Method for printing image planes on substrate

1. A method for printing a plurality of documents each having a plurality of image planes on a substrate, the method comprising:

(a) providing a plurality of print heads for depositing material on the substrate as the substrate moves along a transport path, each printhead printing an associated image plane and being located at an associated position along the transport path;

(b) providing a first sensor in a predetermined position along a transport path downstream relative to predetermined positions of the plurality of print heads;

(c) providing an indication of position of the substrate along the transport path;

(d) providing a plurality of cue marks at predetermined positions or intervals on the substrate, each cue mark being detected by the first sensor as the cue mark moves along the transport path past the first sensor;

(e) for each document initiating the printing of an image plane printed by one of the plurality of print heads located along the transport path upstream of the first sensor following an appropriate pre-defined cue delay from the detection of one of the plurality of cue marks on the substrate by the first sensor.

2. The method as in claim 1 , wherein providing the plurality of cue marks includes printing one or more leading cue marks sufficient to span a distance between the first sensor and the at least one upstream print head.

3. The method as in claim 2 , wherein the indication of position is provided by an encoder for determining position of the substrate.

4. The method as in claim 1 , wherein the indication of position is provided by an encoder for determining position of the substrate.

5. The method as in claim 1 further comprising providing a second sensor upstream of the at least one print head for producing second cue signals that correspond to the detection of the cue marks at the second sensor.

6. The method as in claim 5 , wherein initiating printing of the image plane of the document is adjusted based on a determination of a deviation between the image plane position based on the pre-defined cue delay and the detection of the position of the cue marks on the substrate by the first sensor and a second image plane position based on a different pre-defined cue delay and cue signals of the second sensor.

7. The method as in claim 6 , wherein the adjustment based on the deviation of image plane position is determined by interpolation.

8. The method as in claim 6 , wherein interpolation is determined by relative distance between each of the two cue sensors and the print head that prints the image plane.

9. The method as in claim 6 , wherein interpolation is determined by image content between each of the two cue sensors and the print head that prints the image plane.

10. The method of claim 6 , wherein the printing a plurality of image planes on a substrate comprises the printing of multiple copies of a sequence of documents; and wherein the interpolation varies from one document to the next document within a copy of the sequence of documents based on the registration errors measured during the printing of a previous copy of the sequence of documents for the corresponding documents in the sequence of documents.

11. The method as in claim 1 further comprising a system for measuring registration of the image planes printed by the plurality of print heads.

12. The method of claim 1 , wherein the one of the plurality of print heads is located along the transport path downstream of the first sensor, and for each document the initiating of the printing of an image plane by the downstream print head following a second pre-defined cue delay from the detection of a cue mark by the first sensor.

13. The method claim 12 , wherein following the detection of a cue mark by the first sensor, the image plane printed by the print head upstream of the first sensor and the image plane printed by the print head downstream of the first sensor are image planes of different documents.