Device and method for determining process status by tone value and color reproduction measurement
View Patent ↗The present invention concerns measures for the space-optimized determination of printing-related measured values. With the aid of a tone value and/or color gradient in a control patch and a suitable measuring device, it is possible to obtain, in a smaller amount of space, adequate or even detailed information about the printing process. Correcting values necessary for the automatic control of the printing operation can be determined on the basis of the information thus obtained, which can be also be continuously acquired due to the space-optimized tone value and/or color gradients.
1. A measuring unit for determining a printing-related measured value from at least one of a tone value gradient and a color gradient of a control patch printed on a printing medium, the measuring unit comprising:
a photosensitive sensor that can resolve a position in the control patch in at least one direction, said sensor producing image data;
a central processing unit for evaluating the image data from the photosensitive sensor;
a measuring device for determining a printing-related measured value at a measuring point in the control patch and determining a position of the measuring point; and
a memory for storing the measured values,
wherein the printing-related measured value and the position of the measuring point are determined during a printing operation of a printing press.
2. The measuring unit of claim 1 wherein the measuring device determines at least one limit of at least one of said tone value gradient and said color gradient of said control patch, and determines the position of the measuring point with reference to this limit.
3. The measuring unit of claim 1 wherein the measuring device determines a series of measured values as a function of the position of the measuring point, and fits a suitable function to said series of measured values.
4. The measuring unit of claim 3 wherein the measuring device determines an inflection point of the function and possibly a slope of the function at the inflection point.
5. The measuring unit of claim 3 wherein the measuring unit determines an ink acceptance behavior for each measured value of the series.
6. The measuring unit of claim 1 wherein
the photosensitive sensor can resolve a position in two directions; and
the measuring device determines a matrix of measured values in horizontal and vertical directions, and determines a mean value of the measured values in the vertical direction, so that a position-dependent series of averaged measured values is obtained.
7. The measuring unit of claim 1 wherein the measuring device compares at least one measured value with a predetermined limit and outputs suitable result signals and/or control signals.
8. The measuring unit of claim 1 wherein the measuring device performs densitometric measurements.
9. The measuring unit of claim 1 wherein the photosensitive sensor is one of a CCD surface chip and a CMOS surface chip.
10. The measuring unit of claim 1 wherein the measuring device comprises a computer program.
11. A method for determining a printing-related measured value of a printing press, the method comprising:
providing a printed medium having a control patch printed by the printing press with at least one of a tone value gradient and a color gradient;
determining a printing-related measured value from at least one of said tone value gradient and said color gradient of said control patch; and
determining the position in the control patch of a measuring point associated with said measured value,
wherein the steps of determining the measured value and determining the position are performed during a printing operation of a the printing press.
12. The method of claim 11 wherein the position of the measuring point is determined with respect to the position of the control patch.
13. The method of claim 11 comprising:
determining a series of measured values as a function of the position of the measuring point.
14. The method of claim 11 comprising:
determining a matrix of measured values in horizontal and vertical directions; and
determining a mean value of the measured values in the vertical direction, so that a position-dependent series of averaged measured values is obtained.
15. The method of claim 11 comprising determining said printing-related measured value from a control strip having gradient-like gradations consisting of a plurality of contiguous control patches.
16. The method of claim 11 comprising determining the measured value by image acquisition from one of a CCD surface chip and a CMOS surface chip.
17. The method of claim 11 further comprising computing an ICC profile from the printing-related measured value.
18. The method of claim 11 further comprising computing a tone value increase from the printing-related measured value.
19. The method of claim 11 further comprising computing a correcting variable for one of open-loop and closed-loop control from the printing-related measured value.
20. The method of claim 19 , further comprising controlling a fountain solution based at least in part on the correcting variable.
21. The method of claim 11 wherein the control patch is printed with a screen tone value gradient.