JP2007034546A - Optical reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical reader for preventing an occurrence of a large difference in average time until the code is read both by a positive code and by a negative code. <P>SOLUTION: When an auto mode capable of reading both the positive code and negative code is selected, the optical reader generates combination image data in which original image data captured by imaging and inverted image data generated by black-and-white-inverting the original image data. A code area extraction part 17 extracts a code area from the generated combination image data, a decode processing part 18 applies decode processing to the extracted code area, based on either a positive recognizing algorithm or negative algorithm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical reading apparatus, and more particularly to an improvement in a method for performing decoding processing (reading processing) on a code such as a one-dimensional code or a two-dimensional code.

  2. Description of the Related Art Conventionally, in a production line or the like in a factory, an article with a barcode is given to an article to be conveyed (parts etc.) or a pallet that holds the article, and the identification information is read from the barcode. A system is used to identify the type. The barcode is optically read by an optical reader having a light emitting element and a light receiving element, and the optical reader recognizes the identification information represented by the barcode by performing a decoding process on the read barcode. (For example, Patent Document 1).

  As codes that can be read by the optical reader, two-dimensional codes such as QR codes are generally known in addition to one-dimensional codes such as barcodes. In such a general code, since the code area is written in black on a white background, the lightness of the code area is lower than the lightness of the ground color. When reading this type of code, it is possible to determine an area having a lightness lower than a predetermined threshold value as a code area and read the code based on the pattern of the code area.

  Recently, a code in which a code area and its surrounding area are reversed in black and white may be used. Such a code is created, for example, by selectively irradiating a black sheet with a laser beam by a so-called laser marking method and marking the code area in white, and the code area has a lightness of the ground color. Higher than. When reading this type of code, it is possible to determine an area having a lightness higher than a predetermined threshold value as a code area and read the code based on the pattern of the code area.

  In an optical reader, a normal code (hereinafter referred to as “positive code”) that is positively expressed by the code area being written in black can be read, or by being reversed in black and white. Some codes can be read negatively (hereinafter referred to as “negative codes”). This type of optical reader performs, for example, a normal mode in which only a positive code can be read, a negative mode in which only a negative code can be read, and an auto mode in which both a positive code and a negative code can be read. The user can select which mode to execute.

  FIG. 7 is a flowchart showing a first conventional example of the code reading process. The optical reading apparatus of this conventional example first generates original image data by imaging a subject (step S201), stores the original image data in a memory, and then performs different processing depending on the selected mode. Do. The memory stores an algorithm (positive recognition algorithm) for recognizing a positive code. The positive recognition algorithm is a program that represents a procedure for determining an area having lightness lower than a predetermined threshold value as a code area and reading the code based on the pattern of the code area.

  In the decoding process, a target area (for example, a rectangular area) that is considered to be a code area is extracted from the subject. When it is determined that the extracted target area is a code area, a decoding process is performed on the code area. More specifically, the decoding processing unit sequentially performs two types of determination processing on the extracted target area as to whether or not the target area is a code area. In the first determination process (first determination process), a determination process with a high possibility of determining that the target area is the code area is performed on all the extracted target areas. If the subject includes a code area, the code area is usually extracted in the first determination process.

  However, in some rare cases, the code area cannot be extracted by the first determination process even when the subject includes the code area due to various factors such as dirt adhering to the code area. Assuming such a case, if the code area cannot be extracted in the first determination process, in the subsequent second determination process (second determination process), for all the extracted target areas, A multifaceted approach is made by executing a determination process that is highly likely to be determined to be a code area, that is, a process that performs determination using more determination criteria than the first determination process. The In the second determination process, the determination is performed using more determination criteria than in the first determination process, so that the time required for the determination process is longer than that in the first determination process.

  When the normal mode is selected (step S202), the decoding process is performed based on the positive recognition algorithm stored in the memory (step S203). Therefore, if a positive code is included in the image read from the subject, the positive code is read. However, any code cannot be read unless the positive code is included in the image read from the subject.

  In the normal mode, for example, the imaging time Ti in step S201 is 70 msec, the decoding processing time Td in step S203 is 26 msec, and the time Tt from the start of processing until the positive code is read is Tt = Ti + Td = 96 msec. In the decoding process, an error occurs in the time required until the code area is extracted depending on the position of the code area in the subject. The decoding process time Td here indicates an average time when the positions of the code areas are different. Yes.

  When the negative mode is selected (step S202), the inverted image data is generated by inverting the brightness of the original image data stored in the memory (step S204). Thereby, when a negative code is included in the image read from the subject, the negative code is converted into a positive code. Therefore, the negative code converted into the positive code can be read by performing the decoding process on the reverse image data based on the positive recognition algorithm thereafter (step S205). However, any code cannot be read unless the negative code is included in the image read from the subject.

  In the negative mode, for example, the imaging time Ti in step S201 is 70 msec, the inversion processing time Tr in step S204 is 5 msec, the decoding processing time Td in step S205 is 26 msec, and the time Tt from the start of processing until the negative code is read is Tt = Ti + Tr + Td = 101 msec.

  When the auto mode is selected (step S202), first, decoding processing is performed based on the positive recognition algorithm (step S206). Therefore, if a positive code is included in the image read from the subject (Yes in step S207), the positive code is read. If the positive code has not been read (No in step S207), after the inverted image data is generated by inverting the brightness of the original image data stored in the memory (step S208), the positive recognition algorithm Based on the above, a decoding process is performed on the inverted image data (step S209).

  FIG. 8 is a time chart for explaining the time required for the code reading process in the auto mode. FIG. 8A shows the case of the first conventional example, and FIG. 8B shows the case of the present invention. In the auto mode in the first conventional example, for example, if the imaging time Ti in step S201 is 70 msec and the decoding processing time Td in step S206 is 26 msec, and a positive code is included in the image read from the subject, The time Tt from the start of processing until the positive code is read is Tt = Ti + Td = 96 msec (see FIG. 8A). In this example, the code area is extracted in the first determination process, but in rare cases, the code area cannot be extracted in the first determination process and may be extracted in the subsequent second determination process. In such a case, as shown by a broken line, a corresponding delay time Tn (for example, 270 msec) is required.

  If the image read from the subject contains a negative code instead of a positive code, the code area is not extracted in the decoding process of step S206, and is generated after the inversion process (step S208). The decoded image data is decoded (step S209). In this case, the first determination process and the second determination process are always performed in the decoding process in step S206, and in addition to the corresponding delay time Tn (= 270 msec), the inversion process time Tr (= 5 msec) in step S208. ) And the decoding processing time Td (= 26 msec) of step S209 is required. Therefore, when a negative code is included in the subject image, the time Tt from the start of processing until the negative code is read is Tt = Ti + Td + Tn + Tr + Td = 396 msec (see FIG. 8A).

  FIG. 9 is a flowchart showing a second conventional example of the code reading process. As in the first conventional example, this conventional optical reading apparatus first generates original image data by imaging a subject (step S301), stores the original image data in a memory, and then is selected. Different processing is performed depending on the mode. The memory stores an algorithm for recognizing a positive code (positive recognition algorithm) and an algorithm for recognizing a negative code (negative recognition algorithm). The negative recognition algorithm is an algorithm different from the positive recognition algorithm, and is a program representing a procedure for determining a region having a lightness higher than a predetermined threshold as a code region and reading the code based on the pattern of the code region. .

  When the normal mode is selected (step S302), the decoding process is performed based on the positive recognition algorithm stored in the memory (step S303). Therefore, if a positive code is included in the image read from the subject, the positive code is read. However, any code cannot be read unless the positive code is included in the image read from the subject. In the normal mode, for example, the imaging time Ti in step S301 is 70 msec, the decoding processing time Td in step S303 is 26 msec, and the time Tt from the start of processing until the positive code is read is Tt = Ti + Td = 96 msec.

  When the negative mode is selected (step S302), the decoding process is performed based on the negative recognition algorithm stored in the memory (step S304). Therefore, if a negative code is included in the image read from the subject, the negative code is read. However, any code cannot be read unless the negative code is included in the image read from the subject. In the negative mode, for example, the imaging time Ti in step S301 is 70 msec, the decoding processing time Td in step S304 is 26 msec, and the time Tt from the start of processing until the negative code is read is Tt = Ti + Td = 96 msec.

When the auto mode is selected (step S302), a decoding process is performed so that both the positive code and the negative code can be read (step S305). In order to perform such a decoding process, a recognition algorithm for recognizing both positive code and negative code is required. In order to create such a recognition algorithm, a design equivalent to existing software is required. You have to make changes and it takes time. Further, the decoding process in step S305 requires a considerably longer processing time than the time (= 52 msec) obtained by simply doubling the decoding processing time Td (= 26 msec) for reading only one of the positive code and the negative code. The time Tt from the start of processing until the positive code or negative code is read is Tt >> Ti + 2Td = 122 msec.
Japanese Patent Laid-Open No. 2003-669

  In the first conventional example, as shown in FIG. 8A, the time Tt until the positive code is read in the auto mode is 96 msec, which is a relatively short time, while the negative in the auto mode. The time Tt until the code is read is as long as 396 msec, and the difference between them is very large. Therefore, there may be a large difference in the average time until the code is read between when the subject includes a positive code and when a negative code is included, which may be difficult to apply to a production line.

  On the other hand, in the second conventional example, as described above, a recognition algorithm for recognizing both the positive code and the negative code must be created by making a considerable design change to the existing software. Moreover, even when decoding is performed using such a recognition algorithm, the time until the code is read cannot be effectively shortened. In the second conventional example, it is necessary to prepare both a positive recognition algorithm and a negative recognition algorithm.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical reading device that can prevent a large difference in average time until a code is read between a positive code and a negative code. To do. Furthermore, an object of the present invention is to provide an optical reading apparatus capable of performing reading processing on positive codes and negative codes using existing software.

  An optical reading apparatus according to the present invention includes an imaging unit that shoots an object to be read and generates original image data, a brightness reversing unit that generates inverted image data obtained by inverting the brightness of the original image data, and the original image data. And an image combining unit that combines the inverted image data to generate combined image data, and performs a reading process on the combined image data with respect to one of a positive code and a negative code. And a code reading means.

  According to such a configuration, positive code (positive code) and negative code (negative code) are generated for the combined image data generated by combining the original image data and the inverted image data. By performing the reading process for either one, it is possible to prevent a large difference in the average time until the code is read, regardless of whether the positive code or the negative code is read.

  For example, when a positive recognition algorithm is used, a positive code can be read from the original image data if the reading target includes a positive code, and an inverted image can be read if the reading target includes a negative code. A negative code converted from data to a positive code can be read. On the other hand, when the negative recognition algorithm is used, the negative code can be read from the original image data if the read target includes a negative code, and the reverse image is read if the read target includes a positive code. A positive code converted from data to a negative code can be read. Therefore, it is possible to read the positive code and the negative code using existing software, and it is not necessary to prepare both a positive recognition algorithm and a negative recognition algorithm.

  In the optical reading apparatus according to the present invention, the code reading means extracts a code area extracting means for extracting an area where the code is written from the combined image data as a code area, and reads the read data based on the extracted code area. A data extraction means for generating, wherein the code area extraction means is a first area extraction means for extracting a code area based on a first determination criterion; and a code area is not extracted by the first area extraction means. And a second region extracting means for extracting a code region based on a second determination criterion different from the first determination criterion.

  For example, the determination processing time by the second region extraction unit is longer than the determination processing time by the first region extraction unit. Therefore, the code is read when the code area is extracted by the first area extracting means and when the code area is not extracted by the first area extracting means and the code area is extracted by the second area extracting means. The difference in time until becomes larger. However, if the configuration is such that the positive code and the negative code are simultaneously read from the combined image data as in the present invention, the average time until the code is read depending on whether the positive code or the negative code is included. It is possible to effectively prevent a large difference from occurring.

  In the optical reading apparatus according to the present invention, the image combining means arranges the original image data and the inverted image data without overlapping so as to generate the combined image data. According to such a configuration, the reading process can be sequentially performed on the original image data and the inverted image data arranged without being overlapped.

  In the optical reading apparatus according to the present invention, the original image data has a rectangular shape, and the image combining means arranges the original image data and the inverted image data adjacent to each other. According to such a configuration, since the original image data and the inverted image data are arranged adjacent to each other, the reading process can be continuously performed, and a certain area is formed between the original image data and the inverted image data. Compared to the case where the code is read, the time until the code is read can be shortened.

  According to the present invention, a positive code is obtained by performing a reading process on either a positive code or a negative code on the combined image data generated by combining the original image data and the inverted image data. When reading either of the negative code and the negative code, it is possible to prevent a large difference in the average time until the code is read. In addition, it is possible to read the positive code and the negative code using existing software, and it is not necessary to prepare both a positive recognition algorithm and a negative recognition algorithm.

  FIG. 1 is a block diagram showing a configuration example of an optical reading device 1 according to an embodiment of the present invention. The optical reading device 1 is applied to a production line in a factory, for example, and an object (reading object) attached in advance to an article (part or the like) conveyed on the conveyance path of the production line or a pallet holding the article. ) Optically reading the code shown in 2. The optical reading device 1 is connected via a cable to an external device such as a monitor for displaying a captured image and an analysis result on a screen in real time, and a personal computer that takes in image data and analysis data and performs various controls. .

  The optical reading device 1 includes a control unit 3 including a CPU (Central Processing Unit) and a CMOS (Complementary Metal Oxide Semiconductor) electrically connected to the control unit 3. Membrane semiconductor) Image sensor 4, LD (Laser Diode) 5 for pointer, LED (Light Emitting Diode) 6 for lighting, FPGA (Field Programming Gate Array) 7, inverting circuit 8, memory 9, mode selection A switch 10 and an inversion processing unit 14 are provided.

  The pointer LD 5 is a light emitting element that generates irradiation light to be the pointer 11, and can display a readable rectangular area and its center position on the subject 2. The illumination LED 6 is a light emitting element that generates irradiation light for illuminating a reading target of the subject 2.

  The CMOS image sensor (imaging means) 4 includes an imaging circuit 12 and an A / D (Analog / Digital) conversion circuit 13. The imaging circuit 12 is composed of a rectangular semiconductor chip that outputs a pixel signal corresponding to the amount of received light, and a large number of photodiodes are arranged in a matrix as light receiving elements. Each light receiving element is provided with an amplifying element for amplifying the power of a pixel signal generated according to the amount of received light for each light receiving element, and one pixel is constituted by the light receiving element and the amplifying element. Image data (analog data) is generated in the imaging circuit 12 when each light receiving element receives reflected light from the illumination LED 6 on the subject 2. The analog data generated in the imaging circuit 12 is input to the A / D conversion circuit 13 after being subjected to a predetermined correction process.

  The A / D conversion circuit 13 is a quantization circuit for image data that converts input analog data into M-bit digital data. Here, it is assumed that the voltage value is quantized to 10 bits, and the amount of received light is represented by the brightness of 1024 gradations.

  The FPGA 7 is an image data compression circuit that converts quantized image data into image data having a smaller number of bits. That is, the FPGA 7 converts the M-bit digital data input from the A / D conversion circuit 13 of the CMOS image sensor 4 into N-bit (N <M) digital data and outputs it. Here, it is assumed that 10-bit image data is converted into 8-bit digital data having a smaller number of bits. That is, the image data represented by the lightness of 1024 gradations is converted into image data represented by the lightness of 256 gradations, whose information amount is ¼ of the image data before conversion.

  The inversion circuit 8 generates inverted image data in which the brightness is inverted by performing a bit inversion process (inversion process) on each pixel of the image data input from the FPGA 7. That is, for each bit of 8-bit image data, the data of “0” or “1” is inverted with respect to each other, thereby converting the image data represented by the lightness level K in 256 gradations into the lightness level (255-K ) Image data. For example, image data with a lightness level “0” is converted into image data with a lightness level “255”, and image data with a lightness level “10” is converted into image data with a lightness level “245”. As a result, black pixels are converted to white, and white pixels are converted to black.

  The inverted image data generated by the inverting circuit 8 is input to the control unit 3. The control unit 3 outputs an instruction signal indicating that inversion processing should be performed in the inversion circuit 8, and the inversion circuit 8 performs inversion processing only when the instruction signal is received. Therefore, if the instruction signal is not output from the control unit 3, the inversion process in the inversion circuit 8 is not performed, and the image data output from the FPGA 7 is input to the control unit 3 as it is. Whether to output the instruction signal from the control unit 3 to the inverting circuit is determined depending on which mode is executed among a plurality of modes (normal mode, negative mode, and auto mode) described later. The user can select which mode to execute among the plurality of modes by operating the mode selection switch 10.

  The inversion processing unit (brightness inversion means) 14 performs the same inversion processing as that of the inversion circuit 8 on the image data input to the control unit 3 without going through the inversion circuit 8 by software processing, and the brightness is inverted. Inverted image data is generated. The control unit 3 executes a reversal process by the reversal processing unit 14 in accordance with the mode selected by the user.

  The memory 9 includes an original image data storage unit 9A, an inverted image data storage unit 9B, and a recognition algorithm storage unit 9D. The original image data storage unit 9A stores image data input from the FPGA 7 to the control unit 3 without going through the inversion circuit 8, that is, image data not subjected to inversion processing (original image data). The inverted image data storage unit 9B stores image data input from the FPGA 7 via the inversion circuit 8 to the control unit 3, that is, image data that has been subjected to inversion processing (inverted image data).

  The original image data storage unit 9A and the reverse image data storage unit 9B in the memory 9 are determined in advance as continuous regions, and the original image data and the reverse image data are stored in the respective regions, whereby continuous combined image data 9C. Is generated. Therefore, the original image data input to the control unit 3 without passing through the inversion circuit 8 is stored in the original image data storage unit 9A, and the original image data is subjected to inversion processing by the inversion processing unit 14 so that the inverted image is obtained. By storing the data in the inverted image data storage unit 9B, the combined image data 9C can be generated.

  However, the present invention is not limited to this configuration, and the combined image data storage unit is provided in the memory 9, and the original image data stored in the original image data storage unit 9A and the inversion stored in the inverted image data storage unit 9B. A configuration may be employed in which combined image data is generated by performing processing for combining image data, and the combined image data is stored in the combined image data storage unit.

  The optical reading device 1 can read a normal code (positive code) that is positively expressed by displaying the code area in black in the decoding process, or a code that is negatively expressed by reversing black and white. (Negative code) can also be read. The recognition algorithm storage unit 9D of the memory 9 stores a recognition algorithm used when performing the decoding process. This recognition algorithm is a program representing a procedure for recognizing a positive code.

  2A and 2B are diagrams illustrating a configuration example of a code that can be read by the optical reading device 1, in which FIG. 2A is a schematic diagram of a barcode 20 that is an example of a one-dimensional code, and FIG. 2B is an example of a two-dimensional code. A schematic diagram of a QR code 30 is shown.

  In the barcode 20 shown in FIG. 2A, a plurality of bar-shaped code regions 21 having different widths are written in black. The plurality of code regions 21 have the same length, and extend in parallel at a predetermined interval. Thus, a plurality of code areas 21 are arranged one-dimensionally in a rectangular area (code arrangement area 22) sandwiched between the code areas 21 at both ends. An area around the code area 21, that is, an area other than the code area 21 in the code arrangement area 22 and an area outside the code arrangement area 22 are white areas. The white areas on the left and right sides outside the code arrangement area 22 are so-called quiet zones 23 and have a predetermined width so that the code arrangement area 22 can be detected.

  In the QR code 30 shown in FIG. 2B, black code areas 32 are two-dimensionally arranged in a predetermined pattern in a rectangular code arrangement area 31. In FIG. 2B, details of the code area 32 are omitted, and hatching is performed in the code arrangement area 31, but the code area 32 is represented in a predetermined pattern in the code arrangement area 31. The surrounding area, that is, the area other than the code area 32 in the code arrangement area 31 and the area outside the code arrangement area 31 are white areas.

  A white area surrounding the outside of the code arrangement area 31 is a quiet zone 33, and has a predetermined width so that the code arrangement area 31 can be detected. As shown in FIG. 2B, a rectangular pattern 34 called a finder pattern is arranged at three of the four corners of the QR code 30, and the code is converted into a QR code by the finder pattern 34. 30 and the directivity of the QR code 30 is defined.

  In this way, in a general code such as a one-dimensional code or a two-dimensional code, the code area is arranged in a rectangular code arrangement area, so that it is considered as a code area by detecting the rectangular area from the subject 2. The rectangular area to be extracted can be extracted. However, since some subjects 2 may have a rectangular area other than the code, it is necessary to determine whether or not the extracted rectangular area is a code area.

  FIG. 3 is a functional block diagram illustrating main operations of the control unit 3. The control unit 3 functions as a mode selection unit 15, a rectangular region extraction unit 16, a code region extraction unit 17, and a decoding processing unit 18 when the CPU executes a program. The code area extraction unit 17 includes a first determination processing unit 17A and a second determination processing unit 17B. The rectangular area extraction unit 16, the code area extraction unit 17, and the decoding processing unit 18 constitute code reading means for performing code reading processing.

  A mode selection signal based on the operation of the mode selection switch 10 is input to the mode selection unit 15. When the auto mode is selected, the original image data and the inverted image data are input to the rectangular area extraction unit 16 as combined image data. When the normal mode is selected, the original image data is input to the rectangular area extraction unit 16. When the negative mode is selected, the reverse image data is input to the rectangular area extraction unit 16.

  The rectangular area extraction unit 16 extracts a rectangular area from the subject 2, and the code area extraction unit 17 extracts a code area from the extracted rectangular area. Then, based on the code area extracted by the code area extraction unit 17, the decode processing unit (data extraction unit) 18 performs a decoding process to generate read data. The code area extraction unit (code area extraction unit) 17 sequentially performs two types of determination processing on the rectangular area extracted by the rectangular area extraction unit 16 as to whether or not the rectangular area is a code area. In the first determination process (first determination process) performed by the first determination processing unit (first area extraction unit) 17A, rectangular areas are extracted from all the extracted rectangular areas based on a predetermined first determination criterion. A determination process that is highly likely to be determined as a code area is performed. If the subject 2 includes a code area, the code area is usually extracted in the first determination process.

  However, even if the subject 2 includes a code area due to various factors such as dirt attached to the code area, the code area may not be extracted by the first determination process. Assuming such a case, if the code area could not be extracted in the first determination process, the second determination process (second area) performed by the second determination processing unit (second area extraction means) 17B thereafter In the determination process), for all the extracted rectangular areas, a determination process that is highly likely to be determined as a code area based on a predetermined second determination criterion, that is, more than the first determination process. A multi-faceted approach is made by executing a process of making a judgment using many judgment criteria. In the second determination process, the determination is performed using more determination criteria than in the first determination process, so that the time required for the determination process is longer than that in the first determination process.

  FIG. 4 is a flowchart showing an aspect of the code reading process. In the present embodiment, unlike the conventional example shown in FIGS. 7 and 9, imaging is performed in different modes in the normal mode and the auto mode, and in the negative mode. That is, when the normal mode is selected and when the auto mode is selected, the image data output from the FPGA 7 shown in FIG. Stored in the memory 9. On the other hand, when the negative mode is selected, an instruction signal is input from the control unit 3 to the inverting circuit 8, whereby image data output from the FPGA 7 is input to the control unit 3 via the inverting circuit 8, The generated reverse image data is stored in the memory 9.

  As described above, in the negative mode, the inverted image data is generated simultaneously with the imaging (in parallel). Therefore, the original image data once stored in the memory 9 is inverted in black and white to generate the inverted image data. In comparison, the time required to generate the inverted image data can be shortened. However, the present invention is not limited to this configuration, and the original image data is temporarily stored in the memory 9 by imaging the subject 2 and the inverted image data is generated by reversing the original image data in black and white. Also good.

  When the normal mode is selected (step S101), the original image data output from the CMOS image sensor 4 is input to the control unit 3 without passing through the inversion circuit 8 and stored in the memory 9, thereby capturing an image. Is performed (step S102). Then, the original image data stored in the memory 9 is decoded based on the positive recognition algorithm (step S103). Therefore, if a positive code is included in the image read from the subject 2, the positive code is read. However, if the image read from the subject 2 does not include a positive code, no code can be read.

  In the normal mode, for example, the imaging time Ti in step S102 is 70 msec, the decoding processing time Td in step S103 is 26 msec, and the time Tt from the start of processing until the positive code is read is Tt = Ti + Td = 96 msec. In the decoding process, an error occurs in the time required until the code area is extracted depending on the position of the code area in the subject 2. The decoding process time Td here indicates an average time when the positions of the code areas are different. ing.

  When the negative mode is selected (step S101), the original image data output from the CMOS image sensor 4 is inverted by the inversion circuit 8, and the generated inverted image data is input to the control unit 3 and stored in the memory 9. Imaging is performed by storing (step S104). Then, decoding processing is performed on the reverse image data stored in the memory 9 based on the positive recognition algorithm (step S105). When a negative code is included in the image read from the subject 2, the original image data is inverted in black and white to generate inverted image data, whereby the negative code is converted into a positive code. Therefore, the negative code converted into the positive code can be read by performing the decoding process on the inverted image data based on the positive recognition algorithm. However, if the image read from the subject 2 does not include a negative code, no code can be read.

  In the negative mode, for example, the imaging time Ti in step S104 is 70 msec, the decoding processing time Td in step S105 is 26 msec, and the time Tt from the start of processing until the negative code is read is Tt = Ti + Td = 96 msec.

  When the auto mode is selected (step S101), the original image data output from the CMOS image sensor 4 is input to the control unit 3 without passing through the inversion circuit 8, and imaging is performed (step S106). ). Then, the original image data input to the control unit 3 and the inverted image data inverted by the inversion processing unit 14 are stored in the memory 9 to generate combined image data (step S107), and the generated combined image is generated. The data is decoded based on the positive recognition algorithm (step S108).

  In the process of step S107, the inversion process by the inversion processing unit 14 is performed and the generated inverted image data is simply combined with the original image data as it is, so the time Tr required for the process is the same as the time required for the inversion process. For example, 5 msec. Since the decoding process of step S108 is performed on the combined image data obtained by combining the original image data and the inverted image data, the time TD required for the process is the time required for the decoding process on the original image data or the decoding on the inverted image data. The time required for processing is simply doubled (Td × 2), for example, 52 msec.

  FIG. 5 is a schematic diagram illustrating an example of an image 50 based on the combined image data. As shown in FIG. 5, the image 50 based on the combined image data is an image in which an image 51 based on the original image data each having a rectangular shape and an image 52 based on the inverted image data are combined side by side. In the example shown in FIG. 5, the image 51 based on the original image data and the image 52 based on the reverse image data are arranged adjacent to each other so as not to overlap.

  By arranging the images 51 and 52 without overlapping, the reading processing for the images 51 and 52 can be sequentially performed. Further, by arranging the images 51 and 52 adjacent to each other, the reading process can be performed continuously, and compared with the case where a certain area is formed between the images 51 and 52, the code It is possible to shorten the time until the is read. However, the present invention is not limited to this mode, and a certain area may be formed between the images 51 and 52. In addition, as shown in FIG. 5, the images 51 and 52 may be combined side by side instead of being aligned side by side. Further, the images 51 and 52 may overlap in a range that does not affect the code reading.

  In the example shown in FIG. 5, the image 51 based on the original image data includes a rectangular area 41 including a predetermined character and a rectangular area 42 including a black area, in addition to the QR code 30 including a positive code. . In the subject 2 attached to the article conveyed on the production line in the factory, character information such as a part number that can be visually recognized by the worker is usually written in addition to the code, and the character information is surrounded by a rectangular frame. In many cases, a rectangular area is described.

  When decoding processing is performed on the combined image data as shown in FIG. 5, from the image 51 corresponding to the original image data, the rectangular area 31 corresponding to the QR code 30 and the other two rectangular areas 41, 42 is extracted, and from the image 52 corresponding to the inverted image data, three rectangular regions 43, 44, and 45 made of inverted images respectively corresponding to the three rectangular regions 31, 41, and 42 are extracted. Then, it is determined that only the rectangular area corresponding to the QR code 30 is the code arrangement area 31 from the extracted rectangular areas 31, 41, 42, 43, 44, 45. Decoding processing is performed on the code area 32 arranged in the area.

  FIG. 6 is a schematic diagram illustrating another example of the image 50 based on the combined image data. When a negative code is written on the subject 2, as shown in FIG. 6, the image 51 based on the original image data includes a rectangular area 43 corresponding to the negative code and other rectangular areas 44 and 45. . On the other hand, the image 52 based on the inverted image data includes the QR code 30 composed of the positive code obtained by reversing the negative code in black and white, and the rectangular areas 41 corresponding to the rectangular areas 44 and 45, respectively. , 42 are included.

  When decoding processing is performed on the combined image data as shown in FIG. 6, the rectangular area 31 corresponding to the QR code 30 and the other two rectangular areas 41, from the image 52 corresponding to the inverted image data, 42 is extracted, and from the image 51 corresponding to the original image data, three rectangular regions 43, 44, and 45 respectively corresponding to the three rectangular regions 31, 41, and 42 are extracted. Then, it is determined that only the rectangular area corresponding to the QR code 30 is the code arrangement area 31 from the extracted rectangular areas 31, 41, 42, 43, 44, 45. Decoding processing is performed on the code area 32 arranged in the area.

  In the present embodiment, both the positive code and the negative code are obtained by performing a decoding process based on an existing positive recognition algorithm on the combined image data generated by combining the original image data and the inverted image data. Can be read. That is, if the subject 2 includes a positive code, the positive code can be read from the original image data, and if the subject 2 includes a negative code, the negative code converted from the inverted image data to the positive code. Can be read. Therefore, unlike the second conventional example shown in FIG. 9, the existing code can be used to decode the positive code and the negative code, and both the positive recognition algorithm and the negative recognition algorithm are prepared. There is no need.

  However, the decoding process is not limited to the configuration that is performed based on the positive recognition algorithm, but may be configured to be performed based on the negative recognition algorithm. In such a configuration, if the subject 2 contains a negative code, the negative code can be read from the original image data. If the subject 2 contains a positive code, the negative image can be read from the inverted image data. A positive code converted into a code can be read. Therefore, by performing a decoding process based on an existing negative recognition algorithm, both a positive code and a negative code can be read.

  In the present embodiment, since the positive code and the negative code are simultaneously decoded from the combined image data, the first conventional example shown in FIG. 7 depends on which of the positive code and the negative code is included. Thus, it is possible to prevent a large difference from occurring in the average time until the code is read. That is, in the first conventional example, as shown in FIG. 8A, a large difference Tg in the average time until the code is read depends on whether the code included in the subject 2 is a positive code or a negative code. However, in this embodiment, as shown in FIG. 8B, regardless of whether the code included in the subject 2 is a positive code or a negative code, the average time until the code is read is constant. is there. In the present embodiment, the time Tt required for reading the positive code or the negative code is, for example, Tt = Ti + Tr + TD = 127 msec, regardless of whether the subject 2 includes a positive code or a negative code. is there. However, in rare cases, the code area cannot be extracted in the first determination process, and may be extracted in the subsequent second determination process. In such a case, as shown by the broken line, the corresponding delay time TN (For example, 540 msec) is required.

  In the above embodiment, the QR code 30 has been described as an example of a two-dimensional code. However, the optical reading apparatus 1 of the present invention can use various two-dimensional codes other than the QR code 30, such as a so-called code 49, code 16K, and coder block. , PDF417, super code, ultra code, veri code, CP code, data matrix, code 1, maxi code, array tag, and aztec code. Further, the optical reading device 1 of the present invention is not limited to a one-dimensional code or a two-dimensional code, and can be applied to other codes.

  The means for reading the code from the subject 2 is not limited to the CMOS image sensor 4 and may be other means such as a line sensor. In the above embodiment, the subject 2 includes only one code. However, the subject 2 may include two or more codes. In this case, the subject 2 may include different types of codes.

  The present invention is not limited to the contents of the above-described embodiment, and various modifications can be made within the scope of the claims.

It is a block diagram which shows the example of 1 structure of the optical reader by embodiment of this invention. It is a figure which shows the structural example of the code which can be read by an optical reader, (a) is the schematic of the barcode which is an example of a one-dimensional code, (b) is the schematic of the QR code which is an example of a two-dimensional code Is shown. It is the functional block diagram shown about the main operation | movement of the control part. It is a flowchart which shows the aspect of a code reading process. It is the schematic which shows an example of the image based on combined image data. It is the schematic which shows the other example of the image based on combined image data. It is a flowchart which shows the 1st prior art example of a code reading process. It is a time chart for demonstrating the time which the code reading process in an auto mode requires, (a) is the case of a 1st prior art example, (b) has shown the case of this invention. It is a flowchart which shows the 2nd prior art example of a code reading process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical reader 2 Subject 3 Control part 4 CMOS image sensor 5 LD for pointers
6 LED for lighting
7 FPGA
8 Inversion circuit 9 Memory 10 Mode selection switch 14 Inversion processing unit 15 Mode selection unit 16 Rectangular region extraction unit 17 Code region extraction unit 17A First determination processing unit 17B Second determination processing unit 18 Decoding processing unit 20 Barcode 21 Code region 22 Code arrangement area 30 QR code 31 Code arrangement area 32 Code areas 41, 42, 43, 44, 45 Rectangular area

Claims (4)

An imaging means for photographing a reading object and generating original image data;
Brightness inversion means for generating inverted image data obtained by inverting the brightness of the original image data;
Image combining means for combining the original image data and the inverted image data to generate combined image data;
An optical reading apparatus, comprising: a code reading unit that performs a reading process on the combined image data with respect to either a positive code or a negative code. The code reading means, a code area extracting means for extracting an area where the code is written from the combined image data as a code area;
Data extraction means for generating read data based on the extracted code area,
The code area extraction means includes first area extraction means for extracting a code area based on a first determination criterion;
And a second region extraction unit that extracts a code region based on a second determination criterion different from the first determination criterion when a code region is not extracted by the first region extraction unit. The optical reading device according to claim 1.   2. The optical reading apparatus according to claim 1, wherein the image combining unit generates the combined image data by arranging the original image data and the inverted image data without overlapping. The original image data has a rectangular shape,
4. The optical reader according to claim 3, wherein the image combining unit arranges the original image data and the inverted image data adjacent to each other.

Images