Incremental printing of symbolic information – Thermal marking apparatus or processes – Multicolor
Reexamination Certificate
2002-11-28
2004-02-03
Tran, Huan (Department: 2861)
Incremental printing of symbolic information
Thermal marking apparatus or processes
Multicolor
Reexamination Certificate
active
06686944
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
The present invention relates to digital printer, and more specifically to a digital printer that utilizes a dye ribbon.
2. Description of the Prior Art
Digital printers are used in computer systems to print digital images. One type of printer uses a print head to heat a dye ribbon to transfer dye of different colors to a print medium. The dye ribbon comprises dyed regions colors that can be proportioned to approximate true color, and usually has a transparent overcoating region as well. Currently, this type of printer is commonly used to print digital photographs.
Consider a thermal printer
20
as shown in FIG.
1
. The thermal printer
20
includes a housing
22
, a thermal print head
24
mounted on a track
26
that is attached to the housing
22
, and a removable ribbon cassette
28
installed in the housing and having a spooled dye ribbon
30
. The printer
20
further includes motors (not shown and a control circuit (ref.
38
of
FIG. 2
) that drive the print head
24
and ribbon cassette
28
to print dye onto a print medium (not shown) such as a piece of paper.
Please refer to
FIG. 2
showing a cross-sectional view of the printer
20
cut along a section line
2
—
2
of FIG.
1
. In
FIG. 2
some components of
FIG. 1
are omitted for clarity. The printer
20
further comprises a light source (such as an LED)
32
and a photosensor
34
. The light source
32
emits light to the dye ribbon
30
. Where the light passes through the ribbon
30
the light can be detected by the photosensor
34
. A specific arrangement of the light source
32
and photosensor
34
establishes a specific sensing area
36
on the ribbon
30
. A controller
38
controls the operation of the printer
20
by controlling the print head
24
, ribbon cassette
28
, light source
32
, and photosensor
34
. As the controller
38
controls the ribbon
30
to advance so that the print head
24
can print different colors to the print medium, a color of the ribbon
30
in the sensing area
36
changes.
Please refer to
FIG. 3
showing the dye ribbon
30
removed from the ribbon cassette
28
. The ribbon
30
comprises regions of printing dye separated by strips of unprintable black dye. In
FIG. 3
printing dye is identified as Y for yellow, M for magenta, C for cyan, and O for transparent overcoating, while the unprintable black strips are identified as B. The sensing area
36
and print head
24
are separated by a predetermined distance. As the ribbon
30
moves relative to the sensing area
36
, the photosensor
34
detects the black dye regions B and triggers the printer to set operational parameters for the next color of dye on the ribbon
30
.
For example, suppose the ribbon
30
as illustrated in
FIG. 3
is moving to the right, the photosensor
34
and print head
24
are stationary, and the printer
20
has just completed printing magenta dye to the print medium. The photosensor
34
detects the black strip between the yellow and magenta dye regions and automatically configures operational parameters of the print head
24
for printing yellow. That is, the black strips trigger the printer to prepare for the next color in the predetermined color sequence of the ribbon
30
.
This triggering process is readily apparent in the signal diagram of
FIG. 4
The signal diagram of
FIG. 4
shows a plot of signal output of the photosensor
34
against a distance X along the length of the ribbon
30
. The photosensor
34
is configured such that it has a low output when detecting the unprintable black dye strips and a high output when detecting any colored printing dye region.
There are several disadvantages of the prior art printer
20
. These include the expense of disposing a plurality of unprintable black dye regions that are exclusively used for detection and the added length of ribbon
30
needed to accommodate the black dye regions.
SUMMARY OF INVENTION
It is therefore a primary objective of the claimed invention to provide a method for recognizing a color of a printing ribbon and a ribbon thereof to solve the problems of the prior art.
Briefly summarized, the claimed invention method includes providing a printing ribbon having a repeated sequence of dyed and undyed regions such that output of a photosensor sensing the ribbon is a low or high level based on a threshold. The repeated sequence is a short low level region, a first long high level region, a first long low level region, a short high level region, a second long low level region, and a second long high level region. The method includes illuminating a sensing area of the ribbon, moving the ribbon relative to the sensing area, measuring output of the photosensor over time as the ribbon moves, correlating output of the photosensor to the repeated sequence as the ribbon moves to determine the color of the ribbon under the print head, and setting operational parameters of the printer and print head according to the color of the ribbon under the print head.
According to an embodiment of the claimed invention the short low level region comprises black dye, the first long high level region comprises yellow dye and undyed ribbon, the first long low level region comprises magenta dye, the short high level region comprises undyed ribbon, the second long low level region comprises cyan dye, and the second long high level region comprises transparent overcoating and undyed ribbon.
It is an advantage of the claimed invention that the dye regions themselves are used to trigger the photosensor to allow to printer to set operational parameters for the print head and the color of dye ribbon.
It is a further advantage that no exclusive unprintable black dye regions are required to trigger the photosensor thus saving the associated manufacturing cost and time.
These and other objectives of the claimed invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
REFERENCES:
patent: 6071024 (2000-06-01), Chi-Ming et al.
patent: 6396526 (2002-05-01), Sung et al.
patent: 64-87376 (1989-03-01), None
Huang Kuan-Chih
Lin Sheng-Chih
Hi-Touch Imaging Technologies Co., Ltd.
Hsu Winston
Tran Huan
LandOfFree
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