JP3290738B2 - Barcode detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bar code detecting device for detecting a bar code from image data including a bar code image.

[0002]

2. Description of the Related Art In recent years, POs in supermarkets, etc.
With the remarkable spread of point-of-sales (S) systems, barcodes have become ubiquitous. There are dozens or more types of barcodes, which are roughly classified into one-dimensional barcodes and two-dimensional barcodes.

A one-dimensional bar code has a structure in which bars and spaces are alternately arranged in a line. In addition to JAN as shown in FIG. 3A, ITF, CODE128, CO
There are various code systems such as DE39.

However, the amount of information that can be stored in these one-dimensional barcodes is as small as about ten and several characters.
A new barcode having a large amount of information called a dimension barcode has been developed. For example, PDF417 as shown in FIG. 3B and DAT as shown in FIG.
ACODE, VERICOD as shown in (D) of FIG.
E and other various code systems such as Code16K have been proposed. These two-dimensional barcodes increase the information amount by stacking one-dimensional barcodes or developing data in a matrix.

[0005] The decoding method of each of the above barcodes differs depending on the shape of the barcode. For example, in a one-dimensional barcode, generally, a laser having a scanning pattern in a plurality of directions is configured such that one laser scans the entire barcode, or a line sensor is contacted so as to scan the entire barcode. The bar code data is determined and decoded by detecting margins existing on both sides of the bar code. In recent years, as disclosed in, for example, JP-A-2-23484, image processing such as contour detection is performed from image data including a barcode image to extract a barcode region, A method of determining a scanning line to cross and decoding the scanning line has also been proposed.

In the case of PDF417, a barcode is imaged by an area sensor and is temporarily stored in a frame memory. The row is scanned by reading the data of the frame memory in the horizontal and vertical directions, the start / stop codes 100 and 102 characteristic of the PDF 417 are detected, the position of the bar code is determined, and the bar code exists. Efficient decoding is performed by finely scanning only the area. Alternatively, since the PDF417 has a structure in which one-dimensional barcodes are stacked, it is possible to decode by scanning a row by shaking the laser two-dimensionally.

In DATACODE and VERICODE, a barcode image is picked up by an area sensor, and a frame memory is scanned to obtain a characteristic pattern of each code, that is, an L-shaped frame 104 of DATACODE, VERICOD.
The square outer frame 106 of E is detected, and the position of the barcode is determined and decoded.

As described above, in the method in which a barcode is picked up by an area sensor, data is stored in a frame memory, and the data is decoded, it is unknown where the barcode image exists in the frame memory. However, it is impossible to scan the frame memory in all directions in all directions, and the processing time is very long and impractical. Therefore, a method has been generally proposed in which a barcode position in a frame memory is detected, and only a region where the barcode exists is scanned and decoded.

For example, in a system in which an article on which a barcode is printed or pasted flows on a belt conveyor, and the barcode is picked up and decoded by an area sensor arranged at a predetermined position, decoding processing generally takes a long time. Therefore, the key to speeding up is to perform decoding only when a barcode comes. Therefore, various methods have been proposed for detecting the presence of the barcode itself in the frame memory and starting decoding only when the barcode exists.

[0010]

However, in order to detect the presence or position of a barcode in the frame memory,
It is necessary to perform a pre-scan for appropriately scanning the inside of the frame memory, and a simple and generally used method is to roughly scan the entire screen every several pixels in the horizontal and vertical directions. If the pre-scan for bar code detection is improperly performed, the processing time may be long or the bar code may not be detected.

In the barcode detection method, the algorithm for finding a characteristic pattern of each code from the scan data is different for each code. Therefore, it is necessary to prepare a plurality of detection algorithms according to the type of barcode to be decoded. There is.

Further, the above-mentioned algorithm has a problem that unless it is known which barcode is to be decoded, it is impossible to know which pattern to find.

The present invention has been made in view of the above points, and can detect any type of barcode in a frame memory using the same algorithm, and the type of barcode can be determined in advance. It is an object of the present invention to provide a barcode detection device that can detect even if it is not known.

[0014]

In order to achieve the above object, a bar code detecting apparatus according to the present invention comprises a frame memory for storing multi-valued image data including a bar code image, and an image stored in the frame memory. D for performing discrete cosine transform (DCT) on the data for each block of a predetermined size
CT means, coefficient storing means for storing DCT transform coefficients obtained by the DCT means, and bar code detecting means for detecting a bar code from the transform coefficients stored in the coefficient storing means. Things.

[0015]

According to the bar code detecting device of the present invention,
The DCT means performs discrete cosine transform of the image data stored in the frame memory for each block of a predetermined size, and stores the DCT transform coefficients obtained by the DCT in the coefficient storage means. Then, the barcode detection means detects a barcode from the conversion coefficient stored in the coefficient storage means.

That is, by binarizing multi-valued data to eliminate fluctuations in pixel values in the black / white area, the DCT
To decompose into frequency components. Then, barcode detection is performed by extracting features of the barcode area from the frequency components (DCT transform coefficients).

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing the embodiments of the present invention, the basic concept of the barcode detecting method of the present invention will be described first. The principle is to detect a barcode area from the frequency components of the image data.

DCT is a type of high-efficiency coding that divides image data into frequency components and performs quantization and coding for each component to compress the information amount of the image data. This DC
T is a technique most frequently used in recent years as a data compression technique for moving images and still images.

The image data is divided into blocks of n pixels × n pixels, and DCT transform coefficients obtained by performing DCT on each block are used to determine what frequency component and how strong the data in the block is. Represents For example, if the data in the block is uniform, all the AC components appear, and only the DC component (offset) appears. That is, if the inside of the block is pure black or pure white, only DC components having different magnitudes of DCT transform coefficients are obtained as shown in FIG. 1 (B) or (C). On the other hand, if black-and-white data is mixed in a block, the DCT transform coefficient becomes a complicated value as shown in FIG.

Therefore, since a bar code is composed of black bars and white spaces, when DCT is applied to image data including the bar code, the DCT transforms the image data into black, white, and black-and-white mixed areas. Can be classified. That is,
Since the AC component exists in the block in which the barcode, the character, and the like exist, the white area of the background or the quiet zone of the barcode is distinguished from the barcode, the character, and the like. The barcode has a square shape, and the bar and space have a length.
Since the character has various shapes, various frequency components appear in each block, and a specific coefficient cannot be obtained. Using the feature that the barcode can be distinguished from other characters, etc. It is assumed that the barcode area can be detected. An embodiment of the present invention based on the above idea will be described below with reference to the drawings. (First embodiment)

FIG. 1A is a block diagram of a bar code detecting apparatus 10 according to a first embodiment of the present invention. In FIG. 1, reference numeral 12 denotes an input terminal for image data (multi-valued), and reference numeral 14 denotes a frame memory for storing the input image data. Reference numeral 16 denotes a binary conversion unit that divides the image data stored in the frame memory 14 into n × n blocks and binarizes the data in the block with a certain threshold value. Reference numeral 18 denotes the binarized n. × n block data to D
A DCT unit 20 for performing CT is a coefficient memory for storing DCT transform coefficients output from the DCT unit 18 for one screen. Reference numeral 22 denotes a DC stored in the conversion coefficient memory 20.
A barcode detection unit that detects a barcode region from the T-transform coefficient and reads and supplies image data in the barcode region from the frame memory 14 to the decoding unit 24.
The decoding unit 24 converts the data read from the frame memory 14 by the barcode detection unit 22
It decodes the barcode information and transfers and outputs the decoding result to a host device (not shown). Next, the operation of the first embodiment will be described.

That is, image data including a barcode image picked up by a CCD or the like (not shown) is input from the input terminal 12 and stored in the frame memory 14 as shown in FIG. The image data stored in the frame memory 14 is divided into, for example, 8 × 8 pixel blocks of the frame memory 14 by the binary conversion unit 16 and converted into binary data. Since the input image is multi-valued data, its value is slightly scattered for each pixel even in a black bar or a white space. Therefore, if DCT is applied as it is,
Since an AC component appears even in a block that can be regarded as black, the binarization is performed by the binary conversion unit 16 to eliminate fluctuations in data values. Next, an 8 × 8
DCT of the block of pixels is performed, and the conversion result (DCT
(Transformation coefficient) is stored in the coefficient memory 20. This binarization,
DCT is performed on all blocks, and a barcode detection unit 22 detects a barcode area from the DCT transform coefficients of each block. For example, a black block is extracted from the DC component of each block, and a group is formed by neighboring blocks to detect a region forming a substantially quadrangle, which is determined as a barcode region. Then, since the position of the block containing the barcode, that is, the position of the barcode is known, the data corresponding to the area is read from the frame memory 14 and the decoding unit 24 decodes the barcode information by the conventional decoding processing. , And transfer the decoding result.
As described above, the barcode in the image can be detected by decomposing the image data including the barcode image into frequency components and extracting the characteristics of the frequency components. (Second Embodiment) As a modification of the first embodiment, there is a method of detecting characteristic patterns of various barcodes in the processing of the barcode detection unit 22.

More specifically, if blocks having similar frequency components are arranged in a certain direction, and if a number of the columns appear in parallel, it is determined that a one-dimensional barcode exists. Also, in a square area that can be seen as a barcode area,
If there are blocks representing large black bars, PDF4
Judge as 17. Separately, if there is a block group representing a black L-shape or square black frame, DATACODE or VE
It is determined that the code is RICODE, and the data in the frame memory 14 is read out by a decoding method corresponding to each code, and the decoding unit 24 performs a decoding process.

As described above, by decomposing the image data including the barcode image into frequency components, the characteristics of the barcode having various shapes can be expressed by the frequency components. Can be identified. (Third embodiment)

In another embodiment, image data is repeatedly picked up by an image sensor such as a CCD with the same structure as that of the first embodiment, and only when any image is picked up, the process shifts to barcode detection and decoding processing. Thinking system.

In the state where no image is taken, the entire screen is white or black, and the AC component of the DCT transform coefficient does not appear anywhere. Therefore, in the processing of the barcode detection unit 22 in the first embodiment, if there is no AC component, it is determined that nothing has been imaged, and the process proceeds to capture the next image. On the other hand, if an AC component exists,
It is determined that something has been imaged, and the process proceeds to barcode area detection and decoding processing.

As described above, by analyzing the frequency components of the captured image data, it can be detected that an object (bar code) has entered the screen, and the automatic reading of the bar code can be started. (Fourth Embodiment) Another embodiment will be described with reference to the block diagram of the barcode detection device 30 shown in FIG.

Referring to FIG. 1, reference numeral 12 denotes an input terminal for image data (multi-valued), and reference numeral 14 denotes a frame memory for storing the input image data. Reference numeral 16 denotes a binary conversion unit which divides the input image data stored in the frame memory 14 into blocks of m × m pixels of the frame memory and binarizes the data in each block with a certain threshold.
Is m large enough to fill the bar code space
This is an expansion processing unit that expands black with a size of xm. Reference numeral 18 denotes the data obtained by expanding the black in the expansion processing section 32 into n × n
(N <= m) DCT unit for performing DCT in block, 20 is D
This is a coefficient memory for storing CT conversion coefficients for one screen. 2
Reference numeral 2 denotes a barcode detection unit that detects a barcode area from the DCT transform coefficients, and 24 denotes a decoding unit that decodes barcode information from data read from the frame memory 14. Next, the operation of the fourth embodiment will be described.

The image data input from the input terminal 12 is stored in the frame memory 14. The image data stored in the frame memory 14 is converted into binary data by a binary conversion unit 16. Next, black expansion processing is performed by the expansion processing unit 32 through a scanning window of m × m size. This is a general method, in which the black pixel is expanded by the size of the scanning window by taking the logical sum of the data in the scanning window. Then, in the barcode area, the space is filled with black, and a large black square is formed. The DCT unit 18 converts the image data including the black barcode image into n
× n blocks, the size of which is smaller than or the same as the scan window size m × m at the time of expansion processing, and DCT is applied. Then, in the DCT transform coefficient, a square block having an AC component appears at a position corresponding to the peripheral portion of the barcode area, and the inside of the block is a block group including only the DC component representing a black block. Therefore, in the barcode detection unit 22,
The barcode area can be detected by extracting the square black block group.

As described above, since the barcode area is black-expanded to be a square black area, a characteristic can be given by the generation of a frequency component, so that the barcode detection processing can be easily performed. (Fifth Embodiment) In the fourth embodiment, after expansion processing, data thinning is performed, and then DCT is performed. Then, since the number of blocks is reduced, the amount of calculation is reduced, and higher-speed processing can be performed.

In the first to fifth embodiments,
The DCT transform coefficients stored in the coefficient memory 20 need not necessarily be all coefficients, and may be only DC components or only DC components and low frequency components of AC.

[0032]

As described in detail above, according to the present invention,
Decompose the image data including the barcode image into frequency components,
Since barcode detection is performed by extracting the characteristics of the frequency components, any type of barcode in the frame memory can be detected using the same algorithm, and the type of barcode is known in advance. It is possible to provide a barcode detection device that can perform detection without using the barcode. Further, the binarization by the binary conversion unit 16 can be omitted.

[Brief description of the drawings]

FIG. 1A is a block diagram of a barcode detection device according to a first embodiment of the present invention, and FIGS. 1B to 1D each show a DC obtained by a discrete cosine transform (DCT).
FIG. 4 is a diagram for explaining a T-transform coefficient.

FIG. 2A is a schematic diagram of image data including a barcode image stored in a frame memory, and FIG. 2B is a block configuration diagram of a barcode detection device according to a fourth embodiment of the present invention.

FIGS. 3A to 3D are diagrams each showing a barcode. FIG.

[Explanation of symbols]

10, 30: bar code detecting device, 12: input terminal, 1
4 ... frame memory, 16 ... binary transform unit, 18 ... discrete cosine transform (DCT) unit, 20 ... coefficient memory, 22 ...
Bar code detection unit, 24... Decoding unit, 32.

Claims (1)

(57) [Claims] 1. A frame memory for storing multi-valued image data including a barcode image, and a discrete cosine transform means for performing discrete cosine transform of the image data stored in the frame memory for each block of a predetermined size. A coefficient storage unit that stores a conversion coefficient obtained by the discrete cosine conversion unit; and a barcode detection unit that detects a barcode from the conversion coefficient stored in the coefficient storage unit. Barcode detection device.