Image analysis – Applications – Mail processing
Reexamination Certificate
1999-03-19
2001-11-06
Johns, Andrew W. (Department: 2621)
Image analysis
Applications
Mail processing
Reexamination Certificate
active
06314193
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for localizing and detecting plastic strips and/or window areas on mail. In particular, the invention relates to a localization method of this kind for large-format envelopes and parcels. The invention also relates to a device for implementing such a method.
BACKGROUND TO THE INVENTION
Mail sorting equipment is in widespread use today. Automated location and detection of addresses on standard envelopes at high throughput rates has long been mastered. In the field of large-format envelopes and parcels (e.g. DIN A4, B4) too there has recently been a development with regard to automated address detection (cf. DE-C-195 32 842).
However, the proportion of such mail being sent vacuum sealed in plastic sheet is steadily increasing. Consequently, the detection of mail enclosed entirely in plastic sheeting or of mail with plastic strip areas—such as a plastic-sheeted window in a standard paper envelope or a label mounted on a plastic strip—is becoming more and more important.
Precise detection of plastic strips and/or areas of plastic is important for the following reasons:
The result of the read operation is often imprinted on the envelope as a barcode. Such barcodes cannot be affixed directly to the plastic, however, as there is a risk of their being blurred. A special label must therefore be affixed to the mail, resulting in additional cost which is avoidable on paper envelopes.
On the other hand, if a label of the said kind and its position on a plastic covering can be localized, the position of the recipient's address or barcode is thereby automatically identified.
The same applies where it is possible to detect a window and its position on a standard paper envelope.
STATE OF THE ART
All currently known plastic strip/window detectors use the amplified total reflection of light on plastic strips and/or the ability of those materials to polarize light when the light is radiated and received at a preferred angle (Brewster angle). In this, the light sender and receiver are arranged perpendicular to the direction of movement of the mail along a line over its entire height. The received light is spatially allocated to the position of the individual sender or receiver and evaluated:
Thus, for example, DE-A-195 35 038 discloses a device and method to detect a label/window position, wherein light-emitting elements illuminate the object conveyed by a conveyor device.
A lens generates an image of the said object, wherein linear image converters convert the image light striking the lens into image signals. Then the image signals are converted by binary conversion into monochrome binary image signals, and on the basis of those binary image signals a label/window position is determined with the aid of a coordinates computation unit.
In DE-C-42 22 908 a device is disclosed which scans the label edges based on a shadowing effect when the mail is illuminated from different directions. In this, the label must lie essentially parallel to the surface of the mail, and be vertically raised or lowered.
Finally, U.S. Pat. No. 4,845,761 discloses a system for determining possible address information, including a light source and detectors to detect the reflection from the mail. The light source consists of a large number of photoemitters (for example light-emitting diodes), of which the reflection is detected by photodetectors (for example phototransistors). Also, a polarizer is used to improve the so-called “specular-to-diffuse” ratio.
Since the light reflected from a specific position of an object (envelope etc.) covers a certain solid angle (approx. 3/100 sr), correct allocation of a received signal with a desired resolution to the location-from which it is reflected is only possible if the sending and receiving elements are mounted so close to the surface of the object being detected that the possibility of overlap of the corresponding light cones of adjacent parts of the object is excluded (a light cone in this context should be understood as being the envelope of all angles into which light is reflected).
Thus, for example, at a desired positional resolution of 5 mm the distance must not be greater than 2-3 cm.
These detectors have the disadvantage that they are heavily contaminated by dust from abrasion of the mail, and so need to be cleaned very frequently. Above all, they incur the risk that plastic strips and window areas will not be detected. Furthermore, these detectors are practically unusable for parcel surfaces, as they have differing heights (mechanical tracking problem) and are very uneven.
It is therefore the object of the present invention to deliver a method and device which permit precise identification of plastic strips and plastic-sheeted window areas, at the same time prevent dust contamination of the arrangement, and also allow the range of applications of such detectors to be expanded to include parcel surfaces.
This and other objects are fulfilled by the method in accordance with claim
1
and the device in accordance with claim
6
. Further advantageous embodiments of the inventions are presented in the sub-claims.
The method in accordance with the invent ion offers the advantage that between the sender and receiver and the object being examined a large distance can be ensured, limited only by the aperture. To be able to receive as much light as possible with as little apparatus as possible, it is beneficial—but not limiting—to select a distance from the receiver to the detected object of approximately 30-50 cm. The distance from the sender to the detected object may without any problem be set longer (100 cm and more) when using light with greater coherence length (laser).
The method in accordance with the invention can be applied in the detection of plastic strips, inspection windows and paper labels affixed on plastic, as well as for standard and large-format envelopes and parcels. It is not restricted to those applications, however, but can generally be applied wherever the positions of smooth surfaces need to be distinguished from those of rough surfaces. The method in accordance with the invention can also be applied wherever the positions of smooth (but not necessarily entirely flat) surfaces of electrically non-conductive materials need to be distinguished from those of conductive materials, where the special property of the said materials is used for polarization.
For the sake of clarity, however, the invention is detailed in the following based on the drawing in respect only of the problem of detection of plastic strips and inspection windows. The drawing schematically presents a possible arrangement for implementing the method in accordance with the invention.
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August, Esq. Casey P.
International Business Machines - Corporation
Johns Andrew W.
McGinn & Gibb PLLC
Nakhjavan Shervin
LandOfFree
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