JP2016148925A - Two-dimensional code reading apparatus and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two-dimensional code reading apparatus having an image memory of comparatively small capacity, while reducing probability of read failure.SOLUTION: A two-dimensional code reading apparatus includes: a two-dimensional imaging apparatus 11; memories 13, 33 for storing image data of a storage range 41 narrower than an imaging range 40 of the two-dimensional imaging apparatus, out of image data captured by the two-dimensional imaging apparatus; and an analysis section 50 which analyzes the image data of the storage range acquired by imaging, to analyze a two-dimensional code included in an image. The analysis section includes: a code search section 51 which searches an area of the two-dimensional code in the storage range; and a storage range control section 53 which controls a position of the storage range in the next imaging, in the imaging range, on the basis of a position of the area of the two-dimensional code searched by the code search section when an analysis of the two-dimensional code in the image data of the storage range fails.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a two-dimensional code reading apparatus and method.

A barcode is used as a means for adding information to an actual object. The one-dimensional barcode is related to the price of the product and contributes to improving the work efficiency of the cash register.
On the other hand, a two-dimensional code can store more data than a one-dimensional barcode. Therefore, it is used to associate relatively large data such as URLs with products, provide product guidance to consumers, and store work support data for workers.

  A two-dimensional code reader (two-dimensional code reader) is configured using a camera (imaging device) and a microprocessor. Recent improvements in semiconductor technology have led to improved component performance and lower prices, making it possible to wear wearable two-dimensional code readers. By making the code reader wearable, the user's hands are free. For this reason, it is expected to be used to reduce the workload of workers on the site who use the two-dimensional code.

  The processor analyzes the two-dimensional code from the image obtained from the camera and acquires code data. The installed memory includes a camera image storage area for storing an image obtained from the camera, a camera control information storage area for controlling the camera, a main program storage area for analyzing the image, and the main program temporarily storing data. Has a work area for storing.

  The two-dimensional code reader captures images according to the user's instructions, analyzes the captured images, outputs code data if the analysis is successful, and continuously analyzes images up to the specified number of times if the analysis fails. Repeat the shooting and analysis. If the analysis failure exceeds the specified number of times, the two-dimensional code reader enters an input waiting state.

  When a two-dimensional code reader is mounted on a wearable device, it is difficult to obtain a two-dimensional code image that can be processed for the following reason.

  One reason is that it is not possible to check the shooting contents in real time. The wearable device is desired to be small and light, and it is difficult to mount a large-capacity battery. Therefore, it is impossible to mount a display, and the user cannot check the captured image.

  Therefore, it has been proposed to provide a guide light irradiating unit that indicates the photographing position and provide the user with an alignment guideline. However, as described above, it is difficult to mount a large-capacity battery. There is no room to install a light source.

  Another reason is that the image memory (camera image storage area) is small. Since wearable devices are small and lightweight, it is difficult to mount a large-capacity memory because of the size and battery capacity. In recent years, the number of pixels of the imaging device has increased dramatically, but it is difficult to increase the capacity of the image memory for the above reasons, the storage range that the image memory can store is narrower than the imaging range, Only a part of the image of the generated imaging range can be stored. Since the analysis is performed on the image stored in the storage range, the analysis fails if the image of the two-dimensional code does not fall within the imaging range or if it falls within the imaging range but does not fall within the storage range. Will do.

Japanese Patent No. 2938338 JP 2000-157812 A JP 2004-157812 A Japanese Patent Laying-Open No. 2005-084890 Japanese Patent No. 4419269

  If the analysis of the captured image fails, the user will be asked to retry the shooting many times, which will be a burden on the work.

  Therefore, it is desired that a two-dimensional code reader having a relatively small capacity image memory can succeed in analyzing the two-dimensional code reliably.

  The two-dimensional code reading device according to the first aspect of the present invention includes a two-dimensional imaging device, a memory, and an analysis unit. The memory stores image data in a storage range narrower than the imaging range of the two-dimensional imaging device among the image data captured by the two-dimensional imaging device. The analysis unit analyzes the image data in the storage range acquired by imaging, and analyzes the two-dimensional code included in the image. The analysis unit includes a code search unit and a storage range control unit. The code search unit searches for a two-dimensional code area in the storage range. When the storage range control unit fails to analyze the two-dimensional code in the image data of the storage range, the storage range control unit determines whether the storage range in the next imaging is based on the position of the area of the two-dimensional code searched by the code search unit. Control the position.

  The two-dimensional code reading method of the second aspect of the present invention stores, in a memory, image data in a storage range narrower than the imaging range of the two-dimensional imaging device among the image data captured by the two-dimensional imaging device. Analyze the image data and analyze the 2D code contained in the image. According to the two-dimensional code reading method, the area of the two-dimensional code in the storage range is searched. Further, the analysis of the two-dimensional code with the image data in the storage range is performed, and when the analysis fails, the position of the storage range in the next imaging is controlled based on the position of the area of the searched two-dimensional code. .

  According to the embodiment, a two-dimensional code reader having an image memory having a relatively small capacity but a low probability of reading failure is realized.

FIG. 1 is a block diagram showing a configuration of a two-dimensional code reader. FIG. 2 is a diagram illustrating a configuration example of a camera (imaging device) mounted on a wearable code reader. FIG. 3 is a diagram showing the contents of the memory. FIG. 4 is a diagram illustrating the relationship between the camera image storage area of the memory and the imaging range of the imaging surface of the camera. FIG. 5 is a flowchart showing processing of the entire two-dimensional code reader. FIG. 6 is a flowchart showing details of the two-dimensional code analysis processing. FIG. 7 is a diagram illustrating an example of the imaging position of the two-dimensional code with respect to the imaging range and the storage range. FIG. 8 is a functional block diagram of an analysis unit realized by a processor in the two-dimensional code reader of the embodiment. FIG. 9 is a flowchart showing details of the two-dimensional code analysis processing of the embodiment. FIG. 10 is a diagram illustrating an imaging surface (imaging range) and an image coordinate system. FIG. 11 is a flowchart showing the search process. FIG. 12 is a diagram illustrating a storage range divided into a plurality of grids. FIG. 13 is a diagram illustrating an example of division into grids.

  Before describing the two-dimensional code reader (two-dimensional code reader) of the embodiment, a general two-dimensional code reader will be described.

  Recent improvements in semiconductor technology have led to improved component performance and lower prices, making it possible to wear wearable two-dimensional code readers. By making the code reader wearable, the user's hands are free. For this reason, it is expected to be used to reduce the workload of workers on the site who use the two-dimensional code.

FIG. 1 is a block diagram showing a configuration of a two-dimensional code reader.
The two-dimensional code reader includes a camera (imaging device) 11, a microprocessor 12, a memory 13, a DMA controller 14, an external communication module 15, an external input / output unit 16, and a bus 17 that connects the above parts. Have. In other words, the two-dimensional code reader has a camera and a computer.

  FIG. 2 is a diagram illustrating a configuration example of a camera (imaging device) mounted on a wearable code reader.

  The camera 11 includes a lens 21, an image sensor 22, a controller 24, and a connection cable 25. The lens 21 projects an optical image of the external object 100 onto the imaging surface 23 of the imaging element 22. The imaging element 22 converts the optical image projected on the imaging surface 23 into an electrical signal. The controller 24 reads the electrical signals corresponding to the light intensity in the rectangular imaging area of the imaging surface 23 in raster order and converts them into image data, and then transfers them to the main body (memory 13) of the code reader through the connection cable 25.

The memory 13 stores programs and data that cause the processor 12 to perform image analysis.
FIG. 3 is a diagram showing the contents of the memory.

  The capacity of the memory 13 is divided into a main program storage area 31, a camera control information storage area 32, a camera image storage area 33, and a main program work area 34. The camera image storage area 33 stores image data obtained from the camera 11. The camera control information storage area 32 stores camera control information for controlling the camera. The main program storage area 31 stores a program that causes the processor 12 to perform processing for analyzing an image. The main program work area 34 temporarily stores data generated during the operation of the main program. The memory 13 is a volatile memory such as SRAM (Static RAM) or DRAM (Dynamic RAM), a nonvolatile memory such as a flash memory, or a part of which is nonvolatile and partly volatile. Is also possible.

The DMA controller 14 reads the image data obtained from the camera 11 and writes it in the camera image storage area 33 of the memory 13.
The processor 12 analyzes the two-dimensional code from the image data written in the camera image storage area 33 and acquires the code data.

The external input / output unit 16 is connected to buttons, switches, and LEDs for power on (ON) state display.
The external communication module 15 is a module that connects the two-dimensional code reader and an external system. Although the communication form is not limited, USB, Bluetooth (registered trademark) or the like is used.

FIG. 4 is a diagram illustrating the relationship between the camera image storage area of the memory and the imaging range of the imaging surface of the camera.
Since wearable devices are small and light, it is difficult to mount a large-capacity memory because of the increase in size, battery capacity, and computational load. In recent years, the number of pixels of the imaging device has increased dramatically, but it is difficult to increase the capacity of the image memory for the above reasons, and as shown in FIG. 4, the storage range that the image memory can store is the imaging range. More narrowly, the image memory can store only a part of the image of the generated imaging range. Since the analysis is performed on the image stored in the storage range, the analysis fails not only when the image of the two-dimensional code does not fall within the imaging range but also when it enters the imaging range but does not fall within the storage range. It will be. FIG. 4 shows an example in which the center of the storage range coincides with the center of the imaging range, but the position of the storage range within the imaging range can be arbitrarily set.

FIG. 5 is a flowchart showing processing of the entire two-dimensional code reader.
The processing as a whole has an infinite loop structure while power is supplied.
In step S1, the process waits until an instruction from the external input / output 16 is received. If there is an instruction, the process proceeds to step S2.

In step S2, an image is read from the camera 11 according to the instruction, analyzed, and the process proceeds to step S3.
In step S3, it is determined whether the analysis is successful or unsuccessful. If successful, the process proceeds to step S4, and if unsuccessful, the process returns to step S2. Here, it is assumed that the steps S2 and S3 when the analysis fails are continuously performed up to the specified number of times, and the process proceeds to step S4 even when the analysis failure exceeds the specified number of times.

  In step S4, the analysis result is transmitted to the host device of the two-dimensional code reader. That is, the code data of the analyzed two-dimensional code is notified when the analysis is successful, and the analysis failure is notified when the analysis failure exceeds the specified number of times. When the two-dimensional code reader has an output device for displaying the analysis result, the analysis result is output from the output device.

FIG. 6 is a flowchart showing details of the two-dimensional code analysis processing.
Among the steps shown in FIG. 6, the three steps of code search (S13), code normalization (S15), and code decoding (S17) are the main steps of the two-dimensional code analysis process.

In step S11, the camera 11 is first initialized, and the image acquisition size, the white balance of the image sensor, the gamma value, and the like are set.
In step S12, the camera 11 captures an image, transfers it to the captured camera image storage area 33 using the DMA controller 14, and acquires an image.

In step S13, it is searched where the two-dimensional code appears from the photographed image.
In step S14, it is determined whether or not the two-dimensional code can be found in step S13. If the search is successful, the process proceeds to step S15. If the search is not successful, the process proceeds to step S20.

  In step S15, if the search is successful and the location where the two-dimensional code is shown is known, the code is normalized. Normalization is to rotate the code to the correct position and replace the black and white information of the code with the contents of 0 and 1.

  In step S16, it is determined whether normalization of the two-dimensional code is successful in step S15. If normalization is successful, the process proceeds to step S17. If normalization is not successful, the process proceeds to step S20.

  In step S17, the code is decoded based on the normalized two-dimensional code information. As a result of the decoding, if the error is detected, the analysis is unsuccessful, and if the error is not detected, the analysis is successful.

  In step S18, it is determined whether the analysis of the two-dimensional code is successful in step S17. If the analysis is successful, the process proceeds to step S19. If the analysis is not successful, the process proceeds to step S20.

In step S19, the analysis success is returned.
In step S20, an analysis failure is returned.
The success or failure of analysis in steps S19 and S20 is transmitted as an analysis result.

  The configuration and analysis processing of the two-dimensional code reader (reading device) are described in Patent Document 1 and are widely known, and thus further description thereof is omitted.

  When a two-dimensional code reader is mounted on a wearable device, it is difficult to obtain a two-dimensional code image that can be processed for the following reason.

  One reason is that wearable devices are desired to be small and light, and it is difficult to mount a large-capacity battery, so it is not possible to mount a display and the user can check the captured image in real time. Is not possible. For this reason, imaging and analysis are repeated many times until success, and if the analysis is not successful within the specified number of times, reading will fail, and the user will be retried to shoot many times, which is a burden on the work. Become.

  Therefore, Patent Document 4 proposes to provide a guide light irradiating unit indicating a photographing position and provide a user with an alignment guide, but it is difficult to mount a large-capacity battery as described above. Therefore, there is no room for mounting a light source for guide.

  Another reason is that the image memory (camera image storage area) is small as described above. Since wearable devices are small and lightweight, it is difficult to mount a large-capacity memory because of the size, battery capacity, and increased processing capacity. If the captured image of the two-dimensional code does not fall within the storage range of FIG. 4, the analysis fails.

  For the above two reasons, it is difficult for a two-dimensional code reader (reading device) mounted on a wearable device to accurately capture and analyze an image of a two-dimensional code, and reading fails many times. It was. This is not limited to the one mounted on the wearable device, and has the same problem as long as the display is not mounted and the two-dimensional code reader has a small image memory.

  The two-dimensional code reader (reading device) of the embodiment described below improves the probability of successful analysis within a specified number of times, and reduces the work load on the user.

In order to solve the above problem, attention is paid to the relationship between the imaging range and the storage range shown in FIG.
In the camera 11 of FIG. 2, an image reflected on the imaging surface 23 of the imaging element 22 through the lens 21 is transferred to the camera image storage area 33 of FIG. 3 via the DMA controller 24. At this time, information reflected on the imaging surfaces 23 of all the imaging elements 22 is not transferred to the camera image storage area 33, but only the amount stored in the camera image storage area 33 is transferred.

  For example, as illustrated in FIG. 4, the imaging element 22 has an imaging range 40 that can acquire an image of 640 × 480 pixels at the maximum. However, what is transferred to the camera image storage area 33 is image data in the storage range 41 having a size of 320 × 240 pixels. This is because, as described above, it is difficult to mount a large-capacity memory because of the size, battery capacity, and increase in processing amount, and an image in a small area is transferred for the convenience of the memory size.

FIG. 7 is a diagram illustrating an example of the imaging position of the two-dimensional code with respect to the imaging range and the storage range.
Actually, the image of the two-dimensional code is projected in a distorted manner instead of a square, and the edge of the image and the edge of the imaging range and the storage range are not always parallel. However, FIG. 7 shows an example in which the edges of the square image of the two-dimensional code are photographed so as to be parallel to the edges of the imaging range and the storage range in order to simplify the description. This is the same in the following description, and the analysis processing of the two-dimensional code when the acquired two-dimensional code image is distorted and rotated is described in Patent Document 1, Patent Document 5, and the like. The techniques disclosed in them can be used.

  As shown in FIG. 7, when a photographed two-dimensional code image 42 is projected onto the boundary of the storage range 41, only a part of the two-dimensional code is included in the image to be analyzed. Therefore, if the code analysis process is performed on an image as shown in FIG. 7, the analysis fails. However, although it cannot be acquired as an analysis target image, the imaging range 40 may include the entire image 42 of the two-dimensional code.

  As described above, the position of the storage range 41 within the imaging range 40 can be arbitrarily set. Therefore, when acquiring the next frame image, it is expected that the entire two-dimensional code can be included in the storage range by shifting the range to be transferred to the camera image storage area 33, that is, the storage range. In the embodiment, as a result of the code analysis for the image in the storage range, only a part of the two-dimensional code is included, and if the analysis fails, according to the position of the part determined to be a part of the two-dimensional code, The position of the storage range with respect to the imaging range when acquiring the next frame image is changed. The position of the image stored in the storage range is determined by designating the image acquisition position. Here, the position in the imaging range of the upper left corner of the storage range is designated as the image acquisition position.

  The two-dimensional code reader (reading device) of the embodiment has the same configuration as the above-described general two-dimensional code reader, and the analysis processing of the two-dimensional code after the analysis fails is different, and the others may be the same. .

FIG. 8 is a functional block diagram of an analysis unit realized by a processor in the two-dimensional code reader of the embodiment.
As shown in FIG. 8, the image data generated by the camera (imaging device) 11 is transferred to the camera image storage area 33 of the memory 13 for the range set by the storage range (image acquisition position) setting data. The analysis unit 50 includes a code search unit 51, an analysis processing unit 52, and a storage range control unit 52. The code search unit 51 searches a region of the two-dimensional code in the image data stored in the camera image storage region 33 and outputs the position of the two-dimensional code that is the search result to the analysis processing unit 52. Based on the search result from the code search unit 51, the analysis processing unit 52 performs code normalization processing and code decoding processing on the image data stored in the camera image storage area 33. When the storage range control unit 52 receives a notification that the code analysis has failed from the notification analysis processing unit 52, the storage range control unit 52 acquires information regarding the position of the area of the two-dimensional code searched from the code search unit 51 and outputs the information to the camera 11. The storage range (image acquisition position) setting data to be changed is changed. Thereby, the storage range of the image data stored in the camera image storage area 33 is changed. Note that when the code search unit 51 fails in the code search, the analysis processing unit 52 does not perform the analysis process, but when the code search unit 51 generates information related to the region estimated to be a two-dimensional code, The storage range of the image data may be changed based on the information.

  In FIG. 8, the portion excluding the storage range control unit 53 is the same as that of a general two-dimensional code reader. In a general two-dimensional code reader, the storage range setting data set in the camera 11 is fixed or can be set, but once set, it is not changed according to the analysis result. In other words, the storage range of the image data stored in the camera image storage area 33 is fixed with respect to the imaging range or can be set, but once set, it is not changed according to the analysis result. .

FIG. 9 is a flowchart showing details of the two-dimensional code analysis processing of the embodiment.
In FIG. 9, steps S33-S35 and S37-S42 correspond to S12-S20 of FIG. 6, and the two-dimensional code analysis processing of the embodiment adds steps S31, S32, and S36. And different.

  In step S31, the previous code detection position is acquired first. If this search is the first search, the code detection position is the center of the imaging range 40. The first time is, for example, a case where a predetermined time or more has elapsed since the previous shooting. On the other hand, not being the first time is, for example, a case where the number of retries is within a specified number.

  In step S32, the camera 11 is initialized, and an image data acquisition range in the imaging range 40, that is, a storage range 41 is set. At this time, the previous code detection (estimation) position is set to be near the center of the storage range 41.

  In step S33, the camera 11 captures an image, transfers it to the captured camera image storage area 33 using the DMA controller 14, and acquires an image.

In step S34, the location where the two-dimensional code appears in the photographed image is searched. The search process will be described later.
In step S35, it is determined whether or not the two-dimensional code can be found in step S34. If the search is successful, the process proceeds to step S36. If the search is not successful, the process proceeds to step S42.

  In step S 36, the searched position of the two-dimensional code is stored in the camera control information storage area 32 of the memory 13. The stored detection position is used in steps S31 and S32 at the time of the next shooting when the analysis fails.

  In step S37, the code is normalized with respect to the code image in the area where the two-dimensional code is shown. Normalization is to rotate the code to the correct position and replace the black and white information of the code with the contents of 0 and 1.

  In step S38, it is determined whether normalization of the two-dimensional code is successful in step S37. If normalization is successful, the process proceeds to step S39. If normalization is not successful, the process proceeds to step S42.

  In step S39, the code is decoded based on the normalized two-dimensional code information. As a result of the decoding, if the error is detected, the analysis is unsuccessful, and if the error is not detected, the analysis is successful.

  In step S40, it is determined whether the analysis of the two-dimensional code is successful in step S39. If the analysis is successful, the process proceeds to step S41. If the analysis is not successful, the process proceeds to step S42.

In step S41, the analysis success is returned.
In step S42, an analysis failure is returned.

Next, the storage range setting process in the imaging range will be described in detail.
FIG. 10 is a diagram illustrating an imaging surface (imaging range) and an image coordinate system.
The imaging plane and the image coordinate system are considered in the row direction and the column direction. As shown in FIG. 10, the row direction is from the top to the bottom of the image, and starts from 0 as shown in FIG. Here, the row coordinate is represented by y. Similarly, the column direction is from the left to the right of the image and starts from 0. Here, the column coordinates are represented by x. Depending on the type of camera, the row direction can be from the bottom to the top of the image.

  The storage range 41 for acquiring and storing image data in the imaging range 40 is set by setting a register inside the camera 11. This register is set via an interface (I2C or SPI) that connects the processor and the camera.

The camera 11 has a register for setting an acquisition start row, an acquisition start column, an acquisition width, and an acquisition height. Some cameras set an acquisition end row and an acquisition end column instead of an acquisition width and acquisition height. In this case, the acquisition end row and the acquisition end column are set by the following relational expression.
Acquisition end row = acquisition start row + acquisition height Acquisition end column = acquisition start column + acquisition width The embodiment may adopt any method, and the width and height of the acquired image do not change. Acquisition height does not change.

FIG. 11 is a flowchart showing the search process.
Various methods have been proposed for the search process, and any search process may be used in the embodiment. The search process shown in FIG. 11 is a process example described in Patent Document 5.

  In step S101, the input image (image data in the storage range) is scanned in units of blocks, and a block that satisfies a predetermined condition is detected as a code block. The shape of the block is arbitrary, for example, a rectangular block having horizontal M pixels and vertical N pixels. The predetermined conditions are, for example, (1) a range in which the black pixel ratio in the block is within a certain range, (2) a range in which there is a ratio of change points between white pixels and black pixels, and (3) black in the block. An identification condition depending on how the pixels are connected, and (4) an identification condition based on the projection variation of the black pixels in the block. Although details are described in Patent Document 5 and are omitted, it can be determined whether or not the block has a high probability of existence of a two-dimensional code under any of the above conditions.

In step S102, an area composed of code blocks to be linked with respect to the code block detected in step S101 is detected.
In step S103, the largest area among the areas constituted by the linked code blocks is detected as a two-dimensional code area.

  In the embodiment, steps S104 and S105 are performed as a code normalization process, not as a code search process. In step S104, a two-dimensional code image is extracted from the detected two-dimensional code region. In step S105, the inclination angle of the two-dimensional code is detected, and if necessary, inclination correction is performed.

In the embodiment, the center position of the area determined as the two-dimensional code area is estimated. The estimation of the center position is, for example, the middle position of the uppermost block and the lower block among the blocks in the two-dimensional code area as the vertical center position (the center position of the y coordinate), and the leftmost and rightmost positions. The middle of the center position of the block is defined as the horizontal center position (the center position of the x coordinate). Alternatively, the center position may be calculated by adding the center positions of the blocks in the two-dimensional code area and dividing by the number of blocks in the two-dimensional code area.
As described above, the center position of the two-dimensional code area is estimated. Hereinafter, the estimated center position is referred to as an estimated position.

  Next, the process of changing the range for acquiring an image from the camera at the next frame according to the estimated position of the two-dimensional code in step S32 will be described.

First, in the difference calculation, a difference in the row direction and a difference in the column direction are obtained.
Difference in row direction = estimated position in the row direction of the code-position in the row direction at the center of the storage range Difference in the column direction = estimated position in the column direction of the code-position in the column direction at the center of the storage range Is above the storage range center, the difference in the row direction is a negative value. When the estimated position of the code is below the center of the storage range, the difference in the row direction is a positive value. If the estimated position of the code is on the left side of the storage range center, the difference in the column direction is a negative value. If the estimated position of the code is on the right side of the storage range center, the difference in the column direction is a positive value. It becomes.

  Using this difference value, the image acquisition position in the next frame is calculated. First, the difference in the column direction is added to the position in the column direction of the current acquisition position (the upper left corner position of the storage range) to obtain the acquisition position in the column direction of the storage range to be acquired next. Similarly, the difference in the row direction is added to the position in the row direction of the current acquisition position to obtain the acquisition position in the row direction of the next acquisition position.

  Furthermore, even if an image is acquired from the next acquisition position, it is confirmed that it is within the imaging range, and if it does not fit, the acquisition position is adjusted. In other words, it is determined whether the storage range to be acquired next falls within the imaging range. If not, the next acquisition position is set according to the boundary of the imaging range.

  Specifically, when the position in the column direction of the next acquisition position is smaller than 0, the position in the column direction of the next acquisition position is set to 0. When the position in the column direction of the next acquisition position is larger than (length in the column direction of the imaging range) − (length in the column direction of the storage range), the next acquisition position is set to (column direction of the imaging range). The length of the storage range in the column direction).

  When the position in the row direction of the next acquisition position is smaller than 0, the position in the row direction of the next acquisition position is set to 0. When the position in the row direction of the next acquisition position is larger than (length in the row direction of the imaging range) − (length in the row direction of the storage range), the position in the row direction of the next acquisition position is ( The length of the imaging range in the row direction) − (the length of the storage range in the row direction).

  For example, the size of the imaging range is 640 × 480 (column direction coordinate values 0 to 639, row direction coordinate values 0 to 479), and the storage range size is 320 × 240 (column direction coordinate values 0 to 319). Assume that the row direction coordinate value is 0 to 239).

At this time, the center of the imaging range is 320 in the column direction and 240 in the row direction, and the center of the storage range is 160 in the column direction and 120 in the row direction.
At the time of the first shooting, the acquisition position is set to 160 in the imaging range for the column direction position and 120 to the imaging range for the row direction so that the center of the imaging range matches the center of the storage range.

  Next, as a result of code search, it is determined that the estimated position of the code center is in the column direction 100 and the row direction 100, and code normalization and decoding have failed. At this time, the acquisition position is changed as follows in the next frame.

Difference in row direction = estimated position in the row direction at the code center−position in the row direction at the center of the storage range = 100−160 = −60
Difference in column direction = estimated position in the column direction at the code center−position in the column direction at the center of the storage range = 100−120 = −20

Column direction position of next acquisition position = column direction position of current acquisition position + column direction difference = 160 + (− 60) = 100
Next acquisition position in row direction = Current acquisition position in row direction + Row direction difference = 120 + (− 20) = 100

  In this case, since the position in either direction is within the imaging range, the next frame is imaged at this position.

  Further, as a result of code search using the image at the changed acquisition position, it is assumed that the estimated position of the code center is calculated to be the column direction position 10 and the row direction position 10, and code normalization and decoding have failed. At this time, the acquisition position is further changed in the next frame.

Difference in row direction = estimated position in the row direction of the code−position in the row direction at the center of the storage range = 10−160 = −150
Difference in column direction = estimated position in the column direction of the code−position in the column direction at the center of the storage range = 10−120 = −110

Column direction position of next acquisition position = column direction position of current acquisition position + column direction difference = 100 + (− 150) = − 50
Next acquisition position in the row direction = current acquisition position in the row direction + difference in the row direction = 100 + (− 110) = − 10

  In this case, since the acquisition position exceeds the imaging range, correction is necessary. As a result of correction, the position of the next acquisition position in the column direction = 0 and the position of the next acquisition position in the row direction = 0. .

  The processing for estimating the center position of the two-dimensional code and the processing for changing the image acquisition position are performed in units of pixels. However, in order to reduce the amount of calculation, it is also possible to perform the processing in units of grids including a plurality of pixels. . Hereinafter, a modified example of processing in grid units will be described.

In this modification, the storage range 41 is divided into a plurality of grids.
FIG. 12 is a diagram illustrating a storage range divided into a plurality of grids.

  In FIG. 12, the storage range 41 is divided into row-direction line (vertical line) grids x0, x1,... Xm (m: integer of 1 or more) and column-direction line (horizontal line) grids y0, y1,. Is an integer greater than or equal to: 1) and is divided into the same rectangular grid area of m × n. However, the grids x0 and xm are the values of the left and right edges of the storage range 41 (x0 = 0, xm = the width of the image), and the grids y0 and yn are the values of the upper and lower edges of the storage range 41 (y0 = 0, yn = image height).

  In FIG. 12, the imaging range 40 is divided into a grid including the outside and inside of the storage range 41. That is, the column direction is divided into the following m + 2 areas including the outside and inside of the storage range 41.

Area smaller than grid x0 Area smaller than grid x0, smaller than grid x1 Area larger than grid x1 and smaller than grid x2 ...
Area greater than or equal to grid xi and smaller than grid x (i + 1)
Area greater than grid x (m-1) and smaller than grid xm Area larger than grid xm

Similarly, the row direction is divided into the following n + 2 areas including the outside and inside of the storage range 41.
Area smaller than grid y0 Area larger than grid y0 and area smaller than grid y1 Area larger than grid y1 and smaller than grid y2 ...
Area greater than or equal to grid yi and smaller than grid y (i + 1)
Area greater than or equal to grid y (n−1) and smaller than grid yn Area larger than grid yn Therefore, the area is divided into (m + 2) × (n + 2) areas including the inside and outside of the storage range 41.

FIG. 13 is a diagram illustrating an example of division into grids.
In FIG. 13, m = 3 and n = 3, and the grids are x0 = 0, x1 = 106, x2 = 212, x3 = 320, y0 = 0, y1 = 80, y2 = 160, and y3 = 240. As a result, as shown in FIG. 13, it is divided into three in the row direction and three in the column direction inside the storage range 41 to form a total of nine grid areas, including the outside, respectively in the row direction and the column direction. Since it is divided into five, there are a total of 25 grid areas.

The grid area is preferably larger than the code search block described above and includes a plurality of blocks.
The above-described estimation of the median value of the two-dimensional code area may be made by determining which grid area the estimated median value falls into. Therefore, it is determined in which grid area the median value of the two-dimensional code area estimated by the above method is included. A difference is assigned to each grid area in advance, and the next image acquisition position is changed according to the difference assigned to the grid area.

  In addition, in the above-described search for the block of the two-dimensional code, the grid area including the most blocks having a high probability of existence of the two-dimensional code is regarded as the “grid area including the estimated central position of the code”. Then, the next image acquisition position may be changed according to the difference assigned to the grid area.

Whether or not the grid area includes the corresponding block is determined by whether or not the grid area includes the center coordinates of the corresponding block.
Next, the assignment of the difference to the grid area will be described.

  As shown in FIG. 12, the difference in the row direction and the column direction is respectively assigned to the (m + 2) × (m + 2) divided grid areas including the inside and the outside of the storage area 41. However, the following conditions must be satisfied.

  (1) For any two divided grid areas with different positions (x coordinates) in the column direction, the difference in the column direction associated with the left grid area is the column associated with the right grid area. Less than or equal to the direction difference.

  (2) For any two divided grid areas having different positions (y coordinates) in the row direction, the difference in the row direction associated with the upper grid area is the line associated with the lower area. Less than or equal to the direction difference.

  FIG. 13 shows an example of the difference assigned so as to satisfy the above conditions (1) and (2). Using this difference value, the image acquisition position in the next frame is calculated.

First, the difference in the column direction is added to the position in the column direction of the current image acquisition position to obtain the column direction position of the next acquisition position.
Further, the difference in the row direction is added to the position in the row direction of the current image acquisition position to obtain the position in the row direction of the next acquisition position.

Next, even if an image is acquired from the next acquisition position, it is confirmed that it will fit on the imaging surface, and if it does not fit, the acquisition position is adjusted.
Specifically, when the position in the column direction of the next acquisition position is smaller than 0, the position in the column direction of the next acquisition position is set to 0.

  When the position in the column direction of the next acquisition position is larger than (length in the column direction of the imaging range) − (length in the column direction of the storage range), the position in the column direction of the next acquisition position is ( The length of the imaging range in the column direction) − (the length of the storage range in the column direction).

When the position in the row direction of the next acquisition position is smaller than 0, the position in the row direction of the next acquisition position is set to 0.
When the position in the row direction of the next acquisition position is larger than (length in the row direction of the imaging range) − (length in the row direction of the storage range), the position in the row direction of the next acquisition position is ( The length of the imaging range in the row direction) − (the length of the storage range in the row direction).

A processing example using this method will be described with reference to FIG.
First, let the image acquisition position from the imaging range (the position of the upper left corner of the storage range)) be the column direction position 160 and the row direction position 120.

  As a result of the code search, it is assumed that the estimated position of the code center is calculated as the column direction position 100 and the row direction position 100, and the code normalization and decoding have failed. At this time, the image acquisition position in the next frame is changed.

  First, since the estimated position of the code center is found at the column direction position 100 and the row direction position 100, the grid area surrounded by the grids x0 and x1 and the grids y1 and y2 in FIG. Become. The difference assigned to the grid area is −160 in the column direction and 0 in the row direction.

  When a difference is added to the current acquisition position, the image acquisition position in the next frame is 0 in the column direction position and 120 in the row direction position. Since this position is within the range of the imaging surface, this position is set as an image acquisition position for the next frame.

  Further, as a result of code search for the image stored in the storage range at this acquisition position, it is assumed that the estimated position of the code center is found at the column direction position 10 and the row direction position 10 and the code normalization and decoding have failed. At this time, the captured image acquisition position is further changed in the next frame.

  The grid area corresponding to this position is a grid area surrounded by the grids x0 and x1 and the grids y0 and y1 in FIG. 13, and the difference assigned to this grid area is −160 in the column direction and the difference in the row direction. The difference is -120.

  When a difference is added to the current acquisition position (0, 120), the image acquisition position in the next frame is -160 in the column direction and 0 in the row direction. Since this position is outside the imaging surface, the acquisition position is adjusted. As a result of the adjustment, the image acquisition position is 0 in the column direction position and 0 in the row direction position.

  As described above, according to the embodiment, the number of shooting retries can be reduced, and the detection time can be shortened. As a result, the operation time of the processor is shortened and the power consumption of the system is reduced.

  The two-dimensional code reader (reading device) of the embodiment has been described above, but it goes without saying that various modifications are possible. In the above example, the image acquisition position is set so that the center of the imaging range coincides with the center of the storage range as the first shooting except for shooting within the specified number of retries, but for example, the same use of a two-dimensional code reader When the user uses it, the image acquisition position when the previous analysis was successful may be stored and used. As a result, the trap when the user uses the two-dimensional code reader can be reflected, and the possibility that the two-dimensional code can be analyzed with the image acquired by the first photographing is improved.

  The embodiment has been described above, but all examples and conditions described herein are described for the purpose of helping understanding of the concept of the invention applied to the invention and technology. In particular, the examples and conditions described are not intended to limit the scope of the invention, and the construction of such examples in the specification does not indicate the advantages and disadvantages of the invention. Although embodiments of the invention have been described in detail, it should be understood that various changes, substitutions and modifications can be made without departing from the spirit and scope of the invention.

11 Camera (imaging device)
DESCRIPTION OF SYMBOLS 12 Processor 13 Memory 14 DMA controller 22 Image sensor 23 Imaging surface 24 Controller 33 Camera image storage area 40 Imaging range 41 Storage range 50 Analysis part 51 Code search part 52 Analysis processing part 53 Storage range control part

Claims (8)

A two-dimensional imaging device;
Of the image data captured by the two-dimensional imaging device, a memory that stores image data in a storage range narrower than the imaging range of the two-dimensional imaging device;
Analyzing the image data of the storage range acquired by imaging, and analyzing a two-dimensional code included in the image,
The analysis unit
A code search unit for searching a region of a two-dimensional code in the storage range;
Based on the position of the region of the two-dimensional code searched by the code search unit when the analysis of the two-dimensional code in the image data of the storage range fails, the position in the imaging range of the storage range in the next imaging A two-dimensional code reading device comprising: a storage range control unit that controls   The two-dimensional code reading device according to claim 1, wherein the code search unit divides the storage range into a plurality of blocks and determines a block including the image of the two-dimensional code as a code block.   The storage range control unit determines a region of a two-dimensional code from the set of code blocks, and in the next imaging, the determined region of the two-dimensional code falls within the storage range. The two-dimensional code reader according to claim 2, wherein the position in the imaging range is controlled.   The two-dimensional code reader according to claim 3, wherein the storage range control unit estimates a central position of the set of code blocks, and controls the estimated central position to be positioned at the center of the storage range.   The storage range control unit controls the estimation of the center position of the set of code blocks so that the center of the block including the estimated center position is positioned at the center of the storage range. Dimensional code reader.   The storage range control unit divides the storage range into a plurality of blocks, determines a block having a high existence probability of the image of the two-dimensional code as a central block, and determines the center of the central block determined in the next imaging. The two-dimensional code reading device according to claim 1, wherein the position of the storage range in the imaging range is controlled so as to be the center of the storage range.   The storage range control unit divides the storage range into grid regions including a plurality of adjacent blocks, and controls the position of the storage range in the imaging range in units of the grid regions. The two-dimensional code reader according to claim 1. Among the image data captured by the 2D imaging device, the image data in the storage range narrower than the imaging range of the 2D imaging device is stored in the memory, the image data in the storage range is analyzed, and the 2D code included in the image is analyzed A two-dimensional code reading method
Search for the area of the two-dimensional code in the storage range,
The analysis of the two-dimensional code in the image data of the storage range, and when the analysis fails, based on the position of the area of the two-dimensional code searched for, the position of the storage range in the imaging range in the next imaging A two-dimensional code reading method characterized by controlling.

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