U.S. patent application number 09/189722 was filed with the patent office on 2001-08-09 for printing apparatus and a printing method.
Invention is credited to KANDA, HIDEHIKO, KANEMATSU, DAIGORO, NAKAJIMA, YOSHINORI, ONO, MITSUHIRO.
Application Number | 20010012033 09/189722 |
Document ID | / |
Family ID | 26567806 |
Filed Date | 2001-08-09 |
United States Patent
Application |
20010012033 |
Kind Code |
A1 |
ONO, MITSUHIRO ; et
al. |
August 9, 2001 |
PRINTING APPARATUS AND A PRINTING METHOD
Abstract
In a multipass printing using a print head which has a plurality
of staggered columns of print elements, one and the same print line
is formed by using nozzles (k1-129, k2-1) of different nozzle
columns (k1, k2) to disperse the directivity of landing deviations
of dots in the same print line.
Inventors: |
ONO, MITSUHIRO;
(KAWASAKI-SHI, JP) ; KANEMATSU, DAIGORO;
(KAWASAKI-SHI, JP) ; KANDA, HIDEHIKO;
(KAWASAKI-SHI, JP) ; NAKAJIMA, YOSHINORI;
(YOKOHAMA-SHI, JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Family ID: |
26567806 |
Appl. No.: |
09/189722 |
Filed: |
November 12, 1998 |
Current U.S.
Class: |
347/41 |
Current CPC
Class: |
B41J 2/145 20130101;
G06K 15/107 20130101 |
Class at
Publication: |
347/41 |
International
Class: |
B41J 002/145; B41J
002/15 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 14, 1997 |
JP |
09-314057 |
Nov 9, 1998 |
JP |
09-318085 |
Claims
What is claimed is:
1. A printing apparatus using a print head to perform printing,
comprising: main scan means for scanning the print head relative to
a recording medium in a main scan direction; sub-scan means for
scanning the recording medium relative to the print head in a
sub-scan direction different from the main scan direction; and
control means for controlling to main-scan the print head a
plurality of times over the same print line on the recording medium
with at least one sub-scan operation interposed between the main
scan operations to print the line, the print head having a
plurality of staggered columns of print elements; wherein the
control means controls to use the print elements of different
columns to complete the printing of the same print line.
2. A printing apparatus as claimed in claim 1, wherein the print
elements comprise print elements for an ink-jet printing
system.
3. A printing apparatus as claimed in claim 1, wherein odd-numbered
columns of the print elements and even-numbered columns of the
print elements are staggered with respect to each other.
4. A printing apparatus as claimed in claim 3, wherein the control
means controls to scan comprise the print head two times over the
same print line by interposing between the main scan operations the
sub-scan operation which advances the recording medium by a
distance equal to one-half the length of the print element columns
plus or minus one-half the print element interval.
5. A printing apparatus as claimed in claim 3, wherein the control
means controls to scan the print head two times over the same print
line by interposing between the main scan operations the sub-scan
operations which advances the recording medium by a distance equal
to one fourth the length of the print element columns plus or minus
one-half the print element interval.
6. A printing apparatus as claimed in claim 3, wherein the
odd-numbered columns and the even-numbered columns of the print
elements each are used an odd number of print elements for
printing, and the control means controls to scan the print head two
times over the same print line by interposing between the main scan
operations the sub-scan operation which advances the recording
medium by a distance equal to one-half the length of the print
element columns.
7. A printing apparatus as claimed in claim 3, wherein the
odd-numbered columns and the even-numbered columns of the print
elements each comprise four times an arbitrary odd number of print
elements, and the control means controls to scan the print head
four times over the same print line by interposing between the main
scan operations the sub-scan operation which advances the recording
medium by a distance equal to one fourth the length of the print
element columns.
8. A printing apparatus as claimed in claim 3, wherein the
odd-numbered columns and the even-numbered columns of the print
elements each comprise n times an arbitrary odd number of print
elements, and the control means controls to scan the print head n
times over the same print line by interposing between the main scan
operations the sub-scan operation which advances the recording
medium by a distance equal to one n-th the length of the print
element columns where n is an arbitrary natural number other than
1.
9. A printing apparatus as claimed in claim 1, said printing
apparatus is capable of color printing and has a plurality of
columns of print elements for each print color.
10. A printing method using a print head to perform printing,
comprising the steps of: moving the print head relative to a
recording medium in a main scan direction; moving the recording
medium relative to the print head in a sub-scan direction different
from the main scan direction; and controlling to main-scan the
print head a plurality of times over one and the same print line on
the recording medium with at least one sub-scan operation
interposed between the main scan operations to print the line, the
print head having a plurality of staggered columns of print
elements; wherein the print elements of different columns are used
to complete the printing of the same print line.
11. A printing method as claimed in claim 10, wherein the print
elements comprise print elements for an ink-jet printing
apparatus.
12. A printing method as claimed in claim 10, wherein odd-numbered
columns of the print elements and even-numbered columns of the
print elements comprise staggered with respect to each other.
13. A printing method as claimed in claim 12, wherein the control
step controls to scan the print head two times over the same print
line by interposing between the main scan operations the sub-scan
operation which advances the recording medium by a distance equal
to one-half the length of the print element columns plus or minus
one-half the print element interval.
14. A printing method as claimed in claim 12, wherein the control
steps controls to scan the print head two times over the same print
line by interposing between the main scan operations the sub-scan
operations which advances the recording medium by a distance equal
to one fourth the length of the print element columns plus or minus
one-half the print element interval.
15. A printing method as claimed in claim 12, wherein the
odd-numbered columns and the even-numbered columns of the print
elements each are used an odd number of print elements for
printing, and the control step controls to scan the print head two
times over the same print line by interposing between the main scan
operations the sub-scan operation which advances the recording
medium by a distance equal to one-half the length of the print
element columns.
16. A printing method as claimed in claim 12, wherein the
odd-numbered columns and the even-numbered columns of the print
elements each comprise four times an arbitrary odd number of print
elements, and the control step controls to scan the print head four
times over the same print line by interposing between the main scan
operations the sub-scan operation which advances the recording
medium by a distance equal to one fourth the length of the print
element columns.
17. A printing method as claimed in claim 12, wherein the
odd-numbered columns and the even-numbered columns of the print
elements each comprise n times an arbitrary odd number of print
elements, and the control means controls to scan the print head n
times over the same print line by interposing between the main scan
operations the sub-scan operation which advances the recording
medium by a distance equal to one n-th the length of the print
element columns where n is an arbitrary natural number other than
1.
18. A printing method as claimed in claim 10, the printing method
is capable of color printing and has a plurality of columns of
print elements for each print color.
Description
[0001] This application is based on Patent Application Nos.
314,057/1997 filed on Nov. 14, 1997 in Japan and 318,085/1998 filed
on Nov. 9, 1998 in Japan, the content of which is incorporated
hereinto by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a printing apparatus and a
printing method that are applicable to any apparatuses for printing
recording mediums, such as paper, cloth, nonwoven fabric and OHP,
and more specifically to a printing apparatus and a printing method
which are most suitable for an inkjet printing apparatus installed
in a variety of office equipment and mass-produced apparatuses such
as printers, copying machines and facsimiles.
[0004] 2. Description of the Prior Art
[0005] An ink-jet printing apparatus for printing recording mediums
such as paper, cloth, plastic sheets and OHP sheets has been
commercialized as an output means of information processing
systems, for example as a printer for copying machines, facsimiles,
electronic typewriters, word processors and workstations, or as a
handy or portable printer used on personal computers, host
computers, optical disk drives and video tape recorders.
[0006] The ink-jet printing apparatus in the above case has a
structure corresponding to part of these equipment, or incorporated
into their unique functions. Generally, the ink-jet printing
apparatus comprises a carriage mounting a recording means (print
head) and an ink tank; a feeding means to feed print paper; and a
control means to control the recording means and the feeding means.
The print head that ejects an ink from a plurality of nozzles is
serially scanned in a direction (hereinafter referred to as a main
scan direction) perpendicular to the print paper feeding direction
(a sub-scan direction) and at the same time the print paper is
intermittently advanced by a distance equal to a recording width
during non-printing periods. This method delivers ink onto the
print paper according to a print signal to perform printing and has
found a wide range of applications as a low-noise recording system
with a small running cost.
[0007] Because the print head has many ink ejecting nozzles
arranged in line in the sub-scan direction, scanning the print head
over the print paper results in the paper being printed in a width
corresponding to the number of nozzles, thus assuring high-speed
printing.
[0008] In recent years, a device has been in use that includes a
plurality of print heads for three to four colors to form
full-color images. This device can mount four print heads and four
ink tanks corresponding to three primary colors--yellow (Y),
magenta (M) and cyan (C)--and black (B).
[0009] A recent trend of the ink-jet printer is for reducing the
size of ink droplets to enhance the printed image quality to cope
with high-speed printing and photograph printing. The reduced size
of ink droplets requires enhanced landing precision. It is,
however, unavoidable that the actual landing points of the ink
droplets are deviated from ideal landing positions.
[0010] To deal with this problem, Japanese Patent Laid-Open Nos.
214,670/1985 and 214,671/1985, and U.S. Pat. Nos. 4,963,882 and
4,967,203 offer a multipass recording method. In this recording
method, the image data is divided into predetermined arrays for
first and second scans so that the first-scan array and the
second-scan array complement each other. Generally, the divided
arrays of the pixels are like a hound's-tooth check pattern in the
vertical and lateral directions as shown in FIG. 1 and the material
to be printed is fed intermittently when the printing is not
performed. FIG. 1 represents pixels in the form of squares in a
grid and the numbers indicate in which scan the ink will be ejected
onto the corresponding pixels. With the multipass recording,
because one line is formed of ink droplets ejected from different
nozzles, variations that depend on the nozzles can be reduced.
[0011] There is also a printing apparatus which has a plurality of
columns of ink ejecting nozzles to improve the printing resolution
for higher image quality. In this case, the deviations between the
ink droplet actual landing positions and the ideal landing
positions differ from one nozzle column to another. In other words,
the same nozzle column will produce the similar landing deviations.
The inventor of this invention has found that if only the nozzles
of the same nozzle column are used in each scan line to form an
image, an unevenness of an image by the nozzle is reduced, but an
unevenness of the image by the nozzle column is reduced at all, and
this results in large unevenness of an image during the
quantization process, causing significant image quality degradation
in some cases.
[0012] This is explained by taking an example shown in FIGS. 2
through 5. FIG. 2 shows a print head having columns of nozzles n1,
n2, the nozzle column n1 ranging from nozzle n1-1 to nozzle n1-256
and the nozzle column n2 from nozzle n2-1 to nozzle n2-256. Let us
consider a case where the nozzles n1-1 to n1-256 of the nozzle
column n1 have ink landing points that tend to deviate to the right
from ideal landing points and the nozzles n2-1 to n2-256 of the
nozzle column n2 have ink landing points that tend to deviate to
the left from ideal landing points. It is assumed that a print
pattern as shown in FIG. 3 is printed by a 1-raster-2-pass
multipass printing. With the division method used by this multipass
printing, ink dots are thinned out to form a hound's-tooth check
pattern described above. FIG. 3 represents pixels in the form of
squares in a grid and dots in the form of circles. When there are
no deviations between the actual landing points and the ideal
landing points, the image produced will have a uniform dot
distribution as shown in FIG. 3. In the case under consideration,
however, the image obtained will be as shown in FIG. 4. This is
because the landing positions of odd-numbered lines of dots
produced by the nozzle column n1 are deviated to the right on the
sheet of the figure and because the landing positions of
even-numbered lines of dots produced by the nozzle column n2 are
deviated to the left. The directions of deviations of the landing
points are shown in FIG. 5, from which it is seen that the
deviation direction changes for each line.
[0013] Hence, when the multipass recording is performed by the
print head which has a plurality of staggered columns of print
elements, an actual printed image looks to have a slantwise
texture, different from the one that is originally intended to be
represented.
SUMMARY OF THE INVENTION
[0014] An object of this invention is to provide a printing
apparatus and a printing method, which can form an image strictly
according to what is intended to be represented by the image data
even when a multipass printing is performed by a print head which
has a plurality of staggered columns of print elements.
[0015] The present invention provides a printing apparatus using a
print head. The printing apparatus may comprise a main scan means
to move the print head relative to a recording medium in a main
scan direction; a sub-scan means to move the recording medium
relative to the print head in a sub-scan direction different from
the main scan direction; and a control means to main-scan the print
head a plurality of times over one and the same print line on the
recording medium with at least one sub-scan operation interposed
between the main scan operations to print the line, the print head
having a plurality of staggered columns of print elements; wherein
the control means uses the print elements of different columns to
complete the printing of the same print line.
[0016] According to the invention, the print elements may be print
elements for ink-jet printing system.
[0017] According to the invention, odd-numbered columns of the
print elements and even-numbered columns of the print elements may
be staggered with respect to each other.
[0018] According to the invention, the control means may scan the
print head two times over the same print line by interposing
between the main scan operations the sub-scan operation which
advances the recording medium by a distance equal to one-half the
length of the print element columns plus or minus one-half the
print element interval.
[0019] According to the invention, the control means may scan the
print head two times over the same print line by interposing
between the main scan operations the sub-scan operations which
advances the recording medium by a distance equal to one fourth the
length of the print element columns plus or minus one-half the
print element interval.
[0020] According to the invention, the odd-numbered columns and the
even-numbered columns of the print elements each may use an odd
number of print elements for printing, and the control means may
scan the print head two times over the same print line by
interposing between the main scan operations the sub-scan operation
which advances the recording medium by a distance equal to one-half
the length of the print element columns.
[0021] According to the invention, the odd-numbered columns and the
even-numbered columns of the print elements each may comprise four
times an arbitrary odd number of print elements, and the control
means may scan the print head four times over the same print line
by interposing between the main scan operations the sub-scan
operation which advances the recording medium by a distance equal
to one fourth the length of the print element columns.
[0022] According to the invention, the odd-numbered columns and the
even-numbered columns of the print elements each may comprise n
times an arbitrary odd number of print elements, and the control
means may scan the print head n times over the same print line by
interposing between the main scan operations the sub-scan operation
which advances the recording medium by a distance equal to one n-th
the length of the print element columns where n is an arbitrary
natural number other than 1.
[0023] According to the invention, the printing apparatus may be
capable of color printing and have a plurality of columns of print
elements for each print color.
[0024] According to the invention, the printing method using a
print head to perform printing may comprise the steps of: moving
the print head relative to a recording medium in a main scan
direction; moving the recording medium relative to the print head
in a sub-scan direction different from the main scan direction; and
controlling to main-scan the print head a plurality of times over
one and the same print line on the recording medium with at least
one sub-scan operation interposed between the main scan operations
to print the line, the print head having a plurality of staggered
columns of print elements; wherein the print elements of different
columns are used to complete the printing of the same print
line.
[0025] According to the invention, the print elements may be print
elements for an ink-jet printing apparatus.
[0026] According to the invention, odd-numbered columns of the
print elements and even-numbered columns of the print elements may
be staggered with respect to each other.
[0027] According to the invention, the control step may scan the
print head two times over the same print line by interposing
between the main scan operations the sub-scan operation which
advances the recording medium by a distance equal to one-half the
length of the print element columns plus or minus one-half the
print element interval.
[0028] According to the invention, the control steps may scan the
print head two times over the same print line by interposing
between the main scan operations the sub-scan operations which
advances the recording medium by a distance equal to one fourth the
length of the print element columns plus or minus one-half the
print element interval.
[0029] According to the invention, the odd-numbered columns and the
even-numbered columns of the print elements may each use an odd
number of print elements for printing, and the control step may
scan the print head two times over the same print line by
interposing between the main scan operations the sub-scan operation
which advances the recording medium by a distance equal to one-half
the length of the print element columns.
[0030] According to the invention, the odd-numbered columns and the
even-numbered columns of the print elements may each comprise four
times an arbitrary odd number of print elements, and the control
step may scan the print head four times over the same print line by
interposing between the main scan operations the sub-scan operation
which advances the recording medium by a distance equal to one
fourth the length of the print element columns.
[0031] According to the invention, the odd-numbered columns and the
even-numbered columns of the print elements may each comprise n
times an arbitrary odd number of print elements, and the control
means may scan the print head n times over the same print line by
interposing between the main scan operations the sub-scan operation
which advances the recording medium by a distance equal to one n-th
the length of the print element columns where n is an arbitrary
natural number other than 1. This invention may be capable of color
printing and have a plurality of columns of print elements for each
print color.
[0032] According to the invention, because the printed dots
representing one and the same line are formed by ink droplets
ejected from the nozzles of different nozzle columns, the degree to
which the dot landing deviations have a directivity in the line can
be alleviated. As a result, when an image is formed by using nozzle
columns whose ink droplet landing positions will deviate, it is
possible to prevent unintended textures from appearing in the
printed image.
[0033] The above and other objects, effects, features and
advantages of the present invention will become more apparent from
the following description of embodiments thereof taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 is a schematic diagram showing the print positions
allocated in a hound's-tooth check pattern;
[0035] FIG. 2 is an external front view of a conventional print
head;
[0036] FIG. 3 is a schematic diagram showing ideal dot landing
positions;
[0037] FIG. 4 is a schematic diagram showing a conventional output
image;
[0038] FIG. 5 is a schematic diagram showing the directions of
landing deviations of dots on a recording medium produced by the
conventional apparatus;
[0039] FIG. 6 is a schematic view showing an outline construction
of the ink-jet printer as one embodiment of this invention;
[0040] FIG. 7 is a schematic, external front view of the print head
of the embodiment of this invention;
[0041] FIG. 8 is a schematic diagram showing the directions of
landing deviations of dots on a recording medium produced by the
embodiment of this invention;
[0042] FIG. 9 is a schematic diagram showing the process of forming
dots in the embodiment of this invention;
[0043] FIG. 10 is a schematic diagram showing the process of
forming dots in the embodiment of this invention;
[0044] FIG. 11 is a schematic diagram showing the print position
allocation (selection) block of a second embodiment of this
invention;
[0045] FIG. 12 is a schematic diagram showing the directions of
landing deviations of dots on a recording medium produced by the
second embodiment of this invention;
[0046] FIG. 13 is a schematic diagram showing an output image in
the second embodiment of this invention;
[0047] FIG. 14 is a schematic, external front view of the print
head of a third embodiment of this invention;
[0048] FIG. 15 is a schematic diagram showing dot landing positions
on the recording medium in a third embodiment of this
invention;
[0049] FIG. 16 is a schematic diagram showing the directions of
landing deviations of dots on the recording medium produced by the
third embodiment of this invention;
[0050] FIG. 17 is a schematic diagram showing the dot landing
positions on the recording medium in the conventional example;
[0051] FIG. 18 is a table of print modes in a fourth embodiment of
this invention; and
[0052] FIG. 19 is a block diagram showing the configuration of a
control circuit used in the above embodiments of this
invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0053] Now, embodiments of the present invention will be described
in detail by referring to the accompanying drawings.
[0054] (Embodiment 1)
[0055] A first embodiment will be explained by referring to FIGS. 6
to 9. FIG. 6 shows an outline configuration of an example ink-jet
printer that can apply the present invention. This printer has a
print head 1 as shown in FIG. 7. The print head 1 has nozzle
columns k1, k2 for ejecting a black ink, nozzle columns c1, c2 for
a cyan ink, nozzle columns m1, m2 for a magenta ink, and nozzle
columns y1, y2 for a yellow ink. It also has a flexible cable 2 to
supply an electric signal from the printer body to the print head,
a cap unit 3 to recover the ink ejection function, a paper feed
tray 5 to supply a recording material (recording medium such as
paper) 4. The printer with the above construction serially scans
the print head 1 in a direction (main scan direction) B
perpendicular to the feed direction A of the recording material 4
to perform printing in a width corresponding to the number of
nozzles. At the same time, the printer intermittently feeds the
recording material by a distance equal to the recording width
during the non-printing periods.
[0056] The nozzle columns k1, k2, c1, c2, m1, m2, y1, y2 are each
formed of 256 nozzles arranged at a density of 300 nozzles per
inch, each of which delivers about 20 ng of ink. The nozzle columns
k1, k2 are staggered from each other by {fraction (1/600)} inch.
They are spaced 30 nozzles or 0.1 inch apart in the main scan
direction. Thus, the print density in the sub-scan direction is 600
dpi (dot per inch) and the printer is so constructed that the print
density in the main scan direction will also be 600 dpi. The
similar construction is employed also for c1-c2, m1-m2, and y1-y2
and the printer is constructed so that the print densities for
these nozzles in the main scan direction will also be 600 dpi.
[0057] For black-and-white (monochromatic) printing, an input image
is digitized by a quantization process that spreads errors in the
lateral direction. The printing method employed is a multipass
printing and one raster is formed by two nozzles of different
nozzle columns. Because this embodiment is characterized by the
order of driving the nozzles (print elements), the following
explanation assumes that all pixels of the image data are printed
(or painted solid black). FIG. 1 shows the number of passes
required for the corresponding pixels to be formed.
[0058] After the recording material 4 is fed to a print start
position, a first scan is performed. First, nozzles k1-129 to
k1-256 of the first nozzle column in FIG. 7 are driven to print
odd-numbered pixels of a first vertical column. The deviation
direction of the dot landing positions and the nozzle numbers are
shown in FIG. 8. As can be seen from FIG. 8, the dot landing
positions for all of the pixels of the first column are deviated to
the right in FIG. 8. Next, nozzles k2-129 to k2-256 of the second
nozzle column are driven to print even-numbered pixels of a second
column. Further, the print head 1 is moved in the main scan
direction to the third column of pixels in FIG. 8, odd-numbered
pixels of a third column is printed by the same nozzle column that
was used for the first dot column. In this way, the print head 1
successively prints the odd-numbered columns of pixels as it moves
in the main scan direction.
[0059] When the print head 1 arrives at the carriage return
position, the print head 1 returns to the print start position in
the main scan direction. During this period the recording material
4 is fed about half the length of the nozzle column, or more
precisely 127-and-half nozzles when viewed from one nozzle column
in the example of FIG. 7. If the recording material 4 were fed by
the distance equal to 128 nozzles, the nozzle k1-129 would assume
the same position as the nozzle k1-1. But because the actual feed
is {fraction (1/2)} nozzle short, the nozzle k1-129 is located at
the same position as the nozzle k2-1. Then, to print the same line
on the recording material 4 that was previously printed, the nozzle
columns of k1-2 to k1-129 and k2-1 to k2-128 are driven to perform
the second multipass printing. In the conventional printer, the
same line is printed by only the nozzle column k1 or k2, whereas
this embodiment uses both of the nozzle columns k1 and k2 in
printing the same line. For reference, FIG. 10 shows the print head
position (shown to the left) and the correspondence between the
positions of dots printed on the recording medium 100 by the print
head and the nozzle numbers. The numbers assigned to the recording
medium 100 correspond to the nozzle numbers of the print head. In
the second printing, the nozzles k1-130 to k1-256 and k2-129 to
k2-256 are printing the next band. Here only the uppermost line is
shown.
[0060] The columns of nozzles k1-2 to k1-129 and k2-1 to k2-128,
after printing at the first and second columns of pixel positions
in FIG. 8, proceed to print at the third and fourth columns of
pixels and then the fifth and sixth columns and so on, two columns
of odd-numbered and even-numbered columns at a time.
[0061] As described above, because the directions of dot landing
deviations produced by the second nozzle column are opposed to
those produced by the first nozzle column, performing the second
pass of the multipass printing will make the dot landing deviation
directions of the odd-numbered and even-numbered columns of pixel
positions face each other as shown in FIG. 8. As a result, the
adjacent odd-numbered and even-numbered columns of dots are closer
together as shown in FIG. 9, thus preventing the printed image from
appearing to have a slantwise texture as it would in the
conventional printer as shown in FIG. 4. Because the multipass
printing described above prints the same line by using different
nozzle columns (first and second columns of nozzles), the distance
by which the recording medium is advanced in the sub-scan direction
is not always constant. The recording medium is sub-scanned by a
distance equal to 128 plus or minus {fraction (1/2)} nozzles. The
nozzle column k2 is driven early compared with the nozzle column k1
to the extent that the nozzle column k2 is positioned further to
the right in the main scan direction than k1.
[0062] In selecting the nozzles of the print head 1 according to
the ink-jet printing method described above a known drive circuit
may be used, and a person skilled in the art should be able to
manufacture a drive control circuit to drive the nozzles in the
above-described order. The drive control circuit may have a
gate-array configuration or use a CPU. For example, the nozzles to
be used in each scan can virtually be selected by masking the data
for other than the pixels of the present scan number.
[0063] (Embodiment 2)
[0064] Next, the second embodiment of this invention will be
described by referring to FIGS. 11 and 12.
[0065] FIG. 11 shows the correspondence between the block of the
print head 1 and the print positions. In FIG. 11 the vertical axis
represents a line position and the horizontal axis a pixel
position. The numbers in a matrix of FIG. 11 indicate in which pass
the corresponding pixels are formed.
[0066] While the embodiment 1 prints one line in two scans, the
embodiment 2 prints one line in four scans. At the first column,
fifth column, ninth column, . . . of pixel positions during the
first scan, odd-numbered nozzles of an odd-numbered nozzle column
(k1-193, 195, . . . , 255) are selected to print one line only.
[0067] During the first scan, at the second column, sixth column,
tenth column, . . . of pixel positions, odd-numbered nozzles of an
even-numbered nozzle column (k2-193, 195, . . . , 255) are selected
(used). Similarly, at the third column, seventh column, . . . of
pixel positions, even-numbered nozzles of an odd-numbered nozzle
column (k1-194, 196, . . . , 256) are selected. At the fourth
column, eighth column, . . . of pixel positions, even-numbered
nozzles of an even-numbered column (k2-194, 196, . . . , 256) are
selected. In this way, pixels are formed at positions indicated by
"1" in FIG. 11 during the first scan.
[0068] Then, the recording material (print paper) is sub-scanned by
a distance equal to 63 and {fraction (1/2)} nozzles to start the
second scan. At this time, if the paper were advanced 64 nozzles,
the nozzle k1-193 would assume the same position as the nozzle
k1-129. The actual advance, however, is {fraction (1/2)} nozzle
short, so that the nozzle k1-193 assumes the same position as the
nozzle k2-129.
[0069] At the first column, fifth column, . . . of pixel positions,
odd-numbered nozzles of an odd-numbered nozzle column (k1-131, 133,
. . . , 255) are selected during the second scan. The second scan
forms the pixels at positions indicated by "2" in FIG. 11. The
third scan forms the pixels at positions indicated by "3" and the
fourth scan by "4." The sub-scan feeds during the second and third
scans are 64 plus {fraction (1/2)} nozzles and those during the
third and fourth scans are 63 plus {fraction (1/2)} nozzles. That
is, the sub-scans amounting to 64+1/2 nozzles and 64-1/2 nozzles
are repeated.
[0070] While the above multipass printing is performed, the first
or second nozzle column in other areas is performing the multipass
printing on other lines.
[0071] In this embodiment, too, because the nozzle columns are
selected so that the directions of landing deviations of dots
formed by the first and second nozzle columns during the multipass
printing on the same line are opposed to each other (see FIGS. 12
and 13), a slantwise texture found in the conventional printer does
not appear. For reference, dot landing positions of an output image
in the second embodiment are shown in FIG. 13. When the multipass
printing is being performed at an intermediate position of the
print paper, for example on a line in one area of the print head,
the multipass printing is also being carried out on lines in other
areas of the print head.
[0072] (Embodiment 3)
[0073] Next, a third embodiment will be explained by referring to
FIGS. 14 through 17. This embodiment uses a print head 8 as shown
in FIG. 14, which differs in the number of nozzles from the print
head 1 of the first embodiment. The nozzle columns k1, k2, c1, c2,
m1, m2, y1, y2 each comprise 127 nozzles arranged at a density of
300 nozzles per inch.
[0074] The total number of nozzles for each color therefore is 254.
For the print head with 128 nozzles in each column, 127 out of 128
nozzles can be used.
[0075] FIG. 15 shows the correspondence between the nozzle columns
of the print head 8 and the pixel positions printed on the
recording medium. Although in the actual printer it is the
recording medium that is fed, FIG. 15 shows the print head to be
shifted for simplicity. First, after the recording material 4 is
fed to the print position, the first scan is performed. The nozzles
of the first nozzle column k1-65 to k1-127 are driven to print
odd-numbered pixels of the first vertical column. The directions of
landing deviations of dots and the corresponding nozzle numbers
during this printing are shown in FIG. 16. As can be seen from FIG.
16, all of the dots landing on the pixels of the first column are
deviated to the right. Next, nozzles of the second column k2-64 to
k2-127 are driven to print even-numbered pixels of the second
column. When the print head 8 moves in the main scan direction to
the third pixel column, the nozzle column that was used on the
first column is driven to print odd-numbered pixels of the third
column. In this way, the print head 8 successively prints at the
odd-numbered pixel positions while moving in the main scan
direction.
[0076] When the print head 8 reaches the carriage return position,
it returns to the print start position in the main scan direction.
In the mean time, the recording material 4 is advanced in the
sub-scan direction by a distance equal to half the length of the
nozzle column or, more precisely, 63.5 nozzles when seen from one
nozzle column in the example of FIG. 16. The numbers assigned to
the recording medium correspond to the nozzle numbers of the print
head. In the second printing, nozzles k1-65 to k1-127, k2-64 to
k2-127 are printing on the next band. Only the uppermost line is
shown here.
[0077] As described above, because the directions of dot landing
deviations produced by the second nozzle column are opposed to
those produced by the first nozzle column, performing the second
pass of the multipass printing will make the dot landing deviation
directions of the odd-numbered and even-numbered columns of pixel
positions face each other as shown in FIG. 16. As a result, the
adjacent odd-numbered and even-numbered columns of dots are closer
together as shown in FIG. 9, thus preventing the printed image from
appearing to have a slantwise texture as it would in the
conventional printer. In the above multipass printing, to print the
same line by using different nozzle columns (first and second
columns of nozzles) and make the paper feed in the sub-scan
direction constant at all times, the nozzle columns each have an
odd number of nozzles.
[0078] Because each nozzle column in this embodiment has an odd
number of nozzles, both of the two nozzle columns are always used
to print one raster. For reference, the conventional sequence of
driving the nozzles, whose arrangement is identical to that of this
embodiment, is shown in FIG. 17.
[0079] In the example of FIG. 15, the printing of one raster is
performed by, for example, the nozzles k2-64 and k1-1. In other
words, the nozzles k1-1 to k1-64 print at even-numbered pixel
positions along the sub-scan direction on the recording medium and,
by using the same even-numbered pixel position pattern, print at
even-numbered pixel column positions along the main scan direction
on the recording medium. Next, the recording medium is fed by a
distance equal to 63.5 nozzles, and the nozzles k2-64 to k2-127
print at odd-numbered pixel positions along the sub-scan direction
on the recording medium and, by using the same odd-numbered pixel
position pattern, print at odd-numbered pixel column positions
along the main scan direction on the recording medium. Driving two
nozzle columns for printing in this manner produces two columns of
dots whose landing deviation directions are opposed to each
other.
[0080] In selecting the nozzle columns of the print head 8
according to the above-described ink-jet printing method a known
drive circuit may be used, and a person skilled in the art should
be able to manufacture a drive control circuit to drive the nozzles
in the above-described order. The drive circuit may have a
gate-array configuration or use a CPU. For example, the nozzles to
be used in each scan can virtually be selected by masking the data
for other than the pixels of the present scan number. Further, even
when the nozzle columns each have an even number of nozzles, the
use of the mask mentioned above allows these columns to be handled
as if they have an odd number of nozzles, by masking one end nozzle
at all times regardless of the contents of print data.
[0081] (Embodiment 4)
[0082] This embodiment allows a variety of print modes to be
selected according to the recording medium used, print quality and
printing time. FIG. 18 shows the number of print pulses, the number
of nozzles used, and a feed distance in each print mode.
[0083] In addition to the embodiments described above, the
following modifications may be made.
[0084] 1) While the embodiment 1 uses two passes in the multipass
printing and the embodiment 2 four passes, any number of passes can
be used for the same line as long as the printing is performed in
two or more passes. While the embodiment 1 and 2 use two nozzle
columns for each color of ink, any number of columns may be used as
long as they are two or more columns.
[0085] 2) Both of the first and second nozzle columns of the print
head 1 may have deviation characteristics in the same or opposite
directions with respect to the directions shown in FIG. 5 due to
variations of manufacture and assembly. Even in such a case, the
directivity of the dot landing position deviations can be dispersed
by using different nozzle columns in forming the same line.
[0086] 3) While the above examples have been described by taking an
ink-jet printer as an example, the invention can also be applied to
a variety of printing apparatuses including those which print a
plurality of dots with a plurality of print elements such as
thermal imprint type print elements.
[0087] Lastly, the configuration of the control circuit used in the
above embodiments will be explained by referring to FIG. 19. FIG.
19 shows the configuration of the control circuit for the ink-jet
printer of the above embodiments of this invention. In FIG. 19, a
CPU 100 performs control on devices and data processing via a main
bus line 105. According to a program stored in a ROM 801, the CPU
100 controls the conventionally known data processing and the head
and carriage driving associated with this invention through the
following devices. A RAM 102 is used as a work area for the data
processing by the CPU 100. Hard disks may also be used as a
storage. An image input unit 103 has an interface with a host
equipment (such as a computer as an information processing device
and an image reading device) and temporarily holds an image input
from the host equipment. An image processing unit 104 performs
color conversion processing and digitization processing. An
operation unit 106 has keys, by which an operator can enter control
inputs.
[0088] An ink ejection recovery system control circuit 107 controls
the ink ejection recovery operations, such as preliminary ink
ejection, according to the ink ejection recovery program stored in
the RAM 102. That is, an ink ejection recovery system motor 108
drives a print head 113, a cleaning blade 109 and a cap 110 both
disposed opposite the print head 113, and a suction pump 111.
[0089] A head drive control circuit 115 controls the driving of an
ink ejection electricity-heat converter of the print head 113 to
cause the print head 113 to eject ink droplets for preliminary
ejection and for printing. A heater is provided to a substrate
where the ink ejection electricity-heat converter of the print head
113 is installed, to adjust the temperature of the ink in the print
head to a desired setting. A thermistor 112 is controlled by a head
temperature control circuit 114 and also provided on the substrate
and measures the virtual ink temperature in the print head. The
thermistor 112 may also be installed outside the substrate, such as
around the print head. Further, a carriage drive control circuit
116 and a paper feed control circuit 117 similarly control carriage
movement and paper feed according to the program.
[0090] The present invention has been described in detail with
respect to preferred embodiments, and it will now be apparent from
the foregoing to those skilled in the art that changes and
modifications may be made without departing from the invention in
its broader aspect, and it is the intention, therefore, in the
apparent claims to cover all such changes and modifications as fall
within the true sprit of the invention.
* * * * *