Color correction of dot linearities in multiple print engine system

• US 6,271,937 B1
• Filed: 01/12/1999
• Issued: 08/07/2001
• Est. Priority Date: 08/07/1995
• Status: Expired due to Fees

• Current Assignee: Electronics For Imaging Incorporated
• Original Assignee: T/R Systems, Inc. (Electronics For Imaging Incorporated)
• Inventors: Zuber, Peter A.
• Primary Examiner(s): ROGERS, SCOTT A
• Application Number:
  US09/229,242
• Time in Patent Office: 938 Days
• Field of Search: 358/1.9, 358/536, 358/534, 358/535, 358/521, 358/518, 358/504, 358/501, 358/456, 358/457, 358/458, 358/460, 358/406, 358/401, 358/298, 358/296, 382/274
• US Class Current: 358/1.9
• CPC Class Codes: G03G 15/5087 for receiving image data
• CPC Class Codes: G03G 2215/00021 Plural substantially independent image forming units in cooperation, e.g. for duplex, colour or high-speed simplex
• CPC Class Codes: G06F 2206/1514 Sub-job
• CPC Class Codes: G06F 3/1211 Improving printing performance
• CPC Class Codes: G06F 3/1215 achieving increased printing speed, i.e. reducing the time between printing start and printing end
• CPC Class Codes: G06F 3/1217 achieving reduced idle time at the output device or increased asset utilization
• CPC Class Codes: G06F 3/124 Parallel printing or parallel ripping
• CPC Class Codes: G06F 3/1241 Dividing a job according to job requirements, e.g. black/white and colour pages, covers and body of books, tabs
• CPC Class Codes: G06F 3/1281 Multi engine printer devices, e.g. one entity having multiple output engines
• CPC Class Codes: G06F 3/1282 High volume printer device
• CPC Class Codes: G06F 3/1285 Remote printer device, e.g. being remote from client or server
• CPC Class Codes: G06K 15/025 Simulating output on another printing arrangement, e.g. proof output matching two or more picture signal generators or two or more picture reproducers H04N1/6052
• CPC Class Codes: G06K 15/1859 involving data processing distributed amongst different data processing apparatus
• CPC Class Codes: H04N 1/52 Circuits or arrangements for halftone screening
• CPC Class Codes: H04N 1/6033 using test pattern analysis H04N1/6055 takes precedence

Abstract

A method for providing color correction to a color marking engine for halftone and contone images includes the step of first generating a test pattern. This test pattern has a plurality of discrete images disposed thereon with the discrete images having characteristics that are correlated with parameters of the print job. In one mode, they relate to halftone images that have differing densities of dots, each less than 100% density. The images are correlated to different bit values for the same densities such that the maximum density value for the pixel is offset for different images. A user then views the different images and determine which one is closest to a true gray and then selects the offset bit value for that image as the marking engine offset. This can then be applied to that particular marking engine. This can be utilized for a plurality of marking engines (651) with a single RIP operation (649 and 651). For dot linearization, the images will have different bit density values such that a curve can be made for actual verses requested density. A linearization curve can be defined for each of the plurality of the marking engines (651) in a versatile engine and then these linearization curves averaged. This averaged linearization curve is then applied to the RIP operation (649 and 651).

Claims

1. A method for generating dot linearization curves for multiple color marking engines having a single RIP associated therewith for generating a single RIPed halftone screen image for transfer to all of the marking engines configured as a virtual engine, comprising the steps of:

storing an average dot linearization curve for all of the marking engines; and

modifying the RIP operation of the RIP to provide an offset defined by the stored average dot linearization curve when RIPing an input job to offset the density level at each input level in accordance with the stored dot linearization curve.

2. The method of claim 1, wherein the linearization curve represents the average of the linearization curves for select ones of the marking engines.

3. The method of claim 2, wherein the linearization curve represents the average of all the linearization curves for all of the marking engines.

4. The method of claim 1, and further comprising the step of generating the stored averaged dot linearization curve by the steps of:

determining the linearization curve of all of the marking engines;

selecting the linearization curves for select ones of the marking engines in accordance with predetermined criteria for an averaging operation; and

averaging the select linearization curves to provide a single averaged linearization curve.

5. The method of claim 4, wherein the step of selecting comprises selecting the linearization curves from all of the marking engines.

6. The method of claim 4, wherein the step of determining comprises the steps of:

generating a test pattern of patches, each of the patches having differing known densities;

running the patch through the RIP operation and then through all of the marking engines to provide an output therefrom;

measuring the actual density of each of the patches on the provided output from each of the marking engines; and

generating a curve of actual density verses input density for each of the marking engines as the linearization curve for each of the marking engines.

7. The method of claim 4, wherein the step of selecting excludes marking engines having linearization values that are outside of predetermined bounds and further comprising the step of modifying the operation of the excluded marking engine independent of the RIP operation in addition to applying the step of modifying thereto.

8. The method of claim 1, wherein the step of modifying is applied selectively to a pre-defined job being operated on by the RIP operation.

9. A method for correcting dot linearities of a plurality of color marking engines configured as a single virtual printer utilizing a single RIP operation when printing a halftone image, comprising the steps of:

generating an average of dot linearization curves for the plurality of color marking engines;

storing the average dot linearization curve in association with the virtual printer; and

modifying the single RIP operation in accordance with the stored average dot linearization curve.

10. The method of claim 9, wherein the step of generating comprises:

determining the linearization curve of all of the marking engines;

selecting the linearization curves for select ones of the marking engines in accordance with predetermined criteria for an averaging operation; and

averaging the select linearization curves to provide a single averaged linearization curve.

11. The method of claim 9, wherein the step of generating comprises calculating offset values to be applied to each density value during the single RIP operation.

12. The method of claim 9, wherein the linearization curve represents the average of the linearization curves for select ones of the marking engines.

13. The method of claim 9, wherein the linearization curve represents the average of all the linearization curves for all of the marking engines.

14. The method of claim 9, wherein the step of determining comprises:

generating a test pattern of patches, each of the patches having differing known densities;

running the patch through the RIP operation and then through all of the marking engines to provide an output therefrom;

measuring the actual density of each of the patches on the provided output from each of the marking engines; and

generating a curve of actual density verses input density for each of the marking engines as the linearization curve for each of the marking engines.

15. The method of claim 10, wherein the step of selecting comprises selecting the linearization curves from all of the marking engines.

16. The method of claim 10, wherein the step of selecting comprises:

excluding the linearization curve of a marking engine having a linearization curve outside of predetermined bounds;

generating a parameter control value for the excluded marking engine corresponding to the variance of the linearization curve of the excluded marking engine from the predetermined bounds; and

modifying the linearization curve of the excluded marking engine according to the generated parameter control value.

17. The method of claim 10, wherein the step of selecting comprises:

excluding the linearization curve of a marking engine having a linearization curve outside of predetermined bounds; and

modifying the operation ofthe excluded marking engine independent of the RIP operation.

18. The method of claim 10, wherein the step of modifying comprises:

determining a parameter correction value for the linearization curve of the excluded marking engine; and

adjusting the excluded marking engine according to the parameter correction value corresponding to the excluded marking engine.

19. The method of claim 18, wherein the step of determining comprises determining a density correction value for the linearization curve of the excluded marking engine.

20. The method of claim 19, wherein the step of modifying comprises:

calculating a parameter correction value corresponding to the stored average dot linearization curve; and

correcting the single RIP operation according to the parameter correction value.

21. The method of claim 17, wherein the step of calculating comprises calculating a toner density correction percentage value.

22. The method of claim 9, wherein the step of modifying is applied selectively to a pre-defined job operated on by the RIP.