PRINT QUALITY EVALUATION APPARATUS AND METHOD OF PRINT QUALITY EVALUATION

• US 20080219513A1
• Filed: 02/21/2008
• Published: 09/11/2008
• Est. Priority Date: 03/06/2007
• Status: Active Grant

• Current Assignee: S-Printing Solution Co., Ltd. (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: HASEGAWA, Jun
• Granted Patent: US 8,090,156 B2
• Time in Patent Office: Days
• US Class Current: 382/112
• CPC Class Codes: H04N 1/00002 Diagnosis, testing or measuring; Detecting, analysing or monitoring not otherwise provided for error detection, error correction or monitoring in digital computers or digital computer components G06F11/00
• CPC Class Codes: H04N 1/00005 relating to image data
• CPC Class Codes: H04N 1/00015 Reproducing apparatus
• CPC Class Codes: H04N 1/00031 Testing, i.e. determining the result of a trial H04N1/00029 takes precedence; using test signals for transmission mode changing H04N2201/33371
• CPC Class Codes: H04N 1/00045 using a reference pattern designed for the purpose, e.g. a test chart
• CPC Class Codes: H04N 1/00068 Calculating or estimating
• CPC Class Codes: H04N 1/00074 Indicating or reporting details of user-machine interface H04N1/0035

Abstract

A method and apparatus to evaluate print quality determines an indicator thereof by measuring a reflectance of printed dots by scanning a medium on which pattern data having a predetermined pattern is printed. The predetermined pattern includes a highlight region and a shadow region. An average of reflectances of the highlight region in the predetermined pattern and an average of reflectances of the shadow region thereof are determined, and a contrast value is determined from a difference between the averages. The indicator is determined from the contrast value. Accordingly, deterioration of print quality that occurs due to a mismatch of a print position is considered, and furthermore, a change in print gradation and a degree of mixing with noise components is also considered in the print quality evaluation.

Claims

1. A method of evaluating print quality, the method comprising:

measuring a reflectance of printed dots by scanning a medium on which the dots are printed according to pattern data having a predetermined pattern of a highlight region and a shadow region;

determining an average of reflectances of the highlight region in the predetermined pattern and an average of reflectances of the shadow region thereof;

determining a contrast value from a difference between the average of the reflectances of the highlight region and the average of the reflectances of the shadow region; and

determining an indicator of the print quality from the contrast value.

2. The method of claim 1, further comprising:

classifying pixels respectively assigned a value corresponding to a reflectance of a corresponding one of the printed dots from the scanning thereof as corresponding to the dot in the highlight region or the shadow region of the predetermined pattern.

3. The method of claim 2, wherein the classifying of pixels further comprises:

determining a position of each of the pixels, the pixels being classified into the highlight region and the shadow region in the predetermined pattern on the basis of the position of each of the pixels.

4. The method of claim 2, wherein the classifying of the pixels further comprises:

mapping a scan image formed from the pixels based on the measured reflectance onto an image formed directly from the pattern data.

5. The method of claim 1,

wherein the contrast value is determined through machine computations of the following equations:

${\stackrel{\_}{R}}_0=\frac{1}{n_0}<br><br>\underset{i\in <br><br>{\mathrm{\Omega <br><br>}}_0}{\sum <br><br>}<br><br>R<br><br>\left(x_i,y_i\right);<br><br>$ ${\stackrel{\_}{R}}_1=\frac{1}{n_1}<br><br>\underset{j\in <br><br>{\mathrm{\Omega <br><br>}}_1}{\sum <br><br>}<br><br>R<br><br>\left(x_j,y_j\right);<br><br>$ $\mathrm{and}$ $C_t=k·<br><br><br><br>{\stackrel{\_}{R}}_1-{\stackrel{\_}{R}}_0<br><br>·<br><br>100,$

wherein, R₀, R₁, and C_t respectively denote the average of reflectances of the shadow region, the average of reflectances of the highlight region, and the contrast value;

n₀ and n₁ denote the numbers of pixels used to obtain the average of reflectances of the shadow region and the average of reflectances of the highlight region , respectively;

R(x, y) denotes a reflectance assigned to the pixel at coordinates (x, y);

Ω

₀ and Ω

₁ respectively denote a set of pixels included in the shadow region and a set of pixels included in the highlight region; and

k is a constant.

6. The method of claim 1,

wherein the predetermined pattern includes a plurality of bar patterns in which the highlight region and the shadow region have widths corresponding to a plurality of predetermined resolution values, the contrast values being determined from each of the bar patterns.

7. An apparatus to evaluate print quality, the apparatus comprising:

a scanner to obtain a reflectance of printed dots on a medium and to assign the reflectance to at least one pixel in a scan image, the dots printed according to pattern data having a predetermined pattern of a highlight region and a shadow region;

a contrast determining unit to determine an average of reflectances of the highlight region in the predetermined pattern and an average of reflectances of the shadow region thereof, and to determine a contrast value from a difference between the average of reflectances of the highlight region and the average of reflectances of the shadow region; and

an indicator determining unit to determine an indicator of the print quality from the determined contrast value.

8. The apparatus of claim 7, further comprising:

a pixel classifier to classify the pixels as being from the highlight region or the shadow region of the predetermined pattern.

9. The apparatus of claim 8, further comprising:

a position determining unit to determine a position of each of the pixels in relation to a position of the corresponding dot in the predetermined pattern, wherein the pixel classifier classifies pixels as being from the highlight region or the shadow region in the predetermined pattern from the determined position of each of the pixels.

10. The apparatus of claim 8, wherein the pixel classifier classifies the pixels into the highlight region and the shadow region of the predetermined pattern by mapping the scan image of the measured reflectance onto an image formed directly from the pattern data.

11. The apparatus of claim 7,

wherein the contrast value is determined through machine computations of the following equations:

${\stackrel{\_}{R}}_0=\frac{1}{n_0}<br><br>\underset{i\in <br><br>{\mathrm{\Omega <br><br>}}_0}{\sum <br><br>}<br><br>R<br><br>\left(x_i,y_i\right);<br><br>$ ${\stackrel{\_}{R}}_1=\frac{1}{n_1}<br><br>\underset{j\in <br><br>{\mathrm{\Omega <br><br>}}_1}{\sum <br><br>}<br><br>R<br><br>\left(x_j,y_j\right);<br><br>$ $\mathrm{and}$ $C_t=k·<br><br><br><br>{\stackrel{\_}{R}}_1-{\stackrel{\_}{R}}_0<br><br>·<br><br>100,$

wherein, R₀, R₁, and C_t respectively denote the average of reflectances of the shadow region, the average of reflectances of the highlight region, and the contrast value;

n₀ and n₁ denotes the numbers of pixels used to obtain the averages, respectively;

R(x, y) denotes a reflectance assigned to the pixel at coordinates (x, y);

Ω

₀ and Ω

₁ respectively denote a set of pixels included in the shadow region and a set of pixels included in the highlight region; and

k is a constant.

12. The apparatus of claim 7, wherein the predetermined pattern includes a plurality of bar patterns in which the highlight region and the shadow region have widths corresponding to a plurality of predetermined resolution values, the contrast determining unit determining the contrast values corresponding to each of the bar patterns.

13. A method of evaluating print quality of a printer comprising:

printing on the printer pattern data of a plurality of dot patterns each having a contrast respectively defined by a plurality of print resolutions;

measuring the contrast in each of the dot patterns of the printed pattern data; and

determining the print quality from a distribution of the measured contrast from each of the printed dot patterns.

14. The method of claim 13, wherein the measuring of the contrast further comprises:

measuring a characteristic of the printed pattern data and assigning a value of the measurement to respective pixels of an image; and

determining the measured contrast from pixels of the image.

15. The method of claim 14, wherein the determining of the measured contrast further comprises:

classifying each of the pixels as containing the measured characteristic of a dot in a print region of the corresponding one of the dot patterns or in a non-print region of the corresponding one of the dot patterns from a position thereof in the image;

determining an average of the measured characteristic of the pixels classified as from the print region of the corresponding one of the dot patterns and an average of the measured characteristic of the pixels classified as from the non-print region of the corresponding one of the dot patterns; and

establishing as the measured contrast of each of the dot patterns a difference between the average measured characteristic of the pixels from the print region thereof and the average measured characteristic of the pixels in the non-print region thereof.

16. The method of claim 14, wherein the measuring of the characteristic further comprises:

optically scanning the printed dot patterns at predetermined positions therein to measure a reflectance as the quality of the printed pattern data.

17. The method of claim 13, wherein the determining of the print quality further comprises:

determining as the print quality a maximum one of the print resolutions at which the measured contrast is above a threshold value.

18. A method of evaluating print quality comprising:

scanning a printed pattern corresponding to an ideal shading model provided to a printer;

determining a contrast level in the scanned pattern at which a difference in measured values in printed and non-printed regions of the ideal shading model remain statistically significant to a predetermined significance level; and

providing an indicator of the print quality corresponding to the contrast level.

19. The method of claim 18, wherein the providing of the indicator further comprises:

providing a print resolution corresponding to the contrast level as the indicator.

20. The method of claim 18, wherein the providing of the indicator further comprises:

providing an integrated area defined by contrast values in the scanned pattern at which the difference in measured values in the printed and the non-printed regions of the ideal shading model remain statistically significant above the predetermined significance level.

21. An apparatus to evaluate print quality of a printer comprising:

a scanner to form a scan image of pixels containing measurement data of pattern data printed by the printer;

a pixel identifier to determine respective positions of the pixels in the scan image and to determine from the positions whether a pixel contains the measurement data of a printed region or a non-printed region of the pattern data; and

an output device to provide an indicator of the print quality corresponding to a contrast value in the scan image at which a difference in the measurement data in the printed and the non-printed regions of the pattern data remains statistically significant to a predetermined significance level.

22. The apparatus of claim 21, further comprising:

a contrast determining unit to determine the contrast value of each of a plurality of print resolution patterns having the printed and the non-printed regions; and

an indicator determining unit to determine the contrast value at which the difference in the measurement data in the printed and the non-printed regions of the pattern data remain statistically significant to the predetermined significance level.

23. An apparatus to evaluate print quality of a printer comprising:

a storage unit having stored therein an image of pixels containing measurement data of printed pattern data corresponding to an ideal shading model; and

a print quality evaluator to determine a maximum print quality from a difference in respective averages of the measurement data corresponding to printed and non-printed regions of the ideal shading model that remains statistically significant to a predetermined significance level.