Image analysis – Applications – Mail processing
Reexamination Certificate
1998-09-11
2002-07-16
Boudreau, Leo (Department: 2721)
Image analysis
Applications
Mail processing
C382S100000, C356S613000
Reexamination Certificate
active
06421451
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a step difference detection apparatus used as, e.g., an apparatus for detecting the position and area of the address label or address indication cellophane window (address window) of mail, and a processing apparatus using the same.
Conventionally, to detect the region of an address label on the upper surface of a letter of, e.g., a mail envelope, the image on the upper surface of the mail item is simply sensed, and a rectangular region having an appropriate size and position, which appears to be an address label, is detected.
This method is effective to some degree but is influenced when letters have address labels and upper surfaces in the same color, or letters have label-like pictures on the upper surfaces.
Conventionally, to detect an address window (a window portion covered with a transparent sheet optically having a high reflection ratio, e.g., a cellophane or paraffine sheet), the positive reflected light component of illumination light is detected.
An example is disclosed in Jpn. Pat. Appln. KOKOKU Publication No. 58-45305 (Japanese Patent No. 1377041). This method is exclusively used to detect an address window. Address label detection must be performed using another method.
In addition, several step difference/unevenness detection methods applicable to detect an address label or an address window are conventionally known. As the first method, a shadow or scattered light due to a stepped edge is read by oblique illumination.
FIG. 1
shows an arrangement for reading the step difference on the upper surface of a letter by simple oblique illumination. This arrangement is incorporated in a culler facer canceller for automatically facing and canceling a lot of letters including mail envelopes and aims to detect the flap of a letter (folded seal portion of mail) for discrimination between the upper and lower surfaces of the letter. A similar arrangement is disclosed in Jpn. Pat. Appln. KOKOKU Publication No. 5-7750.
As shown in
FIG. 1
, a light beam emitted from a halogen lamp
1
is collimated by a collimator lens
2
to obliquely irradiate a letter
3
at a large incident angle (the incident angle means the angle formed by the normal and the incident light beam).
An image sensing means constituted by an image sensing lens (camera lens)
4
and a CCD sensor
5
senses the image of the letter from the vertical direction to detect a shadow
6
generated at the step portion, thereby detecting the position of the step difference of the flap.
However, the method of detecting the shadow or scattered light by simple oblique illumination may be influenced by the printed contents on the upper surface of the letter. For example, when a black straight line is printed on the upper surface of the letter, the output obtained upon reading this line can hardly be discriminated from that obtained by reading the edge of the address label on the upper surface of the letter or that obtained by reading the flap on the lower surface of the letter.
Another representative step difference detection apparatus using oblique illumination is SERRATION READER BML3D, shown in
FIG. 2
, available from SCHRACK in Australia. This is an edge detection apparatus exclusively used for stamps.
As shown in
FIG. 2
, in this apparatus, illumination light containing parallel light components obliquely illuminates a linear region on a surface with a stamp at a large incident angle. This region is read by a line image sensor. The read region (CCD AREA in
FIG. 2
) of the line image sensor is almost parallel to the longitudinal side of the stamp.
A portion corresponding to each punch hole of the perforation generates a shadow on the upper side of the hole due to the oblique illumination effect while the lower side of the hole scatters the illumination light and becomes bright. By reading this region, a signal having a period corresponding to the interval of the perforations of the stamp is obtained.
When this signal is collated with a predetermined reference pattern, the perforated edge of the stamp is detected. This method utilizes, at maximum, the fact that a stamp has notches of perforations, thereby improving the detection reliability. For this reason, this method cannot be applied to an address label having straight sides.
As still another surface unevenness detection method, triangulation shown in
FIG. 3
is known.
FIG. 3
is quoted from “Handbook of Applied Opto-electronics”, Shoko-sha (1989). In
FIG. 3
, the point to be measured is irradiated with a laser beam emitted from a semiconductor laser light source
7
to obliquely observe the spot.
The spot forms an image on a position sensor
9
through an imaging lens
8
. The position of the spot image on the position sensor changes depending on the height of the point to be measured. Therefore, when the change in spot image position is detected, the height of the point to be measured can be detected. Visible laser displacement sensors of LB-1000 series (LB-1000/LB-040) available from KEYENCE use this technique.
In this technique, only one point is measured in one measurement operation. To measure the unevenness of a region with a two-dimensional extent, like an address label, detection devices need be arrayed, and the letter must be carried under the array of detection devices. Since limitations are imposed on size reduction of individual sensors, this technique is disadvantageous in resolution power or cost.
As described above, in the conventional address label and address window detection apparatus or step difference detection apparatus using oblique illumination, a change in reflection ratio distribution due to printed contents on the upper surface of a letter or a background design influences the step difference reading result, so the step position cannot be properly detected.
In addition, the stamp edge detection method or unevenness detection based on triangulation cannot be directly applied to detect unevenness of a region having a two-dimensional extent and straight edges as in an address label.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above situation, and has as its object to provide a step difference detection apparatus capable of minimizing the influence of the reflection ratio distribution on a measuring surface due to printed contents on the upper surface of a letter and highly precisely detecting the position of an address label or an address window on the upper surface of the letter, and a processing apparatus using the same.
In order to achieve the above object, according to the first aspect of the present invention, there is provided a step difference detection apparatus comprising:
illumination means for emitting illumination light;
incident means for making the illumination light emitted by the illumination means be incident on a plurality of small illumination regions on an object carried in a predetermined carrier direction from different directions;
image sensing means for inputting an image of the regions on the object illuminated with the illumination light which is made to be incident by the incident means; and
detection means for detecting a step difference on the object on the basis of the image sensed by the image sensing means.
In the step difference detection apparatus of the present invention, the object surface is divided into a plurality of small illumination regions each comprising a two-dimensional region, and adjacent small illumination regions are illuminated with illumination light from different directions, respectively.
By obtaining the image of the object comprising the small illumination regions using an image sensor or the like, the position of the step difference can be detected while almost eliminating the influence of the background design of the letter such as mail as the object.
For example, when a letter with an address label is illuminated obliquely with a collimated beam, a dark line or a bright line is formed at a stepped portion of the address label in accordance with the direction of the stepped
Honguh Yoshinori
Saito Tutomu
Shimura Kei
Shiratsuchi Masataka
Boudreau Leo
Choobin M B
Kabushiki Kaisha Toshiba
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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