Method for controlling a print engine and digital printer

Patent metadata

Field	Value
Publication number	US-2016342107-A1
Application number	US-201415114802-A
Country	US
Kind code	A1
Filing date	Jan 31, 2014
Priority date	Jan 31, 2014
Publication date	Nov 24, 2016
Grant date	—

Abstract

A method of controlling a print engine, the method comprising: printing a first test image including a number of scans of printing components at a first setting of the array of printing components; printing at least a second test image by a number of scans of the printing components at a modified setting of the array of printing components, the modified setting being different from the first setting, wherein the modified setting provides a modified setting for each one of the printing components which is varied according to the position of the respective printing component in the array; optically scanning the printed test images and determining the distinctiveness of a scan band within the printed test images for each one of the test images; and deriving an optimum setting of the array of printing components from a comparison of the determined distinctiveness.

First claim

1 . A method of controlling a print engine, the method comprising:
printing a first test image including a number of scans of printing components at a first setting of the army of printing components; printing at least a second test image by a number of scans of the printing components at a modified setting of the array of printing components, the modified setting being different from the first setting, wherein the modified setting provides a modified setting for each one of the printing components which is varied according to the position of the respective printing component in the array; optically scanning the printed test images and determining the distinctiveness of a scan band within the printed test images for each one of the test images; and deriving an optimum setting of the array of printing components from a comparison of the determined distinctiveness.

2 . The method of claim 1 wherein the first setting provides a predetermined nominal power to each one of the printing components, and each modified setting provides a modified power to each one of the printing components which is described by a polynomial term as a function of the position of the respective printing component in the array.

3 . The method of claim 2 wherein the polynomial term comprises a linear term or a parabolic term or a combined term including a linear component and a parabolic component.

4 . The method of claim 3 , further comprising:
printing k test images, each test image including n scans per image, wherein a different modified setting is used for each of the k test images; wherein the linear term comprises:

power
′



(
i
)

=

power


(
i
)

·

(

1
+

slope
k

·

i
-
a

b

)

wherein
i=1 . . . L, for an array of L printing components,
power(i) is the predetermined nominal power of the ith printing component in the array off printing components,
power′(i) is the modified power of the ith printing component in the array of L printing components,
slope k is a sealing factor used for an kth test image, and
a and b are parameters for linearly distributing the modified power over the array of L printing components; and
wherein the polynomial term comprises:
wherein

power
″



(
i
)

=

power
′



(
i
)

·

(

1
+

parabola
k

·

(

i
-
a

b

)

2

)

power″(i) is a further modified power of the ith printing component in the array of L printing components, and
parabolas k is a sealing factor used for the kth test image,

5 . The method of claim 4 wherein a=(L+1)/2 and b=2a.

6 . The method of claim 4 wherein
k is an integer number in the range of 2 to 20, or 4 to 12, or k=4; and
n is an integer number k the range of 2 to 50, or 5 to 50, or n is about 10, or n=9.

7 . The method of claim 1 wherein
determining the distinctiveness of a scan band within the printed test images comprises: optically scanning each test image, and for each test image, determining an amplitude of the test image at a scan band frequency, and
deriving an optimum setting of the array of printing components comprises: comparing the determined amplitudes of the test images and selecting a setting which resulted in an test image having a low amplitude when compared, to other test images.

8 . The method of claim 7 wherein the amplitude is determined by Fourier analysis or correlation.

9 . The method of claim 8 wherein the amplitude corresponds to a pixel intensity value of a printed test image.

10 . The method of claim 8 wherein the printing components are laser elements and the amplitude is determined at a scan band frequency of 1/(L·laser_dot_diameter), wherein L is the number of laser elements in the array.

11 . A method of controlling a an array of L laser elements in a digital printer, the laser elements writing scan by scan a digital image, wherein each scan is composed of a number of laser beams generated by the laser elements, the method comprising: printing a first test image including a number of scans of the laser elements at a first power setting of the array of laser elements;
printing further test images, each further test image including a number of scans of the printing components at a modified power setting of the array of laser elements, each modified power setting being different from a preceding power setting, wherein the modified power setting provides a modified control power for each one of the laser elements which is varied according to the position of the respective laser element in the array; determining the amplitude of a scan band within the printed test images for each one of the test images by analyzing the test image at a scan band frequency; and selecting the test image exhibiting the lowest amplitude for deriving an optimum power setting of the army of laser elements.

12 . The method of claim 11 wherein
determining the amplitude of a scan band within the printed test images comprises:
optically scanning each test image using a in-line scanner of the printer, the in-line scanner having a resolution lower than necessary for directly measuring the laser element output power.

13 . The method of claim 11 wherein the first power setting provides a predetermined nominal

Assignees

• Hewlett Packard Indigo Bv

Inventors

• Yedid Am Tsafrir
• Vladomirski Haim
• Blinchuk Pavel

Classifications

• G03G15/043 Primary

  with means for controlling illumination or exposure (G03G15/041 takes precedence) · CPC title

• G03G15/04072

  by laser · CPC title

• B41J2/473 Primary

  using multiple light beams, wavelengths or colours · CPC title

• G06K15/027

  Test patterns and calibration (arrangements for controlling or analysing printing mechanisms of typewriters or selective printing units B41J29/393 takes precedence; colour correction using test pattern analysis in general H04N1/6033) · CPC title

• H04N1/40037

  the reproducing element being a laser · CPC title