Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2001-01-05
2002-07-09
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S037000, C400S279000, C400S283000
Reexamination Certificate
active
06416148
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system and a method for improving the print quality of a printer. Specifically, the present invention discloses a system and method for adjusting the timing interval between a print head stepping signal and a print head firing signal so that pixels are formed at desired locations.
2. Description of the Prior Art
The increasing sophistication of computer systems has lead to a corresponding increase in the graphical resolutions of these systems. Computer monitors are displaying more pixels with more color, and scanners are scanning documents at more pixels per inch than ever before. There is, therefore, an equal demand placed upon printers to offer extremely high-resolution printing. A direct consequence of this is that finer tolerances are placed upon the print head driving systems of these printers.
Please refer to FIG.
1
.
FIG. 1
is a perspective view of a prior art printer
10
. The prior art printer
10
has a carrier
9
that is slidably disposed on a print track
7
. The carrier
9
can move forward and backward, which is indicated by the arrow FB. The carrier
9
is used to hold a print cartridge
6
, which is removably fixed in the carrier
9
.
Please refer to
FIG. 2
, in conjunction with FIG.
1
.
FIG. 2
is a block diagram of the prior art printer
10
. The cartridge
6
has a print head
20
. The print head
20
does the actual printing, jetting ink onto a document. The print head
20
comprises a plurality of orifices
22
that are used to jet ink onto the document. Generally speaking, the orifices
22
are arranged in rows and/or columns and can jet ink of different colors. For the sake of simplicity, the following discussion will concentrate on only one of the orifices
22
. It should be born in mind, however, that the methods and systems discussed are all equally valid and designed for the full plurality of orifices
22
.
The prior art printer
10
further comprises a control circuit
30
and a driving system
40
. The driving system
40
comprises a stepping motor
42
that is controlled by a stepping integrated circuit (IC)
44
. The stepping IC
44
provides electrical signals
46
to control the stepping motor
42
. The driving system
40
is mechanically connected to the print head
20
to move the print head
20
along the print track
7
. This mechanical connection is indicated by arrow
40
d.
The control circuit
30
controls the general operations of the printer
10
. In particular, it sends a control signal
30
c
to the driving system
40
to trigger a stepping function of the stepping motor
42
, and sends a firing signal
30
f
to the print head
20
to make the orifice
22
jet ink. In this manner, the control circuit
30
can get the print head
20
to move to a particular location and form a pixel at a desired pixel location.
Please refer to
FIG. 3
in conjunction with
FIGS. 1 and 2
.
FIG. 3
is a simple schematic diagram of the stepping motor
42
. Please note that the structure of the stepping motor
42
has been greatly simplified. The stepping motor
42
comprises a rotor
43
, a stator
45
, and two pairs of coils wound on the stator
45
. By supplying current to alternating coils on the stator
45
, the rotor
43
can be made to rotate through succeeding 90 degree steps. With the configuration shown in
FIG. 3
, each 90 degree rotation of the rotor
43
is called a full-step. Thus, to create a full-step, current is turned off for the present pair of coils on the stator
45
and is turned on for the succeeding coils on the stator
45
. Under this shifted magnetic field, the rotor
43
will rotate to align with the corresponding energized coils on the stator
45
. As noted above, it is the stepping IC
44
that generates signals
46
to control the stator current.
It should be clear that not only full-steps are possible for the stepping motor
42
. It is also possible to perform a half-step. To perform a half-step, the stepping IC
44
generates signals to supply current equally to both pairs of adjacent stators
45
. From a vertical or a horizontal position, the rotor
43
will rotate 45 degrees, balancing between the equal magnetic fields generated by the adjacent stators
45
. Current is then turned off for the preceding pair of stators
45
, and the rotor
43
will make another 45 degree rotation, completing a full-step. In this manner, accurate half-stepping of the rotor can be achieved. Furthermore, steps finer than half steps can be achieved by varying the ratio of the stator current between adjacent pairs of stators
45
. Such steps, finer than a half step, are termed micro-steps. It is the job of the stepping IC
44
to provide these carefully calibrated stator currents to provide accurate micro-stepping of the rotor
43
. The stepping IC
44
may generate signals
46
to advance the stepping motor
42
by one micro-step when receiving proper control signals
30
c
from the control circuit
30
.
By providing micro-stepping, the overall resolution of the stepping motor
42
is greatly increased, which directly leads to a finer pitch when printing. This is illustrated in FIG.
4
and FIG.
5
.
FIG. 4
is a phase diagram of angular displacements for micro-stepping of the stepping motor
42
.
FIG. 5
illustrates locations of the print head
20
resulting from each micro-step of FIG.
4
. In
FIG. 4
, the micro-step number is indicated by an encircled numeral. For the stepping motor as shown in
FIG. 3
, each full step has been broken into 16 micro-steps, with the intermediate steps running from 1 to 15. Ideally, the angular rotation of the rotor
43
from one micro-step to the next should be 90°/16, which equals 5.6250°. Depending on the gearing of the driving system
40
d,
each of these micro-steps should be translated into an equal displacement of the print head
20
along the print track
7
, such as {fraction (1/1200)} of an inch for a 1200 dpi printer. These displacements are indicated in
FIG. 5
, with the resulting location of each micro-step on the print track
7
indicated by its encircled numeral.
In the prior art, the control circuit
30
comprises a timer
32
. The timer
32
is used to generate regularly spaced control signals
30
c
that are sent to the driving system
40
. The interval between control signals
30
c
is of a sufficient length of time to enable the rotor
43
to move to and settle into the next micro-step position. The control circuit
30
then sends out the firing signal
30
f,
and the firing signal
30
f
will logically “AND” with the image data to activate the orifice on the print head to jet the ink. In other words, the print head will jet the ink if both the firing signal
30
f
and the image data are “1”, and will not jet the ink if either one of the firing signal
30
f
or the image data is “0”. Thus, the same interval &Dgr;t exists between successive firing signals
30
f
and successive control signals
30
c,
the two signals having only a constant time delay between them. The timing of the control and firing signals is indicated in FIG.
6
. The result of these two signals
30
c
and
30
f,
in conjunction with the even micro-steps of the stepping motor
42
, should result in pixels placed at evenly spaced intervals. That is, with each successive micro-step, a pixel should be formed on a desired pixel position
23
that corresponds to that micro-step, as indicated in FIG.
5
.
The above is the ideal. The reality is that the stepping IC
44
is unable to evenly divide the angular distribution of the micro-steps between full-steps. This problem is illustrated in FIG.
7
.
FIG. 7
is a phase diagram of the actual angular displacements for the micro-stepping of the stepping motor
42
. The stepping IC
44
uses some approximation technique (e.g. linear approximation) to map the arc of the full-step. This results in some of the micro-steps making too large of a rotation, and others making rotations that are too small. This irregularity in the angular distributions of the micro-steps results in a corresp
Du Ben-Chuan
Li Yung-Yi
Acer Communications and Multimedia Inc.
Barlow John
Hsu Winston
Mouttet Blaise
LandOfFree
Method and system for improving the print quality of a printer does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and system for improving the print quality of a printer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and system for improving the print quality of a printer will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2906581