US 6,332,574 B1 · Method of reading bar code

Abstract

A method of reading a bar code having guard bars at both sides thereof without fail even if the bar code image is highly distorted. An image region taken in by a CCD camera is scanned in horizontal and/or vertical directions to find out a first guard bar in the bar code. Then, a first scanning line for reading the bar code is set in a direction perpendicular to the first guard bar. The bar code is scanned along the first scanning line. If the first scanning line goes out of the bar code region, the first scanning line is traced back to a bar which is last read. Another scanning line starting from the last read bar and extending perpendicularly thereto is set to read the rest of the bar code. This process is repeated until the second guard bar is detected and a whole bar code is completely read. The first scanning line may be set, so that it only reads a predetermined number of bars and the rest of the bar code is read by new scanning lines starting from the last read bar. Alternatively, the bar code region is searched by preliminarily scanning the image region divided into plural rectangular sections. The bar code region is determined based on the number of brightness changes in each divided section. The first guard bar in the bar code can be easily found in this manner.

Claims21

Dependent claims

A method of reading a bar code having a plurality of bars and spaces, the method comprising steps of:

setting detecting lines running in horizontal and vertical directions on two-dimensional image region including a bar code region having a pair of guard bars at both sides thereof, the two-dimensional image region being temporarily stored in an image memory;
detecting one of the guard bars in the bar code region by scanning the image region along the detecting lines;
setting a scanning line starting from the detected guard bar and extending perpendicularly thereto;
scanning the bar code region along the scanning line to read the bar code;
tracing back the scanning line to a bar last read by the scanning line, if the scanning line goes out of the bar code region without reaching the other guard bar;
setting a new scanning line starting from the last read bar and extending perpendicularly thereto to read the rest of the bar code;
and
repeating a new scanning line setting step until a newly set scanning line reaches the other guard bar and a whole bar code is scanned and read.

5 more elements

A method of reading a bar code having a plurality of bars and spaces, the method comprising steps of:

dividing a two-dimensional image region including a bar code region having a pair of guard bars at both sides thereof into a plurality of rectangular sections, the image region being temporarily stored in an image memory;
preliminarily scanning the divided sections;
counting a number of brightness changes in each divided section;
selecting detecting sections which most probably constitute the bar code region from among the divided sections, based on the counted number of brightness changes;
setting a first detecting line running in the detecting sections;
detecting one of the guard bars in the bar code region by scanning the detecting sections along the first detecting line;
setting a scanning line starting from the detected guard bar and extending in the direction of the first detecting line;
scanning the bar code region along the scanning line to read the bar code;
tracing back the scanning line to a bar last read by the scanning line, if the scanning line goes out of the bar code region without reaching the other guard bar;
setting a new scanning line starting from the last read bar and extending perpendicularly thereto to read the rest of the bar code;
and
repeating a new scanning line setting step until a newly set scanning line reaches the other guard bar and a whole bar code is scanned and read.

9 more elements

A method of reading a bar code having a plurality of bars and spaces, the method comprising steps of:

dividing a two-dimensional image region including a bar code region having a pair of guard bars at both sides thereof into a plurality of rectangular sections, the image region being temporarily stored in an image memory;
preliminarily scanning the divided sections;
counting a number of brightness changes in each divided section;
selecting detecting sections which most probably constitute the bar code region from among the divided sections, based on the counted number of brightness changes;
setting a first detecting line running in the detecting sections;
detecting one of the guard bars in the bar code region by scanning the detecting sections along the first detecting line;
setting a scanning line starting from the detected guard bar and extending in a direction of the first detecting line;
scanning a predetermined number of bars or a predetermined distance along the scanning line to read the bar code;
setting a new scanning line starting from the last read bar and extending perpendicularly thereto to read the rest of the bar code;
and
repeating a new scanning line setting step until a newly set scanning line reaches the other guard bar and a whole bar code is scanned and read.

8 more elements

Dependencies are inferred from the claim text.

Method of reading bar code

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Method of reading bar code

Life of this patent

Abstract

Claims21