Typewriting machines – Including selection of type-face by... – Including error detection
Reexamination Certificate
1999-11-18
2001-09-11
Hilten, John S. (Department: 2854)
Typewriting machines
Including selection of type-face by...
Including error detection
C358S001180
Reexamination Certificate
active
06287027
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an image printing apparatus and, more particularly, to an image correction system for correcting density nonuniformity between a plurality of heads or density nonuniformity between main-scanned images by a print head.
In recent years, image printing using inkjet print heads and thermal print heads as image printing apparatuses has rapidly being spread with the development of electronic video devices. Particularly, image printing using a high-speed printing multihead have been developed.
An image printing apparatus using a multihead prints an image by one head formed by adhering a plurality of print heads each having a plurality of nozzles.
FIG. 17A
shows an ideal image printing state by the multihead printing apparatus.
In
FIG. 17A
, upper black dots form an image printed by a head H
1
, whereas lower blank dots form an image printed by a head H
2
.
To form an adhered head so as to print a clear image, as shown in
FIG. 17A
, the heads H
1
and H
2
must be aligned with a very high precision.
However, if the heads H
1
and H
2
are excessively apart from each other at different angles, as shown in
FIG. 17B
, a blank stripe appears in an image corresponding to the joint between the heads H
1
and H
2
, or images printed by the upper and lower heads geometrically change.
If the heads H
1
and H
2
overlap each other at different angles, as shown in
FIG. 17C
, a black stripe appears in an image printed at the joint between the heads H
1
and H
2
.
To prevent this, the conventional multihead printing apparatus requires a long time for adjusting the head position, resulting in a high-cost multihead printing apparatus.
In the conventional multihead printing apparatus, even if heads are aligned with a high precision, printed images may overlap or be omitted at the boundary between one main-scanned image and the next main-scanned image owing to decentering of a roller for feeding a paper sheet serving as a printing medium, a slip of a paper sheet, and the like.
In the conventional multihead printing apparatus, the head position may change over time in accordance with the environment (temperature and humidity) of the printing apparatus and the like. For this reason, the image quality must be properly kept constant in accordance with the instantaneous state of printing.
To solve these problems, Jpn. Pat. Appln. KOKAI Publication No. 61-121658 discloses a printing apparatus wherein previous and current main-scanned images partially overlap each other, and an image is printed based on a predetermined pattern formed such that the previous and current scanned images become complementary to each other in this overlapping region.
The prior art disclosed in Jpn. Pat. Appln. KOKAI Publication No. 61-121658 can avoid to a certain degree a black or blank stripe generated in an image corresponding to the head joint. However, the heads must still be aligned with a high precision.
In addition, Jpn. Pat. Appln. KOKAI Publication No. 61-121658 does not disclose any multihead printing apparatus itself formed by adhering a plurality of heads.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above situation, and has as its object to provide an image correction system for a multihead image printing apparatus capable of greatly reducing the number of adjustment steps by coping with, by only electrical signal correction, even the attaching errors of a plurality of heads constituting a multihead.
It is another object of the present invention to provide an image correction system for a multihead image printing apparatus which can greatly reduce the number of adjustment steps by only electrical signal correction even when a plurality of heads constituting a multihead have attaching errors, and which corrects on-line the printing state which changes depending on changes over time and environmental changes.
To achieve the above objects, according to the present invention, there is provided
(1) an image correction apparatus for a printing apparatus which prints an image by scanning relatively a print head having a plurality of printing elements for forming dots to a printing medium, comprising:
a print head adhered a plurality of unit print heads having a plurality of printing elements for forming dots by overlapping partially at the printing elements in a scanning direction;
a correction unit for performing at least one correction processing of geometric correction, density nonuniformity correction, and color correction corresponding to positional shifts of the print head for input image signals corresponding to the plurality of print heads; and
a smoothing unit for changing a signal value at a portion corresponding to the overlapping region of the print head for the input image signals corresponding to the print head.
To achieve the above objects, according to the present invention, there is provided
(2) an image correction apparatus defined in (1), further comprising a plurality of print heads each other to print images of different colors.
To achieve the above objects, according to the present invention, there is provided
(3) an image correction apparatus defined in (1), wherein the apparatus further comprises:
a test image storage unit for storing a predetermined test image;
an image reader unit for reading a printed image obtained by printing the predetermined test image from the test image storage unit by the heads;
a parameter calculation unit for calculating parameters used for geometric correction, density nonuniformity correction, and color correction by the correction unit from image data read by the image reader unit; and
a storage unit for storing the parameters calculated by the parameter calculation unit, and the correction unit performs correction processing using the parameters stored in the storage unit.
To achieve the above objects, according to the present invention, there is provided
(4) an image correction apparatus defined in (2), wherein the apparatus further comprises:
a test image storage unit for storing a predetermined test image;
an image reader unit for reading a printed image obtained by printing the predetermined test image from the test image storage unit by the heads;
a parameter calculation unit for calculating parameters used for geometric correction, density nonuniformity correction, and color correction by the correction unit from image data read by the image reader unit; and
a storage unit for storing the parameters calculated by the parameter calculation unit, and the correction unit performs correction processing using the parameters stored in the storage unit.
To achieve the above objects, according to the present invention, there is provided
(5) an image correction apparatus for a printing apparatus which prints an image by scanning relatively a print head having a plurality of printing elements for forming dots to a printing medium, comprising:
means for causing the print head to ensure partially overlapping a region printed by one scanning and a region printed by next scanning;
a correction unit for performing at least one correction processing of predetermined geometric correction, density nonuniformity correction, and color correction corresponding to positional shifts of the print head for input image signals corresponding to the print head; and
a smoothing unit for changing a signal value at a portion corresponding to the overlapping region for the input image signals corresponding to the print head.
To achieve the above objects, according to the present invention, there is provided
(6) an image correction apparatus defined in (5), further comprising a plurality of print heads each other to print images of different colors.
To achieve the above objects, according to the present invention, there is provided
(7) an image correction apparatus defined in (5), wherein the apparatus further comprises:
a test image storage unit for storing a predetermined test image;
an image reader unit for reading a printed image obtained by printing the predetermined test image
Ioka Ken
Komiya Yasuhiro
Omata Yoshinobu
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Hilten John S.
Nolan, Jr. Charles H.
Olympus Optical Co,. Ltd.
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