Patent US5685652A successfully refreshed from Google Patents.
US5685652A
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Method of preparing threshold matrix and method of and apparatus for generating halftone image
Assignee: Screen Holdings Co Ltd
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Filing: 1995-12-18
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Granted: 1997-11-11
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Expires: 2015-12-18
Abstract
Abstract The present invention is made to effectively prevents the occurrence of undesirable dot patterns in the process of FM screening. Threshold values in an M1×M2 threshold matrix are determined using a plurality of fundamental tiles of 2×2 dots in size. The method of the invention arranges the plurality of fundamental tiles in the M1×M2 threshold matrix region, while not allowing the fundamental tiles to have preset forbidden arrangements. This gives a 50% dot pattern including 50% black dots and 50% white dots. The values `0` and `1` are assigned as the upper-most paired bits of digital data representing a threshold value to the positions of two black dots in each fundamental tile, and the values `2` and `3` are assigned as the upper-most paired bits to the positions of two white dots. The values of the other paired bits included in the digital data representing a threshold value are determined by successively dividing the M1×M2 threshold matrix region into four equal parts and allocating different values of `0` through `3` to the four divisional matrix regions.
Inventors
- 👤 Hiroshi Asai
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 19:21
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/40; H04N1/405; H04N1/4051
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
138 words
A method of producing a threshold matrix used in a halftone process of multi-tone image data, said method comprising the steps of: (a) providing a plurality of fundamental tiles each having a size of 2×2 dots in which two black dots and two white dots are arranged in parallel; (b) arranging said plurality of fundamental tiles in a threshold matrix region while preventing said fundamental tiles to form a predetermined forbidden arrangement, thereby determining an array of black dots and white dots in a 50%-halftone image in said threshold matrix region, said 50%-halftone image having an area rate of 50% for both of black dots and white dots; and (c) determining threshold values in said threshold matrix region based on the arrangement of said plurality of fundamental tiles in said threshold matrix region, thereby producing said threshold matrix.
Claim 2
Independent Claim
138 words
A method of producing a threshold matrix used in a halftone process of multi-tone image data, said method comprising the steps of: (a) providing a plurality of fundamental tiles each having a size of 2×2 dots in which two black dots and two white dots are arranged in parallel; (b) arranging said plurality of fundamental tiles in a threshold matrix region while preventing said fundamental tiles to form a predetermined forbidden arrangement, thereby determining an array of black dots and white dots in a 50%-halftone image in said threshold matrix region, said 50%-halftone image having an area rate of 50% for both of black dots and white dots; and (c) determining threshold values in said threshold matrix region based on the arrangement of said plurality of fundamental tiles in said threshold matrix region, thereby producing said threshold matrix.
Claim 3
Dependent Claim
35 words
A method in accordance with claim 1, wherein said predetermined forbidden arrangement comprises a first-type forbidden arrangement in which at least either of black dots and white dots are arrayed in a 2×2 square shape.
Claim 4
Dependent Claim
35 words
A method in accordance with claim 2, wherein said predetermined forbidden arrangement comprises a second-type forbidden arrangement in which at least either of black dots and white dots are arrayed in a 4×1 linear shape.
Claim 5
Dependent Claim
86 words
A method in accordance with claim 3, wherein said step (c) comprises the step of: assigning values of 0 and 1 to an upper-most pair of bits of 2N-bit digital data representing threshold values at the positions of two black dots in each fundamental tile in said threshold matrix region, where N is an integer of at least 2, and assigning values of 2 and 3 to said upper-most pair of bits for threshold values at the positions of two white dots in each fundamental tile.
Claim 6
Dependent Claim
247 words
A method in accordance with claim 4, wherein said threshold matrix region has a width of M1 dots in a first scanning direction and a width of M2 dots in a second scanning direction, where M1 is an integer of a power of 2 and M2 is an integer obtained by multiplying M1 by a power of 4; and said step (c) further comprises the steps of: (1) dividing said threshold matrix region along said second scanning direction into four equal parts to produce four pieces of first divisional regions, and assigning different 2-bit values representing first priorities of 0 through 3 to said first divisional regions, respectively; (2) repeating said step (1) until a width of each of said first divisional regions in said second scanning direction becomes equal to the width M1 of said threshold matrix region, thereby producing a plurality of M1×M1 divisional regions; (3) dividing each of said plurality of M1×M1 divisional regions into two equal parts both in said first scanning direction and said second scanning direction to produce four pieces of second divisional regions, and assigning different 2-bit values representing second priorities of 0 through 3 to said second divisional regions, respectively; (4) repeating said step (3) until each of said second divisional regions has a width of 2 dots; and (5) allocating the first and second priorities to (N-1) pairs of lower bits in said 2N-bit digital data representing threshold values, thereby determining threshold values in said threshold matrix region.
Claim 7
Dependent Claim
35 words
A method in accordance with claim 1, wherein said predetermined forbidden arrangement comprises a second-type forbidden arrangement in which at least either of black dots and white dots are arrayed in a 4×1 linear shape.
Claim 8
Dependent Claim
86 words
A method in accordance with claim 6, wherein said step (c) comprises the step of: assigning values of 0 and 1 to an upper-most pair of bits of 2N-bit digital data representing threshold values at the positions of two black dots in each fundamental tile in said threshold matrix region, where N is an integer of at least 2, and assigning values of 2 and 3 to said upper-most pair of bits for threshold values at the positions of two white dots in each fundamental tile.
Claim 9
Dependent Claim
247 words
A method in accordance with claim 7, wherein said threshold matrix region has a width of M1 dots in a first scanning direction and a width of M2 dots in a second scanning direction, where M1 is an integer of a power of 2 and M2 is an integer obtained by multiplying M1 by a power of 4; and said step (c) further comprises the steps of: (1) dividing said threshold matrix region along said second scanning direction into four equal parts to produce four pieces of first divisional regions, and assigning different 2-bit values representing first priorities of 0 through 3 to said first divisional regions, respectively; (2) repeating said step (1) until a width of each of said first divisional regions in said second scanning direction becomes equal to the width M1 of said threshold matrix region, thereby producing a plurality of M1×M1 divisional regions; (3) dividing each of said plurality of M1×M1 divisional regions into two equal parts both in said first scanning direction and said second scanning direction to produce four pieces of second divisional regions, and assigning different 2-bit values representing second priorities of 0 through 3 to said second divisional regions, respectively; (4) repeating said step (3) until each of said second divisional regions has a width of 2 dots; and (5) allocating the first and second priorities to (N-1) pairs of lower bits in said 2N-bit digital data representing threshold values, thereby determining threshold values in said threshold matrix region.
Claim 10
Dependent Claim
86 words
A method in accordance with claim 1, wherein said step (c) comprises the step of: assigning values of 0 and 1 to an upper-most pair of bits of 2N-bit digital data representing threshold values at the positions of two black dots in each fundamental tile in said threshold matrix region, where N is an integer of at least 2, and assigning values of 2 and 3 to said upper-most pair of bits for threshold values at the positions of two white dots in each fundamental tile.
Claim 11
Dependent Claim
247 words
A method in accordance with claim 9, wherein said threshold matrix region has a width of M1 dots in a first scanning direction and a width of M2 dots in a second scanning direction, where M1 is an integer of a power of 2 and M2 is an integer obtained by multiplying M1 by a power of 4; and said step (c) further comprises the steps of: (1) dividing said threshold matrix region along said second scanning direction into four equal parts to produce four pieces of first divisional regions, and assigning different 2-bit values representing first priorities of 0 through 3 to said first divisional regions, respectively; (2) repeating said step (1) until a width of each of said first divisional regions in said second scanning direction becomes equal to the width M1 of said threshold matrix region, thereby producing a plurality of M1×M1 divisional regions; (3) dividing each of said plurality of M1×M1 divisional regions into two equal parts both in said first scanning direction and said second scanning direction to produce four pieces of second divisional regions, and assigning different 2-bit values representing second priorities of 0 through 3 to said second divisional regions, respectively; (4) repeating said step (3) until each of said second divisional regions has a width of 2 dots; and (5) allocating the first and second priorities to (N-1) pairs of lower bits in said 2N-bit digital data representing threshold values, thereby determining threshold values in said threshold matrix region.
Claim 12
Independent Claim
195 words
A method of generating a halftone image by comparing multi-tone image data with a threshold matrix, said method comprising the steps of: (a) providing a first memory for storing a threshold matrix, said threshold matrix being prepared by (i) providing a plurality of fundamental tiles each having a size of 2×2 dots in which two black dots and two white dots are arranged in parallel; (ii) arranging said plurality of fundamental tiles in a threshold matrix region while preventing said fundamental tiles to form a predetermined forbidden arrangement, thereby determining an array of black dots and white dots in a 50%-halftone image in said threshold matrix region, said 50%-halftone image having an area rate of 50% for both of black dots and white dots; and (iii) determining threshold values in said threshold matrix region based on the arrangement of said plurality of fundamental tiles in said threshold matrix region, thereby producing said threshold matrix; (b) comparing multi-tone image data with a threshold value read out of said first memory, thereby converting said multi-tone image data to a recording signal representing a halftone image; and (c) producing said halftone image in response to said recording signal.
Claim 13
Independent Claim
195 words
A method of generating a halftone image by comparing multi-tone image data with a threshold matrix, said method comprising the steps of: (a) providing a first memory for storing a threshold matrix, said threshold matrix being prepared by (i) providing a plurality of fundamental tiles each having a size of 2×2 dots in which two black dots and two white dots are arranged in parallel; (ii) arranging said plurality of fundamental tiles in a threshold matrix region while preventing said fundamental tiles to form a predetermined forbidden arrangement, thereby determining an array of black dots and white dots in a 50%-halftone image in said threshold matrix region, said 50%-halftone image having an area rate of 50% for both of black dots and white dots; and (iii) determining threshold values in said threshold matrix region based on the arrangement of said plurality of fundamental tiles in said threshold matrix region, thereby producing said threshold matrix; (b) comparing multi-tone image data with a threshold value read out of said first memory, thereby converting said multi-tone image data to a recording signal representing a halftone image; and (c) producing said halftone image in response to said recording signal.
Claim 14
Dependent Claim
35 words
A method in accordance with claim 11, wherein said predetermined forbidden arrangement comprises a first-type forbidden arrangement in which at least either of black dots and white dots are arrayed in a 2×2 square shape.
Claim 15
Dependent Claim
35 words
A method in accordance with claim 12, wherein said predetermined forbidden arrangement comprises a second-type forbidden arrangement in which at least either of black dots and white dots are arrayed in a 4×1 linear shape.
Claim 16
Dependent Claim
86 words
A method in accordance with claim 13, wherein said step (iii) comprises the step of: assigning values of 0 and 1 to an upper-most pair of bits of 2N-bit digital data representing threshold values at the positions of two black dots in each fundamental tile in said threshold matrix region, where N is an integer of at least 2, and assigning values of 2 and 3 to said upper-most pair of bits for threshold values at the positions of two white dots in each fundamental tile.
Claim 17
Dependent Claim
247 words
A method in accordance with claim 14, wherein said threshold matrix region has a width of M1 dots in a first scanning direction and a width of M2 dots in a second scanning direction, where M1 is an integer of a power of 2 and M2 is an integer obtained by multiplying M1 by a power of 4; and said step (iii) further comprises the steps of: (1) dividing said threshold matrix region along said second scanning direction into four equal parts to produce four pieces of first divisional regions, and assigning different 2-bit values representing first priorities of 0 through 3 to said first divisional regions, respectively; (2) repeating said step (1) until a width of each of said first divisional regions in said second scanning direction becomes equal to the width M1 of said threshold matrix region, thereby producing a plurality of M1×M1 divisional regions; (3) dividing each of said plurality of M1×M1 divisional regions into two equal parts both in said first scanning direction and said second scanning direction to produce four pieces of second divisional regions, and assigning different 2-bit values representing second priorities of 0 through 3 to said second divisional regions, respectively; (4) repeating said step (3) until each of said second divisional regions has a width of 2 dots; and (5) allocating the first and second priorities to (N-1) pairs of lower bits in said 2N-bit digital data representing threshold values, thereby determining threshold values in said threshold matrix region.
Claim 18
Independent Claim
203 words
An apparatus for generating a halftone image by comparing multi-tone image data with a threshold matrix, said apparatus comprising: a memory for storing a threshold matrix, said threshold matrix being prepared by (i) providing a plurality of fundamental tiles each having a size of 2×2 dots in which two black dots and two white dots are arranged in parallel; (ii) arranging said plurality of fundamental tiles in a threshold matrix region while preventing said fundamental tiles to form a predetermined forbidden arrangement, thereby determining an array of black dots and white dots in a 50%-halftone image in said threshold matrix region, said 50%-halftone image having an area rate of 50% for both of black dots and white dots; and (iii) determining threshold values in said threshold matrix region based on the arrangement of said plurality of fundamental tiles in said threshold matrix region, thereby producing said threshold matrix; means for reading out a threshold value from said memory; and a comparator for comparing multi-tone image data with the threshold value read out of said memory, thereby converting said multi-tone image data to a recording signal representing a halftone image; and recording means for producing said halftone image in response to said recording signal.
Claim 19
Independent Claim
203 words
An apparatus for generating a halftone image by comparing multi-tone image data with a threshold matrix, said apparatus comprising: a memory for storing a threshold matrix, said threshold matrix being prepared by (i) providing a plurality of fundamental tiles each having a size of 2×2 dots in which two black dots and two white dots are arranged in parallel; (ii) arranging said plurality of fundamental tiles in a threshold matrix region while preventing said fundamental tiles to form a predetermined forbidden arrangement, thereby determining an array of black dots and white dots in a 50%-halftone image in said threshold matrix region, said 50%-halftone image having an area rate of 50% for both of black dots and white dots; and (iii) determining threshold values in said threshold matrix region based on the arrangement of said plurality of fundamental tiles in said threshold matrix region, thereby producing said threshold matrix; means for reading out a threshold value from said memory; and a comparator for comparing multi-tone image data with the threshold value read out of said memory, thereby converting said multi-tone image data to a recording signal representing a halftone image; and recording means for producing said halftone image in response to said recording signal.
Claim 20
Dependent Claim
35 words
An apparatus in accordance with claim 16, wherein said predetermined forbidden arrangement comprises a first-type forbidden arrangement in which at least either of black dots and white dots are arrayed in a 2×2 square shape.
Claim 21
Dependent Claim
35 words
An apparatus in accordance with claim 17, wherein said predetermined forbidden arrangement comprises a second-type forbidden arrangement in which at least either of black dots and white dots are arrayed in a 4×1 linear shape.
Claim 22
Dependent Claim
86 words
An apparatus in accordance with claim 18, wherein said step (iii) comprises the step of: assigning values of 0 and 1 to an upper-most pair of bits of 2N-bit digital data representing threshold values at the positions of two black dots in each fundamental tile in said threshold matrix region, where N is an integer of at least 2, and assigning values of 2 and 3 to said upper-most pair of bits for threshold values at the positions of two white dots in each fundamental tile.
Claim 23
Dependent Claim
247 words
An apparatus in accordance with claim 19, wherein said threshold matrix region has a width of M1 dots in a first scanning direction and a width of M2 dots in a second scanning direction, where M1 is an integer of a power of 2 and M2 is an integer obtained by multiplying M1 by a power of 4; and said step (iii) further comprises the steps of: (1) dividing said threshold matrix region along said second scanning direction into four equal parts to produce four pieces of first divisional regions, and assigning different 2-bit values representing first priorities of 0 through 3 to said first divisional regions, respectively; (2) repeating said step (1) until a width of each of said first divisional regions in said second scanning direction becomes equal to the width M1 of said threshold matrix region, thereby producing a plurality of M1×M1 divisional regions; (3) dividing each of said plurality of M1×M1 divisional regions into two equal parts both in said first scanning direction and said second scanning direction to produce four pieces of second divisional regions, and assigning different 2-bit values representing second priorities of 0 through 3 to said second divisional regions, respectively; (4) repeating said step (3) until each of said second divisional regions has a width of 2 dots; and (5) allocating the first and second priorities to (N-1) pairs of lower bits in said 2N-bit digital data representing threshold values, thereby determining threshold values in said threshold matrix region.
References Cited (Backward Citations)
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 2000-11-10 | 2001-05-12 | 2001-11-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2004-11-10 | 2005-05-12 | 2005-11-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2008-11-10 | 2009-05-12 | 2009-11-11 | $7700.00 | Window Closed / Lapsed |