JP4957616B2 - Two-dimensional code reader - Google Patents

Description

  The present invention relates to a two-dimensional code encoded in a light / dark module composed of a light module and a dark module, and a functional pattern required to decode the encoded data, and the data or information accompanying the data. And a two-dimensional code reader capable of reading a two-dimensional code including the data pattern.

  In a two-dimensional code reading device that reads a two-dimensional code encoded in a light / dark module, generally, a light receiving sensor whose signal level changes according to the intensity of light reflected on the two-dimensional code (corresponding to color shading or lightness). The sensor signal from is binarized by comparing with a predetermined threshold value to determine whether it is a light module or a dark module.

  If such a predetermined threshold is fixed to a predetermined value, when the change in light / darkness of the light / dark module is small, or when the entire two-dimensional code is dark, etc. Since the sensor signal is also above or below the threshold value, the sensor signal cannot be binarized properly.

  For this reason, as disclosed in Patent Document 1 below, there are some that are appropriately changed according to the state of the sensor signal. For example, in the first method disclosed in the [Prior Art] column of Patent Document 1, (1) a certain dead band width is provided above and below the threshold value, and a sensor signal outside this width falls within the dead band width. The threshold value is changed as follows. In the second method disclosed in the same column, (2) a maximum value and a minimum value of the sensor signal are appropriately determined, and an intermediate value thereof is set as a threshold value.

However, even if the method (1) is adopted, the dead zone width is a constant value, so it is not always possible to set an optimal threshold, and there is a range where the change in brightness is poor even if the method (2) is adopted. If it is wide, there is a problem that it is difficult to set an appropriate threshold even if it is an intermediate value. For this reason, Patent Document 1 proposes a technique for adaptively calculating the dead band width according to the maximum value and the minimum value of the sensor signal (grayscale signal) and setting the threshold value based on the dead band width.
JP-A-11-53459

  However, even with the technique disclosed in Patent Document 1, the dead band width is obtained based on the maximum value and the minimum value of the sensor signal (grayscale signal), and the threshold value is made to follow the sensor signal using this dead band width. . For this reason, for example, if noise is mixed in the power supply line of the two-dimensional code reader, the sensor signal may be affected by the fluctuation of the power supply voltage and may be a jagged waveform in some cases. It is difficult to set an appropriate threshold value with the dead band width based on such a sensor signal.

  In other words, the technique disclosed in Patent Document 1 does not employ a configuration that can remove noise components from a power source or the like that can be included in a sensor signal. There is a problem that you can not.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a two-dimensional code reader that can accurately binarize even if power supply noise or the like is mixed. .

  In order to achieve the above object, in the two-dimensional code reader according to claim 1, the coded two-dimensional code is encoded in the light / dark module composed of the light module and the dark module. In a two-dimensional code reader capable of reading a two-dimensional code including a functional pattern required to decode the received data and a data pattern obtained by encoding the data or information accompanying the data, Code image storage means for storing a plurality of code images acquired at different timings for the same two-dimensional code in the code image, and included in this one code image based on one code image stored in the code image storage means Function pattern detecting means for detecting the function pattern to be detected, and detecting the function pattern. A first decoding means for decoding the data pattern included in the one code image using a first threshold value set to determine the brightness of the light / dark module; and the data by the first decoding means. Decoding success / failure determining means for determining whether or not the pattern has been decoded; and when the decoding success / failure determining means determines that the data pattern has not been decoded, the code image stored in the code image storage means is In each image data constituting the image data, the degree of lightness and darkness expressed numerically for each pixel is added for a predetermined image of the plurality of code images, and an addition code image is generated based on the addition image data obtained by the addition. Based on the code image addition means and the addition code image generated by the code image addition means, Threshold setting means for setting a second threshold for discriminating the brightness of the brightness module, and second decoding means for decoding the data pattern included in the addition code image using the second threshold. It is a technical feature to provide.

  The “module” is a minimum component constituting the two-dimensional code, and the “bright module” is a light color (for example, a color with high brightness such as white) and a dark color (for example, black). Is a light color module in the case where the module is configured with two types of light color), and the “dark module” refers to a dark color module when the module is configured with two types of light color and dark color. That is.

  The two-dimensional code reader according to claim 2, wherein the code image storage means performs logical operation on each image data constituting the plurality of code images. A technical feature is that it is an annular storage device that can be stored cyclically.

  The two-dimensional code reading device according to claim 3, wherein the threshold value setting means is arranged in a row of pixels constituting the addition code image. An increase / decrease change amount of the added image data for each pixel arranged side by side is subjected to a second derivative operation, and the second image obtained as a result of the second derivative value is set to the second threshold value. Technical features.

  In the two-dimensional code reading device according to claim 4, the threshold value setting means is arranged in a row with pixels constituting the addition code image. A technical feature is that an average value obtained by dividing the sum of the added image data for each pixel arranged side by side by the number of pixels constituting the column is set as the second threshold value.

  In the two-dimensional code reader according to claim 5, the code image adding means includes a unit for the predetermined image. An adder having a number of images equal to or greater than ½, and performing the addition operation for each pixel of the predetermined image almost simultaneously to obtain the added image data to obtain the added code Generating an image is a technical feature.

  In the two-dimensional code reading device according to claim 6, the code image adding means is configured to output the added image data as the two-dimensional code reading device according to any one of claims 1 to 4. The oldest image data of the image data for the predetermined image used for obtaining is removed from the added image data, and the newest image data is added to the added image data to obtain new added image data. Generating an image is a technical feature.

  According to the first aspect of the present invention, the code image storage means stores a plurality of code images acquired at different timings for the same two-dimensional code in the code image of the two-dimensional code, and the function pattern detection means stores the code image in the code image storage means. A function pattern included in the one code image is detected based on the stored one code image, and the first decoding unit is set to determine the brightness of the light / dark module when detecting the function pattern. The data pattern included in one code image is decoded using the threshold value. When the decoding success / failure determining means determines whether or not the data pattern can be decoded by the first decoding means, and when the decoding success / failure determining means determines that the data pattern cannot be decoded, the code image adding means Thus, the image data stored in the code image storage means that represents the numerical value of the degree of lightness and darkness for each pixel in the image data is obtained by adding a predetermined image of the plurality of code images. An addition code image is generated based on the addition image data, a second threshold for determining the brightness of the light / dark module is set by the threshold setting means based on the addition code image generated by the code image addition means, and the second The data pattern included in the addition code image is decoded using the second threshold.

  As a result, when it is determined that the data pattern cannot be decoded, each image data constituting the code image stored in the code image storage means numerically expresses the degree of brightness for each pixel. Since a predetermined number of code images are added and an addition code image is generated based on the addition image data obtained by the addition, for example, a part of the code image is disturbed due to temporary mixing of power noise or the like. However, by adding a predetermined number of images before and after that, it is possible to compensate for the disturbance of some of the code images by other code images not affected by power supply noise or the like (to reduce image disturbances). it can). Therefore, since the data pattern included in the addition code image is decoded using the second threshold value based on the addition code image in which the disturbance of the code image is reduced in this way, even if power supply noise or the like is mixed, the data pattern is accurately detected. Can be priced.

  In the invention of claim 2, since the code image storage means is an annular storage device capable of storing each image data constituting a plurality of code images in a logical (endless) manner, it is logically circular. Compared with a non-endless storage device, it is difficult to create a useless empty area (fragment). Thereby, the storage device can be used effectively.

  In the invention of claim 3, the threshold setting means is exemplified. For example, addition image data in which the secondary differential value obtained as a result of second-order differential calculation of the increase / decrease change amount of the addition image data for each pixel arranged adjacent to each other in a row with pixels constituting the addition code image becomes zero Is set to the second threshold. Thereby, the maximum value or the minimum value of the added image data can be set as the second threshold value.

  In the invention of claim 4, the threshold setting means is exemplified. For example, the average value obtained by dividing the sum of the added image data for each pixel arranged adjacent to each other in a column with pixels constituting the addition code image by the number of pixels constituting the column is set as the second threshold value. To do. Thereby, as a threshold value setting means, the second threshold value can be set with a simple calculation algorithm as compared with the case where the second derivative value is obtained by performing a second derivative operation and set as the second threshold value.

  In the invention of claim 5, the code image addition means includes an adder that is at least half the number of images for a predetermined image, and operates them in parallel to perform an addition operation for each pixel of the predetermined image. By performing substantially the same time, addition image data is obtained and an addition code image is generated. Thereby, it is possible to speed up the arithmetic processing as compared with the case where the addition operation is not performed in parallel (the addition operation is performed in series).

  In the invention of claim 6, the code image adding means removes the oldest image data from the added image data and outputs the newest image data to the added image from among the image data for a predetermined image used for obtaining the added image data. In addition to the data, new addition image data is obtained and an addition code image is generated. As a result, the addition image data can be updated by performing the subtraction process excluding the old image data and the addition process adding the new image data, so that the calculation process is performed in comparison with the case of adding all the image data to be added each time. Can be faster.

  Hereinafter, an embodiment in which the two-dimensional code reader of the present invention is applied to a two-dimensional code reader 20 capable of reading a QR code will be described with reference to the drawings. In this embodiment, a QR code is described as an example of a two-dimensional code. However, the coded data is represented by a two-dimensional code coded in a light / dark module composed of a light module and a dark module. For example, a data matrix code, a maxi code, a veri code, a color code, and the like can be used as long as it is a two-dimensional code that records a function pattern required for decoding and a data pattern obtained by encoding the data or information accompanying the data. The present invention can also be applied to codes, CP codes, and the like.

  First, the configuration of the two-dimensional code reader 20 will be described with reference to FIG. As shown in FIG. 1, the two-dimensional code reader 20 mainly includes an optical system such as an illumination light source 21, a light receiving sensor 23, and an imaging lens 22, a memory 35, a control circuit 40, an operation switch 42, and a liquid crystal display 46. And a power supply system such as a power switch 41 and a battery 49. These are mounted on a printed circuit board (not shown) and accommodated in a housing (not shown).

  The optical system includes an illumination light source 21, a light receiving sensor 23, an imaging lens 22, and the like. The illumination light source 21 functions as an illumination light source capable of emitting illumination light Lf, and includes, for example, a red LED and a diffusion lens, a condensing lens, and the like provided on the emission side of the LED. In the present embodiment, illumination light sources 21 are provided on both sides of the light receiving sensor 23, and configured to be able to irradiate illumination light Lf toward the label P through a reading port of a housing (not shown). On this label P, a QR code Q is printed.

  The light receiving sensor 23 is configured to receive the reflected light Lr irradiated and reflected on the label P or the QR code Q. For example, a light receiving element which is a solid-state imaging element such as a C-MOS or CCD is two-dimensionally arranged. The arranged area sensor corresponds to this. The light receiving sensor 23 is mounted on a printed circuit board (not shown) so that incident light incident through the imaging lens 22 can be received by the light receiving surface 23a.

  The imaging lens 22 functions as an imaging optical system capable of condensing incident light incident through the reading port from the outside and forming an image on the light receiving surface 23a of the light receiving sensor 23. And a plurality of condensing lenses housed in the lens barrel.

  Next, a configuration outline of the microcomputer system will be described. The microcomputer system includes an amplification circuit 31, an A / D conversion circuit 33, a ring buffer circuit 34, a memory 35, an address generation circuit 36, a synchronization signal generation circuit 38, a control circuit 40, an operation switch 42, an LED 43, a buzzer 44, and a liquid crystal display. 46, a communication interface 48, and the like. As the name suggests, this microcomputer system is composed of a control circuit 40 and a memory 35 that can function as a microcomputer.

  An image signal output from the light receiving sensor 23 of the optical system is amplified by a predetermined gain by being input to the amplification circuit 31 and then converted from an analog signal to a digital signal when input to the A / D conversion circuit 33. Is done. For example, when the light module of QR code Q is composed of “white” and the dark module is “black”, when converting gray scale to 256 bits of 8-bit, “black” is 0 for each module. , “White” is converted to 255, and “gray” in between is converted to 1 to 254 according to the lightness. The image data thus converted (digitized image signal) is input to the memory 35 and stored in the image data storage area. In parallel with this, the image data is also input to and accumulated in a ring buffer circuit 34 described later.

  The synchronization signal generation circuit 38 is configured to be able to generate synchronization signals for the light receiving sensor 23, the ring buffer circuit 34, and the address generation circuit 36. The address generation circuit 36 is supplied from the synchronization signal generation circuit 38. The storage address of the image data stored in the ring buffer circuit 34 or the memory 35 can be generated based on the synchronization signal.

  The ring buffer circuit 34 is an annular storage device that can logically store the image data output from the A / D conversion circuit 33. The ring buffer circuit 34 stores the image data based on the synchronization signal supplied from the synchronization signal generation circuit 38. I remember it. A configuration example of the ring buffer circuit 34 is shown in FIG. 2 and will be described with reference to FIG.

  As shown in FIG. 2, the ring buffer circuit 34 includes a clock control unit 34a, a pixel counter 34b, a screen number counter 34c, a multiplexer 34d, a latch 34e, an image memory 34f, a buffer 34g, and the like.

  The clock control unit 34 a generates and outputs a clock signal for counting image data output from the A / D conversion circuit 33 on a pixel basis based on the synchronization signal from the synchronization signal generation circuit 38. . This clock signal is output to the pixel counter 34b.

  The pixel counter 34b counts the number of pixels for one screen (predetermined region imaged by the light receiving sensor 23) based on the clock signal output from the clock control unit 34a, and outputs the count value as data. The delimiter timing is output as a reset signal. For example, when the predetermined area is composed of pixels arranged in a matrix of m rows and n columns, “1” to “m × n” are repeatedly counted, and the count value is output to the multiplexer 34d. A reset signal is output to the screen number counter 34c.

  The screen number counter 34c receives the reset signal output from the pixel counter 34b and counts the image number within a predetermined range. For example, if the predetermined range is 64 screens, the screen number counter 34c repeatedly counts 1 to 64. The screen number counted as the count value by the screen number counter 34c is output to the multiplexer 34d and the latch 34e.

  The multiplexer 34d generates an image memory address of the image memory 34f based on the count value input from the pixel counter 34b and the screen number input from the screen number counter 34c, and outputs the image memory address to the image memory 34f. The image memory address is also output to the latch 34e.

  The latch 34e is configured to hold the screen number input from the screen number counter 34c and to output the held image number to the control circuit 40, that is, to be able to read from the control circuit 40. As a result, the control circuit 40 can acquire the image number of the image data being taken into the image memory 34f described below.

  The image memory 34f is a semiconductor memory device capable of storing a predetermined number of image data, and stores image data sent from the A / D conversion circuit 33 through a buffer 34g described below for a plurality of images. . For example, when the count range by the screen number counter 34c is for 64 screens, the image memory 34f is configured to be able to store image data for 64 images as a predetermined number.

  The buffer 34g is a semiconductor memory device that stores the image data sent from the A / D conversion circuit 33 and the image data output to the control circuit 40. The buffer 34g is connected to the A / D conversion circuit 33, the control circuit 40, and the image memory. Image data is exchanged with 34f. The buffer 34g has a smaller storage capacity than the image memory 34f, but is configured so that writing and reading can be performed at high speed.

  By configuring the ring buffer circuit 34 in this way, the ring buffer circuit 34 functions as an annular storage device (endless storage device) capable of logically storing in a circular manner as shown in FIG. . For example, an image captured at a certain time and sent from the A / D conversion circuit 33 is No. Assuming one image, the next captured image is No. 2 images, the next captured image is No. 3 images are stored in order, and the nth stored image is No. n images (No. 64 image in the above example) are stored, and the (n + 1) -th stored image is again No. One image is stored.

  As a result, the image data of n images (64 images in the previous example) that are new in time are stored in the buffer 34g. The ring buffer circuit 34 stores image data including a plurality of code images acquired at different timings for the same QR code Q in the QR code Q code image. It can correspond to a “code image storage means”. An annular storage device that can be logically stored in a circular manner by the ring buffer circuit 34 may be simply referred to as a “ring buffer”.

  The memory 35 is a semiconductor memory device, and corresponds to, for example, a RAM (DRAM, SRAM, etc.) or a ROM (EPROM, EEPROM, etc.). In addition to the above-described image data storage area, the RAM of the memory 35 is configured so as to be able to secure a work area used by the control circuit 40 during each processing such as arithmetic operation and logical operation. In addition, the ROM stores in advance a predetermined program capable of executing a decoding process described later, a system program capable of controlling each hardware such as the illumination light source 21 and the light receiving sensor 23, and the like.

  The control circuit 40 is a microcomputer that can control the entire two-dimensional code reader 20, and includes a CPU, a system bus, an input / output interface, and the like. The control circuit 40 is configured to be connectable to various input / output devices via a built-in input / output interface. In the case of this embodiment, the power switch 41, operation switch 42, LED 43, buzzer 44, liquid crystal. A display 46, a communication interface 48, and the like are connected.

  Thereby, for example, monitoring and management of the power switch 41 and the operation switch 42, turning on / off the LED 43 functioning as an indicator, turning on / off the buzzer 44 capable of generating a beep sound and an alarm sound, and further reading the QR code This makes it possible to control the screen of the liquid crystal display 46 capable of displaying the code content by the communication, the communication control of the communication interface 48 enabling serial communication with an external device, and the like. The external devices connected to the communication interface 48 include a host computer HST corresponding to the host system of the two-dimensional code reader 20 and the like.

  The power supply system includes a power switch 41, a battery 49, and the like. When the power switch 41 managed by the control circuit 40 is turned on and off, the conduction of the drive voltage supplied from the battery 49 to each of the above-described devices and circuits is performed. Or shut off is controlled. The battery 49 is a secondary battery capable of generating a predetermined DC voltage, and corresponds to, for example, a lithium ion battery. Further, the battery 49 may be configured to receive power supply from an external device such as the host computer HST connected via the communication interface 48 without using the battery 49. In this case, the battery 49 is unnecessary.

  By configuring the two-dimensional code reader 20 in this manner, for example, when the power switch 41 is turned on and a predetermined self-diagnosis process or the like is normally completed and the QR code Q can be read, the illumination light Lf An input of an operation switch 42 (for example, a trigger switch) that instructs light emission is received. Accordingly, when the user of the two-dimensional code reader 20 pulls the trigger switch to turn it on, the control circuit 40 outputs the light emission signal to the illumination light source 21 based on the synchronization signal, and thus receives the light emission signal. The illumination light source 21 emits the LED and emits illumination light Lf.

  Then, the illumination light Lf irradiated to the QR code Q is reflected, and the reflected light Lr enters the imaging lens 27 through the reading port, so that the image of the QR code Q is formed on the light receiving surface 23a of the light receiving sensor 23. Is imaged. As a result, the image of the QR code Q exposes the light receiving sensor 23, so that the image data of the QR code Q processed by the microcomputer system is stored in the image data storage area of the memory 35 and the ring buffer. The circuit 34 is also stored sequentially as described above.

  The control circuit 40 acquires image data via the memory 35 when executing the reading process described below, or in some cases, acquires necessary image data from the ring buffer circuit 34 and is necessary for reading. The threshold value is reset and the reading process is performed.

  Here, the flow of the reading process will be described with reference to FIGS. 3 to 8. In this reading process, a threshold necessary for reading is set when detecting the function pattern of the QR code. Prior to the description, the basic structure of the QR code will be described with reference to FIG. Note that the QR code Q shown in FIG. 4 is configured such that the bright module is “white” and the dark module is “black”.

  As shown in FIG. 4, the QR code Q is configured substantially in accordance with the basic specifications of the QR code (Japanese Industrial Standard; JIS X 0510: 2004, hereinafter simply referred to as “JIS standard”). The function pattern includes a finder pattern FP, an alignment pattern AP, a timing pattern TP, and the like, and a data pattern DP. FIG. 4 shows an example conforming to the JIS standard type 2 (25 × 25 module).

  The finder pattern FP is also referred to as a cutout symbol or an alignment pattern, and is an aggregate of a plurality of unit modules arranged in squares located at three corners of the QR code Q, that is, an n × n module. It is configured and recorded so that the position, size, and inclination of the code can be detected. Specifically, for example, a 3 × 3 dark module in which black unit modules are arranged in a matrix of 3 rows and 3 columns, and a 5 × in which white unit modules are arranged in a matrix of 5 rows and 5 columns so as to surround them. It is composed of a 5-light module and a 7 × 7 dark module in which black unit modules are arranged in a matrix of 7 rows and 7 columns so as to surround them.

  For this reason, when light / dark information is scanned so as to traverse or longitudinally cross the finder pattern FP, the continuous ratio of modules of the same color becomes 1: 1: 3: 1: 1 in the order of dark, bright, dark, bright, dark. Utilizing this, the image range is the finder pattern FP and the center position of the finder pattern FP is detected. That is, the QR code Q can be detected in all directions of 360 degrees by the finder pattern FP.

  The alignment pattern AP is also an assembly of a plurality of unit modules arranged in a square, and is recorded so as to be able to correct the distortion of the QR code. The alignment pattern AP is a predetermined area within the square range defined by the three finder patterns FP. Located in the place. Specifically, for example, a black 1 × 1 dark module for one unit module, eight white 3 × 3 bright modules surrounding the 1 × 1 dark module, and this square 3 × It consists of 16 black 5 × 5 dark modules surrounding the 3 light module. This alignment pattern AP facilitates detection of the center coordinates.

  The timing pattern TP is a repeating pattern of unit modules in which white and black unit modules appear repeatedly, which enables timing extraction for obtaining the center coordinates of each unit module. The white 1 × 1 bright module and the black 1 × One dark module is alternately arranged in a straight line. For example, when the QR code Q is distorted or there is an error in the pitch of the unit module, it is used to correct the center coordinates of the unit module. The timing pattern TP is recorded in each of the vertical direction and the horizontal direction of the QR code Q so as to pass through the center of the alignment pattern AP.

  For example, as shown in FIG. 4, the data pattern DP is configured by arranging unit modules in 4 rows and 2 columns, so that data of 8 bits from bit 0 to bit 7 can be expressed. . The data pattern DP is recorded in a data pattern area other than the function pattern area in which the finder pattern FP, the alignment pattern AP, and the timing pattern TP are arranged.

  A quiet zone QZ having a width of 4 modules (4 unit modules) is secured around the QR code Q because the two-dimensional code reader 20 needs to recognize the outline and presence of the finder pattern FP. Yes.

  In the two-dimensional code reader 20 according to the present embodiment, the QR code Q configured as described above is decoded by the reading process shown in FIG. That is, as shown in FIG. 3, first, a code image acquisition process is performed in step S101. In this process, image data stored in the image data storage area of the memory 35 is read.

  In step S103, position detection pattern detection processing is performed. That is, the image data read in step S101 is virtually scanned on the memory 35 so as to traverse or longitudinally cross, and a predetermined threshold value (first threshold value) set in advance at the time of factory shipment or the like is used as a reference. The light / dark information is determined.

  For example, when the image data is composed of 256 gradations of 8 bits, the predetermined threshold is set to 120, which is slightly smaller than the intermediate value (128) of 0 to 255. A module having a value equal to or smaller than the predetermined threshold (0 to 128) is determined as a dark module (black), and a module having a value (129 to 255) larger than the predetermined threshold is determined as a bright module (white). Then, as described with reference to FIG. 4, by detecting a range in which the continuous ratio of the same color module is 1: 1: 3: 1: 1 in the order of dark, bright, dark, bright, dark. The image range is the finder pattern FP and the center position of the finder pattern FP, that is, the position detection pattern is detected.

  Note that the image data read in step S101 can correspond to “one code image” recited in the claims, and the position detection pattern detection processing in step S103 is performed according to “ This can correspond to “functional pattern detection means”. In the present embodiment, the finder pattern FP is given as an example of the function pattern detected in step S103. However, the alignment pattern AP and the timing may be used as long as the pattern is necessary for decoding the data encoded in the QR code Q. The pattern TP may be a detection target in step S103.

  In subsequent step S105, processing for determining whether or not the position detection pattern has been detected in step S103 is performed. If it is determined that the position detection pattern cannot be detected (S105; No), the process proceeds to step S125, assuming that the image data read in step S101 does not include the QR code Q. Then, error information output processing described later is performed. On the other hand, when it is determined in step S105 that the position detection pattern has been detected (S105; Yes), black and white determination processing is performed in subsequent step S107.

  In the monochrome determination process in step S107, the data pattern DP is determined in the same manner as in step S103 described above with reference to the predetermined threshold (first threshold) used when the finder pattern FP (position detection pattern) is detected in step S103. And the like (for example, 8-bit 256 gradation) are discriminated, and the code image is decoded in the subsequent step S109 based on the light / dark information. The decoding process in step S109 is performed according to the JIS standard and can correspond to the “first decoding unit” recited in the claims.

  In the subsequent step S111, processing is performed to determine whether or not the decoding in step S109 has been successful, that is, whether or not the decoding has been normally performed. As a result, if the decoding is successful (S111; Yes), the predetermined threshold (first threshold) used in the decoding in step S109 has no problem with the QR code Q. Then, the process proceeds to the decoding result output process in step S131, and the decoding result is output to the liquid crystal display 46, or is output to the host computer HST via the communication interface 48. On the other hand, if the decoding has not succeeded (decoding has failed) (S111; No), a code image cut-out process is performed in step S113. The determination process in step S111 can correspond to “decoding success / failure determination means” described in the claims.

  In the code image cut-out process in step S113, the image data of QR code Q, that is, the code image is cut out from each image data stored in the image memory 34f of the ring buffer circuit 34 in order. The cutout range is set based on the above-described QR code Q finder pattern FP, for example.

  In the subsequent step S115, a code image addition process is performed. In this process, the code image cut out in step S113 is added for each module, and a new code image (added code image) is generated based on the image data (added image data) obtained by the addition. Note that the code image addition processing in step S115 can correspond to “code image addition means” recited in the claims.

  In step S117, processing for determining whether or not a predetermined number of code images has been added is performed. For example, in the previous example, the ring buffer circuit 34 has No. 1 image-No. Since 64 images are stored, when code images for 8 images (for example, No. 1 image to No. 8 image) are added from these, the predetermined number is 8 and 8 images have not been added yet. (S117; No), the process returns to step S113 to perform the code image cutting process again, and then performs the code image addition process in step S115.

  As a result, the addition processing in step S115 is repeated for the predetermined image, and thus the value increases for each module. For example, when the number of images to be cut out (hereinafter referred to as “number of cut out images”) is 8, The data of the modules constituting the code Q in the same position and added for 8 images cut out.

  For example, the image data corresponding to a certain module is 976 (= 105 + 100 + 110 + 134 + 131 + 129 + 135 + 132), that is, the image data itself is about eight times as much as one image (for example, eight images). On the other hand, when it is determined that a predetermined number of code images are added (S117; Yes), a threshold value calculation process in step S119 is performed.

  In step S119, a threshold value calculation process is performed. In this process, a process of setting a new threshold (second threshold) based on the code image added in steps S113 to S117, that is, the added code image is performed. The threshold value calculation process in step S119 can correspond to “threshold value setting means” described in the claims.

  For example, if the QR code Q shown in FIG. 4 is used as the QR code Q ′ of the addition code image, the addition is performed for each of the modules arranged side by side along the one-dot chain line arrow α shown in FIG. Then, a value obtained by dividing the sum by the number of modules constituting the column, that is, an average value is set as a threshold (second threshold) for the added code image. Alternatively, the threshold value for the addition code image is calculated by adding the pixels obtained by adding together the pixels constituting the modules arranged adjacent to each other in a column along the one-dot chain line α, and dividing the sum by the number of pixels constituting the column. (Second threshold).

  The one-dot chain line arrow α shown in FIG. 4 is an example thereof, and for example, extends along a line extending in a direction orthogonal to this, or extends obliquely by 45 degrees with respect to the one-dot chain line arrow α. Modules and pixels arranged next to each other in a row in an arbitrary direction may be added as long as they are linear, such as a row along a line. In addition, this threshold value may be applied to the decoding of the addition code image obtained by calculating for an arbitrary column, or may be further averaged by calculating for an arbitrary plurality of columns. It may be applied to the decoding of the addition code image. Further, all the modules or pixels constituting the addition code image may be added, and the average value may be set as a threshold value (second threshold value) for the addition code image.

  While increasing the number of modules or pixels to be added, it is easy to obtain an appropriate threshold value for the added code image, but it takes time to perform the addition operation. On the other hand, as the number of modules or pixels to be added is decreased, the time required for the addition calculation process can be reduced and the processing time is increased, but on the other hand, it is difficult to obtain an appropriate threshold for the added code image. . For this reason, there is a trade-off relationship between the appropriate threshold for the added code image and the time for the threshold calculation process (S119).

  When the threshold value (second threshold value) for the addition code image is set in this way, in the subsequent step S121, the second decoding process is performed. The second decoding process in step S121 may correspond to the “second decoding means” recited in the claims.

  As the decoding process in step S121, for example, when the above-described average value is set as a threshold value, as shown in FIG. 5A, black and white (light / dark) is determined and decoded with respect to the added code image based on the threshold value. . The example shown in FIG. 5 (A) is for an addition code image obtained by adding 8 code images (FIG. 5 (A), upper figure: the data value of the addition code image is shown in the waveform), and the minimum value is 0. Since the threshold value is set to 980 with respect to (= 0 × 8) to the maximum value 2040 (= 255 × 8), the module or pixel constituting the addition code image has a value equal to or lower than this threshold value (0 to 980). If it is a module or pixel having a dark module or pixel (black), and if it is a module or pixel having a value (981 to 2040) larger than this threshold, it is determined that it is a bright module or pixel (white). (FIG. 5 (B) bottom; monochrome determination) and decoded.

  Then, in the subsequent step S123, a process for determining whether or not the decoding is successful, that is, whether or not the decoding is normally performed is performed. As a result, if the decoding is successful (S123; Yes), the process proceeds to the decoding result output process in step S131 to output the decoding result to the liquid crystal display 46, or via the communication interface 48 to the host computer HST. And the series of reading processing is terminated. On the other hand, if the decoding has not succeeded (decoding has failed) (S123; No), since the addition code image cannot be decoded, the error information output process in step S125 is performed, and then a series of steps are performed. The reading process ends.

  As the error information output process in step S125, for example, a message is output to the user of the two-dimensional code reader 20 that a reading error has occurred on the liquid crystal display 46, or a similar message is output to the communication interface 48. To the host computer HST.

  As described above, in the two-dimensional code reader 20 according to the present embodiment, the ring buffer circuit 34 stores a plurality of code images acquired at different timings for the same QR code Q in the QR code Q code image, The position detection pattern detection process (S103) by the control circuit 40 detects a finder pattern FP (functional pattern) included in the code image based on the code image (one code image) stored in the ring buffer circuit 34, By the first decoding process (S109) by the control circuit 40, a code image (one code) is used by using a predetermined threshold (first threshold) set in advance to determine the brightness of the brightness module when detecting the finder pattern FP. Data pattern DP included in (image) is decoded.

  If the decoding success / failure determination process (S111) by the control circuit 40 determines whether the data pattern DP has been decoded, and if it is determined that the data pattern DP has not been decoded (S111; No), By the code image addition processing (S115) by the control circuit 40, a plurality of image data constituting the code image stored in the ring buffer circuit 34, in which the degree of lightness and darkness is numerically expressed for each QR code Q module or pixel, A predetermined image (e.g., 8 images) of the code image is added and an added code image is generated based on the added image data obtained by the addition, and a control circuit is generated based on the generated added code image. Addition for discriminating the brightness of the module of QR code Q by the threshold value calculation process (S119) by 40 A threshold value (second threshold value) for the code image is set, and a data pattern included in the addition code image using the threshold value (second threshold value) for the addition code image by the second decoding process (S121) by the control circuit 40 Decode.

  Thereby, when it is determined that the data pattern DP could not be decoded (S111; No), a predetermined image (for example, 8 images) of the plurality of code images is added to the generated image data. Since the addition code image is generated on the basis of, for example, even if power supply noise or the like is temporarily mixed and a part of the code image is disturbed, the influence of the power supply noise or the like is obtained by adding the predetermined images before and after the code image. Other code images that have not been received can compensate for the disturbance of some of the code images (the image disturbance can be reduced).

  For example, if there is a code image disturbance in one of the eight images, if only one image is taken out, the influence of the disturbance is great. However, the other seven images without disturbance in the image data of such a code image Such disturbance is reduced by adding the image data including the image data. Therefore, by decoding the data pattern included in the addition code image using the second threshold value based on the added addition code image, even if power noise or the like is mixed, it can be binarized accurately. .

  In the two-dimensional code reader 20 according to the present embodiment, the ring buffer circuit 34 receives a plurality of code images by the clock control unit 34a, the pixel counter 34b, the screen number counter 34c, the multiplexer 34d, the latch 34e, and the image memory 34f. Since each configured image data can be stored logically (endlessly) in a circular manner (annular storage device), it is wasteful compared to a non-logically circular endless storage device such as the memory 35. Difficult free space (fragment). Thereby, the storage device can be used effectively.

  In the above-described embodiment, a threshold value (second threshold value) for the addition code image is set by the threshold value calculation process in step S119, and the second decoding process in step S121 is performed based on this threshold value. If the QR code Q shown in FIG. 4 is the QR code Q ′ of the addition code image, the increase / decrease change of the addition image data for each pixel arranged adjacent to each other in a row along the dashed line arrow α shown in FIG. A secondary differential calculation process for performing the secondary differential calculation on the quantity is provided instead of step S119, and as shown in FIG. 5B, the added secondary image data obtained as a result of the secondary differential value becomes 0 (zero). May be set to the second threshold.

  As a result, the maximum value or the minimum value of the added image data can be set as the second threshold value. For example, as shown in FIG. Where the secondary differential value changes from-(minus) to + (plus), where the secondary differential value is 0 (zero) and the immediately preceding secondary differential value changes from + (plus) to-(minus) Can be determined as black (dark), and the secondary differential value is 0 (zero), and the immediately preceding secondary differential value changes from + (plus) to-(minus). A section where the start point and the secondary differential value are 0 (zero) and the immediately preceding secondary differential value changes from − (minus) to + (plus) as the end point can be determined as white (bright).

  In the above-described embodiment, the code image is cut out by the code image cut-out process in step S113, and the code image addition process in step S115 is sequentially added until a predetermined number of code images are added (S117; No). An added code image is generated. Instead, a plurality of adders are provided with more than half of a plurality of code images (the number of images for a predetermined image) stored in the ring buffer circuit 34, and these are operated in parallel. The addition operation for each pixel of a predetermined image may be performed almost simultaneously.

  For example, 64 image addition code images A1, A2, A3, A4, A5, A6, A7, A8, B1, B2, B3, B4, B5, B6, B7, are stored in the image memory 34f of the ring buffer circuit 34. B8, C1, C2, C3, C4, C5, C6, C7, C8, D1, D2, D3, D4, D5, D6, D7, D8, E1, E2, E3, E4, E5, E6, E7, E8, F1, F2, F3, F4, F5, F6, F7, F8, G1, G2, G3, G4, G5, G6, G7, G8, H1, H2, H3, H4, H5, H6, H7, H8 are stored. If this is the case, 32 (= 64/2) adders for adding adjacent image data are provided.

  In FIG. 6, 32 of these 64 images are representative of addition code images A1, A2, A3, A4, A5, A6, A7, A8, B1, B2, B3, B4, B5, B6, B7, B8. On the other hand, a configuration in which eight adders AD1 to AD8 are connected to the image memory 34f is shown. Note that eight adders are added to the image memory 34f for the addition code images C1, C2, C3, C4, C5, C6, C7, C8, D1, D2, D3, D4, D5, D6, D7, and D8. Although connected, it is omitted in FIG.

  Here, the addition code image A1 and the addition code image A2 are added by the adder AD1, and the addition result is stored in the memory space of the predetermined address of the image memory 34f in which the addition code image A1 is stored. Connect the output. Further, the addition code image A3 and the addition code image A4 are added by the adder AD2, and the addition result is output from the adder AD2 so that the addition result can be stored in the memory space of the predetermined address of the image memory 34f in which the addition code image A2 is stored. Connect. Similarly, the addition code image A5 and the addition code image A6 are added by the adder AD3, and the addition result is stored in the memory space of the predetermined address of the image memory 34f in which the addition code image A3 is stored. Connect the output. Similarly, the addition code image A7 and the addition code image A8 are added by the adder AD4, and the addition result is stored in the memory space of the predetermined address of the image memory 34f in which the addition code image A4 is stored. Connect the output.

  Similarly, the addition code image B1 and the addition code image B2 are added by the adder AD5, and the addition result is stored in the memory space of the predetermined address of the image memory 34f in which the addition code image A5 is stored. Connect the output. Similarly, the addition code image B3 and the addition code image B4 are added by the adder AD6, and the addition result is stored in the memory space of the predetermined address of the image memory 34f in which the addition code image A6 is stored. Connect the output. Similarly, the addition code image B5 and the addition code image B6 are added by the adder AD7, and the addition result is stored in the memory space of the predetermined address of the image memory 34f in which the addition code image A7 is stored. Connect the output. Similarly, the addition code image B7 and the addition code image B8 are added by the adder AD8, and the addition result is stored in the memory space of the predetermined address of the image memory 34f in which the addition code image A8 is stored. Connect the output.

  Although not shown in FIG. 6, similarly to the addition code images C1, C2, C3, C4, C5, C6, C7, C8, D1, D2, D3, D4, D5, D6, D7, D8 However, similarly, eight adders are connected to the image memory 34f.

  Thus, for example, in the first stage, the addition code image A1 and the addition code image A2 are added by the adder AD1, and the addition code image A3 and the addition code image A4 are further added by the adder AD2 and the addition code image A5. The code image A6 is added by the adder AD3, the addition code image A7 and the addition code image A8 are added by the adder AD4, respectively, and the addition code image B1 and the addition code image B2 are added by the adder AD5. Image B3 and addition code image B4 are added by adder AD6, addition code image B5 and addition code image B6 are added by adder AD7, and addition code image B7 and addition code image B8 are added by adder AD8, respectively. To do. As a result, addition results (A1, A2), (A3, A4), (A5, A6), (A7, A8) are obtained, and a predetermined address of the image memory 34f in which the addition code images A1 to A4 are stored. Stored in the memory space.

  Next, in the second stage, the addition result (A1, A2) and the addition result (A3, A4) are added by the adder AD1, and the addition result (A5, A6) and the addition result (A7, A8) are added by the adder AD2. Thus, the addition result (B1, B2) and the addition result (B3, B4) are added by the adder AD3, and the addition result (B5, B6) and the addition result (B7, B8) are added by the adder AD4, respectively. Thereby, the addition results (A1, A2... A4), (A5, A6... A8) are obtained and stored in the memory space of the predetermined address of the image memory 34f in which the addition code images A1 to A4 are stored.

  Similarly, addition code images C1, C2, C3, C4, C5, C6, C7, C8, D1, D2, D3, D4, D5, D6, D7, D8 are also shown in the first stage and the second stage. Add with an abbreviated adder. Thereby, the addition results (C1, C2... C4), (C5, C6... C8) are obtained and stored in the memory space of the predetermined address of the image memory 34f in which the addition code images A5 and A6 are stored. The addition results (D1, D2... D4) and (D5, D6... D8) are obtained and stored in the memory space of the predetermined address of the image memory 34f in which the addition code images A7 and A8 are stored.

  After these additions, the addition results (A1, A2... A4) and the addition results (A5, A6... A8) are added to the addition results (B1, B2... B4) by the adder AD1 in the third stage. The result (B7, B6... B8) is added by the adder AD2, the addition result (C1, C2... C4) and the addition result (C5, C6... C8) are added by the adder AD3, and the addition result (D1, D2... D4). And the addition results (D7, D6... D8) are added by the adder AD4. Thereby, the addition results (A1, A2... A8), (B1, B2... B8), (C1, C2... C8), (D1, D2... D8) are obtained, and the addition code images A1 to A4 are stored. It is stored in the memory space of the predetermined address of the previously stored image memory 34f.

  Thereafter, in the fourth stage, the addition result (A1, A2... A8) and the addition result (B1, B2... B8) are added by the adder AD1, and the addition result (C1, C2... C4) and the addition result (D1, D2). ... D8) are added by the adder AD2, respectively, and addition results (A1 to A8, B1 to B8) and (C1 to C8, D1 to D8) are obtained, and the addition code images A1 and A2 are stored. The stored image memory 34f is stored in a memory space at a predetermined address.

  Finally, the addition results (A1 to A8, B1 to B8) and the addition results (C1 to C8, D1 to D8) are added by the adder AD1 in the fifth stage, so that all the addition results ( (ΣA, ΣB, ΣC, ΣD) are obtained and stored in a memory space of a predetermined address of the image memory 34f in which the addition code image A1 is stored.

  As a result, for example, when 32 code images are added and calculated by one adder, 31 calculation stages are required, but the addition can be performed at 5 calculation stages of 1/6 or less. . For this reason, the code image addition calculation processing can be dramatically speeded up. Further, even if 64 code images are added and calculated, they can be added in six calculation stages.

  The code image addition process is not performed every time for all the code images, but the image data of the oldest code image among the image data of the predetermined number of code images used for obtaining the added image data is used. The image data of the newest code image may be added to the added image data while being excluded from the added image data, and new added image data may be obtained to generate an added code image.

For example, as shown in FIG. 1 image-No. When the functional concept of the ring buffer circuit 34 capable of storing n code images of n images is expressed in a donut shape, no. (Nm−2) to No. The addition of 1 m code images is S _{(No. (n−m + 2) to No. 1 )} = (A ₁ + A _n +... + A _{n−m + 2} ) (see FIG. 7A). Here, A _x is No. It means image data of x image (code image). And No. (Nm−3) to No. 2 m code images are added by S _{(No. (n−m + 3) to No. 2 )} = (A ₂ + A _n +... + A _{n−m + 3} ) = A ₂ + (A ₁ + A _n +. _{n−m + 2} ) −A _{n−m + 2} = A ₂ + S _{(No. (n−m + 2) to No. 1)} −A _{n−m + 2} (see FIG. 7B).

Therefore, the image data A _n of the addition image data _{S (No. (n-m +} 2) ~No.1) adds the image data A ₂ of a new code image from oldest code image obtained by the previous addition operation By subtracting _{−m + 2} , it is possible to obtain an addition code image with less arithmetic processing without adding image data every time.

Further, instead of the process of subtracting the image data A _{n−m + 2} of the oldest code image, the inverted image data ¬A _{n in} which all the bits of the image data A _{n−m + 2} are inverted (0 → 1, 1 → 0) _An arithmetic addition operation may be performed by adding 1 to _{−m + 2} , that is, a logical addition operation of the two's complement of _{An−m + 2} (¬ is a symbol representing logic inversion). That is, no. (Nm−3) to No. The addition of m code images of 2 is as follows: S _{(No. (n−m + 3) to No. 2 )} = A ₂ + S _{(No. (n−m + 2) to No. 1)} −A _{n−m + 2} = A ₂ + S _{(No. (n−m + 2) to No. 1)} + ¬A _{n−m + 2} +1. By adding “1” to each image data, subtraction processing can be performed by the addition circuit, so that it is not necessary to provide a subtraction circuit, and the arithmetic circuit can be configured simply.

It is a block diagram which shows the structural example of the two-dimensional code reader which concerns on one Embodiment of this invention. It is a block diagram which shows the structural example of the ring buffer shown in FIG. It is a flowchart which shows the flow of the reading process by the two-dimensional code reader which concerns on this embodiment. It is explanatory drawing which shows the general structure of QR Code. It is explanatory drawing which shows the example of a setting of the threshold value with respect to a sensor signal. It is explanatory drawing which shows the concept and operation example of a parallel addition process. It is explanatory drawing which expressed the functional concept of the ring buffer circuit which can memorize | store n code images in donut shape.

Explanation of symbols

20 ... Two-dimensional code reader (two-dimensional code reader)
DESCRIPTION OF SYMBOLS 21 ... Illumination light source 22 ... Imaging lens 23 ... Light receiving sensor 31 ... Amplifying circuit 33 ... A / D conversion circuit 34 ... Ring buffer circuit (code image storage means, annular storage device)
35 ... Memory 36 ... Address generation circuit 41 ... Power switch 42 ... Operation switch 43 ... LED
44 ... Buzzer 46 ... Liquid crystal display 48 ... Communication interface Q ... QR code (two-dimensional code)
S103 (function pattern detecting means), S109 (first decoding means), S111 (decoding success / failure judging means), S115 (code image adding means), S119 (threshold setting means), S121 (second decoding means)

Claims (6)

A two-dimensional code encoded in a light / dark module composed of a light module and a dark module, and a function pattern required to decode the encoded data and the data or information accompanying the data are encoded In a two-dimensional code reader capable of reading a two-dimensional code including a data pattern,
Code image storage means for storing a plurality of code images acquired at different timings for the same two-dimensional code in the code image of the two-dimensional code;
Functional pattern detection means for detecting the functional pattern included in the one code image based on the one code image stored in the code image storage means;
First decoding means for decoding the data pattern included in the one code image using a first threshold value set for determining the brightness of the brightness module when detecting the functional pattern;
Decoding success / failure determining means for determining whether or not the data pattern can be decoded by the first decoding means;
When the decoding success / failure determining unit determines that the data pattern cannot be decoded, the degree of lightness and darkness is numerically expressed for each pixel in each image data constituting the code image stored in the code image storage unit Code image addition means for adding a predetermined image of the plurality of code images and generating an addition code image based on the addition image data obtained by the addition;
Threshold setting means for setting a second threshold for determining the brightness of the brightness module based on the added code image generated by the code image adding means;
Second decoding means for decoding the data pattern included in the addition code image using the second threshold;
A two-dimensional code reading device comprising:   2. The two-dimensional code reading device according to claim 1, wherein the code image storage means is an annular storage device capable of logically storing each image data constituting the plurality of code images in a circular manner.   The threshold value setting means performs a second derivative operation on the increase / decrease change amount of the added image data for each of the pixels constituting the addition code image adjacent to each other in a row, and a second derivative value obtained as a result of the second derivative operation is obtained. 3. The two-dimensional code reader according to claim 1, wherein the added image data that becomes zero is set to the second threshold value.   The threshold setting means obtains an average value obtained by dividing the sum of the addition image data for each pixel arranged adjacent to each other in a column with the pixels constituting the addition code image by the number of pixels constituting the column. 3. The two-dimensional code reader according to claim 1, wherein the second threshold is set to the second threshold value.   The code image addition means includes an adder of 1/2 or more of the number of images for the predetermined image, and operates these in parallel to perform the addition operation for each pixel for the predetermined image almost simultaneously. 5. The two-dimensional code reading device according to claim 1, wherein the addition code image is generated by obtaining the addition image data.   The code image adding means removes the oldest image data from the added image data and adds the newest image data to the added image data from among the image data for the predetermined image used to obtain the added image data. 5. The two-dimensional code reading device according to claim 1, wherein new addition image data is obtained and the addition code image is generated. 6.

Images