Halftone screens

1. A method comprising:

generating a halftone screen by arranging a plurality of amplitude-modulated dot clusters in correspondence with a grid, wherein each of the amplitude-modulated dot clusters comprises a plurality of frequency-modulated dots, wherein arranging the plurality of amplitude-modulated dot clusters comprises positioning each amplitude-modulated dot cluster in correspondence with an intersection point of a plurality of intersecting lines of the grid; and

printing a printed product using the generated halftone screen.

2. A method according to claim 1 , wherein arranging the plurality of amplitude-modulated dot clusters comprises determining a distribution of the plurality of frequency-modulated dots to be comprised in each amplitude-modulated dot cluster based on a target printing property.

3. A method according to claim 1 , wherein arranging the plurality of amplitude-modulated dot clusters comprises determining a number of frequency-modulated dots to be comprised in each amplitude-modulated dot cluster based on a target printing property.

4. A method according to claim 1 , wherein the plurality of amplitude-modulated dot clusters comprises a first amplitude-modulated dot cluster comprising a first number of frequency-modulated dots and a second amplitude-modulated dot cluster comprising a second, different number of frequency-modulated dots.

5. A method according to claim 1 , wherein arranging the plurality of amplitude-modulated dot clusters comprises determining an overlap characteristic of the plurality of frequency-modulated dots comprised in each amplitude-modulated dot cluster based on a target printing property.

6. A method according to claim 1 , wherein the plurality of amplitude-modulated dot clusters comprises an amplitude-modulated dot cluster having a plurality of overlapping frequency-modulated dots.

7. A method according to claim 1 , further comprising using the halftone screen to print an image that mimics a rosette appearance of analog printing.

8. A system to generate a halftone screen, the system comprising a halftone screen generation engine comprising a processor to generate a plurality of amplitude-modulated dot clusters, each of the amplitude-modulated dot clusters respectively comprising a plurality of frequency-modulated dots, the plurality of amplitude-modulated dot clusters being distributed in accordance with a grid and wherein the amplitude-modulated dot clusters contain overlapping frequency-modulated dots.

9. A system according to claim, 8 wherein a first amplitude-modulated dot cluster in the plurality of amplitude-modulated dot clusters has a first dot cluster size and a second amplitude-modulated dot cluster in the plurality of amplitude-modulated dot clusters has a second, different dot cluster size.

10. A system according to claim 8 , wherein the plurality of amplitude-modulated dot clusters comprises a first amplitude-modulated dot cluster, a second amplitude-modulated dot cluster and a third amplitude-modulated dot cluster, and wherein a separation of the first amplitude-modulated dot cluster relative to the second amplitude-modulated dot cluster is the same as a separation of the first amplitude-modulated dot cluster relative to the third amplitude-modulated dot cluster.

11. A system according to claim 10 , wherein the plurality of amplitude-modulated dot clusters comprises a fourth amplitude-modulated dot cluster, and wherein a separation of the first amplitude-modulated dot cluster relative to the fourth amplitude-modulated dot cluster is different from the separation of the first amplitude-modulated dot cluster relative to the second amplitude-modulated dot cluster and the separation of the first amplitude-modulated dot cluster relative to the third amplitude-modulated dot cluster.

12. A system according to claim 10 , wherein the plurality of amplitude-modulated dot clusters comprises a fourth amplitude-modulated dot cluster, wherein a separation of the fourth amplitude-modulated dot cluster relative to the second amplitude-modulated dot cluster is the same as the separation of the first amplitude-modulated dot cluster relative to the second amplitude-modulated dot cluster, and wherein a separation of the fourth amplitude-modulated dot cluster relative to the third amplitude-modulated dot cluster is the same as the separation of the first amplitude-modulated dot cluster relative to the third amplitude-modulated dot cluster.

13. A printer comprising a system according to claim 8 .

14. A method of supplementing a run of flexographically printed boards with a number of additional matching boards printed with a digital press, the method comprising:

with the digital press, matching boards produced by the flexographic printing, by generating a halftone screen comprising a plurality of amplitude-modulated dot clusters based on the flexographic printing, each amplitude-modulated dot cluster of the halftone screen being arranged in accordance with a grid and comprising a plurality of frequency-modulated dots produced by the digital press; and

with the digital press, printing the number of additional matching boards using the halftone screen.

15. A method according to claim 3 , wherein the target printing property is a target gray level of each amplitude-modulated dot cluster.

16. A method according to claim 3 , wherein the target printing property is a target color intensity of each amplitude-modulated dot cluster.

17. A method according to claim 3 , wherein the target printing property is a target balance between printing fluid efficiency and minimizing the effect of malfunctioning nozzles when printing.

18. A method according to claim 1 , wherein a separation between a first amplitude-modulated dot cluster and a second amplitude-modulated dot cluster is the same as between the first amplitude-modulated dot cluster and a third amplitude-modulated dot cluster as measured from respective centers of the amplitude-modulated dot clusters or a shortest distance between respective boundaries of the amplitude-modulated dot clusters.

19. The system of claim 9 , wherein the halftone screen generation engine further comprises:

an AM halftoning engine comprising an amplitude-modulated (AM) stretch and linearization look up table (LUT);

an FM halftoning engine comprising a frequency-modulated (FM) stretch and linearization look up table (LUT);

and

a logical AND gate receiving input from the AM halftoning engine and the FM halftoning engine, wherein the logical AND gate regulates the output of the halftone screen generation engine.