Information
-
Patent Grant
-
6712536
-
Patent Number
6,712,536
-
Date Filed
Tuesday, October 9, 200122 years ago
-
Date Issued
Tuesday, March 30, 200420 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Yan; Ren
- Nguyen; Hoai-An D.
Agents
-
CPC
-
US Classifications
Field of Search
US
- 400 582
- 400 578
- 400 279
- 347 13
- 347 116
- 347 81
- 347 177
- 358 112
- 358 514
- 235 435
- 235 439
- 271 315
- 271 261
- 271 26503
-
International Classifications
-
Abstract
A printer prints images on a printing medium having a mark. The printer includes an optical sensor, a feeding section, a controller, and a printing section. The optical sensor is operable to generate a signal based on a position of the mark of the printing medium with respect to the optical sensor. The feeding section is operable to perform feeding of the printing medium. The controller is operable to control the feeding of the printing medium based on the signal. The printing section is operable to print images on the printing medium.
Description
BACKGROUND OF THE INVENTION
The present invention relates to printers, and more specifically, to apparatus and methods for printing on a card with high precision.
Thermal printers are used for printing various documents including personal identification cards. Typically, these identification cards have images on their surfaces printed in various colors. Some cards have images printed in metallic color. Further, some cards have a lenticular lens thereon so that a user can see different images depending on the viewing angle with respect to the normal direction of the surface of the card.
In the prior art, when an image sheet having printed images thereon is affixed onto a plastic sheet having a lenticular lens thereon, alignment of these two sheets requires high precision. Misalignment of the image sheet and the lenticular lens sheet would result in mixed or blurred images of the two separate images. In a normal lenticular card, only one of the two images can be seen if the user fixes the point of view. In order to align the image sheet with the lenticular sheet, the prior art technique requires a skilled worker to manually align the two sheets. This is a time-consuming task, and thus incurs cost. Besides, due to the manual alignment, the yield of the resulting product is low.
In view of these and other issues, it would be desirable to have a technique allowing a printer to print images with high precision.
SUMMARY OF THE INVENTION
According to various embodiments of the present invention, a printer prints images on a printing medium having a mark. The printer includes an optical sensor, a feeding section, a controller, and a printing section. The optical sensor is operable to generate a signal based on a position of the mark of the printing medium with respect to the optical sensor. The feeding section is operable to perform feeding of the printing medium. The controller is operable to control the feeding of the printing medium based on the signal. The printing section is operable to print images on the printing medium.
In a specific embodiment, the sensor is a linear optical sensor which is operable to detect the mark provided on the printing medium. Based on a signal output from the sensor, the controller aligns the printing medium with the images printed on the medium using the feeding section.
In some embodiments, the mark is a line or a stripe drawn on the printing medium diagonally with respect to the line.
In some specific embodiments, the printing section includes an intermediate transfer film, a print head, and an intermediate transfer roller. The print head has a plurality of resistance heating elements for transfer of the ink from the ink film to the intermediate transfer film. The intermediate transfer roller is operable to heat the ink on the intermediate transfer film for transfer of the ink from the intermediate transfer film to the printing medium.
A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings.
BRIEF DESCRIPTION OF THE DRAWING
The invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which:
FIG. 1
is a cross-sectional view of a thermal transfer printer of a specific embodiment according to the present invention.
FIG. 2
is a cross-sectional view of a thermal transfer printer of an alternative embodiment according to the present invention.
FIG. 3
is a cross-sectional view of a card after the printing process utilizing a specific embodiment of the apparatus and methods according to the present invention.
FIG. 4
is a plain view of the printing medium and the sensor used for specific embodiments of the apparatus and methods according to the present invention.
FIG. 5
is a plain view of the printing medium and the sensor used for specific embodiments of the apparatus and methods according to the present invention where the sensor transverses a mark.
FIG. 6
is a plain view of the printing medium and the sensor used for alternative embodiments of the apparatus and methods according to the present invention where the sensor transverses a mark.
FIG. 7
is a plain view of the printing medium and the sensor in an alternative configuration used for specific embodiments of the apparatus and methods according to the present invention where the sensor transverses a mark.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
Various embodiments of the present invention will now be described in detail with reference to the drawings, wherein like elements are referred to with like reference labels throughout.
As described in detail below, various embodiments of the present invention include an optical sensor which is operable to generate a signal based on a position of mark provided on a printing medium. Thus, the embodiments of the present invention are capable of aligning the printing medium with high precision, thereby avoiding misalignment of images printed on the medium with respect to the medium.
In this specification, “regular color ink” means any ink other than the metallic ink, which includes, for example, cyan ink, magenta ink, yellow ink, black ink, and white ink. A “regular color ink film” includes any film which carries regular color ink thereon. In this specification, “ink” includes regular color ink and metallic ink which presents metallic color. An “ink film” includes any ink film which carries metallic ink or regular color ink. Thus, the ink film includes regular color ink films
140
and
240
, and an intermediate transfer film
148
described in detail below referring to
FIGS. 1 and 2
.
FIG. 1
is a cross-sectional view of a thermal transfer printer
100
of a specific embodiment according to the present invention. The thermal transfer printer
100
includes a thermal transfer printing section
104
, and a controller
106
within a housing
108
. A printing medium
110
is fed along a medium flow path
112
from left to right in FIG.
1
.
FIG. 1
shows two locations of the printing medium
110
in the thermal transfer printer
100
.
Suitable polymers for the printing medium
110
include polyvinylchloride (PVC), polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS), polypropylene sulfate (PPS), and polyethylene terephthalate glycol (PETG). Circles shown in
FIG. 1
represent rollers or platens, and elongated rectangles
110
in
FIG. 1
represent cards or plate-like materials used as the printing medium
110
.
The thermal transfer printing section
104
is operable to heat regular color ink on the regular color ink film
140
for transfer the regular color ink from the regular color ink film
140
to the printing medium
110
. The regular color ink film
140
includes at least one of a cyan color layer, a magenta color layer, a yellow color layer, a black color layer, and a white color layer on a base film. The base film is made from plastic materials including polyethylene terephthalate (PET).
The thermal transfer printing section
104
includes a printing head
142
having a plurality of resistance heating elements
144
, and a platen
146
. The resistance heating elements
144
apply heat to the regular color ink film
140
based on electric drive pulses representing image data. The printing head
142
presses the regular color ink film
140
and the intermediate transfer film
148
against the platen
146
, thereby transferring the regular color ink to the intermediate transfer film
148
by heat and pressure. The intermediate transfer film
148
constitutes a closed loop, which rotates counterclockwise in
FIG. 1
supported by feeding rollers
150
,
152
,
154
and
156
.
The regular color ink transferred from the regular color ink film
140
to the intermediate transfer film
148
is carried counter clockwise to a point where an intermediate transfer roller
158
and a platen
160
contact the printing medium
110
. In order to determine the exact position of the printing medium
110
, the thermal transfer printing section
104
includes a sensor
162
which detects a predetermined point, e.g., a mark
161
, provided on the printing medium
110
by utilizing, for example, an optical sensing technique. A light emitting device
163
emits light toward the sensor
162
through the printing medium
110
during detection of the location of the printing medium
110
. The light emitting device
163
may be any device which supplies sufficient intensity and wavelength of light for the sensor
162
such as an light emitting diode, a lamp, an electroluminescent lamp, or the like.
In the specific embodiment shown in
FIG. 1
, the light emitting device
163
is positioned on the opposite side of the sensor
162
with respect to the medium flow path
112
because the sensor
162
generates signal based on the light intensity through the printing medium
110
, and the mark
161
on the printing medium
110
varies the transmissivity of the printing medium
110
compared to other part of the printing medium
110
. Conversely, when the reflection of the printing medium
110
is varied by the mark
161
, the light emitting device
163
is positioned on the same side of the sensor
162
with respect to the medium flow path
112
.
Feeding rollers
164
and
166
feed the printing medium
110
onto the intermediate transfer roller
158
and the platen
160
along the medium flow path
112
. The controller
106
controls rotational speeds and directions of the feeding roller
164
appropriately.
The printing medium
110
is positioned on a predetermined point on the medium flow path
112
by using the sensor
162
and the feeding roller
164
controlled by the controller
106
. Then, the feeding rollers
164
and
166
feed the printing medium
110
onto the intermediate transfer roller
158
and the platen
160
along the medium flow path
112
. The intermediate transfer roller
158
presses the intermediate transfer film
148
and the printing medium
110
against the platen
160
, thereby transferring the regular color ink from the intermediate transfer film
148
to the printing medium
110
by pressure. Feeding rollers
170
and
172
feed the printing medium
110
out of the housing
108
of the thermal transfer printer
100
along the medium flow path
112
. The controller
106
controls rotational speeds and directions of the feeding rollers
170
and
172
appropriately.
FIG. 2
is a cross-sectional view of a thermal transfer printer
200
of an alternative embodiment according to the present invention. The thermal transfer printer
200
includes a thermal transfer printing section
204
, and the controller
106
within the housing
108
. The differences between the embodiments shown in
FIGS. 1 and 2
mainly reside in the thermal transfer printing section
204
. Thus, it should be appreciated that elements in
FIG. 2
which are assigned the same reference labels as shown in
FIG. 1
have the same functionalities as those of
FIG. 1
with the exception that the elements are designed to be coordinated with the thermal transfer printing section
204
.
The thermal transfer printing section
204
is operable to heat regular color ink on the regular color ink film
240
for transfer the regular color ink from the regular color ink film
240
to the printing medium
110
. The regular color ink film
240
includes at least one of a cyan color layer, a magenta color layer, a yellow color layer, a black color layer, and a white color layer on a base film, which is made from plastic materials including PET.
The thermal transfer printing section
204
includes a printing head
242
having a plurality of resistance heating elements
244
, and a platen
246
. The resistance heating elements
244
apply heat to the regular color ink film
240
based on electric drive pulses representing image data. The printing head
242
presses the regular color ink film
240
and the printing medium
110
against the platen
246
, thereby transferring the regular color ink from the regular color ink film
240
to the printing medium
110
by heat and pressure.
FIG. 3
is a cross-sectional view of a card
300
after the printing process utilizing a specific embodiment of the apparatus and methods according to the present invention. Before the printing process utilizing the thermal transfer printers
100
and
200
, the card
300
includes only the printing medium
110
. The printing medium
110
in the card
300
used for a specific embodiment of the present invention includes parallel ridge portions
302
on one side thereof, which may be used as lenticular lenses. In a specific embodiment, the pitch p between the immediately neighboring parallel ridge portions
302
is, for example, 0.254 mm (i.e., 100 line per inch).
After the printing process performed by one of the thermal transfer printing sections
104
and
204
, images
310
-
315
and
320
-
325
are printed on the printing medium
110
. In this specific embodiment, the images
310
-
315
and
320
-
325
compose first and second pictures, respectively, where the first and second pictures can be seen from different angles with respect to the normal direction of the card
300
. As described in detail below, this specific embodiment of the present invention having the sensor
162
capable of detecting the location of the card
300
with high precision is advantageous especially when the printing medium
110
has the lenticular lenses thereon because aligning the images
310
-
315
and
320
-
325
with the ridge portion
302
becomes an issue.
However, it should be appreciated that other images including a plain, single image rather than stripes of images similar to the images
310
-
315
and
320
-
325
may be printed on the top surface of the printing medium
110
. Furthermore, the printing medium
110
may be any other suitable planar printing medium without including parallel ridge portions
302
.
FIG. 4
is a plain view of the printing medium
110
and the sensor
162
used for specific embodiments of the apparatus and methods according to the present invention. As described above referring to
FIGS. 1 and 2
, the printing medium
110
has the mark
161
thereon. The mark
161
has a different transmissivity rate or a reflection rate compared to other part of the printing medium
110
. In a specific embodiment, the mark
161
is provided on the printing medium
110
by printing a black stripe having the width w. However, it should be appreciated that the color and the width w of the mark
161
may be any other suitable color and width. Also, the mark
161
may be provided by any other suitable way such as etching, abrasion, scratching or the like. In the embodiment shown in
FIG. 4
, the width w ranges from about 0.5 mm to about 1.0 mm. However, in this specification, the term “stripe” covers (i) the mark
161
of which width w is not negligible compared to the size of each of the sensor cells
410
,
411
,
412
, . . . , and (ii) a fine line of which width is substantially negligible compared to the size of each of the sensor cells
410
,
411
,
412
, . . . as described in detail below referring to FIG.
6
.
In the specific embodiments shown in
FIGS. 1
,
2
and
4
of the printer according to the present invention, the sensor
162
is a charge coupled device (CCD) line sensor which has a plurality of sensor cells
410
,
411
,
412
, . . . It should be appreciated that any other suitable linear optical sensor may be used for the sensor
162
. In some embodiments, the mark
161
and the longitudinal direction of the sensor
162
intersect at an angle which is substantially non-perpendicular, where a line
460
in
FIG. 4
is parallel to the mark
161
. In more specific embodiments, the angle
450
at which the mark
161
and the longitudinal direction of the sensor
162
intersect is between about 3 degrees and about 30 degrees. The printing medium
110
is fed along a feeding direction
470
by the feeding rollers
164
and
166
. The medium flow path
112
can be a curved line. In such a case, the feeding direction
470
is a direction along which the printing medium
110
is fed in the vicinity of the sensor
162
.
FIG. 5
is a plain view of the printing medium
110
and the sensor
162
used for specific embodiments of the apparatus and methods according to the present invention where the sensor
162
transverses the mark
161
. During the process of feeding the printing medium
110
toward the thermal transfer printing sections
104
and
204
along the feeding direction
470
, the sensor
162
transverses the mark
161
. In a specific embodiment shown in
FIG. 5
, the sensor cells
410
-
413
and
419
-
422
output a HIGH level signal corresponding to a high intensity of the incident light, and the sensor cells
414
-
418
output a LOW level signal corresponding to a low intensity of the incident light. It should be appreciated that the level of the output signal from the sensor
162
may be inverted or shifted depending on the characteristics of the sensor
162
and output circuitry associated with the sensor
162
. The controller
106
receives the output signal from the sensor
162
and calculates the distance between the mark
161
on the printing medium
110
and the sensor
162
, i.e., the location of the printing medium
110
with respect to the sensor
162
, based on the output signal from each of the sensor cells
410
-
422
.
FIG. 6
is a plain view of the printing medium
110
and the sensor
162
used for specific embodiments of the apparatus and methods according to the present invention where the sensor
162
transverses a mark
661
. In this specific embodiment, the mark
661
is a fine line of which width is negligible compared to the size of the each of the sensor cells
410
-
422
.
Similar to the operation described referring to
FIG. 5
, during the process of feeding the printing medium
110
toward the thermal transfer printing sections
104
and
204
along the feeding direction
470
, the sensor
162
transverses the mark
661
. In a specific embodiment shown in
FIG. 6
, the sensor cells
410
-
412
and
415
-
422
output a HIGH level signal corresponding to a high intensity of the incident light, and the sensor cells
413
and
414
output a LOW level signal corresponding to a low intensity of the incident light. It should be appreciated that the level of the output signal from the sensor
162
may be inverted or shifted depending on the characteristics of the sensor
162
and output circuitry associated with the sensor
162
. The controller
106
receives the output signal from the sensor
162
and calculates the distance between the mark
661
on the printing medium
110
and the sensor
162
, i.e., the location of the printing medium
110
with respect to the sensor
162
, based on the output signal from each of the sensor cells
410
-
422
.
FIG. 7
is a plain view of the printing medium
110
and the sensor
162
used for specific embodiments of the apparatus and methods according to the present invention where the sensor
162
transverses a mark
661
. In this specific embodiment, the mark
661
and the longitudinal direction of the sensor
162
intersect at an angle which is substantially perpendicular. In other words, the angle
450
in
FIG. 7
is substantially 90 degrees.
Similar to the operation described referring to
FIG. 5
, during the process of feeding the printing medium
110
toward the thermal transfer printing sections
104
and
204
along the feeding direction
470
, the sensor
162
transverses the mark
661
. In a specific embodiment shown in
FIG. 7
, the sensor cells
410
-
414
and
416
-
422
output a HIGH level signal corresponding to a high intensity of the incident light, and the sensor cell
415
outputs a LOW level signal corresponding to a low intensity of the incident light. It should be appreciated that the level of the output signal from the sensor
162
may be inverted or shifted depending on the characteristics of the sensor
162
and output circuitry associated with the sensor
162
. The controller
106
receives the output signal from the sensor
162
and calculates the distance between the mark
661
on the printing medium
110
and the sensor
162
, i.e., the location of the printing medium
110
with respect to the sensor
162
, based on the output signal from each of the sensor cells
410
-
422
.
The embodiments described above referring to
FIGS. 4-6
where the sensor
162
is provided so that the angle
450
is substantially non-perpendicular are advantageous especially when higher detection resolution of the sensor
162
is necessary. Suppose that the sensor
162
has a longitudinal length of 25 mm, having 500 sensor cells, and the angle
450
is 11.5 degrees. Then, the detection resolution of the sensor
162
is improved up to 0.01 mm (=25×sin 11.5/500). Here, the detection resolution is defined as a resolution along the feeding direction
470
while actual resolution of the sensor
162
is defined as a resolution along the longitudinal direction of the sensor
162
.
It should be appreciated that the angle
450
which is substantially 90 degrees may be applied to the embodiment illustrated in
FIGS. 4 and 5
. In the specific embodiments described above, the sensor
162
is a CCD line sensor. However, the sensor
162
may be a two-dimensional CCD sensor as long as the sensor
162
traverses the mark on the printing medium
110
during the feeding of the printing medium
110
. Alternatively, the sensor
162
may be any suitable sensor which is capable of detecting the location of the printing medium
110
.
The specific embodiments of the present invention described referring to
FIGS. 1 and 2
utilize the roller printing section
102
. However, it should be appreciated that the sensor
162
may be used with only one of the thermal transfer printing sections
104
and
204
, i.e., without employing the roller printing section
102
. The thermal transfer printing sections
104
and
204
may be replaced by any other suitable printing mechanism such as an ink jet print engine, a bubble jet print engine, an electrophotographic print engine, a dot impact print engine or the like.
The specific embodiment of the apparatus and methods according to the present invention described above referring to
FIG. 1
can be implemented by utilizing the thermal transfer printer
200
illustrated in
FIG. 2
in a similar manner except that the regular color printing is performed by the thermal transfer printing section
204
rather than the thermal transfer printing section
104
. Thus, further detail is omitted.
In the specific embodiments described above, the regular color printing by the thermal transfer printing sections
104
and
204
can be implemented by a single thermal head. However, it should be appreciated that a plurality of thermal heads can be used for the regular color printing.
In the specific embodiments described above, the image layer printing by the thermal transfer printing sections
104
and
204
can be implemented by a single thermal head. However, it should be appreciated that a plurality of thermal heads can be used for the regular color printing. For example, five separate thermal heads can be used for five colors (e.g., cyan, magenta, yellow, and black and white) for the thermal transfer printing sections
104
and
204
.
In the above-described specific embodiments of the thermal transfer printer according to the present invention described referring to
FIGS. 1 and 2
, the feeding rollers
164
,
166
,
170
and
172
are appropriately positioned along the medium flow path
112
so that the position of the printing medium
110
is controlled to go back and forth along the medium flow path
112
based on a specific printing process which is applied to the printing medium
110
.
In the above embodiments of the thermal transfer printer according to the present invention described referring to
FIGS. 1 and 2
, the controller
106
can be implemented by any combination of software and/or hardware. For example, the controller
106
can be implemented by a microprocessor, a memory device which stores instruction codes and data, and an interface which drives external devices such as the feeding rollers, the transfer roller, and the intermediate transfer roller.
Although only a few embodiments of the present invention have been described in detail, it should be understood that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. For example, although the illustrated embodiments have been described primarily in the context of a thermal transfer printer for printing images on a plastic card, it should be appreciated that various materials may be used for embodiments of the thermal transfer printer according to the present invention. Therefore, it should be apparent that the above described embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope of the appended claims.
Claims
- 1. A printer for printing on a printing medium having a mark, comprising:an optical sensor operable to generate a signal based on a position of the mark of the printing medium with respect to the optical sensor; a feeding section operable to perform feeding of the printing medium; a controller operable to control the feeding of the printing medium based on the signal; and a printing section operable to print images on the printing medium, wherein the optical sensor is operable to generate the signal by sensing a change of transmissivity of the printing medium; the optical sensor is a CCD line sensor having a longitudinal direction along which a plurality of sensor cells constituting the CCD line sensor are provided; the mark is a stripe drawn on the printing medium; the stripe is substantially a line; the line is drawn substantially perpendicular to a feeding direction along which the feeding section feeds the printing medium; the line and the longitudinal direction of the CCD line sensor intersect at an angle which is substantially non-perpendicular; and the line traverses all of the sensor cells while the printing medium is being fed.
- 2. The printer of claim 1, wherein the line and the longitudinal direction of the CCD line sensor intersect at an angle which is between about 3 degrees and about 30 degrees.
- 3. The printer of claim 1, wherein the printing section includes:a thermal transfer printing section operable to heat ink on an ink film for transfer of the ink from the ink film to the printing medium; and a platen against which the thermal transfer printing section presses the ink film and the printing medium.
- 4. The printer of claim 3, wherein the thermal transfer printing section includes:an intermediate transfer film, a print head having a plurality of resistance heating elements for transfer of the ink from the ink film to the intermediate transfer film, and an intermediate transfer roller operable to heat the ink on the intermediate transfer film for transfer of the ink from the intermediate transfer film to the printing medium.
- 5. The printer of claim 3, wherein the thermal transfer printing section includes:a print head having a plurality of resistance heating elements for transfer of the ink from the ink film to the intermediate transfer film.
- 6. A printer for printing on a printing medium having a mark, comprising:means for generating a signal based on a position of the mark of the printing medium with respect to an optical sensor; means for feeding the printing medium; means for controlling the feeding of the printing medium based on the signal; and means for printing images on the printing medium; wherein the optical sensor is operable to generate the signal by sensing a change of transmissivity of the printing medium; the optical sensor is a CCD line sensor having a longitudinal direction along which a plurality of sensor cells constituting the CCD line sensor are provided; the mark is a stripe drawn on the printing medium; the stripe is substantially a line; the line is drawn substantially perpendicular to a feeding direction along which the feeding section feeds the printing medium; the line and the longitudinal direction of the CCD line sensor intersect at an angle which is substantially non-perpendicular; and the line traverses all of the sensor cells while the printing medium is being fed.
- 7. A method of printing on a printing medium having a mark, comprising:generating by an optical sensor a signal based on a position of the mark of the printing medium with respect to the optical sensor; feeding the printing medium; controlling the feeding of the printing medium based on the signal; and printing images on the printing medium; wherein the optical sensor is operable to generate the signal by sensing a change of transmissivity of the printing medium; the optical sensor is a CCD line sensor having a longitudinal direction along which a plurality of sensor cells constituting the CCD line sensor are provided; the mark is a stripe drawn on the printing medium; the stripe is substantially a line; the line is drawn substantially perpendicular to a feeding direction along which the feeding section feeds the printing medium; the line and the longitudinal direction of the CCD line sensor intersect at an angle which is substantially non-perpendicular; and the line traverses all of the sensor cells while the printing medium is being fed.
- 8. The method of claim 7, wherein the line and the longitudinal direction of the CCD line sensor intersect at an angle which is between about 3 degrees and about 30 degrees.
- 9. The method of claim 7, wherein the printing includes:heating ink on an ink film for transfer of the ink from the ink film to the printing medium; and pressing the ink film and the printing medium against a platen.
- 10. The method of claim 7, wherein the printing includes:heating ink on an ink film for transfer of the ink from the ink film to an intermediate transfer film, pressing the ink film and the intermediate transfer film against a first platen, pressing the ink on the intermediate transfer film for transfer of the ink from the intermediate transfer film to the printing medium.
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