Method and apparatus for multi-color printing using hybrid dot-line halftone composite screens

Abstract

A method and apparatus for generating a multicolor image using halftone screens employs a dot structure dot growth pattern for one or more of the colors and a line structure dot growth pattern for at least two or more of the other colors.

1 . An apparatus for configuring image information for printing of an image having at least three different colors, comprising:
 a screen generator or generators for generating halftone screen color separation image data for each of the at least three different colors, the screen generator or generators generating image data in the form of halftone screens representative of the image at predetermined respective screen angles wherein for each of at least two of the three colors a first type of dot growth is pattern is provided and is operational to generate halftone cells of different density and for the third of the three colors a second type of dot growth pattern is provided which is different from the first type of dot growth pattern used commonly for the said at least two of the three colors, wherein the first type of growth pattern is selected from the group consisting of the dot structure dot growth pattern and the line structure dot growth pattern and the second type of growth pattern is selected from the group consisting of the dot structure dot growth pattern and the line structure dot growth pattern and further wherein the respective screen angles for the at least two of the three colors and for the third of the three colors are all different from each other.   
   
   
       2 . The apparatus of  claim 1  and wherein the at least two of the three colors are generated with a line structure dot growth pattern and the third of the at least three colors is generated with a dot structure dot growth pattern. 
   
   
       3 . The apparatus of  claim 2  and wherein the at least three different colors are at least five colors and the at least five colors include cyan, magenta and yellow and at least four of the at least five colors are formed with halftone cells of different screen angles. 
   
   
       4 . The apparatus of  claim 3  and wherein the at least five colors includes blue. 
   
   
       5 . The apparatus of  claim 4  and wherein the dot structure dot growth pattern and the line structure dot growth pattern employ the creation of different gray levels at pixel locations. 
   
   
       6 . The apparatus of  claim 5  and wherein one of the at least five colors includes black and the angle of the black halftone screen is directed at an angle that is perpendicular to the blue halftone screen. 
   
   
       7 . The apparatus of  claim 3  and wherein the line structures formed by the halftone cells with the line structure dot growth pattern are perpendicular to each other. 
   
   
       8 . The apparatus of  claim 3  and wherein the line structures formed by the halftone cells with the line structure dot growth pattern are at an angle of between 53° and 64° to each other. 
   
   
       9 . The apparatus of  claim 8  and wherein the yellow color is formed with a halftone screen generated printer dot structure dot growth pattern and at a line frequency of at least 1.1 times the line frequency of the lowest line frequency employed for any of the other colors. 
   
   
       10 . The apparatus of  claim 9  and wherein the yellow halftone screen is at an angle ±10 of midway between the respective angles of two halftone screens of different colors. 
   
   
       11 . The apparatus of  claim 1  and wherein one color is formed as a composite of two halftone screens of different screen angles. 
   
   
       12 . The apparatus of  claim 11  and wherein the one color formed as a composite of two halftone screens is a composite of two halftone screens at a 60° angle to each other. 
   
   
       13 . The apparatus of  claim 1  in combination with a printer for printing the image information as a halftone image in the at least three colors. 
   
   
       14 . A method for configuring image information for printing of an image having at least three different colors, comprising:
 generating halftone screen color separation image data for each of the at least three different colors in the form of halftone screens representative of the image at predetermined respective screen angles wherein for each of at least two of the three colors a first type of dot growth is pattern is provided and is operational to generate halftone cells of different density and for the third of the three colors a second type of dot growth pattern is provided which is different from the first type of dot growth pattern used commonly for the said at least two of the three colors, wherein the first type of growth pattern is selected from the group consisting of the dot structure dot growth pattern and the line structure dot growth pattern and the second type of growth pattern is selected from the group consisting of the dot structure dot growth pattern and the line structure dot growth pattern and further wherein the respective screen angles for the at least two of the three colors and for the third of the three colors are all different from each other.   
   
   
       15 . The method of  claim 14  and wherein the at least two of the three colors are generated with a line structure dot growth pattern and the third of the at least three colors is generated with a dot structure dot growth pattern. 
   
   
       16 . The method of  claim 14  and wherein the at least three different colors are at least five colors and the at least five colors include cyan, magenta and yellow and at least four of the at least five colors are formed with halftone cells of different screen angles. 
   
   
       17 . The method of  claim 16  and wherein the at least five colors includes blue. 
   
   
       18 . The method of  claim 17  and wherein the dot structure dot growth pattern and the line structure dot growth pattern employ the creation of different gray levels at pixel locations. 
   
   
       19 . The method of  claim 18  and wherein one of the at least five colors includes black and the angle of the black halftone screen is directed at an angle that is perpendicular to the blue halftone screen. 
   
   
       20 . The method of  claim 14  and wherein the line structures formed by the halftone cells with the line structure dot growth pattern are perpendicular to each other. 
   
   
       21 . The method of  claim 14  and wherein the line structures formed by the halftone cells with the line structure dot growth pattern are at an angle of between 53° and 64° to each other. 
   
   
       22 . The method of  claim 21  and wherein yellow is one of the at least five colors and the yellow color is formed with a halftone screen generated printer dot structure dot growth pattern and at a line frequency of at least 1.1 times the line frequency of the lowest line frequency employed for any of the other colors. 
   
   
       23 . The method of  claim 22  and wherein the line structure of the yellow halftone screen is at an angle ±1° of midway between the respective angles of two halftone screens of different colors. 
   
   
       24 . The method of  claim 14  and wherein one color is formed as a composite of two halftone screens. 
   
   
       25 . The method of  claim 14  and wherein the one color formed as a composite of two halftone screens is a composite of two halftone screens at a 60° angle to each other. 
   
   
       26 . The method for generating a multicolor image using halftone screens comprising:
 forming halftone dots using a dot structure dot growth pattern for the halftone cells of one or more of the colors; and   forming halftone lines using a line structure dot growth pattern for the halftone cells of at least two of the other colors.