Method and apparatus for the reading of a bar code

Claim 1

A method of reading a bar code consisting of a predetermined number of code elements for generation of a binary signal with sequential high and low phases, the lengths of which correspond to the width of the sequential code elements, the method comprising: sensing the code elements by one or more sensing beams of a bar code reader along scanning lines extending substantially parallel to one another, wherein each region of a code element sensed by a scanning line forms a code element section; detecting, for substantially each scanning line, those codes segments that consist of a code element section or a plurality of sequential code element sections, which are recognized as permissible code segments on the basis of preset decision criteria; finding in each case a reference code element from mutually associated code element sections, each representing the same code element of the bar code for different scanning lines; storing detected permissible code segments in an image memory; after the detection and storing of the permissible code segments, freeing of distortion the segmented image of the bar code deposited in the image memory for allowing the forming of the reference code element; determining a shift between code elements detected for two adjacent scanning lines; shifting each code segment stored for a certain scanning line within the image memory by such an element of said shift that corresponds to the distance of said certain scanning line from said two adjacent scanning lines; and producing the binary signal from the reference code elements.

Claim 2

A method of reading a bar code consisting of a predetermined number of code elements for generation of a binary signal with sequential high and low phases, the lengths of which correspond to the width of the sequential code elements, the method comprising: sensing the code elements by one or more sensing beams of a bar code reader along scanning lines extending substantially parallel to one another, wherein each region of a code element sensed by a scanning line forms a code element section; detecting, for substantially each scanning line, those codes segments that consist of a code element section or a plurality of sequential code element sections, which are recognized as permissible code segments on the basis of preset decision criteria; finding in each case a reference code element from mutually associated code element sections, each representing the same code element of the bar code for different scanning lines; storing detected permissible code segments in an image memory; after the detection and storing of the permissible code segments, freeing of distortion the segmented image of the bar code deposited in the image memory for allowing the forming of the reference code element; determining a shift between code elements detected for two adjacent scanning lines; shifting each code segment stored for a certain scanning line within the image memory by such an element of said shift that corresponds to the distance of said certain scanning line from said two adjacent scanning lines; and producing the binary signal from the reference code elements.

Claim 32

An apparatus for reading a bar code consisting of a predetermined number of code elements for the generation of a binary signal with sequential high and low phases, the lengths of which correspond to the width of sequential code elements, in particular with a reading direction extending obliquely to the code elements wherein a bar code reader which transmits one or more scanning beams for the sensing of the code elements along scanning lines extending substantially parallel to one another, wherein each region of the code element sensed by a scanning line forms a code element section, a code segment selection means is provided for the determination of permissible code segments as a result of predetermined decision criteria and consisting of one code element section, or of a plurality of sequential code element sections, a code segment detection means is provided for the detection of the code segments recognized as permissible by the code segment selection means for substantially each scanning line, by a reference code element determining means for determining in each case a reference code element for respective, mutually associated code element sections representing the same code element of the bar code and detected for different scanning lines, an image memory for storing the detected, permissible code segments, a shift determining means for determining the shift between two code segments detected for two adjacent scanning lines and stored in the image memory, a code segment shifting means for shifting within the image memory a code segment stored in the image memory for a certain scanning line by such a multiple of said shift which corresponds to the distance between said certain scanning line from said two adjacent scanning lines, and a signal generating means is provided for the generation of the binary signal from the reference code elements.

Claim 33

An apparatus for reading a bar code consisting of a predetermined number of code elements for the generation of a binary signal with sequential high and low phases, the lengths of which correspond to the width of sequential code elements, in particular with a reading direction extending obliquely to the code elements wherein a bar code reader which transmits one or more scanning beams for the sensing of the code elements along scanning lines extending substantially parallel to one another, wherein each region of the code element sensed by a scanning line forms a code element section, a code segment selection means is provided for the determination of permissible code segments as a result of predetermined decision criteria and consisting of one code element section, or of a plurality of sequential code element sections, a code segment detection means is provided for the detection of the code segments recognized as permissible by the code segment selection means for substantially each scanning line, by a reference code element determining means for determining in each case a reference code element for respective, mutually associated code element sections representing the same code element of the bar code and detected for different scanning lines, an image memory for storing the detected, permissible code segments, a shift determining means for determining the shift between two code segments detected for two adjacent scanning lines and stored in the image memory, a code segment shifting means for shifting within the image memory a code segment stored in the image memory for a certain scanning line by such a multiple of said shift which corresponds to the distance between said certain scanning line from said two adjacent scanning lines, and a signal generating means is provided for the generation of the binary signal from the reference code elements.

Claim 34

A method of reading a bar code consisting of a predetermined number of code elements for generation of a binary signal with sequential high and low phases, the lengths of which correspond to the width of the sequential code elements, the method comprising: sensing the code elements by one or more sensing beams of a bar code reader along scanning lines extending substantially parallel to one another, wherein each region of a code element sensed by a scanning line forms a code element section; detecting, for substantially each scanning line, those codes segments that consist of a code element section or a plurality of sequential code element sections, which are recognized as permissible code segments on the basis of preset decision criteria; finding in each case a reference code element from mutually associated code element sections, each representing the same code element of the bar code for different scanning lines; carrying out a two-dimensional Fourier transform of the detected code segments and determining the maximum amplitudes of the spectrum of magnitude that is found; determining the tilt angle between the scanning direction and the direction perpendicular to the bar orientation of the bar code from the position of the maximum amplitudes; calculating the shift between the code element sections respectively detected for different scanning lines from the tilt angle; compensating the shift; and producing the binary signal from the reference code elements.

Claim 35

A method of reading a bar code consisting of a predetermined number of code elements for generation of a binary signal with sequential high and low phases, the lengths of which correspond to the width of the sequential code elements, the method comprising: sensing the code elements by one or more sensing beams of a bar code reader along scanning lines extending substantially parallel to one another, wherein each region of a code element sensed by a scanning line forms a code element section; detecting, for substantially each scanning line, those codes segments that consist of a code element section or a plurality of sequential code element sections, which are recognized as permissible code segments on the basis of preset decision criteria; finding in each case a reference code element from mutually associated code element sections, each representing the same code element of the bar code for different scanning lines; carrying out a two-dimensional Fourier transform of the detected code segments and determining the maximum amplitudes of the spectrum of magnitude that is found; determining the tilt angle between the scanning direction and the direction perpendicular to the bar orientation of the bar code from the position of the maximum amplitudes; calculating the shift between the code element sections respectively detected for different scanning lines from the tilt angle; compensating the shift; and producing the binary signal from the reference code elements.