JP3140184B2 - Barcode symbol reader - 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 symbol reading apparatus for reading a bar code symbol, and more particularly, to "double reading" in a bar code symbol reading apparatus using a two-dimensional imaging device such as a video camera. Prevention) function.

[0002]

2. Description of the Related Art At present, barcode symbols are adopted in many countries, and the types thereof are very large. Representative bar code symbols include JAN / UPC / EAN code, ITF (Interleaved 2 of 5) code, CODE
39, NW-7 code, CODE128, etc. Recently, two-dimensional barcode symbols having a large amount of information and a high recording density have begun to be proposed due to demands for expressing more information, attaching to narrower places, and the like. As such a two-dimensional barcode symbol, C
ODE16K, CODE49, PDF417, DATA
CODE, etc.

[0003] These JAN / UPC / EAN codes, I
TF (Interleaved 2 of 5) code, CODE39, N
There are many types of devices for reading one-dimensional barcodes such as W-7 code and CODE128, and typical types include a pen type, a touch type, and a laser type. On the other hand, there are few types of devices for reading a two-dimensional barcode symbol, and the reading technology has not yet been established.

However, the basic method of reading a barcode symbol is almost the same for a two-dimensional barcode symbol as for a conventional one-dimensional barcode. That is, light is emitted from the light source to the barcode symbol, and the light reflected by the barcode symbol is focused on a light receiving element inside the reader. The bar code symbol is read by decoding the collected signal by an electric circuit including a microcomputer or the like.

Here, important issues other than the reading technique,
That is, one of the functions required as a barcode symbol reading device is a "double reading prevention" function that a barcode symbol once read cannot be read again. In particular, at cash registers such as supermarkets,
This function is of course necessary.

A conventional bar code, JAN / UPC /
EAN code, ITE (lnterleaved 2 of 5) code,
In a device for reading a one-dimensional bar code such as CODE39, NW-7 code, CODE128, etc., a "double reading prevention" function is that data is not transferred to the host computer if the read data is the same as the last time. There are employed a method, a method in which the next barcode is not read for a predetermined time after the data is transferred to the host computer, and a method in which a switch for starting reading is provided and an operator operates the switch.

[0007]

However, in the above-mentioned method of not transferring data to the host computer if the read data is the same as the previous data, there is no problem with the conventional bar code having a very short reading time. However, it is not a good method for a two-dimensional barcode symbol having a long reading time.

In the method in which the next bar code is not read for a predetermined time after the data is transferred to the host computer, it is very difficult to set the predetermined time, and if the set time is long, the next bar code is easily read. In addition, there is a problem that the same bar code is read twice when the setting time is short. Furthermore, if the operator misplaces the sheet on which the barcode symbol is recorded, the operator will "read twice". Further, in a method in which a switch for starting reading is provided and the operator operates the switch, there is a problem that labor for operating the switch is required. The present invention
In view of the above, it is an object of the present invention to provide a bar code symbol reading device having a reliable "double reading prevention" function.

[0009]

To achieve SUMMARY OF to the above objects, the bar code symbol reading device according to the present invention, Ba
Imaging means for imaging the chromatography code symbol, and bar code symbol detection means for detecting the presence of the bar code symbol from the output signal of the shooting <br/> image unit, the decode enable / disable state of the bar code symbol a state holding means for holding the status information indicating, in response to the detection of the bar code symbol by the bar code symbol detection means, to interpret the contents of the bar code symbol from the image of the bar code symbol picked up by the image pickup means and Lud code means,
After decode <br/> bar code symbol by the decoding means, and the content of in the state information and the decoding prohibition state to the state holding means, then the bar code symbol detection
Bar code symbol detection status changes
And control means for changing the content of the state information in the state holding means to a decoding permission state when the state is held.

[0010]

[Action] That is, the bar code symbol reading device of the present invention, the control means, after decode of the bar code symbol by the decode means, and the content of in the state information and the decoding prohibition state to the state holding means, then , Barco
When the code symbol is no longer detected, the content of the status information in the status holding means is set to the decoding enabled state, so that a medium such as a sheet or a product on which the bar code symbol is pasted can be read from the bar code symbol reading device. Until you recognize that it has been removed,
The barcode symbol is not read (decoded) until the bol is no longer detected , thereby preventing “double reading”.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1A, a bar code symbol reading device according to a first embodiment of the present invention comprises a camera stand 20 and a decoder box 30 connected by a camera cable 10. In the camera stand 20, a sheet or a product including the barcode symbol 40 is illuminated by a lighting device (not shown), and the reflected light is incident on the video camera 21. The video camera 21 captures an image of a sheet, a product, or the like, on which a barcode symbol 40, which is supported by a column 22 and is placed on a base plate 23, is recorded. The video camera 21 converts an optical signal into an electric signal, and further adds a synchronization signal and the like to generate a video signal.
0 to the decoder box 30. The decoder box 30 receives the output signal of the video camera 21, decodes the recorded content of the barcode symbol 40 from the output signal, and transfers the recorded content of the barcode symbol 40 to the host computer 50 or a terminal device (not shown). .

Although it has been described that the sheet or the product on which the barcode symbol 40 is described is placed on the base plate 23, the user moves the space above the base plate 23 while holding the sheet or the product by hand. , Bar code symbol 4
0 may be read.

The decoder backs 30 is configured as shown in FIG. That is, a video signal transmitted from the video camera 21 via the camera cable 10 is input to the video circuit 31. The video circuit 31 separates the synchronizing signal from the input video signal, and performs A / D conversion and digitization.
This digitized signal is stored in a frame memory 32
Is stored in

An image of a sheet or the like containing the barcode symbol 40 stored in the frame memory 32 is scanned by the high-speed operation circuit 33 (image information is detected from the memory 32), and the detection of the presence or absence of the barcode symbol 40 and the bar The decoding of the code symbol 40 is performed. The decoded contents are temporarily stored in the decoding result storage memory 34. The high-speed operation circuit 33 clears the decoding permission flag 35 (decoding is prohibited) upon completion of the decoding.
I do.

The CPU 36 controls each component. For example, the CPU 36 outputs a capture start signal for instructing capture of an image to the frame memory 32 to the video circuit 31, and outputs a bar code symbol 40 to the high-speed operation circuit 33. And the decoding start signal of the bar code symbol 40 is output. The high-speed operation circuit 33 outputs the detection state signal of the bar code symbol 40 and the bar code symbol 40.
And the operation of each section is controlled in response to the decoding and check end signals. After the decoding permission flag 35 indicating whether the barcode symbol 40 can be decoded is set (decoding permission), when the barcode symbol 40 can be detected, the barcode symbol 40 is recorded from the decoding result storage memory 34 to the barcode symbol 40. The obtained information is taken out, the host interface circuit 37 is controlled, and the information is transferred to the host computer 50 or the like.

Here, the symbol configuration of the barcode symbol 40 will be briefly described. In this embodiment, the barcode symbol 40 is a two-dimensional barcode symbol PDF4.
17 is used.

This two-dimensional bar code symbol PDF41
As shown in FIG. 2A, reference numeral 7 denotes a label portion 41 which is an information component to be decoded, which is composed of a bar code character group composed of a combination of a bar and a space, and a start / stop portion arranged before and after the label portion 41. It has a start code 42 and a stop code 43 which are stop characters. One code consists of four bars and four spaces except for the stop code 43. The start and stop codes 42 and 43 are two-dimensional barcode symbols PDF4 called big bars.
It starts with the large bars 42a, 43a, which are also the features of the seventeen. Hereinafter, the operation of the "double reading prevention" mechanism in the bar code symbol reading apparatus having such a configuration will be described with reference to FIG.
This will be described with reference to the flowchart of FIG.

First, the CPU 36 outputs a capture start signal to the video circuit 31, and captures an image into the frame memory 32 (step S1). After the image capturing is completed, the CPU 36 outputs a detection start signal of the barcode symbol 40 to the high-speed operation circuit 33, and the high-speed operation circuit 33 detects the presence / absence of the barcode symbol 40 and detects the position (step S2). .

The detection of the presence / absence of the bar code symbol and the detection of the position are performed by the big bars 42a and 43a provided in the start code 42 and the stop code 43 in the two-dimensional bar code symbol PDF417 of FIG. This can be done by confirming the existence of a typical part. In the case of the two-dimensional barcode symbol DATA CODE, this can be performed by confirming the presence of a characteristic portion such as an L-shaped outer frame. Further, as for a conventional one-dimensional barcode, for example, as disclosed in JP-A-2-23483, a method is used in which it is determined that there is a barcode symbol when it is confirmed that there are a plurality of parallel bars. be able to. Then, the high-speed operation circuit 33 uses the detection result of the barcode symbol 40 as a detection state signal as a detection state signal.
Output to PU36.

The CPU 36 determines whether or not the bar code symbol 40 exists in the image captured in the frame memory 32 by determining the detection state signal from the high-speed operation circuit 33 (step S3). And
When the barcode symbol 40 does not exist, the process returns to the step S1 to instruct the image capture again.

When the barcode symbol 40 is present, a decoding start signal of the barcode symbol 40 is output to the high-speed operation circuit 33 to cause the high-speed operation circuit 33 to decode the barcode symbol 40 (step S4). . After confirming that the decoding permission flag 35 is set (decoding permitted) in response to the decoding start signal, the high-speed operation circuit 33 outputs the frame memory 32.
The information of the barcode symbol is decoded from the image of the barcode symbol 40 captured in the step (1). Further, the high-speed operation circuit 33 checks the decoding result (step S5). This decoding content check is performed only when the decoding result is simply confirmed (JAN / UPC / EA).
N code, ITF ((lnterleaved 2 of 5) code, C
There are conventional one-dimensional barcodes such as ODE39, NW-7 code, and CODE128), but there are also cases involving error correction (two-dimensional barcode symbols such as PDF417 and DATA CODE). And the high-speed operation circuit 33
Outputs to the CPU 36 a decode and check end signal of the bar code symbol 40 including the information of the check result.

Here, the CPU 36 includes a high-speed arithmetic circuit 33.
The decoding of the bar code symbol 40 and the check end signal are judged (step S6). If decoding is not successful, the process returns to step S1 and repeats the steps from the capture of the image. Also, when decoding is correctly performed, the CPU 36 operates the high-speed operation circuit 33.
And outputs a decode result holding signal to the terminal. High-speed operation circuit 33
Temporarily stores the decoded contents in the decode result storage memory 34 in response to the decode result holding signal, and clears the decode permission flag 35 (decode disable).
(Step S7).

Next, the CPU 36 takes out the information recorded in the bar code symbol 40 from the decoding result storage memory 34, controls the host interface circuit 37, and transfers the information to the host computer 50 or a terminal device (not shown). (Step S8). After that,
This is the "prevent double reading" function.

That is, the video circuit 3 is sent from the CPU 36 again.
1, a start signal for capturing an image into the frame memory 32 is output, and the image is captured (step S9). After completion of the capture of the image, the high-speed operation circuit 33 detects the base plate 23 (step S10).

Here, when the base plate 23 cannot be detected in the image captured in the frame memory 32, it is confirmed that the decoding permission flag 35 is cleared (step S11), and the process is repeated from the image capturing in step S9. It is. That is, after the transfer to the host computer 50 or the like is completed, if the base plate 23 cannot be detected yet, the sheet or the product on which the barcode symbol 40 transferred to the host computer 50 or the like is recorded is still in use. It is determined that the bar code symbol has not been removed from the bar code symbol reading device, and the process is prevented from proceeding.

On the other hand, when the base plate 23 has been detected (step S11), the CPU 36 sets the decode permission flag 35 (step S12). That is, when the base plate 23 can be detected in the image taken into the frame memory 32, the decoding permission flag 35 is set. Thereafter, the process returns to step S1, and the above-described processing is repeated. Next, the method of detecting the base plate 23 in step S10 will be described in detail.

FIG. 2B shows a state where the bar code symbol 40 is stored in the frame memory 32. Actually, the projection image of the barcode symbol 40 captured by the video camera 21 is stored in the frame memory 32. However, for simplification of the description, the two are not particularly distinguished from each other. .

Now, as shown in FIG. 2B, an arbitrary check line 60 on the frame memory 32 is defined, and the pixel intensity on this line is read. In the case as shown in this figure, since the barcode symbol 40 exists in the screen, the pixel intensity on the check line 60 is bright as shown by (1) in FIG. There are parts and dark parts. Also, the barcode symbol 40
Does not exist (that is, when the base plate 23 of the apparatus is imaged), the intensity becomes almost uniform as shown by the broken line (2) in FIG. 2C.

As shown in FIG. 2D, the histogram of the pixel data clearly has a difference in frequency distribution depending on the presence or absence of a barcode symbol. Therefore, as shown in the figure, a threshold value is determined in advance, and if the number of pixels below the threshold value is equal to or less than a specified number, the high-speed operation circuit 33 determines that the barcode symbol 40 does not exist, Board 2
3 is determined to be detected.

The check line 60 includes:
It is clear that the accuracy can be further improved by using a plurality of lines instead of just one as shown in FIG. Usually, one frame image is captured in 1/30 second, so it is preferable to define as many check lines as possible within this time. For example, four lines each in the vertical and horizontal directions and two lines in the diagonal direction can be defined.

Alternatively, instead of the histogram of the pixel data on the check line 60, a histogram of the image data of all the pixel planes or a histogram of the image data in an area of an arbitrary size at the center may be used. By comparing with the value, the base plate 23 can be detected. With the above-described method, the base plate 23 of the apparatus can be detected.

In the above description, a method of decoding barcode symbols by the CPU 36 and the high-speed operation circuit 33 has been described. However, if a high-speed element such as a DSP (digital signal processor) is used as the CPU 36, , CPU (DSP) 36 is a high-speed operation circuit 33
It is also possible to double. In the above description, the decoder box 30 and the camera stand 20 are separate bodies, but they may be integrated.

In the above embodiment, the bar code symbol in the PDF417 format is used as the bar code symbol 40. However, the present invention is not limited to this.
Other two-dimensional barcodes such as E49, CODE16K, and J
A conventional one-dimensional barcode such as an AN code may be used. Next, a second embodiment of the present invention will be described.

The basic configuration of the second embodiment is the same as that of the first embodiment. However, only the method of detecting the base plate 23 (step S10) is different. Therefore, only the method of detecting the base plate 23 will be described here.

As in the first embodiment, FIG.
As shown in (1), an arbitrary check line 60 on the frame memory 32 is defined. In this case, since the barcode symbol 40 exists in the screen, the check line 60
As shown by (1) in FIG. 2C, the upper pixel intensity has a bright part and a dark part. When the barcode symbol 40 does not exist (that is, when the base plate 23 of the apparatus is imaged), the intensity becomes almost uniform as shown by (2) in FIG. 2C.

When one-dimensional Fourier transform is performed on such pixel intensity data on the check line 60, the result is as shown in FIG. That is, when the barcode symbol 40 exists, its distribution extends to a higher frequency. Therefore, as shown in the figure, a threshold value is determined in advance, and if there is only a frequency component lower than the threshold value, it is determined that the barcode symbol 40 does not exist, that is, the base plate 23 of the apparatus is detected.

In the second embodiment, as in the first embodiment, a plurality of check lines 60 can be provided. Any area or the entire screen can be used as the check area.

The two-dimensional image pickup device such as the video camera 21 is not limited to the one using an area sensor typified by a two-dimensional CCD or an image pickup tube. May be used in combination. Further, even if the frame memory 32 does not cover the entire imaging area, the base plate 23 can be detected as long as there is an area for at least one line.

In the second embodiment, a barcode symbol in the PDF417 format is used as the barcode symbol 40. However, the present invention is not limited to this, and other two-dimensional barcodes such as CODE49 and CODE16K are used. A conventional one-dimensional barcode such as a code or a JAN code may be used. Next, a third embodiment of the present invention will be described.

The basic structure of the third embodiment is the same as that of the first embodiment. However, the method of detecting the base plate 23 (step S10) is different from that of the second embodiment. Therefore, here, only the method of detecting the base plate 23 will be described.

The base plate 23 used in this embodiment includes:
As shown in FIG. 4B, a specific barcode symbol 70 is printed in advance in the imaging range 23A on the base plate 23. Then, when a barcode symbol can be detected on the frame memory 32 and its content matches the content of this specific barcode symbol 70, the base plate 23 of the apparatus is detected, that is, the barcode symbol 40 is detected. It can be determined that the sheet or the product or the like on which is recorded is removed.

Although the bar code symbol of the PDF417 format is used as the bar code symbol 40 in this embodiment, the present invention is not limited to this.
Other two-dimensional barcodes such as ODE49 and CODE16K, or conventional one-dimensional barcodes such as JAN code may be used.

However, the specific bar code symbol 70
As a matter of course, it is needless to say that the barcode symbol needs to be a content that is not used in the application. Therefore, this embodiment can be said to be an optimal method for a two-dimensional barcode having a large amount of information, rather than a one-dimensional barcode having a small amount of information. Next, a fourth embodiment of the present invention will be described.

The fourth embodiment has the same basic structure as that of the first embodiment. However, the method of detecting the base plate 23 (step S10) is different as in the second and third embodiments. Therefore, here, only the method of detecting the base plate 23 will be described.

The base plate 23 used in this embodiment includes:
As shown in FIG. 4C, a light-emitting element such as an LED 80 is previously embedded at a specific position in the imaging range 23A on the base plate 23 and constantly emits light. Then, the value of each pixel of the image stored in the frame memory 32 is checked, and when a portion having an extremely high signal level exists at a specific position on the frame memory 32, the L level on the base plate 23 of the apparatus is determined.
ED 80 is detected, ie, the bar code symbol 40
It is determined that the sheet or the product or the like on which is recorded is removed.

The range in which the pixel value is checked may be the entire frame memory 32 or an area of any size centered on the position where the LED 80 is provided. Further, it may be an area for one line passing through the position where the LED 80 is provided. Further, it is possible to detect the LED 80 even with the value of one pixel at the position where the LED 80 is provided. In this way, it can be reliably determined that the sheet or the like on which the barcode symbol is recorded has been removed, and thus "double reading prevention" can be realized.

In the fourth embodiment, the LED 80 is located at a specific position in the photographing range 23A on the base plate 23.
Although an example in which a light emitting element such as is embedded is described, the present invention is not limited to this, and characters and graphics having a predetermined shape are fetched into the frame memory 32, and the shape and the shape are determined by known image processing. Any mark may be used as long as the position can be confirmed.

As described above, according to the present invention, instead of decoding the barcode symbol, the barcode symbol is detected by directly detecting the base plate on which a medium such as a sheet on which the barcode symbol is recorded is placed. Detect that the recorded media has been removed,
It realizes the "prevent double reading" function, and the processing speed is fast enough. Therefore, the present invention is not particularly limited to barcode symbol types, but can be said to be particularly effective for two-dimensional barcode symbols having a long reading time.

Even if a medium such as a sheet on which a barcode symbol is recorded is left on the base plate, it is not read twice and no additional parts such as switches are used. It can be said that this is a very preferable method from the viewpoint of properties.

In the above embodiment, the base plate is detected from the "output signal of the image pickup means". However, the present invention is not limited to this. For example, in the fourth embodiment, the LED 8
Light from 0 may be detected by other means such as a photodiode. The position of the photodiode may be information on the base plate so as to be blocked by the barcode,
It may be embedded in the base plate so as to detect light reflected by the back side of the barcode.

[0052]

As described in detail above, according to the present invention,
It is possible to provide a bar code symbol reading device having a reliable “double reading prevention” function.

[Brief description of the drawings]

FIG. 1A is a diagram illustrating a configuration of a first exemplary embodiment of the present invention, and FIG. 1B is a block configuration diagram of the first exemplary embodiment.

FIG. 2A is a diagram showing a symbol configuration of a two-dimensional barcode symbol PDF417 used in the first embodiment, FIG. 2B is a diagram for explaining a check line, and FIG. It is a figure which shows the pixel intensity on a check line, (D) is a histogram of pixel intensity data.

FIG. 3 is a flowchart for explaining the operation of the first embodiment.

FIG. 4A is a diagram illustrating a result of performing a one-dimensional Fourier transform on pixel intensity data on a check line for explaining a method of detecting a base plate in a second embodiment. (B) is a plan view of a base plate used in the third embodiment, and (C) is a plan view of a base plate used in the fourth embodiment.

[Explanation of symbols]

Reference numeral 20: camera stand, 21: video camera, 23: base plate, 23A: shooting range, 30: decoder box,
31 video circuit, 32 frame memory, 33 high-speed operation circuit, 34 decode result storage memory, 35 decode enable flag, 36 CPU, 37 host interface circuit, 40 bar code symbol, 50 host computer 60: check line, 70: specific bar code symbol, 80: LED.

Claims (3)

(57) [Claims] 1. A and imaging means for imaging a bar code symbol, the bar code symbol detection means for detecting the presence of the bar code symbol from the output signal of the imaging means, the decode enable / disable state of the bar code symbol a state holding means for holding the status information indicating, in response to the detection of the bar code symbol by the bar code symbol detection means, to interpret the contents of the bar code symbol from the image of the bar code symbol picked up by the image pickup means and Lud code means, after decode <br/> bar code symbol by the decoding means, the content of in the state information to the state holding means decode
The bar code symbol detection is disabled.
Bar code symbol detection status changes
And control means for changing the content of the status information in the status holding means to a decoding permission state when the status is held. 2. The bar code symbol detecting means according to claim 1, wherein
ー Base installed facing the back of the code symbol
It is detected from the output signal of the imaging means that the board is being imaged.
And a base plate detecting means for projecting the base plate.
When the base plate is detected by the
Wherein the content is changed to a decoding enabled state.
Item 2. The barcode symbol reader according to Item 1. 3. A bar code symbol detecting means, comprising :
ー Base installed facing the back of the code symbol
When light from the LED provided on the board is detected,
Change the content of the status information to decode enabled
The bar code symbol reading device according to claim 1, wherein
Place.