Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
1998-07-30
2001-11-13
Frech, Karl D. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S462200
Reexamination Certificate
active
06315201
ABSTRACT:
The present invention relates to a method of reading a bar code consisting of a predetermined number of code elements for the generation of a binary signal with sequential high-low phases, the lengths of which correspond to the widths of the sequential code elements. Furthermore, the invention is directed to an apparatus for carrying out such a method.
BACKGROUND OF THE INVENTION
Methods of this kind are used together with bar code readers, with the bar code reader transmitting a scanning beam in the direction of the bar code to be detected. The scanning beam is, for example, deflected via a rotating, polygonal mirror wheel, so that the scanning beam is periodically swept through a scanning angle. Through the moving scanning beam a scanning line is projected onto the object carrying the bar code, i.e. onto the bar code.
Most known methods require, for the successful decoding of a bar code, that the scanning beam sweeps over the bar code over its entire length. This condition is, however, no longer satisfied when the bar code to be detected is so tilted relative to the scanning direction that the scanning line projected onto the bar code no longer covers the bar code over its full length. This can, for example, be the case when the bar code is located on an article of luggage which is transported on a conveyor belt. The bar code can in this respect adopt any desired position, so that it is not ensured that a scanning beam sweeping over the object sweeps over the bar code over its full length.
In order to increase the probability of decoding it is thus published German patent application DE-A-107 118 73 that a bar code which is moving obliquely to the scanning direction should be multiply scanned by the same scanning beam, so that different adjacent regions of the bar code are obliquely swept over by the scanning beam as a result of the relative movement between the bar code and the scanning line.
The code segments of the bar code which are respectively detected during this, are combined in an image memory into a complete bar code, with the association of the code element sections respectively forming the same code element of the bar code and detected by the oblique scanning taking place by determining the angle of tilting, the so-called tilt angle, between the scanning direction and the longitudinal direction of the bar code. Once the bar code has been fully built up in the image memory, it is decoded with conventional methods.
All these methods have the common feature that for a successful detection and decoding of the bar code the latter is swept over by a scanning beam of a single bar code reader either in one passage, or, with oblique scanning, in a plurality of directly sequential passages along parallel scanning lines.
A problem exists in that bar codes which are not completely readable from the direction of the bar code reader cannot be fully detected and are thus not decodable with this method, for example due to a partial obscuring of the bar code, because of a bent or kinked bar code, because of an unfavorable reading angle, or because of a partly destroyed bar code.
BRIEF SUMMARY OF THE INVENTION
It is thus an object of the invention to design a method of the initially named kind in such a way that the detection and decoding probability is further increased even in the above-named problematic cases. Furthermore, an apparatus should be set forth for carrying out such a method.
The object with regard to the method is satisfied, starting from the method of the initially named kind, in accordance with the invention in that the bar code is sensed by at least two scanning beams from different directions along different scanning lines, in that at least some of the regions of the bar code scanned by a scanning beam are respectively detected as a code segment, and in that at least some of the detected code segments are selected with respect to predetermined decision criteria and combined for the reconstruction of the scanned bar code.
An apparatus formed in accordance with the invention is comprised by at least two bar code readers which transmit one or more scanning beams in different directions along different scanning lines for the scanning of the bar code, by a code segment detection unit for detecting at least some of the regions of the bar code scanned by a scanning beam as a respective code segment, and by a central evaluation unit for checking predetermined decision criteria for at least some of the detected code segments and for the selection and combination of some of the checked code segments for the reconstruction of the scanned bar code in dependence on the result of the check.
Thus, the problem that the bar code is not fully swept over by one scanning beam, be it in one or more scans, is solved in accordance with the invention in that a plurality of scanning beams sweep over the object bearing the bar code from different directions along different scanning lines. If the bar code cannot be swept over by the corresponding scanning beam from one direction, i.e. along its longitudinal axis, or in several parts oblique to its longitudinal axis, then the possibility exists that the part of the bar code which could not be swept over, can be swept over from a different direction by one of the other scanning beams.
Since it is possible that a plurality of different bar codes are present on the object carrying the bar code, the detected code segments are checked with respect to predetermined decision criteria to see whether they represent segments of the same bar code so that only code segments which belong together are combined for the reconstruction of the scanned bar code. The thus completely detected bar code can subsequently be decoded by customary methods.
It is basically also possible for the same bar code to be multiply present on the object, for example for reasons of redundancy. In this case it is possible, with the method of the invention, to combine one code segment or several code segments of the scanned bar code with one or more code segments of another scanned bar code bearing the same information in order, in this manner, to reconstruct the full bar code present at different points of the object.
In accordance with another advantageous embodiment of the invention, scanning beams are transmitted from different bar code readers, in particular from bar code readers which are spatially separated from one another. In this embodiment a plurality of bar code readers can be so arranged in the room that a detection of the bar code takes place from essentially all relevant directions. In this manner all possible orientations of the bar code are covered, so that each region of the bar code can be swept over by at least one of the scanning beams of the bar code reader.
It is, however, also possible for the scanning beams to be produced and transmitted from one bar code reader, for example by division and/deflection of a scanning beam. Through the special design of a bar code reader, in which a scanning beam is, for example, divided via one or more semipermeable mirrors into a plurality of scanning beams, the number of the bar code readers required can be reduced. However, a bar code reader of this kind is, on the one hand, more complicated to manufacture and, on the other hand, the adjustment of such a bar code reader and any possibly required deflection devices are difficult in practice.
In a further preferred embodiment, the detected code segments are supplied to a central evaluation unit, through which the decision criteria are checked. The code segments selected as a result of the check are combined. In this arrangement one of the bar code readers can be used as the evaluation unit or a unit formed separately from the bar code readers can be used as the evaluation unit.
Through the central evaluation unit the code segments detected by the different bar code readers can be checked to see whether they are parts of the same bar code in accordance with the predetermined decision criteria. A complicated communication and synchronization between different evaluation un
Hippenmeyer Heinrich
Reichenbach Jurgen
Frech Karl D.
Sick AG
Townsend and Townsend / and Crew LLP
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