JP7402088B2 - optical reader - Google Patents

Description

The present invention relates to an optical reading device that reads information included in a read image generated by imaging a workpiece.

Generally, a code reader uses a camera to image a code such as a barcode or two-dimensional code attached to a workpiece, uses image processing to cut out the code contained in the obtained image, binarizes it, and decodes it. It is configured so that information can be read (for example, see Patent Documents 1 and 2).

The optical reading device of Patent Document 1 determines the upper limit of the exposure time for reading the code based on the moving speed of the workpiece and the cell size constituting the code, and acquires a plurality of images including the code. Through analysis, the exposure time is automatically set within the above upper limit value.

The optical reading device of Patent Document 2 includes a first core that causes an imaging unit to perform imaging processing and transfers acquired image data to a shared memory, and a shared memory that transfers acquired image data to a shared memory based on a decoding processing request from the first core. and a second core that reads image data from within and executes decoding processing.

JP2018-136860A JP2012-64178A

By the way, reading processing in optical reading devices such as those disclosed in Patent Documents 1 and 2 involves pre-processing that performs various filter processes, etc., and scanning the entire image after pre-processing to identify areas where there is a high possibility that a code exists. Generally, the process consists of three processes: a code search process to search for a code candidate area (code candidate area), and a decode process to decode using image data of the code candidate area specified in the code search process.

However, if the range imaged by the imaging unit is wide, the number of code candidate areas in the read image may increase. For example, code candidate regions can be extracted based on feature values that indicate code-likeness, but in addition to code candidate regions that actually contain codes, code candidate regions that do not contain codes are extracted. Sometimes. The reason for this is that even if a code is not included, if a character string or pattern similar to a code is attached to the workpiece, the feature amount of that part will become large and it will be extracted as a code candidate area. .

If all of the extracted multiple code candidate regions contain codes, it is necessary to perform decoding processing on all of the code candidate regions. In some cases, it may not be included, and in that case, performing decoding processing on a code candidate area that does not contain a code is a wasteful process and will result in prolonging the time it takes to complete the decoding process. . In particular, when a plurality of codes exist in a read image and these codes are individually decoded, there is a problem in that the output of the decoding results is significantly delayed.

The present invention has been made in view of the above, and an object of the present invention is to enable high-speed output of code decoding results when a plurality of code candidate regions are extracted.

In order to achieve the above object, the present disclosure can be based on a stationary optical reading device that reads a code attached to a workpiece being conveyed on a line. The optical reading device includes an illumination unit for irradiating light toward an area through which the workpiece passes, and receives light irradiated from the illumination unit and reflected from the area through which the workpiece passes through. If a plurality of code candidate areas are extracted as a result of executing an extraction process that extracts code candidate areas from the read image generated by the image pickup unit and the read image generated by the image pickup unit, extraction The decoding process is executed sequentially for the multiple code candidate areas, and if the decoding process for any of the code candidate areas is successful, a decoding result is generated and the decoding process is performed at a position distant from the code candidate area where the code candidate area was successfully decoded. The processing unit includes a processing unit that excludes a code candidate region from a decoding target, and an output unit that outputs a decoding result generated by the processing unit.

According to this configuration, when the workpiece being conveyed on the line is irradiated with light from the illumination unit, the light reflected by the workpiece is received by the imaging unit, and a read image including the workpiece and the code attached to the workpiece is captured. is generated. The processing unit executes an extraction process on the read image and extracts a code candidate area. As a result of the extraction process, a plurality of code candidate regions may be extracted, and in addition to a code candidate region that includes a code, a code candidate region that does not include a code may be extracted.

When a plurality of code candidate regions are extracted, the processing unit sequentially performs decoding processing on the plurality of extracted code candidate regions. If any code candidate area is successfully decoded, a code candidate area located away from the code candidate area is excluded from the decoding target.

In other words, cases where multiple codes are attached to a workpiece are, for example, cases where multiple codes are printed on one label and are attached to the workpiece, or cases where multiple codes are attached to the workpiece. An example of this is when multiple codes are printed close to each other. In any of these cases, multiple codes are often close to each other. Therefore, it is unlikely that a code exists in a location far away from the code candidate region that has been successfully decoded, and code candidate regions that are located in locations where this code is unlikely to exist are excluded from the decoding target. By doing so, it is possible to perform decoding processing preferentially on code candidate areas where there is a high possibility that a code exists.

In the second disclosure, the processing unit determines a decoding processing area based on the position of a code candidate area that has been successfully decoded and a preset area limitation parameter, and determines a decoding processing area based on the position of a code candidate area that has been successfully decoded, and The candidate area can be targeted for decoding processing.

According to this configuration, when a certain code candidate area is successfully decoded, a decoding process area is determined based on the position of the code candidate area and a preset area limiting parameter, and a position within this decoding process area is determined. The decoding process is performed on the code candidate area that is For example, when a circle centered on the center of a code candidate area that has been successfully decoded is drawn, the area within this circle can be set as the decoding process area. In this case, the region limiting parameter may be the radius of the circle. This method is just an example, and other methods may be used to determine the decoding processing area. A region within a figure can be used as a decoding processing region.

In a third disclosure, the processing unit may target the code candidate region that overlaps the decoding processing region as a decoding processing target.

In other words, a code candidate area that overlaps with a decoding processing area is located close to a code candidate area that has been successfully decoded, and a code exists in such a code candidate area. Probability is high. In this case, it can be targeted for decoding.

In a fourth disclosure, the processing unit can exclude the code candidate area located outside the decoding processing area from the decoding processing target.

According to this configuration, a code candidate area located outside the decoding processing area is separated from a code candidate area that has been successfully decoded, and a code exists in such a code candidate area. Since the possibility is low, it can be excluded from decoding processing targets.

In a fifth disclosure, when setting the optical reading device, a read image including a plurality of codes is acquired from the imaging unit, and the processing unit performs decoding processing on the plurality of code candidate areas of the acquired read image. The apparatus further includes a tuning execution unit that automatically sets the area limiting parameter so that a plurality of code candidate areas that have been successfully decoded are included in the decoding process area.

According to this configuration, the region limiting parameter can be automatically set to an optimal value based on the read image.

A sixth disclosure includes a reception unit that accepts settings of the region-limiting parameters by a user.

According to this configuration, the region-limiting parameter can be set by the user, so that the region-limiting parameter can be set to include a plurality of codes attached to the actual workpiece. After the region-limiting parameters are automatically set by the tuning execution section, the user can also adjust the region-limiting parameters, and in this case, the receiving section can also be called an adjustment section. s
In the seventh disclosure, after determining the decoding processing area, if the processing unit succeeds in decoding processing for another code candidate area located within the decoding processing area, the processing unit determines the position of the another code candidate area and the A decoding processing area is newly determined based on the area-limiting parameter, and a code candidate area located within the newly determined decoding processing area is set as a decoding processing target.

For example, if three codes, the first code, the second code, and the third code, are attached to the workpiece in parallel, if the decoding process for the first code candidate area where the first code exists is successful, the first code, the second code, and the third code are attached to the workpiece. The first decoding processing area is determined based on the position of the first code candidate area and the area limiting parameter. In this first decoding processing area, a second code candidate area where the second code exists and a third code candidate area where the third code exists are located. Thereafter, the processing unit executes decoding processing on the second code candidate area, and if the decoding process is successful, determines a new decoding processing area based on the position of the second code candidate area and the area limiting parameter. do. A third code candidate area in which the third code exists is located in this new decoding processing area. In this way, the decoding processing area can be narrowed down step by step according to the success of the decoding process, thereby enabling faster decoding processing.

In an eighth disclosure, the processing unit can change the area limiting parameter according to the size of the code on the read image.

Even when imaging workpieces with codes of the same size, for example, if the distance between the workpiece and the imaging unit is short, the code will be large on the read image, and the distance between the workpiece and the imaging unit may be small. If it is far away, the code will be smaller on the read image. Therefore, if the area limitation parameter is a fixed value, even if the size of the decoding processing area is appropriate for a large code on the read image, the decoding processing area will be large for a small code on the read image. It is conceivable that a code candidate area with a low probability of containing a code will be included in the decoding processing area. According to this configuration, the area limitation parameter can be changed according to the size of the code on the read image, so it is possible to determine an appropriate decoding processing area regardless of the size of the code on the read image. can.

In a ninth disclosure, the processing unit changes the area limiting parameter so that the smaller the size of the code on the read image, the smaller the decoding processing area. Furthermore, in the tenth disclosure, the processing unit changes the area limiting parameter so that the larger the size of the code on the read image, the larger the decoding processing area.

Thereby, the size of the decoding processing area can be determined to correspond to the size of the code on the actual read image. Things that define the size of the code on the read image include, for example, the area of the code candidate area, the size of the minimum module of the code, and the like.

In the eleventh disclosure, the processing unit calculates an estimated value of the number of modules or the number of elements for each of the plurality of extracted code candidate regions, and selects a code candidate region to be decoded according to the calculated estimated value. select.

That is, the number of modules or the number of elements constituting a code is a feature quantity that does not depend on the area of the code occupied in the read image, and by using such a feature quantity, code candidate regions can be extracted at high speed.

As described above, according to the present disclosure, when a plurality of code candidate regions are extracted and the decoding process of any one of the code candidate regions is successful, the code candidate region located at a position distant from the code candidate region is is excluded from the decoding processing target, so that the decoding processing can be performed preferentially on the code candidate region where there is a high possibility that a code exists, and thereby the decoding result can be outputted at high speed.

FIG. 1 is a diagram illustrating the operation of an optical reading device according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of a workpiece to which a plurality of codes are attached. FIG. 3 is a block diagram of the optical reading device. FIG. 4 is a front view of the optical reading device. FIG. 5 is a diagram of the optical reading device viewed from the operation button side. FIG. 6 is a diagram of the optical reading device viewed from the terminal side. FIG. 7 is a flowchart illustrating an example of a procedure of decoding processing by the processing unit. FIG. 8 is a diagram showing an example of a read image generated by imaging a workpiece. FIG. 9 is a flowchart illustrating an example of the procedure of code search data generation processing. FIG. 10 is a diagram showing extracted code candidate regions. FIG. 11 is a diagram showing the determined code processing area. FIG. 12 is a diagram showing a case where a code candidate area located away from a successful code candidate area is excluded from decoding processing targets. FIG. 13 is a diagram showing a case where the code processing area is narrowed in stages. FIG. 14 is a diagram showing a case where the code becomes large on the read image. FIG. 15 is a diagram showing a case where the code becomes smaller on the read image. FIG. 16 is a diagram showing a state in which the size of the decoding processing area is changed to correspond to the case where the code on the read image is small. FIG. 17 is a diagram showing a state in which the size of the decoding processing area is changed to correspond to a case where the code on the read image is large.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings. Note that the following description of preferred embodiments is essentially just an example, and is not intended to limit the present invention, its applications, or its uses.

FIG. 1 is a diagram schematically showing the operation of an optical reading device 1 according to an embodiment of the present invention. In this example, a plurality of workpieces W are placed on the upper surface of a conveyor belt B and are being transported in the direction of arrow Y in FIG. Such an optical reading device 1 is installed. The workpiece W may flow not only at the center in the width direction of the upper surface of the conveyor belt conveyor B, but also on one side and the other side in an offset state in the width direction, so the workpiece W may not always pass through a fixed position. do not have.

The optical reading device 1 can be used, for example, at a distribution center. Objects (works W) of various sizes and shapes are transported at high speed on a transport belt conveyor B installed in a distribution distribution center. Furthermore, the distance between the works W in the transport direction is also set narrow.

As shown in FIG. 2, a plurality of codes CD1, CD2, CD3, CD4, and CD5 may be attached to a certain surface of the workpiece W, but there are also cases where only one code is attached. The first code CD1, the second code CD2, and the third code CD3 attached to the upper left of the work W are the codes to be read, and the fourth code CD4 and the third code attached to the upper right of the work W are the codes to be read. Code 5, CD5, is a code that is not to be read. The first to fifth codes CD1 to CD5 may be on the side surface of the work W, the top surface, the front surface, or the back surface.

In addition, in addition to the first to fifth codes CD1 to CD5, the first to eighth character strings L1 are attached to the same surface of the work W as the first to fifth codes CD1 to CD5. ~L8 is also attached. The first to third character strings L1 to L3 are placed close to the first to third codes CD1 to CD3 to be read, while the fourth to eighth character strings L4 to L8 are It is placed far from the first to third codes CD1 to CD3. Further, the workpiece W may have a pattern or the like attached thereto in addition to or in place of the character strings L1 to L8.

The workpiece W shown in FIG. 2 is an example, and the number and arrangement of codes, the presence or absence of character strings and patterns, etc. may vary; The fourth and fifth codes CD4 and CD5 and the first to eighth character strings L1 to L8 are spaced apart from the first to third codes CD1 to CD3. That is, the interval S1 between the first code CD1 and the second code CD2 and the interval S2 between the second code CD2 and the third code CD3 are the same as those between the third code CD3 and the character strings L1 to L18. It is set shorter than the interval S3 between the third code CD3 and the first character string L1 closest to it. Further, the interval S4 between the first to third codes CD1 to CD3 and the fourth and fifth codes CD4 and CD5 is set longer than the intervals S1 and S2. Therefore, among the first to fifth codes CD1 to CD5 and the first to eighth character strings L1 to L8, the first to third codes CD1 to CD3 constitute one group.

Although details will be described later, the areas where the first to fifth codes CD1 to CD5 are present on the read image of the workpiece W are areas that can become code candidate areas. In addition, even if the character strings L1 to L8 are not codes, the frequency may be high depending on the type of characters, character spacing, etc., just like the code. In this case, the character strings L1 to L8 are also code candidate areas. In some cases,

In this example, a case will be described in which the first to fifth codes CD1 to CD5 are one-dimensional codes, but they may be two-dimensional codes. Also, some of the first to third codes CD1 to CD3 to be read may be one-dimensional codes, and the remaining codes may be two-dimensional codes. A typical example of a one-dimensional code is a barcode, such as a JAN code, an ITF code, and GS1-128. Typical examples of two-dimensional codes are QR code (registered trademark), micro QR code, data matrix (Data code), Veri code, Aztec code, PDF417, and Maxi code. code) etc. Two-dimensional codes include stack type and matrix type, and the present invention can be applied to either type of two-dimensional code. The first to fifth codes CD1 to CD5 may be attached by directly printing or stamping on the workpiece W, or may be attached by printing on a label etc. and then pasting it on the workpiece W. , the method does not matter.

As shown in FIG. 1, the optical reading device 1 is a device that optically reads the first to third codes CD1 to CD3 (shown in FIG. 2) attached to the workpiece W. The first to third codes CD1 to CD3 attached to W are imaged to generate a read image, and the first to third codes CD1 to CD3 included in the generated read image are decoded by decoding processing. This is a code reader configured to be able to output results.

The optical reading device 1 can be configured as a stationary optical reading device that is fixed to a bracket or the like (not shown) so as not to move during operation. It may also be operated while being held and moved by someone else. Further, the first to third codes CD1 to CD3 of the workpiece W in a stationary state may be read by the optical reading device 1. During operation, the operation is performed to read the first to third codes CD1 to CD3 of the workpieces W sequentially conveyed by the conveyor belt B. The optical reading device 1 of this embodiment is suitable for situations where it is desired to read the first to third codes CD1 to CD3 attached to a workpiece W whose position changes, but is not limited to this. It can also be used to read the first to third codes CD1 to CD3 attached to W.

As shown in FIG. 1, the optical reading device 1 is wired to a computer 100 and a programmable logic controller (PLC) 101 as external control devices by signal lines 101a and 101a, respectively, but the invention is not limited to this. A communication module may be built into the optical reading device 1, the computer 100, and the PLC 101, and the optical reading device 1, the computer 100, and the PLC 101 may be wirelessly connected. The PLC 101 is a control device for sequentially controlling the transport belt conveyor B and the optical reading device 1, and a general-purpose PLC can be used.

The computer 100 can be a general-purpose or dedicated computer, a portable terminal, or the like. In this example, a so-called personal computer is used, and includes a control section 40, a storage device 41, a display section 42, an input section 43, and a communication section 44. By downsizing the optical reading device 1, it becomes difficult to perform all settings of the optical reading device 1 using only the display section 7, buttons 8, 9, etc. of the optical reading device 1, so the optical reading device 1 and Alternatively, a computer 100 may be prepared separately, and the computer 100 may perform various settings for the optical reading device 1 and transfer the setting information to the optical reading device 1.

Further, since the computer 100 includes the communication section 44, the computer 100 and the optical reading device 1 can be connected to enable bidirectional communication, so that a part of the processing of the optical reading device 1 described above can be performed by the computer 100. It's okay. In this case, part of the computer 100 becomes part of the components of the optical reading device 1.

The control unit 40 is a unit that controls each unit included in the computer 100 based on a program stored in the storage device 41. The storage device 41 includes various types of memories, hard disks, SSDs (Solid State Drives), and the like. The display section 42 is composed of, for example, a liquid crystal display. The input unit 43 includes a keyboard, a mouse, a touch sensor, and the like. The communication unit 44 is a part that communicates with the optical reading device 1. The communication unit 44 may include an I/O unit connected to the optical reading device 1, a serial communication unit such as RS232C, and a network communication unit such as a wireless LAN or wired LAN.

The control unit 40 displays a user interface image for setting the imaging conditions of the imaging unit 5 of the optical reading device 1, image processing conditions of the processing unit 23, etc., the decoding results output from the optical reading device 1, image data, etc. A user interface image and the like for display are generated and displayed on the display unit 42. The display unit 42 may constitute a part of the optical reading device 1. The storage device 41 is a part that stores decoding results that are the results of decoding processing performed by the processing unit 23, images captured by the imaging unit 5, various setting information, and the like.

Further, during operation, the optical reading device 1 receives a reading start trigger signal from the PLC 101 via the signal line 101a, which defines the timing to start reading the first to third codes CD1 to CD3. The optical reading device 1 then performs imaging and decoding processing of the workpiece W based on this reading start trigger signal. Thereafter, the decoding result obtained by the decoding process is transmitted to the PLC 101 via the signal line 101a. In this manner, during operation of the optical reading device 1, input of a reading start trigger signal and output of a decoding result are repeatedly performed between the optical reading device 1 and an external control device such as the PLC 101 via the signal line 101a. Note that the input of the reading start trigger signal and the output of the decoding result may be performed via the signal line 101a between the optical reading device 1 and the PLC 101, as described above, or via other signal lines (not shown). It may also be done through For example, a sensor for detecting that the workpiece W has arrived at a predetermined position may be directly connected to the optical reading device 1, and a reading start trigger signal may be input from the sensor to the optical reading device 1. . Furthermore, the decoding results, images, and various setting information can also be output to devices other than the PLC 101, such as the computer 100.

[Overall configuration of optical reading device 1]
As shown in FIGS. 4 to 6, the optical reading device 1 includes a housing 2 and a front cover 3. As shown in FIGS. As shown in FIG. 4, a lighting section 4, an imaging section 5, and an aimer 6 are provided on the front of the housing 2. The configurations of the illumination section 4 and the imaging section 5 will be described later. The aimer 6 is composed of a light emitting body such as a light emitting diode. The aimer 6 is used to indicate the imaging range of the imaging section 5 and the optical axis of the illumination section 4 by emitting light toward the front of the optical reading device 1. The user can also install the optical reading device 1 by referring to the light emitted from the aimer 6.

Further, as shown in FIG. 5, a display section 7, a select button 8, an enter button 9, and an indicator 10 are provided on one end surface of the housing 2. The configuration of the display section 7 will be described later. The select button 8 and the enter button 9 are buttons used for settings of the optical reading device 1, etc., and are connected to the control unit 20. The control unit 20 is capable of detecting the operating states of the select button 8 and the enter button 9. The select button 8 is a button that is operated when selecting one from a plurality of options displayed on the display section 7. The enter button 9 is a button operated when confirming the result selected with the select button 8. The indicator 10 is connected to the control unit 20 and can be constituted by a light emitter, such as a light emitting diode. The operating state of the optical reading device 1 can be notified to the outside by the lighting state of the indicator 10.

Further, as shown in FIG. 6, a power connector 11, a network connector 12, a serial connector 13, and a USB connector 14 are provided on the other end surface of the housing 2. Furthermore, a heat sink 15 serving as a rear case is provided on the back surface of the housing 2. Power wiring for supplying power to the optical reading device 1 is connected to the power connector 11 . The serial connector 13 is a signal line 100a, 101a connected to the computer 100 and the PLC 101, and the network connector 12 is an Ethernet connector. Note that the Ethernet standard is just one example, and signal lines of standards other than the Ethernet standard can also be used.

Further, inside the housing 2, a control unit 20, a storage device 50, an output section 60, etc. shown in FIG. 3 are provided. These will be described later.

In the description of this embodiment, the front and back sides of the optical reading device 1 are defined as described above, but this is only for the convenience of the description and does not limit the orientation when the optical reading device 1 is used. do not have. That is, as shown in FIG. 1, the optical reading device 1 may be installed and used with the front thereof facing almost downward, or the optical reading device 1 may be installed and used with the front of the optical reading device 1 facing upward. It is possible to install and use the optical reading device 1 so that the front face thereof faces downward and is inclined, or to use it so that the front surface of the optical reading device 1 runs along a vertical plane.

[Configuration of lighting section 4]
As shown by the broken line in FIG. 4, the illumination unit 4 is a member for irradiating light toward an area through which the workpiece W conveyed by the conveyor belt B passes. The light emitted from the illumination unit 4 illuminates at least a predetermined range in the conveyance direction by the conveyance belt conveyor B. This predetermined range is wider than the dimension in the same direction of the largest workpiece W expected to be transported during operation. The illumination unit 4 illuminates the first to third codes CD1 to CD3 attached to the work W being conveyed by the conveyor belt B.

The illumination unit 4 includes a light emitter 4a made of, for example, a light emitting diode, and there may be one or more light emitters 4a. In this example, a plurality of light emitters 4a are provided, and the imaging unit 5 faces the outside from between the light emitters 4a. Furthermore, light from the aimer 6 is emitted from between the light emitters 4a. The illumination section 4 is electrically connected to the imaging control section 22 of the control unit 20 and is controlled by the control unit 20, so that it can be turned on and off at arbitrary timing.

In this example, the illumination section 4 and the imaging section 5 are integrated into one housing 2, but the illumination section 4 and the imaging section 5 may be configured separately. In this case, the illumination section 4 and the imaging section 5 can be connected by wire or wirelessly. Further, a control unit 20, which will be described later, may be built into the illumination section 4 or the imaging section 5. The lighting unit 4 mounted on the housing 2 will be referred to as internal lighting, and the lighting unit 4 that is separate from the housing 2 will be referred to as external lighting. It is also possible to illuminate the workpiece W using both internal and external lighting.

[Configuration of imaging unit 5]
FIG. 3 is a block diagram showing the configuration of the optical reading device 1. As shown in FIG. The imaging unit 5 is a member for receiving light emitted from the illumination unit 4 and reflected from an area through which the workpiece W passes, and generating a read image of the area through which the workpiece W passes. As the imaging unit 5, an area camera in which pixels are arranged vertically and horizontally (in the X direction and the Y direction) can be used, which makes it possible to read two-dimensional codes and to read one workpiece W during transportation multiple times. It becomes possible to take images.

As shown in FIG. 3, the imaging unit 5 includes an imaging element 5a capable of imaging at least the portions of the workpiece W to which the first to third codes CD1 to CD3 are attached, an optical system 5b having lenses, etc., and an automatic A focus mechanism (AF mechanism) 5c is provided. Light reflected from at least the portions of the workpiece W to which the first to third codes CD1 to CD3 are attached is incident on the optical system 5b. The image sensor 5a is a light receiving element such as a CCD (charge-coupled device) or a CMOS (complementary metal oxide semiconductor) that converts an image including the first to third codes CD1 to CD3 obtained through the optical system 5b into an electrical signal. It is an image sensor consisting of

The AF mechanism 5c is a mechanism that performs focusing by changing the position and refractive index of a focusing lens among the lenses constituting the optical system 5b. The AF mechanism 5c is connected to the control unit 20 and controlled by the AF control section 21 of the control unit 20.

The image sensor 5a is connected to the image capture control section 22 of the control unit 20. The imaging device 5a is controlled by the imaging control unit 22, and can image the area through which the workpiece W passes at preset fixed time intervals, or image the area through which the workpiece W passes at an arbitrary timing by changing the time interval. It is configured to be able to image a region. The imaging unit 5 is configured to be able to perform so-called infinite burst imaging in which read images are continuously generated. As a result, it is possible to capture the first to third codes CD1 to CD3 of the work W that is moving at high speed into the read image without escaping them, and also to capture multiple images of one work W being conveyed multiple times. It becomes possible to generate a read image. Note that the imaging control section 22 may be built into the imaging section 5.

The intensity of the light received by the light-receiving surface of the image sensor 5a is converted into an electrical signal by the image sensor 5a, and the electrical signal converted by the image sensor 5a is sent to the processing section of the control unit 20 as image data constituting a read image. Transferred to 23.

[Configuration of display section 7]
The display section 7 is made of, for example, an organic EL display or a liquid crystal display. The display section 7 is connected to the control unit 20 as shown in FIG. The display unit 7 displays, for example, the first to third codes CD1 to CD3 captured by the imaging unit 5, character strings that are the decoding results of the first to third codes CD1 to CD3, the reading success rate, and the matching level ( reading margin), etc. can be displayed. The read success rate is the average read success rate when reading processing is executed multiple times. The matching level is a reading margin indicating the ease of reading the first to third codes CD1 to CD3 that have been successfully decoded. This can be determined from the number of error corrections that occur during decoding, and can be expressed, for example, as a numerical value. The fewer the error corrections, the higher the matching level (reading margin), and the more error corrections, the lower the matching level (reading margin).

[Configuration of storage device 50]
The storage device 50 is comprised of various memories, hard disks, SSDs, and the like. The storage device 35 is provided with a decoding result storage section 51, an image data storage section 52, and a parameter set storage section 53. The decoding result storage unit 51 is a part that stores the decoding result that is the result of the decoding process performed by the processing unit 23. The image data storage section 52 is a section that stores images captured by the imaging section 5. The parameter set storage unit 53 stores setting information set by a setting device such as the computer 100, setting information set by the select button 8 and enter button 9, and setting information obtained as a result of tuning performed by the tuning execution unit 24. This is the part that stores things like. The parameter set storage unit 53 stores a plurality of parameters that configure the imaging conditions of the imaging unit 5 (gain, light amount of the illumination unit 4, exposure time, etc.) and the image processing conditions of the processing unit 23 (type of image processing filter, etc.). A plurality of parameter sets including parameters can be stored.

[Configuration of output section 60]
The optical reading device 1 has an output section 60. The output section 60 is a section that outputs a decoding result that has been decoded by the processing section 23, which will be described later. Specifically, upon completion of the decoding process, the processing unit 23 transmits the decoding result to the output unit 60. The output unit 60 can be configured with a communication unit that transmits data regarding the decoding result received from the processing unit 23 to the computer 100 and the PLC 101, for example. The output unit 60 may include an I/O unit connected to the computer 100 and the PLC 101, a serial communication unit such as RS232C, and a network communication unit such as a wireless LAN or wired LAN.

[Configuration of control unit 20]
The control unit 20 shown in FIG. 3 is a unit for controlling each part of the optical reading device 1, and can be configured with a CPU, MPU, system LSI, DSP, dedicated hardware, etc. The control unit 20 is equipped with various functions as described below, but these may be realized by a logic circuit or by executing software.

The control unit 20 includes an AF control section 21, an imaging control section 22, a processing section 23, a tuning execution section 24, and a UI management section 25. The AF control section 21 is a section that performs focusing of the optical system 5b using conventionally well-known contrast AF or phase difference AF. The AF control section 21 may be included in the imaging section 5.

[Configuration of imaging control unit 22]
The imaging control section 22 is a section that not only controls the imaging section 5 but also controls the illumination section 4 . That is, the imaging control section 22 is configured with a unit that adjusts the gain of the imaging device 5a, controls the light amount of the illumination section 4, and controls the exposure time (shutter speed) of the imaging device 5a. The gain, the amount of light of the illumination section 4, the exposure time, etc. are included in the imaging conditions of the imaging section 5.

[Configuration of processing unit 23]
The processing section 23 is a section that executes decoding processing on the code candidate region extracted from the read image, and when the decoding processing is successful, generates a decoding result and sends it to the output section 60. The details of each process executed by the processing unit 23 will be described below using the flowchart in FIG.

This flowchart starts at the timing when the optical reading device 1 receives the reading start trigger signal, and ends at the timing when the operation stop operation is performed. After the start, in step SA1, the processing unit 23 acquires the read image 200 (shown in FIG. 8) generated by the imaging unit 5 from the imaging unit 5. A read image 200 shown in FIG. 8 is an image generated by capturing an image of the workpiece W shown in FIG. 2 from one side. This read image 200 includes first to fifth codes CD1 to CD5 attached to the workpiece W and first to eighth character strings L1 to L8.

After acquiring the read image in step SA1, the process proceeds to step SA2, and code search data generation processing is executed. Details of the code search data generation process are shown in FIG. In step SB1 after the start, edge detection processing is performed on the read image 200 to generate edge data. The edge detection process can be performed using, for example, a Sobel filter. For example, in the case of a one-dimensional code, if the rotation angle of the barcode is 0°, the sobel in the X direction, if it is 90°, the sobel in the Y direction, and if there is no prerequisite for the rotation angle of the barcode, the sobel in the X direction, the sobel in the Y direction. A composite image may be generated by adding them to the image.

In step SB1, for example, an edge intensity image, an edge angle image, etc. can be generated as the image after the edge detection process, and an image after common convolution processing or arithmetic processing may be generated. Furthermore, not only the first-order differential processing but also the second-order differential processing can be used as the edge detection processing.

In step SB2, the edge image data generated in step SB1 is acquired. Thereafter, the process proceeds to step SB3, where edge image data integration processing is performed to integrate edge image data of a certain pixel and its vicinity. For example, since there is a high possibility that a code exists in an area where pixels with large luminance values gather in edge image data, that area can be estimated as a candidate area for the code. By integrating a certain pixel forming edge image data and edge image data existing in its vicinity, it is possible to express an area where pixels with large luminance values gather. In this example, it is possible to execute product-sum calculation processing and pixel integration processing to generate data that measures the degree of aggregation of edge image data within a certain region. For example, smoothing processing can be used that has the effect of adding up pixel values within a specific window size. Further, reduction processing may be used. When reduction processing is used, the amount of data becomes smaller, so there is an advantage that the amount of scanning can be reduced.

By going through steps SB1 to SB3, it is possible to calculate the feature amount indicating code-likeness for each area in the image data. Since the code candidate region can be searched and extracted based on the feature amount, the calculated feature amount is acquired as code search data (step SB4). Note that it is also possible to generate a feature amount image to which a brightness value according to the calculated feature amount is assigned. The feature image can be a so-called heat map image, in which regions with large feature amounts can be displayed brighter or darker than regions with small features. The feature amount itself may be used as code search data without generating a heat map image.

It is also possible to generate code search data for one-dimensional codes and two-dimensional codes. That is, in the one-dimensional code edge image data integration process, the characteristics of the shape of the one-dimensional code are utilized to integrate edges whose edge directions are aligned. For example, edge angle images are generated, and those with close edge angles are added together, and those with far edge angles are subtracted. Furthermore, within a certain range of edge image data, a process may be performed in which image data with close edge directions are added and image data with different edge directions are subtracted. Furthermore, in the two-dimensional code edge image data integration process, the characteristics of the shape of the two-dimensional code are utilized to integrate edges with irregular edge directions. For example, edge angle images are generated and those with close edge angles are averaged. Furthermore, within a certain range of edge image data, a process of adding image data with different edge directions may be performed. As described above, the process of step SA2 in the flowchart shown in FIG. 7 is completed.

Thereafter, the process proceeds to step SA3, where the processing unit 23 uses the code search data to extract a code candidate area. The code candidate region is a region including a portion with a large feature amount indicating code-likeness, and the processing unit 23 extracts a region including a portion with a feature amount greater than or equal to a predetermined threshold value from the read image 200. One or more code candidate regions may be extracted depending on the number of codes included in the read image 200, and may further increase depending on the character strings included in the read image 200. Furthermore, the position of the code candidate area corresponds to the position of the code or character string included in the read image 200. Further, the size and shape of the code candidate area correspond to the size and shape of the code or character string included in the read image 200.

FIG. 10 is a diagram showing the code candidate area extracted in step SA3. This is an example in which a total of 13 code candidate areas with codes 501 to 513 are extracted. The regions where the first to third codes CD1 to CD3 in FIG. 8 are located are extracted as code candidate regions 501 to 503 in FIG. 10. The regions where the fourth code CD4 and fifth code CD5 in FIG. 8 are located are extracted as code candidate regions 504 and 505 in FIG. 10. The regions where the first to eighth character strings L1 to L8 are located are extracted as code candidate regions 506 to 513 in FIG. Although the first to eighth character strings L1 to L8 in FIG. 8 are not codes, they are extracted as code candidate areas 506 to 513 because they are high-frequency parts on the read image 200 like codes. Sometimes. Note that the black rectangle in FIG. 8 is clearly not a code, so the feature amount indicating the code-likeness is less than the threshold value, and it is not extracted as a code candidate region in FIG. 10.

After extracting the code candidate area in step SA3, the process proceeds to step SA4. In the first step SA4, a code candidate region to be first subjected to decoding processing is selected from among the plurality of code candidate regions extracted in step SA3. Specifically, the processing unit 23 calculates an estimated value of the number of modules or the number of elements for each of the plurality of extracted code candidate regions 501 to 013, and calculates the estimated value of the code candidate region in which the decoding process is to be performed. According to this, a code candidate area to be decoded first is selected. For example, the processing unit 23 executes a process of selecting one code candidate region whose calculated estimated value is closest to the value of the code to be read. In other words, the number of modules or elements constituting a code is a feature that does not depend on the area of the code in the read image 200, and by using such a feature, code candidate regions can be extracted at high speed. .

Thereafter, the process proceeds to step SA5. In step SA5, the processing unit 23 performs a decoding process on the one code candidate region selected in step SA4. After the decoding process, the process proceeds to step SA6, and the processing unit 23 determines whether or not the decoding process in step SA5 was successful. If the determination in step SA6 is NO and the decoding process is not successful, the process returns to step SA4, selects a code candidate area other than the initially selected code candidate area, and then proceeds to step SA5 to execute the decoding process. Then, it is determined again in step SA6 whether or not the decoding process was successful. Steps SA4 to SA6 are repeated until the decoding process is successful, thereby making it possible to sequentially perform the decoding process on the plurality of extracted code candidate areas.

If the decoding process for any of the code candidate areas is successful, the process proceeds to step SA7. In step SA7, the processing unit 23 determines whether or not the designated number of decoding processes has been successful. In this example, since the first to third codes CD1 to CD3 are the codes to be read, the specified number is 3, so the determination in the first step SA7 is NO and the process proceeds to step SA9. In step SA9, the processing unit 23 executes processing to limit the reading area.

At this time, in step SA9, area limiting parameters are used. The area limitation parameter is a parameter for excluding from the decoding processing target a code candidate area that is located away from the code candidate area that was successful in step SA5, and is set in advance. The region limitation parameters can be set by the user. When the user makes settings, the input unit 43 can be used as a reception unit that accepts the user's settings for area-limiting parameters. The region-limiting parameters received via the input unit 43 can be stored in the storage device 50, and can be read from the storage device 50 and used when executing step SA9.

A specific example of the process in step SA9 will be described in detail. First, the processing unit 23 acquires the position of the code candidate area that has been successfully decoded in step SA5. The position of the code candidate area that has been successfully decoded can be obtained by, for example, the X and Y coordinates on the read image 200. These coordinates may be the center of the code candidate area, a part of the periphery, or the position of the center of gravity.

The processing unit 23 acquires the position of the code candidate area that has been successfully decoded, and also acquires the area limiting parameter. Thereafter, the processing unit 23 determines a decoding processing area (indicated by reference numeral 550 in FIG. 11) based on the position of the code candidate area and the area limiting parameter. FIG. 11 shows an example in which the code candidate area 503 is first selected as a reading target and the decoding process for the code candidate area 503 is successful. The position of the code candidate area 503 that has been successfully decoded is obtained from the coordinates of the center 551 of the code candidate area 503. R1 is a region-limiting parameter, and the region-limiting parameter may be a predetermined coefficient. In this example, a circle having a radius R1 centered on the center 551 of the code candidate area 503 is determined as the decoding processing area 550. That is, since the radius of the decoding processing area 550 is used as the area-limiting parameter, the larger the area-limiting parameter, the wider the decoding processing area 550 becomes, and conversely, the smaller the area-limiting parameter, the narrower the decoding processing area 550 becomes. The region confinement parameter may be the diameter of a circle. Further, the decoding processing area 550 may be an ellipse or an ellipse, or may be various shapes such as a polygon. Even when these shapes are used, the size of each shape and the area of each drawing are A numerical value that defines the size can be used as a region-limiting parameter, and depending on the figure, two or more region-limiting parameters can be included. When the user sets or adjusts the region-limiting parameters, the settings or adjustments may be made stepless or stepwise.

The region-limiting parameters can also be automatically set when the optical reading device 1 is set. When setting the optical reading device 1, the tuning execution unit 24 acquires a read image 200 (shown in FIG. 8) including a plurality of codes from the imaging unit 5, and selects a plurality of code candidate areas 501 to 513 of the acquired read image 200. (shown in FIG. 10), the processing unit 23 executes the decoding process, and the area limitation parameter is set so that the plurality of code candidate areas 501 to 503 for which the decoding process has been successfully performed are included in the decoding process area 550 (shown in FIG. 11). Automatically set. In this example, since the code candidate areas 501 to 503 are to be read, during tuning, the decoding process for these code candidate areas 501 to 503 is successful, and the decoding process for other code candidate areas 504 to 513 is not successful. . If the decoding process is successful in any one of the code candidate areas 501 to 503, the tuning execution unit 24 limits the area so that the decoding process area 550 is large enough to include the other two code candidate areas. Parameters can be calculated and stored in the storage device 50.

When the process proceeds to step SA8 via step SA9 in the flowchart shown in FIG. 7, the processing unit 23 limits the code candidate area. When the decoding processing area 550 is determined as shown in FIG. 11, code candidate areas 504, 505, 508 to 513 located outside the decoding processing area 550 are excluded from the decoding processing targets. In FIG. 12, the code candidate areas excluded from the decoding target are deleted, and only code candidate areas 501 to 503, 506, and 507 to be decoded are shown. In other words, the processing unit 23 subjects only the code candidate regions 501 to 503, 506, and 507 that overlap the decoding processing region 550 to decoding processing. Furthermore, the processing unit 23 does not have to target the code candidate areas 501 to 503 located within the decoding processing area 550 and not target the code candidate areas 504 to 513 located outside the decoding processing area 550. . Therefore, when the processing unit 23 succeeds in decoding any of the code candidate regions 501 to 503, it generates a decoding result, and also generates a code candidate region 504 located at a position separated from the code candidate regions 501 to 503 where the code candidate region 503 was successfully decoded. 505, 508 to 513 are excluded from decoding processing targets.

After passing through step SA8, the process proceeds to step SA4. In step SA4 after step SA8, one of the code candidate regions 501, 502, 506, 507 that has not been subjected to decoding processing from among the code candidate regions 501 to 503, 506, and 507 limited in step SA8 is selected. Select one. At this time, a code candidate area can be selected based on the number of modules or the number of elements described above.

Assuming that the code candidate area 502 is selected in step SA4, decoding processing is performed on the code candidate area 502 in step SA5. Thereafter, the process proceeds to step SA6, and if the decoding process is successful, the process proceeds to step SA7. In step SA7, it is determined whether or not the specified number of decoding processes has been successful. At this stage, only two code candidate areas 503 and 502 have been successfully decoded, which is less than 3. , proceed to step SA9.

In the second step SA9, the reading area is limited again. That is, since the decoding process of the code candidate area 502 was successful, the processing unit 23 acquires the position of the code candidate area 502 that has been successfully decoded, and also acquires the area limiting parameter, and determines the position and area of the code candidate area 502. A decoding processing area (indicated by reference numeral 552 in FIG. 13) is determined based on the limiting parameters. The position of the code candidate area 502 can be obtained from the coordinates of the center 553 of the code candidate area 502. A circle having a radius R2 centered on the center 553 of the code candidate area 502 can be determined as the decoding processing area 552. The radius R2 is a region-limiting parameter, and may be different from or the same as the above R1. Thereafter, the process proceeds to step SA8, and the code candidate areas 501 to 503 within the decoding process area 552 are targeted for decoding.

That is, after determining the decoding processing area 550 (shown in FIG. 11) in the first step SA9, if the processing unit 23 succeeds in decoding another code candidate area 502 located within the decoding processing area 550, the processing unit 23 determines the decoding processing area 550 (shown in FIG. 11). A decoding processing area 552 (shown in FIG. 13) is newly determined based on the position of another code candidate area 502 and the area limiting parameter (R2), and the decoding processing area 552 is located within the newly determined decoding processing area 552. Code candidate areas 501 to 503 are targeted for decoding processing.

Thereafter, the process proceeds to step SA4, where the reading area is limited for the third time. Since the code candidate area 503 and the code candidate area 502 have been successfully decoded so far, the code candidate area 501 which has not yet been decoded in the decode process area 552 is selected as a decode target. Then, the process proceeds to step SA5, and decoding processing is executed on the code candidate area 501. If it is determined in step SA6 that the decoding process of the code candidate area 501 has been successful, the process proceeds to step SA7. Since the decoding process for the three code candidate areas 501 to 503 has been successful, the determination in step SA7 is YES and the process proceeds to step SA10. In step SA10, the output unit 60 outputs the decoding result.

[Changes in region-limited parameters]
The region limiting parameter may be a fixed value, or may be changed. For example, even when imaging workpieces W with codes CD1 to CD3 of the same size, if the distance between the workpiece W and the imaging unit 5 is short, the images may appear on the read image 200 as shown in FIG. When the codes CD1 to CD3 become large and the distance between the workpiece W and the imaging unit 5 is long, the codes CD1 to CD3 become small on the read image 200 as shown in FIG. 15. Therefore, if the area limitation parameter R is a fixed value, the size of the decoding processing area 550 may be too small in the case of large codes CD1 to CD3 on the read image 200 (as shown in FIG. 14), and In the case of small codes CD1 to CD3 on the image 200 (as shown in FIG. 15), the decoding processing area 550 is too large, and the decoding processing area 550 is a code candidate area in which the codes CD1 to CD3 are unlikely to exist. It is possible that it may fall into.

On the other hand, in this example, since the area limitation parameter R can be changed according to the size of the codes CD1 to CD3 on the read image 200, Therefore, it is possible to determine an appropriate decoding processing area. For example, as shown in FIG. 16, the processing unit 23 changes the area limiting parameter R so that the smaller the size of the codes CD1 to CD3 on the read image 200, the smaller the decoding processing area 550 becomes. Further, as shown in FIG. 17, the processing unit 23 changes the area limiting parameter R so that the larger the size of the codes CD1 to CD3 on the read image 200, the larger the decoding processing area 550.

More specifically, the size of the codes CD1 to CD3 on the read image 200 can be defined by, for example, the area of the code area and the size of the smallest module of the code. The region limiting parameter R can be changed based on the sizes of the codes CD1 to CD3. The region limiting parameter R can also be calculated, for example, by multiplying the sizes of the codes CD1 to CD3 on the read image 200 by a coefficient. The coefficients may be determined in advance.

[Operations and effects of embodiment]
As described above, according to this embodiment, when the workpiece W being conveyed on the line is irradiated with light from the illumination section 4 as shown in FIG. The light is received by. As a result, as shown in FIG. 8, a read image 200 including the workpiece W, the codes CD1 to CD5 attached to the workpiece W, and the character strings L1 to L8 is generated. The processing unit 23 executes an extraction process on the read image 200 and extracts code candidate areas 501 to 513 as shown in FIG. As in this example, multiple code candidate areas 501 to 513 may be extracted, and in addition to code candidate areas 501 to 505 that include codes CD1 to CD5, codes that do not include codes CD1 to CD5 Candidate regions 506-513 may be extracted.

When a plurality of code candidate regions 501 to 513 are extracted, the processing unit 23 sequentially performs decoding processing on the extracted plurality of code candidate regions 501 to 513. When the code candidate area 503 is successfully decoded as shown in FIG. 11, code candidate areas 504, 505, 508 to 513 located at a distance from the code candidate area 503 are excluded from the decoding targets as shown in FIG. .

That is, a case where a plurality of codes CD1 to CD3 to be decoded are attached to the workpiece W is assumed to be, for example, a case where a plurality of codes CD1 to CD3 are printed on one label and the code is attached to the workpiece W. For example, a plurality of codes CD1 to CD3 may be printed near the periphery of the workpiece W. In any of these cases, the plurality of codes CD1 to CD3 are often close to each other. Therefore, it is unlikely that the codes CD1 and CD2 to be decoded exist in a place far away from the code candidate area 503 that has been successfully decoded. By excluding certain code candidate areas 504, 505, 508 to 513 from the decoding target, decoding is performed only on the code candidate areas 501 and 502 where there is a high possibility that the codes CD1 and CD2 to be decoded exist. can be executed.

The embodiments described above are merely illustrative in all respects and should not be interpreted in a limiting manner. Furthermore, all modifications and changes that come within the scope of equivalents of the claims are intended to be within the scope of the present invention.

As described above, the optical reading device according to the present invention can be used, for example, to read codes such as barcodes and two-dimensional codes attached to workpieces.

1 Optical reading device 4 Illumination unit 5 Imaging unit 23 Processing unit 24 Tuning execution unit 550 Decode processing area CD1 to CD3 Codes to be decoded CD4, CD5 Codes not to be decoded L1 to L8 Character string

Claims (11)

A stationary optical reader that reads codes attached to workpieces being conveyed on a line,
an illumination unit for irradiating light toward an area through which the workpiece passes;
an imaging unit that receives light emitted from the illumination unit and reflected from a region through which the workpiece passes, and generates a read image of the region through which the workpiece passes;
If a plurality of code candidate regions are extracted as a result of the extraction process of extracting code candidate regions from the read image generated by the imaging unit, decoding processing is performed on the extracted plurality of code candidate regions in order. a processing unit that executes the above process and, when successfully decoding one of the code candidate regions, generates a decoding result and excludes a code candidate region located at a position distant from the successful code candidate region from the decoding processing target;
An optical reading device comprising: an output section that outputs a decoding result generated by the processing section. The optical reading device according to claim 1,
The processing unit determines a decoding processing area based on the position of a code candidate area that has been successfully decoded and a preset area limiting parameter, and selects a code candidate area located within the decoding processing area as a decoding processing target. Optical reading device. The optical reading device according to claim 2,
The processing unit is an optical reading device in which the code candidate area overlapping with the decoding processing area is subjected to decoding processing. The optical reading device according to claim 2 or 3,
The processing unit is an optical reading device that excludes the code candidate area located outside the decoding processing area from the decoding processing target. The optical reading device according to any one of claims 2 to 4,
When setting the optical reading device, a read image including a plurality of codes is acquired from the imaging unit, and the processing unit executes decoding processing on the plurality of code candidate areas of the acquired read image, and the decoding process is successful. An optical reading device comprising: a tuning execution unit that automatically sets the area limiting parameter so that a plurality of code candidate areas are included in the decoding processing area. The optical reading device according to any one of claims 2 to 5,
An optical reading device comprising: a reception unit configured to accept settings of the region-limiting parameters by a user. The optical reading device according to any one of claims 2 to 6,
After determining the decoding processing area, if the processing unit succeeds in decoding another code candidate area located within the decoding processing area, the processing unit performs a decoding process based on the position of the other code candidate area and the area limiting parameter. An optical reading device that newly determines a decoding processing area, and subjects a code candidate area located within the newly determined decoding processing area to a decoding processing target. The optical reading device according to any one of claims 2 to 7,
The processing section is an optical reading device that changes the area limiting parameter according to the size of the code on the read image. The optical reading device according to claim 8,
The processing section is an optical reading device that changes the area limiting parameter so that the smaller the size of the code on the read image, the smaller the decoding processing area. The optical reading device according to claim 8 or 9,
The processing section is an optical reading device that changes the area limiting parameter so that the larger the size of the code on the read image, the larger the decoding processing area. The optical reading device according to any one of claims 1 to 10,
The processing unit calculates an estimated value of the number of modules or the number of elements for each of the plurality of extracted code candidate regions, and selects a code candidate region to perform decoding processing according to the calculated estimated value.

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