Printing methods and apparatus for mutually interstitial printing and optional interlacing

1. Dot matrix printing method for printing an image on a printing medium using a printing head having an array of equally spaced marking elements for marking dots on the printing medium while performing fast scan and slow scan movements relative to the printing medium, the method comprising,

printing the image as at least one set of monochromatic mutually interstitially printed sub-images wherein

adjacent dots on one scan line extending in the fast scan direction are formed by the different marking element, and

at least one of the number of sub-images and a sequence in which the printing of the sub-images is performed is settable.

2. The method according to claim 1 , wherein the number of sub-images and the sequence of printing of the sub-images are independently settable.

3. The method according to claim 1 wherein the marking elements are spaced apart by a distance “x” in a slow scan direction (X), the method further comprising the step of:

printing on the printing medium a matrix of dots using mutually interstitial printing steps and interlacing steps, wherein the distance “x” is substantially an integer multiple of the substantially equal distance between lines extending in the fast scan direction (Y).

4. The method according to claim 3 , wherein the number of interlacing steps is settable.

5. The method according to claim 3 , comprising printing the image as N sub-images, N being the number of colors used for printing multiplied by the number of mutually interstitial printing steps and multiplied by the number of interlacing steps (N=C*P*I).

6. The method according to claim 5 , wherein each mutually interstitial printing step is a pass of the printing head.

7. The method according to claim 5 , wherein each interlacing step is a pass of the printing head.

8. The method according to claim 3 , wherein the marking element array has two rows and in each mutually interstitial printing step one of the rows is selected to print during an interlacing step.

9. The method according to claim 3 , wherein the image has a resolution R 1 , and each sub-image has a resolution R 2 being equal to R 1 divided by the number of interlacing steps.

10. The method according to claim 3 , further comprising the-step of: moving the printing head relative to the printing medium successively in the fast scan direction (Y) for writing a plurality of contiguous swaths of each of the 1 st to N th sub-image, the printing medium being transported relative to the printing head over a distance in the slow scan direction (X) equal to the active nozzle length each time a swath of a sub-image has been written; boundaries between swaths of at least two sub-images not falling at the same location on the printing medium.

11. The method according to claim 10 , wherein all of the boundaries between swaths of the sub-images fall on different locations on the printing medium.

12. A computer program product for executing the method as claimed in claim 1 when executed on a computing device associated with a printing head.

13. A machine readable data storage device storing the computer program product of claim 12 .

14. Transmission of the computer product of claim 12 over a local or wide area telecommunications network.

15. An apparatus for dot matrix printing an image on a printing medium, comprising:

a printing head;

an array of equally spaced marking elements on the printing head, the marking elements being spaced apart by a distance “x” in a slow scan direction (X);

means for generating a first relative linear movement between the printing head and the printing medium in a fast scan direction (Y) perpendicular to the slow scan direction (X),

the apparatus being adapted to print the image as at least one set of monochromatic mutually interstitially printed sub-images wherein

adjacent dots on one scan line extending in the fast scan direction are formed by different marking elements, and

at least one of the number of sub-images and a sequence in which the printing of the sub-images is performed is settable.

16. The apparatus according to claim 15 , wherein the apparatus is adapted so that each bf the number of sub-images and the sequence of the sub-images is individually settable.

17. The apparatus according to claim 15 wherein the apparatus is adapted to print on the printing medium a matrix of dots using mutually interstitial printing steps and interlacing steps.

18. The apparatus according to claim 17 , wherein the apparatus is adapted to print the image as N sub-images, N being the number of colors used for printing multiplied by the number of mutually interstitial printing steps and multiplied by the number of interlacing steps (N=C*P*I).

19. The apparatus according to claim 18 , further comprising means for moving the printing head relative to the printing medium successively in the fast scan direction (Y) for writing a plurality of contiguous swaths of each of the 1 st to Nth sub-image, the printing medium being transported relative to the printing head over a distance in the slow scan direction (X) equal to the active nozzle length each time a swath of a sub-image has been written; boundaries between swaths of at least two sub-images not falling at the same location on tha printing medium.

20. The apparatus according to claim 19 , wherein the apparatus is adapted so that all of the boundaries between swaths of the sub-images fall on different locations on the printing medium.

21. The apparatus according to claim 17 , wherein the apparatus is adapted so that the number of interlacing steps is settable.

22. The apparatus according to claim 15 , wherein the marking elements are ink projecting nozzles.

23. An ink jet printing including an apparatus according to claim 15 .