Systems and methods for designing zero-shift supercell halftone screens

Abstract

Conventional design tools were not developed for designing square zero-shift supercells. Conventionally, solutions that enable square zero-shift supercells were found by trial and error or by exhaustive analysis. According to a first design criterion of this invention, a non-square supercell in a first frame of reference has a diagonal that is equal in length to the diagonal of a square supercell in a second frame of reference rotated at a desired screen angle to the first frame of reference. The screen angle is a function of the lengths of the sides of the non-square supercell in the first frame of reference. According to a second design criterion, if the area of the corresponding square supercell in the second frame of reference is an integer, a square zero-shift supercell can be designed based on the lengths of the sides of the non-square supercell in the first frame of reference.

1 . A method for designing a halftone screen having a square zero-shift halftone supercell, comprising: 
 selecting a desired length for a first side of a pair of sides of a non-square supercell;    selecting a length for a second side of the pair of sides of the non-square supercell;    determining an integer number of centers within the square zero-shift halftone supercell based on the side lengths of the first and second sides of the non-square supercell.    
   
   
       2 . The method of  claim 1 , further comprising determining an angle between a first frame of reference in which the non-square supercell lies and a second frame of reference in which the square zero-shift halftone supercell lies based on the selected lengths of the first and second sides of the non-square supercell.  
   
   
       3 . The method of  claim 1 , further comprising: 
 estimating an effective visual area of a basic halftone cell of the halftone screen based on a resolution of a printer by which the halftone screen will be printed and a desired screen frequency; and    determining a supercell area based on the estimated effective visual area and the determined integer number of centers of the square zero-shift halftone supercell.    
   
   
       4 . The method of  claim 3 , further comprising: 
 determining a nominal side length of the square zero-shift halftone supercell based on the determined supercell area; and    determining an actual integer-valued side length of the square zero-shift halftone supercell based on the determined nominal side length of the square zero-shift halftone supercell.    
   
   
       5 . The method of  claim 4 , further comprising: 
 determining an actual effective visual area of the basic halftone cell based on the actual integer-valued side length of the square zero-shift halftone supercell; and    determining an actual screen frequency based on the actual effective visual area of the basic halftone cell and the printer resolution.    
   
   
       6 . The method of  claim 1 , further comprising: 
 selecting an effective visual area of a basic halftone cell of the halftone screen;    determining a supercell area based on the selected effective visual area and the determined integer number of centers.    
   
   
       7 . The method of  claim 6 , further comprising: 
 determining a nominal side length of the square zero-shift halftone supercell based on the determined supercell area; and    determining an actual integer-valued side length of the square zero-shift halftone supercell based on the determined nominal side length of the square zero-shift halftone supercell.    
   
   
       8 . The method of  claim 7 , further comprising determining an actual screen frequency based on the effective visual area of the basic halftone cell and a resolution of a printer by which the halftone screen will be printed.  
   
   
       9 . A square zero-shift supercell designing system usable in designing a halftone screen having a square zero-shift halftone supercell, comprising: 
 at least one input device usable to input data defining a desired angle between a first frame of reference and a second frame of reference and a desired length for a first side of a pair of sides of a non-square supercell in the first frame of reference;    a first nominal side length determining circuit, routine or application operable to determine, based on the desired angle and the desired length of the first side, a first nominal side length of a second side of the pair of sides of the non-square supercell;    an actual side length selecting circuit, routine or application operable to select, based on the first nominal side length, an actual side length of the second side of the pair of sides of the non-square supercell; and    a center number determining circuit, routine or application.    
   
   
       10 . The square zero-shift supercell designing system of  claim 9 , wherein the first nominal side length determining circuit, routine or application determines a value for a nominal side length for a second side of the pair of sides of the non-square supercell in the first frame of reference.  
   
   
       11 . The square zero-shift supercell designing system of  claim 10 , further comprising a display device usable to display the determined nominal side length for the second side of the pair of sides of the non-square supercell, wherein the at least one input device is usable to input data defining an actual side length for the second side such that a number of centers within the square zero-shift halftone supercell is an integer.  
   
   
       12 . The square zero-shift supercell designing system of  claim 10 , wherein the actual side length selecting circuit, routine or application selects an actual side length for the second side based on the determined nominal side length of the second side such that a number of centers within the square zero-shift halftone supercell is an integer.  
   
   
       13 . The square zero-shift supercell designing system of  claim 10 , wherein the center number determining circuit, routine or application determines an integer number of centers within the square zero-shift halftone supercell based on the side lengths of the first and second sides of the non-square supercell.  
   
   
       14 . The square zero-shift supercell designing system of  claim 13 , further comprising: 
 an effective visual area estimating circuit, routine or application; and    a supercell area determining circuit, routine or application;    a second nominal side length determining circuit, routine or application;    an actual side length determining circuit, routine or application;    an effective visual area determining circuit, routine or application; and    an actual screen frequency determining circuit, routine or application.    
   
   
       15 . The square zero-shift supercell designing system of  claim 14 , wherein the effective visual area estimating circuit, routine or application estimates an effective visual area of a basic halftone cell of the halftone screen based on a resolution of a printer by which the halftone screen will be printed and a desired screen frequency.  
   
   
       16 . The square zero-shift supercell designing system of  claim 15 , wherein the supercell area determining circuit, routine or application determines a supercell area based on the estimated effective visual area and the determined integer number of centers of the square zero-shift halftone supercell, 
 the second nominal side length determining circuit, routine or application determines a nominal side length of the square zero-shift halftone supercell based on the determined supercell area,    the actual side length determining circuit, routine or application determines an actual integer-valued side length of the square zero-shift halftone supercell based on the determined nominal side length of the square zero-shift halftone supercell,    the effective visual area determining circuit, routine or application determines an actual effective visual area of the basic halftone cell based on the actual integer-valued side length of the square zero-shift halftone supercell, and    the actual screen frequency determining circuit, routine or application determines an actual screen frequency based on the actual effective visual area of the basic halftone cell and the printer resolution.    
   
   
       17 . The square zero-shift supercell designing system of  claim 13 , further comprising: 
 a supercell area determining circuit, routine or application;    a second nominal side length determining circuit, routine or application;    an actual side length determining circuit, routine or application;    an actual screen frequency determining circuit, routine or application.    
   
   
       18 . The square zero-shift supercell designing system of  claim 17 , wherein: 
 the at least one input device usable to input data defining an effective visual area of a basic halftone cell of the halftone screen; and    the supercell area determining circuit, routine or application determines a supercell area based on the defined effective visual area and the determined integer number of centers.    
   
   
       19 . The square zero-shift supercell designing system of  claim 18 , wherein the second nominal side length determining circuit, routine or application determines a nominal side length of the square zero-shift halftone supercell based on the determined supercell area, 
 the actual side length determining circuit, routine or application determines an actual integer-valued side length of the square zero-shift halftone supercell based on the determined nominal side length of the square zero-shift halftone supercell, and    the actual screen frequency determining circuit, routine or application determines an actual screen frequency based on the effective visual area of the basic halftone cell and a resolution of a printer by which the halftone screen will be printed.    
   
   
       20 . A square zero-shift supercell designing system, comprising: 
 an angle determining circuit, routine or application; and    a center number determining circuit, routine or application.    
   
   
       21 . The square zero-shift supercell designing system of  claim 20 , further comprising at least one input device usable to input data defining a desired length for a first side and a second side of a pair of sides of a non-square supercell.  
   
   
       22 . The square zero-shift supercell designing system of  claim 21 , wherein the angle determining circuit, routine or application determines an angle between a first frame of reference and a second frame of reference based on the input lengths for the first and second sides of the pair of sides of the non-square supercell.  
   
   
       23 . The square zero-shift supercell designing system of  claim 21 , wherein the center number determining circuit, routine or application determines an integer number of centers within the square zero-shift halftone supercell based on the side lengths of the first and second sides of the non-square supercell.  
   
   
       24 . The square zero-shift supercell designing system of  claim 23 , further comprising: 
 an effective visual area estimating circuit, routine or application;    a supercell area determining circuit, routine or application;    a nominal side length determining circuit, routine or application;    an actual side length determining circuit, routine or application;    an effective visual area determining circuit, routine or application; and    an actual screen frequency determining circuit, routine or application.    
   
   
       25 . The square zero-shift supercell designing system of  claim 24 , wherein the effective visual area estimating circuit, routine or application estimates an effective visual area of a basic halftone cell of the halftone screen based on a resolution of a printer by which the halftone screen will be printed and a desired screen frequency.  
   
   
       26 . The square zero-shift supercell designing system of  claim 25 , wherein the supercell area determining circuit, routine or application determines a supercell area based on the estimated effective visual area and the determined integer number of centers of the square zero-shift halftone supercell, 
 the nominal side length determining circuit, routine or application determines a nominal side length of the square zero-shift halftone supercell based on the determined supercell area,    the actual side length determining circuit, routine or application determines an actual integer-valued side length of the square zero-shift halftone supercell based on the determined nominal side length of the square zero-shift halftone supercell,    the effective visual area determining circuit, routine or application determines an actual effective visual area of the basic halftone cell based on the actual integer-valued side length of the square zero-shift halftone supercell, and    the actual screen frequency determining circuit, routine or application determines an actual screen frequency based on the actual effective visual area of the basic halftone cell and the printer resolution.    
   
   
       27 . The square zero-shift supercell designing system of  claim 23 , further comprising: 
 a supercell area determining circuit, routine or application;    a second nominal side length determining circuit, routine or application;    an actual side length determining circuit, routine or application; and    an actual screen frequency determining circuit, routine or application.    
   
   
       28 . The square zero-shift supercell designing system of  claim 27 , wherein: 
 the at least one input device usable to input data defining an effective visual area of a basic halftone cell of the halftone screen; and    the supercell area determining circuit, routine or application determines a supercell area based on the defined effective visual area and the determined integer number of centers.    
   
   
       29 . The square zero-shift supercell designing system of  claim 28 , wherein the second nominal side length determining circuit, routine or application determines a nominal side length of the square zero-shift halftone supercell based on the determined supercell area, 
 the actual side length determining circuit, routine or application determines an actual integer-valued side length of the square zero-shift halftone supercell based on the determined nominal side length of the square zero-shift halftone supercell, and    the actual screen frequency determining circuit, routine or application determines an actual screen frequency based on the effective visual area of the basic halftone cell and a resolution of a printer by which the halftone screen will be printed.