Fountain solution thickness measurement using an optical grating surface in a digital lithography printing system

Patent metadata

Field	Value
Publication number	US-11493328-B2
Application number	US-202017137473-A
Country	US
Kind code	B2
Filing date	Dec 30, 2020
Priority date	Dec 30, 2020
Publication date	Nov 8, 2022
Grant date	Nov 8, 2022

Abstract

According to aspects of the embodiments, there is provided a method of measuring the amount of fountain solution employed in a digital offset lithography printing system. Fountain solution thickness is measured using a diffractive optical element (DOE) configured with grating surfaces varying in a periodic fashion to hold an amount of fountain solution. When radiated with a light source the combination of the grating surface and the fountain solution therein reduces the scattering of the surface structure (“contrast”) that gives rise to a diffraction pattern. The diffractive optical element can be placed on the printing blanket of the lithography printing system or on a separate substrate.

First claim

What is claimed is:

1. A method to measure fountain solution thickness for variable data lithography printing comprising:
a) providing an optical gating-like surface varying in a periodic fashion, wherein diffraction intensity off the gating-like surface varies as a function of fountain solution thickness;
b) providing fountain solution onto the optical gating-like surface;
c) emitting light through the fountain solution to the gating-like surface using an optical system, while the light reflected from the gating-like surface is received by the optical system through the fountain solution; and
d) measuring a thickness of the fountain solution, based on intensity of the reflected light received by the optical system.

2. The method in accordance to claim 1 , wherein the gating-like surface includes a plurality of grooves on an outer surface to hold the fountain solution.

3. The method in accordance to claim 2 ,
wherein the step a) includes placing the optical gating-like surface on an imaging member having an arbitrarily reimageable imaging surface.

4. The method in accordance to claim 1 ,
wherein the step a) includes placing the optical gating-like surface on a substrate;
and the step b) includes applying a layer of the fountain solution to an imaging member having an arbitrarily reimageable imaging surface, and
transferring a portion of the applied fountain solution on the imaging member onto the substrate.

5. The method in accordance to claim 2 , wherein the plurality of grooves are spaced apart in a range of 200 nanometers to 2000 nanometers.

6. The method in accordance to claim 5 , wherein a groove has an average depth in a range of 10 nanometers to 200 nanometers.

7. The method in accordance to claim 4 , wherein the transferring is direct splitting contact transfer of the fountain solution on the imaging member to the optical gating-like surface on the substrate.

8. The method in accordance to claim 4 , wherein the transferring is evaporating the fountain solution on the imaging member and re-condensing on the optical gating-like surface on the substrate.

9. The method in accordance to claim 1 , the method further comprising:
using a donor roll to apply a layer of the fountain solution to an imaging member having an arbitrarily reimageable imaging surface.

10. The method in accordance to claim 9 , wherein the optical gating-like surface is placed on the donor roll to directly measure the fountain solution thickness before being transferred to the imaging member.

11. An ink-based digital printing system useful for ink printing, comprising:
a processor; and
a storage device coupled to the processor, wherein the storage device comprises instructions which, when executed by the processor, cause the ink-based digital printing system to measure fountain solution in variable data lithography printing by:
providing an optical gating-like surface varying in a periodic fashion, wherein diffraction intensity off the gating-like surface varies as a function of fountain solution thickness;
providing fountain solution onto the optical gating-like surface;
causing an optical system to emit light through the fountain solution to the gating-like surface, while the light reflected from the gating-like surface is received by the optical system through the fountain solution; and
measuring a thickness of the fountain solution, based on intensity of the reflected light received by the optical system.

12. The ink-based digital printing system of claim 11 , wherein the optical gating-like surface includes a plurality of grooves on an outer surface to hold the fountain solution.

13. The ink-based digital printing system in accordance to claim 12 , wherein the optical gating-like surface is located on an imaging member having an arbitrarily reimageable imaging surface.

14. The ink-based digital printing system in accordance to claim 11 , further comprising:
a fountain solution applicator configured to apply a layer of the fountain solution to an imaging member having an arbitrarily reimageable imaging surface;
the ink-based digital printing system transferring a portion of the fountain solution applied on the imaging member onto the substrate;
wherein the optical gating-like surface is located on a substrate.

15. The ink-based digital printing system in accordance to claim 12 , wherein the plurality of grooves are space apart in a range of 200 nanometers to 2000 nanometers.

16. The ink-based digital printing system in accordance to claim 15 , wherein a groove has an average depth in a range of 10 nanometers to 200 nanometers.

17. The ink-based digital printing system in accordance to claim 14 , wherein the transferring is direct splitting contact transfer of the fountain solution on the imaging member to the optical gating-like surface on the substrate.

18. The ink-based digital printing system in accordance to claim 14 , wherein the transferring is evaporating the fountain solution on the imaging member and re-condensing on the optical gating-like surface on the substrate.

19. The ink-based digital printing system in accordance to claim 11 , the ink-based digital printing system further comprising:
a donor roll to apply a layer of the fountain solution to an imaging member having an arbitrarily reimageable imaging surface.

20. The ink-based digital printing system in accordance to claim 19 , wherein the optical gating-like surface is located on the donor roll to directly measure the fountain solution thickness before being transferred to the imaging member.

Assignees

• Xerox Corp

Inventors

• Liu Chu-Heng
• Mcconville Paul J
• Lefevre Jason M
• Herrmann Douglas K
• Praharaj Seemit

Classifications

• B41P2227/70

  Forming the printing surface directly on the form cylinder · CPC title

• B41M1/06

  Lithographic printing · CPC title

• B41J2/0057

  where an intermediate transfer member receives the ink before transferring it on the printing material · CPC title

• G01B11/0675 Primary

  using interferometry · CPC title

• G01B11/0683 Primary

  measurement during deposition or removal of the layer · CPC title