EP0142470B1
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EP
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Method and device for judging the printing quality of a printed object, preferably printed by an offset printing machine, and offset printing machine provided with such a device
Assignee: Gretag AG
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Filing: 1984-10-29
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Granted: 1988-01-07
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Expires: 2004-10-29
Abstract
Abstract Printed products and their respective corresponding printing plates are divided into a plurality of image elements. For each image element the surface coverage is determined by photoelectric measurements; a reference reflectance value is then calculated from these measurements, taking into consideration such parameters as the printing characteristic. These reference reflectance values are compared with the actual reflectance values measured on the printed products and the results of the comparison are evaluated to form a quality measure and to calculate control values for the ink feed devices of the printing machine. In this manner, the use of special color measuring strips may be eliminated.
Inventors
- 👤 Hans Ott
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-24 22:59
CPC Classifications
B; B41; B41F; B41F33/00; B41F33/0027; B41F33/0036
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
296 words
Process for evaluating the printing quality of a printed product produced on a printing machine, wherein the printed product and a reference are each divided into image elements (E) and photoelectrically measured by image element, wherein for each image element (E) of the printed product and for each color a corresponding reference reflectance value (R s ) and an actual reflectance value (R;) are determined by measuring techniques and the reference reflectance and actual reflectance values of corresponding image elements are compared with each other, and wherein a quality measure (Q) is determined from said comparisons, characterized in that the determination of the reference reflectance and actual reflectance (R s , R i ) by measuring techniques is carried out densitometrically for each printing color, that to every image element (E) of the printed product as a function of the reference and actual reflectance values for said element a perception weighting factor (He) expressing the relationship between the sensitometric and technically measured color deviations and/or as a function of its surface coverage and color a full tone factor (G e ) describing the effect of the full tone density on reflectance are assigned and that the differences (A e ) between the reference reflectance values (R s ) and the corresponding actual reflectance values (R;) are weighted with the perception weighting factor (He) and the full tone factor (G e ), in order to obtain on the one hand a conversion into a sensitometric color coordinate system and on the other, to determine full tone density deviations from the reference potentially also without the use of a color measuring strip, and that the quality measure (Q) is formed by the summation of the differences weighted in this manner over at least part of the image elements.
Claim 2
Dependent Claim
296 words
Process for evaluating the printing quality of a printed product produced on a printing machine, wherein the printed product and a reference are each divided into image elements (E) and photoelectrically measured by image element, wherein for each image element (E) of the printed product and for each color a corresponding reference reflectance value (R s ) and an actual reflectance value (R;) are determined by measuring techniques and the reference reflectance and actual reflectance values of corresponding image elements are compared with each other, and wherein a quality measure (Q) is determined from said comparisons, characterized in that the determination of the reference reflectance and actual reflectance (R s , R i ) by measuring techniques is carried out densitometrically for each printing color, that to every image element (E) of the printed product as a function of the reference and actual reflectance values for said element a perception weighting factor (He) expressing the relationship between the sensitometric and technically measured color deviations and/or as a function of its surface coverage and color a full tone factor (G e ) describing the effect of the full tone density on reflectance are assigned and that the differences (A e ) between the reference reflectance values (R s ) and the corresponding actual reflectance values (R;) are weighted with the perception weighting factor (He) and the full tone factor (G e ), in order to obtain on the one hand a conversion into a sensitometric color coordinate system and on the other, to determine full tone density deviations from the reference potentially also without the use of a color measuring strip, and that the quality measure (Q) is formed by the summation of the differences weighted in this manner over at least part of the image elements.
Claim 3
Dependent Claim
81 words
Process according to claim 1, characterized in that as the reference for the individual colors the corresponding printing plate (P) or the photographic master upon which it is based, are used, that the surface coverage is determined for every image element of said reference and that the reference reflectance value (R s ) is calculated for every image element (E) and each printed color of the printed product from the determined surface coverage of the corresponding image element of the reference.
Claim 4
Dependent Claim
21 words
Process according to claim 1, characterized in that a printed product (OKB) found to be satisfactory is used as the reference.
Claim 5
Dependent Claim
57 words
Process according to one of claims 1 to 3, characterized in that the determination of the reference reflectance values (R s ) for the image elements (E) of the reference (P) is carried out with a higher resolution than the determination of the actual reflectance values (R;) for the image elements (E) of the printed product (D).
Claim 6
Dependent Claim
20 words
Process according to claim 4, characterized in that the image elements (E) of the printed product (D) are measured integrally.
Claim 7
Dependent Claim
33 words
Process according to claim 4 or 5, characterized in that the resolution in the measuring of the reference (P) is at least 10 times higher than in the case of the printed product.
Claim 8
Dependent Claim
32 words
Process according to one of claims 4 to 6, characterized in that the area of the image elements is approximately 25 to 400 mm 2 , preferably about 1 cm 2 .
Claim 9
Dependent Claim
43 words
Process according to one of claims 4 to 7, characterized in that in the measuring of the reference (P) the image elements (E) are divided into subelements (SE) of approximately 0.25 to 25 cm 2 , preferably about 1 m m 2 .
Claim 10
Dependent Claim
60 words
Process according to claim 8, characterized in that for each individual subelement (SE) of an image element (E) with consideration of the parameters controlling the printing process a subreference reflectance value (RS s ) and from all of the subreference reflectance values of an image element the reference reflectance value (R s ) of the image element concerned, are formed.
Claim 11
Dependent Claim
29 words
Process according to claim 9, characterized in that the reference reflectance value (R s ) is calculated by an averaging method from the subreference reflectance values (RS S ).
Claim 12
Dependent Claim
79 words
Process according to one of claims 9 and 10, characterized in that to each subelement (SE) a sub-full tone weighting factor (GS e ) and/or a sub- perception factor (HS e ) are assigned, and that the full tone and the perception weighting factors (G e , He) of an image element (E) are calculated by averaging from the sub-full tone and sub-perception factors (GS e , HS e ) of the subelements (SE) of the corresponding image element.
Claim 13
Dependent Claim
61 words
Process according to one of claims 1 to 11, characterized in that the summation of the weighted differences (A e ) is carried out over the image elements (E) belonging to a common printing zone (Z) or a selected surface area, to obtain a zonal error value (O Z ) or an area error value, which represents the quality measure (Q).
Claim 14
Dependent Claim
46 words
Process according to claim 3, characterized in that for every ink color the reference reflectance values (R s ) and the corresponding full tone and/or perception weighting factors (G e , He) of the image elements (E) are obtained from one and the same reference (P).
Claim 15
Dependent Claim
39 words
Process according to claim 3, characterized in that the reference reflectance values (R s ) are determined from a printed product (OK8) and the full tone and/or perception weighting factors from the corresponding printing plates (P) or photographic master.
Claim 16
Dependent Claim
33 words
Process according to one of the preceding claims, characterized in that the printed product (D) is measured densitometrically for the determination of the actual reflectance values (R;) before and after each printing mechanism.
Claim 17
Dependent Claim
270 words
Apparatus for the evaluation of the printing quality of a printed product produced on a printing machine by means (120, 220) for the photoelectric scanning by image elements of printed products and a reference, and with a computer (150,250) connected with said scanning means for the comparison by image elements of printed products and the reference, and for the formation of a quality measure (Q) from the results of said comparison, characterized in that for the determination by measuring techniques of at least the actual reflectance values for each printed color a densitometer is provided and the computer is equipped to store a plurality of perception weighting factors expressing the relationship between the sensitometric and technically measured color deviations for different reflectances and/or a plurality of full tone weighting factors stating the effect of full tone density on reflectance in the case of different surface coverages, to assign to every image element (E) of the printed product a perception weighting factor (He) selected as a function of the reflectance determined for the element concerned and/or as a function of its surface coverage and the color involved a full tone weighting factor (G e ), in order to obtain on the one hand a sensitometric color coordinate system and to determine, optionally without the use of a color measuring strip full tone, deviations from the reference, and on the other, to weight the differences by image element detected by the scanning means (120, 220) between the printed product and the reference with the associated perception weighting factor and full tone weighting factor, and from this to form the quality measure (Q).
Claim 18
Dependent Claim
270 words
Apparatus for the evaluation of the printing quality of a printed product produced on a printing machine by means (120, 220) for the photoelectric scanning by image elements of printed products and a reference, and with a computer (150,250) connected with said scanning means for the comparison by image elements of printed products and the reference, and for the formation of a quality measure (Q) from the results of said comparison, characterized in that for the determination by measuring techniques of at least the actual reflectance values for each printed color a densitometer is provided and the computer is equipped to store a plurality of perception weighting factors expressing the relationship between the sensitometric and technically measured color deviations for different reflectances and/or a plurality of full tone weighting factors stating the effect of full tone density on reflectance in the case of different surface coverages, to assign to every image element (E) of the printed product a perception weighting factor (He) selected as a function of the reflectance determined for the element concerned and/or as a function of its surface coverage and the color involved a full tone weighting factor (G e ), in order to obtain on the one hand a sensitometric color coordinate system and to determine, optionally without the use of a color measuring strip full tone, deviations from the reference, and on the other, to weight the differences by image element detected by the scanning means (120, 220) between the printed product and the reference with the associated perception weighting factor and full tone weighting factor, and from this to form the quality measure (Q).
Claim 19
Dependent Claim
29 words
Apparatus according to claim 16, characterized in that the scanning means (120, 220) are capable of scanning the reference (P) with a higher resolution than the printed products (D).
Claim 20
Dependent Claim
31 words
Apparatus according to claim 17, characterized in that the scanning means (120, 220) are equipped to scan a reference in the form of a printing plate (P) photoelectrically by image element.
Claim 21
Dependent Claim
28 words
Apparatus according to one of claims 16 to 18, characterized in that it is equipped to carry out the steps according to one of claims 2 to 15.
Claim 22
Dependent Claim
57 words
Apparatus according to one of claims 16 to 19, characterized in that it comprises a display (171, 172, 270, 370) for the graphical representation of the measured refelectances of the reference and/or the reference reflectance values calculated therefrom and/or the actual refelctance values of the printed products and/or the differences between the reference and actual reflectance values.
Claim 23
Dependent Claim
22 words
Offset printing machine characterized by an apparatus for the evaluation of the printing quality according to one of claims 16 to 20.
References Cited (Backward Citations)
No citation records indexed.
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