2D rectangular code symbol scanning device and 2D rectangular code symbol scanning method

• US 20050242186A1
• Filed: 04/21/2005
• Published: 11/03/2005
• Est. Priority Date: 04/28/2004
• Status: Abandoned Application

• Current Assignee: NEC Electronics Corporation (Renesas Electronics Corporation)
• Original Assignee: NEC Electronics Corporation (Renesas Electronics Corporation)
• Inventors: Ohbuchi, Eisaku
• Application Number:
  US11/110,831
• Publication Number:
  US 20050242186A1
• Time in Patent Office: Days
• US Class Current: 235/462.90
• CPC Class Codes: G06K 7/10712 Fixed beam scanning
• CPC Class Codes: G06K 7/1093 sensing, after transfer of the image of the data-field to an intermediate store, e.g. storage with cathode ray tube

Abstract

A two-dimensional rectangular code symbol scanning device inputs two-dimensional image data containing two-dimensional rectangular code symbol data and detects code data corresponding to the two-dimensional rectangular code symbol data. The device has a projective transformation calculator for correcting distortion of the two-dimensional rectangular code symbol data by performing projective transformation of the two-dimensional rectangular code symbol data.

Claims

1. A two-dimensional rectangular code symbol scanning device inputting two-dimensional image data containing two-dimensional rectangular code symbol data and detecting code data corresponding to the two-dimensional rectangular code symbol data, the device comprising:

a projective transformation calculator for correcting distortion of the two-dimensional rectangular code symbol data by performing projective transformation of the two-dimensional rectangular code symbol data.

2. The two-dimensional rectangular code symbol scanning device according to claim 1, further comprising a symbol area detector detecting a corner position of a symbol area of the two-dimensional rectangular code symbol data from the two-dimensional image data and specifying the symbol area of the two-dimensional rectangular code symbol data based on the corner position.

3. The two-dimensional rectangular code symbol scanning device according to claim 1, further comprising a decoder reading the two-dimensional rectangular code symbol data corrected by the projective transformation calculator and transforming the symbol data into the code data.

4. The two-dimensional rectangular code symbol scanning device according to claim 2, further comprising a decoder reading the two-dimensional rectangular code symbol data corrected by the projective transformation calculator and transforming the symbol data into the code data.

5. The two-dimensional rectangular code symbol scanning device according to claim 2, wherein the symbol area detector detects a tentative symbol area by reducing the two-dimensional image data, referring to the reduced image data per reference unit, and extracting a range where a pixel with a prescribed luminance value or above exists in the referred image data, and detects a corner based on the detected tentative symbol area.

6. The two-dimensional rectangular code symbol scanning device according to claim 2, wherein the symbol area detector detects corners by generating two line segments connecting two opposing corner points which are already detected or estimated and one of candidate corners for a corner different from the two corners and shifting the candidate corner until the two line segments touch each side of the symbol area of the two-dimensional rectangular code symbol data.

7. The two-dimensional rectangular code symbol scanning device according to claim 5, wherein the symbol area detector detects corners by generating two line segments connecting two opposing corner points which are already detected or estimated and one of candidate corners for a corner different from the two corners and moving the candidate corner until the two line segments touch each side of the symbol area of the two-dimensional rectangular code symbol data.

8. The two-dimensional rectangular code symbol scanning device according to claim 5, wherein

the two-dimensional image data is rectangular image data,

the two-dimensional rectangular code symbol data is square symbol data,

the symbol area detector comprises a unit of performing line scan from a plurality of directions which shifts a line in parallel from an outer side to an inner side of the tentative symbol area to search an intersection with a boundary of the tentative symbol area, a unit of setting a plurality of intersections searched by the line scan to candidate corners, and a unit of determining four corners from the candidate corners, the four corner being a first point which is closest to the corner of the two-dimensional rectangular code symbol data, a second point which is point-symmetric to the first point with respect to a weighted center of the plurality of candidate corners, and a third and a fourth point which are closest to a perpendicular bisector of the first and the second point, thereby detecting corners.

9. The two-dimensional rectangular code symbol scanning device according to claim 4, wherein

the symbol area detector divides the symbol area of the two-dimensional rectangular code symbol data by a perpendicular bisector of a side on a rectangle closest to a point on the boundary of the symbol area of the two-dimensional rectangular code symbol data where the difference is maximum when a difference between a side on a rectangle generated by connecting the detected corners and the boundary of a symbol area of the two-dimensional rectangular code symbol data becomes equal to or more than a predetermined value, and specifies the symbol area of the two-dimensional rectangular code symbol data to each divided area,

the projective conversion calculator corrects distortion of the two-dimensional rectangular code symbol data by performing projective transformation of each of the divided two-dimensional rectangular code symbol data specified by the symbol area detector, and

the decoder combines and reads each of the two-dimensional rectangular code symbol data corrected by the projective conversion calculator.

10. The two-dimensional rectangular code symbol scanning device according to claim 4, wherein

the symbol area detector, after detecting corners, sets an estimated point in an outer side of the symbol area of the two-dimensional rectangular code symbol data from a midpoint of a line segment connecting the corners, generates two line segments connecting the corners at both ends of the line segment connecting the corners and the estimated point, searches a new corner by shifting the estimated point until the two line segments touch each side of the symbol area of the two-dimensional rectangular code symbol data, divides the symbol area of the two-dimensional rectangular code symbol data by a line segment connecting the new corner, and specifies the symbol area of the two-dimensional rectangular code symbol data for each divided area,

the projective conversion calculator corrects distortion of each of the divided two-dimensional rectangular code symbol data by performing projective transformation of each of the two-dimensional rectangular code symbol data specified by the symbol area detector, and

the decoder combines and reads each of the divided two-dimensional rectangular code symbol data corrected by the projective conversion calculator.

11. The two-dimensional rectangular code symbol scanning device according to claim 2, wherein the two-dimensional rectangular code symbol data is symbol data comprising black and white binary image, and

the symbol area detector sorts a luminance value of each pixel in a target image, binarizes the two-dimensional image data with a middle value as a luminance threshold value, and detects a corner position of the symbol area of the two-dimensional rectangular code symbol data based on the binarized two-dimensional image data.

12. The two-dimensional rectangular code symbol scanning device according to claim 3, wherein the two-dimensional rectangular code symbol data is symbol data comprising black and white binary image, and

the symbol area detector sorts a luminance value of each pixel in a target image, binarizes the two-dimensional image data with a middle value as a luminance threshold value, and detects a corner position of the symbol area of the two-dimensional rectangular code symbol data based on the binarized two-dimensional image data.

13. The two-dimensional rectangular code symbol scanning device according to claim 4, wherein the two-dimensional rectangular code symbol data is symbol data comprising black and white binary image, and

the symbol area detector sorts a luminance value of each pixel in a target image, binarizes the two-dimensional image data with a middle value as a luminance threshold value, and detects a corner position of the symbol area of the two-dimensional rectangular code symbol data based on the binarized two-dimensional image data.

14. The two-dimensional rectangular code symbol scanning device according to claim 1, wherein

the two-dimensional rectangular code symbol scanning device is a mobile phone, and

the two-dimensional image data is inputted by a camera provided for the mobile phone.

15. The two-dimensional rectangular code symbol scanning device according to claim 2, wherein

the two-dimensional rectangular code symbol scanning device is a mobile phone, and

the two-dimensional image data is inputted by a camera provided for the mobile phone.

16. The two-dimensional rectangular code symbol scanning device according to claim 3, wherein

the two-dimensional rectangular code symbol scanning device is a mobile phone, and

the two-dimensional image data is inputted by a camera provided for the mobile phone.

17. A two-dimensional rectangular code symbol scanning method comprising:

inputting two-dimensional image data containing two-dimensional rectangular code symbol data;

detecting a corner position of a symbol area of the two-dimensional rectangular code symbol data from the inputted two-dimensional image data and specifying the symbol area of the two-dimensional rectangular code symbol data based on the corner position;

correcting distortion of the two-dimensional rectangular code symbol data by performing projective transformation of the inputted two-dimensional rectangular code symbol data; and

reading the corrected two-dimensional rectangular code symbol data and transforming the symbol data into code data corresponding to the data.

18. The two-dimensional rectangular code symbol scanning method according to claim 17, wherein the symbol area of the two-dimensional rectangular code symbol data is specified by detecting a tentative symbol area by reducing the two-dimensional image data, referring to the reduced image data per reference unit, and extracting a range where a pixel with a prescribed luminance value or above exists in the referred image data and detects a corner based on the detected tentative symbol area, and performing line scan from a plurality of directions which shifts a line in parallel from an outer side to an inner side of the tentative symbol area to search an intersection with a boundary of the tentative symbol area, setting a plurality of intersections searched by the line scan to candidate corners and determining from the candidate corners four corners of a first point which is closest to the corner of the two-dimensional rectangular code symbol data, a second point which is point-symmetric to the first point with respect to a weighted center of the plurality of candidate corners, and a third and a fourth point which are closest to a perpendicular bisector of the first and the second point, thereby detecting corners.

19. The two-dimensional rectangular code symbol scanning method according to claim 17, wherein the symbol area of the two-dimensional rectangular code symbol data is specified by generating two line segments connecting two opposing corner points which are already detected or estimated and one of candidate corners for a corner different from the two corners, and shifting the candidate corner until the two line segments touch each side of the symbol area of the two-dimensional rectangular code symbol data.

20. The two-dimensional rectangular code symbol scanning method for detecting code data contained in two-dimensional image data, the method comprising:

scanning two-dimensional image data;

performing projective transformation for correcting distortion of the scanned two-dimensional image data; and

detecting code data from the projective-transformed two-dimensional image data.