Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2002-06-28
2004-08-03
Nguyen, Thinh (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S019000
Reexamination Certificate
active
06769759
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a technique for performing printing by recording ink dots on a recording medium while a print head is moving in the main scan direction.
2. Description of the Related Art
Ink jet printers which eject ink from a head and laser printers have become popular as output devices for computers. Especially in recent years, color printers using color inks have also been widely utilized.
Various types of printing media for ink jet printers have been commercially marketed. Since the coloring properties of inks differ in different printing media, there are considerable differences in the images obtained. The type of printing medium used also affects the precision of the sub-scan feed of the printing medium (hereafter referred to as the “paper feed”). For example, the actual feed amount may vary considerably between printing media with easy-slip surfaces and printing media with surfaces that do not slip easily, even if the same feed operation is performed. Furthermore, the precision of the paper feed tends to vary considerably from printer to printer.
The degree of precision of the paper feed has a great effect on the image quality. However, in the case of printers that perform printing using a so-called interlace recording mode, the image quality degradation caused by paper feed error can be suppressed to some extent by appropriately setting the paper feed amount. Here, the term “interlace recording mode” refers to a printing method that is performed using a print head that has nozzles aligned in a row at a nozzle pitch that is twice the dot pitch in the sub-scan direction (i.e., the main scan line pitch) or greater. In cases where such a print head is used, gaps are generated between the main scan lines (raster lines) that are recorded by a single main scan pass. Furthermore, a number of main scan passes that is equal to the number of main scan lines contained in these gaps is further required in order to eliminate the gaps. It is known that various feed amounts can be used in the case of such an interlace recording mode. Conventionally, therefore, the effect of variation in the paper feed precision on the mage quality has be minimized by appropriately selecting the paper feed amount in the interlace recording mode.
For the reasons described above, the direct correction of paper feed error in printers using an interlace recording mode has not been seriously considered. However, as high image quality in printers has spread in recent years, there has been a demand for further improvement of image quality by the appropriate correction of paper feed error in printers that perform printing in an interlace recording mode. This demand has been increased not only against interlace recording mode printers but also against non-interlace recording mode printers.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a technique for improving image quality by correcting the paper feed error in a printer.
In order to attain the above object, the present invention executes prescribed processing in printing using a printing apparatus for printing by recording ink dots on a printing medium while moving a printing head in a main scanning direction. This printing apparatus comprises: a printing head including a plurality of nozzles arranged in a sub-scanning direction substantially perpendicular to a main scanning direction; a main scan drive unit configured to move the printing head in the main scanning direction, a sub-scan drive unit configured to move the printing medium in the sub-scanning direction by a plurality of intermittent feedings, a head driving unit configured to eject ink droplets from the nozzles while the main scan of the printing head, and a control unit configured to control the main scan drive unit, the sub-scan drive unit and the head driving unit.
With such the printing apparatus, a test pattern is formed on a printing medium. The test pattern includes a plurality of color patches printed in a plurality of printing modes, respectively. The test pattern is formed for selecting a printing mode from among the plurality of printing modes which are different each other in a sub-scan feed amount and/or an adjustment value for a sub-scan feed amount. Dots are recorded in accordance with a printing mode selected based on printing result of the test pattern.
With such an embodiment, image quality is improved by selecting the paper feed properly. This technique is described in many kinds of embodiment underneath.
(1) Pattern Printing in Interlace Printing Mode:
One embodiment for attaining the above object is as follows. That is a method for correcting the amount of sub-scan feed of the printing medium in a printing device which uses a print head that has a plurality of nozzles aligned in a row in the sub-scan direction, which is approximately perpendicular to the main scan direction, at a nozzle pitch of k times (k is an integer of 2 or greater) the dot pitch in the sub-scan direction, and which records ink dots on the printing medium while causing the print head to move in the main scan direction. The method comprises the steps of (a) printing, in accordance with an interlace recording mode, a test pattern that includes a plurality of color patches respectively printed using different correction values, as a test pattern for the purpose of determining the correction value of the sub-scan feed amount of the printing medium; and (b) correcting the sub-scan feed amount according to a correction value set in accordance with the printing results of the test pattern when the printing of images is performed in the interlace recording mode.
In this method, a test pattern that includes a plurality of color patches that are respectively printed using different correction values is printed according to the interlace recording mode, and the sub-scan feed amount is corrected using a correction value in accordance with the printing results of this test pattern. Accordingly, the sub-scan feed error of the printer that performs printing in an interlace recording mode can be corrected, so that the image quality is improved.
The step (a) may comprise the steps of as follows. These are (i) selecting N nozzles (N is an integer of 2 or greater) for each color among the plurality of nozzles as used nozzles; (ii) performing (k −1) scan sets each comprising a single main scan and a sub-scan feed by a first feed amount that is equal to the dot pitch in the sub-scanning direction, and then further performing a single main scan and a sub-scan feed by a second feed amount which is equal to {N×k−(k−1)} time the dot pitch; and (iii) printing the test pattern by repeatedly performing the step (ii).
In the test pattern that is printed by such a printing method, band-form areas of image deterioration called “banding” tend to be generated as a result of sub-scan feed error. Accordingly, if the correction value is determined using such a test pattern, the sub-scan feed error can be corrected so that banding tends not to occur.
It is preferable that the plurality of color patches are gray patches that are reproduced by composite black.
Composite black is reproduced using inks of the three hues CMY. The sub-scan feed error can be corrected with the ink dot trajectory error also taken into account; as a result, the mage quality can be further improved.
The plurality of color patches may be monochromatic patches that are reproduced using one ink among inks of black, cyan and magenta. The plurality of color patches may also be color patches of a secondary color that is reproduced using two inks among inks of three colors of cyan, magenta and yellow.
If inks with color components for which improvement of the image quality is especially desired are selected as the inks used to reproduce the color patches, the effect of the correction of the sub-scan feed error in improving the image quality is conspicuous.
(2) Pattern Printing in Given Ink Duty:
One embodiment for attaining the above object is
Otsuki Koichi
Yamasaki Keigo
Martine & Penilla LLP
Nguyen Thinh
Seiko Epson Corporation
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