Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
1999-11-12
2001-12-25
Lee, Michael G. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S462090, C235S462160
Reexamination Certificate
active
06332574
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims benefit of priority of Japanese Patent Applications No. Hei-10-325278 filed on Nov. 16, 1998 and No. Hei-11-270926 filed on Sep. 24, 1999, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of reading a bar code attached to a variety of articles, and more specifically to a method of correctly reading a bar code, even if the image of a bar code taken in by a bar code reader is distorted.
2. Description of Related Art
A variety of bar codes are widely used these days. Some examples are shown in
FIGS. 16A-16C
. A bar code shown in
FIG. 16A
is a usual type, the one shown in
FIG. 16B
has a large height H, and the one shown in
FIG. 16C
has a short profile. Those bar codes have to be correctly read irrespective of their size and shape. If a bar code is scanned as shown in
FIG. 17A
, it can be correctly read because all the bars are scanned by a scanning line. If the scanning line is somewhat slanted as shown in
FIG. 17B
, the bar code is still readable. However, the bar code is unreadable if the scanning line goes therethrough as shown in
FIG. 17C
, because some bars cannot be scanned.
Some counter measures to overcome the unreadable problem have been made, for example, in JP-A-7-93451 and JP-A-10-198754. JP-A-10-198754 proposes to provide main detecting lines and auxiliary detecting lines that are perpendicular to the main detecting lines, so that the auxiliary detecting lines can pass through the bar code if the main detecting lines cannot. In this case, however, there is still a situation where the bar code cannot be read. That is, if none of the main and auxiliary detecting lines passes through the bar code due to too much rotation or distortion of the bar code region relative to the image region, the bar code cannot be read. JP-A-7-93451 proposes to set the scanning line in the direction perpendicular to a bar located at one side of the bar code as shown in
FIGS. 18B and 18C
. It is ideal if an image region taken into the bar code reader and a bar code region are square to each other as shown in FIG.
18
A. In most cases, however, the bar code region rotates relative to the image region as shown in
FIGS. 18B and 18C
. Since the bar code reader proposed by JP-A-7-93451 calculates the inclination of the first bar and sets the scanning line in the perpendicular direction thereto as shown in
FIGS. 18B and 18C
, the scanning line passes through the bar code even if the bar code region is extremely rotated relative to the image region.
However, there are still other situations where the bar code reader proposed by JP-A-7-93451 cannot read the bar code. The bar code reader is not always positioned in parallel to a bar code plane. Some examples are shown in
FIGS. 19A-19C
and
19
A′-
19
D′. If the bar code reader is positioned in parallel to the bar code plane as shown in
FIG. 19A
, the bar code region is not distorted even if it rotates relative to the image region as shown in FIG.
19
A′. If the bar code reader is positioned not in parallel to the bar code plane as shown in
FIG. 19B
, the bar code region is distorted as shown in FIG.
19
B′. If the bar code reader is positioned as shown in
FIG. 19C
, the bar code region is distorted as shown in FIG.
19
C′. Further, if the bar code reader takes a slanted position both in the longitudinal and lateral directions (a combination of
FIGS. 19B and 19C
, the bar code region is extremely distorted as shown in FIG.
19
D′. As exemplified above, the bar code region may be variously distorted according to the position of the bar code reader relative to the bar code plane. If the degree of distortion is not extremely large as shown in FIGS.
19
B′ and
19
C′, the bar code reader proposed by JP-A-7-93451 may be able to read it by setting the scanning line perpendicularly to the first bar. However, in the case the bar code region is extremely distorted as shown in FIG.
19
D′, the bar code cannot be read because the scanning line does not pass through all the bars in the bar code. It is most desirable for the bar code reader to be able to read the bar code, regardless of any rotation or distortion of the bar code region relative to the image region.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-mentioned problem, and an object of the present invention is to provide a method of reading a bar code, in which the bar code is readable even if the bar code image taken into the reader is highly distorted.
A certain area in which a bar code region is included is taken in by a CCD camera as an image region into a bar code reader. In the bar code region, a bar code itself to be read by the bar code reader and a first guard bar located at one side of the bar code and a second guard bar located at the other side of the bar code are included. To find out the bar code region in the image region, detecting lines running in both horizontal and vertical directions are set. The image region is scanned along the detecting lines to search the first guard bar. When the first guard bar is found, a scanning line for reading the bar code is set in the direction perpendicular to the first guard bar. The bar code region is scanned along the scanning line. If the scanning line goes out of the bar code region without reaching the second guard bar, the scanning line is traced back to a bar which is last read by the scanning line. Then, a new scanning line to read the rest of the bar code is set so that it starts from the last read bar and extends perpendicularly thereto. This process are repeated until the second guard bar is found and the bar code is completely read.
Alternatively, the bar code region is scanned along the first set scanning line by a predetermined number of bars or a predetermined distance. Then, a new scanning line is set so that it starts from the last read bar and extends in the direction perpendicular thereto. This process is repeated until the second guard bar is found and a whole bar code is read. The predetermined number of the bars to be scanned by a scanning line may be set at one.
The first scanning line may be set to start from a cross-point of the detecting line and the first guard bar, and the a new scanning line may start from a cross-point of the last read bar and a previous scanning line. It is also possible to shift the starting point of the scanning line toward the center of the bar code region to complete scanning with a smaller number of the scanning lines, in case such a cross-point is located close to the ends portion of the guard bar or the bar in the code bar. The first scanning line may start from the center of the first guard bar, and the following new scanning line may start from the center of the last read bar. In this manner, the number of scanning lines required to read a whole bar code may be saved.
Plural detecting lines may be set, and the horizontal detecting lines may be first used for detecting the first guard bar. After the horizontal detecting lines are all used, then the vertical detecting lines may be used. When plural detecting lines are set, it is preferable to first use the detecting lines closer to the center line of the bar code region and then to sequentially use detecting lines remote from the center line, so that the number of the scanning lines necessary to find the first guard bar can be smaller. This is because it is highly probable that the bar code region is located closer to the center line. For the same purpose, the detecting lines may be set denser around the center line than in portions remote from the center line.
The bar code region in the image region may be searched by preliminarily scanning the image region before setting the detecting lines. In this case, the image region is divided into plural rectangular sections, and the number of brightness changes resulting from existence of the bar code in each divide
Oshima Tadao
Shigekusa Hisashi
Tanaka Masami
Denso Corporation
Lee Diane I.
Lee Michael G.
Pillsbury & Winthrop
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