U.S. patent number 3,742,833 [Application Number 05/152,917] was granted by the patent office on 1973-07-03 for system for optically encoding an item and verifying same.
Invention is credited to Lawrence J. Matteson, Stuart F. Ring, John M. Sewell.
United States Patent |
3,742,833 |
Sewell , et al. |
July 3, 1973 |
SYSTEM FOR OPTICALLY ENCODING AN ITEM AND VERIFYING SAME
Abstract
Apparatus for optically encoding an item and verifying same,
generally including a rotatable index table for sequentially
accepting items and carrying each item to a first station where
direct printout photosensitive material is applied to a
predetermined portion of the item by spraying, to a second station
where an optical code image is formed by ultraviolet radiation
impinging on a plurality of piezoelectric elements and projected
onto the photosensitive material and printed out thereon. The item
is then rejected from the table and preferably read at a
verification station to verify the accuracy of the encoded
data.
Inventors: |
Sewell; John M. (Rochester,
NY), Matteson; Lawrence J. (Rochester, NY), Ring; Stuart
F. (Rochester, NY) |
Family
ID: |
22545007 |
Appl.
No.: |
05/152,917 |
Filed: |
June 14, 1971 |
Current U.S.
Class: |
250/580; 396/429;
250/570; 310/330; 347/224 |
Current CPC
Class: |
B07C
3/18 (20130101); G06K 5/00 (20130101); B07C
3/10 (20130101) |
Current International
Class: |
B07C
3/10 (20060101); B07C 3/00 (20060101); G06K
5/00 (20060101); B07C 3/18 (20060101); G03b
029/00 () |
Field of
Search: |
;95/12,1R ;346/17R
;355/27 ;310/8.5,8.6 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Greiner; Robert P.
Claims
We claim:
1. An apparatus for photographically encoding an item with visual
intelligence, comprising:
a rotatably mounted index table for receiving such item to be
encoded;
a first station having means for applying a coating of direct
printout photosensitive material to a predetermined area of such
item;
a second station having means for determining and optically
projecting said intelligence onto said coating of photosensitive
material to produce a direct printout image of said intelligence on
such item; and
means for rotating said table to sequentially position such item at
said first station and said second station, said rotating means
including means for ejecting such item from said table after said
intelligence has been projected onto such item.
2. The invention of claim 1 including means for optically reading
said intelligence on such item to verify the accuracy of said
intelligence.
3. The invention of claim 2 wherein said reading means is
positioned to read said intelligence on such item as such item is
ejected from said index table.
4. The invention of claim 1 wherein said applying means includes
means for spraying a coating of direct printout photosensitive
material onto such item in said predetermined area of such
item.
5. The invention of claim 1 wherein said first station includes
means for registering such item relative to said applying means to
insure that said photosensitive material is accurately coated on
said predetermined area of such item.
6. The invention of claim 4 wherein said first station includes
means for registering such item relative to said spraying means to
insure that said photosensitive material is accurately sprayed on
said predetermined area of such item.
7. The invention of claim 1 wherein said determining and projecting
means includes:
means for producing a beam of ultraviolet radiation;
piezoelectric means for modulating said beam to form a pattern
representing said intelligence; and
means for optically projecting said pattern onto said predetermined
area of such item.
8. The invention of claim 7 including means for electrically
controlling said piezoelectric means to form said pattern.
9. The invention of claim 7 wherein said direct printout
photosensitive material is sensitive in the ultraviolet region
only.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a system for encoding an image upon an
item and for verifying the image and more particularly to a system
for producing an encoded image by optical means wherein the image
is formed by modulating a beam of ultraviolet radiation by means of
piezoelectric elements and a permanent record of the image is
produced on direct printout, photosensitive material which is
applied to the item.
2. Description of the Prior Art
In many applications it is desirable that an optical code be
applied to an item so that the coded information may be used to
subsequently control various operations relating to the item, for
example, the handling and sorting of items such as letters, checks,
invoices, or the like. It is desirable to optically encode on the
item information recorded on the document, such as the zip code or
the like. The optical code may be read more easily than the
information imprinted on the document and, therefore, contribute to
the reliability and accuracy in handling the item. In such
applications, it is desirable that the code formed on the item be
done so rapidly, accurately, and with little or no further
processing steps. Present systems utilizing phosphorescent ink are
unsatisfactory since the ink tends to blur and tends to diffuse
over an area wider than the area it is desired to print the bar
code. In order to attain accuracy, therefore, it has been necessary
to utilize impact printing techniques which are relatively slow and
require repeated maintenance of the printing members which tend to
wear out quickly.
SUMMARY OF THE INVENTION
It is thus an object of the present invention to provide a system
for optically encoding on an item information relevant to the
subsequent processing of the item which is efficient and economical
and which requires a minimum of maintenance.
It is a further object of the present invention to provide a system
for encoding an optical bar code on an item wherein further
processing beyond imaging of the bar code on the item is
unnecessary and the minimum number of steps for producing the bar
code on the item are needed.
In general the system according to the present invention comprises
means for applying a coating of photosensitive direct printout
material to a portion of an item; means for modulating a beam of
radiation through piezoelectric elements interposed in the path of
the beam according to a predetermined pattern to produce a
modulated beam corresponding to the bar code to be produced on the
item; and means for projecting the modulated image onto the
photosensitive area to produce a direct printout image of the bar
code on the item. A verifier is preferably provided for reading the
imprinted bar code and comparing it with the signals used to
control the piezoelectric modulator to verify the accuracy of the
imprinted code. In a preferred embodiment, letters are fed to a
four-sided index tray which carries individual letters to a spray
station where direct printout photosensitive material is applied to
a letter at the spray station by means of a nozzle which moves
relative to the letter to spray the material on the letter in a
predetermined area. Thereafter, the letter is rotated to a writing
station comprising a source of ultraviolet radiation, a plurality
of piezoelectric reeds disposed in the path of the beam of
ultraviolet radiation, a shutter mechanism for thermally shielding
the piezoelectric modulation mechanism from the heat of the
ultraviolet radiation source, except during exposure and for
providing a controlled exposure time and an optical system
preferably comprising a quartz lens and a lens system which
projects the ultraviolet optical bar code image onto the sprayed
area of the letter.
BRIEF DESCRIPTION OF THE DRAWINGS
In the detailed description of the preferred embodiments of the
invention presented below, reference is made to the accompanying
drawing, in which:
FIG. 1 is a perspective view of a preferred embodiment of apparatus
according to the present invention for optically encoding an item
such as a letter and for verifying the encoded information;
FIG. 2 is a partial plan view of the apparatus of FIG. 1;
FIG. 3 is a partially sectional elevational view showing details of
the registration mechanism of FIG. 1;
FIG. 4 is a partially sectional perspective view of the letter
clamping mechanism of FIG. 1;
FIG. 5 is a partially sectional perspective view of the letter
ejection mechanism and pinch belts of the apparatus of FIG. 1;
FIG. 6 is a partially sectional perspective view of the letter stop
mechanism of FIG. 1;
FIG. 7 is a perspective view illustrating the basic elements of an
optical bar code projection means which may be used in the
apparatus of FIG. 1;
FIG. 8 is a partially sectional top plan view of structure
embodying the elements of the projection means of FIG. 7;
FIG. 9 is a partially sectional elevational view of the projection
means of FIG. 8;
FIG. 10 is a partially sectional perspective view of the shutter
mechanism of the projection means of FIGS. 8 and 9;
FIG. 11 is a partially sectional perspective view of the
piezoelectric light modulation mechanism of the projection means of
FIGS. 8 and 9;
FIG. 12 is a partially sectional perspective view showing the
piezoelectric elements of the mechanism of FIG. 11 in greater
detail;
FIG. 13 is a partial elevational view showing the piezoelectric
elements of the mechanism of FIG. 11 in the at rest position or
bent either into or out of registration with a light slot;
FIG. 14 is a schematic view illustrative the operation of a
piezoelectric element of the mechanism of FIG. 11;
FIG. 15 is a partially sectional elevational view schematically
illustrating a preferred form of optical bar code reader according
to the present invention;
FIGS. 16-19 are schematic diagrams of a preferred form of
electrical circuit to be used in conjunction with the reader of
FIG. 15;
FIGS. 20 and 21 are perspective views illustrating alternate
embodiments of optical bar code projection means;
FIG. 22 is a schematic illustration of a letter showing the optical
bar code for the Zip Code in the mailing address;
FIGS. 23 and 24 are tables respectively illustrating the decimal to
binary relationship and the decimal to optical binary bar code
relationship.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the figures, there is shown a preferred embodiment
of apparatus according to the present invention for optically
encoding an item such as a letter and for verifying the accuracy of
the encoded information. As shown in FIG. 1, apparatus 30 generally
comprises an index table 32, a letter load and unload station 34, a
photosensitive material application station 36, an optical bar code
projection and exposure station 38 and an optical bar code reader
and verification station 40.
More specifically, apparatus 30 comprises a base member 42 upon
which is mounted index table 32. Index table 32 comprises a
rotatable tray 44 having a plurality of pockets 46 for accepting
items such as letters 56 upon which an optical bar code is to be
imprinted. As shown, pockets 46 may comprise four arranged in a
square about the periphery of tray 44, each pocket 46 being formed
by side walls 48 and 50, end wall 51 and a plurality of rollers 52
journaled in bearings 54 respectively on the lower portions of
members 48 and 50. Rollers 52 are adapted to support a letter 56 in
pocket 46, to facilitate registration at station 36 and to permit
rapid ejection thereof at station 34.
Index tray 32 is adapted to be rotated between a plurality of
stations 34, 36, and 38 at which various operations are performed
on an item supported within a pocket 46. At station 34 an item such
as a letter 56 is fed either positively or by gravity to a pocket
46 where further vertical movement is restrained by rollers 52.
As shown more clearly in FIG. 4, a clamp 190 is provided for each
pocket 46 to hold a letter 56 therein. Clamp 190 is hingedly
mounted on the rear of wall 50 by brackets 192 and projects through
a slot 194 in wall 50. Clamp 190 is normally spring biased to a
letter holding position by means of a suitable spring such as
compression spring 196 bearing against member 198 of clamp 190.
Member 198 projects below rollers 52 and is engageable by a
solenoid mechanism 200 to move clamp 190 into an unclamping
position against the bias of spring 196.
After an item such as letter 56 has been loaded into pocket 46 at
station 34, solenoid mechanism 200 is deactivated to permit clamp
190 to clamp letter 56 and index table 32 is rotated to station 36.
Station 36 comprises a registration mechanism 58 and a
photosensitive material application mechanism 60. Registration
mechanism 58 is adapted to position letter 56 relative to mechanism
60 so that suitable photosensitive material may be applied to a
predetermined area of letter 56.
Registration mechanism 58 comprises a continuously driven conveyor
belt 64 mounted on members 66, belt 64 being swung into and out of
engagement with rollers 52 to drive the rollers. As table 32 is
indexed to station 36, a suitable cam mechanism 69 depresses
mechanism 58, thus allowing rollers 52 to clear belt 64.
After table 32 has stopped at station 36, cam mechanism 69 forces
conveyor belt 64 mounted on members 66 into engagement with rollers
52 to move a letter positioned in tray 46 to the right as shown in
FIGS. 1 and 3 in order to bring letter 56 into registration with a
slot 68 in wall 48.
As shown in FIG. 6 the letter is stopped by a suitable stop member
70 which is controlled to swing into and out of engagement with
slot 72 formed by members 48 and 50 of pocket 46. Control of stop
70 is by suitable control circuitry not shown which is synchronized
with the rotation of table 32 so that as a pocket 46 is indexed
around to station 36, stop 70 is swung out of the path of rotation
of tray 32 until the tray has come to a rest and registration
mechanism 58 has been engaged.
After a letter 56 has been suitably registered with respect to slot
68 at spray station 36, mechanism 60 is activated to apply by
spraying onto the area of letter 56 which is exposed by slot 68, a
coating of a photosensitive material which requires little or no
further processing once it has been exposed to suitable radiation
to develop a coded image in the material. Preferably, such a
material is not sensitive to light in the visible spectrum and
comprises a print-out negative working, ultraviolet-sensitive
material. A number of such materials are suitable for this
application such as polyacetylenic compounds such as those
disclosed in U.S. Pat. No. 3,501,302 of Foltz issued Mar. 17, 1970.
In general, the material selected should preferably be
negative-working i.e., give a colored image in areas exposed to
suitable radiation; have high resolution; have high speed; be
relatively stable under normal daylight and artificial lighting; be
sensitive within a relatively narrow range of the nonvisible
spectra, preferably the ultraviolet; require no processing after
exposure; and be readily applicable by a variety of techniques such
as spraying or the like at a reasonable cost.
Other suitable photosensitive materials which require no processing
after exposure to a suitable image may also be used.
As shown more clearly in FIGS. 1 and 2 mechanism 60 comprises a
spray gun 73 mounted from rails 74 and 75 by means of carriage 76.
Preferably, the suitable photosensitive material is supplied to gun
73 through suitable conduits 78 which communicate with gun 73
through carriage 76 and hollow support member 80.
Preferably, the spray gun 73 sprays suitable radiation sensitive
material onto the letter through slot 68 as gun 73 is returned from
the position shown in dashed lines as at 82 in FIG. 2 to the at
rest position as at 84 out of the way of the circle of rotation of
table 32. It will be understood, however, that the spraying of
letter 56 in tray 44 could also be accomplished during the movement
of the gun 73 from position 84 to 82. Alternatively, gun 73 might
be mounted for rotation to spray the letter in an arcuate path. In
such circumstances, the carriage and rail mechanism shown in the
drawing would be replaced by a suitable rotatable drive
mechanism.
After the predetermined area of letter 56 has been sprayed with a
coating of suitable photosensitive material, index table 32 is
indexed around to exposure station 38. Previously thereto stop
mechanism 70 has been rotated out of the way of tray 32 so that the
index tray 32 may be moved without any interference from stop
70.
At exposure station 38 a suitable encoded bar code image is
projected upon the area of letter 56 which has been sprayed with
suitable photosensitive material. FIG. 7 schematically illustrates
apparatus for forming and projecting an optical bar code image onto
such area. Assuming that a material sensitive to ultraviolet
radiation has been sprayed upon a letter 56, apparatus 89 includes
a source 90 of ultraviolet radiation, a modulator 92 for modulating
the beam produced by source 90 according to a predetermined bar
code pattern, and a projection lens assembly 94 for projecting the
modulated ultraviolet radiation beam onto letter 56. Source 90, for
example, may comprise a suitable ultraviolet lamp 96 enclosed
within a sleeve 98, lamp 96 being cooled by a suitable blower 100
in communication with sleeve 98. Sleeve 98 is preferably of a
material such as quartz, which effectively filters any radiation
from lamp 96 outside of the appropriate ultraviolet region.
Referring now to FIGS. 8 and 9 there is shown in greater detail a
preferred embodiment of projection apparatus according to the
present invention which incorporates the elements shown in FIG. 7.
As shown, apparatus 89 comprises a base 102 upon which is mounted
lamp 96, a quartz sleeve 98 surrounding lamp 96, a lamp cooling
mechanism 104 in communication with sleeve 98, a shutter assembly
106 for controlling the amount of radiation projected from lamp 96,
a piezoelectric commutator or modulation assembly 108 for
modulating the beam of light radiated by lamp 96 past shutter
assembly 106 and a projection system 94 comprising lenses 110 and
112 and a diaphragm 114.
Since ultraviolet radiation can catalyze chemical reactions in
airborn impurities such as oil vapors dispersed in the air which
then build up as a residue on optical surfaces and the like, it is
desirable that the cooling system 104 for the illuminator assembly
and shutter mechanism be filtered using absorbtion-type media. It
is also desirable that the projection system 94 be mounted within a
sealed housing such as housing 113 having sealing plates 116 and
118 at either end thereof, so that the optical elements of the
projection system are protected from water vapor.
Referring now to FIG. 10 there is shown in greater detail a
preferred embodiment of shutter mechanism according to the present
invention. As shown, shutter mechanism 106 comprises a primary
shutter consisting of a drum 122 having a slot 124 formed therein.
Drum 122 is mounted for rotation in bracket 126 and is driven by a
gear drive 128 by means of commutator step motor 130. The primary
shutter 122 will expose the full bar code when radiation from lamp
96 is transmitted through slot 124. The shutter mechanism 122 also
acts as a thermal barrier to prevent the heat of lamp 96 from
affecting commutator mechanism 108.
A secondary shutter mechanism is also provided which may, for
example, comprise blades 132 and 134 mounted for sliding movement
on plate 136. Blade 132 may, for example, be manually actuated by
linkage 138 and blade 134 may be manually actuated by linkage 140.
By means of the blades 132 and 134 selected fields of the bar code
may be imaged onto a letter through manual selection of the
appropriate blades 132 and/or 134.
Referring now to FIGS. 11-14, there is shown in greater detail the
piezoelectric commutator or modulation mechanism 108 according to
the present invention. As shown mechanism 108 comprises a slotted
mask 142 mounted between members 144 and 146 respectively having
recesses 145 and 147. A plurality of piezoelectric elements or
reeds 148 projecting into recesses 145 and 147 are mounted by
members 144 and 146 alternatively on either side of mask 142.
Elements 148 are provided with upwardly projecting portions 150
which partially cover slots 152 in mask 142.
This is more clearly shown in FIGS. 12 and 13 wherein reeds 148 are
shown alternately disposed on either side of mask 142. For example,
reeds 148a, 148c, 148e and 148g may be disposed on the rear side of
mask 142 and reeds 148b, 148d, and 148f may be disposed on the
front side of mask 142. Portions 150 of reeds 148 are shown as
partially covering slots 152 of mask 142 and in their at rest
position cover the lower righthand portion of slots 152 as portions
150a of element 148a is shown covering the lower right-hand portion
of slot 152a. Since it is desired that a slot of light either the
full height of slot 152 or half the height of 152 be projected to
form a half bar or full bar in the photosensitive material supplied
to a suitable letter, reed 148 is so controlled that portion 150
thereof will either be bent into registration with the lower half
of slot 152 as more clearly shown by portion 150d of element 148d
covering the lower half of slot 152d or be bent entirely out of
registration with the lower half of slot 152 as shown more clearly
by portion 150f of element 148f completely uncovering the lower
half of slot 152f.
Stops 154 are provided on either side of piezoelectric elements 148
to limit the lateral flexing of elements 148.
FIG. 14, shows schematically the operation of element 148.
Preferably, element 148 comprises a laminate of flexible
piezoelectric strips 156 and 158 disposed on either side of a
flexible metal strip 160, which may, for example, be made of brass.
Disposed at the base of strips 156 and 158 are electrodes 162 and
164 to which is applied to a d.c. voltage as from a reversible d.c.
source 166. When it is desired to bend the piezoelectric element in
one direction or the other, a voltage of suitable polarity is
applied to electrodes 162 and 164 from reversible source 166.
By suitably controlling a series of piezoelectric elements 148
disposed in registration with slotted mask 142, a beam of
radiation, such as ultraviolet light from lamp 96 transmitted
through the mask may be modulated according to a predetermined
pattern and the modulated beam projected upon a suitable
photosensitive area sprayed on an item such as a letter to produce
an image on the area which corresponds to the desired predetermined
modulated image. In such manner, an optical binary bar code which
is representative of mailing information written on the letter may
be encoded in a preselected area of the letter for subsequent
handling and processing of the letter through the reading of the
code by an optical bar code reader.
After an appropriate bar code has been imaged onto the letter
supported at station 38, the letter is carried by index table 32
back to station 34 where it is ejected from pocket 46 by means of
ejection mechanism 62. This is shown more clearly in FIGS. 1 and 5
wherein ejection mechanism 62 comprises an ejection member 170
mounted on belt 172 which is journaled on pulley 174 driven by a
suitable drive motor 176.
Member 170 is adapted to clear slot 177 formed between members 48
and 50 above wall 51 to push letter 56 to the right as shown in
FIG. 5 where letter 56 is gripped between pinch belts 178 and 180
to carry it past slot 182 in verifier plate 184 where it is read by
optical binary code reader or verifier 186.
Referring now to FIG. 15, there is shown a preferred embodiment of
optical binary code reader 186. As shown, reader 186 comprises a
housing 210 having front wall or plate 184 with a slot 182 therein.
Mounted within housing 210 is a lamp 212 having a reflector 214 for
illuminating the bar code on letter 56 as it is moved past slot
182. The reflected image of this bar code will be transmitted
through slot 182, reflected from mirror 216 and imaged onto
photodiode array 218 by lens system 220.
Photodiode array 218 preferably comprises a linear array of
approximately 50 photodiodes which scan incremental segments of the
optical bar code on letter 56. As will be described in greater
detail hereinafter, each segmental scan detected by diode array 218
is in turn scanned by suitable electronic switching means in such
manner that each diode in the array is sequentially interrogated to
determine its signal level. The electronic scan rate is preferably
such that each bar is scanned at least three or four times. A
full-bar half-bar, no bar determination will then be made by
measuring the length of bar on each scan and taking a vote on the
scan determinations.
Referring now to FIGS. 16-20 there is shown schematically an
electronic system detecting and comparing the optical bar code data
read by reader 186.
FIG. 16 schematically shows a master clock 228 which controls all
the events in the reader. As shown a clock 230 running at twice the
shifting frequency of the photodiode array toggles flip-flop 232
and is gated with the complementary outputs of flip-flop 232 in
gates 234 and 236 to produce two non-overlapping pulse trains of
opposite phase respectively through operational amplifiers 238 and
240. These pulse trains are respectively pulse shifted by
transistors 242 and 244 to provide the 01 and 02 clock signals
required by photodiode 218.
In addition, a 6-bit binary counter controlled by flip-flop 232 is
decoded by gate 246 and by means of operational amplifier 248 and
level shifting transistor 250 provides a data pulse overlapping
every 64th 01 pulse.
The photodiode array and associated circuitry is illustrated in
FIG. 17. Each data pulse is used by photodiode 218 to set the first
stage of its internal shift register and is shifted down the array
by the 01 and 02 pulse trains from master clock 228. As the data
bit is shifted by each location of the register it causes the
contents of the corresponding photosensitive element to be sampled
and to appear on the video output. Threshold amplifier 252 compares
the video output with an automatically generated reference signal
(representative of the reflectance of the individual envelope) to
generate a binary signal which is high for dark areas and low for
light areas. The threshold output of threshold amplifier 252 is
integrated by operational amplifier 254.
At the conclusion of one scan of the 50 elements of photodiode 218
the voltage appearing on the output of amplifier 254 represents the
integral of the bar length perceived as darkened (printed) during
that scan. This voltage is monitored by threshold amplifiers 256
and 258. The threshold of amplifier 256 is twice that of amplifier
258. If the area of the envelope being examined contains a full
bar, the integral will be large, and at the conclusion of a scan
both the high-threshold and low-threshold signals will be high. A
half bar will result in a high on the low threshold output only,
and the absence of a bar will result in neither output reaching the
high state.
As the last element of the photodiode is sampled, a pulse appears
on the Data-I output of photodiode 218. This pulse is amplified by
amplifier 260 and used to sample the states of the high- and
low-threshold amplifiers 256 and 258 to determine whether the scan
just completed was of a full bar, a half bar, or no bar. The
Data-II output of photodiode 218 is used to latch operational
amplifier 262 with its output in the high state. This causes
N-channel FET 264 to conduct and discharge integrator storage
capacitor 266 restoring a zero initial condition to the integrator.
Pulse 64, which is the Data Input pulse for the next scan of the
diode 218, causes amplifier 262 to latch in the low state again and
transistor 264 becomes nonconducting. Amplifier 254 then begins
integration of the next scan.
Processing of the high and low threshold signals to identify full
bar, half bar and no bar regions is performed by logic illustrated
in FIG. 18. Two shift registers are used; Register 270 to store the
low-threshold samples and register 272 to store the high-threshold
samples. The sample pulse generated by amplifier 262 of FIG. 17
shifts registers 270 and 272 and causes each to store an up-to-date
display of the results of the last four scans of photodiode 218.
The criteria used to identify characters are:
a. A full bar is characterized by a three out of four majority of
scans in which both the high-threshold and low-threshold bits are
high.
b. A half bar is characterized by three out of four scans in which
the low-threshold bit is high and the high-threshold bit is
low.
c. No bar is characterized by three out of four scans in which both
bits are low.
The majority voting gates used to recognize a half-bar character
are shown in FIG. 18 for illustration. The gating for full bars and
blanks is similar, differing only in connection to the shift
register outputs. Gate 274 recognizes the condition in which the
last three of the four scans stored all agree that a half bar was
read. For this condition to exist, the contents of the first three
stages of the high shift register are all zero and the contents of
the first three stages of the low-shift register are all one. All
six inputs to gate 274 are then one and the output of gate 274 goes
to zero, indicative of recognition of a half bar character. Thus
the shift register state denoted HHH has been recognized and
correctly interpreted as a half bar. (The X in this notation
indicates an arbitrary or "dont't care" state which may be a blank
b, a half bar h, or a full bar f.)
Three other three-out-of-four shift register conditions are
possible which are also valid indications of a halfbar reading.
They are:
X h h h
h X h h
h h X h
The first condition, X h h h, is trivial as it is identical to the
h h h X condition recognized by G1, but displaced in time by one
scan. the other two conditions are valid and unique indications of
a half bar and are recognized by gate 276 and gate 278 in the same
manner as described above for gate 274. The output of the three
gates are wired together so that a character recognition by any one
of the three causes the half bar output to go low.
Identical sets of gates (not shown) recognize full bar and blank
characters. The significant states of the three character outputs
thus generated are:
a. All high; indicates a noisy signal or an intermediate state
between two of the states described below.
b. No Bar low; indicates that a blank space was recognized.
c. Half Bar low; indicates that three out of four scans have agreed
that the low threshold was exceeded but the high threshold was
not.
d. Full Bar low; indicates that three out of four scans have agreed
that both low and high thresholds were exceeded.
Comparison of the bar code read by the verifier with that supplied
by the computer is performed by the logic illustrated in FIG. 19.
Flip-flop 280 is set to the zero state by the trailing edge of the
sample pulse whenever the No Bar input is high. This step prepares
the circuit for processing either a Half Bar or Full Bar input,
whichever appears next. As photodiode 218 moves from a blank space
to a bar, the No Bar input goes low and shortly afterward, when the
recognition criterion has been met, either the Half Bar or Full Bar
input goes high. This raises the J input of flip-flop 280 and the
trailing edge of the same sample pulse that caused the third
consecutive pair of threshold bits to be stored in shift registers
270 and 272 causes flip-flop 280 to go to the 1 state. The
transition of flip-flop 280 toggles flip-flop 282 and causes it to
go to the 1 state if a full bar is recognized or to the 0 state if
a half bar is recognized.
If the data stored in flip-flop 282 is in agreement with the
computer data stored in the approximate bit location of the shift
register, then the output of exclusive- or gate 284 is zero and the
output of gate 286 is 1 regardless of the other inputs to gate 286.
If an error is present, then the output of gate 284 is 1 and the
output of gate 286 will go to 0 when the error test is performed by
raising gate 286's other inputs to 1. Just after registration of 1
or 0 in flip 282, flip-flop 288 is in the 1 state and the
corresponding input of gate 286 is 1. Flip-flop 288 was set by
recognition of a bar, and that input to gate 286 is also 1. The
incoming Strobe pulse raised, the third input of gate 286, so that
during the duration of the strobe pulse the output of gate 286 is
dependent only on the state of gate 284. If gate 284 has detected
an error, then gate 286's output will drop to zero and thus inform
the computer that an error exists. If there is no error, the
trailing edge of the Strobe pulse sets flip-flop 288 to zero and
generates a shift signal to the shift register storing the computer
data to bring the next bit into position for checking. A delay has
been introduced into this signal to prevent disturbance of the
shift register input to gate 284 until gate 286 has been turned
off. This prevents the generation of false error signals due to
critical timing.
Referring now to FIGS. 20 and 21, there are shown alternate ways
for imaging the optical bar code onto a letter. In FIG. 20, the
modulated image is reflected from concave spherical mirror 300 and
projected through a quartz negative cylindrical member 302; while
in FIG. 21, the modulated image from modulator 303 is reflected
from a toric mirror 304 onto a letter 56 through a transparent
plate 306.
FIG. 22 shows a letter 56 having a mailing address 310 with a Zip
Code 14619 as at 312. The optical binary bar code for this Zip Code
is shown in the lower right-hand corner of letter 56 as at 314.
FIGS. 23 and 24 respectively show in tubular form the decimal to
binary conversion and the decimal to optical binary bar code
conversion which may be used in accordance with the present
invention.
The following features and advantages of the present invention
although evident from the foregoing description and drawings should
be noted:
a. A handling concept that extends the available processing time is
provided by creating a series of processing stations, each having a
processing throughout rate equal to the input acceptance rate. The
item is advanced from one processing position to the next when a
new item is accepted. The printer index tray uses this concept to
extend the available process time by providing four processing
positions, two processing positions being used for spraying the
photosensitive materials and for printing the image bar code
respectively.
b. The photosensitive material used in the system of the present
invention is sensitive in that part of the ultraviolet spectrum
which lies sufficiently close to the visible spectrum to permit
management of the ultraviolet energy by apparatus which uses the
same principles of energy management that are employed in the
management of energy in the visible portion of the spectrum. In the
printer an embodiment of this statement is the use of refractive
lens elements to manage the energy in the 2,200 to 2,800A
region.
c. An important principle employed in the system of the present
invention is the use of a carrier (letter tray) to transport the
letter from one station to another, rather than to pass the letter
by itself from one station to another. This feature prevents
unintentional damage and mishandling of the mail piece.
d. In combination with a source of broad spectral radiance,
spectral filtering is used in the optical bar code reader to
optimally match three items--the spectral radiance from the printed
binary code; the spectral radiance of the background of the mail
piece; and the detector sensitivity. This matching provides the
optimum combination of peak signal to noise and absolute signal
level.
e. The concept of producing unique coded or alphanumeric data on an
individual item by spraying a photosensitive material on the item
and then optically imaging the data provides a means of non-contact
data recording that does not require precise spray control but does
provide fast, high quality recording of data. The data may be
recorded immediately after spraying, at a much later time, or
repetitively. The printer employs this concept by spraying the
photosensitive material on the envelope and in the next processing
step, one-half second later, recording the unique binary bar code
on the envelope.
The invention has been described in detail with reference to
preferred embodiments thereof, but it will be understood that
variations and modifications can be effected within the spirit and
scope of the invention.
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