Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2002-06-19
2004-07-13
Gordon, Raquel Yvette (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
Reexamination Certificate
active
06761426
ABSTRACT:
This application is based on Patent Application No.
2001-187109
filed Jun. 20, 2001 in Japan, the content of which is incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a calibration apparatus, an ink jet printing apparatus, a calibration method, and a medium on which a test image for calibration is printed, which all serve for a calibration which makes printing characteristics of a printing apparatus, such as a printer, to be constant, and in particular, to a test image used for the calibration that makes it possible to reduce an effect of variation in printing characteristics on calibration when printing a test pattern.
2. Description of the Related Art
Color input or output devices including input devices such as scanners and digital cameras and output devices such as monitors and printers have expressible specific color spaces, respectively. Thus, essentially, colors displayed on the monitor appear different when output from a printer. To eliminate this difference, in a system or environment using the above input and output devices, color matching between these devices is carried out by using profiles, i.e., data representative of color transformation characteristics for the respective devices.
For example, an output profile for a printer is generated as follows during a printer calibration process. First, on the basis of predetermined patch data consisting of signal values for R (red), G (green) and B (blue), or C (cyan), M (magenta), Y (yellow) and K (black), i.e., color signals for a color space dependent on the printer, the printer, for which the profile is to be generated, outputs a patch pattern. Next, the patch pattern is subjected to colorimetry using a densitometer or the like, to determine values such as XYZ or Lab, i.e., a color signal for a color space not dependent on the printer. Then, the relationship between the signal values for, for example, R, G, and B for the color space dependent on the printer, and the signal values for, for example, X, Y, and Z for the color space not dependent on the printer, is found. The thus found relationship between the RGB values and the XYZ values is used to determine a masking coefficient on the basis of an interaction method or a mapping from the RGB values to the XYZ values. Then the transformation relationship from the XYZ values to the RGB values, i.e., the reverse of the above transformation relationship, is determined as color modification data.
The profile thus obtained is used, for example, for an image processing executed when image data on the monitor is output by the printer. Then, the colors displayed on the monitor appear substantially the same as what is output by the printer.
In the above-described profile generating process, in which the transformation relationship from the RGB or CMYK signal values to the XYZ or Lab values is determined, as described above, generally, color patches are output and their density measured using a colorimeter or a densitometer so as to generate a correspondence table for the RGB or CMYK values and the XYZ or Lab values on the basis of the results of the measurements.
A printing apparatus such as a printer for which the above-described profile is generated may print an image with a different density depending on a printing position on a sheet even when the image is printed on the same sheet. For example, in a case of an ink jet printer, as a printing head that ejects ink to perform an ejection operation, generally, the temperature of the head increases. As a result, even if signals with the same value are input, the resulting amount of ink ejected may increase consistently with temperature. Consequently, as printing operations are sequentially performed on the sheet, the temperature of the printing head may vary, thereby varying the density depending on the printing position on the sheet. This also applies to the printing of the above-described patch pattern.
To verify such a variation in density,
FIG. 1
schematically shows the distribution of the measured optical densities of a plurality of patches printed on the same sheet, which are gray patches of the same value for the R, G, and B signals, for example, R=G=B=
192
as shown in
FIG. 3
, and are arranged in length and breadth directions to form a matrix pattern. In
FIG. 1
, for simplification of description and illustration, the measured densities of these patches are continuously expressed in the sheet though the patches are separated from one another. Further, the density of the patch is expressed on the basis of the density of lines in such a manner that the density of the patch increases in proportion to the density of the lines. Furthermore,
FIG. 3
, referenced above for the signal values, shows the contents of a distribution table (color separation table) that allows the R, G, and B signal values to be transformed into signals corresponding to the respective color inks actually used by the printer. The example shown in
FIG. 3
relates to a printer using cyan (C), magenta (M), yellow (Y), and black (K) inks, as well as light cyan (lc) and light magenta (lm) inks, which have lower dye concentration than the above group of inks. Further,
FIG. 3
shows a part of the table, which allows the R, G, and B signal values to be transformed into signal values for the corresponding inks, i.e., the figure shows the case in which R=G=B=
192
. Besides, according to this table, when R, G, B signals have values R=G=B=
192
as referenced above, the yellow Y, light cyan lc, and light magenta lm inks are used for printing.
As shown in
FIG. 1
, the printing head performs a scanning operation in a main-scanning direction as shown by the arrow in the figure. During the scanning operation, ink is ejected through ink ejection openings of the printing head to carry out printing. Then, while the printing head is moving in the direction opposite to the main-scanning direction, shown by the arrow, the sheet is fed in a sub-scanning direction. Printing for the entire page of the sheet is performed by repeating the scanning operation of the printing head and the sheet feeding operation.
As is apparent from this figure, during the scanning operation of the printing head, the density increases along the main-scanning direction from a printing start position and along the sub-scanning direction.
FIG. 2
shows a distribution of densities similar to that of
FIG. 1
, wherein signal values for the patch pattern are used to eject inks so that the amount of ink or the number of ink types landing per unit area is increased compared to the patch pattern shown in
FIG. 1
; for example, R=G=B=
96
is used in FIG.
2
. This figure indicates that the tendency described in
FIG. 1
becomes more significant as the total amount of ink landing per unit area increases. Further, when the number of ink types used for printing increases, this increasing easily causes the number of times of driving to be different between respective nozzles of ink types, which communicate with respective ejection openings, and thereby an ejection amount of respective nozzles of ink types individually vary so that difference in color tones between the printing positions becomes greater. That is, a rate of variation in density on the sheet becomes greater, and therefore a difference in density between the printing positions on the sheet becomes greater.
Further, a temperature variation associated with an ejecting operation of the printing head, which may cause the density to be varied as shown in
FIGS. 1 and 2
, generally behaves in such a manner as to gradually approach a certain relatively high temperature. This behavior basically depends on the heat accumulation and radiation characteristics of the printing head. More specifically, as the printing position in the sheet in
FIG. 1
or
2
moves rightward and downward, the temperature increases as well as a difference in temperature between printing positions becomes small.
Furt
Nagoshi Shigeyasu
Tsuchiya Okinori
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Gordon Raquel Yvette
Stewart, Jr. Charles
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