The present invention relates to ink jet printers, and more particularly to an ink jet
printer for use in printing digital photographic images.
Digital photographic images provide significant advantages over conventional
photographic images in that they can be manipulated, stored, retrieved, and
transmitted using digital computer and data communication technology. Digital
photographic images can be generated either by scanning photographic images
captured on conventional photographic film, or directly by digital cameras employing
solid state image sensors. Hard copy display prints of digital color photographic
images are presently produced using thermal printers, electrographic
printers, scanners for exposing conventional silver halide photographic paper, and
ink jet printers.
The largest share of consumer photographic images are currently produced using
optical printers on photographic paper. It has been realized however that consumer
photofinishing would benefit from the advantages of digital image processing,
since the digital images can be digitally processed for better correction of
color balance and exposure, and can be digitally manipulated to add text or special
effects and can be combined with other images. The images captured on silver
halide photographic film are scanned to create color digital images, the color
digital images are processed to correct color balance and exposure, and then
printed using a color digital printer. Presently, the only digital printers for consumer
photofinishing that are available on the market are of the type that use a
scanning light beam to expose conventional silver halide photographic paper.
Such digital printers still use wet chemical processing to develop the exposed
photographic paper. Handling and disposal of the photo processing chemicals is
costly and takes up space, which also must be paid for, for example in the form of
rent. There is a need therefore for a digital photofinishing printer that avoids the
problems and costs associated with wet chemical photographic paper processing.
Of the competing technologies, thermal printing, electrography and ink jet printing;
thermal printing is limited by printing speed and cost of materials, and electrography
is limited by equipment cost and complexity. It appears therefore that ink jet
printing technology may be the best candidate to offer an improvement over
scanned silver halide printers for digital consumer photofinishing.
It is well known to employ ink jet printers to produce hard copy prints of digital
photographic images. Lower resolution images are produced on desk top ink jet
color printers having resolution in the range of 300 to 1200 dpi. Large format color
images are produced using graphic arts ink jet printers, see for example, published
European Patent Application EP 0 710 561 A2, published 08.05.1996,
entitled Printer and ink cartridge to be employed in same, by Ikkatai; and published
PCT application WO 97/28003, published 7 August 1997, entitled Heated
Inkjet Print Media Support System, by Rassmussen et al.. Although high resolution
color ink jet printing is likely to become a preferred mode for photofinishing,
existing ink jet printers are severely limited by their speed of throughput. There is
a need therefore for a high throughput, high resolution an ink jet printer for photo-finishing.
An ink jet printer for making photographic prints includes at least one paper supply
for holding a supply of print paper and a sheet paper transport belt arranged to
receive sheets of print paper from the at least one paper supply and transport the
sheets through the printer. A back printer is located between the at least one
paper supply and the paper transport belt for applying back prints to the print
paper. A full print width color ink jet print head located over a first portion of the
transport belt for printing an image on a paper sheet. An image sensor located in
front of the ink jet print head detects the edges of the paper sheet being transported
under the print head and a controller connected to the image sensor generates
a digital mask representing the area of the paper and applies the digital
mask to a digital image being printed, thereby preventing overspill printing onto
the belt. A paper dryer is located over a second portion of the transport belt, the
paper dryer including a source of flowing air for drying the ink image on the paper.
The ink jet printer according to the present invention has the following advantages.
Shrinkage of the printing paper in the drying section has no influence on
the print area. There is no waste at the cutting station. The printer has simplified
maintenance compared to a roll paper printer that cuts the paper after printing.
Perfect borderless prints can be produced. The printing rate is compatible with the
needs of commercial photofinishing operations.
The invention is described with reference to the following drawings, where similar
parts have been given similar numbers.
- Fig. 1
- is a schematic diagram of ink jet printer for making photographic prints
according to the present invention;
- Fig. 2
- is a schematic diagram of an alternative embodiment of the present
- Fig. 3
- is a schematic diagram of a further alternative embodiment of the present
- Fig. 4
- is a schematic diagram showing the paper cutter employed in the ink jet
printer according to the present invention;
- Fig. 5
- is a schematic diagram showing the image sensor employed in the ink
jet printer according to the present invention;
- Fig. 6
- is a schematic diagram illustrating the layout of an inkjet printer
according to the present invention;
- Fig. 7
- is a perspective view of a buffer section employed with a printer having
the layout shown in Fig. 6;
- Fig. 8
- is a detailed cross sectional view of the nozzle of a belt cleaner
employed with the present invention;
- Fig. 9
- is a perspective view of an air knife used in the paper drier of the present
- Fig. 10
- is a schematic perspective view of the belt transport in the region of the
print head according to the present invention.
Referring to Fig. 1, an ink jet printer, generally designated 10, for printing photographic
images according to the present invention includes a roll paper supply 12
supported by a holder 13, for supplying a web 14 of photographic ink jet print
paper. The photographic ink jet print paper comprises for example, 200 to 300
gram/m2 weight, 10 cm wide white paper having a special surface treatment for
receiving ink from the ink jet printer as is known in the art. The web of paper 14 is
supplied to a first pair of driven metering rollers 16.
A cut station 20 includes metering rollers 22 and a cutter 24. Referring to Fig. 4,
the cutter 24 includes a circular knife 400 that is moved across the paper path
against a fixed blade 402. The paper is held in a fixed position by a paper holder
404. The circular knife 400 is mounted on a knife carriage 406, which is supported
for sliding movement on a shaft 408. A cam 410 mounted on the knife carriage
406 engages the paper holder 404 to press the paper against the fixed blade 402
as the knife carriage is moved across the paper 14. In operation, the cut station
20 cuts individual sheets 25 of photographic ink jet print paper from the web 14.
Prior to cutting, the paper is advanced by metering roller 22 until a sensor 412
detects the leading edge of the paper web 14. The paper web 14 is then accurately
advanced a further distance by metering rollers 22 and stopped.
A back printer 26 is located between the metering rollers 16 and the metering
rollers 22 for printing information onto the back of web 14. The back printer 26 is,
for example a low resolution monochrome ink jet print head employing rapid drying
ink. Alternatively, the back printer 26 can be an impact printer. The back
printer 26 prints information such as order and frame number on the back side of
the web 14.
A pair of transport rollers 28 are located after the cutter 24 for delivering the cut
sheets 25 of photographic ink jet print paper to a vacuum belt transport. The
vacuum belt transport includes a first section having a belt 30 and a vacuum
plenum 33, and a second section having a belt 31 and two independently controllable
vacuum plenums 34 and 35. The first portion of the vacuum belt transport
conveys the cut sheets 25 under the print head 36. The second portion of the
vacuum belt transport includes a buffer zone controlled by vacuum plenum 34 to
isolate the motion of the second vacuum belt transport from the first while a sheet
is being printed by turning the vacuum off in plenum 34 until the previous picture
is printed. The length of the buffer zone is preferably as long as the longest
expected print, e.g. 30 cm for a 10 cm wide panoramic print.
As shown in Fig. 10, the vacuum belt 30 is perforated with holes 30' and is
mounted on a pair of vacuum belt support and drive rollers 100, 102. Vacuum belt
drive roller 102 is driven by a motor 104 to drive the vacuum belt 30. Roller 100 is
mounted in a bracket 106 for rotation about its axis 108. Bracket 106 is mounted
for rotation about an axis 110 perpendicular to the rotation of the roller axis 108
for controlling the tracking of belt 30 on the rollers 100 and 102. A bracket drive
motor 112 is coupled to bracket 106, for example by a ball and lead screw drive
114 for rotating the bracket 106 slightly about axis 110, thereby causing belt 30 to
move to the right or left on roller 100. A vacuum belt edge sensor 116, such as an
light emitting diode/photosensor pair, is mounted for sensing the edge 118 of belt
30, to provide feedback to a controller (described below) for accurately controlling
the position of belt 30 on the rollers 100 and 102.
A full width, high resolution color ink jet print head 36 is located over the first
vacuum belt transport 30 for printing a color photographic image onto the cut
sheets 25 as they are transported under the print head by vacuum belt transport
30. The minimum distance from the transport roller 28 to the print head 36 is
slightly greater than the maximum length of a cut sheet (e.g. 30 cm for a 10 cm
wide panoramic print). The full width ink jet print head 36 is, for the example, a
print head of the type shown in U.S. Patent No. 5,812,162, issued Sep. 22, 1998
to Silverbrook. Preferably the print head is slightly wider than the cut sheets 25
(e.g. 12 cm wide) and has a printing resolution of 1200 dpi. The preferred ink jet
print head 36 includes a plurality of print head components 38, 40, 42, 44, each
supplied with a different color of ink, for example cyan, magenta, yellow, and
black. The ink jet print head is capable of printing at a paper transport speed of 5
cm per second, or about 1000 prints per hour.
An image sensor 46, such as a linear CCD image sensor, is located in front of the
ink jet print head 36 for sensing all four edges of the cut paper sheets 25 as they
are transported by vacuum belt transport 30 under the print head 36. The linear
image sensor senses a line that is as wide as the print head 36 (i.e. slightly wider
that the sheets of print paper 25) and has a resolution of, for example 2700 pixels.
Referring to Fig. 5, an example of a suitable linear image sensor arrangement is
shown. The image sensor 46 includes a housing 500, a lens 502 for focusing an
image of the paper and transport belt onto an image sensing module 504, and a
light source 506 for illuminating the paper on the transport belt. A suitable image
sensing module 504 is the ILX533K CCD color linear image sensor sold by Sony
Corporation. An example of such an arrangement is shown in published PCT
patent application 96/38370.
A paper dryer 48, including a plurality of air knives 50 is located over the second
plenum 35 of belt transport 31 for drying the inked images before they reach the
end of the belt transport. Referring to Fig. 9, the air knives 50 include a plenum 52
having an input 51 for heated-compressed air, an exit slot 53, and a baffle 55 for
equalizing the pressure of the air along the exit slot 53. At a paper transport
speed of 5 cm/second, and an air flow to the air knives of about 10 meters/sec,
heated to not more than 80 C°, prints printed with a water base ink can be dried in
approximately 5 seconds. The paper dryer 48 is therefore about 25 cm long.
A belt cleaning station 57 for cleaning paper dust and any overspilled ink from the
transport belt 30 is provided on the side of the belt transport opposite to the ink jet
print head 36. As shown in more detail in Fig. 8 the cleaning station comprises a
cleaning head 800 that is as wide as the belt 30. The cleaning head 800 has an
external channel 802 for delivering a flow of pressurized air to the surface of the
belt 30 and an internal channel 804 for collecting the flow of air, along with any
dust or debris dislodged from the belt, and delivering the collected air to a filter
(not shown). The cleaning station is described in more detail in Applicants
copending German patent application No. 199 14 563.6.
Control electronics 54, including a digital processor such as a micro computer, is
connected to the various components of the printer for controlling the operation of
the printer 10. The operation of the printer 10, under control of control electronics
54, will now be described. The control electronics receives digital image data,
back print data, and print order instructions from an input device such as a film
scanning station, or a digital image processing station (not shown). During printing,
the control electronics 54 commands the printer to meter the printing paper
web 14 to the cutter 24 and print the back print information on the web 14 prior to
the paper being cut.
The paper sheet 25, bearing the back print information, is then cut from the web
14 by cutter 24 and advanced to the vacuum belt transport 30. The image sensor
46 detects the cut sheet 25 as it enters the vacuum belt. The image of the cut
sheet 25 is processed by the control electronics to detect the edges of the sheet
25, and create a print mask corresponding to the boundaries of the sheet. The
print mask is then applied to the digital image data, and the digital image data is
supplied to the ink jet print head 36 by control electronics 54 to print the image up
to the edges of the print sheet. In this way, overspill from the ink jet print head 36
onto the vacuum transport belt is avoided for borderless prints, and for bordered
prints, the print is properly aligned on the sheet, regardless of any slight misalignment
that may occur when the sheet is placed on the vacuum transport belt
The sheets of printing paper are transported continuously past the ink jet print
head 36. After being printed, the sheets pass through the print dryer 48, where
the ink is dried, and the prints are delivered to a finishing station (not shown)
where they are assembled into customer order envelopes.
Referring to Fig. 2, an alternative embodiment of the printer according to the present
invention will be described. In order to provide more flexibility in paper sizes,
the printer of Fig. 2 is provided with a second roll paper supply 12' supported by a
holder 13' for supplying a web 14' of paper that is narrower than the web 14 (e.g.
9 cm wide). The different sized paper webs 14 and 14' are selectively fed to cutter
24 under control of control electronics 54 depending upon the desired print size
contained in the print order instructions. Thus, control electronics 54 provides a
means for switching between paper supplies. Paper guides 56 and 56' are provided
for guiding the paper metered by metering rollers 16 and 16' respectively
into the metering rollers 22 of paper cutter 24. In this embodiment, the back
printer 26 is located between the metering rollers 22 and the transport rollers 28.
The control electronics 54 functions as described above to form a print mask from
the signal supplied sensor 46 that is combined with the digital image data so that
overspill onto the vacuum transport belt is avoided.
Referring to Fig. 3, a further alternative embodiment of an ink jet printer according
to the present invention will be described. This embodiment, like that shown in
Fig. 2, has two paper supplies 58 and 58', but in this case the paper supplies are
held by supports 61, 61' holding stacks of cut paper 60 and 60' having different
sizes respectively. Picking rollers 62 and 62' deliver sheets from the tops of the
stacks to paper transport rollers 64 and 64' respectively, and thence to paper
metering rollers 16.
As described above, the ink jet printers according to the invention are arranged to
transport the paper in a linear fashion from paper supply, through the printer and
the dryer, to the output. This arrangement results in a long, thin printer. Referring
to Fig. 6, a printer layout is shown where the printing and drying components are
arranged in parallel, and a print buffer 600 is arranged between the print head 36
and the dryer 48. The print buffer 600 isolates the effects of the dryer 48 on the
print head section of the paper transport and changes the direction of paper
transport of the paper 360° to deliver the paper from the print head 36 to the dryer
48. Referring to Fig. 7, the buffer section 600 includes a first vacuum belt section
700 that is narrower than the smallest paper width (e.g. 7 cm for a minimum paper
width of 9 cm), and extends in the same direction as the belt 30. A second section
702 extends in a direction perpendicular to the first section 700 for transporting
the cut sheet 25 to a third section 704 that delivers the cut sheet to the vacuum
belt 31 under dryer 48. As described above, the belt transports are vacuum belt
transports. Alternatively, electrostatic belt transports can be used for the portions
of the transport under the print head and the dryer. An example of an electrostatic
transport useful with the present invention is shown in European Published application
0 887 196 A2.
- ink jet printer
- 12, 12'
- roll paper supply
- 13, 13'
- 14, 14'
- 16, 16'
- metering roller
- cut station
- metering rollers
- cut sheet of print paper
- back printer
- transport rollers
- first vacuum belt
- vacuum belt holes
- second vacuum belt
- vacuum plenum
- vacuum plenum
- vacuum belt holes
- ink jet print head
- print head component
- print head component
- print head component
- print head component
- image sensor
- paper dryer
- air knife
- air input
- air exit slot
- control electronics
- 56, 56'
- paper guide
- cleaning station
- 58, 58'
- paper supply
- 60, 60'
- cut paper stack
- 61, 61'
- 62, 62'
- 64, 64'
- transport roller
- vacuum belt support roller
- vacuum belt drive roller
- vacuum belt drive motor
- roller mounting bracket
- roller rotation axis
- bracket rotation axis
- bracket drive motor
- ball and lead screw drive
- vacuum belt edge sensor
- edge of vacuum belt
- circular knife
- fixed blade
- paper holder
- knife carriage
- image sensing module
- light source
- print buffer
- first vacuum belt section
- second vacuum belt section
- third vacuum belt section
- cleaning head
- external channel
- internal channel