Note: Descriptions are shown in the official language in which they were submitted.
~WO95/16973 2l 62673 PCT~US94/13323
PORTABLE DATA FILE READERS
SPECIFICATION
AUTHOR~ATION PURSUANT TO 37 CFR 1.71 (d) and (e)
A portion of the disclosure of this patent document contains material which
is subject to copyright protection. The copyright owner has no objection to the
facsimile reproduction by anypne of the patent document or the patent discl^sl Irel
as it appears in the Patent and Tr~derllall~ Office patent file or records, but
otherwise reserves all cop),i~hl rights vrh~.t~oever.
CROSS Rt~tKtNCE TO RELATED APPLICATIONS
The present application is a continuation-in-part of application of Mailing
Label TB 632 907 748 US filed October 31,1994 which in turn was a continuation-
in-part application of USSN 08/298,345 filed 29 August 1994, which in turn was
a continuation-in-part of USSN of 08/241,866 filed 11 May 1994, which in turn was
a continuation-in-part of USSN of 08/170,120 filed on 17 December 1993, which
in turn was a continuation-in-part of USSN 08/067,384 filed on 25 May 1993 whichin turn was a continuation-in-part of USSN 08/060,404 filed on 11 May 1993. The
foregoing applications are hereby incorporated herein by reference.
TECHNICAL FIELD
This invention relates generally to bar code readers, and more particularly
to an improved portable device for reading portable data files and the like.
BACKGROUND ART
W0 95/16973 ~ PCT/US94/13323
Existing two--Ji",ensional portable bar code readers employ a mechanically
scanned laser beam. In one type of such reader, the beam is mechanically
scanned h ori~nlally as in conventional, one dimensional bar code scanners, while
it is also manually scanned vertically with a downward motion of the hand or wrist.
In a more sophisticated type of two-dimensional reader, the laser beam is
~,,ecl,cl,ically scanned in both the hori orllal and vertical directions utilizing a
raster.
These laser readers require that the scanning beam pattern be accurately
aligned with the label symbology, with the degree of accuracy being a function of
the vertical height of the coding elements versus the hori~onlal width. Further,reading the two dimensional codes line by line requires stitching separately read
lines or words after they are read. Some two dimensional codes (portable data
files and the like) do not provide for sli(cl,il,g. Afurther lillliLalion of laser scanners
for two-dimellsiollal reading is that they require a siy"ir,callL amount of time for the
label to be read, which of course requires that the scanner remain accurate!y
aligned with the label throughout the reading process.
nlS~! OSURE OF THE INVENTION
The present invention utilizes either: (1) a pair of two-dimensional
photosensitive arrays (such as charge coupled device arrays), a pair of pointingbeams for producing a pair of elongated bright spots on a target, an optical string,
control electronics, and a power supply; or (2) a single two-dimensional
photosensitive array (such as a charge coupled device array), a pair of pointingbeams for producing a pair of elongated bright spots on a target, an optical string,
control ele~:t,ul,. sl and a power supply. Both disclosed embodiments utilize the
arrays to pick up label images, convert the image to elec~l ical signals, and process
the signals with a ~"ic, ulJrocessor. In an exemplary embodiment of a two sensorembodiment, each sensor has its own lens system, which provides the proper
amount of overlap between the two images produced by the separate optical
strings. In both embodil "enls a focus indicalor may be provided to facilitate a user
in placing labels to be read at the correct distance from the reader.
BRIEF DESG.~I., ICN OF THE DRAWINGS
~JO95/16973 21 6 2 6 7 3 i~ PCT/US94/13323
FIG.1 depicts a conventional pair of sensors, each with its own lens, and
shows the image overlap provided with the lenses at various positions;
FIG. 2 depicts the sensor and lens system of the invention and its
corresponding image overlaps;
FIG.3is an enlarged view of the positioning of the left lens of FIG. 2;
FIG. 4 is a block diagram of the present invention;
FIG.5is a positioning device of the present invention;
FIG.6is an alternative first embodiment of an aiming device;
FIG. 7 is a diagrammatic illustration of the components of a second
embodiment wherein a single two-dimensional photosensitive array is utilized;
FIG.8is a graphical representation of beam signal outputs from a reader
according to the second embodiment described herein;
FIG S. 9A through 9H together comprise an electronic schematic of an
exemplary single sensor embodiment of the present invention;
lS FIG.10is a flow diagram illustrating an exemplary program structure for
operating the embodiment of FIG. 9A through 9H;
FIG.11is a side elevational view of an exemplary embodiment of a single
sensor portable data fiie reader module adapted for use with a hand-held data
terminal such as illustrated in FIGS.13 and 14;
FIG. 12 is an elevation view of a second exer,lpl~"/ embodiment of a single
sensor portable data file reader module adapted for use with a hand-held data
terminal such as illustrated in FIGS. 13 and 14A-14B;
FIG. 13 is a perspective view of a hand-held data terminal illusl~aling an
exemplar,v module embodiment of the present invention residing in a pod for
2~ attachment to a hand-held data terminal;
FIG. 14A is a top perspective view of a second hand-held data terminal
containing an exemplary module embodiment of the present invention; and
FIG. 14B is a bdtom perspective view of the terminal of FIG. 14A.
BEST MODE FOR CARRYING OUT THE INVENTION
The following United States Patent A~ lic~lions are incorporated herein in
their entirety by reference: (1) USSN 08/298,345 filed on 29 August 1994; (2)
USSN 08/1701120 filed on 17 December 1993; (3) USSN 08/067,384 filed on 25
WO 95/16973 ~ ~ ~ 2 J~ 7 ~l ~ r ~ PCT/US94/13323
May 1993; (4) USSN 08/060,404 filed on 11 May 1993; and (5) USSN 07/947,673
filed 21 September 1992.
A. First Exemplary Embo~5ir"~.,l
One difficulty with current two-dimensional array technology is limited
resolution. Commercially available sensors have been developed for television
related applications having ho,i,o~,~al resolutions typically limited to 500 to 750
pixels. However, a resolution of from 1000 to 2000 pixels is desirable for providing
readability of labels of different sizes and densities.
It is possible to split an image optically and use two sensors with slightly
overlapping fields of view. Such an optical system can be based, for example, ona single lens and 50% reflective mirror image splitting optics. This approach,
however, suffers from significant losses of optical energy, and also requires
complicated optomechanical designs for providing the necess~ry accuracy and
stability.
FIG. 1 depicts such a system based on two lenses, one for each sensor.
This system, however, prorluces the desi, dble amount of overlap between the left
and right images only when the target label is positioned at a fixed distance from,
the sensors. Turning now to FIG. 1, a label positioned in the vicinity designated
by b would be in the correct position so that the half images would overlap
properly, but the position a would produce a missing central area, while the
position c provides too great an area of ove, lappi"g, thereby defeali,)y the purpose
of using two sensors.
FIG. 2 also depicts the configuration of an exemplary first embodiment of
the present invention. Again, two sensors are used, each with its own lens.
These sensors are fixed in a common plane. Automatic focusing is provided by
placing the lenses on a carriage that moves toward and away from the sensors.
These lenses are mounted on the carriage in such a way that, as the carriage
moves away from the sensors, the distance between lenses decreases. As the
carriage moves toward the sensors, the distance between the lenses increases.
As seen in FIG. 2, the lines k-k' and m-m' represent the trajectories of the left and
right lenses co" ~:SpGI n.l;n9 to the carriage posiLion moving from c to a. The zones
A, B, and C correspondingly show the amount of image overlap between the left
~WO 95/16973 2 1 6 2 6 7 i f`~ PCT/US94/13323
and right halves of the total field of view of the system. As may be seen, this
overlap is the same percentage area for each zone. Therefore, the high total
resolution achieved by using two sensors is preserved throughout the entire
focusing range of the system.
s FIG. 3 illusl,ales, in greater detail, the position of the left lens during
focusing. The individual lens viewing angle must be larger than would be required
for ordinary imaging of the same field since the axis of the sensor's sight
(originating in the center of the sensor) skews away from the optical axis of the
lens when the carriage is in other than the midpoint position.
The block diagram of FIG. 4 depicts the major components of a portable
data file reader. Before a two-dime~ ,siollal CCD device or the like may be utilized
as an image sensor for reading two-dimensional optical information sets, two
problems must be overcome: first, the difficulty inherent in processing the dataproduced by a two-dimensional array, and second, the difficulty inherent in
mir,i" ,i~i"g mer"ory space req-,i, emenls when working with the array's data output.
The present invention solves these problems in part via utilization of the
CCD sensor storage capability. Both vertical and hori~o,)lal CCD shift registersare, in essence, analog storage devices used as an intermediate Read Once
Men,oly (ROM), situ~ted between the array of the photo receptors (photodiodes)
and the image p,ucessing hardware. The system architecture, r~pr~senled in FIG.
4 allows the microcor,l~oller 8 (referred to as a DSP) to have direct control over the
sensor 1 scanning processes via HVC pulse control circuit 7. This HVC circuit
generates the clock pulses necess~ry for moving electrical charges from the
photodiodes to the vertical shift registers, for moving charges in the vertical
r~g;~ler~, for sl ,ini"9 them inside the h o~ i~onLal shift r~ er and for controlling the
correlated double sampling device (CDS) 2. The vertical driver 4 serves as a
power stage for the vertical clock pulses. The microurocessor 8 oriyindles the
control signals to the HVC chip 7. These signals, where a CCD type device is
u tili~ed, cause the CCD to perform an image charge 1~ dl l~rer, a line by line vertical
shift and a pixel by pixel horizontal shift.
W095/16973 2 1 6 2 6 7 3 . PCT/US94/13323 ~
The analog signal appearing on the output of the CDS chip 2 is available
to the inputs of the AJD converter 3 and the comparator 5. The other input of the
comparator is connected with the output of the D/A device 6. The D/A is equippedwith an internal input latch. This architecture provides:
(1 ) line shifting separately from pixel scanning;
(2) shifting pixels along the hol i~onlal register either by processing the
pixel data or dumping it;
(3) input the pixel illuminance values to the DSP as gray scale values
produced by the high resolution A/D converter 3;
(4) input the pixel illuminance values as black/white single bit values
produced by the data reduction comparator 5.
So as to obtain a cleco~ l~hle image some image COI, ~cli~/e actions are also
provided, e.g., exposure adjustment, focusing adjustment (long range readers).
An exemplary solution is to take a service image or service frame, measure
` certain parar"eters of the image such as image quality (contrast, brightness,
sl ,a".i ,ess, and the like) adjust the sensor control parameters and take a second
improved image frame.
Since i"rur",dlion about image quality is redundant,.it is not necessary to
study the entire image. This is where the direct control of the vertical shift
becomes useful. Since the luminosity distribution along the image area may not
be uniform, it maybe necess~ry to study the whole image frame area, but with thelimited sampling frequency. Since the non-uniformity of the distribution of the
signal bright and dark levels is usually a smooth function of x and y sensor
coordinates, samples of this function may be taken infrequently, for example as
a matrix of 10 samples evenly spread along horizontal lines by 10 samples
vertically, i.e., 10û sa",p'~s. Based on these salll~les, the corrections for the next
frame may be accomplished.
When the "service frame" is of acceptable quality, the before mentioned
samples are used to c~lcl ~ te the threshold function for the next frame image data
compression. The threshold function is a 3-D surface that is stretched in the
coordinate of x and y sensor pixels and having vertical coordinate as the image
21 62673 = ~
~WO 95/16973 PCT/US94/13323
brightness or illuminance. If properly calculated, this surface must intersect the
image 3-D function on the middle level between the dark and bright levels of a
po, la~'e data file image. Having only about 100 points, represenlil lg the threshold
surface, small memory slor~ge is required. When the "info-frame" (service frame)S is taken for image processing, the DSP outputs the threshold points to the D/A
converter at the appropriate moments during the frame scanning. These points
are locked in the D/A's latch until they are updated with the following values by the
DSP. The cor,lpa,~lor 5 cor"pd,~s each pixel value with the threshold surface and
produces a high conl,dsl black/white image. This co",~ ssed image data is read
by the DSP either through polling or the interrupt, which occurs at each transition
from black to white and from white to black.
The "info-frame" (service frame) processing is combined with image
acquisition. Since the regions of the label image carry enough information for
decoding data residing in those regions, it is not necessary to have a complete
image from a pre-stored memory prior to starting the decoding process. To save
memory, only a limited number of lines are acquired, digitized and stored in theDSP RAM. Practically, about 40 lines may be stored in the processing image
buffer. After a current strip of an image has been decoded, the strip of the next
40 lines is acquired from the sensor and is placed in the same buffer abutted to
the preceding strip. Only a few lines from the preceding strip is required, to assure
continuity. The number of this overlap depends on the structure of the label code
and the desired skew angle tolerance. Thus, the processing image buffer is a
circular buffer, with some 40 plus lines of the ~liuiti~ed image. A minimum memory
capacily for this kind of buffer is: 50 lines x 750 pixels per line = 37500 bits or 2344
words.
Thus, the ~rore",enlioned description denotes how economizing of both
processing time and computing facilities is accGI"plished.
FIG. 5 depicts a reader positioning apparatus. S1 and S2 each produce
illuminating beams, which converge at a position from the reader where a two-
dimensional bar code is focused. In this embodiment the illulliillaLillg spot isrectangular, and outlines the viewing area.
2 1 6 2 6 7 3 "t ~
WO 95/16973 - = PCT/US94/13323
An alternative first embodiment of a reader aiming device is depicted in
FIG 6. In this embodiment, S1 and S2 produce narrow beams of light which
converge to indicate the center of the viewing area and the optimum focus
distance.
B. Second Exemplary Embo.li,~,e.,l
FIGS. 7 and 8 depict a second exemplary embodiment for a two-
dimel ,sional portable optically readable information reader. Turning first to FIG.
7 wherein it may be seen that two pointing beams are provided (S1 and S2) for
producing elongated bright spots (a and b) on a target surface Q. When this
lo surface lies in a plan at a readable distance from the reader, both spots (a and b)
merge. Conversely, where the target surface lies in a plane which is not at a
readable lisldl ,ce~ from the reader, the spots (a and b) are sepa, dled by a distance
m, which is a function of the displacement of the target surface from the best focus
position.
i5 The beams may have a wavel~. Iyll, selected from the visible portion of the
electromagnetic spectrum (such as those produce from red or green LED's), or
i~ dl dred sources may be u tili~e~ In either case the elongated profile of the beams
f~cilit~tes capturing of the spots by the array during the taking of a service frame
(FIG. 8), which is processed much faster than an ordinary dafa frame. This
reduction in processing time is accomplished by simply skipping most of the
horizontal lines in the frame and studying only about three percent (3%) of the
regularly spaced lines. Elongated or fan shaped spots (a and b) are preferred
since round or narrow spots may be missed if the spot's image fell between the
active horizontal lines of a service frame.
The disla"ce m is then measured by the reader's computer and is displayed
on the indicator (e.g., as a line of variable length, or as a sound of variable pitch)
such that an operalor may quickly adjust the disla~ ~ce between the reader and the
target even where the label to be read and the spots (S1 and S2) are not visible.
If the distance m between the spot images is defined as:
m=b-a
~W095/16973 21 6 2 6 7 3 ~ PCT/US94/13323
and a and b are horizontal coordinates of the spots in the service frame, it
becomes negative when a ~ b, this is true when the target surface Q is out of
range. So the sign of the m distance is an indicator of whether the surface Q istoo close or too far from the best focus distance. For positive identification of the
spots (a and b) the computer may turn the beams (S1 and S2) on and off or
otherwise control the amount of energy in each separately in sequential service
frames.
As noted before, the "service frame" provides all necessary information for
adjustments, so an image of acce~able quality can be made, such that the "info
frame" may be processed successfully and quickly.
This may be accomplished according to the following: (1) the selected
sensor for this application has a matrix of 752 x 582 useful pixels; (2) there are
two fields: odd and even; (3) each field col ~sists of 291 interlaced horizontal lines;
(4) each line has 752 pixels; (5) any one field conldil ~s sufficient data for a "service
frame", therefore after processing one "service field" a decision may be made
regarding adjustments before another "service field" or an "info frame" is taken.
During acquisition of a "service field" only 12 equally sp~ced hol i~onlal linesare p, ocessed (one in each of 24 lines). The other 23 lines of each 24 are skipped
(not acquired). ~kipping or dumping of the lines may be done with a much higher
rate (20 MHz in the present embodiment). The 12 active lines are processed in
the following manner: (1 ) each line is divided in 16 sections of 47 pixels each; (2)
one half of each section (24 pixels) is taken for processing, while another half (23
pixels) is skipped; (3) out of the 24 pixel values two exl, eme values, brightest and
darkest, are found and their differences are stored in a "modulation array". Themorll ~l~tion array is organized as a Of H x ObH (16 x 12 decimal) matrix. A mean
value for each of the 24 pixel strips is also c~lcl ll~ted and stored in the "threshold
array", organized similarly to a "modulation array". The examples of both arraysare shown in the following tables:
2~ 62673 ^ ~
WO 95/16973 - PCT/US94/13323
~o_ooo~
o g o o o o o o o g o o
S --o ~ ~ C~ C, o) _ g _ ~
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oooooooooooo
~ ~ ~ o ~ ~ ~ . _ _ _ o 8
oo_____ ____
oooooooooooo
~ ~ ~ ~ ~ N _ O O
gOOOOOOOOOOO
O O O O O O O O O O O O
,~ O ~ 8 ~ a~
~ ~ 8 t.~ ~1 ~) ~ N
gOOO$OOOOOOO
~ o 8 ~J 8 8 ~1 ~ N
O O g $ g g o O O O O O
g Og o O O O --O --O -- -- --o
n 0
~ D g 8ggggoooooo
o 0 ~ ~ ~ 0 ~ o o 0 ~
o o 'o o g o -- _ ~ _ ~ _
o o o o o o o o o o o o
~_o-88g~0~
g g g o o o o o o g o g
~ ~o o o g o g _ o o 8 o ~o
oooooooooooo
~5 D ~1 0 C~ 0 ~ C~ 8
O O O O O O O O O O O O
O O O O O O O O O O O O
o 0 ~ ~ 0 ~ o n o 0 o _
0 ~ ~
g g 8 g g 888 g 88$
o U~ 0 4 ~ U~ ~ ~ ~ 0 ~ ~
g8g g o 88888 g 8
o ~ ~ c~ OD ~ $
880888888088
o _ ~ ~ ~ U~ ~o ~ 0 0 ~ ,'
2 1 62673
~W0 9S/16973 ~ ;` PCT/US94/13323
11 ..
~g~ N ~ ~ ~ ~ ~ ~ ~ .~
C~OOOOOOOOOOOO
~OOOOOOOOOOOO~
1~ N Q tl~ G~ c~) N 8 1~ n
N O O O O O O O O Q O O O
~OOOOOOOOOOOO~
0 o ~ a~ o ~ ~ o
N ~ ~ ~ O
~gggogg8ggggg~
~ ~ N cn ~_ ~ O C~
~googoggogoogogogog~
0 00 N ~ 00 ~ c15 C~
O O O O O O Q Q O Q O O
~noooooooooooo~
1~ ~) O ~ ~ ~ t~ 0 a~ N
~ o o o o o o o Q o o o o
tDOOOOOOOOOOOOa~
._ o u~ o ~ o a~ o ~ o~ o o
gooogggooggogg~
o
. ~ O O
~ooogggoo
m
~ 00~000~ 0 00 CD
O O O O O O O o O O O $ O O
OOOOOOOOOOOO~D
t~5 N O 0 ~7 0 .~
n _ ~ o o o ~ _ ~ ct~ ~.
~ogoggg 8
~ 0 ~ ~) N ~ 0 0 ~ ~ ~ ~
000gOOOOOOOOO
~OOOOOOOOOOOO~t
N ~') 0 ~ 0 ~ ~ 0
O O O O O O Q O O O O O
~OOOOOOOOOOOO~
0 ~ t~5 N ~ 5 0 c~) 0 ~ 0 0
~ ~ ~ O . O ~- ~ ~ ~ ~ ~
~gg$gggggg$$g N
0 ~ 0 4-- ~ U~ 1~ ~ ~ 4_ ~ 0
~ogggQOgggggo_
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O ~ N ~ ~ u~ 0 0 t~5 '`
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WO 95/16973 2 1 6 2 6 7 3 PCT/US94113323 ~
12
The modulation array reflects areas of data activity in the image frame. The
rectangular area with the xy coordinates (column * row) of: 62, 65, a2, a5 has
elevated modulation values and indicates the image of the label (in this particular
example a UPS-code label was used.). The next procedure pinpoints the middle of
the area of i"leresL. For this purpose a low pass spatial filter is applied to the array
of modulations as a running window of 3 units wide, independently of horizontal and
vertical coordinates. The result of this processing is the two linear arrays (14 and 10
values long correspondingly). Maximum values (and the label middle) is indicated in
bold typeface.
The next object is to identify the boundaries of the label area. For this purpose
a tolerance value is c~lc~ ted as a function of an average modulation in the middle
of the label (Mm) and average modulation for a large vicinity, surrounding the label
(Mv).
Mm - 1/9 m9
Moduiations of 9 elemer;ts of a 3 x 3 matrix with the determined label center in the
matrix are added together and divided by 9.
Mv- 1/81 m81
A similar operation is ,ue, ru" "ed on 81 elements of a 9 x 9 matrix. Thus, a tolerance
value Tm = (k * Mm + Mv)/2k. For this example k = 4 is an optimum because the
vicinity area (81 points) is 4 times greater than the label area (4 x 5 = 20 points).
Next, the modulation values are being compared with the tolerance value, starting
from the deler" lil led label center, and moving outward until lesser than Tm values are
found. One more row or column is then added to this area for safety. The x and ycoorcli~ IdleS, outlining the zone of the label are stored. These coordinates are used
for optimum processing of the info-frame. All lines preceding (and following) the
outlined zone in the frame may be disregarded. The i, Iror",dlion positioned to the left
and to the right of the outlined zone may also be disregarded and need not be
acquired. This process of line skipping and pixel skipping substantially redl ~ces the
image processing time.
~wo 95/16973 2 1 6 2 6 7 3 -` PCT/US94/13323
Tl " eshold surface values may be found by simply a\,e, ayi"g 9 tl " es h o l d values
for a 3 x 3 matrix surrounding the determined label center and applying this averaged
threshold for the whole zone. This method is acceptable for relatively small size
labels (like UPS-code labels), for which val id~iOnS of illumination intensity do not vary
si9nirical ILly within the label area. For large size labels, (like some PDF 0417 code
labels) adapt~ion of the threshold surface within the label boundaries is required. In
this case, in the array of "row" lhl esholdst each number situated ekle, I ,ally to the label
and immediately next to a Ihl eshold value on the border of the label (more accurately,
a blob representing a presumed label), is substituted with the value of the nearest
blob value for the purpose of ~Icl ~ations. Then the low pass 3 x 3 filter is applied to
the area inside the blob boundaries. The resultant array of smoothened thresholdvalues then may be used as the ll "esholding surface for the fast ~repr~cessing of the
info-frame. As discussed earlier, these values are loaded by the DSP in to the
comparator during the info-frame acquisitions.
15- C. Flcros~re Control
In order to properly function in a variety of lighting conditions the present
invention is prererably provided with exposure control. means. Ambient light
conditions may collllllollly range from 3 to 100,000 lux. An office illuminated by
fluorescent lamps typically ranges from 300 to 500 lux. Fluorescent lights normally
flicker at a frequency of twice the alternating power source frequency.
Therefore, a preferred embodiment of the present invention should work in
flickering lighting conditions and be ~djust~hle from 30,000 to 1. The ratio between
the maximum and minimum instant values of illumination intensities are normally on
the order of 3 to 1 (where 90 phase shift li-Jhlil ,9 is not utilized). It is also necess~ry,
in a pr~re, It:d eAelllpldl y embodiment that sensor sensitivity adjustments take place
in an order of milliseconds such that the amount of time remaining for image
acquisition and decoding is Gplill,i~ed.
As disclosed herein, the presenl invention describes a method and apparatus
for reading two~li",e"siollal optical il~ru~ dlioll sets, which delivers image information
WO 95/16973 . ., ~ PCT/US94/13323
14
sequentially in "frames" which are divided in two fields where a interlaced typetelevision sensor is utilized. Where a non-interlaced sensor is utilized each "frame"
constitutes a single field. According to the present invention these fields may be
classified into two groups, i.e., "service-field" and "i"rur",ation field."
Service fields are processed much more rapidly than are inror",dlion fields.
Service fields are processed only for ca" ,era house-keeping purposes, i.e., sensitivity
adjustments and the like. In an exemplary preferred embodiment sensitivity
adjustments may be made according to the following method:
(a) A first field is taken with a default exposure of 417 ,us where a non-
lo interlaced sensor is utilized. Where an interlaced sensor is utilized the
first field is exposed for 417 ~s and the second field is exposed for 50
,us.
(b) The first field is analyzed to determine the ambient light level
(illumination level). Where the level of illumination of the first field is
. insufficient the exposure time is increased, in such a case two
conditions are possible:
(1 ) The signal level is determined to be reliable for
calculating an optimal exposure time (in such a case the
exrosl Ire time is modified accordingly and an inror" Idlion-
field is acquired). The maximum exposure time is 4.17
ms (based upon empirical studies of image smear
caused by hand motion and the like), and the tolerable
exposure time is between 4 to 5 ms (by selecting 4.17 ms
certain advantages are obtained). If the required
optimum exposure is between 4.17 ms and 12 ms (dim
level), the information-field is taken with 4.17 ms
exposure and the ADC reference levels are adjusted to
preserve co, Ill asl ("image normalization"). If exposure
time is r;llçl ll~ted to be more than 12 ms (dim level), then
~WO 95/16973 2 1 6 2 6 7 3 PCT/US94/13323
auxiliary lighting is utilized (xenon strobe light or the like)
during acquisition of the information-field.
(2) The signal level is found to be too small to calculate
optimum e-~posl lre In this case the auxiliary light source
iS also used (assuming very dark ambient lighting
conditions).
(c) If the first service field taken with the default exposure produced an
image which is too bright a second service-field is taken with the
exposure reduced by a factor of ten (47 microseconds). With this
exposure setting an accurate prediction of optimal exposure may be
made. However if the image is stiil to bright a third (or subsequent)
service-field may be taken. When an unsaturated white level is
dele""i"ed optimum exposure time is calculated and the information-
field is acquired.
D. Aiming andTriggering
Once activated by a user (via suitable activation means such as a trigger
switch voice activation or code recognition system) or a HOST computer the
appardl.Js begins to obtain "service fields." The DSP processes these "service fields"
rapidly since only a few lines distributed throughout the field are ,c ,ucesse~ The DSP
then measures the signal level and ~jUStC exposure to within optimum limits. TheDSP then determines range and/or focal length via a look-up register (the
specifications of US Serial Numbers (1) 07/960 520 filed October 13 1992; (2)
08/277 132 filed July 19 1994; (3) 07/947 673 filed September 21 1992; and (4)
08/281 884 filed July 28 1994 are hereby incorporated by rerere"ce in their entirety).
In a simplified ex~mpld,y e",bodi,ne"l an apparatus accordil-g to the present
invention may then produce two beams of visible light (with the imaging lens forexample situated between them). The beams converge in one spot at the taryeted
disla"ce. The DSP may activate the beams whenever it is desirable to obtain a field
with the beam spots ~.resel1l. In another ex~mplary embod;" ~enl the apparatus of the
WO 95/16973 ; - - PCT/US94/13323
2~ 62673 ~
16
pr~se, 1L invention may obtain range and focusing information by analyzing the shape
of the fiducial marks produced by the beams. Likewise, the apparatus may simply
obtain an image when beam convergence is obtained.
In an eflort to save processing time embodiments may utilize only three
horizontal lines in the center of the field (fiducial spot carrying area). Since only a
limited accuracy of range to the target is required (as determined by the optical string
depth of field) it is only necessary to measure the width of the area covered with the
spots. In order to increase sensitivity it is possi~lc to subtract the field taken with the
beams off from the field with the beams on. The result may be integrated so as to
distinguish weak contrast beam spots (this condition occurs whenever ambient
lighting is bright [the use of high intensity orange LED's in a pulse mode is desired so
as to " ,a~(i" ,i,e insldnla"eous co~)lr~sl]). In order to facilitate operator visibility a long
current pulse to the LED's may be employed whenever the DSP is not obtaining an
image.
In an exemplary embodiment a pair of LEDs may serve two purposes, namely
operator aiming and focusing. P,ererably, and as ~lisclosed by FIGS. 9A-9H and 10,
the a,c paral-Js simply takes an image when the array is at the correct distance from
the optically readable information. In this way an opera.tor may simply aim the
a~ ardl~s at the i"ror" ,dlion to be read at the apprw(illlale in focus distance from the
illru~ alioll. In operation the operator simply points the LED spots at the inror",alion
to be read and moves the apparatus away from or closer to the information and the
apparatus obtains an image as soon as the two LED spots converge.
E. Descr~iption of FIGS. 9A-9H
FIGS. 9A through 9G comprise an electrical schematic which collectively
illustrate an exemplary single array embodiment of the electrical components of a
present invention.
FIG. 9A illusll dles the timing generdlor (U3) provides timing and control signals
to the driver (U1 ) which in turn controls a two-dimensional array via U2. External
shutter control and operation is facilitated via U4A and U4B and supporting circuitry.
~WO 95/16973 2 ~ 6 2 6 7 3 ~PCT~US94/13323
17
The timing generator (U3) is also capable of independently providing shutter timing
signals to the array (20 ms to 0.1 ms). However, the external shutter in an exemplary
emboclimen~ is capable of shutter speeds down to 2.0 ,us. This configuration allows
continuous selection of an exact ~xr~osl lre setting rather than a forced closest setting.
FIG. 9B is a continuation of the electrical schematic partially illustrated by FIG.
9A illu~lraliny the computer ,crucessi,-y unit (CPU; U8) and related con,pG"ents. U8
is operates a 32 MHZ device operating at the array frequency of 28.3 MHZ. The core
logic (U10) for the CPU is an address decoder coupled with a latch (U9) and the
addl~ss bus driver (U12 and U13). The reset circuit, memory logic, and buffers are
also illustrated. An exemplary driver circuit for a display is also shown.
FIG. 9C is a continuation of the electrical schematic partially illustrated by
FIGS. 9A and 9B. FIG. 9C illustrates a 32 bit-wide FFT static random access
memory (FFT-SRAM; U15-U22). The FFT-SRAM provides a 64 bit by 32 bit memory
which acts as a continuous bank transparent random ~ccess memory for the CPU
(U8). Associated FFT-SRAM logic and buffer components are also illusl,dlecl.
FIG. 9D is a continuation of the electrical schematic partially illustrated by FIG.
9A-9C. FIG. 9D illusl~ales an exemplary FLASH EPROM system (U24-U25)
providing for software updates while allowing for the access speed of conventional
SRAMs. Also illustrated are voltage control for programming the FLASH EPROMs
(see also, FIG. 9H).
FIG. 9E is a continuation of the electrical schematic partially illustrated by
FIGS. 9A-9D. FIG. 9E illustrates the frame SRAM which stores frame images (one
of the two array fields). The same field is taken each time rather than a random field.
U26-U33 are the memory chips. Since the processor has a 32 bit data bus and the
image has an 8 bit resolution the memory is organized as a single 256 kilobyte by 8
bit memory. When the CPU (U8) is reading this memory the memory provides the 8
lower bits and the data bus buffers (U35-U36) provide the upper 24 bits (all 0's). Also
illustrated are the associated buffers and logic. The address decoder (U34) allows
WO 95/16973 2 ~ 6 2 6 7 ~ - - PCT/US94/13323 ~
18
sequential enablement of each RAM chip (U26-U33) so as to reduce energy
consumption.
FIG. 9F is a continuation of the electrical schematic partially illustrated by
FIGS. 9A-9E. FIG. 9F illustrates the imager having an 8 bit A/D converter (U43).U43 is provided two I ~rerel ~ce vollages by U40 and U41 and their respective latches.
U42 is a buffer and amplifier. The array sampler (U44) is also illustrated. FIGS. 9G
and 9H generally illustrate the power supplies.
G. Description of FIG. 10
FIG. 10 is a flow chart illustrating the program logic obtaining an image for a
preferred embodiment of the present invention. The logical steps of an exemplarycontrol software utilized to pel ron" the processes of a single array embodiment of the
present invention. In operation the array, whether a conventional charged coupled
array or a CMOS device, first consists of a hardware initialization step wherein the
array is purged of any accumulated random charge and variables are set to zero.
The Initialization step may begin upon activation of the apparatus through either
operator intervention via a keyboard key, voice, or the like, or via code detection
means (such as disclosed in USSN 08/277,132), orthe like.
A sample field (service fielcl) is taken and the quality of the exposure is
determined agair,sl a set of preset factors. In the case of reading optically readable
information sets these factors may include a set of predefined conditions which if
present are likely to lead to a s' ucessful read, i.e., decoding. Where decodability of
an image to be taken is not an issue the prospect of sl~ccessful analysis of a
prospective image to be recorded may be determined via a set of other user
controllable predefined conditions.
For example, it may be seen exposure control is a primary factor, thus,
exposure quality may be determined against such a set of standards. If a threshold
exposure level is not determined exactly, the apparatus will ~llelllpl another field
sample at, for example, another exposure setting. Such step may utilize a fuzy logic
or other artificial intelligence means to determine the next most likely setting.
~WO 95/16973 2 1 6 2 h 7 3~ PCT/US94/13323
19
If the sample field meets the selected standards then, for example, a set of
correction values may be generated for, for example, light non-uniformity, and
imaging lens and/or artificial illumination source performance, or the like. The array
is then purged and the apparalus is ready to determine whether another selected
cOIl.liliorl exists. For example, focus quality. In an exemplary embodiment focus is
determined via the position of a spot or spots produced by a light emitting diode
(LED), or the like, in the field of view of a second field sample.
G. Portable Data Terminal
Any embodiment of the pr~se, ll invention may be i"c~"uo, dled into a hand-held
data terminal such as described in any of the following co-pending United StatesPatent Applications (said applications incorporated herein in their entirety by
r~rerence): (1) as the reader engine in the "Reader for Decoding Two DimensionalOptical Information" described in USSN 07/919,488 filed on July 27, 1992, USSN
07/889,705 filed on May 26,1992 (now abandoned), and USSN 07/849,771 filed on
March 12, 1992 (issue fee paid September 16, 1993); (2) as a reader engine in
USSN 07/305,302 filed January 31, 1989, USSN 07/345,200 filed April 28, 1989,
USSN 07/347,602 filed May 3, 1989, USSN 07/347,849 also filed on May 3, 19,89,
USSN 07/426,135 filed October 24,1989, USSN 07/558,895 filed on July 25, 1990,
USSN 07/561,994 filed July 31, 1990, USSN 07/633,500 filed December 26, ~990,
USSN 07/660,615 filed February 25,1991, USSN 07/674,756 filed March 25, 1991,
USSN 07/719,731 filed June 24,1991, USSN 07/735,610 filed July 23, 1991, USSN
07/777,691 filed October 10, 1991, and Serial NQ 07/960,520 filed on October 13,1992.
H. Description of FIG. 11
FIG. 11 is a side elevational view of an exemplary embodiment of a single
sensor portable data file reader module 10 adapted for use with a hand-held dataterminal 24 and 28 such as illustrated in FIGS. 13 and 14-14B. A single two-
di"~e,1sional pholose,1sitive array 18 (e.g. a charge coupled device or CMOS array)
is affixed, preferably in a central position, to a rectangular or similarly shaped
WO 95/16973 2 1 6 2 ~ 7 3 ~ PCT/US94/13323 ~
recessed housing 22 which provides a rigid structure to which the components of the
data file reader module 10 are secured. The housing 22 extends at its ends
perpendicularly to the plane of that portion of the housing 22 to which the
photosensitive array 18 is affixed.
A left LED 12 is mounted on one such housing 22 extension and a right LED
14 is mounted on the other housing 22 extension. The pair of LEDs 12 and 14 are
mounted in such a manner that the center lines of the beams of emitted light
converge at the apex of the angle formed by the two said center lines such apex Iying
on a line normal to the plane formed by the pl ,olosensili~/e array 18 and such normal
lo line intersecting said plane of the pl~olosensili,/e array 18 preferably at the center of
said array.
The distance d from the photosensitive array 18 at which the beams of light
emitted from the LEDs 12 and 14 converge corresponds to the focal distance of a
fixed focus lens 16 said lens 16 mounted on the photosensitive array 18. In an
e,c~",,~lary e"lbodi",enl of the invention the fixed focus lens 16 has a focal distance
of 8.5 inches and an aperture such that the depth of field of 4.0 inches. The depth of
field of the lens 16 allows for images within a range of 8.5 +/- 2.0 inches (6.5 inches
to 10.5 inches) to be in focus. This range over which the image focus is maintained
aids the human operatorwho may place the data file reader module 10 at imprecisedisla"ces from the data file to be read. So long as the data file reader module 10 is
placed within the focus range the image will be in focus.
In a further embodiment the lens 18 may have a variable focal length such
that long range or short range data file readings may be possible. In an additional
further embodiment the lens 18 may have a variable aperture such that the depth of
field and the image brightness may be varied as well. Control of the focal length
depth of field and image brightness may be processed and controlled by the DSP.
A xenon flash tube with back reflector 20 is mounted near the fixed focus lens
16 (the flash tube 20 is partially hidden by the lens 16 in FIG. 11). The xenon flash
tube 20 provides supplemental lighting of the data file image to be read when the
~W0 95/16973 2 1 6 2 6 7 ~ PCT/US94/13323
ambient light conditions are insufFicient for proper image ~posl Ire. The back reflector
of the xenon flash tube 20 provides concentration of the supplemental light on the
data file image area and further prevents direct light incident on the photosensitive
array 18. The use of the xenon flash tube 20 is controlled by the DSP.
I. Description of FIG. 12
FIG. 12 depicts a second exemplary embodiment of the data file reader
module 10 adapted for use with a hand-held data terminal 24 and 28 such as
illustrated in FIGS. 13 and 14A-14B. In this embodiment implemented in data
terminal 24 the pl ,olosei1sitive array 18 lens 16 and LEDs 12 and 14 are mounted
to the rectangular or similarly shaped recessed housing 22 at one end of the housing
22, and the xenon flash tube with back rerleclor 20 or the like is mounted at the other
end of the housing 22. An advanlage of this embodiment is the allowance of a larger
xenon flash tube 20 capable of producing greater amounts of supplemental light.
J. Description of FIGS. 13 and 14A-14B
FIG. 13 is perspective view of a hand-held data terminal 28 illustrating an
exemplary module embodiment of the present invention residing in an external pod
26 for attacl""enl to a hand-held data terminal 28. The data file reader module 10
is frontally mounted within an external pod 26 such that the opening of the recessed
housing 22 faces in a forward direction. With the module 10 thus mounted the
~o beams from the LEDs 12 and 14 are frontally emitted such that data files to be read
are positioned dir~ctly in front of said data ter"~inal Iying in a plane parallel to the
front edge of said data terminal 28 and parallel to the plane of the photosensitive
array 18.
FIG. 14A is a top perspective view of a second hand-held data terminal 24
containing an exemplary module embodiment of the present invention. Said data
ler" ,i"al 24 is desiy"ed to be used such that it is frequently laid upon a planar surface
- for input of data by means of a stylus or the like when not used for data file reading.
Such conditions of use require said data terminal 24 to remain stable during stylus
implemented data input and to remain flush with the surface upon which said data
.
W095/16973 ;~ 1 6 2 6 7~ PCT/US94/13323
terminal 24 is laid. As required, said data terminal 24 may readily be employed for
data file reading purposes.
FIG. 14B is a bottom perspective view of the terminal 24 of FIG. 14A. The
data file reader module 10 is mounted directly within the hand-held data terminal 24
so that said module 10 is flush or nearly so with the bottom surface of said terminal
24. Said module is mounted such that the beams form the LEDs 12 and 14 are
downwardly e"~illed such that the data files to be read are positioned directly beneath
said data terminal 24, Iying in a plane essentially parallel with the bottom surface of
said data terminal 24 and essentially parallel with the plane of the photosensitive
array 18.
