U.S. patent number RE33,260 [Application Number 07/189,554] was granted by the patent office on 1990-07-10 for thermal printer color dye frame identification using red and yellow light sources.
This patent grant is currently assigned to Eastman Kodak Company. Invention is credited to Stanley W. Stephenson.
United States Patent |
RE33,260 |
Stephenson |
July 10, 1990 |
Thermal printer color dye frame identification using red and yellow
light sources
Abstract
In a thermal printer for printing color images which uses a
carrier having a repeating series of spaced frames of yellow,
magenta and cyan colored heat transferable dyes, apparatus for
identifying the different color frames of each series uses a source
of red light and a source of yellow light. The apparatus responds
to the intensity of red and yellow source light which passes
through a dye frame to identify that dye frame.
Inventors: |
Stephenson; Stanley W.
(Spencerport, NY) |
Assignee: |
Eastman Kodak Company
(Rochester, NY)
|
Family
ID: |
26885279 |
Appl.
No.: |
07/189,554 |
Filed: |
May 2, 1988 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
892620 |
Aug 4, 1986 |
04710781 |
Dec 1, 1987 |
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Current U.S.
Class: |
347/178; 346/136;
400/120.04; 400/240.3; 400/240.4; 400/248.3; 400/249; 400/703 |
Current CPC
Class: |
B41J
35/18 (20130101) |
Current International
Class: |
B41J
35/18 (20060101); B41J 35/16 (20060101); G01D
015/10 (); B41J 003/20 () |
Field of
Search: |
;346/76PH,136
;400/120,240.3,248.3,240.4 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Shaw; Clifford C.
Assistant Examiner: Preston; Gerald E.
Attorney, Agent or Firm: Owens; Raymond L.
Claims
I claim:
1. In a thermal printer system including a printer which uses a
carrier with a repeating series of spaced yellow, magenta and cyan
dye frames, and a receiver which receives dye from the yellow,
magenta and cyan dye frames of a series to form a colored image,
such printer including a print head having a plurality of
selectively energizable heating elements, means for moving the
carrier and the receiver along respective paths so as to
sequentially move each dye frame of a series and the receiver
relative to the print head such that as the heating elements are
selectively energized, dye from each dye frame of a series is
transferred to the receiver and forms a colored image in the
receiver, means for identifying dye frames of such series
comprising:
(a) a red LED disposed adjacent to the carrier path for
illuminating the carrier with red light;
(b) a yellow LED disposed adjacent to the carrier path for
illuminating the same dye frame of the carrier illuminated by red
light with yellow light;
(c) first and second spaced photodetectors disposed adjacent to the
carrier path and respectively responsive to the intensity of yellow
and red light which passes through the dye frames for respectively
providing electrical signals, the levels of such signals being a
function of the intensity of source light which passes through a
dye frame;
(d) said first photodetector producing a signal level above a
threshold level when illuminated by yellow light passing through a
yellow dye frame and below such threshold level when illuminated by
yellow light passing through a cyan or magenta dye frame, said
second photodetector producing a signal level above the threshold
level when illuminated by red light passing through a yellow or a
magenta dye frame and below such threshold level when illuminated
by red light passing through cyan dye frames; and
(e) means responsive to the threshold levels such first and second
photodetector for identifying the particular dye frame being
illuminated by the red and yellow light sources.
2. The invention as set forth in claim 1, wherein said electrical
signals responsive means includes a threshold detector connected to
each photodetector for providing logic signals representing whether
or not an electrical signal is above the threshold level, and
computing means responsive to said logic signals for identifying
the illuminated dye frame of a series.
3. The invention as set forth in claim 2, wherein red and yellow
light from the red and yellow LED's illuminate the same spot on the
carrier adjacent to an edge of the carrier. .Iadd.
4. In a thermal printer system including a printer which uses a
carrier with a repeating series of spaced different colored dye
frames, and a receiver which receives dye from the color frames of
the series to form a colored image, means for moving the carrier
and the receiver along respective paths so as to sequentially move
each dye frame of a series and the receiver so that dye from each
dye frame of a series is transferred to the receiver and forms a
colored image in the receiver, means for identifying dye frames of
such series comprising:
(a) a low frequency LED disposed adjacent to the carrier path for
illuminating the carrier with low frequency light;
(b) a high frequency LED disposed adjacent to the carrier path for
illuminating the same dye frame of the carrier illuminated by low
frequency light with high frequency light;
(c) first and second spaced photodetectors disposed adjacent to the
carrier path and respectively responsive to the intensity of light
which passes through the dye frames for respectively providing
electrical signals, the levels of such signals being a function of
the intensity of source light which passes through a dye frame and
representing logic patterns; and
(d) means responsive to the logic patterns of the electrical
signals produced by such first and second photodetectors for
identifying a particular dye frame being illuminated by the light
sources. .Iaddend. .Iadd.5. In a thermal printer system including a
printer which uses a carrier with a repeating series of spaced
yellow, magenta and cyan dye frames, and a receiver which receives
dye from the yellow, magenta and cyan dye frames of a series to
form a colored image, such printer including a print head having a
plurality of selectively energizable heating elements, means for
moving the carrier and the receiver along respective paths so as to
sequentially move each dye frame of a series and the receiver such
that dye from each dye frame of a series is transferred to the
receiver and forms a colored image in the receiver, means for
identifying dye frames of such series comprising:
(a) a low frequency LED disposed adjacent to the carrier path for
illuminating the carrier with low frequency light;
(b) a high frequency LED disposed adjacent to the carrier path for
illuminating the same dye frame of the carrier illuminated by low
frequency light with high frequency light;
(c) first and second spaced photodetectors disposed adjacent to the
carrier path and respectively responsive to the intensity of light
which passes through the dye frames for respectively providing
electrical signals, the levels of such signals being a function of
the intensity of source light which passes through a dye frame;
(d) said first photodetector producing a signal level above a
threshold level when illuminated by high frequency light passing
through a yellow dye frame and below such threshold level when
illuminated by high frequency light passing through a cyan or a
magenta dye frame, said second photodetector producing a signal
level above the threshold level when illuminated by low frequency
light passing through a yellow or a magenta dye frame and below
such threshold level when illuminated by low frequency light
passing through cyan dye frames; and
(e) means responsive to the threshold signal levels such first and
second photodetectors for identifying a particular dye frame being
illuminated by
the light source. .Iaddend. .Iadd.6. The invention as set forth in
claim 5, wherein said electrical signals responsive means includes
a threshold detector connected to each photodetector for providing
logic signals representing whether or not an electrical signal is
above the threshold level, and computing means responsive to said
logic signals for identifying the illuminated dye frame of a
series. .Iaddend.
Description
This application is a reissue application for U.S. Pat. No.
4,710,781 issued on Dec. 1, 1987, on U.S. Ser. No. 892,620 filed
Aug. 4, 1986. .Iaddend.
CROSS-REFERENCE TO RELATED APPLICATION
Reference is made to commonly assigned U.S. patent application Ser.
No. 851,748 filed Apr. 14, 1984 entitled "Identifying Color Dye
Frames in Carrier Used in Thermal Printer" by S. J. Sparer and S.
W. Stephenson.
FIELD OF THE INVENTION
The present invention relates to thermal printers for printing
color images which uses a carrier having a repeating series of
spaced frames of different colored heat transferable dyes. More
particularly, this invention relates to identifying the different
color frames of each series.
BACKGROUND OF THE INVENTION
In one type of thermal printer which prints colored images, a
carrier contains a repeating series of spaced frames of different
colored heat transferable dyes. In such apparatus, the carrier is
disposed between a receiver, such as coated paper, and a print head
formed of, for example, a plurality of individual heating elements.
When a particular heating element is energized, it is heated and
causes dye from the carrier to transfer to the receiver. The
density or darkness of the printed color dye is a function of the
energy delivered from the heating element to the carrier.
Thermal dye transfer printers offer the advantage of true
"continuous tone" dye density transfer. This result is obtained by
varying the energy applied to each heating element, yielding a
variable dye density image pixel on the receiver.
The carrier often includes a repeating series of spaced yellow,
magenta and cyan dye frames. First, the yellow frame and the
receiver are moved to be positioned under the print head and as
they are advanced, the heating elements are selectively energized
to form a row of yellow image pixels in the receiver. This process
is repeated until a yellow dye image is formed in the receiver.
Next, the magenta frame is moved under the print head and the
receiver is also moved under the print head. Both the receiver and
the magenta frame are moved as the heating elements are selectively
energized and a magenta image is formed superimposed upon the
yellow image. Finally, as the cyan dye frame and the receiver are
moved under the print head, the heating elements are selectively
energized and a cyan dye image is formed in the receiver
superimposed upon the yellow and magenta dye images. These yellow,
magenta and cyan dye images combine to form a colored image.
Since the carrier has a repeating series of yellow, magenta and
cyan dye frames, it is important to identify the leading yellow
frame of each series. One way to identify the leading yellow frame
is to employ a conventional sensitometer. This sensitometer
identifies a yellow dye frame by producing a particular analog
signal in response to light which passes a yellow dye frame. Such
sensitometer is effective but can be a complex and expensive piece
of equipment. Another way to identify a yellow dye frame is to
provide code marks. A code field composed of a series of black code
bars can be disposed in the clear interframe area between dye
frames. This code field can identify the particular color of the
following frame. A reader station can be provided which includes a
plurality of photodetectors which are aligned to produce a
particular output signal representing the color of the following
colored frame. Such a system can perform quite satisfactorily but
requires decoding electronics and involves additional manufacturing
steps for forming the code field in the clear interframe areas of
the carrier.
SUMMARY OF THE INVENTION
Accordingly, it is an object of this invention to provide an
improved system for identifying the dye frames of a repeating
series of dye frames on a carrier as it is used in a thermal
printer.
This object is achieved in a thermal printer system including a
printer which uses a carrier with a repeating series of spaced
yellow, magenta and cyan dye frames and a receiver which receives
dye from the yellow, magenta and cyan dye frames of a series to
form a colored image, such printer including a print head having a
plurality of selectively energizable heating elements, means for
moving the carrier and the receiver along respective paths so as to
sequentially move each dye frame of a series and the receiver
relative to the print head such that as the heating elements are
selectively energized, dye from each dye frame of a series is
transferred to the receiver and forms a colored image in the
receiver, means for identifying the dye frames of such series
comprising:
(a) a source of red light disposed adjacent to the carrier path for
illuminating the carrier with red light;
(b) a source of yellow light disposed adjacent to the carrier path
for illuminating the same dye frame of the carrier illuminated by
red light;
(c) first and second spaced photodetectors disposed adjacent to the
carrier path and respectively responsive to the intensity of yellow
and red source light which passes through the dye frames for
respectively providing electrical signals, the levels of such
signals being a function of the intensity of source light which
passes through a dye frame;
(d) said first photodetector producing a signal level above a
threshold level when illuminated by yellow source light passing
through a yellow dye frame and below such threshold level when
illuminated by yellow source light passing through a cyan or a
magenta dye frame, said second photodetector producing a signal
level above the threshold level when illuminated by red source
light passing through a yellow or a magenta dye frame and below
such threshold level when illuminated by red source light passing
through a cyan dye frame; and
(e) means responsive to the threshold levels of such first and
second photodetector electrical signals for identifying the
particular dye frame being illuminated by the red and yellow light
sources.
In one space-saving embodiment, the red and yellow LEDs illuminate
the same portion of each dye frame adjacent to the edge of the
carrier.
Commercially available low cost, long life, LED light sources and
low cost, long life, photodetectors can be employed in this
invention. In accordance with the invention the identification of
dye frames can be accomplished quite simply.
Another advantage of this invention is that no clear interframe
area between carrier dye frames need be employed.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic of a thermal printer apparatus which can be
employed to make colored image in a receiver in accordance with the
invention;
FIG. 2 is a perspective of several heating elements used in the
print head of the apparatus of FIG. 1;
FIG. 3a shows a strip of a typical carrier which can be used by the
apparatus shown in FIG. 1, and logic tables for the photodetectors
A and B which are used by a microcomputer to identify the different
colored dye frames of a repeating series of dye frames in the
carrier;
FIG. 3b shows a cross section of the carrier shown in FIG. 3a;
FIG. 3c is a graph illustrating representative spectral sensitivity
of the dye frames of the carrier of FIG. 3b and the amplitude of
the signals produced by detectors A and B; and
FIG. 4 shows another embodiment where yellow and red LEDs
illuminate the same spot on the edge of a moving carrier.
DESCRIPTION OF THE PREFERRED EMBODIMENT
To facilitate an understanding of the present invention, reference
is first made to FIG. 3a which shows a typical section of a strip
of a carrier 14 which may be used in the printer 10 shown in FIG.
1. The carrier 14 comprises a black leader portion followed by a
repeating series of colored dye frames. The dye frames are
contiguous and each series includes in sequence yellow, magenta and
cyan dye frames. Each dye frame extends across the width of the
carrier 14. As will be described later, .[.an.]. .Iadd.low
frequency .Iaddend.LED 14a produces yellow light and .[.an.].
.Iadd.high frequency .Iaddend.LED 14b produces red light.
.Iadd.Frequency (f) is related to wavelength (.lambda.) by the
relationship: f=c/.lambda., wherein c is the speed of light.
.Iaddend.Light from these sources illuminates the same dye frame.
Located in the printer 10 and shown schematically in FIG. 3a is a
reader station which includes the LEDs 14a and 14b and two spaced
photodetectors A and B respectively. The LED 14a and photodetector
A are disposed adjacent to one edge of the carrier 14 and the LED
14b and photodetector B are disposed adjacent to the opposite edge
of the carrier 14. LEDs 14a and 14b can be constructed of
Gallium-Arsenide-Phosphide. These elements are located downstream
of the thermal print head 18. (See FIG. 1). They scan areas of the
carrier 14 which are outside of the area contacted by thermal
elements of the print head 18. These photodetectors A and B are
adapted to provide signals, the amplitude levels of which are a
function of the intensity of light from a corresponding LED light
source which passes through a dye frame. These signals are used to
identify the particular color of each dye frame. Yellow light
produced by LED 14a can only illuminate the photodetector A. Red
light produced by the LED 14b can only illuminate the photodetector
B.
Turning to FIG. 3c, LED 14b emits red light (635 nM typical) and
LED 14a yellow light (583 nM typical). The LEDs are high intensity
(80 mCd min), and are tightly focused (12 degrees=1/2 power).
Detectors A and B can be silicon phototransistors, saturating at
250 uW/cm.sup.2 at 930 nM light. The spectral response of the
typical sublimation yellow, magenta and cyan dyes are also shown. A
threshold signal amplitude level produced by the photodetectors A
and B can readily be selected to distinguish between logic "1" and
logic "0" as will be explained.
The following table can be interpreted with referece to FIG.
3c.
______________________________________ DYE YELLOW LOGIC RED LOGIC
FRAME LED (14a) LEVEL LED (14b) LEVEL
______________________________________ Cyan Blocked 0 Blocked 0
Magenta Blocked 0 Transmits 1 Yellow Transmits 1 Transmits 1 Black
(Leader) Blocked 0 Blocked 0
______________________________________
When illuminated so as to produce a signal level above the selected
threshold level, a photodetector will be considered to provide a
logic 1. Below this level it provides logic 0. Therefore as shown,
photodetector A will produce a signal level above the threshold
level (logic 1) and photodetector B will produce a signal level
above the threshold level (logic 1) when a yellow dye frame is
disposed adjacent to the photodectors A and B. When a cyan dye
frame is disposed over the photodectors A and B, they each produce
signals having levels below the threshold level (logic 0). As shown
in FIG. 1, the output of each photodetector is provided to an
amplifier 17a. The amplifier 17a drives a threshold detector 17b
which provides a logic "1" to a microcomputer 17 if the signal
produced by its photodetector is above the threshold level (see
FIG. 3c) and a logic "0" if it is below the threshold level. The
microcomputer 17 in accordance with an algorithm embodied in a
stored program determines the color of the dye frame above the
detectors. The logic pattern 0,0 for the black leader portion is
also shown. The logic pattern are also used by the microcomputer 17
to control the state of the printing cycle of a dye image. Although
the detectors A and B are shown a distance downstream of the print
head, this is only for clarity of illustration and they can be
disposed quite close to the print head.
At the end of every printing cycle, or when new donor is supplied,
the detectors A and B should be covered by the leader portion or by
a portion of a cyan dye frame (logic 0,0). When a print command is
given by an operator to the microcomputer 17, the carrier is
advanced until both detectors identify a yellow dye frame (logic
1,1). The print head 18 is now ready to print a yellow image. At
the end of printing the yellow image, the carrier 14 is advanced
until the logic state 0,1 is detected. This indicates that a
magenta dye frame is adjacent to the photodetectors A and B. After
a magenta image is printed, the carrier is advanced until both LEDs
14a and 14b are covered by the leading edge of a cyan dye frame.
That is logic 0,0. After a cyan image is printed, the carrier is
not advanced and the detectors A and B remain covered by the
trailing edge portion of the cyan dye frame until a new printing
cycle is initiated. If the apparatus should lose electrical power
at this point or be turned off, when power is restored, it need
only verify that the logic pattern is 0,0 and begin a new print
cycle.
With yellow and red LED detection, logic is used by the
microcomputer 17 to control carrier web advance after each dye
transfer and on power-down and power-up with a minimum wastage of
carrier. Although the detectors A and B are shown located
downstream past the print head, but it will be understood that they
also can be disposed upstream of the print head, preferably at a
distance equal to the length of a single dye frame.
FIG. 3b shows in cross-section the carrier 14. As shown, the
carrier 14 includes a support. On one surface of the support is a
slipping layer which bears against the heating elements of the
print head 18. On the other surface of the support is a barrier
layer. On the barrier layer is the dye layer. Heat from the heating
element passes through the slipping, support and barrier layers to
the dye layer. The dye is sublimed from this layer into a receiver
member 12 shown in FIG. 1.
Referring to FIG. 1, the receiver member 12 is in the form of a
sheet and is secured to a rotatable drum 16 which is mechanically
coupled to a drive mechanism 15. The drive mechanism 15
continuously advances the drum 16 and receiver sheet 12 along a
path past a stationary print head 18 during a cycle for addressing
heating elements of the print head. Print head 18 has a plurality
of heating elements 50, several of which are shown in FIG. 2, which
press against the slipping layer of the carrier member 14 and force
the carrier member against the receiver member 12. The carrier
member 14 is driven along a path from a supply spool 20 onto a
take-up spool 22 by a drive mechanism 23 coupled to the take-up
spool 22. The drive mechanisms 15 and 23 each include motors which
respectively continuously advance the carrier 14 and the receiver
12 relative to the heating elements 50 of the print head 18 as the
heating elements are selectively energized.
The heating elements are shown schematically in FIG. 2. When a
switch 54 is closed, a heating element 50 is connected to a
potential source V.sub.S. The microcomputer 17 controls the timing
of the energization of the heating elements. During printing, as
the members 12 and 14 are moved, dye image pixels are formed in the
receiver member 12. As noted above, these members are moved
continuously along paths relative to the print head during the
printing operation. The microcomputer 17 controls the operation of
the mechanisms 15 and 23.
The carrier member 14 is as noted above is formed with a repeating
series of thermally transferable dye frames. Each series includes
frames of yellow, magenta and cyan dye frames. The sequence of
yellow, magenta and cyan is repeated. A single series is used to
print one colored image in the receiver member 12. In the
disclosure, the term dye refers to a colored material which
transfers from the carrier to a receiver in response to energy
applied by the individual heating elements of the print head
18.
In the space saving embodiment of FIG. 4, LEDs 14a and 14b are
shown to illuminate the same spot on a carrier adjacent to an edge
of the carrier. The yellow and red light pass through dye frames of
the moving carrier and respectively illuminate their corresponding
photodetectors A and B. All the other elements of the apparatus can
be identical to that shown in FIG. 1. This arrangement further
minimizes carrier wastage.
This invention has been described in detail with particular
reference to certain preferred embodiments thereof, but it will be
understood that variations and modifications can be affected within
the spirit and scope of the invention.
* * * * *