Method for detecting a two-dimensional code existing area, method reading two-dimensional code, and a recording medium storing related programs

• US 6,678,412 B1
• Filed: 04/06/2000
• Issued: 01/13/2004
• Est. Priority Date: 04/08/1999
• Status: Expired due to Fees

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Tanaka, Masami, Nojiri, Tadao, Iida, Masahiro, Shigekusa, Hisashi
• Primary Examiner(s): Mariam, Daniel G.
• Application Number:
  US09/543,881
• Time in Patent Office: 1,377 Days
• Field of Search: 382/137-139, 382/173, 382/181-183, 382/190, 382/192, 382/205, 382/209, 382/217-219, 382/274, 382/306, 382/312, 235/456, 235/462.04, 235/462.09, 235/462.2, 235/462.11, 235/494
• US Class Current: 382/181
• CPC Class Codes: G06K 7/10722 Photodetector array or CCD scanning
• CPC Class Codes: G06K 7/1443 locating of the code in an image

Abstract

An image region of an image data memory is dissected into a plurality of search sections. Brightness change points in each of the search sections are counted based on image data of each search section. A candidate region having a likelihood of involving an information code is detected based on the count value of the brightness change points. And, the candidate region is identified as the existing area of the information code.

Claims

1. A method for estimating an existing area of an information code, comprising the steps of:

inputting a two-dimensional image of an information code;

storing image data of a predetermined image region on an image data memory, said image data including the two-dimensional image of said information code; and

estimating an existing area of said information code in said image region of said image data memory based on said stored image data,

said method further comprising the steps of;

dissecting said image region into a plurality of search sections;

counting brightness change points in each of said search sections based on image data of each search section;

detecting a candidate region having a likelihood of involving said information code based on the count value of the brightness change points;

identifying said candidate region as said existing area of said information code;

obtaining an average of brightness-related values of said image data involved in said search section, and

using said average of brightness-related values as one of judging conditions for detecting and identifying said candidate region.

2. The information code area estimating method in accordance with claim 1, wherein said plurality of search sections are rectangular sections dissected by lines parallel to a main scanning line used for scanning said image region in a horizontal direction and also by lines parallel to a sub scanning line used for scanning said image region in a vertical direction.

3. The information code area estimating method in accordance with claim 2, wherein said information code consists of a plurality of cells arranged in a two-dimensional pattern, and each of said search sections is larger than a minimum size of said cell on said image data memory.

4. The information code area estimating method in accordance with claim 3, wherein each of said search sections is larger than two times the minimum size of said cell on said image data memory.

5. The information code area estimating method in accordance with claim 1, wherein said search sections are arranged so as to correspond to each main scanning line used in a horizontal scanning operation of said image region.

6. The information code area estimating method in accordance with claim 1, wherein each of said search sections is further dissected into a plurality of smaller search sections.

7. The information code area estimating method in accordance with claim 1, wherein said candidate region consists of consecutive search sections, and a higher priority is given to a candidate region positioned near the center of said image region when a plurality of candidate regions are detected.

8. The information code area estimating method in accordance with claim 7, wherein a higher priority is given to a candidate region having a large value in the total number of consecutive search sections involved therein.

9. The information code area estimating method in accordance with claim 1, wherein

a counting operation of brightness change points is performed in parallel with a storing operation of the image data into said image data memory, and

a count table is used to obtain the relationship between the counted data of the brightness change points and corresponding search sections, so that the existing area of said information code can be estimated based the data of said count table.

10. The information code area estimating method in accordance with claim 9, wherein said counting operation of the brightness change points includes the steps of:

renewing a memory region in response to an input of image data so as to store both a brightest data and a darkest data among brightness-related data having been ever received;

calculating a mid value equivalent to an average of said brightest data and said darkest data;

comparing a newly entered data with said mid value to make a bright-dark judgement; and

counting each change in the result of said bright-dark judgement as a brightness change point.

11. The information code area estimating method in accordance with claim 10, wherein

a darkness upper limit and a brightness lower limit are used in said bright-dark judgement, said darkness upper limit is darker than said brightest data by a predetermined darkness margin, and said brightness lower limit is brighter than said darkest data by a predetermined brightness margin,

said bright-dark judgement results in “

bright”

when said newly entered data is not smaller than both of said mid value and said brightness lower limit, and results in “

dark”

when said newly entered data is smaller than said mid value and not larger than said darkness upper limit.

12. The information code area estimating method in accordance with claim 1, further comprising the steps of:

scanning each search section by a plurality of scanning lines,

counting said brightness change points along each scanning line,

obtaining a cumulative count value by counting the number of said brightness change points cumulatively until said search section is completely scanned by said plurality of scanning lines, and

obtaining the total number of the brightness change points of each search section based on said cumulative count value.

13. A method for estimating an existing area of an information code, comprising the steps of:

inputting a two-dimensional image of an information code;

storing image data of a predetermined image region on an image data memory, said image data including the two-dimensional image of said information code; and

estimating an existing area of said information code in said image region of said image data memory based on said stored image data,

said method further comprising the steps of;

dissecting said image region into a plurality of search sections;

counting brightness change points in each of said search sections based on image data of each search section;

detecting a candidate region having a likelihood of involving said information code based on the count value of the brightness chance points; and

identifying said candidate region as said existing area of said information code;

wherein

said search sections are arranged in a hierarchical structure so that one upper-grade search section is dissected into a plurality of lower-grade search sections, and

said method further comprising the steps of;

comparing a count value of brightness change points in each upper-grade search section with a predetermined upper-grade threshold;

detecting a candidate region consisting of consecutive upper-grade search sections having a count value of brightness change points equal to or larger than said upper-grade threshold;

comparing a count value of brightness change points in each lower-grade search section with a predetermined lower-grade threshold, when said lower-grade search section belongs to an upper-grade search section positioned in the vicinity of said candidate region;

adding said lower-grade search section to said candidate region when said lower-grade search section has a count value of brightness change points equal to or larger than said lower-grade threshold; and

identifying said candidate region including said added lower-grade search section as said existing area of said information code.

14. A method for reading an information code, comprising the steps of:

inputting a two-dimensional image of an information code;

storing image data of a predetermined image region on an image data memory, said image data including the two-dimensional image of said information code;

dissecting said image region into a plurality of search sections;

counting brightness change points in each of said search sections based on image data of each search section;

detecting a candidate region having a likelihood of involving said information code based on the count value of the brightness change points;

identifying said candidate region as an existing area of said information code in said image region of said image data memory;

setting search lines only in a limited region corresponding to said candidate region;

detecting said existing area of said information code by searching the image data along said plurality of search lines;

reading the contents of said information code involved in the detected existing area based on the image data of said detected existing area;

obtaining an average of brightness-related values of said image data involved in said search section, and

using said average of brightness-related values as one of judging conditions for detecting and identifying said candidate region.

15. A storing medium for storing a program installable in a computer system for detecting an existing area of an information code on an image data memory, said program determining the steps of:

inputting a two-dimensional image of an information code;

storing image data of a predetermined image region on an image data memory, said image data including the two-dimensional image of said information code; and

estimating an existing area of said information code in said image region of said image data memory based on said stored image data,

said method further comprising the steps of;

dissecting said image region into a plurality of search sections;

counting brightness change points in each of said search sections based on image data of each search section;

detecting a candidate region having a likelihood of involving said information code based on the count value of the brightness change points;

identifying said candidate region as said existing area of said information code;

obtaining an average of brightness-related values of said image data involved in said search section, and

using said average of brightness-related values as one of judging conditions for detecting and identifying said candidate region.

16. A storing medium for storing a program installable in a computer system for reading an information code on an image data memory, said program determining the steps of:

inputting a two-dimensional image of an information code;

storing image data of a predetermined image region on an image data memory, said image data including the two-dimensional image of said information code;

dissecting said image region into a plurality of search sections;

counting brightness change points in each of said search sections based on image data of each search section;

detecting a candidate region having a likelihood of involving said information code based on the count value of the brightness change points;

identifying said candidate region as an existing area of said information code in said image region of said image data memory;

setting search lines only in a limited region corresponding to said candidate region;

detecting said existing area of said information code by searching the image data along said plurality of search lines;

reading the contents of said information code involved in the detected existing area based on the image data of said detected existing area;

obtaining an average of brightness-related values of said image data involved in said search section, and

using said average of brightness-related values as one of judging conditions for detecting and identifying said candidate region.