Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2000-04-18
2002-09-17
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S043000, C399S049000
Reexamination Certificate
active
06450606
ABSTRACT:
This application is based on Japanese Patent Application No. 11-111494 (1999) filed Apr. 19, 1999, the content of which is incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to test pattern printing methods, and more specifically to a test pattern printing method to print a test pattern which is checked to detect a color deviation caused by variations in an output characteristic among several print heads, and an information processing apparatus and a printing apparatus to print the test pattern.
2. Description of the Related Art
As devices for automated office work have come into wide use, the necessity for producing color images has increased. Output devices for outputting color images are known, such as printing apparatuses of various methods, including ink jet, electro-photographic, and heat transfer methods. In recent years, these printing apparatuses have become able to output picture-like color images of relatively high quality.
Such printing apparatuses generally print color images using either three chromatic colorants, cyan (C), magenta (M) and yellow (Y), or four colorants with an additional achromatic color, black (K). The printed color image, however, may have a color deviation or color misrepresentation wherein the produced color in the printed image differs from a desired one due to an imbalance of output characteristics (e.g., reflection density or lightness, saturation, hue, etc.) among the print heads for the each respective color. In the ink jet system, for example, the print heads may have differences in an amount of heat produced by the heaters as a result of differing film thickness of the heaters, and/or differences in the size and shape of the ink ejection orifices, causing individuality in an amount of ejected ink. These differences, in turn, may result in the output characteristic imbalance among the print heads, as described above. Furthermore, these differences are not only inherent to print heads, but it is also known that these differences result over time.
To alleviate this problem of color deviation or misrepresentation, a personal computer functioning as a host computer for the printing apparatus, or the printing apparatus itself, may perform a correction process in which the host computer or printing apparatus detects the color deviation due to the differences among respective print heads and, based on the result of detection, corrects the output characteristics of the print heads to match predetermined characteristics. Such correction processing is generally carried out in two ways distinguished primarily on whether the detection of the color deviation is done by using an input device such as scanner or by a human visual check. An outline of these two correction methods, as distinguished by the way of detecting the color deviation, is briefly explained below.
The method using the input device such as scanner, for example, firstly prints a patch pattern by using the print heads of the C, M, Y and K coloring materials that are subjects of the correction, as disclosed in the official gazette of Japanese Patent No. 2661917. Then, the patch pattern is read by the scanner to detect a difference between a read value which represents an output characteristic of the head and an expected value calculated from the print data for the patch pattern. Based on the detected difference, the color deviation is corrected. The patch pattern used in this method may be a solid pattern of each of the C, M, Y, K colors or a patch pattern of each color having patches showing a gradation in density. The gradation patch pattern can also be used to detect an output characteristic with respect to a halftone, thus improving precision of detecting the color deviation. A method is also known that combines the C, M, Y and K to form second- or third-color patch patterns and thereby improves the detection and correction accuracy.
On the other hand, the method using the visual check, unlike the method using the input device, cannot easily detect an absolute value with respect to the output characteristic for each color head. Hence, a detection method that uses a third-color patch pattern printed by mixing three colorants C, M, Y is more commonly used. More specifically, a plurality of patches of almost gray color are printed. The plurality of patches include a central patch which is expected to be printed at a predetermined ratio of the three colorants (represented by print data of the three colorants) so as to be a patch of an achromatic color when printed by using print heads with an average ink ejection amount or without any deviation of ink ejection amount. The other patches are printed with their three-color ratios successively changed slightly. From the plurality of patches a user visually chooses one patch closest to the achromatic color so as to detect the patch of the most appropriate output characteristic balance among the C, M, Y color print heads. Then, the correction data corresponding to the detected patch is used to correct the output characteristic of each print head. This method of detecting the color deviation takes advantage of a fact that a slight imbalance in the output characteristics among the C, M, Y color print heads causes relatively large output characteristic changes in the patch, resulting in the patch deviating from the achromatic color.
While the problem of color deviation and the method of its detection have been described for the case of the print heads of ink jet system, differences in the output characteristics of the color print heads may also occur with printing apparatuses using electrophotographic or heat transfer systems due to causes peculiar to the principles of the respective printing systems. In these printing systems, also, the color deviation detection and correction are performed in the similar manner.
Unfortunately, the conventional color deviation detection method described above has several drawbacks.
First, in a typical environment in which the printing apparatus is used, the method using an input device such as a scanner requires that the user controls, has access to, or “owns” the input device. However, in a typical environment not all users have the input device available. Thus the method using the scanner or other input devices is not practical. Further, even if some input device is made available, the correction process on a basis of the color deviation detection using such wide variation of input devices is often very difficult to carry out.
The method based on visual check, on the other hand, does not require any special input device and thus can be employed by any user to detect color deviation. It is, however, not easy to select a patch closest to the achromatic color from the plurality of patches with their C, M, Y color ratios progressively yet slightly changed.
For example, JIS (JIS E3305, JIS Z8721, JIS L0600, etc.) and various other specifications concern a color difference (&Dgr;E). In these specifications, a range of the color difference of 3.2-6.5 is defined as a “range that can be handled as the same color in terms of impression.” This suggests that visually picking a patch closest to the achromatic color from patches in this range of color difference is difficult. It is also stated that the color difference in such a range may “cause a customer to complain about difference in color when selecting paint color,” suggesting that even in this range of color difference, if a wrong patch is selected, an image printed after being corrected based on a correction value corresponding to the selected patch may fail to provide a desired color.
For this reason, an effort is being made to improve an accuracy of the visual check-based color deviation detection method.
FIG. 1
is a view schematically showing an example of a test pattern that enables users to detect the color deviation with greater precision. In
FIG. 1
, each frame represents a patch printed with a mixture of C, M and Y colors and with K. The four numbers in each of two areas in each patch
Kanematsu Daigoro
Kato Masao
Kato Minako
Ono Mitsuhiro
Yano Kentaro
Barlow John
Canon Kabushiki Kaisha
Duddling Alfred
Fitzpatrick ,Cella, Harper & Scinto
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