Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
2000-08-03
2004-02-10
Lee, Michael G. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S485000, C235S462270, C235S462160, C235S462180, C235S462200
Reexamination Certificate
active
06688524
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for reconstructing a bar code through consecutive scans.
2. Discussion of Prior Art
As already known, bar codes are largely used in the automatic identification of products.
A bar code is made up of a sequence of light and dark areas which are named space- and bar-type elements. These are rectangular-shaped elements, and each of them can have a different amplitude value. The amplitude of the elements is equal to an elementary value called module, or to multiples of it.
A set of elements univocally represents a character of the code, and a set of characters univocally represents a symbol of a particular code (briefly referred to simply as code). For the purpose of facilitating its location and reading, each code is preceded and followed by quiet zones, that is to say, areas without signs, whose colour corresponds to the background colour on which the bars are printed.
Spaces, quiet zones and background are usually white or, in any case, light, whereas the bars are black or, in any case, dark; this is the case which will be referred to in the following description, for simplicity of exposition. However, the contrary is possible, too.
Each code is defined by a series of rules making up the coding and decoding protocol of that particular type of code. Therefore, a certain sequence of characters matching said protocol represents the decoded symbol of the code being read.
Several methods for scanning and decoding the symbol of a bar code are known. A typical method can be schematised as follows: a device for reading bar codes lights up the code to be decoded along a reading line; the diffused light is collected by a photo-sensor element which, in its turn, generates an analogue signal that is proportional to the intensity of the diffused light.
Bar codes are usually examined according to a scan direction which is not coincident with the longitudinal axis of the code; thus, said scan direction usually forms an angle with the longitudinal axis of the bar code. When this angle exceeds a certain value, only a subset of the elements of the code is scanned; thus, the signal relating to said scan is partial, and it does not allow reading the bar code. Having just partial scans, therefore, there is the problem of “reconstructing” a complete scan of the code from said partial scans (or, with an abbreviation largely used in the field, “reconstructing the code”).
In addition, known devices carry out a relative movement between the electro-optical acquisition system of the reader and the objects on which the bar codes are. For example, the electro-optical acquisition system can be of the fixed type, and the objects can be moved, with respect to it, by a movement system, or the reader can be of the portable type, and be moved over the bar codes by an operator.
Other known reconstruction devices are adapted to compose consecutive partial scans, obtained in different positions of the same code, so as to reconstruct and decode the bar code.
Prior-art reconstruction devices may be schematised as in FIG.
2
. They use various algorithms, and they are all based on the composition of the characters or of the code elements.
As shown in
FIG. 2
, the code elements are obtained from the analogue signal, which is obtained by the electro-optical acquisition system, through an operation of digitization. Said digitization essentially consists in squaring the analogue signal, which is reduced to only two values (a high and a low value), and in determining the length of the elements.
The above digitization is a very delicate operation that can generate serious errors in determining the number of elements of the code (by generating errors known as split and merge errors) and in the length of these elements.
For analogue signals affected by faults and distortions such as, for example, blurring, noise and so on, or for reading errors, such as damaged codes or spurious reflexes, the reconstruction and/or the subsequent decoding of the reconstructed code can be compromised.
SUMMARY OF THE INVENTION
Therefore, purpose of the present invention is that of realising a method for reconstructing a bar code through consecutive scans to allow a very precise and reliable reconstruction of the code (for its further decoding) with all types of codes, and in particular, with codes whose signals are affected by faults, distortions and reading errors.
According to the invention, this purpose is achieved by a method for reconstructing a bar code through consecutive scans, said bar code being made up of a plurality of elements having a first and a second reflectivity, characterised in that it comprises the following steps:
a) carrying out at least one scan of the bar code;
b) determining a reconstructed wave form, representative of said at least one scan;
c) carrying out an actual scan of the bar code;
d) determining an actual wave form, representative of said actual scan;
e) aligning said reconstructed and actual wave forms;
f) combining said aligned wave forms by updating said reconstructed wave form with said actual wave form.
Herein and in the following description, the term “scan” refers to the operation of reading a line through the code. Such operation may be carried out in a number of ways, such as for example illumination with a laser scanner, point by point reading through a photodiode (thus, in a temporal sequence), the contemporaneous illumination of the entire line by a LED and simultaneous global reading through a CCD or C-MOS linear sensor (thus, in a spatial sequence).
The term “wave form” refers to the wave form of the analogue signal emitted by the photo-sensor element, possibly processed, but only so that the x-values of the points of the wave form remain directly connected to the temporal or spatial sequence of the different measurement instants or points during a scan.
Differently from the prior art, therefore, the invention can directly operate on the signal of the photo-sensor, before carrying out any digitization of it. This is extremely advantageous because the digitization causes a strong reduction in the information contained in the signal, and said reduction is not recoverable in the following steps. It is also true that usually, the above reduction of information content does not directly hinder the decoding of a bar code, but it has been proved that it can be very disadvantageous during the reconstruction; the reconstruction based on the entire signal is much more precise and reliable for it is based on more information. It must also be taken into account that inaccuracies during the reconstruction often generate errors while decoding.
The aforesaid reconstruction process, with the listed minimum steps from (a) to (f), can be used to combine two or more scans one with another. Preferably, said method is iteratively applied, and thus comprises the following step:
g) iterative repetition of the steps from (c) to (f) until the reconstructed wave form is representative of the entire bar code.
As already said, a very important advantage of the invention is the use of wave forms rich in information content. This information content ensures that it suffices often to use just some properly selected points of the wave forms, and not all of them. In particular, according to a preferred embodiment of the invention, steps (b) and (d) are respectively followed by the following steps:
b′) determining a first series of points on said reconstructed wave form;
d′) determining a second series of points on said actual wave form.
Preferably, said series of points have the same interval, that is to say, each point of the series is separated by an identical distance or by an identical time interval from the following point.
Preferably, the wave forms are analogue, and said series of points are obtained through the sampling of the analogue wave forms.
The number of points provided in each series can be different; preferably, it is of at least 1.5 points for each module of the code to be read. More preferably, it is eq
Bottazzi Marco
Brunelli Elena
Zocca Rinaldo
Datalogic S.p.A.
Lee Michael G.
Nixon & Vanderhye P.C.
Paik Steven S.
LandOfFree
Method for reconstructing a bar code through consecutive scans does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for reconstructing a bar code through consecutive scans, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for reconstructing a bar code through consecutive scans will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3347856