Note: Descriptions are shown in the official language in which they were submitted.
WO 95/~6323 PCTIUS94113803
2 1 907~ ~
lNSTANT SPECL~T. FI~FECTS E FcTRoNIc G
BA(~KGROU~JI ) OF TETF. INVFNTION
The present invention relates generally to a hand-held electronic
5 imaging camera and, more particularly, to an electronic camera capable of
recording an image of a scene and thereafter PlP~t--~r:-~lly ~ g the
image and producing a hard copy print on a paper sheet. The electronic
camera is designed to be operated by a child, and captures the image with a
charge coupled device (CCD). The hard copy printout is ~r~lably produced
l0 with a thermal printer.
Electronic imaging cameras capable of recording an image of a scene
and providing a hard copy printout using a thermal printer are known in the
art. For example, U.S. Patent No. 4,074,324 to Barrett discloses an instant
electronic camera which focuses an image on a CCD having a planar array of
15 pholvs~llsvlD. Signals from the CCD are digitized and placed in a shift
register memory. The contents of the shift register memory are then output to
a dot matrix printer having heat-sensitive paper. Other electronic cameras
with printer devices are shown, for example, in U.S. Patent No. 4 ~62,301 to
F.rlirhm~n, published European Patent Application No. 574,581 to King Jim
20 Co., published PCT Application No. WO 92/11731 to Eastman Kodak Co.,
and published European Application No. 398,295 to Minolta Camera.
In a typical electronic camera of this type, the camera optical system
focuses an image on a conventional CCD chip having an array of
phr,l..c~ The pl ~us~l~DulD produce analog signals proportional to the
25 intensity of incident light. These analog signals are digitized by an analog-to-
digital converter and stored in a random access memory. The capture,
conversion and storage of the image is normally controlled by a
mi~lV~lV-~DDVl. The mi~:.vlulv~Dsvl can then control the print head of an
~Ccc~ri:ltpd printer ""; ~ - to provide a hard copy of the captured image.
30 Optional software for the mi-.vl,.u~ssu- can process the image stored in the
random access memory to enhance the quality of the printed image or to
produce special effects such as an outline image.
Electronic cameras of this type have several disadvantages. Because
the CCD array operates at a relatively high speed, and the printer typically
35 operates at a relatively low speed, it is often necessary to store the entire captured image in the random access memory. A typical conventional CCD
array can capture 80,000 or more picture elements (pixels), each of which is
WO 95116323 PCTIUS94/13803
21 9078l
stored in memory. This requires a relatively large memory which adds to the
cost of the camera. The system described in PCT Application No. WO
92/11731 attempts to overcome this liDadval~ldge by coupling the CCD array
directly to a printer. However, this system introduces additional
S disadvantages and limits the available options.
For many appli~-Ati~ nc, it is not necessary to capture 80,000 or more
pixels to produce a D~ r ~ image quality. For example, for a child's
electronic camera, a CCD device with a 160 x 160 array of ph~usellsulD
(25,600 pixels) or a 190 x 160 array of pho~ (30,400 pixels) may
10 provide sufficient picture resolution. Using a lower resolution CCD array can save costs for both the CCD chip and the random access memory.
To produce a c~ticf~rtory printed image quality, it is necessary to
produce the appearance of shades of gray in the hard copy print out.
However, a thermal printer is only capable of ~..ud.~ black or white dots.
15 As a result, the llli~lV~lU~t~DDUI must manipulate the data in the random
access memory to produce the à~ea.an.~ of shades of gray in the printout.
rithmc for producing this effect, known as dithering techniques, are
known in the art. A typical dithering technique would operate on a block of
pixels one line wide and two or three lines high. Thus, to create the first line20 of the printed image, the microprocessor needs to operate on only the first
two or three lines of the captured image. Therefore, if a system could be
arranged so that only two or three lines of data had to be stored in the
random access memory at a given time, the size of the random access
memory could be reduced by a factor of ten or more, with a consequent
25 savings in cost.
Because the CCD array produces analog outputs at a relatively high
rate, it is usually necessary for both the digital-to-analog converter and the
random access memory to operate at high speed. Cost would be reduced if
the CCD array could be arranged to capture an image at high speed, but
30 output the image at relatively low speed, therefore allowing a slower analog
to-digital converter and random access memory to be used.
It is a primary objective of the present invention to overcome the
described disadvantages of the prior art as well as other prior shul ~lUl~S,
and to provide a relatively low cost electronic camera for children which is
35 capable of providing plain prints as well as prints with special effects
features.
wo gs/16323 Pcrluss41l3803
2 1 9078 1
BR~F SUMMARY OF Al~F INVE~TlON
The present invention provides a low cost irlstant special effects
camera suitable for use by children, and provides an ~ - alternative to
film cameras. In the preferred ~."~ , an image sensor includes an
5 array Of F~(: which provide analog irnage outputs proportional to
the intensity of light incident on the respective ~)1~. .l- ., . ~,. ., ~ The irnage
sensor preferably includes timing logic for rnn~o11ing operation of the
.1"~ P. ~-- array, as well as an analog to digital converter for digitizing theanalog image outputs and interface logic. Electronic exposure control may
10 . also be provided to allow the use of low cost fiAved aperture camera optics.
A memory stores the digitized image data from the image sensor for
later processing by a microcontroller. To allow the use of a low pin count,
low cost .1li.l~....1...11~Ar, the microcontroller accesses dah in the memory
through the image sensor interface and a m111ti~A1AY_rl address/data bus. In
15 operation, the microcontroller retrieves data from the memory and applies
contrast rnl~,~... ~....~..1, mA~nifirAtlnn, dithering and data compression
A1gnrithmA to prepare the data for printing. The print-formatted data is then
stored back in the memory.
The mirrornntroller applies selected special effects to the print-
20 formatteddataasitisretrievedfrommemoryforprinting. Tl.~..,...~1i...lforaplurality of standard special effects, including processing A1~nri~hmc and/or
data, may be provided in ROM internal to the microcontroller. Additional
special effects infnrm~tinn may be provided by optional ROM packs which
may be inserted in the camera. A manual switch may be provided on the
25 camera housing to permit a user to select speciflc special effects.
A~ itinnA11y, random selection of the special effects infnrmAhnn may be
chosen.
An integral printer is provided in the camera body, and paper may be
supplied by rerl ~r~Ahl,A paper cassettes. Audible and/or visual inriirAtinnc
30 maybe provided to alert the user to the status of the camera processing.
WO 95/16323 PCT/US94113803
21 90781
BRTFF D~ R~PTION OF T~TF DRAWING~
The objectc, advantages and features of the present invention will
become apparent to the skilled artisan from the following detailed
,~.~c. ~ , when read in light of the a ~ Iyillg drawings, in which:
Fig. 1 is a schematic block diagram of a typica~ prior art electronic
camera with a hard copy output;
Fig. 2 is a block diagram of a ~llv~lLiul~al CCD imaging array;
Fig. 3 is a block diagram of a custom CCD imaging array for use in an
electro~ic camera;
Fig. 4 is a block diagram of one ~ . . .ho. 1; . . ~ ~ ~ . 1 of an improved electronic
imaging camera using a custom CCD array;
Fig. 5 is a block diagrarn of a preferred custom imaging sensor;
Fig. 6 is a block diagram of a preferred ~mhQtlimf~nt of an electronic
imaging camera using the imaging sensor of Fig. 5;
Fig. 7 is a flow chart illllctrAtin~ the operation of the electronic imaging
camera of Fig. 6;
Fig. 8 illustrates a pulse width m~ llAtit~n techrlique for controlling
printing operation;
Fig. 9 is a flow chart illllctrAtin~ an exposure control scheme for use
with the electronic imaging camera of Fig. 6;
Fig. 10 is a front view of a camera housing for the electronic imaging
camera of Fig. 6;
Fig. 11 is a rear view of the camera houcing of Fig. 9;
Fig. 12 is a side view of the camera housing of Fig. 9; and
Fig. 13 is a bottom view of the camera housing of Fig. 9.
DET~TT ~n D~:s~l~lr~ ~ OF THE l~ :1 ) E~RODIMF~TS
Referring to Fig. 1, a typical electronic camera utilizes a conventional
CCD array 1 to capture an image focused on the CCD array by camera opticc.
The analog output of the CCD array 1 is digitized by an A/D converter 2 and
stored in random access memory 3. A mi..u~.v.~aa~i 4 controls a print head
5 and printer ~ 6 to provide a hard copy of the captured image. The
mi..v~.vu:~v. 4 may optionally include software to process the image stored
in the random access memory 3 to enhance the quality of the hard copy image
35 or to produce special effects such as an out~ine image.
wo 95116323 2 1 9 ~ 7 ~3 1 PCIIUS94113803
As illl1ctr~q~tpcl in Fig. 2, a ~ullv~ Lul~al CCD array indudes a plurality
of pho~ust~ 7 arranged in a matrix of rows and columns. Each
ph. .l- ,s.~ ~.b a single pixel in the image. A vertical shift register 8
is qcco~qtpci with eadh column of ~ c ~ During QpPrqti~)n, the analog
5 image data from the ph.. l.. ~ cc.,~ 7 is gated into the vertical shift registers 8
by the CCD control 10. At this point, eadh vertical shift register contains one
column of analog image; r~ S -l ~Pq~ ~ lly, the CCD control 10 shifts
the data in the vertical shift registers 8, by one pixel in an upward direction.As a result, the topmost pixel of each column is shifted into the hnri7-)ntAi
shift register 9 so that the h- ri7r~nt-ql shift register 9 then contains one row of
image data. The contents of the hnri7cntql shift register are then shifted to
the right by one pixel at a time to the analog output terminal 11 by the CCD
control 10. in this way, a row of image dah is dodced out of the CCD array
one pixel at a time. The h--ri7- ntql shift register 9 is then filled with the next
line of data by shifting the dah in all the vertical shift registers 8 up one pixel.
This line of pixel dah is again output through the analog output terminal 11
by successive shifting of the hnri7~1nt~1 shift register 9. This process is
repeated until all lines of pixel dah have been output from the analog output
terminal 11.
l~eferring now to Fig. 3, the custom CCD array consists of a
conventional CCD array 12 having, for example, a 160 x 160 pixel matrix, an
analog to digital (A/D) converter 13, a tri-state buffer 14, control logic 15 and
memory control logic 16. The busy signal 22, the transfer signal 21, the read
signal 20 and the shutter signal 19 are used to control the operation of the
device and are normally connected to an external l~ lU~llu~:)sol. The digital
data signals 23, the address signals 17 and read/write signals 18 are used to
transfer dah to an external random access memory.
Ln operation, when the shutter signal 19 is asserted, the control logic 15
controls the CCD array 12 to capture a single image focused on the array by
the camera optics. A filter may be provided to select light frequencies to
whidh the p h. ~I- .c~ are sensitive. During this process, the control logic 15
asserts the busy signal 22 to inform the external mi~lu~ that it is busy.
When the image has been captured, the busy signal 22 is not asserted. When
the transfer signal 21 is asserted, the control logic 15 transfers a
prP~iPtPrminPci number of lines of data from the CCD array 12 via the A/D
converter 13 and tri-state buffer 14 to an external random access memory.
The control logic 15 also controls the address in the external random access
WO 95/16323 PCTIUS94/13803
21 9~781
memory at which each pixel is stored by r(~ntrollin~ the memory control logic
16 which generates the address signals 17 and the read/write signal 18 which
are also connected to the external random access memory. The control logic
15 asserts the busy signal 22 during the transfer. This process may be
S repeated until all the data from the CCD array 12 has been lla~r~ d.
Between each transfer of a pre~ P~ number of lines, or once all
the data has been LLal~r~ d to the external random access memory, the data
in the external random access memory can be read by asserting the read
signal 20. When the read signal 20 is asserted, the control logic 15 and the
memory control logic 16 control the address signals 17 and the read/write
signal 18 to access a memory location in the external random access memory.
While the read signal 20 is asserted, the tri-state buffer 14 is disabled to
prevent the output of the A/D converter 13 from intPrf7rin~ with the data
read from the external random access memory. The address from which data
is read is ~lPlr~ ;llPd by the ;--~ rlll signal 24 and clear signal 25. When
the clear signal 25 is asserted, tne address is set to zero. Each time the
Pnl signal 24 is asserted the address is incremented by one. In this
way, an external mi~.~.U~Pssc~ or other control circuit can access any of the
data in the external random access memory.
Turning to Fig. 4, an improved electronic imaging camera includes a
custom CCD array 26, such as that illllctr.7te~ in Fig. 3, external random
access memory 27, a mi..v~iùcPssubl 28, a print head 29, a printer drive
mPrh~nicm 30 and an optional plug-in module 31 which may comprise
random access memory only, or a ~ of random access memory and
25 read-only memory.
In operation, the Il~lu~lu~P~SVL 28 romm,7n~lC the custom CCD array
26 to capture an image when the shutter switch is operated. Once the image
has been captured the custom CCD array 26 irlforms the mi~vp~v~ssbl 28
that this operation is complete. When no plug-in module 31 provided, the
30 mi..v~.b.~:ssv- 28 then comm7n~lC the custom CCD array 26 to transfer a
l~lr~ r~ P~i number of lines of image dah into the random access memory
27. The number of lines to transfer is ~frlr ...i~.Pd by the functions the
electronic imaging camera is expected to be able to perform without the
benefit of the plug-in module 31. The amount of random access memory 27 is
35 chosen to be just sufficient to hold the ~Ir~ r~ P~I number of image data
lines. In one rl~Lbbvilll~lll, eight lines of data are Llal~r~ d tû the random
access memory 27. Where one line of image data consists of 160 pixels, the 8
WO 95116323 2 1 9 0 7 ~ 1 PCrlUS94113803
lines of image dah requires 8 times 160 bytes, or 1,280 bytes. A low cost 2
kilobyte random access memory 27 can therefore be used. TrAn~fPrrin~ the
image 8 lines at a time allows a simple dithering algorithm to be employed
which will allow an a~ h~' ^ but not high quality gray-scale hard copy to be
5 produced. As each group of 8 lines of image data is llai~r .l~d, the
uU.lv~lv-~ssur 28 in ~Ou~elaLiOl- with custom CCD array 26 accesses the
image dah one byte at a time, carries out the dithering Al~rithm, if required,
then controls the print head 29 and the printer drive mPrh~nicm 30 to
produce a hard copy image. Lines are llai~r~ d eight at a time to random
10 access memory 27, manipulated and printed by the mi.lu~lu.~ssul 28, in
rr~OrPrAtir~n with the print head 29 and printer drive ~--P- 1.~,-;.~.--- 30 until the
entire captured image has been printed.
In another Pmho~limPnt, 4 kilobytes of random access memory 27 is
provided and lines of image data are llal~sr~ d in a block of 16 lines or two
15 blocks of 8 lines to the random access memory 27. This allows the
mi~lU~lU~sul 28 to employ a more sophicti~AtPd dithering algorithm which
produces a ull~ulldillgly higher quality hard copy image.
To allow Afltliti~n~l features and runctions to be provided a plug-in
module 31 may be ~ P l~ to the electronic imaging camera. In one
20 PmhorlimPnt, the plug-in module 31 contains 32 kilobytes of random access
memory. This allows the entire image to be lla~ d rrom the custom CCD
array 26 to the plug-in module 31 before the image is printed. This allows
more rr~mrlirAtP~ effects to be produced which require the mi.lu~luu:~ul to
be able to access the entire image or large portions of the image. In addition,
25 because the entire image is stored, extra copies of the image can be printed.Each copy can be identical to the previous one or modified, if required by
pressing one of the effects switches 32. The effects that can be selected
include, but are not limited to, binary image, outline image, contrast
Pnh~nrPmPnt and the addition of a "speech bubble" such as are used in
30 newspaper cartoons.
In another PmhQ~limPnt, the plug-in module contains read only
memory, the contents of which represent a number of pre-stored images.
These pre-stored images could include picture frames, places of interest, film
or pop stars, animals or other images of an Prl~lrAtirnAl or l~ dil~lllt~ll~
35 nature. A particular image can be selected either by the operation of a switch
incorporated in the plug-in module 31 or by the effects switches 32. The
WO 95/16323 = PCT/US94113803
21 90787
image could be printed directly or used as a badcground over which a
caphlred image could he ~ se~1
Turning now to Fig. 5, a blodc diagram of the preferred custom image
sensor is ~ lchrAt~rl Preferably, the image sensor array is conshructed in
A.. 1_, .. - with PCT Published Application No. WO 91/04633 to VL~I Vision
Ltd. ("VVL"). A test circuit for such an image sensor array is disdosed in
PCT Published Application No. 91/04498. This type of imaging array is
available from VVL as part of a ~ P mnnnlithir camera under the
hrade name ASIS-1070. ~ _lin~ of the array is available to suit a
lO particular application.
Briefly, unlilce the CCD array of Fig. 2, the VVL image sensor array
does not utilize vertical shift registers to dock the data to an ouhput port.
Rather, a relatively compact array of pixels is provided with a series of
hnri7nntAl word lines and vertical bit lines. Each pixel in a row is connected
15 to a common hrlri7~nntAI word line which, in turn, is rnnnrctrd to driver
conhrol circuih^y sudh as a shift register. Each vertical column of pixels is
connected to a vertical bit line whidh is coupled to one input of an Accc)ri~tPcl
switch sense amplifier. A second input of the switch sense Amrlifif~rc is
coupled to a switdling conhrol circuit. The ouhput terminals of the switch
20 sense amplifiers are connected to a common read-out line. In operation, the
signals from the phnl..~..c...~. are ~r~ v~ly sequentially mlllhrlrY~d onto
the read out line through the switdh sense ~ ;ri~ ~ under direction of the
driver conhrol circuihry and the switdung control circuit. For a more detailed
desiption of sudh an image sensor array and its operation, reference may be
25 had to the published VVL patent applications.
Fig. 5 illustrates a modified version of the VVL ASIS 1070 whidh forms
an image sensor 100. The sensor 100 indudes an image array similar to the
ASIS-1070 image array, together with all the timing logic to conhrol the array.
In addition to the imaging array, the sensor 100 includes an analog to digital
30 converter and all the logic necessary to interface with static RA~ and a
~ u~lu~u~ uller. The design of the image sensor array is intended to allow the
use of a low pin count, low cost ~ u~u~ uller to process the image data and
con~hrol the printer. The sensor array interface supports a minimum pin count
interface between a system microconhroller and the system pPrirh~rAIc by
35 combining the address and dah bus and decoding the high and low address
locally to the p~rirhPrAlC The image is stored in static RAM and is accessed
WO 95/16323 PCl)llS94)138D3
21 ~07~1
using a mlllhrlPYPcl address/data bus to provide an interface with the
mi. ~v~
An array 101 of ~' having an array size, for example, of 160
X 190 pixels, is provided with aCco~iatp~l control circuits and switch sense
5 ~mrlifiPrc In operation, row shift register 103 and column shift register 105
sequentially switch the data from the individual pixels through a bank of
iQ~ amplifiers 107 to an output terminal 109. An eight bit analog to
digihl converter 111 digitizes the pixel data into eight bit data, and places the
data in parallel on a data bus Do-D7 &ough a bi-directional dah latch 112 A
10 fifteen bit presettable binary counter 113 is provided to generate address
signals for the individual dah words on address bus Ao-A7, Ag-AI4. A RAM
interface is provided for write enable (WE) and address strobe (AS) signals
which conhrol transfers between the image sensor array and the system
memory. The interface between the image sensor array and the RAM is a
15 simple read/write interface using the address strobe line tv latch the current
address and the write enable line to conhrol the read or write mode. Since the
speed of the ..u.~ llPr interface will be relatively slow in ~ ;c. "~ to
the rate at which data becomes available on the multiplexed address/data
bus during a read operation, this simple interface permits the use of a low
20 cost RAM.
A mode controller 117 is included to allow the image sensor array to
operate in a selected one of several available operating modes, as discussed
more fully below. Automatic exposure conhrol logic and timer conhrol circuit
121 are provided to control the sensor exposure time and to ~ lLv~
25 system operation. The use of electronic exposure control circuit 119, which
operates over a relatively wide range, permits the camera to use a low cost
fixed aperhlre lens.
Turning now to Fig. 6, the image sensor array is arranged in a system
including a shtic RAM 125, a microconhroller 127, and a power supply unit
30 129. The microcontroller 127 can be, for example, a commercially available
Zilog Z86C76 microconhroller. The system also includes a plurality of
switches 131 for controlling the shutter as well as the special effects and tvnesettings. An optional effects cartridge 133 in the form of an insertable
memory package may also be provided. An eight dot print head 135 is
35 provided for printing hard copies of images on thermal paper. Alternatively,
an inkjet or other appropriate type of printer may be used. Movement of the
print head and paper transport are conhrolled by a DC motor encoder 137. An
WO 95/16323 PCTrUS94/l3803
i 2190781
audio/video output device 139 allows a user to monitor system operation
through audible tones and/or a visible display such as an LCD screen or
indicator lights. ~ 1;t;nn~11Y~ a low cost electronic Yiew finder could be
provided which may be driven from either the microcontroller or the
S memory. The system may be powered by a battery 141, which may take the
forrn, for example, of 6 AA cells (1.5V nominal) or 6 NiCad l~.l~g~al~lc cells
~1.2V nominal).
In operation, the raw irnage is stored in the static RAM 125 by the
image sensor array 100. The image may then be accessed using a mll1tirl~yed
10 8 bit address/data bus to provide the interface of the RAM 125 to the
microcontroller 127Yia the image sensor array 100. This interface allows the
system to use a low pin count, low cost miocontroller such as the Zilog
Z86C76. The microcontroller 127 processes the raw image data and converts
it from the original 8 bit gray scale 190 x 160 resolution to a 2 bit gray scale380 x 320 resolution image suitable for printing. The converted image is
stored in the static RAM 125, and may be retrieved and combined with
overlays and effects stored either internally within the microcontroller or
externally in an optional effects cartridge 133. The effects cartridge 133 is
~It!r~l~ly accessed using the same multiplexed address/data bus used for
20 t~lmmllni~Atilmc with the image sensor array 100 and the static RAM 125.
The uu~ w~ ller interface with the print SUb~Y~ includes a
buffered 8 bit interface to the print head 135, and the DC motor control,
optical encoder feedback and home sensor feedback 137. The thermal print
head 135 is preferably a passive print head including eight dots each of
25 d~p~u~u-l-al~ly 35 ohms. The print head is controlled using an eight bit datalatch to connect print data to the print head and to provide sufficient drive
capability to place an NPN transistor into SAhlrAh~m to thereby hurn on the
individual print dots. The single transistor drive provides a benefit by
reducing voltage requirements, in relation to Darlington pair l,,.,.cl~.., " to
30 ensure mAYimllm voltage across the print head. The print head interface
writes to the latch by writing the required pattern to the address/data bus
and driving the clock line of the latch high. If individual bits of the print head
are required to be turned off earlier than others, then the latch can be
rewritten with a new value at any time. At the ~mrl~tinn of the print shrobe
35 time, all bits will be written to zero.
The DC motor interface is linked to the encoder feedback to provide
speed conhrol of the DC motor using a pulse width modulated (PWM)
_ _ _ _ _ _ . = , . = ., , = .... = . . ... .... . ...
W0 9S/16323 2 1 9 0 7 8 ~ PCIIUS94)138~3
.
11
system. During the printing cycle, the ~ .v.u.,l.uller will cûntrûl the speed
of the print head by reference to rohry encoder pulses fed back from an IR
LuLlau~isLui which senses the position of the print head. These pulses are
used to pulse width modulate the DC motor to mainhin a constant speed at
S the print head, and to ~yll~hlui~ the print head strobe with the print head
pûsition to ensure good print regictrAtinn In addition to the encûder
feedback, a home position sensor will provide a feedback to allow a
r~ at the shrt of each print line.
The DC motor will be turned on at the mAYimllm pulse width
(controlled by an internal timer interrupt) until the time between the encoder
pulses is within a set range. If the time between encoder pulses becomes too
short, then the motor will be slowed by; .~. rr~i 1 Ig the amount of OFF time inthe pulse code m-~d~llAti~-n Conversely, if the time is too long, then the motorspeed will be increased by iu~ si.~g the ON time of the m~ ti~n signals.
The encoder feedback may be used to ~y~lu~>~u~e the print strobe to the
motor position, with an absolute line to line regictrAti~-n being provided by
the home sensor input.
The effects cartridge 133 interfaces with the microcontroller 127
thrûugh the same multiplexed address/data bus lines through which the
image sensor array 100 and the Uli~lv~uilLluller 127 interface. A separate
effects cartridge enable line is provided to enable the cartridge interface. This
allows the system to l;~L;,~ between accesses to the RAM 125 through
image sensor 100 and accesses to the effects cartridge ROM pack. Internally,
the effects cartridge 133 lul~C~.ably includes two eight bit latches for addressdata and plurality of ROM memory locations. To access a particular byte
stored within the ROM pack, the u~ r writes the low address byte
on the ~ 1 address/dah bus, followed by the high address byte, and
will then read back the data. If ~ -uLiv~ bytes are required, then the
minimum operation will be to rewrite the low address bytes and read back
the data. In the preferred embodiment, the high and low address bytes allow
up to a 16 bit a~l~r~ccin~ range within the cartridge. Thus, the cartridge may
store up to 64 kilobytes of dah for use by the microcontroller.
The microcontroller 127 interfaces with the user through a series of
switches 131, including the shutter button, a repeat picture button, and the
effects cartridge selector input. The shutter button is rnnn~t~d to bo~h the
power supply and the microcontroller so that when the system is powered
down, pressing the shutter button will power the system and hke a picture.
Wo 9~116323 , PCI/IJS94/13803
21 90781
12
If the system is already turned on, pressing the shutter will simply take
another picture. The repeat picture button will operate only if pressed within
a certain time period after the last picture was taken, for example, 2 minutes.
Pressing the repeat picture button within that time period causes the system
S to reprint the picture with the current effects setting. The effects selection will
consist of three binary coded inpuS selected by a rotary selector. (See Figs. 10and 12).
During operation, the system will produce an audible sound generated
from a sound effects device. Pl~r~ ~ably, the sound may be produced with a
10 simple single transistor amplifier with a moving coil loudspeaker
. l.ul,uulàled in the audio/visual output device 139. It may also be possible
to utilize different sound effects to indicate different points in the camera
cycle. For example, one sound effect may be used to indicate the picture has
been taken or that the camera is taking a picture, and a second sound effect
15 may be used while the camera is IJlU.~lg the image and printing it out. As
an alternative to the sound effects, or in addition to the sound effects, visualindicators such as LED lights or an LCD display may be used to indicate the
camera operation.
The microcontroller interface allows control of the image sensor 100
20 and the static RAM 125 using a number of operation modes. These modes
include image control modes and memory control modes. As noted above,
the image sensor 100 mode is rCmtr~llPd by the micrornntrn11Pr through
instructions to the address/mode decode logic 117. The imager control
modes allow the interface to instruct the image sensor 100 to capture a frame
25 of image data and place the frame in static RAM 125, and to set the exposure
value in exposure control 119 following IJlu~S~lg of the picture.
The memory control modes allow the ul~Lu~ul~lLuller 127 to access the
external RAM 125 via the image sensor using the mllltirlPYP-I address/dah
bus. In the simplest form, the read and write mode operates by the
30 uli~-u~u~ uller writing the low address byte followed by the high address
byte, and reading back data or write data. The ~rlitinn~l memory control
modes increase the system efficiency by avoiding the microcontroller
rewriting the address bytes. For instance, an RMW mode allows the
microcontroller to perform a normal read operation followed by a write
35 operation to the same address. Auto read or write cycles allow the
uli~u~u-~l-uller 127 to read or write Cu~ u~iv~ bytes of the RAM 125 while
the binary counter 113 of image sensor 100 a1ltnmati~ally increments the
WO 95/16323 ~3 PCTIUS94113803
address. Thus, blocks of data may be read or written with only the first
address being set. Such an arr2~PmPnt is nearly as efficient as directly
accessing the memory 125.
The basic software functions of the electronic camera are illustrated in
5 flow chart form in Fig. 7. Prior to operating the camera, a user should set the
three position tone control switch to the desired setting. In normal indoor
use, the tone control should be set to medium. For operation in cold
rnn~iti~mc such as outdoor winter use, the tone control should be set to dark;
and in very hot weather, the light tone control setting should be used. As
10 shown in Fig. 7, camera operation may be initiated by pressing the shutter
button to power up the camera. The overall principle of the system is to
capture the image as quickly as possible, apply all the standard PnhAnrPmPntc
and ~u~ sio~ to the image, and store the print-formatted image back in
the RAM 125 while printing an appropriate picture heading. Finally, the
15 image is rotated as it is removed from the static RAM 125 and printed with
the d~ u~-;aL~ overlays, scaling, etc. being applied at that time. Finally, a
picture footer such as a company logo may be printed. One benefit of the
system is an ability to maintain the printable image in RAM 125 such that if
another copy of the image is provided within the time-out period, the copies
20 can be produced with alL~..,dLiv~ effects. A time-out period of a~lu~llal :ly two minutes may be used to help conserve battery life.
Once the shutter button is pressed, an electronic exposure control is
performed. The exposure control adjusts the pixel exposure time to
~Ulllp~l~dl~ for reflected light from the main subject of the exposure, and
25 allows the camera to use a low cost fixed aperture lens. The function of the
electronic exposure control is discussed more fully in ~ ..";, ... l ;.... with Fig. 9.
The objective of the image ~lu.~s~i lg software is to convert the 8 bit
gray scale 160 X 190 image captured by the image sensor 100 into a 2 bit gray
scale image at 320 X 380 resolution, with a~litinnAI image PnhAnrPmPnt to
30 tailor the image for the print Su~y~L~lll. The image processing consists of
several main stages: contrast Pn~ of the original data to increase the
printed image contrast; mA~nifirAtirn of the original image to 320 X 380
resolution for the printer; dithering and thresholding of the mA~nifiP~i image
to reduce each pixel from 8 bit gray scale resolution to 2 bit gray scale
35 resolution; and compression of the image to 4 pixels per byte to allow the
image to be stored within the same 30,400 byte image areas as the original 8
bit image.
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Since the hardware interface with the external RAM 125 is optimized
to allow access to u~se~uliv~ bytes of stored data, the image processing
software preferably utilizes as much internal ~ u~ Pr RAM as is
available to load pieces of the image, prooess them, and store them back into
S the external RAM 125. Assurning, for example, that 160 bytes of internal
RAM are available in the mirro~-ntroller 127, a block of 40 bytes of original
image data may be retrieved from the external RAM 125 for processing.
Following m~nifit~ti~m, the 40 byte block of image data fills an 80 byte by 2
row block of data, for a total of 160 bytes. After dithering, thresholding and0 data compression, each 40 bytes of original data becomes two rows of
l data of 20 bytes each
Contrast ~nh~n~Pm~nt is applied to the original 40 bytes of image data
as they are copied from the external RAM 125 to the uu-~ ller internal
RAM. The contrast Pnh-". . P~I modifies the raw image data by applying a
15 ~ .;. .P 1 conversion function to map the raw image data into enhanced
contrast data. M~gnifi~tinn increases the image size by UllV~:lLillg each pixelof i ~ lrl ,, . . .~ ., . into four pixels. In other words, the image data for a single
pixel in the 160 x 190 original image is assigned to 2 x 2 array of pixels in the
320 x 380 resolution array. The dither algorithm reduces the 8 bit, 256 gray
20 level original image data to 2 bit, 4 gray level data. Preferably, the ditheralgorithm is based on a Floyd Steinberg Dither algorithm which produces a
black and white output. To achieve the reduction in gray scale values, the 8
bit gray scale values X of the image data are compared against the thr~ch~ lc
shown in the following table, and the 2 bit gray scale value is set accordingly
Original 8 Bit Resulting 2 Bit
Gray Scale Value Gray Scale Value
0<X<42 o
42<X<127
127<X<212 2
212<X<255 3
The resulting 2 bit data is packed into four pixels per byte and stored
in the external static RAM 125. To avoid discrepancies in the dither
~lr~ tion of image data in adjacent blocks of image data, the image data
30 bytes at the right of each prooessed block are ~illl~;. Pd in 8 bit format and
WO 95/16323 PC'r)US941~3803
21 90781
are stored separately for use with the adjacent blocks when they are
~ub~ u~ ly processed.
The printer control software drives a single DC motor to scan the print
head and advance the paper. '`~ . .. l .. ~. .; ~l with the print head position, the
5 printer control software controls the dah on the print head and the strobe
time for the print head. The printer control software runs in parallel with the
image ~lU.~UIg software so that a header may be printed during image
~lU~ ;llg. Thus, the printer software is pl~:r~l~bly operated under interrupt
control.
The DC motor control is ~ l~ly a pulse width mn~ lAt~d (PWM)
type control system with the feedback p~rfnrmF~d using a single rotary
encoder system. The PWM output is produced with an internal timer set over
a range of values ~1Pp~nrlPnt on the speed error. The speed error is calculated
by the time taken between each encûder pulse. The basic printer control
15 system is shown srhPmAti~Ally in Fig. 8.
Print head control is p~rfnrm~d by ~yll~luviu~ulg the absolute print
head position, using the rotary encoder, with the print data. As the print
head moves, the encoder is used to ~y-l~hlvlu ~ the data being sent to the
print head such that every line printed is registered to the previous line. To
20 maintain the registration, the home sensor input is used to provide an
absolute print head position feedback at the start of each line.
The print head ON time is controlled using a series of gray scale tables
and an offset provided by the tone control position. The start of the ON time
forallprintdotsis~y,.~l...."; _.1totheencoderfeedback. Thedurationofthe
25 ON time for each pixel of the current line is chosen with reference to the
required gray level for the pixel and 50% weighting for the gray level of the
previous pixel. This ON time is offset with a fixed value ~l~tPrmin~ by the
tone control switch position to ... .~ s~l~ for ambient ~ c
As noted previously, special effects are applied to the print-formatted
30 image stored in external RAM 125 as the image is retrieved for printing. A
number of special effects are stored in microcontroller ROM and are available
with the standard camera. For example, typical effects might include a
"dollar bill" overlay to permit a user to print a friend's face on play money;
an aquarium overlay; a speech bubble overlay; and a picture frame overlay.
35 Additional effects may be provided by a ROM module in the optional plug-in
effects cartridge 133. For example, image scaling factors may be included in a
special effect to produce a "fun house mirror" image. To determine the
WO 95/16323 PCTIUS94/13803
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presence of the plug-im effects cartridge 133, a two byte signature is included
in the cartridge to be read back at power up. If a cartridge is present, the
cartridge effects will be used. Otherwise, the system will default to internal
effects.
Each effect will include or e or more of the following parts: overlays
which are ~U~ DD~d using run length ~_Ulll~ DDiUl~, contrast modifiers to
modify the contrast Al~nrithm; exposure modifiers to change the average
exposure value for long exposure type effects; x-axis image scaling hctors for
an entire image to produce a stretched or ~:Ulll~l~DD~d image; x,y ~uuldil~l~
image offsets to allow the entire picture to be offset within an overlay; line
scaling factors to be applied line by line; and line offsets for each image line to
be used with the line scaling factors. Other possible features which could be
provided through the effects cartridge include: a self timer to allow a user to
take a self portrait or the like; electronic zoom which expands the center of the
captured image to fill the entire picture area; a mirror effect provided by
printing only half of the captured image and then repeating this image in
reverse; and fading by a complex overlay so that the edge of the picture fades
to white. It should be noted that contrast and exposure modifiers will affect
the original image and thus will not be adjustable when using the repeat
picture functions.
The effect to be applied, if any, is preferably selected by the user
through a rotary switch on the camera housing. The position of the rotary
switch sets three binary coded inputs which are read by the mi.lu.ul.lluller
127. Such a rotary switch is shown in Figs. 10 and 12. Preferably, a random
setting may also be provided whereby the microcontroller randomly selects
one of the available special effects for printing.
Turrling now to Fig. 9, the exposure control is performed as soon as the
shutter button is pressed. The electronic exposure control algorithm performs
a first pass using a random line within the captured image. This allows the
software to calculate an d~,ulu~dllldl~ exposure value without waiting for the
entire frame to be captured. This exposure value can then be written directly
into the exposure register in exposure control 119 of the image sensor 100 and
another frame started. If the random line of the new frame is.within the
required exposure range, the center of the frame will be used to calculate a
more accurate exposure value. Tf necessary, another frame will be requested
to improve the image. When the exposure is within tolerance, the captured
image will be further processed and printed.
WO 95116323 PCrll~S94J13803
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The exposure r~lr~ hr~n may be pr-rfnrm.od by r~lrlll~tin~ an average
8 bit gray scale level of all the pixels in the area under consideration. The
- e%posure register contents will be modified from the error between the
calculated average gray scale level and the midpoint 8 bit value 128. As a first- S apprr~Yim~htm~ the exposure register contents will be set to a center value on
power up, and will be modified up or down from that value for a more
accurate exposure at the particular light level.
For improved results, the exposure setting may be center weighted
within the picture frame such that the exposure will be r~ t~ with
respect to the object at the center of the frame. This technique provides
several advantages. First, it helps ensure that the exposure is correct for the
main subject of the image. Also, c~lr~ tir\n of the exposure ~alue will only
require a limited nurnber of pixels to be con~ Prr-d and therefore will be
much hster. ~rl~litirn~lly, the effect of back-lighting/front-lighting will be
~ d as only the main subject of the picture will be considered by the
~rithm
The housing for the carnera is illll~hrAt~d in Figures 10-13. Referring to
the frontal view of Fig. 9, the housing includes a top molding 200 and a
bottom molding 202 which may be formed of an ~.o~lidl~ plastic material.
A knurled lens ring/effects switch 204 is provided for selecting a special
effect from the optional special effects ROM pack 206 or, if no special effects
pack is included, from the standard special effects stores in the ROM of the
system microconhroller. Rotation of the lens ring 204 sets three binary coded
inputs to be decoded by the microcontroller 127. Preferably, a visual
in~ hon such as a pointer arrow is provided on the lens ring to indicate the
current effects setting.
The upper molding 200 ~ la~ly includes a clear plastic cover 208 for
the printer paper ouhput. The upper molding 200 and the lower molding 202
are each provided with pPrirhr-r~l gripping portions. A shutter button 210 is
arranged on a gripping portion of the upper molding. ~ ih(~n~lly, a picture
repeat buhton (not shown) may be provided on the upper molding 200. The
top portion of the upper molding 200 receives a view finder molding 212,
which provides viewing aperhures 214 and 216. The viewing aperhures 214
and 216 are preferably covered with clear eye piece moldings 214A and 216A,
respectively.
A rear view of the camera housing is illushrated in Fig. 11. The ~iew
finder molding 212 includes a pair of eye pieces 214B and 216B associated
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with viewing apertures 214 and 216, ~ e-~iY~ly. A connector 218 is
provided for attaching a carrying strap (not shown). The rear portion of the
special effects ROM pack 206 includes a recessed gripping portion 206A to
facilitate removal from the camera body.
S Referring to the side view of Fig. 12, the lower molding 202 includes a
paper cassette cover 220. Thermal printing paper may be provided in a
rPpl~ PAhlP cassette which is received in an aperture of the system printer
mPrhAnicm A typical paper cassette would include sufficient paper to
supply approximately 50 hard copy prints. As shown in the bottom view of
Fig. 13, the lower molding 202 includes a battery cover 222 in addition to the
paper cassette cover.
The principles, preferred Pmho~imPntC and modes of operation of the
present invention have been described in the foregoing spP~ifi~Ati--n The
invention which is sought to be protected herein, however, is not to be
lS considered as limited to the particular forms disclosed, since these are to be
regarded as illustrative rather than restrictive. Variations and changes may
be made by those skilled in the art without departing from the spirit of the
invention.
