Method of and apparatus for recording halftone images

Claim 1

A method of recording a plurality of color separation images of a color image as halftone images, said method comprising the steps of: (a) presetting a reference triangle having a first apex, a second apex, a third apex, a first side facing to said first apex, a second side facing to said second apex, and a third side facing to said third apex; (b) producing a first halftone image with the steps of: (b-1) selecting a first parallelogram out of a first set of a plurality of parallelograms which are formed from three apexes consisting of said first apex, a first middle point of said first side, and one of said second and third apexes; (b-2) virtually laying out said first parallelogram as a first unit area repeatedly over a first image plane; and (b-3) locating one halftone dot with respect to each said first unit area; (c) producing a second halftone image with the steps of: (c-1) selecting a second parallelogram out of a second set of a plurality of parallelograms which are formed from three apexes consisting of said second apex, a second middle point of said second side, and one of said first and third apexes; (c-2) virtually laying out said second parallelogram as a second unit area repeatedly over a second image plane; and (c-3) locating one halftone dot with respect to each said second unit area; and (d) producing a third halftone image with the steps of: (d-1) selecting a third parallelogram out of a third set of a plurality of parallelograms which are formed from three apexes consisting of said third apex, a third middle point of said third side, and one of said first and second apexes; (d-2) virtually laying out said third parallelogram as a third unit area repeatedly over a third image plane; and (d-3) locating one halftone dot with respect to each said third unit area.

Claim 2

A method of recording a plurality of color separation images of a color image as halftone images, said method comprising the steps of: (a) presetting a reference triangle having a first apex, a second apex, a third apex, a first side facing to said first apex, a second side facing to said second apex, and a third side facing to said third apex; (b) producing a first halftone image with the steps of: (b-1) selecting a first parallelogram out of a first set of a plurality of parallelograms which are formed from three apexes consisting of said first apex, a first middle point of said first side, and one of said second and third apexes; (b-2) virtually laying out said first parallelogram as a first unit area repeatedly over a first image plane; and (b-3) locating one halftone dot with respect to each said first unit area; (c) producing a second halftone image with the steps of: (c-1) selecting a second parallelogram out of a second set of a plurality of parallelograms which are formed from three apexes consisting of said second apex, a second middle point of said second side, and one of said first and third apexes; (c-2) virtually laying out said second parallelogram as a second unit area repeatedly over a second image plane; and (c-3) locating one halftone dot with respect to each said second unit area; and (d) producing a third halftone image with the steps of: (d-1) selecting a third parallelogram out of a third set of a plurality of parallelograms which are formed from three apexes consisting of said third apex, a third middle point of said third side, and one of said first and second apexes; (d-2) virtually laying out said third parallelogram as a third unit area repeatedly over a third image plane; and (d-3) locating one halftone dot with respect to each said third unit area.

Claim 7

An apparatus of recording a plurality of color separation images for a plurality of colors as halftone images, comprising: (a) image capturing means for capturing a plurality of color separation image signals representing a color image for at least three colors, respectively; (b) a mount for mounting photosensitive material, on which a plurality of halftone images are to be recorded; (c) a screen pattern memory for storing three sets of threshold values for said respective three colors, said three sets of threshold values being arranged in first through third unit areas, respectively, each of said first through third unit areas being laid out repeatedly in first through third X-Y coordinate systems, respectively, each of said first through third unit areas being defined by: (c-1) presetting a reference triangle having a first apex, a second apex, a third apex, a first side facing to said first apex, a second side facing to said second apex, and a third side facing to said third apex; (c-2) selecting a first parallelogram as said first unit area out of a first set of a plurality of parallelograms which are formed from three apexes consisting of said first apex, a first middle point of said first side, and one of said second and third apexes, the sides of said first parallelogram being parallel to the coordinate axes of said first X-Y coordinate system; (c-3) selecting a second parallelogram as said second unit area out of a second set of a plurality of parallelograms which are formed from three apexes consisting of said second apex, a second middle point of said second side, and one of said first and third apexes, the sides of said second parallelogram being parallel to the coordinate axes of said second X-Y coordinate system; and (c-4) selecting a third parallelogram as said third unit area out of a third set of a plurality of parallelograms which are formed from three apexes consisting of said third apex, a third middle point of said third side, and one of said first and second apexes, the sides of said third parallelogram being parallel to the coordinate axes of said third X-Y coordinate system; (d) coordinate signal generation means for generating a coordinate signal representing a position in a Cartesian U-V coordinate system, said U and V denoting a primary scanning direction and a secondary scanning direction on said mount, respectively, said U-V coordinate system being set in predetermined relations to said first through third X-Y coordinate systems; (e) address generation means for transforming said coordinate signal from U-V coordinates into first through third X-Y coordinates to generate address for said screen pattern memory; (f) comparator means for comparing each of said plurality of color separation image signals with a target threshold value read out from each of said three sets of threshold values stored in said screen pattern memory as a function of said first through third X-Y coordinates, to thereby generate a plurality of exposure signals for said respective three colors, said plurality of exposure signals indicating whether or not to expose target recording pixels on said photosensitive material; and (g) exposure means for exposing said photosensitive material mounted on said drum responsive to each of said plurality of exposure signals, thereby recording said plurality of color separation images for said three colors as halftone images.

Claim 8

An apparatus of recording a plurality of color separation images for a plurality of colors as halftone images, comprising: (a) image capturing means for capturing a plurality of color separation image signals representing a color image for at least three colors, respectively; (b) a mount for mounting photosensitive material, on which a plurality of halftone images are to be recorded; (c) a screen pattern memory for storing three sets of threshold values for said respective three colors, said three sets of threshold values being arranged in first through third unit areas, respectively, each of said first through third unit areas being laid out repeatedly in first through third X-Y coordinate systems, respectively, each of said first through third unit areas being defined by: (c-1) presetting a reference triangle having a first apex, a second apex, a third apex, a first side facing to said first apex, a second side facing to said second apex, and a third side facing to said third apex; (c-2) selecting a first parallelogram as said first unit area out of a first set of a plurality of parallelograms which are formed from three apexes consisting of said first apex, a first middle point of said first side, and one of said second and third apexes, the sides of said first parallelogram being parallel to the coordinate axes of said first X-Y coordinate system; (c-3) selecting a second parallelogram as said second unit area out of a second set of a plurality of parallelograms which are formed from three apexes consisting of said second apex, a second middle point of said second side, and one of said first and third apexes, the sides of said second parallelogram being parallel to the coordinate axes of said second X-Y coordinate system; and (c-4) selecting a third parallelogram as said third unit area out of a third set of a plurality of parallelograms which are formed from three apexes consisting of said third apex, a third middle point of said third side, and one of said first and second apexes, the sides of said third parallelogram being parallel to the coordinate axes of said third X-Y coordinate system; (d) coordinate signal generation means for generating a coordinate signal representing a position in a Cartesian U-V coordinate system, said U and V denoting a primary scanning direction and a secondary scanning direction on said mount, respectively, said U-V coordinate system being set in predetermined relations to said first through third X-Y coordinate systems; (e) address generation means for transforming said coordinate signal from U-V coordinates into first through third X-Y coordinates to generate address for said screen pattern memory; (f) comparator means for comparing each of said plurality of color separation image signals with a target threshold value read out from each of said three sets of threshold values stored in said screen pattern memory as a function of said first through third X-Y coordinates, to thereby generate a plurality of exposure signals for said respective three colors, said plurality of exposure signals indicating whether or not to expose target recording pixels on said photosensitive material; and (g) exposure means for exposing said photosensitive material mounted on said drum responsive to each of said plurality of exposure signals, thereby recording said plurality of color separation images for said three colors as halftone images.

Claim 14

An apparatus of recording a plurality of color separation images for a plurality of colors as halftone images, comprising: (a) image capturing means for capturing a plurality of color separation image signals representing a color image for at least three colors, respectively; (b) a mount for mounting photosensitive material, on which a plurality of halftone images are to be recorded; (c) a screen pattern memory for storing three sets of threshold values for said respective three colors, said three sets of threshold values being arranged in first through third block areas, respectively, said first through third block areas including a plurality of first unit areas, a plurality of second unit areas, and a plurality of third unit areas, respectively, each of said first through third block areas being laid out repeatedly in an X-Y coordinate system, each of said first through third unit areas being defined by: (c-1) presetting a reference triangle having a first apex, a second apex, a third apex, a first side facing to said first apex, a second side facing to said second apex, and a third side facing to said third apex; (c-2) selecting a first parallelogram as said first unit area out of a first set of a plurality of parallelograms which are formed from three apexes consisting of said first apex, a first middle point of said first side, and one of said second and third apexes; (c-3) selecting a second parallelogram as said second unit area out of a second set of a plurality of parallelograms which are formed from three apexes consisting of said second apex, a second middle point of said second side, and one of said first and third apexes; and (c-4) selecting a third parallelogram as said third unit area out of a third set of a plurality of parallelograms which are formed from three apexes consisting of said third apex, a third middle point of said third side, and one of said first and second apexes; (d) coordinate signal generation means for generating a coordinate signal representing a position in a Cartesian U-V coordinate system, said U and V denoting a primary scanning direction and a secondary scanning direction on said mount, respectively, said U-V coordinate system being set in predetermined relation to said X-Y coordinate system; (e) address generation means for transforming said coordinate signal from said U-V coordinates into said X-Y coordinates to generate an address for said screen pattern memory; (f) comparator means for comparing each of said plurality of color separation image signals with a target threshold value read out from each of said three sets of threshold values stored in said screen pattern memory as a function of said corrected X-Y coordinates, to thereby generate a plurality of exposure signals for said respective three colors, said plurality of exposure signals indicating whether or not to expose target recording pixels on said photosensitive material; and (g) exposure means for exposing said photosensitive material mounted on said drum responsive to each of said plurality of exposure signals, thereby recording said plurality of color separation images for said three colors as halftone images.

Claim 15

An apparatus of recording a plurality of color separation images for a plurality of colors as halftone images, comprising: (a) image capturing means for capturing a plurality of color separation image signals representing a color image for at least three colors, respectively; (b) a mount for mounting photosensitive material, on which a plurality of halftone images are to be recorded; (c) a screen pattern memory for storing three sets of threshold values for said respective three colors, said three sets of threshold values being arranged in first through third block areas, respectively, said first through third block areas including a plurality of first unit areas, a plurality of second unit areas, and a plurality of third unit areas, respectively, each of said first through third block areas being laid out repeatedly in an X-Y coordinate system, each of said first through third unit areas being defined by: (c-1) presetting a reference triangle having a first apex, a second apex, a third apex, a first side facing to said first apex, a second side facing to said second apex, and a third side facing to said third apex; (c-2) selecting a first parallelogram as said first unit area out of a first set of a plurality of parallelograms which are formed from three apexes consisting of said first apex, a first middle point of said first side, and one of said second and third apexes; (c-3) selecting a second parallelogram as said second unit area out of a second set of a plurality of parallelograms which are formed from three apexes consisting of said second apex, a second middle point of said second side, and one of said first and third apexes; and (c-4) selecting a third parallelogram as said third unit area out of a third set of a plurality of parallelograms which are formed from three apexes consisting of said third apex, a third middle point of said third side, and one of said first and second apexes; (d) coordinate signal generation means for generating a coordinate signal representing a position in a Cartesian U-V coordinate system, said U and V denoting a primary scanning direction and a secondary scanning direction on said mount, respectively, said U-V coordinate system being set in predetermined relation to said X-Y coordinate system; (e) address generation means for transforming said coordinate signal from said U-V coordinates into said X-Y coordinates to generate an address for said screen pattern memory; (f) comparator means for comparing each of said plurality of color separation image signals with a target threshold value read out from each of said three sets of threshold values stored in said screen pattern memory as a function of said corrected X-Y coordinates, to thereby generate a plurality of exposure signals for said respective three colors, said plurality of exposure signals indicating whether or not to expose target recording pixels on said photosensitive material; and (g) exposure means for exposing said photosensitive material mounted on said drum responsive to each of said plurality of exposure signals, thereby recording said plurality of color separation images for said three colors as halftone images.