Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
2003-07-17
2004-09-07
Lee, Michael G. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S462240, C235S462090
Reexamination Certificate
active
06786412
ABSTRACT:
The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2002-210211, filed Jul. 18, 2002, the entire disclosure of which is hereby incorporated by reference.
BACKGROUND OF INVENTION
This invention relates to a two-dimensional code reading method, two-dimensional code reading program, recording medium for recording thereon the two-dimensional code reading program, two-dimensional code reading device, digital camera and portable terminal with the digital camera. Specifically, the present invention relates to a two-dimensional code reading method capable of reading accurately and immediately a two-dimensional code image taken obliquely with no contact with the object, two-dimensional code reading program for the same method, recording medium for recording the two-dimensional code reading program and the two-dimensional code reading device for reading a two-dimensional code according to the same method and program.
FIG. 1
shows representative kinds of codes which have been used for encoding information of the tags of products etc. in form of codes readable by computers. In comparison with bar code (“a” in
FIG. 1
) containing information only in horizontal (or vertical) direction of one-dimension, the two-dimensional code containing information in the vertical and horizontal directions of two dimensions can holds a greater volume of information but requires longer time to read.
There are some methods for two-dimensional code, and the two-dimensional codes may be classified basically into two groups: stack type two-dimensional code (b) and matrix type two-dimensional code (c) as shown in FIG.
1
. The stack type two-dimensional code is composed of a number of bar codes holding binary coded data and stacked in multiple layers (rows) in the direction perpendicular to that of arrangement of bars of each bar code. Rows are distinguished from each other by a start code and a stop code provided for each row.
The matrix type two-dimensional code is such that binary coded data is converted into cells that are arranged in two (horizontal and vertical) directions. The display area of the matrix code is represented by a pattern of dark (black) and bright (white) cells (squares in general). The angle and size of the black-and-white cell pattern are read and decoded.
To correctly decode a two-dimensional code, it is necessary to correctly discriminate by brightness/darkness of each bar or each cell. Therefore, it is important to determine a center position of each bar or each cell, which represents the position of data to be read.
An L-type guide cell and cut out symbol are provided for discriminating the direction of a symbol (i.e., two-dimensional code), which allow high-speed reading of two-dimensional code from all directions of 360°.
Representative stack type two-dimensional codes are CODE49, CODE16K and PDF417 and so on and matrix type two-dimensional codes are DATA CODE, QR CODE, MAXI CODE, Veri CODE, CODE1, Array Tag, CP CODE and Carla CODE and so on.
An example of matrix type two-dimensional code is QR code as shown in
FIG. 2
, which code is defined by JIS standard X0510.
FIG. 2
is a view for explaining a summary of the QR code. As shown in
FIG. 2
, model 2 of QR code has specific position detecting element patterns A, B and C disposed at three corners for detecting the position of the QR code. Furthermore, QR code contains indexing patterns D
0
, D
1
, . . . , Dmax (max is model number depending on the number of cells making up QR code) arranged in the area for indexing the positions of respective cells. Timing patterns E and F for guiding the position of each cell are also disposed along the upper side (in a horizontal direction) and the left side (in a vertical direction) of the area of QR code.
In case of two-dimensional matrix code such as QR code, horizontal and vertical inspection lines are set so that they may join two pairs of opposite sides (horizontal sides and vertical sides) through center positions of timing patterns E and F arranged on the respective sides of the code area. In case of two-dimensional stack code made up of a stack of bar codes, an inspection line is set for each bar code by joining a pair of opposite sides in the direction of arrangement of bars of each bar code. In the two-dimensional matrix code, each cell is found at a cross point of respective inspection lines set in the above-described manner and information, and in the two-dimensional stack code, each cell is found at a cross point where an axis of a bar code layer and the inspection line intersect each other, then information contained in the cell is read and decoded for reading two-dimensional code.
FIG. 3
is a flowchart depicting the basic procedure of reading the QR code shown in FIG.
2
. In the flowchart of
FIG. 3
, three position detecting element patterns A, B and C are found first by detecting specific features of position detecting patterns (Step S
1
), the symbol model number, i.e., the number of cells for recording data (the size of the two-dimensional code) is then detected (Step S
2
), center positions of respective cells composing the QR code are determined by calculation (Step S
3
), white (bright) and black (dark) are discriminated from image data corresponding to the respective cell positions and binary coded data “0” or “1” is generated (Step S
4
and decoding of the QR code is finally conducted based on the binary coded data of each cell position (Step S
5
). Generally, since the calculation of cell center position at Step S
3
and generation of binary coded data at Step S
4
are carried out for each cell, the above sequential steps are repeated (as a double loop in vertical and horizontal directions).
For detecting the coordinate positions (image coordinate positions) of the QR code (Step S
1
), it is also possible to use additional information such as indexing patterns Di (i=0, 1, . . . , max) and/or timing patterns E and F. Furthermore, QR code is divided into areas based on the indexing patterns Di (i=0, 1, . . . , max) and timing patterns E and F to improve the accuracy of indexing. Alternatively, it is also possible to first detect the timing patterns E and F featured by alternations of bright (white) cell and dark (black) cell arranged between the position detecting element patterns A, B and C and find coordinates of center positions of the cells with respect to the position detecting element patterns A, B, C and timing patterns E, F, by image processing method, then determine the center positions of other cells by calculation using the detected coordinate.
However, it must be noted that the two-dimensional code image can not always be detected without distortion, for example, the two-dimensional code image read aslant may be often distorted. In particular, when the two-dimensional code is read at distance from the recording material (paper in many cases) by a non-contact type apparatus such as a digital camera and a portable telephone with a digital camera incorporated therein, the two-dimensional code image is probably distorted.
In this case, a kind of cell (i.e., information recorded in the cell) for the data cells disposed near to the position detecting element patterns A, B, C, the indexing patterns Di and timing patterns E, F can be accurately read owing to a small difference between the read position determined by calculation and the actual cell position. However, since the deviation of the calculated cell position to read from the actual cell position may be increased as the cell is apart further from the position detecting element patterns A, B, C, the indexing patterns Di and timing patterns E, F, it becomes difficult to accurately discriminate the kind of the cells distant from the above patterns.
A method for accurately reading two-dimensional code aslant read and distorted is disclosed in Japanese Patent Publication No. 2742555.
This method is to devise the setting of inspection lines for determining cell center positions based upon the fact that the distortion of two-dimensional code read at an an
Birch & Stewart Kolasch & Birch, LLP
Lee Michael G.
Nguyen Kimberly D.
Sharp Kabushiki Kaisha
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