Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-07-24
2002-08-20
Nguyen, Lamson D. (Department: 2661)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S041000, C347S015000
Reexamination Certificate
active
06435656
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a recording device. More particularly, the invention relates to a recording device which has a recording head including an array consisting of an N (N =a positive integer) number of dot forming elements, which are arrayed at a fixed spatial interval D in a secondary scanning operation as a recording-medium feeding direction, a head drive means for driving dot forming elements, a primary scan drive means for reciprocatively moving the recording head relative to a recording medium in a primary scanning operation, which is orthogonal to the secondary scanning operation, and a secondary scan drive means for feeding a recording medium relative to the recording head in the secondary scanning operation, wherein the recording head records an image while scanning a surface of a recording medium in primary and secondary scanning operations.
The present application is based on Japanese Patent Applications No. 2000-226277 and 2001-220944, which are incorporated herein by reference.
2. Description of the Related Art
A typical example of the recording method for improving the print quality of the ink jet printer is disclosed in Unexamined Japanese Patent Publication No. Hei. 9-169109. This recording method is constructed by combining a partial overlapping method into an “interlacing method” described in U.S. Pat. No. 4,198,642 and Unexamined Japanese Patent Publication No. Sho. 53-2040. The “partial overlapping method” is a recording method in which a part of a raster is recorded by using different inkjet nozzles (referred to simply as “nozzles”) through a plural number of primary scanning operations, and another part of the raster is recorded by using one nozzle through one primary scanning operation. In the specification description, the raster which is recorded by using different nozzles through a plural number of primary scanning operations, will be referred to as an “overlapping raster”, and the raster which is recorded by using one nozzle through one primary scanning operation, will be referred to as a “non-overlapping raster”.
In the overlapping raster, a plurality of nozzles used for raster formation are intermittently driven to eject ink drops. Accordingly, the recording head is driven at a drive frequency being different from that in the non-overlapping raster.
The recording head has a frequency characteristic proper to it. The frequency characteristic of the recording head may be expressed in the form of a characteristic variation of a quantity of an ink drop (ink ejection quantity) ejected from each nozzle of the recording head with respective to a drive frequency at which the recording head is driven. An example of the frequency characteristic of the recording head is shown in FIG.
3
. In the graph, the abscissa represents a drive frequency (kHZ) and the ordinate represents an ink ejection quantity (ng=nano gram). As seen from the characteristic curve, to form dots at dot forming positions arrayed successively in the primary scanning operation, the recording head having that frequency characteristic is driven at a maximum drive frequency (=17 kHz) to eject ink drops, each of which has a quantity of 19 ng, from the nozzles to form dots at those positions. To form dots every other dot forming position, the recording head is driven at the half of the maximum drive frequency (=8.5 kHz), and a quantity of each of the ink drops ejected from the nozzles is 15.5 ng.
To form dots at dot forming positions arrayed successively, in the case of the non-overlapping raster, the recording head is driven at 17 kHz (maximum drive frequency) and causes it to eject ink drops each of 19 ng in quantity. In the case of the overlapping raster, to form dots every other dot by using two different nozzles, the recording head is driven at 8.5 kHz to eject ink drops each of 15.5 ng through the nozzles.
For this reason, where the recording head has the
FIG. 3
frequency characteristic is used, the total ink ejection quantity of the non-overlapping raster is smaller than that of the overlapping raster. Where the ink quantity is small, the diameter of a formed dot is also small and sometimes, it is seen in different color under influence of other color dots. As a result, the overlapping raster is seen standing out of the non-overlapping raster. In other words, a stripe pattern appears on the picture. This problem is more serious as the number of the overlapping rasters successively formed increases.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to lessen such an unwanted phenomenon that the overlapping raster stands out of the non-overlapping raster in the partial overlapping recording method, and hence to improve the picture quality.
Another object of the present invention is to make inconspicuous the displacement of the dots from their proper positions, which is caused by a head movement error when the recording head is moved in the secondary scanning operation, in the interlacing method.
To achieve the above object, there is provided a first recording device having a recording head including an array consisting of an N (N=a positive integer) number of dot forming elements, which are arrayed at a fixed spatial interval D in a secondary scanning operation as a recording-medium feeding direction, a head drive means for driving dot forming elements, a primary scan drive means for reciprocatively moving the recording head relative to a recording medium in a primary scanning operation, which is orthogonal to the secondary scanning operation, and a secondary scan drive means for feeding a recording medium relative to the recording head in the secondary scanning operation, wherein the recording head records an image while scanning a surface of a recording medium in primary and secondary scanning operations, the improvement being characterized in that the secondary scan drive means determines a secondary scan distance of feeding the recording medium by one secondary scan drive so that the dot forming positions of an M (M=positive integer smaller than N/2) number of upstream dot forming elements, which are located in the upstream end of the dot forming element array as viewed in the secondary scanning operation, in a primary scanning operation, are coincident with the dot forming positions of an M number of downstream dot forming elements, which are located at the downstream end of the dot forming element array in a primary scanning operation after a predetermined number of primary scanning operations are performed, and the head drive means intermittently drives the upstream and downstream dot forming elements so as to form dots exactly at the dot forming positions on the same primary scan line, viz., without doubly forming the dots at the same dot forming position and the formation of no dot at its forming position, and drives the upstream dot forming elements so as to more frequently form the dot toward the upstream side and drives the downstream dot forming elements so as to more frequently form the dot toward the downstream side.
According to another aspect, there is provided a second recording device having a recording head including an array consisting of an N (N=a positive integer) number of dot forming elements, which are arrayed at a fixed spatial interval D in a secondary scanning operation as a recording-medium feeding direction, a head drive means for driving dot forming elements, a primary scan drive means for reciprocatively moving the recording head relative to a recording medium in a primary scanning operation, which is orthogonal to the secondary scanning operation, and a secondary scan drive means for feeding a recording medium relative to the recording head in the secondary scanning operation, wherein the recording head records an image while scanning a surface of a recording medium in primary and secondary scanning operations, the improvement being characterized in that the secondary scan drive means determines a secondary scan di
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