Single-color screen patterns for copy protection
A verifiable/copy-protected document features a combination of nearly identical line-screen patterns for embedding latent images within visually integrated settings. The latent images can be detected for purposes of verification with a matching viewer but are indistinguishable from their visually integrated settings under ordinary viewing conditions. The line-screen patterns, which can be incorporated into document artwork, are printed at certain combinations of line frequencies and print densities so that the line-screen patterns digitally reproduce as a largely undifferentiated solid tint.
1. A document comprising:
a latent image embedded within a visually integrated setting of the document,
the latent image and the visually integrated setting being formed by patterns of relatively oriented print elements, and
the print element patterns of both the latent image and the visually integrated setting being arranged with common colors, common print densities, and common line frequencies, the common print densities being at least 20 percent and the common line frequencies being at least 175 lines per inch.
2. The document of claim 1 in which the common print densities are within approximately 10 percent of each other and the common line frequencies are within approximately 20 percent of each other.
3. The document of claim 1 in which the common print densities are within approximately 5 percent of each other and the common line frequencies are within approximately 10 percent of each other.
4. The document of claim 1 in which the print element patterns of the latent image and the visually integrated setting are patterns of spaced lines having angular orientations that differ by at least 5 degrees.
5. The document of claim 1 in which the print element patterns of the latent image and the visually integrated setting are patterns of spaced lines having angular orientations that differ by at least 30 degrees.
6. The document of claim 1 in which the latent image is at least partially indistinguishable from the visually integrated setting to the unaided eye.
7. The document of claim 6 in which the print element patterns of the latent image and the visually integrated setting are patterns of spaced lines that differ in orientation enough that the latent image is distinguishable from the visually integrated setting via differing moiré patterns generated by an overlaid visual aid having a line frequency sufficiently close to the common line frequency of at least one of the latent image or the visually integrated setting such that the latent image is distinguishable from the visually integrated setting while the visual aid is aligned with the angular orientation of at least one of the patterns of spaced lines of either the latent image or the visually integrated setting.
8. The document of claim 7 in which the print element patterns of the latent image and the visually integrated setting digitally reproduce in an altered form so that the latent image is not distinguishable from the visually integrated setting with the same visual aid.
9. The document of claim 1 in which both the print element patterns of the latent image and the visually integrated setting comprise line-screen patterns, and wherein the line-screen patterns reproduce in an altered form on a digitally reproduced copy of the document such that the line-screen patterns of the latent image or the visually integrated setting are at least partially replaced, in the digitally reproduced copy, by print elements which blur differences between the latent image and the visually integrated setting.
10. The document of claim 9 in which the line-screen patterns of the latent image and the visually integrated setting are less distinguishable on the digitally reproduced copy of the document, thereby preventing the latent image from being distinguishable from the visually integrated setting in the digitally reproduced copy.
11. The document of claim 10 in which the digitally reproduced copy of the latent image and the visually integrated setting includes print elements that fill in spaces not occupied by the line-screen patterns of the latent image and the visually integrated setting.
12. The document of claim 1 in which the print element patterns of both the latent image and the visually integrated setting are printed in a single primary subtractive color.
13. The document of claim 1 in which the common line frequencies are between 175 lines per inch and 200 lines per inch.
14. The document of claim 13 in which the common print densities are between 20 percent and 50 percent.
15. A copy-protection system for verifiable documents comprising:
a document containing a verifiable security feature as a latent image within a visually integrated setting, the latent image and the visually integrated setting each comprising an array of print elements arranged in a pattern of spaced lines, the patterns of the latent image and the visually integrated setting configured with common colors, common print densities, and common line frequencies,
the latent image and the visually integrated setting being substantially indistinguishable to the unaided eye but being visually contrastable for verification through a visual aid configured to provide a differing visual effect between the latent image and the visually integrated when overlaid on the document and aligned with at least one of the patterns of spaced lines in the array of print elements of the latent image or the visually integrated setting, and
the print element patterns of the latent image and the visually integrated setting being arranged so that the latent image and the visually integrated setting digitally reproduce in an altered graphic form in which the latent image remains substantially indistinguishable from the visually integrated setting to the unaided eye and is not similarly contrastable through the visual aid as originally aligned with respect to the latent image and visually integrated setting of the document.
16. The system of claim 15 in which the print elements patterns of the latent image and the visually integrated setting are arranged so as to render the latent image and the visually integrated setting substantially indistinguishable to the unaided eye.
17. The system of claim 16 in which the common print densities are within approximately 10 percent of each other and the common line frequencies are within approximately 20 percent of each other.
18. The system of claim 16 in which the common print densities are within approximately 5 percent of each other and the common line frequencies are within approximately 10 percent of each other.
19. The system of claim 15 in which the patterns of spaced lines in the print element patterns of the latent image and the visually integrated setting sufficiently differ from one another in angular orientation enough that the latent image is visually contrasted with respect to the visually integrated setting through differing moiré patterns generated by an overlaid visual aid aligned with at least one of the patterns of spaced lines in the print element patterns of the latent image or the visually integrated setting.
20. The system of claim 19 in which the angular orientations of the patterns of spaced lines in the print element patterns of the latent image and the visually integrated setting differ by at least 5 degrees.
21. The system of claim 19 in which the angular orientations of the patterns of spaced lines in the print element patterns of the latent image and the visually integrated setting differ by at least 30 degrees.
22. The system of claim 15 in which the print element patterns of both the latent image and the visually integrated setting are arranged with the common print densities being at least 20 percent and the common line frequencies being at least 175 lines per inch.
23. The system of claim 22 in which the common line frequencies are between 175 lines per inch and 200 lines per inch.
24. The system of claim 23 in which the common print densities are between 20 percent and 50 percent.
25. A verifiable document comprising:
a latent image embedded within a visually integrated setting of the verifiable document,
the latent image and the visually integrated setting being formed by patterns of commonly oriented print elements,
the print element patterns of the latent image and the visually integrated setting being arranged with common colors, common print densities, and differing line frequencies, the common print densities being at least 20 percent and the differing line frequencies each being at least 175 lines per inch, and
the line frequencies of the print element patterns of the latent image and the visually integrated setting differing by between 5 percent and 20 percent of each other.
26. The document of claim 25 in which the latent image is at least partially indistinguishable from the visually integrated setting to the unaided eye.
27. The document of claim 26 in which the line frequencies of the print element patterns of the latent image and the visually integrated setting differ by enough that the latent image is distinguishable from the visually integrated setting via differing moiré patterns generated by an overlaid visual aid having a line frequency sufficiently close to the line frequency of the print element pattern of one of the latent image or the visually integrated setting such that the latent image is distinguishable from the visually integrated setting while the visual aid is aligned with angular orientations of the commonly oriented print element patterns.
28. The document of claim 27 in which the print-elements element patterns of the latent image and the visually integrated setting digitally reproduce in an altered form so that the latent image is not similarly distinguishable from the visually integrated setting with the same visual aid.
29. The document of claim 25 in which the differing line frequencies of the print element patterns of both the latent image and the visually integrated setting are between 175 lines per inch and 200 lines per inch and the common print densities are between 20 percent and 50 percent.
30. The document of claim 25 in which the difference between the line frequencies of the print element patterns of the latent image and the visually integrated setting is enough that the latent image is visually contrasted from the visually integrated setting via differing moiré patterns generated by an overlaid visual aid aligned with the commonly oriented print element patterns of the latent image and the visually integrated setting.
31. The document of claim 25 in which the print element patterns of both the latent image and the visually integrated setting comprise line-screen patterns and wherein the line-screen patterns reproduce in an altered form on a digitally reproduced copy of the document such that the line-screen patterns of the latent image or the visually integrated setting are at least partially replaced, in the digitally reproduced copy, by print elements which blur the differences between the latent image and the visually integrated setting.
32. The document of claim 31 in which the line-screen patterns of the latent image and the visually integrated setting are less distinguishable on the digitally reproduced copy of the document, thereby preventing the latent image from being distinguishable from the visually integrated setting in the digitally reproduced copy.
33. The document of claim 31 in which the digitally reproduced copy of the latent image and the visually integrated setting includes print elements that fill in spaces not occupied by the line-screen patterns of the latent image and the visually integrated setting.
34. The document of claim 25 in which the print element patterns of the latent image and the visually integrated setting are arranged as patterns of spaced lines.
35. The document of claim 25 in which the print element patterns of the latent image and the visually integrated setting are arranged as systematically spaced lines that include continuous lines.
36. The document of claim 25 in which the common colors of the print element patterns are matching colors and the common print densities of the print element patterns are matching print densities.
37. The system of claim 15 in which the print element patterns of both the latent image and the visually integrated setting comprise line-screen patterns, and wherein the line-screen patterns reproduce in an altered form on a digitally reproduced copy of the document such that the line-screen patterns of the latent image or the visually integrated setting are at least partially replaced, in the digitally reproduced copy, by print elements which blur the differences between the latent image and the visually integrated setting.
38. The system of claim 37 in which the line-screen patterns of the latent image and the visually integrated setting are less distinguishable on the digitally reproduced copy of the document, thereby preventing the latent image from being distinguishable from the visually integrated setting in the digitally reproduced copy.
39. The system of claim 37 in which the digitally reproduced copy of the latent image and the visually integrated setting includes print elements that fill in spaces not occupied by the line-screen patterns of the latent image and the visually integrated setting.
40. The system of claim 19 in which the angular orientations of the patterns of spaced lines in the print element patterns of the latent image and the visually integrated setting differ by approximately 45 degrees.
41. The system of claim 15 in which patterns of spaced lines in the print element patterns of the latent image and the visually integrated setting are arranged as systematically spaced lines that include continuous lines.
42. The system of claim 15 in which the common line frequencies of the patterns of the latent image and the visually integrated setting are matching line frequencies.
43. The system of claim 15 in which the common colors of the patterns of the latent image and the visually integrated setting are matching colors, the common print densities of the patterns of the latent image and the visually integrated setting are matching print densities, and the common line frequencies of the patterns of the latent image and the visually integrated setting are matching line frequencies.
44. The document of claim 7 in which the print element patterns of the latent image and the visually integrated setting are patterns of spaced lines having angular orientations that differ by approximately 45 degrees.
45. The document of claim 1 in which the print element patterns of the latent image and the visually integrated setting are arranged as patterns of spaced lines.
46. The document of claim 1 in which the print element patterns of the latent image and the visually integrated setting are arranged as systematically spaced lines that include continuous lines.
47. The document of claim 46 in which the common line frequencies of the print element patterns are matching line frequencies.
48. The document of claim 1 in which the common line frequencies of the print element patterns are matching line frequencies.
49. The document of claim 1 in which the common colors of the print element patterns are matching colors, the common print densities of the print element patterns are matching print densities, and the common line frequencies of the print element patterns are matching line frequencies.
50. A verifiable document comprising:
a latent image including a first line-screen pattern formed by an array of print elements arranged as systematically spaced lines having a first color, a first print density, a first angular orientation, and a first line frequency;
a visually integrated setting surrounding the latent image, the visually integrated setting including a second line-screen pattern formed by an array of print elements arranged as systematically spaced lines having a second color, a second print density, a second angular orientation, and a second line frequency;
wherein the first color matches the second color and the first print density matches the second print density, such that the latent image is substantially indistinguishable from the visually integrated setting to the unaided eye;
wherein at least one of a difference between the first and second angular orientations or a difference between the first and second line frequencies is sufficient to allow the latent image to be distinguishable from the visually integrated setting via a visual aid having a line frequency configured to generate differing interference patterns for the latent image and the visually integrated setting while the visual aid is aligned with at least one of the first or second line-screen patterns; and
wherein the document is further configured such that a digitally reproduced copy of the latent image and the visually integrated setting includes print elements that fill in spaces not occupied by the first and second line-screen patterns so as to blur the differences between the latent image and the visually integrated setting so that the latent image is not similarly distinguishable from the visually integrated setting with the same visual aid.
51. The verifiable document of claim 50 , wherein the first line frequency matches the second line frequency and wherein the first angular orientation and the second angular orientation differ by at least 5 degrees.
52. The verifiable document of claim 51 , wherein the first angular orientation and the second angular orientation differ by at least 30 degrees.
53. The verifiable document of claim 50 , wherein the first angular orientation matches the second angular orientation such that the first and second line-screen patterns are commonly aligned, and wherein the first line frequency and the second line frequency differ by at least 5 percent.
54. The verifiable document of claim 53 , wherein the first line frequency and the second line frequency differ by between 5 percent and 20 percent.
55. The verifiable document of claim 50 , wherein the first line frequency and the second line frequency are each at least 175 lines per inch, and wherein the first print density and the second print density are each at least 20 percent.
56. The verifiable document of claim 55 , wherein the first line frequency and the second line frequency are each between 175 lines per inch and 200 lines per inch, and wherein the first print density and the second print density are each between 20 percent and 50 percent.
57. The verifiable document of claim 50 , wherein the first line frequency and the second line frequency are each less than 175 lines per inch, and wherein the first print density and the second print density are each at least 50 percent.
58. The verifiable document of claim 50 , wherein the array of print elements arranged as systematically spaced lines of the first and second line-screen patterns include continuous lines.