Digital Camera Patent Abstract
A recyclable, one-time use, print on demand, digital camera comprises
a housing. A chassis is contained within the housing. An image sensor
device, supported on said chassis, senses an image. A processor,
arranged in the housing, processes the image sensed by the image
sensor device. A replenishable supply of print media is supported
on the chassis. The supply of print media includes a former defining
a chamber and a quantity of print media carried by the former. A
pagewidth print head is arranged on the chassis for printing, on
demand, the sensed image on the print media as the print media traces
the print head. A power supply is arranged within the former of
the supply of print media for providing power to the image sensor
device, the processing means, the print head and a drive means for
the supply of print media. Digital Camera Patent Claims
I claim:
1. A recyclable, one-time use, print on demand, digital camera
comprising
a housing;
a chassis contained within the housing;
an image sensor device, supported on said chassis, for sensing
an image;
a processing means, arranged in the housing, for processing an
image sensed by said image sensor device;
a replenishable supply of print media supported on the chassis,
the supply of print media including a former defining a chamber
and a quantity of print media carried by the former;
a pagewidth print head arranged on the chassis for printing, on
demand, said sensed image on the print media as the print media
traverses the print head; and
a power supply means arranged within the former of the supply of
print media for providing power to the image sensor device, the
processing means, the print head and a drive means for the supply
of print media.
2. The camera of claim 1 in which the housing is recyclable.
3. The camera of claim 1 which includes a supply of ink for supplying
ink to the print head.
4. The camera of claim 3 in which the supply of ink is in the form
of an ink cartridge arranged on the chassis.
5. The camera of claim 4 in which the ink cartridge is refillable.
6. The camera of claim 1 in which the former is a right circular
cylinder rotatably supported on the chassis to be rotated by the
drive means, the supply of print media being wound around said cylinder
to be in roll form.
7. The camera of claim 6 in which the power supply means comprises
at least one battery with the former being rotatable about the battery
when the print head is printing said sensed image on said print
media.
8. The camera of claim 1 in which the print head is an ink jet
print head.
9. The camera of claim 8 in which the print head is formed by semi-conductor
fabrication techniques.
10. The camera of claim 9 in which the print head is manufactured
using microelectromechanical techniques.
Digital Camera Patent Description
FIELD OF THE INVENTION
The present invention relates to a low cost, recyclable, digital
camera. More particularly, the invention relates to a recyclable,
one-time use, print on demand, digital camera and specifically to
the arrangement of a power supply in such a camera.
BACKGROUND OF THE INVENTION
Recently, the concept of a "single use" disposable camera
has become an increasingly popular consumer item. Disposable camera
systems presently on the market normally includes an internal film
roll and a simplified gearing mechanism for traversing the film
roll across an imaging system including a shutter and lensing system.
The user, after utilizing a single film roll returns the camera
system to a film development center for processing. The film roll
is taken out of the camera system and processed and the prints returned
to the user. The camera system is then able to be re-manufactured
through the insertion of a new film roll into the camera system,
the replacement of any worn or wearable parts and the re-packaging
of the camera system in accordance with requirements. In this way,
the concept of a single use "disposable" camera is provided
to the consumer.
Recently, a camera system has been proposed by the present applicant
which provides for a handheld camera device having an internal print
head, image sensor and processing means such that images sensed
by the image sensing means, are processed by the processing means
and adapted to be instantly printed out by the printing means on
demand. The proposed camera system further discloses a system of
internal "print rolls" carrying print media such as film
on to which images are to be printed in addition to ink to supply
to the printing means for the printing process. The print roll is
further disclosed to be detachable and replaceable within the camera
system.
Unfortunately, such a system is likely to only be constructed at
a substantial cost and it would be desirable to provide for a more
inexpensive form of instant camera system which maintains a substantial
number of the quality aspects of the aforementioned arrangement
In particular, in any "disposable camera" it would be
desirable to provide for a simple and rapid form of replenishment
of the consumable portions in any disposable camera so that the
disposable camera can be readily and rapidly serviced by replenishment
and return to the market place.
It would be further desirable to provide for a simple means of
storage of replenishable portions of a disposable camera system
to allow for their rapid replenishment.
SUMMARY OF THE INVENTION
According to the invention, there is provided, a recyclable, one-time
use, print on demand, digital camera comprising
a housing;
a chassis contained within the housing;
an image sensor device, supported on said chassis, for sensing
an image;
a processing means, arranged in the housing, for processing an
image sensed by said image sensor device;
a replenishable supply of print media supported on the chassis,
the supply of print media including a former defining a chamber
and a quantity of print media carried by the former;
a pagewidth print head arranged on the chassis for printing, on
demand, said sensed image on the print media as the print media
traverses the print head; and
a power supply means arranged within the former of the supply of
print media for providing power to the image sensor device, the
processing means, the print head and a drive means for the supply
of print media.
As indicated, the camera is recyclable. Accordingly, the housing
may be recyclable. The housing may comprise a pair of shells of
a re-usable, plastics material. The shells may be secured together
to surround and enclose the chassis.
The camera may include a supply of ink for supplying ink to the
print head. The supply of ink may be in the form of an ink cartridge
arranged on the chassis. Due to the recyclability of the camera,
the ink cartridge may be refillable.
The former may be a right circular cylinder rotatably supported
on the chassis to be rotated by the drive means, the supply of print
media being wound around said cylinder to be in roll form.
The power supply means may comprise at least one battery with the
former being rotatable about the battery when the print head is
printing said sensed image on said print media. In a preferred embodiment,
the camera includes two batteries arranged end-to-end. The length
of the two batteries in end-to-end relationship may be approximately
the same as that of the former so that, in use, each visible end
of a battery within the former electrically engages an electrical
contact carried on each of opposed end members of the chassis. One
of said end members may be removable for removing the former, after
depletion of the supply of print media, and the batteries to be
able to replace the depleted supply of print media with a new supply
and to insert fresh batteries when recycling the camera.
The print head may be an ink jet print head. More particularly,
the print head may be formed by semi-conductor fabrication techniques.
In particular, the print head is, preferably, manufactured using
microelectromechanical techniques.
BRIEF DESCRIPTION OF THE DRAWINGS
Notwithstanding any other forms which may fall within the scope
of the present invention, preferred forms of the invention will
now be described, by way of example only, with reference to the
accompanying drawings in which:
FIG. 1 illustrated a side front perspective view of the assembled
camera of the preferred embodiment;
FIG. 2 illustrates a back side perspective view, partly exploded,
of the preferred embodiment;
FIG. 3 is a side perspective view of the chassis of the preferred
embodiment;
FIG. 4 is a side perspective view of the chassis illustrating the
insertion of the electric motors;
FIG. 5 is an exploded perspective of the ink supply mechanism of
the preferred embodiment;
FIG. 6 is a side perspective of the assembled form of the ink supply
mechanism of the preferred embodiment;
FIG. 7 is a front perspective view of the assembled form of the
ink supply mechanism of the preferred embodiment;
FIG. 8 is an exploded perspective of the platten unit of the preferred
embodiment;
FIG. 9 is a side perspective view of the assembled form of the
platten unit;
FIG. 10 is also a perspective view of the assembled form of the
platten unit;
FIG. 11 is an exploded perspective unit of the print head recapping
mechanism of the preferred embodiment;
FIG. 12 is a close up exploded perspective of the recapping mechanism
of the preferred embodiment;
FIG. 13 is an exploded perspective of the ink supply cartridge
of the preferred embodiment;
FIG. 14 is a close up perspective, partly in section of the internal
portions of the ink supply cartridge in an assembled form;
FIG. 15 is a schematic block diagram of one form of chip layer
of the image capture and processing chip of the preferred embodiment;
FIG. 16 is an exploded perspective illustrating the assembly process
of the preferred embodiment;
FIG. 17 illustrates a front exploded perspective view of the assembly
process of the preferred embodiment;
FIG. 18 illustrates a side perspective view of the assembly process
of the preferred embodiment;
FIG. 19 illustrates a side perspective view of the assembly process
of the preferred embodiment;
FIG. 20 is a perspective view illustrating the insertion of the
platten unit in the preferred embodiment;
FIG. 21 illustrates the interconnection of the electrical components
of the preferred embodiment;
FIG. 22 illustrates the process of assembling the preferred embodiment;
and
FIG. 23 is a perspective view further illustrating the assembly
process of the preferred embodiment.
DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS
Turning initially simultaneously to FIG. 1, and FIG. 2 there is
illustrated perspective views of an assembled camera constructed
in accordance with the preferred embodiment with FIG. 1 showing
a front side perspective view and FIG. 2 showing a back side perspective
view. The camera 1 includes a paper or plastic film jacket 2 which
can include simplified instructions 3 for the operation of the camera
system 1. The camera system 1 includes a first "take"
button 4 which is depressed to capture an image. The captured image
is output via output slot 6. A further copy of the image can be
obtained through depressing a second "printer copy" button
7 whilst an LED light 5 is illuminated. The camera system also provides
the usual view finder 8 in addition to a CCD image capture/lensing
system 9.
The camera system 1 provides for a standard number of output prints
after which the camera system 1 ceases to function. A prints left
indicator slot 10 is provided to indicate the number of remaining
prints. A refund scheme at the point of purchase is assumed to be
operational for the return of used camera systems for recycling.
Turning now to FIG. 3, the assembly of the camera system is based
around an internal chassis 12 which can be a plastic injection molded
part. A pair of paper pinch rollers 28, 29 utilized for decurling
are snap fitted into corresponding frame holes e.g. 26, 27.
As shown in FIG. 4, the chassis 12 includes a series of mutually
opposed prongs e.g. 13, 14 into which is snapped fitted a series
of electric motors 16, 17. The electric motors 16, 17 can be entirely
standard with the motor 16 being of a stepper motor type and include
a cogged end portion 19, 20 for driving a series of gear wells.
A first set of gear wheels is provided for controlling a paper cutter
mechanism and a second set is provided for controlling print roll
movement.
Turning next to FIGS. 5 to 7, there is illustrated an ink supply
mechanism 40 utilized in the camera system. FIG. 5 illustrates a
back exploded perspective view, FIG. 6 illustrates a back assembled
view and FIG. 7 illustrates a front assembled view. The ink supply
mechanism 40 is based around an ink supply cartridge 42 which contains
printer ink and a print head mechanism for printing out pictures
on demand. The ink supply cartridge 42 includes a side aluminum
strip 43 which is provided as a shear strip to assist in cutting
images from a paper roll.
A dial mechanism 44 is provided for indicating the number of "prints
left". The dial mechanism 44 is snap fitted through a corresponding
mating portion 46 so as to be freely rotatable.
As shown in FIG. 6, the print head includes a flexible PCB strip
47 which interconnects with the print head and provides for control
of the print head. The interconnection between the Flex PCB strip
and an image sensor and print head chip can be via Tape Automated
Bonding (TAB) Strips 51, 58. A molded aspherical lens and aperture
shim 50 (FIG. 5) is also provided for imaging an image onto the
surface of the image sensor chip normally located within cavity
53 and a light box module or hood 52 is provided for snap fitting
over the cavity 53 so as to provide for proper light control. A
series of decoupling capacitors 34 eg. can also be provided. Further
a plug 121 (FIG. 7) is provided for re-plugging ink holes after
refilling. A series of guide prongs eg. 55-57 are further provided
for guiding the flexible PCB strip 47.
The ink supply mechanism 40 interacts with a platten unit which
guides print media under a print head located in the ink supply
mechanism. FIG. 8 shows an exploded view of the platten unit 60,
while FIGS. 9 and 10 show assembled views of the platten unit. The
platten unit 60 includes a first pinch roller 61 which is snap fitted
to one side of a platten base 62. Attached to a second side of the
platten base 62 is a cutting mechanism 63 which traverses the platten
by means of a rod 64 having a screwed thread which is rotated by
means of cogged wheel 65 which is also fitted to the platten 62.
The screwed thread engages a block 67 which includes a cutting wheel
68 fastened via a fastener 69. Also mounted to the block 67 is a
counter actuator which includes a prong 71. The prong 71 acts to
rotate the dial mechanism 44 of FIG. 6 upon the return traversal
of the cutting wheel. As shown previously in FIG. 6, the dial mechanism
44 includes a cogged surface which interacts with pawl lever 73,
thereby maintaining a count of the number of photographs taken on
the surface of dial mechanism 44. The cutting mechanism 63 is inserted
into the platten base 62 by means of a snap fit via receptacle e.g.
74.
The platten 62 includes an internal recapping mechanism 80 for
recapping the print head when not in use. The recapping mechanism
80 includes a sponge portion 81 and is operated via a solenoid coil
so as to provide for recapping of the print head. In the preferred
embodiment, there is provided an inexpensive form of print head
re-capping mechanism provided for incorporation into a handheld
camera system so as to provide for print head re-capping of an ink
jet print head.
FIG. 11 illustrates an exploded view of the recapping mechanism
whilst FIG. 12 illustrates a close up of the end portion thereof.
The re-capping mechanism 80 is structured around a solenoid including
a 16 turn coil 75 which can comprise insulated wire. The coil 75
is turned around a first stationary solenoid arm 76 which is mounted
on a bottom surface of the platten 62 (FIG. 8) and includes a post
portion 77 to magnify effectiveness of operation. The arm 76 can
comprise a ferrous material.
A second moveable arm 78 of the solenoid actuator is also provided,
the arm 78 being moveable and also made of ferrous material. Mounted
on the arm is a sponge portion surrounded by an elastomer strip
79. The elastomer strip 79 is of a generally arcuate cross-section
and acts as a leaf spring against the surface of the print head
ink supply cartridge 42 (FIG. 5) so as to provide for a seal against
the surface of the print head ink supply cartridge 42. In the quiescent
position elastomer spring units 87, 88 act to resiliently deform
the elastomer seal 79 against the surface of the ink supply unit
42.
When it is desired to operate the print head unit, upon the insertion
of paper, the solenoid coil 75 is activated so as to cause the arm
78 to move down to be adjacent to the end plate 76. The arm 78 is
held against end plate 76 while the print head is printing by means
of a small "keeper current" in coil 75. Simulation results
indicate that the keeper current can be significantly less than
the actuation current. Subsequently, after photo printing, the paper
is guillotined by the cutting mechanism 63 of FIG. 8 acting against
Aluminum Strip 43 of FIG. 5, and rewound so as to clear the area
of the re-capping mechanism 80. Subsequently, the current is turned
off and springs 87, 88 return the arm 78 so that the elastomer seal
is again resting against the print head ink supply cartridge.
It can be seen that the preferred embodiment provides for a simple
and inexpensive means of re-capping a print head through the utilization
of a solenoid type device having a long rectangular form. Further,
the preferred embodiment utilizes minimal power in that currents
are only required whilst the device is operational and additionally,
only a low keeper current is required whilst the print head is printing.
Turning next to FIG. 13 and 14, FIG. 13 illustrates an exploded
perspective of the ink supply cartridge 42 whilst FIG. 14 illustrates
a close up sectional view of a bottom of the ink supply cartridge
with the print bead unit in place. The ink supply cartridge 42 is
based around a pagewidth print head 102 which comprises a long slither
of silicon having a series of holes etched on the back surface for
the supply of ink to a front surface of the silicon wafer for subsequent
ejection via a micro electro mechanical system. The form of ejection
can be many different forms such as those set out in the tables
below.
Of course, many other ink jet technologies, as referred to the
attached tables below, can also be utilized when constructing a
print head unit 102. The fundamental requirement of the ink supply
cartridge 42 being the supply of ink to a series of color channels
etched through the back surface of the print head 102. In the description
of the preferred embodiment, it is assumed that a three color printing
process is to be utilized so as to provide full color picture output.
Hence, the print supply unit 42 includes three ink supply reservoirs
being a cyan reservoir 104, a magenta reservoir 105 and a yellow
reservoir 106. Each of these reservoirs is required to store ink
and includes a corresponding sponge type material 107-109 which
assists in stabilizing ink within the corresponding ink channel
and therefore preventing the ink from sloshing back and forth when
the print head is utilized in a handheld camera system. The reservoirs
104, 105, 106 are formed through the mating of first exterior plastic
piece 110 mating with a second base piece) 111.
At a first end of the base piece II includes a series of air inlet
113-115. The air inlet leads to a corresponding winding channel
which is hydrophobically treated so as to act as an ink repellent
and therefore repel any ink that may flow along the air inlet channel.
The air inlet channel takes a convoluted path further assisting
in resisting any ink flow out of the chambers 104-106. An adhesive
tape portion 117 is provided for sealing the channels within end
portion 118.
At the top end, there is included a series of refill holes for
refilling corresponding ink supply chambers 104, 105, 106. A plug
121 is provided for sealing the refill holes.
Turning now to FIG. 14, there is illustrated a close up perspective
view, partly in section through the ink supply cartridge 42 of FIG.
13 when formed as a unit. The ink supply cartridge includes the
three color ink reservoirs 104, 105, 106 which supply ink to different
portions of the back surface of print head 102 which includes a
series of apertures 128 defined therein for carriage of the ink
to the front surface.
The ink supply unit includes two guide walls 124, 125 which separate
the various ink chambers and are tapered into an end portion abutting
the surface of the print head 102. The guide walls are further mechanically
supported at regular spaces by block portions 126 which are placed
at regular intervals along the length of the print head supply unit.
The block portions 126 leave space at portions close to the back
of print head 102 for the flow of ink around the back surface thereof
The print head supply unit is preferably formed from a multi-part
plastic injection mould and the mould pieces eg. 10, 11 (FIG. 1)
snap together around the sponge pieces 107, 109. Subsequently, a
syringe type device can be inserted in the ink refill holes and
the ink reservoirs filled with ink with the air flowing out of the
air outlets 113-115. Subsequently, the adhesive tape portion 117
and plug 121 are attached and the print head tested for operation
capabilities. Subsequently, the ink supply cartridge 42 can be readily
removed for refilling by means of removing the ink supply cartridge,
performing a washing cycle, and then utilizing the holes for the
insertion of a refill syringe filled with ink for refilling the
ink chamber before returning the ink supply cartridge 42 to a camera.
Turning now to FIG. 15, there is shown an example layout of the
Image Capture and Processing Chip (ICP) 48. The Image Capture and
Processing Chip 48 provides most of the electronic functionality
of the camera with the exception of the print head chip. The chip
48 is a highly integrated system. It combines CMOS image sensing,
analog to digital conversion, digital image processing, DRAM storage,
ROM, and miscellaneous control functions in a single chip.
The chip is estimated to be around 32 mm.sup.2 using a leading
edge 0.18 micron CMOS/DRAM/APS process. The chip size and cost can
scale somewhat with Moore's law, but is dominated by a CMOS active
pixel sensor array 201, so scaling is limited as the sensor pixels
approach the diffraction limit.
The ICP 48 includes CMOS logic, a CMOS image sensor, DRAM, and
analog circuitry. A very small amount of flash memory or other non-volatile
memory is also preferably included for protection against reverse
engineering.
Alternatively, the ICP can readily be divided into two chips: one
for the CMOS imaging array, and the other for the remaining circuitry.
The cost of this two chip solution should not be significantly different
than the single chip ICP, as the extra cost of packaging and bond-pad
area is somewhat cancelled by the reduced total wafer area requiring
the color filter fabrication steps.
The ICP preferably contains the following functions:
Function 1.5 megapixel image sensor Analog Signal Processors Image
sensor column decoders Image sensor row decoders Analogue to Digital
Conversion (ADC) Column ADC's Auto exposure 12 Mbits of DRAM DRAM
Address Generator Color interpolator Convolver Color ALU Halftone
matrix ROM Digital halfioning Print head interface 8 bit CPU core
Program ROM Flash memory Scratchpad SRAM Parallel interface (8 bit)
Motor drive transistors (5) Clock PLL JTAG test interface Test circuits
Busses Bond pads
The CPU, DRAM, Image sensor, ROM, Flash memory, Parallel interface,
JTAG interface and ADC can be vendor supplied cores. The ICP is
intended to run on 1.5V to minimize power consumption and allow
convenient operation from two AA type battery cells.
FIG. 15 illustrates a layout of the ICP 48. The ICP 48 is dominated
by the imaging array 201, which consumes around 80% of the chip
area. The imaging array is a CMOS 4 transistor active pixel design
with a resolution of 1,500.times.1,000. The array can be divided
into the conventional configuration, with two green pixels, one
red pixel, and one blue pixel in each pixel group. There are 750.times.500
pixel groups in the imaging array.
The latest advances in the field of image sensing and CMOS image
sensing in particular can be found in the October, 1997 issue of
IEEE Transactions on Electron Devices and, in particular, pages
1689 to 1968. Further, a specific implementation similar to that
disclosed in the present application is disclosed in Wong et. al,
"CMOS Active Pixel Image Sensors Fabricated Using a 1.8V, 0.25
.mu.m CMOS Technology", IEDM 1996, page 915.
The imaging array uses a 4 transistor active pixel design of a
standard configuration. To minimize chip area and therefore cost,
the image sensor pixels should be as small as feasible with the
technology available. With a four transistor cell, the typical pixel
size scales as 20 times the lithographic feature size. This allows
a minimum pixel area of around 3.6 .mu.m.times.3.6 .mu.m. However,
the photosite must be substantially above the diffraction limit
of the lens. It is also advantageous to have a square photosite,
to maximize the margin over the diffraction limit in both horizontal
and vertical directions. In this case, the photosite can be specified
as 2.5 .mu.m.times.2.5 .mu.m. The photosite can be a photogate,
pinned photodiode, charge modulation device, or other sensor.
The four transistors are packed as an `L` shape, rather than a
rectangular region, to allow both the pixel and the photosite to
be square. This reduces the transistor packing density slightly,
increasing pixel size. However, the advantage in avoiding the diffraction
limit is greater than the small decrease in packing density.
The transistors also have a gate length which is longer than the
minimum for the process technology. These have been increased from
a drawn length of 0.18 micron to a drawn length of 0.36 micron.
This is to improve the transistor matching by making the variations
in gate length represent a smaller proportion of the total gate
length.
The extra gate length, and the `L` shaped packing, mean that the
transistors use more area than the minimum for the technology. Normally,
around 8 .mu.m.sup.2 would be required for rectangular packing.
Preferably, 9.75 .mu.m.sup.2 has been allowed for the transistors.
The total area for each pixel is 16 .mu.m.sup.2, resulting from
a pixel size of 4 .mu.m.times.4 .mu.m. With a resolution of 1,500.times.1,000,
the area of the imaging array 101 is 6,000 .mu.m.times.4,000 .mu.m,
or 24 mm.sup.2.
The presence of a color image sensor on the chip affects the process
required in two major ways:
The CMOS fabrication process should be optimized to minimize dark
current.
Color filters are required. These can be fabricated using dyed
photosensitive polyimides, resulting in an added process complexity
of three spin coatings, three photolithographic steps, three development
steps, and three hardbakes.
There are 15,000 analog signal processors (ASPs) 205, one for each
of the columns of the sensor. The ASPs amplify the signal, provide
a dark current reference, sample and hold the signal, and suppress
the fixed pattern noise (FPN).
There are 375 analog to digital converters 206, one for each four
columns of the sensor array. These may be delta-sigma or successive
approximation type ADC's. A row of low column ADC's are used to
reduce the conversion speed required, and the amount of analog signal
degradation incurred before the signal is converted to digital.
This also eliminates the hot spot (affecting local dark current)
and the substrate coupled noise that would occur if a single high
speed ADC was used. Each ADC also has two four bit DAC's which trim
the offset and scale of the ADC to further reduce FPN variations
between columns. These DAC's are controlled by data stored in flash
memory during chip testing.
The column select logic 204 is a 1:1500 decoder which enables the
appropriate digital output of the ADCs onto the output bus. As each
ADC is shared by four columns, the least significant two bits of
the row select control 4 input analog multiplexors.
A row decoder 207 is a 1:1000 decoder which enables the appropriate
row of the active pixel sensor array. This selects which of the
1000 rows of the imaging array is connected to analog signal processors.
As the rows are always accessed in sequence, the row select logic
can be implemented as a shift register.
An auto exposure system 208 adjusts the reference voltage of the
ADC 205 in response to the maximum intensity sensed during the previous
frame period. Data from the green pixels is passed through a digital
peak detector. The peak value of the image frame period before capture
(the reference frame) is provided to a digital to analogue converter(DAC),
which generates the global reference voltage for the column ADCs.
The peak detector is reset at the beginning of the reference frame.
The minimum and maximum values of the three RGB color components
are also collected for color correction.
The second largest section of the chip is consumed by a DRAM 210
used to hold the image. To store the 1,500.times.1,000 image from
the sensor without compression, 1.5 Mbytes of DRAM 210 are required.
This equals 12 Mbits, or slightly less than 5% of a 256 Mbit DRAM.
The DRAM technology assumed is of the 256 Mbit generation implemented
using 0.18 .mu.m CMOS.
Using a standard 8F cell, the area taken by the memory array is
3.11 mm.sup.2. When row decoders, column sensors, redundancy, and
other factors are taken into account, the DRAM requires around 4
mm.sup.2.
This DRAM 210 can be mostly eliminated if analog storage of the
image signal can be accurately maintained in the CMOS imaging array
for the two seconds required to print the photo. However, digital
storage of the image is preferable as it is maintained without degradation,
is insensitive to noise, and allows copies of the photo to be printed
considerably later.
A DRAM address generator 211 provides the write and read addresses
to the DRAM 210. Under normal operation, the write address is determined
by the order of the data read from the CMOS image sensor 201. This
will typically be a simple raster format. However, the data can
be read from the sensor 201 in any order, if matching write addresses
to the DRAM are generated. The read order from the DRAM 210 will
normally simply match the requirements of a color interpolator and
the print head. As the cyan, magenta, and yellow rows of the print
head are necessarily offset by a few pixels to allow space for nozzle
actuators, the colors are not read from the DRAM simultaneously.
However, there is plenty of time to read all of the data from the
DRAM many times during the printing process. This capability is
used to eliminate the need for FIFOs in the print head interface,
thereby saving chip area. All three RGB image components can be
read from the DRAM each time color data is required. This allows
a color space converter to provide a more sophisticated conversion
than a simple linear RGB to CMY conversion.
Also, to allow two dimensional filtering of the image data without
requiring line buffers, data is re-read from the DRAM array.
The address generator may also implement image effects in certain
models of camera. For example, passport photos are generated by
a manipulation of the read addresses to the DRAM. Also, image framing
effects (where the central image is reduced), image warps, and kaleidoscopic
effects can all be generated by manipulating the read addresses
of the DRAM.
While the address generator 211 may be implemented with substantial
complexity if effects are built into the standard chip, the chip
area required for the address generator is small, as it consists
only of address counters and a moderate amount of random logic.
A color interpolator 214 converts the interleaved pattern of red,
2.times.green, and blue pixels into RGB pixels. It consists of three
8 bit adders and associated registers. The divisions are by either
2 (for green) or 4 (for red and blue) so they can be implemented
as fixed shifts in the output connections of the adders.
A convolver 215 is provided as a sharpening filter which applies
a small convolution kernel (5.times.5) to the red, green, and blue
planes of the image. The convolution kernel for the green plane
is different from that of the red and blue planes, as green has
twice as many samples. The sharpening filter has five functions:
To improve the color interpolation from the linear interpolation
provided by the color interpolator, to a close approximation of
a sinc interpolation.
To compensate for the image `softening` which occurs during digitization.
To adjust the image sharpness to match average consumer preferences,
which are typically for the image to be slightly sharper than reality.
As the single use camera is intended as a consumer product, and
not a professional photographic products, the processing can match
the most popular settings, rather than the most accurate.
To suppress the sharpening of high frequency (individual pixel)
noise. The function is similar to the `unsharp mask` process.
To antialias Image Warping.
These functions are all combined into a single convolution matrix.
As the pixel rate is low (less than 1 Mpixel per second) the total
number of multiplies required for the three color channels is 56
million multiplies per second. This can be provided by a single
multiplier. Fifty bytes of coefficient ROM are also required.
A color ALU 113 combines the functions of color compensation and
color space conversion into the one matrix multiplication, which
is applied to every pixel of the frame. As with sharpening, the
color correction should match the most popular settings, rather
than the most accurate.
A color compensation circuit of the color ALU provides compensation
for the lighting of the photo. The vast majority of photographs
are substantially improved by a simple color compensation, which
independently normalizes the contrast and brightness of the three
color components.
A color look-up table (CLUT) 212 is provided for each color component.
These are three separate 256.times.8 SRAMs, requiring a total of
6,144 bits. The CLUTs are used as part of the color correction process.
They are also used for color special effects, such as stochastically
selected "wild color" effects.
A color space conversion system of the color ALU converts from
the RGB color space of the image sensor to the CMY color space of
the printer. The simplest conversion is a 1's complement of the
RGB data. However, this simple conversion assumes perfect linearity
of both color spaces, and perfect dye spectra for both the color
filters of the image sensor, and the ink dyes. At the other extreme
is a tri-linear interpolation of a sampled three dimensional arbitrary
transform table. This can effectively match any non-linearity or
differences in either color space. Such a system is usually necessary
to obtain good color space conversion when the print engine works
on the color electrophotographic principle.
However, since the non-linearity of a halftoned ink jet output
is very small, a simpler system can be used. A simple matrix multiply
can provide excellent results. This requires nine multiplies and
six additions per contone pixel. However, since the contone pixel
rate is low (less than 1 Mpixel/sec) these operations can share
a single multiplier and adder. The multiplier and adder are used
in a color ALU which is shared with the color compensation function.
Digital halftoning can be performed as a dispersed dot ordered
dither using a stochastic optimized dither cell. A halftone matrix
ROM 116 is provided for storing dither cell coefficients. A dither
cell size of 32.times.32 is adequate to ensure that the cell repeat
cycle is not visible. The three colors--cyan, magenta, and yellow--are
all dithered using the same cell, to ensure maximum co-positioning
of the ink dots. This minimizes `muddying` of the mid-tones which
results from bleed of dyes from one dot to adjacent dots while still
wet. The total ROM size required is 1 KByte, as the one ROM is shared
by the halftoning units for each of the three colors.
The digital halftoning used is dispersed dot ordered dither with
stochastic optimized dither matrix. While dithering does not produce
an image quite as `sharp` as error diffusion, it does produce a
more accurate image with fewer artifacts. The image sharpening produced
by error diffusion is artificial, and less controllable and accurate
than `unsharp mask` filtering performed in the contone domain. The
high print resolution (1,600 dpi.times.1,600 dpi) results in excellent
quality when using a well formed stochastic dither matrix.
Digital halftoning is performed by a digital halftoning unit 217
using a simple comparison between the contone information from the
DRAM 210 and the contents of the dither matrix 216. During the halftone
process, the resolution of the image is changed from the 250 dpi
of the captured contone image to the 1,600 dpi of the printed image.
Each contone pixel is converted to an average of 40.96 halftone
dots.
The ICP incorporates an 16 bit microcontroller CPU core 219 to
run the miscellaneous camera functions, such as reading the buttons,
controlling the motor and solenoids, setting up the hardware, and
authenticating the refill station. The processing power required
by the CPU is very modest, and a wide variety of processor cores
can be used. As the entire CPU program is run from a small ROM 220.
Program compatibility between camera versions is not important,
as no external programs are run. A 2 Mbit (256 Kbyte) program and
data ROM 220 is included on chip. Most of this ROM space is allocated
to data for outline graphics and fonts for specialty cameras. The
program requirements are minor. The single most complex task is
the encrypted authentication of the refill station. The ROM requires
a single transistor per bit.
A Flash memory 221 may be used to store a 128 bit authentication
code. This provides higher security than storage of the authentication
code in ROM, as reverse engineering can be made essentially impossible.
The Flash memory is completely covered by third level metal, making
the data impossible to extract using scanning probe microscopes
or electron beams. The authentication code is stored in the chip
when manufactured. At least two other Flash bits are required for
the authentication process: a bit which locks out reprogramming
of the authentication code, and a bit which indicates that the camera
has been refilled by an authenticated refill station. The flash
memory can also be used to store FPN correction data for the imaging
array. Additionally, a phase locked loop rescaling parameter is
provided for scaling the clocking cycle to an appropriate correct
time. The clock frequency does not require crystal accuracy since
no date functions are provided. To eliminate the cost of a crystal,
an on chip oscillator with a phase locked loop 124 is used. As the
frequency of an on-chip oscillator is highly variable from chip
to chip, the frequency ratio of the oscillator to the PLL is digitally
trimmed during initial testing. The value is stored in Flash memory
121. This allows the clock PLL to control the ink-jet heater pulse
width with sufficient accuracy.
A scratchpad SRAM is a small static RAM 222 with a 6T cell. The
scratchpad provided temporary memory for the 16 bit CPU. 1024 bytes
is adequate.
A print head interface 223 formats the data correctly for the print
head. The print head interface also provides all of the timing signals
required by the print head. These timing signals may vary depending
upon temperature, the number of dots printed simultaneously, the
print medium in the print roll, and the dye density of the ink in
the print roll.
The following is a table of external connections to the print head
interface:
Connection Function Pins DataBits[0-7] Independent serial data
to the eight segments of 8 the print head BitClock Main data clock
for the 1 print head ColorEnable[0-2] Independent enable signals
for the CMY 3 actuators, allowing different pulse times for each
color. BankEnable[0-1] Allows either simultaneous or interleaved
2 actuation of two banks of nozzles. This allows two different print
speed/power consumption tradeoffs NozzleSelect Selects one of 32
banks of nozzles for 5 [0-4] simultaneous actuation ParallelXferClock
Loads the parallel transfer register with the 1 data from the shift
registers Total 20
The print head utilized is composed of eight identical segments,
each 1.25 cm long. There is no connection between the segments on
the print head chip. Any connections required are made in the external
TAB bonding film, which is double sided. The division into eight
identical segments is to simplify lithography using wafer steppers.
The segment width of 1.25 cm fits easily into a stepper field. As
the print head chip is long and narrow (10 cm.times.0.3 mm), the
stepper field contains a single segment of 32 print head chips.
The stepper field is therefore 1.25 cm.times.1.6 cm. An average
of four complete print heads are patterned in each wafer step.
A single BitClock output line connects to all 8 segments on the
print head. The 8 DataBits lines lead one to each segment, and are
clocked in to the 8 segments on the print head simultaneously (on
a BitClock pulse). For example, dot 0 is transferred to segment.sub.0,
dot 750 is transferred to segment.sub.1, dot 1500 to segment.sub.2
etc simultaneously.
The ParallelXferlock is connected to each of the 8 segments on
the print head, so that on a single pulse, all segments transfer
their bits at the same time.
The NozzleSelect, BankEnable and ColorEnable lines are connected
to each of the 8 segments, allowing the print head interface to
independently control the duration of the cyan, magenta, and yellow
nozzle energizing pulses. Registers in the Print Head Interface
allow the accurate specification of the pulse duration between 0
and 6 ms, with a typical duration of 2 ms to 3 ms.
A parallel interface 125 connects the ICP to individual static
electrical signals. The CPU is able to control each of these connections
as memory mapped I/O via a low speed bus.
The following is a table of connections to the parallel interface:
Connection Direction Pins Paper transport stepper motor Output
4 Capping solenoid Output 1 Copy LED Output 1 Photo button Input
1 Copy button Input 1 Total 8
A serial interface is also included to allow authentication of
the refill station. This is included to ensure that the cameras
are only refilled with paper and ink at authorized refill stations,
thus preventing inferior quality refill industry from occurring.
The camera must authenticate the refill station, rather than the
other way around. The secure protocol is communicated to the refill
station via a serial data connection. Contact can be made to four
gold plated spots on the ICP/print head TAB by the refill station
as the new ink is injected into the print head.
Seven high current drive transistors e.g. 227 are required. Four
are for the four phases of the main stepper motor two are for the
guillotine motor, and the remaining transistor is to drive the capping
solenoid. These transistors are allocated 20,000 square microns
(600,000 F) each. As the transistors are driving highly inductive
loads, they must either be turned off slowly, or be provided with
a high level of back EMF protection. If adequate back EMF protection
cannot be provided using the chip process chosen, then external
discrete transistors should be used. The transistors are never driven
at the same time as the image sensor is used. This is to avoid voltage
fluctuations and hot spots affecting the image quality. Further,
the transistors are located as far away from the sensor as possible.
A standard JTAG (Joint Test Action Group) interface 228 is included
in the ICP for testing purposes and for interrogation by the refill
station. Due to the complexity of the chip, a variety of testing
techniques are required, including BIST (Built In SelfTest) and
functional block isolation. An overhead of 10% in chip area is assumed
for chip testing circuitry for the random logic portions. The overhead
for the large arrays the image sensor and the DRAM) is smaller.
The JTAG interface is also used for authentication of the refill
station. This is included to ensure that the cameras are only refilled
with quality paper and ink at a properly constructed refill station,
thus preventing inferior quality refills from occurring. The camera
must authenticate the refill station, rather than vice versa The
secure protocol is communicated to the refill station during the
automated test procedure. Contact is made to four gold plated spots
on the ICP/print head TAB by the refill station as the new ink is
injected into the print head.
FIG. 16 illustrates rear view of the next step in the construction
process whilst FIG. 17 illustrates a front camera view.
Turning now to FIG. 16, the assembly of the camera system proceeds
via first assembling the ink supply mechanism 40. The flex PCB is
interconnected with batteries only one 84 of which is shown, which
are inserted in the middle portion of a print roll 85 which is wrapped
around a plastic former 86. An end cap 89 is provided at the other
end of the print roll 85 so as to fasten the print roll and batteries
firmly to the ink supply mechanism.
The solenoid coil is interconnected (not shown) to interconnects
97, 98 (FIG. 8) which include leaf spring ends for interconnection
with electrical contacts on the Flex PCB so as to provide for electrical
control of the solenoid.
Turning now to FIGS. 17-19 the next step in the construction process
is the insertion of the relevant gear chains into the side of the
camera chassis. FIG. 17 illustrates a front camera view, FIG. 18
illustrates a back side view and FIG. 19 also illustrates a back
side view. The first gear chain comprising gear wheels 22, 23 are
utilized for driving the guillotine blade with the gear wheel 23
engaging the gear wheel 65 of FIG. 8. The second gear chain comprising
gear wheels 24, 25 and 26 engage one end of the print roller 61
of FIG. 8. As best indicated in FIG. 18, the gear wheels mate with
corresponding buttons on the surface of the chassis with the gear
wheel 26 being snap fitted into corresponding mating hole 27.
Next, as illustrated in FIG. 20, the assembled platten unit is
then inserted between the print roll 85 and aluminum cutting blade
43.
Turning now to FIG. 21, by way of illumination, there is illustrated
the electrically interactive components of the camera system. As
noted previously, the components are based around a Flex PCB board
and include a TAB film 58 which interconnects the print head 102
with the image sensor and processing chip 51. Power is supplied
by two AA type batteries 83, 84 and a paper drive stepper motor
16 is provided in addition to a rotary guillotine motor 17.
An optical element 31 is provided for snapping into a top portion
of the chassis 12. The optical element 31 includes portions defining
an optical view finder 32, 33 which are slotted into mating portions
35, 36 in view finder channel 37. Also provided in the optical element
31 is a lensing system 38 for magnification of the prints left number
in addition to an optical pipe element 39 for piping light from
the LED 5 for external display.
Turning next to FIG. 22, the assembled unit 90 is then inserted
into a front outer case 91 which includes button 4 for activation
of printouts.
Turning now to FIG. 23, next, the unit 92 is provided with a snap-on
back cover 93 which includes a slot 6 and copy print button 7. A
wrapper label containing instructions and advertising (not shown)
is then wrapped around the outer surface of the camera system and
pinch clamped to the cover by means of clamp strip 96 which can
comprise a flexible plastic or rubber strip.
Subsequently, the preferred embodiment is ready for use as a one
time use camera system that provides for instant output images on
demand.
It will be evident that the preferred embodiment further provides
for a refillable camera system. A used camera can be collected and
its outer plastic cases removed and recycled. A new paper roll and
batteries can be added and the ink cartridge refilled. A series
of automatic test routines can then be carried out to ensure that
the printer is properly operational. Further, in order to ensure
only authorized refills are conducted so as to enhance quality,
routines in the on-chip program ROM can be executed such that the
camera authenticates the refilling station using a secure protocol.
Upon authentication, the camera can reset an internal paper count
and an external case can be fitted on the camera system with a new
outer label. Subsequent packing and shipping can then take place.
It will be further readily evident to those skilled in the art
that the program ROM can be modified so as to allow for a variety
of digital processing routines. In addition to the digitally enhanced
photographs optimized for mainstream consumer preferences, various
other models can readily be provided through mere re-programming
of the program ROM. For example, a sepia classic old fashion style
output can be provided through a remapping of the color mapping
function. A further alternative is to provide for black and white
outputs again through a suitable color remapping algorithm. Minimumless
color can also be provided to add a touch of color to black and
white prints to produce the effect that was traditionally used to
colorize black and white photos. Further, passport photo output
can be provided through suitable address remappings within the address
generators. Further, edge filters can be utilized as is known in
the field of image processing to produce sketched art styles. Further,
classic wedding borders and designs can be placed around an output
image in addition to the provision of relevant clip arts. For example,
a wedding style camera might be provided. Further, a panoramic mode
can be provided so as to output the well known panoramic format
of images. Further, a postcard style output can be provided through
the printing of postcards including postage on the back of a print
roll surface. Further, clip arts can be provided for special events
such as Halloween, Christmas etc. Further, kaleidoscopic effects
can be provided through address remappings and wild color effects
can be provided through remapping of the color lookup table. Many
other forms of special event cameras can be provided for example,
cameras dedicated to the Olympics, movie tie-ins, advertising and
other special events.
The operational mode of the camera can be programmed so that upon
the depressing of the take photo a first image is sampled by the
sensor array to determine irrelevant parameters. Next a second image
is again captured which is utilized for the output. The captured
image is then manipulated in accordance with any special requirements
before being initially output on the paper roll. The LED light is
then activated for a predetermined time during which the DRAM is
refreshed so as to retain the image. If the print copy button is
depressed during this predetermined time interval, a further copy
of the photo is output. After the predetermined time interval where
no use of the camera has occurred, the onboard CPU shuts down all
power to the camera system until such time as the take button is
again activated. In this way, substantial power savings can be realized.
Ink Jet Technologies
The embodiments of the invention use an ink jet printer type device.
Of course many different devices could be used. However presently
popular ink jet printing technologies are unlikely to be suitable.
The most significant problem with thermal ink jet is power consumption.
This is approximately 100 times that required for high speed, and
stems from the energy-inefficient means of drop ejection. This involves
the rapid boiling of water to produce a vapor bubble which expels
the ink. Water has a very high heat capacity, and must be superheated
in thermal ink jet applications. This leads to an efficiency of
around 0.02%, from electricity input to drop momentum (and increased
surface area) out.
The most significant problem with piezoelectric ink jet is size
and cost. Piezoelectric crystals have a very small deflection at
reasonable drive voltages, and therefore require a large area for
each nozzle. Also, each piezoelectric actuator must be connected
to its drive circuit on a separate substrate. This is not a significant
problem at the current limit of around 300 nozzles per printhead,
but is a major impediment to the fabrication of pagewidth printheads
with 19,200 nozzles.
Ideally, the ink jet technologies used meet the stringent requirements
of in-camera digital color printing and other high quality, high
speed, low cost printing applications. To meet the requirements
of digital photography, new ink jet technologies have been created.
The target features include:
low power (less than 10 Watts)
high resolution capability (1,600 dpi or more)
photographic quality output
low manufacturing cost
small size (pagewidth times minimum cross section)
high speed (<2 seconds per page).
All of these features can be met or exceeded by the ink jet systems
described below with differing levels of difficulty. Forty-five
different ink jet technologies have been developed by the Assignee
to give a wide range of choices for high volume manufacture. These
technologies form part of separate applications assigned to the
present Assignee as set out in the list under the heading Cross
References to Related Applications.
The ink jet designs shown here are suitable for a wide range of
digital printing systems, from battery powered one-time use digital
cameras, through to desktop and network printers, and through to
commercial printing systems
For ease of manufacture using standard process equipment, the printhead
is designed to be a monolithic 0.5 micron CMOS chip with MEMS post
processing. For color photographic applications, the printhead is
100 mm long, with a width which depends upon the ink jet type. The
smallest printhead designed is covered in U.S. patent application
Ser. No. 09/112,764, which is 0.35 mm wide, giving a chip area of
35 square mm. The printheads each contain 19,200 nozzles plus data
and control circuitry.
Ink is supplied to the back of the printhead by injection molded
plastic ink channels. The molding requires 50 micron features, which
can be created using a lithographically micromachined insert in
a standard injection molding tool. Ink flows through holes etched
through the wafer to the nozzle chambers fabricated on the front
surface of the wafer. The printhead is connected to the camera circuitry
by tape automated bonding.
Tables of Drop-on-Demand Ink Jets
The present invention is useful in the field of digital printing,
in particular, ink jet printing. A number of patent applications
in this field were filed simultaneously and incorporated by cross
reference.
Eleven important characteristics of the fundamental operation of
individual ink jet nozzles have been identified. These characteristics
are largely orthogonal, and so can be elucidated as an eleven dimensional
matrix. Most of the eleven axes of this matrix include entries developed
by the present assignee.
The following tables form the axes of an eleven dimensional table
of ink jet types.
Actuator mechanism (18 types)
Basic operation mode (7 types)
Auxiliary mechanism (8 types)
Actuator amplification or modification method (17 types)
Actuator motion (19 types)
Nozzle refill method (4 types)
Method of restricting back-flow through inlet (10 types)
Nozzle clearing method (9 types)
Nozzle plate construction (9 types)
Drop ejection direction (5 types)
Ink type (7 types)
The complete eleven dimensional table represented by these axes
contains 36.9 billion possible configurations of ink jet nozzle.
While not all of the possible combinations result in a viable ink
jet technology, many million configurations are viable. It is clearly
impractical to elucidate all of the possible configurations. Instead,
certain ink jet types have been investigated in detail. Forty-five
such inkjet types were filed simultaneously to the present application.
Other ink jet configurations can readily be derived from these
forty-five examples by substituting alternative configurations along
one or more of the 11 axes. Most of the forty-five examples can
be made into ink jet printheads with characteristics superior to
any currently available ink jet technology.
Where there are prior art examples known to the inventor, one or
more of these examples are listed in the examples column of the
tables below. The simultaneously filed patent applications by the
present applicant are listed by USSN numbers. In some cases, a print
technology may be listed more than once in a table, where it shares
characteristics with more than one entry.
Suitable applications for the ink jet technologies include: Home
printers, Office network printers, Short run digital printers, Commercial
print systems, Fabric printers, Pocket printers, Internet WWW printers,
Video printers, Medical imaging, Wide format printers, Notebook
PC printers, Fax machines, Industrial printing systems, Photocopiers,
Photographic minilabs etc.
The information associated with the aforementioned 11 dimensional
matrix are set out in the following tables.
ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS) Description
Advantages Disadvantages Examples Thermal An electrothermal Large
force High power Canon Bubblejet bubble heater heats the ink generated
Ink carrier limited 1979 Endo et al to above boiling Simple to water
GB patent point, transferring construction Low efficiency 2,007,162
significant heat to No moving High temperatures Xerox heater-in-
the aqueous ink. A parts required pit 1990 Hawkins bubble nucleates
Fast operation High mechanical et al U.S. Pat. No. and quickly forms,
Small chip area stress 4,899,181 expelling the ink. required for
Unusual materials Hewlett-Packard The efficiency of the actuator
required TIJ 1982 Vaught process is low, with Large drive et al
U.S. Pat. No. typically less than transistors 4,490,728 0.05% of
the Cavitation causes electrical energy actuator failure being transformed
Kogation reduces into kinetic energy bubble formation of the drop.
Large print heads are difficult to fabricate Piezo- A piezoelectric
Low power Very large area Kyser et al U.S. Pat. No. electric crystal
such as lead consumption required for 3,946,398 lanthanum zirconate
Many ink types actuator Zoltan U.S. Pat. No. (PZT) is electrically
can be used Difficult to 3,683,212 activated, and either Fast operation
integrate with 1973 Stemme expands, shears, or High efficiency electronics
U.S. Pat. No. 3,747,120 bends to apply High voltage drive Epson
Stylus pressure to the ink, transistors Tektronix ejecting drops.
required USSN 09/112,803 Full pagewidth print heads impractical
due to actuator size Requires electrical poling in high field strengths
during manufacture Electro- An electric field is Low power Low maximum
Seiko Epson, Usui strictive used to activate consumption strain
(approx. et all JP electrostriction in Many ink types 0.01%) 253401/96
relaxor materials can be used Large area USSN 09/112,803 such as
lead Low thermal required for lanthanum zirconate expansion actuator
due to titanate (PLZT) or Electric field low strain lead magnesium
strength Response speed is niobate (PMN). required marginal (.about.10
us) (approx. 3.5 High voltage drive V/.mu.m) can be transistors
generated required without Full pagewidth difficulty print heads
Does not impractical due to require actuator size electrical poling
Ferro- An electric field is Low power Difficult to USSN 09/112,803
electric used to induce a consumption integrate with phase transition
Many ink types electronics between the can be used Unusual materials
antiferroelectric Fast operation such as PLZSnT (AFE) and (<1
.mu.s) are required ferroelectric (FE) Relatively high Actuators
require phase. Perovskite longitudinal a large area materials such
as tin strain modified lead High efficiency lanthanum zirconate
Electric field titanate (PLZSnT) strength of exhibit large strains
around 3 V/.mu.m of up to 1% can be readily associated with the
provided AFE to FE phase transition. Electro- Conductive plates
Low power Difficult to USSN static are separated by a consumption
operate 09/112,787; plates compressible or Many ink types electrostatic
09/112,803 fluid dielectric can be used devices in an (usually air).
Upon Fast operation aqueous application of a environment voltage,
the plates The electrostatic attract each other actuator will and
displace ink, normally need to causing drop be separated from ejection.
The the ink conductive plates Very large area may be in a comb or
required to honeycomb achieve high structure, or stacked forces
to increase the High voltage drive surface area and transistors
may be therefore the force. required Full pagewidth print heads
are not competitive due to actuator size Electro- A strong electric
Low current High voltage 1989 Saito et al, static pull field is
applied to consumption required U.S. Pat. No. 4,799,068 on ink the
ink, whereupon Low May be damaged 1989 Miura et al, electrostatic
temperature by sparks due to U.S. Pat. No. 4,810,954 attraction
air breakdown Tone-jet accelerates the ink Required field towards
the print strength increases medium. as the drop size decreases
High voltage drive transistors required Electrostatic field attracts
dust Permanent An electromagnet Low power Complex USSN magnet directly
attracts a consumption fabrication 09/113,084; electro- permanent
magnet, Many ink types Permanent 09/112,779 magnetic displacing
ink and can be used magnetic material causing drop Fast operation
such as ejection. Rare earth High efficiency Neodymium Iron magnets
with a field Easy extension Boron (NdFeB) strength around 1 from
single required. Tesla can be used. nozzles to High local Examples
are: pagewidth print currents required Samarium Cobalt heads Copper
(SaCo) and metalization magnetic materials should be used for in
the neodymium long iron boron family electromigration (NdFeB, lifetime
and low NdDyFeBNb, resistivity NdDyFeB, etc) Pigmented inks are
usually infeasible Operating temperature limited to the Curie temperature
(around 540 K.) Soft A solenoid induced Low power Complex USSN magnetic
a magnetic field in a consumption fabrication 09/112,751; core soft
magnetic core Many ink types Materials not 09/113,097; electro-
or yoke fabricated can be used usually present in 09/113,066; magnetic
from a ferrous Fast operation a CMOS fab such 09/112,779; material
such as High efficiency as NiFe, CoNiFe, 09/113,061; electroplated
iron Easy extension or CoFe are 09/112,816; alloys such as from
single required 09/112,772; CoNiFe [1], CoFe, nozzles to High local
09/112,815 or NiFe alloys. pagewidth print currents required Typically,
the soft heads Copper magnetic material is metalization in two parts,
which should be used for are normally held long apart by a spring.
electromigration When the solenoid lifetime and low is actuated,
the two resistivity parts attract, Electroplating is displacing
the ink. required High saturation flux density is required (2.0-2.1
T is achievable with CoNiFe [1]) Lorenz The Lorenz force Low power
Force acts as a USSN force acting on a current consumption twisting
motion 09/113,099; carrying wire in a Many ink types Typically,
only a 09/113,077; magnetic field is can be used quarter of the
09/112,818; utilized. Fast operation solenoid length 09/112,819
This allows the High efficiency provides force in a magnetic field
to be Easy extension useful direction supplied externally from single
High local to the print head, for nozzles to currents required example
with rare pagewidth print Copper earth permanent heads metalization
magnets. should be used for Only the current long carrying wire
need electromigration be fabricated on the lifetime and low print-head,
resistivity simplifying Pigmented inks materials are usually requirements.
infeasible Magneto- The actuator uses Many ink types Force acts
as a Fischenbeck, U.S. Pat. striction the giant can be used twisting
motion No. 4,032,929 magnetostrictive Fast operation Unusual materials
USSN 09/113,121 effect of materials Easy extension such as Terfenol-
such as Terfenol-D from single D are required (an alloy of terbium,
nozzles to High local dysprosium and iron pagewidth print currents
required developed at the heads Copper Naval Ordnance High force
is metalization Laboratory, hence available should be used for Ter-Fe-NOL).
For long best efficiency, the electromigration actuator should be
lifetime and low pre-stressed to resistivity approx. 8 MPa. Pre-stressing
may be required Surface Ink under positive Low power Requires Silverbrook,
EP tension pressure is held in a consumption supplementary 0771
658 A2 and reduction nozzle by surface Simple force to effect related
patent tension. The surface construction drop separation applications
tension of the ink is No unusual Requires special reduced below
the materials ink surfactants bubble threshold, required in Speed
may be causing the ink to fabrication limited by egress from the
High efficiency surfactant nozzle. Easy extension properties from
single nozzles to pagewidth print heads Viscosity The ink viscosity
is Simple Requires Silverbrook, EP reduction locally reduced to
construction supplementary 0771 658 A2 and select which drops No
unusual force to effect related patent are to be ejected. A materials
drop separation applications viscosity reduction required in Requires
special can be achieved fabrication ink viscosity electrothermally
Easy extension properties with most inks, but from single High speed
is special inks can be nozzles to difficult to achieve engineered
for a pagewidth print Requires 100:1 viscosity heads oscillating
ink reduction. pressure A high temperature difference (typically
80 degrees) is required Acoustic An acoustic wave is Can operate
Complex drive 1993 Hadimioglu generated and without a nozzle circuitry
et al, EUP focussed upon the plate Complex 550,192 drop ejection
region. fabrication 1993 Elrod et al, Low efficiency EUP 572,220
Poor control of drop position Poor control of drop volume Thermo-
An actuator which Low power Efficient aqueous USSN elastic relies
upon consumption operation requires 09/112,802; bend differential
thermal Many ink types a thermal insulator 09/112,778; actuator
expansion upon can be used on the hot side 09/112,815; Joule heating
is Simple planar Corrosion 09/113,096; used. fabrication prevention
can be 09/113,068; Small chip area difficult 09/113,095; required
for Pigmented inks 09/112,808; each actuator may be infeasible,
09/112,809; Fast operation as pigment 09/112,780; High efficiency
particles may jam 09/113,083; CMOS the bend actuator 09/112,793;
compatible 09/112,794; voltages and 09/113,128; currents 09/113,127;
Standard 09/112,756; MEMS 09/112,755; processes can 09/112,754;
be used 09/112,811; Easy extension 09/112,812; from single 09/112,813;
nozzles to 09/112,814; pagewidth print 09/112,764; heads 09/112,765;
09/112,767; 09/112,768 High CTE A material with a High force can
Requires special USSN 09/112,778; thermo- very high coefficient
be generated material (e.g. 09/112,815; elastic of thermal Three
methods PTFE) 09/113,096; actuator expansion (CTE) of PTFE Requires
a PTFE 09/113,095; such as deposition are deposition 09/112,808;
polytetrafluoroethylene under process, which is 09/112,809; (PTFE)
is used. development: not yet standard in 09/112,780; As high CTE
chemical vapor ULSI fabs 09/113,083; materials are usually deposition
PTFE deposition 09/112,793; non-conductive, a (CVD), spin cannot
be 09/112,794; heater fabricated coating, and followed with 09/113,128;
from a conductive evaporation high temperature 09/113,127; material
is PTFE is a (above 350.degree. C.) 09/112,756; incorporated. A
50 candidate for processing 09/112,807; .mu.m long PTFE bend low
dielectric Pigmented inks 09/112,806; actuator with constant may
be infeasible, 09/112,820 polysilicon heater insulation in as pigment
and 15 mW power ULSI particles may jam input can provide Very low
power the bend actuator 180 .mu.N force and 10 consumption .mu.m
deflection. Many ink types Actuator motions can be used include:
Simple planar Bend fabrication Push Small chip area Buckle required
for Rotate each actuator Fast operation High efficiency CMOS compatible
voltages and currents Easy extension from single nozzles to pagewidth
print heads Conduct- A polymer with a High force can Requires special
USSN 09/113,083 ive high coefficient of be generated materials polymer
thermal expansion Very low power development thermo- (such as PTFE)
is consumption (High CTE elastic doped with Many ink types conductive
actuator conducting can be used polymer) substances to Simple planar
Requires a PTFE increase its fabrication deposition conductivity
to Small chip area process, which is about 3 orders of required
for not yet standard in magnitude below each actuator ULSI fabs
that of copper. The Fast operation PTFE deposition conducting polymer
High efficiency cannot be expands when CMOS followed with resistivity
heated. compatible high temperature Examples of voltages and (above
350.degree. C.) conducting dopants currents processing include:
Easy extension Evaporation and Carbon nanotubes from single CVD
deposition Metal fibers nozzles to techniques cannot Conductive
pagewidth print be used polymers such as heads Pigmented inks doped
may be infeasible, polythiophene as pigment Carbon granules particles
may jam the bend actuator Shape A shape memory High force is Fatigue
limits USSN 09/113,122 memory alloy such as TiNi available maximum
number alloy (also known as (stresses of of cycles Nitinol - Nickel
hundreds of Low strain (1%) is Titanium alloy MPa) required to extend
developed at the Large strain is fatigue resistance Naval Ordnance
available (more Cycle rate limited Laboratory) is than 3%) by heat
removal thermally switched High corrosion Requires unusual between
its weak resistance materials (TiNi) martensitic state and Simple
The latent heat of its high stiffness construction transformation
austenic state. The Easy extension must be provided shape of the
actuator from single High current in its martensitic nozzles to
operation state is deformed pagewidth print Requires pre- relative
to the heads stressing to distort austenic shape. The Low voltage
the martensitic shape change causes operation state ejection of
a drop. Linear Linear magnetic Linear Magnetic Requires unusual
USSN 09/113,061 Magnetic actuators include the actuators can be
semiconductor Actuator Linear Induction constructed with materials
such as Actuator (LIA), high thrust, long soft magnetic Linear Permanent
travel, and high alloys (e.g. Magnet efficiency using CoNiFe) Synchronous
planar Some varieties Actuator (LPMSA), semiconductor also require
Linear Reluctance fabrication permanent Synchronous techniques magnetic
Actuator (LRSA), Long actuator materials such as Linear Switched
travel is Neodymium iron Reluctance Actuator available boron (NdFeB)
(LSRA), and the Medium force is Requires complex Linear Stepper
available multi-phase drive Actuator (LSA). Low voltage circuitry
operation High current operation
BASIC OPERATION MODE Description Advantages Disadvantages Examples
Actuator This is the simplest Simple Drop repetition Thermal ink
jet directly mode of operation: operation rate is usually Piezoelectric
ink jet pushes ink the actuator directly No external limited to
around USSN 09/112,751; supplies sufficient fields required 10 kHz.
09/112,787; 09/112,802; kinetic energy to Satellite drops However,
this is 09/112,803; 09/113,097; expel the drop. The can be avoided
not fundamental 09/113,099; 09/113,084; drop must have a if drop
velocity to the method, 09/112,778; 09/113,077; sufficient velocity
to is less than 4 but is related to 09/113,061; 09/112,816; overcome
the m/s the refill method 09/112,819; 09/113,095; surface tension.
Can be efficient, normally used 09/112,809; 09/112,780; depending
upon All of the drop 09/113,083; 09/113,121; the actuator kinetic
energy 09/113,122; 09/112,793; used must be provided 09/112,794;
09/113,128; by the actuator 09/113,127; 09/112,756; Satellite drops
09/112,755; 09/112,754; usually form if 09/112,811; 09/112,812;
drop velocity is 09/112,813; 09/112,814; greater than 4.5 09/112,764;
09/112,765; m/s 09/112,767; 09/112,768; 09/112,807; 09/112,806;
09/112,820 Proximity The drops to be Very simple Requires close
Silverbrook, EP 0771 printed are selected print head proximity 658
A2 and related by some manner fabrication can between the print
patent applications (e.g. thermally be used head and the induced
surface The drop print media or tension reduction of selection means
transfer roller pressurized ink). does not need to May require two
Selected drops are provide the print heads separated from the energy
required printing alternate ink in the nozzle by to separate the
rows of the contact with the drop from the image print medium or
a nozzle Monolithic color transfer roller. print heads are difficult
Electro- The drops to be Very simple Requires very Silverbrook,
EP 0771 static pull printed are selected print head high electrostatic
658 A2 and related on ink by some manner fabrication can field patent
applications (e.g. thermally be used Electrostatic field Tone-Jet
induced surface The drop for small nozzle tension reduction of selection
means sizes is above air pressurized ink). does not need to breakdown
Selected drops are provide the Electrostatic field separated from
the energy required may attract dust ink in the nozzle by to separate
the a strong electric drop from the field. nozzle Magnetic The drops
to be Very simple Requires Silverbrook, EP 0771 pull on ink printed
are selected print head magnetic ink 658 A2 and related by some
manner fabrication can Ink colors other patent applications (e.g.
thermally be used than black are induced surface The drop difficult
tension reduction of selection means Requires very pressurized ink).
does not need to high magnetic Selected drops are provide the fields
separated from the energy required ink in the nozzle by to separate
the a strong magnetic drop from the field acting on the nozzle magnetic
ink. Shutter The actuator moves High speed Moving parts are USSN
09/112,818; a shutter to block (>50 kHz) required 09/112,815;
09/112,808 ink flow to the operation can be Requires ink nozzle.
The ink achieved due to pressure pressure is pulsed at reduced refill
modulator a multiple of the time Friction and wear drop ejection
Drop timing can must be frequency. be very accurate considered The
actuator Stiction is energy can be possible very low Shuttered The
actuator moves Actuators with Moving parts are USSN 09/113,066;
grill a shutter to block small travel can required 09/112,772; 09/113,096;
ink flow through a be used Requires ink 09/113,068 grill to the
nozzle. Actuators with pressure The shutter small force can modulator
movement need be used Friction and wear only be equal to the High
speed must be width of the grill (>50 kHz) considered holes.
operation can be Stiction is achieved possible Pulsed A pulsed magnetic
Extremely low Requires an USSN 09/112,779 magnetic field attracts
an `ink energy external pulsed pull on ink pusher` at the drop operation
is magnetic field pusher ejection frequency. possible Requires special
An actuator controls No heat materials for both a catch, which dissipation
the actuator and prevents the ink problems the ink pusher pusher
from moving Complex when a drop is not construction to be ejected.
AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) Description Advantages
Disadvantages Examples None The actuator directly Simplicity of
Drop ejection Most ink jets, including fires the ink drop, construction
energy must be piezoelectric and thermal and there is no Simplicity
of supplied by bubble. external field or operation individual nozzle
USSN 09/112,751; other mechanism Small physical actuator 09/112,787;
09/112,802; required. size 09/112,803; 09/113,097; 09/113,084; 09/113,078;
09/113,077; 09/113,061; 09/112,816; 09/113,095; 09/112,809; 09/112,780;
09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128;
09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812;
09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768;
09/112,807; 09/112,806; 09/112,820 Oscillating The ink pressure
Oscillating ink Requires external Silverbrook, EP 0771 ink oscillates,
providing pressure can ink pressure 658 A2 and related pressure
much of the drop provide a refill oscillator patent applications
(including ejection energy. The pulse, allowing Ink pressure USSN
09/113,066; acoustic actuator selects higher operating phase and
09/112,818; 09/112,772; stimulation) which drops are to speed amplitude
must 09/112,815; 09/113,096; be fired by The actuators be carefully
09/113,068; 09/112,808 selectively blocking may operate controlled
or enabling nozzles. with much Acoustic The ink pressure lower energy
reflections in the oscillation may be Acoustic lenses ink chamber
achieved by can be used to must be designed vibrating the print
focus the sound for head, or preferably on the nozzles by an actuator
in the ink supply. Media The print head is Low power Precision Silverbrook,
EP 0771 proximity placed in close High accuracy assembly 658 A2
and related proximity to the Simple print required patent applications
print medium. head Paper fibers may Selected drops construction
cause problems protrude from the Cannot print on print head further
rough substrates than unselected drops, and contact the print medium.
The drop soaks into the medium fast enough to cause drop separation.
Transfer Drops are printed to High accuracy Bulky Silverbrook, EP
0771 roller a transfer roller Wide range of Expensive 658 A2 and
related instead of straight to print substrates Complex patent applications
the print medium. A can be used construction Tektronix hot melt
transfer roller can Ink can be dried piezoelectric ink jet also
be used for on the transfer Any of USSN proximity drop roller 09/112,751;
09/112,787; separation. 09/112,802; 09/112,803; 09/113,097; 09,113,099;
09/113,084; 09/113,066; 09/112,778; 09/112,779; 09/113,077; 09/113,061;
09/112,818; 09/112,816; 09/112,772; 09/112,819; 09/112,815; 09/113,096;
09/113,068; 09/113,095; 09/112,808; 09/112,809; 09/112,780; 09/113,083;
09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128; 09/113,127;
09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813;
09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807;
09/112,806; 09/112,820; 09/112,821 Electro- An electric field is
Low power Field strength Silverbrook, EP 0771 static used to accelerate
Simple print required for 658 A2 and related selected drops head
separation of patent applications towards the print construction
small drops is Tone-Jet medium. near or above air breakdown Direct
A magnetic field is Low power Requires Silverbrook, EP 0771 magnetic
used to accelerate Simple print magnetic ink 658 A2 and related
field selected drops of head Requires strong patent applications
magnetic ink construction magnetic field towards the print medium.
Cross The print head is Does not Requires external USSN 09/113,099;
magnetic placed in a constant require magnet 09/112,819 field magnetic
field. The magnetic Current densities Lorenz force in a materials
to be may be high, current carrying integrated in the resulting
in wire is used to move print head electromigration the actuator.
manufacturing problems process Pulsed A pulsed magnetic Very low
power Complex print USSN 09/112,779 magnetic field is used to operation
is head construction field cyclically attract a possible Magnetic
paddle, which Small print head materials pushes on the ink. A size
required in print small actuator head moves a catch, which selectively
prevents the paddle from moving.
ACTUATOR AMPLIFICATION OR MODIFICATION METHOD Description Advantages
Disadvantages Examples None No actuator Operational Many actuator
Thermal Bubble Ink jet mechanical simplicity mechanisms USSN 09/112,751;
amplification is have 09/112,787; 09/113,099; used. The actuator
insufficient 09/113,084; 09/112,819; directly drives the travel,
or 09/113,121; 09/113,122 drop ejection insufficient process. force,
to efficiently drive the drop ejection process Differential An actuator
material Provides greater High stresses Piezoelectric expansion
expands more on travel in a are involved USSN 09/112,802; bend one
side than on the reduced print Care must be 09/112,778; 09/112,815;
actuator other. The head area taken that the 09/113,096; 09/113,068;
expansion may be materials do not 09/113,095; 09/112,808; thermal,
delaminate 09/112,809; 09/112,780; piezoelectric, Residual bend
09/113,083; 09/112,793; magnetostrictive, or resulting from 09/113,128;
09/113,127; other mechanism. high 09/112,756; 09/112,755; The bend
actuator temperature or 09/112,754; 09/112,811; converts a high
high stress 09/112,812; 09/112,813; force low travel during 09/112,814;
09/112,764; actuator mechanism formation 09/112,765; 09/112,767;
to high travel, tower 09/112,768; 09/112,807; force mechanism. 09/112,806;
09/112,820 Transient A trilayer bend Very good High stresses USSN
09/112,767; bend actuator where the temperature are involved 09/112,768
actuator two outside layers stability Care must be are identical.
This High speed, as a taken that the cancels bend due to new drop
can be materials do not ambient temperature fired before heat delaminate
and residual stress. dissipates The actuator only Cancels residual
responds to transient stress of heating of one side formation or
the other. Reverse The actuator loads a Better coupling Fabrication
USSN 09/113,097; spring spring. When the to the ink complexity 09/113,077
actuator is turned High stress in off, the spring the spring releases.
This can reverse the force/distance curve of the actuator to make
it compatible with the force/time requirements of the drop ejection.
Actuator A series of thin Increased travel Increased Some piezoelectric
ink stack actuators are Reduced drive fabrication jets stacked.
This can be voltage complexity USSN 09/112,803 appropriate where
Increased actuators require possibility of high electric field short
circuits strength, such as due to pinholes electrostatic and piezoelectric
actuators. Multiple Multiple smaller Increases the Actuator forces
USSN 09/113,061; actuators actuators are used force available may
not add 09/112,818; 09/113,096; simultaneously to from an actuator
linearly, 09/113,095; 09/112,809; move the ink. Each Multiple reducing
09/112,794; 09/112,807; actuator need actuators can be efficiency
09/112,806 provide only a positioned to portion of the force control
ink flow required. accurately Linear A linear spring is Matches
low Requires print USSN 09/112,772 Spring used to transform a travel
actuator head area for motion with small with higher the spring
travel and high force travel into a longer travel, requirements
lower force motion. Non-contact method of motion transformation
Coiled A bend actuator is Increases travel Generally USSN 09/112,815;
actuator coiled to provide Reduces chip restricted to 09/112,808;
09/112,811; greater travel in a area planar 09/112,812 reduced chip
area. Planar implementation implementation s due to extreme s are
relatively fabrication easy to difficulty in fabricate. other orientations.
Flexure A bend actuator has Simple means Care must be USSN 09/112,779;
bend a small region near of increasing taken not to 09/113,068;
09/112,754 actuator the fixture point, travel of a bend exceed the
which flexes much actuator elastic limit in more readily than the
flexure area the remainder of the Stress actuator. The distribution
is actuator flexing is very uneven effectively Difficult to converted
from an accurately even coiling to an model with angular bend, finite
element resulting in greater analysis travel of the actuator tip
Catch The actuator Very low Complex USSN 09/112,779 controls a small
actuator energy construction catch. The catch Very small Requires
either enables or actuator size external force disables movement
Unsuitable for of an ink pusher that pigmented inks is controlled
in a bulk manner. Gears Gears can be used to Low force, low Moving
parts USSN 09/112,818 increase travel at the travel actuators are
required expense of duration. can be used Several actuator Circular
gears, rack Can be cycles are and pinion, ratchets, fabricated using
required and other gearing standard surface More complex methods
can be MEMS drive electronics used. processes Complex construction
Friction, friction, and wear are possible Buckle A buckle plate
can Very fast Must stay S. Rirata et al, "An Ink-jet plate
be used to change a movement within elastic Head Using Diaphragm
slow actuator into a achievable limits of the Microactuator",
Proc. fast motion. It can materials for IEEE MEMS, Feb. 1996, also
convert a high long device life pp 418-423. force, low travel High
stresses USSN 09/113,096; actuator into a high involved 09/112,793
travel, medium force Generally high motion. power requirement Tapered
A tapered magnetic Linearizes the Complex USSN 09/112,816 magnetic
pole can increase magnetic construction pole travel at the expense
force/distance of force. curve Lever A lever and fulcrum Matches
low High stress USSN 09/112,755; is used to transform travel actuator
around the 09/112,813; 09/112,814 a motion with small with higher
fulcrum travel and high force travel into a motion with requirements
longer travel and Fulcrum area lower force. The has no linear lever
can also movement, and reverse the direction can be used for of
travel. a fluid seal Rotary The actuator is High Complex USSN 09/112,794
impeller connected to a mechanical construction rotary impeller.
A advantage Unsuitable for small angular The ratio of pigmented
inks deflection of the force to travel actuator results in a of
the actuator rotation of the can be matched impeller vanes, to the
nozzle which push the ink requirements by against stationary varying
the vanes and out of the number of nozzle. impeller vanes Acoustic
A refractive or No moving Large area 1993 Hadimioglu et al, lens
diffractive (e.g. zone parts required EUP 550,192 plate) acoustic
lens Only relevant 1993 Elrod et al, EUP is used to for acoustic
ink 572,220 concentrate sound jets waves. Sharp A sharp point is
Simple Difficult to Tone-jet conductive used to concentrate construction
fabricate using point an electrostatic field. standard VLSI processes
for a surface ejecting ink-jet Only relevant for electrostatic ink
jets
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