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Description  |
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BACKGROUND OF THE INVENTION
The present invention relates to mail processing apparatus and more
particularly to apparatus for sorting mail according to whether the
address characters of the mail are printed or hand-written.
Mail having address characters which are printed are further sorted with
respect to ZIP codes by an optical character reader (OCR), while mail
determined to have handwritten characters are sorted with respect to ZIP
codes by hand.
Mail sorting machines sort mail according to the address, using pattern
recognition methods. Pattern recognition methods are effective for printed
characters, but not effective for hand-written characters. Therefore, only
mail with printed address characters can be supplied to mail sorting
machines because the mail sorting machines are required to accurately
recognize address characters.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide mail
processing apparatus which automatically classifies pieces of mail as
having a printed address or another type of address.
It is another object of the present invention to provide mail processing
apparatus which classifies pieces of mail as having a printed address or
another type of address using fewer calculations.
The present invention overcomes the problems and disadvantages of the prior
art by reading information on the surface of the mail and distinguishing
the area of the destination address from the area of the return address.
The statistical variation (i.e., the dispersion) of a characteristic of
characters forming only a portion of the destination address is
determined, and the mail is classified as having either a printed address
or a handwritten address on the basis of the dispersion of the
characteristic.
To achieve the objects and in accordance with the purposes of the
invention, as embodied and broadly described herein, there is provided
apparatus for processing mail having a destination address area including
a destination address consisting of a plurality of characters and for
selecting mail having a printed destination address. The apparatus
comprises means for detecting the position of the destination address area
on a piece of mail, means for generating signals representative of
characters within the destination address area, means for calculating the
dispersion of a characteristic of the characters within only a portion of
the destination address area, means for comparing the calculated
dispersion to a predetermined limit, and means for selecting the piece of
mail as having a printed address when the dispersion is less than the
predetermined limit.
The accompanying drawings, which are incorporated in and constitute a part
of this specification, illustrate one embodiment of the invention, and,
together with the description, serve to explain the principles of the
present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view of a piece of mail including a destination address
and a return address;
FIG. 2 is a diagrammatical view of a mail processing machine which
constitutes a preferred embodiment of the present invention;
FIG. 3 is a block diagram showing the machine of FIG. 2;
FIG. 4 is a diagram illustrating four possible orientations of mail fed
into the machine shown in FIG. 2;
FIG. 5 is a diagrammatical view showing address position detectors of FIG.
2;
FIG. 6 is a graphical representation showing signal levels of information
detected by the address position detectors of FIG. 5;
FIG. 7 is a diagrammatical view showing the character detector and
recognizer of FIG. 2;
FIG. 8 to 12 are diagrams illustrating the separation of lines and
characters by recognizer shown in FIG. 2;
FIG. 13 to 17 are diagrams illustrating dispersion of characteristics of
address characters; and
FIG. 18 is a diagrammatical view of the recognizer detector shown in FIG. 7
.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An embodiment of the mail address processing machine according to the
present invention will be described below with reference to the attached
drawings.
FIG. 2 is a diagrammatical view of a mail processing machine 8 which reads
a ZIP code and an address written on each piece of mail, discriminates
whether the address characters are printed or handwritten, cancels the
stamp, and sorts the mail into a first group of mail having printed
addresses and a second group of mail having handwritten addresses. The
first group is further sorted automatically by a ZIP code reader, while
the second group is further sorted manually according to ZIP codes.
Mail processing machine 8 shown in FIGS. 2 and 3 comprises an operator
panel 10, a display unit 11, a controller 12, a mail receiver 14, a mail
carrier 16, two stamp detectors 18a and 18b, a non-inversion path 20, an
inversion path 22, a second pair of stamp detectors 24a and 24b, and a
pair of address position detectors 26a and 26b.
The invention thus includes means for detecting the position of a
destination address area which contains the destination address on a piece
of mail. As embodied herein, the detecting means comprises postage stamp
detectors 18a and 18b, non-inversion path 20, inversion path 22, two
postage stamp detectors 24a and 24b, and two address position detectors
26a and 26b.
The invention also includes means for generating signals representative of
characters within the destination address area. As embodied herein, the
generating means includes a branch mechanism 28 and two character
detectors 30a and 30b.
The invention further includes means for calculating the statistical
variation (i.e., the dispersion) of a characteristic of the characters
within the destination address area for comparing the calculated
dispersion to a predetermined limit, and means for selecting the piece of
mail as having a printed address when the dispersion is less than the
predetermined limit. As embodied herein, the calculating, comparing, and
selecting means includes a recognizer 32.
Characters of the address present on mail such as is handled by machine 8
can be described in terms of specific characteristics such as height,
spacing, position above or below a line, pitch, etc. Each of these
characteristics exhibits a certain variation, or dispersion, from an
average. It can be readily appreciated, however, that dispersion of
printed address characters will be less than dispersion for handwritten
characters.
Mail processing machine 8 further includes two stamp cancellers 34a and
34b, and a sorter 36 including several mail sorting boxes 36a to 36e.
A stack of mail is arranged in mail receiver 14. Each piece of mail
arranged in mail receiver 14 is fed one-by-one to postage stamp detectors
18a and 18b in a vertical mail position.
When a postage stamp is attached to a corner of a piece of mail, four
different positions (a), (b), (c) and (d) are possible, as shown in FIG.
4, in which solid lines outlining a stamp indicate that a stamp is
attached on the front surface side of a piece of mail, and dashed lines
indicate that a stamp is attached on the back surface side of a piece of
mail. Here, stamp detectors 18a and 18b are arranged to detect the stamp
only when the stamp is located at the lower ends of the mail as depicted
by (a) and (b) in FIG. 1, respectively. That is, the stamp attached as at
(a) in FIG. 4 can be detected by stamp detector 18a, and that attached at
(b) in FIG. 4 can be detected by stamp detector 18b. When a stamp is
detected as depicted at (a) or (b) in FIG. 4, the mail is fed through a
non-inversion path 20. However, when detectors 18a and 18b cannot detect
the presence of a stamp, the stamp may be located at the upper ends of the
mail, as depicted by (c) and (d) in FIG. 4, or the piece of mail may have
no stamp. In this case, the mail is fed through an inversion path 22 to
reverse the mail upside down so that the stamp is always positioned as
shown by (a) or (b) in FIG. 4. In more detail, when the stamp is located
as (c) and reversed, the piece of mail becomes positioned as at (a); when
the stamp is located as at (d) and reversed, the piece of mail becomes
positioned as at (b) in FIG. 4.
The mail arranged with the stamp located on the lower side thereof is then
fed to the next two stamp detectors 24a and 24b to detect the presence or
absence of the stamp. Therefore, when stamp detector 24a or 24b detects
the presence of a stamp, it is possible to determine that the address is
written on the side on which at least one stamp is affixed.
The address position detector 26a or 26b detects the address character
position on the front surface of a piece of mail on which an address is
written, on the basis of mail surface information. That is, when the
presence of a stamp is detected by stamp detector 24a or 24b, address
position detector 26a or 26b next detects the presence of an address
window covered by cellophane or an address label on which an address is
written, in order to detect a mail address area where a destination
address is written. When the presence of a stamp is not detected by either
stamp detector 24a or 24b, the quantity or the extent of characters
written on one surface of the piece of mail is compared with that on the
other surface of the same piece of mail by address position detectors 26a
and 26b in order to determine the front or back surface of the mail. That
is, the surface on which the most characters are written is determined to
be the front surface of the mail.
On the basis of the detected window or label position and the quantity of
characters, it is possible to detect the front side or back side of the
mail and the address position or area where an address is written. Thus,
even when stamp detector 24a and 24b cannot detect the presence of a
postage stamp, the front surface of the mail is determined on the basis of
the address window by address position detectors 26a and 26b. The quantity
of the address characters can be determined by integrating the image
signals indicative of address characters.
When address position detector 26a detects the front of the piece of mail,
branch mechanism 28 is actuated so that the mail fed to character detector
30a. On the other hand, when address position detector 26b detects the
front of a piece of mail, branch mechanism 28 is actuated so that the mail
is fed to character detector 30b.
As shown in more detail in FIG. 5, address position detectors 26a and 26b
each comprise a light source 262 for emitting a light beam toward a piece
of mail fed through a carrying path for scanning, a lens 264 for focusing
the light scattered by the mail, a photosensitive element 266 composed of
a line image sensor (e.g. a charge coupled device) for detecting
characters written on the mail, an amplifier 268 for producing a detected
character image signal S, and two quantization circuits 270A and 270B.
Light source 262 and lens 264 are both disposed relative to the mail in
such a way that the incidence angle a is roughly equal to the reflection
angle b. Quantization circuit 270A compares the image signal S detected by
photosensitive element 266 with a reference level B outputted from a
controller (not shown in FIG. 5), and outputs a high level signal, called
a window/label signal (W/L SIG), indicative of the presence of a window or
label having a high reflectivity when the level of image signal S exceeds
the reference level B as shown by image signal Sc in FIG. 6.
Quantization circuit 270B compares image signal S with a reference level C
also outputted from a controller (not shown in FIG. 5) and outputs a
character signal (CHR SIG) at a low level when the level of the image
signal S lies between the reference B and C, that is, when the paper
surface exhibits a middle reflectivity. This is indicated in FIG. 6 by the
portion of image signal S designated by S.sub.B. A low level of CHR SIG is
indicative of the absence of characters.
Further, when the level of image signal S lies between reference levels C
and A, that is, when the paper surface exhibits a low level reflectivity,
the quantization circuit 270B outputs a high level CHR SIG which is
indicative of the presence of characters.
In FIG. 6, reference level A corresponds to the level of image signal S
which is generated when the surface being monitored is deep black.
In address position detector 26a or 26b, the resolving power of scanning is
not high (e.g., a single scanning line per millimeter) because this
detector detects only the position of an address window/label. The
window/label position can be detected in the form of (x, y) coordinates
indicative of the number of the horizontal scanning line from an upper
edge and a time period from the beginning of scanning of the horizontal
scanning line, for instance.
When no postage stamp and no address window/label are detected, a low level
character signal CHR SIG outputted from quantization circuit 270B is
integrated by an integrator 272 and supplied to a comparator 274. However,
a high level CHR SIG is not integrated.
Another character signal CHR SIG' outputted from another quantization
circuit corresponding to address position detector 26b is integrated by an
integrator 272' and also supplied to the comparator 274. Comparator 274
compares these two integrals of character signals to determine the front
side of a piece of mail where an address is supposed to be written. For
instance, if the number of character signals integrated by integrator 272
is larger than the number integrated by integrator 272', comparator 274
generates a command signal to branch mechanism 28 to feed the mail toward
character detector 30a. In response to this command signal, character
detector 30a is activated to detect the character image.
FIG. 7 shows character detectors 30a and 30b and recognizer 32. Each
character detector 30a or 30b comprises a fine scanner 302a or 302b and a
quantization circuit 304a or 304b. Fine scanner 302a or 302b generates
image signals in almost the same way as address position detector 26a or
26b by irradiating the mail surface with a light beam and transducing the
reflected light beam (not the scattered light beam) by photosensitive
elements into image signals. However, the resolving power of the fine
scanner 302a or 302b is as high as 8 lines per millimeter because this
detector detects the features of characters.
Quantization circuit 304a or 304b compares the detected mail surface image
signals with a predetermined reference level and outputs character image
signals only when the image signal drops below a reference level (the
above processing being referred to as binarization).
Recognizer 32 comprises an image memory 322, an address position detector
324, a line detector 326, a parameter extractor 328, and a discriminator
330.
Image memory 322 stores all the scanned and binarized character image
signals detected by one of character detectors 30a or 30b because the
front surface of a piece of mail has been detected by address position
detectors 26a and 26b. The detected mail is fed to one of character
detectors 30a and 30b. Therefore, image memory 322 stores the character
image signals corresponding to the detected front surface of a piece of
mail that are detected by either character detector 30a or 30b.
Line detector 326 functions as follows. The preceeding processing
operations have already detected an address position or area where an
address is written. Therefore, in this step, character lines are further
detected from the detected address area. That is, since an area where
characters are gathered has already been determined, the succeeding step
determines how the character area is arranged within the detected address
area. Line detector 326 reads image memory 322, which stores a plurality
of signals in order of scanning, as shown by dotted lines in FIG. 9. The
direction of the dotted lines is called direction X, and the direction
perpendicular to direction X is called direction Y. The surface of the
piece of mail is described according to X,Y coordinates.
By doing this, the number of character image signals are counted along the
conveying direction X in order to obtain a histogram, as shown in FIG. 8.
By detecting the minimum of the histogram indicative of the distribution
of the character image signals, it is possible to separate each of the
address lines so that the position number of the coordinates is obtained.
Parameter extractor 328 detects character feature parameters. These
parameters are dispersions of various character features such as (1)
character height; (2) character lower edge position; (3) character width;
(4) character pitch; (7) leftmost character position; (8) line spacing,
etc.
To obtain character feature parameters, each character area is separated
within a line in an address area. In more detail with reference to FIG. 9,
the number of image signals are counted along a direction Y perpendicular
to an address line. By detecting the minimum of the histogram indicative
of the distribution of the image signals, it is possible to separate each
of the characters so that the position number of the coordinate is
obtained. It is possible to locate each character with the position
numbers of the ordinate and abscissa, as shown in FIG. 10.
For example, as shown in FIG. 12, an address area 4D1 is specified by
address position detectors 26a, 26b as an area with the upper leftmost
position A and a lower rightmost position (not shown). The location of a
particular character is specified with the upper left position and the
lower rightmost position based on a coordinate system with reference to A.
The character area for character a is specified with the coordinates
(a.sub.x1, y.sub.1) and (a.sub.x2, y.sub.2),
The dispersion .sigma..sub.L.sup.2 of character features is calculated
according to the following formula:
.sigma..sub.L.sup.2 =1/N (X.sub.Li -X.sub.Li).sup.2
Where:
N=the number of characters;
L=the character feature such as height, lower edge position, width, pitch,
area, line arrangement slope, leftmost position, line spacing, etc.
X.sub.Li =the value of the character feature of each character.
X.sub.Li =the average value of the character feature of characters.
Generally speaking, .sigma..sub.L.sup.2 is larger for handwritten
characters than that for printed characters. FIG. 13 shows an example of
the dispersion of character height .sigma..sub.H.sup.2 in printing and in
handwriting. FIGS. 13-17 respectively show examples of dispersion of
character lower edge, character width, character pitch, and the character
area.
When calculating these feature parameters, all of the position numbers for
the characters are generally used. However, calculations of such
dispersion values is a burden for a processor (CPU). Such calculations
require long calculation times, a high-speed processor, or both.
In a preferred embodiment, parameter extractor 328 may detect character
parameters on the basis of signals from a limited or restricted area
within the address area. In the preferred embodiment, the restricted area
is the lower two lines of the address area, an area containing important
information about the destination address.
A reference threshold value .sigma..sub.O.sup.2 for the dispersion of each
of the character features is previously determined. Each actual dispersion
value .sigma..sub.L.sup.2 calculated using image signals read from image
memory 322 is compared with this reference threshold value
.sigma..sub.O.sup.2 . The compared result (the difference between the
actual dispersion and the reference dispersion) is stored in the image
memory 322 and added in sequence to obtain a sum total of the differences
between two of the above-mentioned eight character features. When
discriminator 330 determines that the sum total of the dispersion
differences between the actual values and the reference values exceeds a
predetermined value, the characters are designated as handwritten. In
contrast, when discriminator 330 determines that the sum total of the
dispersion differences is less than the predetermined value, the
characters are designated as printed.
FIG. 18 is a block diagram showing address position detector 324, which
comprises a W/L signal detector 3242, a compressor 3244, and an address
area detector 3246. When W/L signal detector 3242 detects the presence of
a W/L signal indicative of a window/label position (x-y coordinates),
image data corresponding to only the window/label position from the image
memory 322 is supplied to line detector 326.
When the W/L signal detector 3242 detects an absence of the W/L signal,
compressor 3244 reads all of the image signals from image memory 322 for
compression. For example, the resolving power of the image signals may be
reduced from 8 lines per millipower meter to 1 line per millimeter by
simply averaging eight horizontal scanning line signal levels. The address
area detector 3246 compares the averaged signal levels with a reference
level for binarization in the same manner as quantization circuit 270, and
determines an address character area on the basis of the binarized
character image signals collected at an area on the front surface of a
piece of mail. When this address character area has been detected, the
image data corresponding to only the determined address character area is
supplied to line detector 326.
When stamp detector 24a or 24b detects the presence of a postage stamp on
the piece of mail, a stamp canceller 34a or 34b corresponding to the stamp
detector 24a and 24b impresses a mark on the detected postage stamp. The
mail thus detected is sorted and put into five sorting boxes 36a to 36e in
such a way that: mail having an address written in print and detected by
character detector 30a is arranged in box 36a, mail having an address
written in handwriting and detected by character detector 30a area is
arranged in box 36b, mail having an address written in print and detected
by character detector 30b is arranged in box 36c, mail having an address
written in handwriting and detected by character detector 30b area
arranged in box 36d, and other mail determined to be rejected is arranged
in box 36e.
In the machine of the present invention, it should be noted that since
address position detectors 26a or 26b can detect a window/label position
and the front side of the mail (by comparing the quantity of characters),
and further, since address position detector 324 can determine an address
character area, character images corresponding to only the front surface
of the mail and only to the address position (window or label) or address
character area can be read from the image memory 322 for discrimination.
Therefore, character image data to be analyzed is not voluminous, making
it possible to increase mail processing speed and decrease the cost of the
machine by providing only a single recognizer 32 including discriminator
330.
The operation of the mail processing machine of the present invention for a
piece of mail P as shown FIG. 1 will now be described with reference to
FIG. 2.
Mail P is arranged in receiver 14 and fed to stamp detectors 18a and 18b by
carrier 16 in a vertically arranged position. When stamp detectors 18a or
18b detect the presence of a stamp attached to the lower side of the mail,
the mail is fed through the non-inversion path 20. When stamp detectors
18a and/or 18b detect the absence of a stamp, the mail is fed through
inversion path 22. Thereafter, stamp detector 24a and 24b detect the
presence or absence of a stamp, and generate a stamp presence signal which
is applied to stamp canceller 34a or 34b to impress a mark on the stamp of
the mail just before sorting the mail.
When no stamp is detected by stamp detectors 24a and 24b, the front side of
the mail (on which an address is written) is detected by address detectors
26a and 26b.
Address position (surface information) detector 26a or 26b also detects the
position of a window or a label. In this process, when address position
detector 26a detects a mail front, branch mechanism 28 is actuated so that
the mail is fed to character detector 30a. When address position detector
26b detects a mail front, branch mechanism 28 is actuated so that the mail
is fed to character detector 30b.
Since the front surface of a piece of mail has been detected by address
position detectors 26a and 26b, the detected mail is fed to either
character detector 30a or 30b. Character detector 30a or 30b detects
characters on the front surface of the mail by scanning and quantization.
The detected character image signals corresponding to the address position
signals (window/label signal) are supplied from image memory 322 (FIG. 7)
to line detector 326 on the basis of the window/label signal detected by
address position detector 26a or 26b.
The character features (e.g., arrangement order, regularity, size, density,
etc.) of the character images are detected by parameter extractor 328 of
recognizer 32 and discriminated as to printed mail or handwritten mail by
comparing the extracted character features with stored reference character
values.
For a piece of mail P for which no window/label signal is detected, address
position detector 324 determines an address area by compressing all of the
surface image signals and binarizing the compressed signals.
The process of separating each of the lines of characters is done for the
signals of the destination address. Thus, the signals are separated into
many groups of signals corresponding to lines. As mentioned above, the
signals corresponding to a line are separated into a group of signals
corresponding to each character. In the preferred embodiment, signals
corresponding to only the two bottom lines are used in discrimination.
After compression, signals exceeding the threshold value may indicate the
existence of several groups of signals. These groups of signals may come
from the destination address, a sender address, an advertisement, and so
on. For mail P, there are two areas of signals. Since the destination
address is normally to the right of the return address when there is a
stamp on the right-upper corner of a piece of mail, and since it is known
that there is a stamp on the right-upper side of the mail P in FIG. 1, it
is determined that the right hand area is the destination address.
The mail thus discriminated is sorted into one of the sorting boxes 36a to
36e.
In the above description, the mail processing machine of the present
invention has been disclosed with reference to block diagrams (i.e., a
hardware configuration). In practice, mail processing machine 8 is
controlled by controller 12 provided with a ROM, a RAM, a display unit,
and a keyboard (not shown).
As described above, in the mail processing machine of the present
invention, since the surface information (window or label position,
quantity of characters, character block position) is first detected and
then used to analyze only a portion of the character image signals to
determine whether the address characters are in printing or handwriting,
it is possible to improve the sorting speed of the mail, while reducing
the cost of the machine.
It will be apparent to those skilled in the art that various modifications
and variations ca be made in the apparatus and methods of this invention
without departing from the spirit or scope of the present invention. The
present invention covers such modifications and variations which are
within the scope of the appended claims and their equivalents.
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