CA1204880A - Method of automatically determining and controlling the print quality of a printer - Google Patents
Method of automatically determining and controlling the print quality of a printerInfo
- Publication number
- CA1204880A CA1204880A CA000441818A CA441818A CA1204880A CA 1204880 A CA1204880 A CA 1204880A CA 000441818 A CA000441818 A CA 000441818A CA 441818 A CA441818 A CA 441818A CA 1204880 A CA1204880 A CA 1204880A
- Authority
- CA
- Canada
- Prior art keywords
- print quality
- value
- pcs
- optimum
- printer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J7/00—Type-selecting or type-actuating mechanisms
- B41J7/96—Means checking correctness of setting
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41F—PRINTING MACHINES OR PRESSES
- B41F33/00—Indicating, counting, warning, control or safety devices
- B41F33/0036—Devices for scanning or checking the printed matter for quality control
Abstract
METHOD OF AUTOMATICALLY DETERMINING AND
CONTROLLING THE PRINT QUALITY OF A PRINTER
Abstract The invention concerns a computer-controlled method of automatically determining the print quality value of a printer and of controlling the print quality value towards an optimum value DQopt, using both the empirically determined average optimum image contrast signal (PCS) and the standard deviation ? PCS. the average optimum image contrast signal is derived from the relation where RB is the reflection of the background and Ri is the reflection of a picture element or dot i (PEL). The actual value of the image contrast signal is derived from the individual values PCS = for all n picture by optoelectronically scanning all picture elements i of a character along the skeleton line and the background, and deriving from these scanning values a factor and a print quality factor and deriving ln x2 from said print quality factor.
Subsequently the actual print quality value DQ = aO + a1 ? ln x2 is determined, and by iterative automatic comparison of the stored optimum print quality value DCopt and the print quality thus determined, control variables are derived and used in a closed control loop for adjusting the different printer parameters.
CONTROLLING THE PRINT QUALITY OF A PRINTER
Abstract The invention concerns a computer-controlled method of automatically determining the print quality value of a printer and of controlling the print quality value towards an optimum value DQopt, using both the empirically determined average optimum image contrast signal (PCS) and the standard deviation ? PCS. the average optimum image contrast signal is derived from the relation where RB is the reflection of the background and Ri is the reflection of a picture element or dot i (PEL). The actual value of the image contrast signal is derived from the individual values PCS = for all n picture by optoelectronically scanning all picture elements i of a character along the skeleton line and the background, and deriving from these scanning values a factor and a print quality factor and deriving ln x2 from said print quality factor.
Subsequently the actual print quality value DQ = aO + a1 ? ln x2 is determined, and by iterative automatic comparison of the stored optimum print quality value DCopt and the print quality thus determined, control variables are derived and used in a closed control loop for adjusting the different printer parameters.
Description
8~(~
~IEI'HOD OF AUTO~TICALLY DETER~IINING ~ND
CONTROLLING TH~ PRINT QUALITY OF A PRINTER
_ Field of the Invention The inven-tion concerns a computer-controlled method of automatically determining the respective print quality value of a printer towards an optimum value, using both the empirically detennined average image contrast signal PCS and the standard deviation cPCS, said average image contrast RB - Ri ' signal being derived from the relation R ~ where RB is the reflection of the background and Ri is the reflection of the ith picture element or dot.
The print quality is a subjective quantity and can be empirically de-termined by a number of originals of equal quality or originals whose quality increases (or decreases) in steps or continuously being subjected to a statistically relevant number of individual evaluations by an equally statistically relevant number of observers. In this manner, as a number of tests with similar results have shown, relatively reliable print quality data are obtained, particularly when the results are associated with graded, say 6, quality classes.
The new method is to be used in particular to continuously monitor and, if necessary, correct the image of a line printer, raster printer, or the like. For this purpose, a numher oE print quality parameters have to be observed which, depending upon the respective print method and the printer used, are of different significance or importance. If characters are partly cut off, the control of the hammer flight time, for example, is incorrect or the type carrier is too fast or too slow, the hammer is triggered too early or too late. Smudged or heavy printing may result, for example, from the print hammer or print head impact being too strong or too weak. Heavy or weak printing may also be caused by a ribbon or inking cloth which is too new or worn, so that the ribbon or cloth structure becomes visible. To overcome these difficu~ties, it is possible, lZD~
for e~ample, to proceed from a predetermined mean print quali-t~f value which may nevertheless be described as very good and which constitutes a reliable optimum value for long--term control and adjus-tment. In accordance with the inventi.on, this ls accomplished by the actual value of the irnage contrast RB ~ ~
signal being derived from the individual values PCS - ~ for al~ n picture elements by optoelec-tronically scanning all picture elernents i of a character along the skeleton line and the background, by deriving from n _ _ _ __ ~ ,/ (PCS-PCSi)2 these scanning values a factor ~ = L ¦ - and a print PCS i=l ~ n-l quality factor x2 = PCS and by deriving ln x2 Erom said print quality factor, that subsequently the actual print quality value DQ = aO ~ al ln X2 is determined, and that by itexative automatic comparison of the stored optimum print quality value DC t and the print quality thus detennilled, control variables are derived and used in a closed control loop for adjusting the difEerent printer parameters.
Further embodiments of the invention may be seen from the subclaims.
One way of carrying out the invention will be described in detai]. below with reference to the attached drawings referred to in the specification.
For determining a subjective print quality factor, a representative quantity of originals of the same and/or of different quality are submitted to an equally representative group of evaluators for evaluation. The evaluators are requested to rate the quality, using a factor from 1 to 6 or interrnediate values 1.5, 2.5, etc. These evaluations are assessed by means of statistical methods. As a result, a formula,X2, is obtained which ~ermit~
the evaluations of the evaluators to be mathema-tically predicted with adequate accuracy if the relevant print quality parameters have been determined by measuremen-t. One of these parameters is the print contrast signa]. PCS. Using the above-mentioned method, this signal is determine~d by scanning along the skeleton line according to DIN 66 223 and across the background of the original. Thus, this pararneter is derived from the diEferent reflection values oE the skeleton line relative to the back-ground.
,,, _ _, .. . __.. , . __ ...... _ . . . . _. ... ... . . _ . , , ~ 3 ~ ~ 2 ~ 4 8 8 ~
This scanning yields different values, depending upon the quality of the scanned characters. The variation of this parameter in the original may be described by means of three expressions:
1. PCS (mean value),
~IEI'HOD OF AUTO~TICALLY DETER~IINING ~ND
CONTROLLING TH~ PRINT QUALITY OF A PRINTER
_ Field of the Invention The inven-tion concerns a computer-controlled method of automatically determining the respective print quality value of a printer towards an optimum value, using both the empirically detennined average image contrast signal PCS and the standard deviation cPCS, said average image contrast RB - Ri ' signal being derived from the relation R ~ where RB is the reflection of the background and Ri is the reflection of the ith picture element or dot.
The print quality is a subjective quantity and can be empirically de-termined by a number of originals of equal quality or originals whose quality increases (or decreases) in steps or continuously being subjected to a statistically relevant number of individual evaluations by an equally statistically relevant number of observers. In this manner, as a number of tests with similar results have shown, relatively reliable print quality data are obtained, particularly when the results are associated with graded, say 6, quality classes.
The new method is to be used in particular to continuously monitor and, if necessary, correct the image of a line printer, raster printer, or the like. For this purpose, a numher oE print quality parameters have to be observed which, depending upon the respective print method and the printer used, are of different significance or importance. If characters are partly cut off, the control of the hammer flight time, for example, is incorrect or the type carrier is too fast or too slow, the hammer is triggered too early or too late. Smudged or heavy printing may result, for example, from the print hammer or print head impact being too strong or too weak. Heavy or weak printing may also be caused by a ribbon or inking cloth which is too new or worn, so that the ribbon or cloth structure becomes visible. To overcome these difficu~ties, it is possible, lZD~
for e~ample, to proceed from a predetermined mean print quali-t~f value which may nevertheless be described as very good and which constitutes a reliable optimum value for long--term control and adjus-tment. In accordance with the inventi.on, this ls accomplished by the actual value of the irnage contrast RB ~ ~
signal being derived from the individual values PCS - ~ for al~ n picture elements by optoelec-tronically scanning all picture elernents i of a character along the skeleton line and the background, by deriving from n _ _ _ __ ~ ,/ (PCS-PCSi)2 these scanning values a factor ~ = L ¦ - and a print PCS i=l ~ n-l quality factor x2 = PCS and by deriving ln x2 Erom said print quality factor, that subsequently the actual print quality value DQ = aO ~ al ln X2 is determined, and that by itexative automatic comparison of the stored optimum print quality value DC t and the print quality thus detennilled, control variables are derived and used in a closed control loop for adjusting the difEerent printer parameters.
Further embodiments of the invention may be seen from the subclaims.
One way of carrying out the invention will be described in detai]. below with reference to the attached drawings referred to in the specification.
For determining a subjective print quality factor, a representative quantity of originals of the same and/or of different quality are submitted to an equally representative group of evaluators for evaluation. The evaluators are requested to rate the quality, using a factor from 1 to 6 or interrnediate values 1.5, 2.5, etc. These evaluations are assessed by means of statistical methods. As a result, a formula,X2, is obtained which ~ermit~
the evaluations of the evaluators to be mathema-tically predicted with adequate accuracy if the relevant print quality parameters have been determined by measuremen-t. One of these parameters is the print contrast signa]. PCS. Using the above-mentioned method, this signal is determine~d by scanning along the skeleton line according to DIN 66 223 and across the background of the original. Thus, this pararneter is derived from the diEferent reflection values oE the skeleton line relative to the back-ground.
,,, _ _, .. . __.. , . __ ...... _ . . . . _. ... ... . . _ . , , ~ 3 ~ ~ 2 ~ 4 8 8 ~
This scanning yields different values, depending upon the quality of the scanned characters. The variation of this parameter in the original may be described by means of three expressions:
1. PCS (mean value),
2. PCS (standard deviation or ~ PCS)' and
3. PCS (voids).
m us the value (l-FCS voids), as the average value, also denotes the comp]eteness of a character. By combining these expressions in the formula x = (1 - PCS (voids¦. PCS sufficiently accurate data are 2 PCS (standard deviation) obtained as to the evaluation behaviour of this group of human evaluators with regard to the print quality of the original. m is is shown in the drawing, whose ordinate represents the evaluation values and whose abscissa indicates the print quality factor x2. The dots represent different samples evaluated and the crosses denote the regression line which is a smoothed line showing the natural logorithm as described in the following paragraph. For this purpose, it is assum~d that-the totality of the evaiuated originals is represented with adequate accuracy by this subquantity. It is assu~ed further than the standard deviation has a value other than zero. This is normally the case.
'rhe x2 value can be linearized by means of the natural algorithm, thusyielding a-linear scale of 1 - 6. This linearization step permits extrapolation to values of less than 1 or greater than 6. In most cases, the characters will be ccmplete, so that the formula x2 may be reduced to x = PCS
2 PCS (standard deviation).
This formula always applies along the skeleton line.
If the PCS standard deviation is zero, which is unlikely~ this formula cannot be used. me reason for this is that the true function of x2 is exp cted to be logarithmic and that the formula for classifying the print quality value is only an approximation from an expansion m-to a series, so that the formula does not become too abstract. For tests where the printed or typed original is of very good yuality, x2 should be replaced by ln x2. This leads to a linear relationship.
OE 9-82~031 ~Z~48B~
The above-mentioned formula can be used for all originals in which the , print contrast, the variations of the print contrast along the skeleton line, the variations of the print contrast between different characters, and the completeness of the individual characters, as well as the edge definition of the individual characters are the essential components of the print quality factor.
The control process is such that the controllable printer parameters aré
stored in a list storage and that the control variable causes the in-dividual parameters, ordered according to their efficiency, to be suc-cessively adjusted until the optimum print quality has been reached or has been approximately reached by comparison with the stored value.
, The scanning values may be derived in principle either from the characters of a print line or from characters to be printed outside the image and which are particularly suited for accurate adjustment to the optimum print quality. Such patterns may be, for example, dot patterns, line patterns or patterns with only one dot, or patterns with concentric circles or the like. For implementing the method, a photoelectronic scanner, arranged in a minimum of space directly above the print line, records the scanning values, forming the pr mt quality factor DQ in a simple computer circuit.
.:
~ ' .
m us the value (l-FCS voids), as the average value, also denotes the comp]eteness of a character. By combining these expressions in the formula x = (1 - PCS (voids¦. PCS sufficiently accurate data are 2 PCS (standard deviation) obtained as to the evaluation behaviour of this group of human evaluators with regard to the print quality of the original. m is is shown in the drawing, whose ordinate represents the evaluation values and whose abscissa indicates the print quality factor x2. The dots represent different samples evaluated and the crosses denote the regression line which is a smoothed line showing the natural logorithm as described in the following paragraph. For this purpose, it is assum~d that-the totality of the evaiuated originals is represented with adequate accuracy by this subquantity. It is assu~ed further than the standard deviation has a value other than zero. This is normally the case.
'rhe x2 value can be linearized by means of the natural algorithm, thusyielding a-linear scale of 1 - 6. This linearization step permits extrapolation to values of less than 1 or greater than 6. In most cases, the characters will be ccmplete, so that the formula x2 may be reduced to x = PCS
2 PCS (standard deviation).
This formula always applies along the skeleton line.
If the PCS standard deviation is zero, which is unlikely~ this formula cannot be used. me reason for this is that the true function of x2 is exp cted to be logarithmic and that the formula for classifying the print quality value is only an approximation from an expansion m-to a series, so that the formula does not become too abstract. For tests where the printed or typed original is of very good yuality, x2 should be replaced by ln x2. This leads to a linear relationship.
OE 9-82~031 ~Z~48B~
The above-mentioned formula can be used for all originals in which the , print contrast, the variations of the print contrast along the skeleton line, the variations of the print contrast between different characters, and the completeness of the individual characters, as well as the edge definition of the individual characters are the essential components of the print quality factor.
The control process is such that the controllable printer parameters aré
stored in a list storage and that the control variable causes the in-dividual parameters, ordered according to their efficiency, to be suc-cessively adjusted until the optimum print quality has been reached or has been approximately reached by comparison with the stored value.
, The scanning values may be derived in principle either from the characters of a print line or from characters to be printed outside the image and which are particularly suited for accurate adjustment to the optimum print quality. Such patterns may be, for example, dot patterns, line patterns or patterns with only one dot, or patterns with concentric circles or the like. For implementing the method, a photoelectronic scanner, arranged in a minimum of space directly above the print line, records the scanning values, forming the pr mt quality factor DQ in a simple computer circuit.
.:
~ ' .
Claims (3)
1. Computer-controlled method of automatically determining the respective print quality value of a printer and of controlling said print quality value towards an optimum value DQopt' using both the empirically determined average optimum image contrast signal (PCS) and the standard deviation 6 PCS, said average optimum image contrast signal being derived from the relation where RB is the reflection of the background and Ri is the reflection of a picture element or dot i (PEL), characterized in that the actual value of the image contrast signal is derived from the individual values PCS= for all n picture elements by optoelectronically scanning all picture elements i of a character along the skeleton line and the background, deriving from these scanning values a factor and a print quality factor and deriving ln x2 from said print quality factor, that subsequently the actual print quality value DQ = a0 + a1 ln x2 is determined, and that by iterative automatic comparison of the stored optimum print quality value DCopt and the print quality thus determined, control variables are derived and used in a closed control loop for adjusting the different printer parameters.
2. Method according to claim 1, characterized in that the different controllable printer parameters are stored in a list storage, and that the control variable causes the individual parameters, ordered according to their efficiency, to be successively adjusted until, by continuous comparison, the optimum print quality has been reached or has been approximately reached.
3. Method according to claim 1 or 2, characterized in that characters, which are particularly suited for accurate adjustment to the optimum print quality, are printed in each print line outside the image, said characters consisting either of a dot pattern, a line pattern, a single dot or a dark area.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP19830100692 EP0115546B1 (en) | 1983-01-26 | 1983-01-26 | Automatic print quality assessment and adjustment of a printer |
| EP83100692.9 | 1983-01-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1204880A true CA1204880A (en) | 1986-05-20 |
Family
ID=8190262
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000441818A Expired CA1204880A (en) | 1983-01-26 | 1983-11-24 | Method of automatically determining and controlling the print quality of a printer |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0115546B1 (en) |
| JP (1) | JPS59138457A (en) |
| CA (1) | CA1204880A (en) |
| DE (1) | DE3382418D1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0527285A2 (en) * | 1991-08-12 | 1993-02-17 | KOENIG & BAUER-ALBERT AKTIENGESELLSCHAFT | Method for evaluating the quality of printed sheets |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1226948A (en) * | 1984-04-13 | 1987-09-15 | Tohru Ozaki | Apparatus for evaluating density and evenness of printed patterns |
| EP0772145A3 (en) * | 1995-11-06 | 1999-02-24 | JOHNSON & QUIN, INC. | System and method for determining quality of printed matter |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2727227A1 (en) * | 1977-06-16 | 1978-12-21 | Heidelberger Druckmasch Ag | DEVICE FOR QUALITY ASSURANCE OF PRINT PRODUCTS |
| DE2727426B2 (en) * | 1977-06-18 | 1981-04-30 | Heidelberger Druckmaschinen Ag, 6900 Heidelberg | Device for controlling the ink supply of a sheet-fed offset printing machine |
-
1983
- 1983-01-26 DE DE8383100692T patent/DE3382418D1/en not_active Expired - Lifetime
- 1983-01-26 EP EP19830100692 patent/EP0115546B1/en not_active Expired - Lifetime
- 1983-11-24 CA CA000441818A patent/CA1204880A/en not_active Expired
- 1983-11-29 JP JP58223390A patent/JPS59138457A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0527285A2 (en) * | 1991-08-12 | 1993-02-17 | KOENIG & BAUER-ALBERT AKTIENGESELLSCHAFT | Method for evaluating the quality of printed sheets |
| EP0527285A3 (en) * | 1991-08-12 | 1993-12-08 | Koenig & Bauer Ag | Method for evaluating the quality of printed sheets |
| US5317390A (en) * | 1991-08-12 | 1994-05-31 | Koenig & Bauer, Aktiengesellschaft | Method for judging printing sheets |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0115546B1 (en) | 1991-09-25 |
| DE3382418D1 (en) | 1991-10-31 |
| EP0115546A1 (en) | 1984-08-15 |
| JPS59138457A (en) | 1984-08-08 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |