spread spectrum digital screening mask and a method and system for digital screening a continuous tone image with the spread spectrum digital screening mask. The mask is characterized in the frequency domain by a function in magnitude independent of angle within a band of frequencies between a minimum frequency and a maximum frequency. The mask may be further characterized by its thresholded binary planes at each of a plurality of predetermined threshold values. The binary planes are characterized in frequency domain by magnitudes primarily distributed within the band of frequencies. For each binary plane, the number of pixels having one of the binary values divided by the total number of pixels in the binary plane equals a fraction determined by the predetermined threshold value of the binary plane divided by the maximum threshold value.
118 Citations
19 Claims
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1. A digital screening mask comprising:
a computer readable memory for storing data, wherein stored in the memory is a two dimensional array of optical density threshold values, each value being in a range between a minimum value and a maximum value, wherein a frequency domain plot of said array of threshold values is characterized by a function in magnitude independent of angle within a band of frequencies between a minimum frequency and a maximum frequency, the minimum frequency normally being imperceptible to humans and the maximum frequency being a frequency within the ability of a printing press to print. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A binary reproduction of a continuous tone image comprising:
a substrate bearing a visible image characterized in the frequency domain by frequencies below 50 dots per inch, said image formed by a matrix of dots wherein the matrix of dots is characterized in the frequency domain by a function between a minimum frequency and a maximum frequency that is uniform with respect to angle, the minimum frequency being normally imperceptible to a human viewing the visible image and the maximum frequency being a frequency within the ability of a printing press to print. - View Dependent Claims (19)
Specification