JP4058883B2 - Optical information reader - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for reading an information code attached to a moving article.
[0002]
[Prior art and problems to be solved by the invention]
Conventionally, as a method for optically reading an information code such as a bar code or a two-dimensional code, a light emitting means such as an LED emits light for reading optical information to an optical information recording surface, and a photosensor as a light receiving element is arranged. There has been known a technique in which an information code is taken into an apparatus as an image from reflected light using the CCD sensor and decoded.
[0003]
Some optical information readers of this type read information codes that are in motion, for example, information codes attached to articles conveyed by a belt conveyor. In this case, considering the speed of the conveyor such as a belt conveyor, the information code attached to the article is just at the timing of entering the field of view of the CCD sensor, the light for reading optical information is emitted, the CCD sensor is exposed, and the information code is imaged. It was taken in as.
[0004]
However, even if only the speed of the conveying device such as a belt conveyor is considered, if the position of the information code attached to the article is shifted for each article, the information code protrudes from the field of view of the CCD sensor at the take-in timing, A situation occurs in which part or all of the information code area does not enter the captured image.
[0005]
Conventionally, it has been proposed that a plurality of images be captured and decoded as a method corresponding to such a positional shift of the information code. In that case, a plurality of images are captured by grasping the conveyance position of the article based on a signal from a detection unit that detects that the article has arrived at a predetermined position of the conveyance apparatus.
[0006]
However, this conventional configuration has the following restrictions. That is the arrangement relationship between the image capture unit (image capture unit) and the article detection unit (detection unit). In other words, in the past, it was detected that an article had reached a predetermined position, and an image was captured based on the detection timing. Therefore, the article detection unit must always be in front of the image capture unit in the transport direction, that is, the image Prior to taking in, the article was placed at a position where it could be detected. This is because when the position of the information code is displaced, if the article detection unit is not in front, the information code may already pass through the field of view of the CCD sensor when the article is detected. Such restrictions on the arrangement relationship cause a reduction in the size of the apparatus.
[0007]
In the present invention, even when there is a possibility that the position of the information code attached to the article may be shifted, the information code can be taken in and decoded, and the arrangement relationship between the image taking-in unit and the article detecting unit is restricted. An object of the present invention is to provide an optical information reading apparatus that eliminates the above-mentioned problem.
[0008]
[Means for Solving the Problems and Effects of the Invention]
In the optical information reading apparatus according to the first aspect, the optical information recording surface of the article is captured as a plurality of images. This is realized by the image capturing means repeatedly capturing images at predetermined time intervals. Note that it is conceivable that the image capturing means is constituted by using, for example, a CCD sensor, and the field of view of the CCD sensor becomes an area of one image. In this case, a part of the optical information recording surface may be recorded in duplicate on two consecutive images.
[0009]
The image captured in this way is stored in the image memory by the image storage control means. At this time, the image storage control means causes the first predetermined number of images new in time to be stored in the image memory. For example, in a configuration in which six images are stored, the latest image is overwritten on the oldest image among the six images.
[0010]
Then, the detecting means detects that the article has arrived at a predetermined position on the conveyance path. The detection knowledge means, we need not necessarily be provided in a housing configured for reading optical information is arranged. Based on the article detection time by the detection means, the process execution means performs a decoding process on the image stored in the image memory. The decoding process is a process for decoding an information code included in an image.
Specifically, the process execution means uses the first predetermined number of images including the reference image and images before and after the reference image, with the image captured by the image capture means after a predetermined time has elapsed from the time of article detection as the reference image. A smaller second predetermined number of images are read from the image memory, and a predetermined number of positioning symbols included in the information code are detected to identify the position of the information code from the read image, and the specified information code is decoded. Apply. For example, an image that will be entered if the information code is attached to the normal position is set as a reference image, and the number of images before and after the reference image is specified in accordance with the possibility that the information code is shifted.
[0011]
Conventionally, a configuration has been proposed in which an article is first detected based on the idea of capturing an image at an appropriate timing, and the idea of capturing a plurality of images in consideration of positional deviation of information codes has been reached. However, if the idea of capturing a plurality of images is assumed, it is not necessary to detect an article first. This is because an image captured at a predetermined timing may be decoded at a timing based on the article detection time.
[0012]
In the present invention, the first predetermined number of images are captured at a predetermined timing, and the image memory image is decoded based on the article detection time point. Therefore, as the number of images taken into the image memory is increased, there is no restriction on the article detection time point. That is, if the number of images taken into the image memory is increased, the article detection time can be delayed as much as possible.
[0013]
As a result, even when the position of the information code attached to the article is misaligned, the information code can be taken in and decoded, and further, the restriction on the arrangement relationship between the image fetching section and the article detecting section can be eliminated. .
For example, in a configuration in which six images are stored in the image memory, when the optical information recording surface of the actual article fits in five images, it is not necessary to set all six images as decoding targets.
According to a second aspect of the present invention, when the prescribed number of positioning symbols is detected over a plurality of images , the processing execution unit synthesizes the plurality of images and performs a decoding process on the combined image. do it. This ensures that the information code is decoded .
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view of a system configuration including a two-dimensional code reader 10 according to an embodiment. FIG. 2 is a schematic perspective view of FIG. 1 viewed from a direction indicated by a symbol K in FIG.
[0018]
The two-dimensional code reader 10 is a stationary device, and reads a QR code printed on the upper surface (hereinafter referred to as “optical information recording surface 71 b”) of an article 71 conveyed by the belt conveyor 70. The two-dimensional code reader 10 is fixed to a post (not shown) on the side of the belt conveyor 70 and is disposed above the belt conveyor 70.
[0019]
The two-dimensional code reading device 10 includes an article detection unit 12. First, the article detection unit 12 will be described.
The article detection unit 12 emits light downward and detects the reflected light. Then, a signal indicating whether reflected light is detected is output. The light from the article detection unit 12 is absorbed when irradiated to the belt conveyor 70 due to the difference in color between the belt conveyor 70 and the optical information recording surface 71b, whereas when light is irradiated to the optical information recording surface 71b. Reflected. In this embodiment, when the article 71 reaches a predetermined position on the belt conveyor 70, specifically, the front end surface 71a of the article 71 is a position indicated by symbol α in FIG. 2 (hereinafter simply referred to as “position α”). It is assumed that reflected light is detected when it reaches.
[0020]
In addition, the two-dimensional code reader 10 has a configuration for reading optical information. In FIG. 2, only the image capturing unit 13 is shown so as to show the arrangement relationship with the article detection unit 12, but as shown in FIG. 3A, the data processing unit 11 and the binarizing unit 14 are also shown. , A synchronization pulse generator 15 and a ring buffer 16 are provided.
[0021]
The data processing unit 11 is configured as a computer system including a CPU, a ROM, a RAM, an I / O, and the like, and executes a later-described decoding process according to a program stored in the ROM. The signal from the article detection unit 12 described above is input to the data processing unit 11.
[0022]
The image capturing unit 13 includes an illumination LED and a CCD sensor (not shown). The illumination LED emits red light for illumination, the reflected light is received by the CCD sensor, and a predetermined area is imaged. A dimensional image is output as a horizontal scanning line signal. The scanning line signal is amplified and output to the binarization unit 14.
[0023]
The binarization unit 14 binarizes the amplified scanning line signal based on the threshold value and outputs the binarized signal to the ring buffer 16.
The synchronization pulse generator 15 outputs a synchronization pulse for the image capturing operation. The image capturing unit 13 repeatedly captures images at predetermined time intervals based on the synchronization pulse. The ring buffer 16 also stores the image data from the binarization unit 14 based on this synchronization pulse.
[0024]
As shown in FIG. 3B, the ring buffer 16 includes a clock generator 16a, a pixel counter 16b, an image counter 16c, a counter buffer 16d, a multiplexer 16e, an image memory 16f, and a buffer 16g.
The clock generation unit 16a outputs a clock for counting the image data output from the binarization unit 14 on a pixel basis to the pixel counter 16b based on the synchronization pulse from the synchronization pulse generation unit 15 described above.
[0025]
The pixel counter 16b counts the clock signal from the clock generator 16a. The pixel counter 16b counts an image of a predetermined area captured by the CCD sensor of the image capturing unit 13 in units of pixels, and the image of the predetermined area is composed of m horizontal pixels and n vertical pixels. Then, “1” to “m × n” are repeatedly counted. The count value is output to the multiplexer 16e. Further, a reset signal is output to the image counter 16c at the timing of resetting the counter value.
[0026]
The image counter 16c counts image numbers, and repeatedly counts “1” to “6” based on a reset signal from the pixel counter 16b. Then, the count value is output to the counter buffer 16d and the multiplexer 16e.
[0027]
The counter buffer 16d holds the count value from the image counter 16c. This count value (image number) can be read out by the data processing unit 11. Thus, the data processing unit 11 can know the image number of the image being captured in the image memory 16f.
[0028]
As described above, the multiplexer 16e receives the count value of the pixel counter 16b and the count value of the image counter 16c. The multiplexer 16e generates an address of the image memory 16f based on these count values. The image data from the binarization unit 14 is stored in the address of the image memory 16f calculated by the multiplexer 16e via the buffer 16g. Therefore, the image memory 16f is configured as a memory device capable of storing six images of image numbers 1 to 6. Hereinafter, the image of the image number x is described as “image x”.
[0029]
The image data stored in the image memory 16f can be read by the data processing unit 11 via the buffer 16g. At this time, the data processing unit 11 outputs a read instruction to the multiplexer 16e and designates an image number.
[0030]
Next, the operation of the two-dimensional code reader 10 of this embodiment configured as described above will be described.
In the two-dimensional code reader 10 of this embodiment, images are repeatedly captured at predetermined time intervals by the image capturing unit 13 and stored in the image memory 16f of the ring buffer 16 described above. FIG. 4A conceptually shows the image memory 16f.
[0031]
Assuming that an image captured at a certain point in time is image 1, the next captured image is stored as image 2, and similarly, image 3 → image 4 → image 5 → image 6 is stored. The image captured next to the image 6 is stored again as the image 1. As a result, six images that are new in time are stored in the image memory 16f.
[0032]
In this embodiment, the optical information recording surface 71b of the article 71 is captured as a plurality of images by the image capturing unit 13, but the relationship between the images 1 to 6 and the optical information recording surface 71b is exemplified. It is FIG.4 (b). In FIG. 4B, the optical information recording surface 71b is imaged with images 5, 6, 1, 2, and 3. In the present embodiment, the optical information recording surface 71b is recorded as at most five images from the relationship between the length in the longitudinal direction of the optical information recording surface 71b and the imaging interval.
[0033]
At this time, the data processing unit 11 specifies these five images based on the signal from the article detection unit 12, performs decoding processing on these five images, and records the QR recorded on the optical information recording surface 71b. Decode the code. Next, the decoding process executed by the data processing unit 11 will be described based on the flowchart of FIG.
[0034]
First, it is determined whether or not an article is detected in the first step (hereinafter, the step is simply indicated by symbol S) 100. This process is based on the signal from the article detection unit 12 to determine that the front end surface 71a of the article 71 has reached the position α in FIG. If an article is detected here (S100: YES), the process proceeds to S110. On the other hand, this determination process is repeated until the article is not detected (S100: NO).
[0035]
In S110, it is determined whether or not a predetermined time has elapsed. In this process, it is assumed that the speed of the belt conveyor 70 is substantially constant, and it is determined whether or not the front end surface 71a of the article 71 has moved to a position indicated by symbol β in FIG. 2 (hereinafter referred to as “position β”). To do. From the positional relationship with the optical system, when the front end surface 71a moves to the position β, an image of the substantially central portion of the optical information recording surface 71b is taken. If it is determined in S110 that the predetermined time has elapsed (S110: YES), the process proceeds to S120. On the other hand, as long as the predetermined time has not elapsed (S110: NO), this determination process is repeated.
[0036]
In S120, a reference image, which is an image at the center of the optical information recording surface 71b, is specified by an image number. This is a process of acquiring the value (image number) of the counter buffer 16d of the ring buffer 16.
In subsequent S130, it is determined whether the necessary number of images have been captured by reading the value of the counter buffer 16d. In this process, it is determined whether or not all the images that may be recorded on the optical information recording surface 71b are captured among the images captured after the reference image. In this embodiment, since the reference image and two images before and after the reference image are to be decoded, the determination is affirmed when the reference image is captured and two more images are captured. If it is determined that the necessary number of images have been captured (S130: YES), the process proceeds to S140. On the other hand, this determination process is repeated until the required number of images is not captured (S130: NO).
[0037]
In S140, image storage is stopped. This process outputs a read instruction to the multiplexer 16e. As a result, the multiplexer 16e switches to the read operation, and the image data from the binarization unit 14 is not stored in the image memory 16f.
[0038]
In subsequent S150, the image number is output to the multiplexer 16e, and the image to be decoded is read out. In the present embodiment, as described above, two images before and after the reference image are read out.
In the next S160, decoding processing is performed on the read image. Here, as is well known, decoding is performed by specifying the position of the QR code in the image. At this time, if the QR code is stored across two images, the two images are synthesized and decoded.
[0039]
The position of the QR code can be specified based on the positioning symbol provided in the QR code. In brief, as shown in FIG. 6, the QR code has three positioning symbols A, C, and D. When reading the QR code, first, the three positioning symbols A, C, and D are detected. The positioning symbols A, C, and D have a specific ratio of 1 (dark): 1 (bright): 3 (dark): 1 (bright): 1 (dark) regardless of the scanning direction. It is a pattern. Therefore, it is possible to detect the positioning symbols A, C, and D by scanning the image data and determining that the specific ratio has been reached. Since the QR code has timing cells E and F in which bright and dark cells are alternately arranged between the positioning symbols A, C, and D, the QR code further includes other cells from the center position of the timing cell. The center position is determined.
[0040]
The decoding process as described above will be specifically described in the case where the optical information recording surface 71b is imaged as shown in FIG. At this time, as shown in FIG. 4A, the article is detected while the image 6 is being captured (S100). Then, the elapse of a predetermined time is determined (S110), and the reference image is specified based on the value of the counter buffer 16d (S120). In this example, image 1 is the reference image. Thereafter, when the two images 2 and 3 are captured, that is, when the value of the counter buffer becomes “4”, image storage is stopped (S140). Then, two images before and after the reference image, ie, image 1, ie, images 5, 6, 1, 2, and 3, are read (S150), and QR code decoding is performed (S160). To decode the QR code, first, the position of the QR code is specified from the positioning symbol. At this time, if there is an image including the entire QR code (image 1 if it is in symbol B, image 2 if it is in symbol C), the QR code is decoded using that image. On the other hand, as indicated by symbol A, if the QR code spans two images, the two images (images 5 and 6 if symbol A) are combined and the QR code is decoded.
[0041]
Next, effects exhibited by the two-dimensional code reader 10 of the present embodiment will be described.
In the two-dimensional code reader 10 of this embodiment, the image capturing unit 13 captures images at regular time intervals, stores them in the image memory 16f of the ring buffer 16, and based on the article detection time (S100 in FIG. 5). ), The image in the image memory 16f is read (S150), and the QR code is decoded (S160). Therefore, even when the position of the QR code attached to the article is misaligned, the QR code can be taken in and decoded, and further, the restriction on the arrangement relationship between the image fetching unit 13 and the article detecting unit 12 can be eliminated. it can.
[0042]
Specifically, if the predetermined time of S110 in the decoding process (the predetermined time may be “0”) and the required number of S130 are changed, the optical information recording surface 71b is imaged as shown in FIG. In this case, it is only necessary that the article can be detected between the time when the image 5 in FIG. 4A starts to be captured and the time when the image 4 is captured. This is because the images 5, 6, 1, 2, and 3 can be read out. Therefore, the article detection unit 12 can be moved within the range, and the restriction can be eliminated.
[0043]
Therefore, as the number of images to be captured is increased, there is no restriction on the arrangement relationship between the article detection unit 12 and the image capture unit 13.
Conventionally, since an article is detected and then an image is captured, it is necessary to always place the article detection unit 12 in front of the field of view of the CCD sensor, which hinders downsizing of the apparatus. On the other hand, in the two-dimensional code reader 10 of the embodiment, the article is detected behind the field of view of the CCD sensor of the image capturing unit 13.
[0044]
Further, in this embodiment, six images are taken into the image memory 16f of the ring buffer 16, but only an image obtained by imaging the optical information recording surface 71b is read out as a decoding target. In other words, only images that may have QR codes recorded are read out and subjected to decoding. Therefore, the decoding processing time does not depend on the number of images fetched into the image memory.
[0045]
Furthermore, in the present embodiment, when the required number of images is captured (S130: YES in FIG. 5), the image storage is stopped (S140). As a result, even if time is required for decoding (S160), the image is not overwritten in the image memory 16f. As a result, it is not necessary to improve the performance of the data processing unit 11 in accordance with the capturing interval of the image capturing unit 13, and the present two-dimensional code reading device 10 becomes inexpensive.
[0046]
In the present embodiment, the position of the QR code is obtained, and if the QR code is captured across two images, the images are combined and the QR code is decoded. Thereby, the QR code can be reliably decoded.
In the present embodiment, the image capturing unit 13 corresponds to an “image capturing unit”, the ring buffer 16 corresponds to an “image storage control unit”, the article detection unit 12 corresponds to a “detecting unit”, and data The processing unit 11 corresponds to “processing execution means”. The decoding processing shown in FIG. 5 corresponds to processing as processing execution means.
[0047]
As described above, the present invention is not limited to such embodiments, and can be implemented in various forms without departing from the spirit of the present invention.
For example, the above embodiment is an apparatus for reading a QR code, but may be an apparatus for reading a two-dimensional code other than the QR code. Needless to say, the present invention is not limited to a two-dimensional code, and can be applied to a device that reads a one-dimensional code such as a barcode or a character code.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an entire system including a two-dimensional code reader according to an embodiment.
FIG. 2 is a schematic perspective view of FIG. 1 viewed from a direction indicated by a symbol K in FIG.
FIG. 3A is a block diagram showing a configuration of a two-dimensional code reader, and FIG. 3B is a block diagram showing a configuration of a ring buffer.
4A is a conceptual diagram of an image memory, and FIG. 4B is an explanatory diagram illustrating a state in which an optical information recording surface is captured as a plurality of images.
FIG. 5 is a flowchart showing a decoding process.
FIG. 6 is an explanatory diagram showing a QR code.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Two-dimensional code reader 11 ... Data processing part 12 ... Article detection part 13 ... Image capture part 14 ... Binarization part 15 ... Synchronization pulse generation part 16 ... Ring buffer 16a ... Clock generation part 16b ... Pixel counter 16c ... Image counter 16d ... Counter buffer 16e ... Multiplexer 16f ... Image memory 16g ... Buffer 70 ... Belt conveyor 71 ... Article 71a ... Tip surface 71b ... Optical information recording surface

Claims (2)

Receiving reflected light from an article moving on a conveyance path, capturing the optical information recording surface of the article as a plurality of images, and decoding an information code recorded on the optical information recording surface based on the captured images An optical information reader for reading information by:
Image capturing means for repeatedly capturing images at predetermined time intervals;
As images temporally new first predetermined number is stored in the image memory, an image storage control means for an image Ru is stored in the image memory to be captured by the image capturing means,
Detecting means for detecting that the article has arrived at a predetermined position on the conveyance path;
The said article by detecting means on the basis of article detection time of it is detected that comes to the predetermined position, the image stored in the image memory, processing execution means for performing a decoding process for decoding the information code and,
The process execution means includes
The image captured by the image capturing means after a predetermined time has elapsed from the article detection time as a reference image,
A second predetermined number of images less than the first predetermined number, including the reference image and images before and after the reference image, are read from the image memory;
By detecting a specified number of positioning symbols included in the information code, the position of the information code is specified from the read image,
An optical information reading apparatus that performs the decoding process on the specified information code . The optical information reader according to claim 1.
The process execution means combines the plurality of images when the prescribed number of positioning symbols is detected over a plurality of images, and performs the decoding process on the combined images. Equipment .

Images