JP2010092211A - Symbol reading device and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a symbol reading device more suitably reading a symbol. <P>SOLUTION: This symbol reading device includes: a camera 14 imaging the symbol; a display 16 displaying an imaged image by the camera 14; and a CPU 11 displaying a frame on a display 16, setting a range in the frame of the imaged image as a decoding range, reading the symbol from the decoding range, and performing the processing of reducing the range in the frame when an average cell size of the read symbol is larger than a prescribed cell size. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a symbol reader and a program.

  2. Description of the Related Art A symbol reading device that images a symbol such as a two-dimensional barcode and reads information such as a character string included in the symbol is known. The symbol reader captures a symbol with an imaging device such as a camera, and reads the contents of the symbol by analyzing the captured image with a reader such as a decoding engine.

The user of the symbol reader needs to adjust the position and angle of the camera or the camera portion of the symbol reader so that the symbol can be captured within the imaging range of the camera in order to capture the symbol. In order to assist the symbol imaging operation, there is a symbol reading apparatus including a display device that displays a preview of an imaging range by a camera. In addition, a preview area that is wider than the analysis range of the symbol by the decode engine is displayed as a preview, and a frame indicating the range that is the analysis range of the symbol by the decode engine is displayed in the preview display. A symbol reading device that prompts the user to do this is known (for example, Patent Document 1).
JP 2004-287808 A

However, the symbol reading apparatus disclosed in Patent Document 1 may not be able to read symbols favorably.
The frame displayed in the preview display and the range within the frame have a fixed size. On the other hand, the area of the symbol varies from symbol to symbol. The user of the symbol reading apparatus often tries to image the symbol in the full frame. For this reason, for example, when a small symbol is captured with respect to the size of the range in the frame, the camera is brought too close to the symbol to enlarge the symbol to fill the frame, and as a result, the symbol is not focused. In some cases, imaging may be performed. In some cases, a captured image of an out-of-focus symbol is blurred and cannot be read by a decoding engine.

  On the other hand, when the area of the symbol is large with respect to the size of the range in the frame, the user often takes an image from a position far away from the symbol as a result of trying to fit the symbol in the frame. As a result, the captured symbol becomes very small with respect to the area of the symbol, and the captured image of the symbol may be crushed and cannot be read by the decoding engine. Also in this case, the symbol reading by the symbol reading device cannot be suitably performed.

  The subject of this invention is providing the symbol reader which can read a symbol more suitably.

  In order to solve the above-described problem, a symbol reading apparatus according to a first aspect of the present invention includes an imaging unit that images a subject, a display unit that displays an image captured by the imaging unit, and a predetermined range of the captured image as a symbol. A reading unit that is set as a reading region and reads a symbol from within the predetermined range, a frame display unit that displays a frame indicating the predetermined range on the display unit, and a cell width that constitutes the read symbol is a predetermined cell And a first display control means for displaying the frame so as to reduce a range included in the frame when larger than the width.

  According to a second aspect of the present invention, there is provided a symbol reading device that sets an imaging unit that images a subject, a display unit that displays an image captured by the imaging unit, and a predetermined range of the captured image as a symbol reading region. A reading unit that reads a symbol from within a predetermined range; a frame display unit that displays a frame indicating the predetermined range on the display unit; and a cell width that configures the read symbol is smaller than a predetermined cell width. And a second display control means for displaying the frame so as to enlarge the range included therein.

  According to a third aspect of the present invention, there is provided the symbol reading apparatus according to the first or second aspect, wherein the frame in which the cell width of the symbol imaged to be within the frame is equal to or smaller than the predetermined cell width is displayed. The display control means is provided.

  According to a fourth aspect of the present invention, in the symbol reading apparatus according to any one of the first to third aspects, a blur detection unit that detects that a blur has occurred in the captured image, and a blur in the captured image. And a shake notification means for notifying a display indicating that a shake has occurred.

  According to a fifth aspect of the present invention, in the symbol reading apparatus according to any one of the first to fourth aspects, when the ratio of the lengths of two opposite sides of the four sides of the symbol is larger than a predetermined ratio, When it is determined that the imaging by the imaging unit is performed from an oblique direction with respect to the subject, and when it is determined that the imaging by the imaging unit is performed from the oblique direction, An oblique imaging notification means for notifying that imaging from an oblique direction is being performed is provided.

  According to a sixth aspect of the present invention, there is provided a program for controlling a computer to capture an image of a subject by the imaging unit, a display control unit for displaying a captured image by the imaging unit on a display unit, and a predetermined range of the captured image as a symbol. A reading unit that is set as a reading area and reads a symbol from within the predetermined range, a frame display unit that displays a frame indicating the predetermined range on the display unit, and a cell width constituting the read symbol is greater than a predetermined cell width When it is large, it is made to function as a first display control means for displaying the frame so as to reduce the range included in the frame.

  According to a seventh aspect of the present invention, there is provided a program for controlling a computer to capture an image of a subject by the imaging unit, a display control unit for displaying a captured image by the imaging unit on a display unit, and a predetermined range of the captured image as a symbol. A reading unit that is set as a reading area and reads a symbol from within the predetermined range, a frame display unit that displays a frame indicating the predetermined range on the display unit, and a cell width constituting the read symbol is greater than a predetermined cell width When it is small, it is made to function as a 2nd display control means to display the said frame so that the range included in the said frame may be enlarged.

  ADVANTAGE OF THE INVENTION According to this invention, the symbol reader which can read a symbol more suitably can be provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the embodiments. The embodiment of the present invention shows the most preferable mode of the invention, and the application of the invention is not limited to this.

FIG. 1 shows a main configuration of a symbol reading apparatus 1 according to the first embodiment of the present invention.
The symbol reader 1 is a CPU 11 that performs various processes for controlling the operation of the symbol reader 1, a ROM 12 that stores various programs and data, a RAM 13 that stores temporarily generated data, and an image of a subject. A camera 14 that functions as an imaging device, an input device 15 that enables an imaging operation input and other inputs by the camera 14, a display of a captured image by the camera 14, a display of a frame 21 that provides guidance on a range in which the symbol S is accommodated, and others The display device 16 for displaying the various information and the power supply device 17 for supplying power to each part of the symbol reading device 1 are provided.

  The CPU 11 controls the operation of each unit of the symbol reading device 1 by so-called software processing that reads a program and data corresponding to the processing content from the ROM 12 and performs processing. Data temporarily generated in the processing is stored in the RAM 13 and is called up as necessary. Hereinafter, the processing performed by the CPU 11 is based on software processing.

  The ROM 12 stores at least a symbol analysis program 12a, a frame display program 12b, a decode range frame determination program 12c, and decode range data 12d. The operation control of the CPU 11 by these programs and data will be described later.

  The camera 14 includes at least a sensor 14a, a lens 14b, and a control unit 14c. The sensor 14b is an image sensor, for example, a sensor using a CCD, a CMOS, or the like. The sensor 14a images the subject via the lens 14b. The control unit 14c performs operation control related to imaging by the sensor 14a. An image captured by the camera 14 has a plurality of pixels (pixels) aligned vertically and horizontally, and is stored in the RAM 13 as data.

  The input device 15 has at least a trigger key 15a. The trigger key 15a is a switch that allows a user of the symbol reading device 1 to manually switch on / off, and is, for example, a button by a pressing operation. When the trigger key 15a is ON, the control unit 14c operates the sensor 14a to cause the camera 14 to image the subject. At this time, the camera 14 continues imaging in a predetermined second frame while the trigger key 15a is ON.

  The display device 16 displays an image captured by the camera 14, and the display device 16 displays a frame 21 that provides guidance on a range in which the symbol S is stored. Hereinafter, the display of the captured image by the camera 14 is referred to as a preview.

FIG. 2 shows an example of the preview screen.
As shown in FIG. 2, a frame 21 is displayed on the preview screen. In the preview screen shown in FIG. 2, the symbol S included in the subject is within the range surrounded by the frame 21.

  The inside of the frame 21 is a decoding range. The CPU 11 analyzes (decodes) the captured symbol S so as to be within the decoding range, and reads the contents of the symbol S, that is, the character string information included in the symbol S. The CPU 11 analyzes (decodes) the symbol S by reading and processing the symbol analysis program 12a. That is, the decoding range is a symbol reading area, and the symbol analysis program 12a causes the CPU 11 to function as reading means.

  The frame 21 is displayed as a frame indicating the outer peripheral four corners of the decoding range. The display of the frame 21 is displayed on the display device 16 by the CPU 11 reading and processing the frame display program 12b. That is, the frame display program 12b causes the CPU 11 to function as a frame display means.

The display position of the frame 21, that is, the position of the decoding range is determined by the decoding range data 12d. The decode range data 12d is data including the upper left start point coordinates (X1, Y1) and the lower right end point coordinates (X2, Y2) of the preview screen, and the CPU 11 (X1, Y1) based on the start point coordinates and the end point coordinates. ), (X1, Y2), (X2, Y1), and (X2, Y2) are set as decoding ranges. The preview screen is a screen that displays a captured image having a plurality of pixels, and the start point coordinates (X1, Y1) and the end point coordinates (X2, Y2) correspond to the position of a certain pixel in the preview screen. In the screens shown in FIG. 2 and subsequent figures, the width in the horizontal direction is the width in the X direction, and the width in the vertical direction is the width in the Y direction.
Reading of the decoding range data 12d is performed before imaging by the camera 14.

  Next, the analysis of the symbol S by the CPU 11 will be described. The analysis of the symbol S includes symbol detection processing, binarization processing, and decoding processing. In the following, description will be given in order.

First, symbol detection will be described.
FIG. 3 shows a conceptual diagram of symbol detection processing.
In the symbol detection process, the CPU 11 performs edge detection within the symbol reading area. The edge detected by the edge detection has four corners, and each corner is connected by a straight line (rectangular straight line L shown in FIG. 3) and is closed when the inside of the four corners is a closed region. The area is detected as a symbol S.

  When the detection of the symbol S is successful, the binarization process is performed on the detected symbol S. When the detection of the symbol S fails, the captured image is obtained again and the symbol detection process is performed.

  Since edge detection in the symbol detection process is an edge detection method based on an existing technique, details thereof are omitted. Edge detection does not require strict edge detection, and may be set so that an edge can be detected even if the imaged symbol S has some degree of blurring or blurring (for example, below a preset threshold). desirable. Also, it is not necessary to determine whether or not the range surrounded by the edge is a closed region, and it is not necessary to completely close the region. It is desirable to set so that it does not matter.

  Next, the binarization process will be described. The binarization processing includes luminance detection processing, cell size detection processing, average cell size calculation processing, and binarization success / failure determination processing. In the following, description will be given in order.

  In the luminance detection process, the captured symbol S is divided by a predetermined number of continuous pixels (unit pixels), and a bright portion is divided into white cells based on the luminance difference (luminance difference) between unit pixels. This is a process for determining a dark cell as a black cell, a region that cannot be determined as a white cell and a black cell as a gray zone, and obtaining an array pattern of white cells, black cells, and gray zones. The discrimination between the white cell, the black cell, and the gray zone is based on whether the luminance difference is larger than a predetermined threshold value.

FIG. 4 shows an example of the imaged symbol S. FIG. 4A shows a symbol S with no blur or blur, and FIG. 4B shows a symbol S with blur or blur.
FIG. 5 shows an example of the luminance distribution detected by the luminance detection process. FIG. 5A shows the luminance distribution of a part of the symbol S shown in FIG. 4A, and FIG. 5B shows the luminance distribution of a part of the symbol S shown in FIG. 4B.

  When imaging is performed in a state in which the distance between the lens 14b and the symbol S is favorable, a captured image of the symbol S with no or almost no blur or blur is obtained as shown in FIG. In this case, as shown in FIG. 5A, the luminance distribution obtained by the luminance detection process has many portions where the luminance difference appears large, and as a result, there are many portions where white cells and black cells can be determined. That is, the gray zone ratio is reduced.

  On the other hand, when imaging is performed with an inappropriate distance between the lens 14b and the symbol S, a captured image of the symbol S in which blurring or blurring has occurred is obtained as shown in FIG. 4B. In this case, in the luminance distribution obtained by the luminance detection process, as shown in FIG. 5B, the luminance difference does not appear clearly, and the ratio of the gray zone increases.

The cell size detection process is a process for detecting the number of continuous pixels (cell size) of a portion determined as a white cell or a black cell. Each cell size is stored in the RAM 13.
The average cell size calculation process calculates the average of the cell sizes of the white cell and the black cell detected by the cell size detection process. The average cell size is stored in the RAM 13.

The binarization success / failure determination process is a process of determining the success / failure of the binarization process based on whether or not the ratio of the gray zone with respect to the entire range detected as the symbol S is equal to or less than a predetermined ratio. In the present embodiment, it is determined that the binarization is successful when the gray zone ratio is 20% or less, and the binarization failure is determined when it exceeds 20%.
When binarization is successful, decode processing is performed. When binarization fails, as long as the trigger 15a is ON, a captured image is obtained again and the symbol S is analyzed.

Next, the decoding process will be described.
The decoding process is a process of analyzing a white cell and black cell arrangement pattern included in the symbol S based on a predetermined rule and reading a character string.

  If the decoding process is successful, the reading of the symbol S ends. If the decoding process fails, the captured image is obtained again and the symbol S is analyzed as long as the trigger 15a is ON.

  At the time of binarization failure or decoding failure, the CPU 11 performs a decoding frame range determination process before obtaining a captured image again. The decode frame range determination process is a process of changing the display position of the frame 21 so as to reduce the range within the frame 21.

FIG. 6 shows an example of a preview screen before and after the frame 21 is reduced. 6A is before the frame 21 is reduced, and FIG. 6B is after the frame 21 is reduced.
In the case of binarization failure or decoding failure, for example, as shown in FIGS. 4B and 6A, the captured image of the symbol S is often blurred or blurred. For this reason, in the binarization process, the ratio of the gray zone becomes large and binarization fails. Alternatively, even if the binarization is successful, the decoding process is hindered by the gray zone portion included between the white cell and the black cell, and the decoding process fails.

  The blur and blur in the captured image of the symbol S often occur due to an inappropriate distance between the lens 14b and the symbol S. In particular, when the distance between the lens 14b and the symbol S is too close, blurring or blurring is likely to occur. If the distance between the lens 14b and the symbol S is too short, a captured image of the symbol S larger than the captured image of the symbol S when a suitable binarization process and decoding process can be performed is obtained. In other words, when the captured image of the symbol S is blurred or blurred, the captured image of the symbol S is captured larger than necessary. Therefore, when the captured image of the symbol S is captured larger than necessary, the frame 21 is reduced by the decoding frame range determination process, and the symbol S is suitable for the user who wants to capture the symbol S within the frame. Encourage them to take a picture in size.

The decode frame range determination process is performed by the CPU 11 reading and processing the decode range frame determination program 12c. Details of the decoding frame range determination process will be described below.
First, the CPU 11 calls the average cell size. The average cell size is the average cell size calculated in the average cell size calculation process of the binarization process. Next, the CPU 11 determines whether or not the average cell size is larger than a predetermined cell size (for example, 3 pixels). At this time, if the average cell size is larger than 3 pixels, the CPU 11 reduces the pixel size of the width of the frame 21 (frame width). The frame width is reduced in both the X direction and the Y direction.

Specifically, the reduced frame width is calculated by the following formula (1), the frame width is reduced, and the display device 16 displays the frame width again.

(1) ... Current frame width x 3 / average cell size

  The current frame width in the expression (1) is the pixel size between X1 and X2 and the pixel between Y1 and Y2 of the decoding range data when the frame width has not been reduced by the decoding frame range determination process. Based on size. After the frame width reduction by the decoding frame range determination process is performed one or more times, the frame width is based on the previous frame width reduction. The frame width calculated by the expression (1) is stored in the RAM 13.

  The frame width calculated by the expression (1) may be reflected in the decoding range data 12d. In that case, it is necessary to take measures such as making the ROM 12 a rewritable storage device, or providing a separately rewritable storage device in the symbol reading device 1 and storing the decode range data 12d in the rewritable storage device.

  If the average cell size is 3 pixels or less, the process of reducing the frame width is not performed, and the decoding frame range determination process is terminated.

  Note that, when the frame width is reduced, the current frame width in the above-described equation (1) may be the width in the X direction and the Y direction of the range detected as the symbol S in the symbol detection process. In this case, the frame width is equal to the width when the symbol S is imaged to have a predetermined cell size. As a result, the cell size of the symbol S imaged so as to fit within the frame 21 is equal to or less than a predetermined cell size (3 pixels).

Next, processing from the imaging of the symbol S to the result output by the symbol reader 1 will be described with reference to the flowcharts of FIGS.
FIG. 7 is a flowchart showing the operation of the symbol reading apparatus 1.

  When the trigger key 15a is turned on by the user's operation (step S1), the CPU 11 reads the decode range data 12d (step S2). Thereafter, the CPU 11 causes the camera 14 to image the subject (step S3), stores the captured image data in the RAM 13 (step S4), and causes the display device 16 to display the captured image data as a preview (step S5).

The CPU 11 determines the display position of the frame 21 (step S6). The display position of the frame 21 immediately after the activation of the symbol reader 1 is based on the decoding range data read in step S2.
Thereafter, the CPU 11 displays the frame 21 on the preview screen displayed on the display device 16 (step S7). Symbol detection processing is performed on the range within the frame, that is, the decoding range (step S8). If the symbol detection process has failed (step S9: NO), the process returns to step S3. If the symbol detection process is successful (step S9: YES), the CPU 11 performs a binarization process (step S10).

FIG. 8 is a flowchart showing the operation of the binarization process shown in step S10 of FIG.
In the binarization process, the CPU 11 scans the image detected as the symbol S (step S21) and checks the luminance difference between unit pixels (step S22). When the luminance difference is larger than the predetermined threshold (step S23: YES), the CPU 11 determines whether or not the luminance change is brighter from the dark part toward the bright part (step S24). When the change in luminance is brighter from the dark part toward the bright part (step S24: YES), the CPU 11 detects a white cell (step S25). If the change in luminance is not bright from the dark part to the bright part in step S24 (step S24: NO), that is, if the change in luminance is dark from the bright part to the dark part, the CPU 11 Is detected (step S26). After step S25 and step S26, the CPU 11 detects the cell size of the detected white cell or black cell (step S27). In step S23, when the luminance difference is equal to or smaller than a predetermined threshold (step S23: NO), the portion is determined as a gray zone (step S28). The processes in steps S21 to S28 are performed until the scanning of the entire range of the image detected as the symbol S is completed (step S29: NO).

  When scanning of the entire range of the image detected as the symbol S is completed (step S29: YES), the CPU 11 calculates an average cell width (step S30). Thereafter, the CPU 11 determines whether the ratio of the gray zone is 20% or less with respect to the entire range of the image detected as the symbol S (step S31), and if it is 20% or less (step S31: YES), Judge that binarization was successful. When larger than 20% (step S31: NO), it is determined that the binarization has failed. This completes the binarization process.

  If the binarization is successful after the binarization process (step S11: YES), the CPU 11 performs a decoding process (step S12). If the decoding process is successful (step S13: YES), the CPU 11 outputs a result such as displaying the obtained character string on the display device 16 (step S14), and ends the operation.

  If the binarization has failed (step S11: NO) or the decoding process has failed (step S13: NO), the CPU 11 checks whether the trigger key 15a is in the ON state (step S15). When the trigger key 15a is OFF (step S15: NO), the CPU 11 performs a predetermined error process and ends the operation.

  When the trigger key 15a is ON in step S15 (step S15: YES), the CPU 11 performs a decoding range frame determination process (step S16).

FIG. 9 is a flowchart showing the operation of the decoding range frame determination process shown in step S16 of FIG.
In the decoding range frame determination process, the CPU 11 calls the average cell size (step S41). It is determined whether the average cell size is larger than 3 pixels (step S42). When the average cell size is larger than 3 pixels (step S42: YES), the CPU 11 calls the current frame width (step S43), reduces the frame width based on the calculation result of the above-described formula (1) (step S44), The decoding range frame determination process ends.
In step S42, when the average cell size is 3 pixels or less (step S42: NO), the CPU 11 ends the decoding range frame determination process.

  After the decoding range frame determination process in step S16, the process returns to step S3. The processing performed thereafter is the same as described above. However, when the processing for reducing the frame width is performed in the decoding range frame determination processing in step S16, the display position determination processing for the frame 21 in step S6 is performed with the reduced frame width. Based.

  According to the first embodiment, when the average cell size is larger than the predetermined cell size, the frame width is reduced. Therefore, it is possible to prevent imaging at a short distance where the symbol S becomes excessively large. That is, when the symbol S is captured in the frame 21 having a small frame width, it becomes difficult to make the distance between the symbol S and the camera 14 so close that the captured image of the symbol S is blurred or blurred. The user is guided to the appropriate distance between the symbol S and the camera 14. Since the picked-up image of the symbol S picked up at an appropriate distance can be suitably binarized and decoded, a symbol reader capable of reading the symbol S more suitably can be provided.

  Further, when the frame width is reduced, the current frame width in the above-described equation (1) is set as the width in the X direction and the Y direction of the range detected as the symbol S in the symbol detection process. It is equal to the width when the symbol S is imaged so as to have a predetermined cell size. As a result, the cell size of the symbol S imaged so as to fit in the frame 21 is equal to or smaller than the predetermined cell size, and thus a captured image of the symbol S that can be favorably binarized and decoded more reliably is obtained. .

  Next, a symbol reading apparatus 2 according to a second embodiment of the present invention, which is an embodiment different from the first embodiment, will be described. In addition, about the structure similar to 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  FIG. 10 shows a main configuration of the symbol reading apparatus 2 according to the second embodiment of the present invention.

  The ROM 12 stores at least a shake detection program 12e and an oblique imaging determination program 12f in addition to the programs and data stored in the ROM 12 of the first embodiment.

The shake detection program 12e detects a shake that has occurred in the captured image of the symbol S and outputs a display indicating that the shake has occurred to the display device 16.
For example, when the user causes camera shake or the like during imaging by the camera 14, the captured image is a captured image in which camera shake has occurred due to the camera shake. Specifically, when blurring occurs, a captured image in which a plurality of portions having the same or very similar arrangement pattern of white cells, black cells, and gray zones, that is, a luminance difference change pattern, is obtained. The shake detection program 12e detects shake based on such a change pattern of the luminance difference.

FIG. 11 shows an example of a screen including a display indicating that blurring has occurred.
When the shake detection program 12e detects a shake, the shake detection program 12e displays a mark 31 indicating that a shake has occurred in the upper right of the frame 21 displayed on the preview screen.

  The oblique imaging determination program 12f determines that imaging by the camera 14 is performed in an oblique direction with respect to the symbol S when the ratio of the lengths of the two opposite sides of the symbol S is greater than a predetermined ratio. .

For example, when the image recognition unit of the sensor 15a is imaged with respect to a plane including the symbol S, which is the subject, in an oblique state rather than in a parallel or substantially parallel state, two opposite sides of the four sides of the symbol S are Due to the difference between the focal length of one side with respect to the camera 14 and the focal length with respect to the camera 14 on the other side, the lengths of one side and the other side are imaged differently. As a result, the square symbol S is imaged in a trapezoidal shape.
The oblique imaging determination program 12f has a ratio of the lengths of two sides of two opposite sides of the symbol S larger than a predetermined value (for example, the ratio of the length of one side to the length of the other side is more than twice). Large), it is determined that the imaging is performed on the symbol S from an oblique direction. As the lengths of the two sides, the lengths of two opposite sides among the four sides recognized as straight lines connecting the four corners by the edge detection in the above-described symbol detection process are used.

FIG. 12 shows an example of a screen including a display indicating that imaging is being performed from an oblique direction.
When the oblique imaging determination program 12f determines that imaging is being performed from an oblique direction, the oblique imaging determination program 12f displays the frame 21 displayed on the preview screen in a trapezoidal shape as shown in FIG.

  The two sides whose lengths are compared may be the upper and lower sides of the symbol S in the captured image, or the left and right sides. You may compare about upper and lower sides, and right and left, respectively.

  In addition to the functions described in the first embodiment, the symbol analysis program 12a according to the second embodiment provides the CPU 11 with a function for expanding the frame width in the decoding frame range determination process.

FIG. 13 shows an example of a preview screen before and after the frame 21 is enlarged. 13A is before the frame 21 is enlarged, and FIG. 13B is after the frame 21 is enlarged.
If the distance between the lens 14b and the symbol S is too long, as shown in FIG. 13A, the symbol S is smaller than the captured image of the symbol S when a suitable binarization process and decoding process can be performed. The captured image is obtained. The captured image of the symbol S that is captured in a small size may be partially or wholly crushed, blurred, or blurred, and may cause binarization failure or decoding failure. Therefore, when the captured image of the symbol S is captured small, the frame 21 is enlarged by the decoding frame range determination process, and the user is prompted to capture the symbol S in a suitable size.

Specifically, when the calculation result of the average cell size in the binarization process is smaller than a predetermined cell size (for example, 3 pixels) as a reference for the frame width expansion, the same as the expression (1) in the first embodiment The frame width is expanded based on the calculation result of
In the second embodiment, it is possible to reduce the frame width as in the first embodiment in the decoding frame range determination process. In the second embodiment, a predetermined cell size (for example, 3 pixels) as a reference for frame width expansion and a predetermined cell size (for example, 5 pixels) as a reference for frame width reduction are provided separately.

  Note that when the frame width is expanded, the current frame width in the above equation (1) may be the width in the X direction and the Y direction of the range detected as the symbol S in the symbol detection process. In this case, the frame width is equal to the width when the symbol S is imaged to have a predetermined cell size. As a result, the cell size of the symbol S imaged so as to fit within the frame 21 is equal to or less than a predetermined cell size (3 pixels).

Next, processing from the imaging of the symbol S to the result output by the symbol reader 2 will be described with reference to the flowcharts of FIGS.
FIG. 14 is a flowchart showing the operation of the symbol reading device 2. The flowchart shown in FIG. 14 is a flowchart in which step S6 of the flowchart of the symbol reading apparatus 1 shown in FIG. 7 is replaced with step S17, and the other steps are the same as those in FIG. 7 and the above description.

  After the process of step S5, the CPU 11 of the symbol reading device 2 determines the frame display position, the presence or absence of trapezoidal display, and the presence or absence of blur display (step S17). Thereafter, the CPU 11 displays a frame corresponding to the determination content of step S51 (step S7).

FIG. 15 is a flowchart showing the operation of the decoding range frame determination process shown in step S16 of FIG.
The CPU 11 of the symbol reading device 2 detects blurring in the decoding range frame determination process (step S51). When blurring is detected (step S52: YES), processing for additionally displaying the mark 31 indicating that blurring has occurred in the upper right of the frame 21 is performed (step S53), and the decoding range frame determination processing is terminated. If no blur is detected (step S52: NO), the CPU 11 performs an oblique scan detection process (step S54).

FIG. 16 is a flowchart showing the operation of the oblique scan detection process shown in step S54 of FIG.
In the oblique scan detection process, the CPU 11 obtains the lengths of two opposite sides of the four sides of the symbol S (step S71), and the ratio of the length of one side to the length of the other side is greater than twice. (Step S72). When the ratio between the length of one side and the length of the other side is greater than twice (step S72: YES), the CPU 11 determines that imaging is being performed from an oblique direction (oblique scanning). When the ratio between the length of one side and the length of the other side is twice or less (step S72: NO), the CPU 11 determines that the scan is normal.

  If it is determined that the scan is an oblique scan after the oblique scan detection process in step S54 (step S55: YES), the CPU 11 makes the frame 21 trapezoidal (step S56) and ends the decode range frame determination process. If it is determined that the scan is normal scanning (step S55: NO), the CPU 11 calls the average cell size (step S57), and determines whether the average cell size is smaller than 3 pixels (step S58). When the average cell size is smaller than 3 pixels (step S58: YES), the CPU 11 calls the current frame width (step S59), and sets the frame width to the frame width based on the calculation result of the above-described formula (1) (step S60). ). When the average cell size is 3 pixels or more (step S58: NO), the CPU 11 determines whether the average cell size is larger than 5 pixels (step S61). When the average cell size is larger than 5 pixels (step S61: YES), the processing after step S59 is performed. If the average cell size is 5 pixels or less (step S61: NO), the decoding range frame determination process is terminated.

  According to the second embodiment, in addition to the effects of the first embodiment, when the average cell size is smaller than the predetermined cell size, the frame width is enlarged, so that the imaging at a long distance is performed because the symbol S becomes too small. Can be prevented. That is, by enlarging the frame width, it is possible to prompt the user to perform an operation that can obtain a captured image of a larger symbol S, that is, to perform imaging at a short distance. Induced to the distance. Since the picked-up image of the symbol S picked up at an appropriate distance can be suitably binarized and decoded, a symbol reader capable of reading the symbol S more suitably can be provided.

  Furthermore, when the frame width is enlarged, the current frame width is set to the width in the X direction and the Y direction of the range detected as the symbol S in the symbol detection process, so that the frame width becomes the predetermined cell size of the symbol S. It becomes equal to the width when the image is taken. As a result, the cell size of the symbol S imaged so as to fit in the frame 21 is equal to or smaller than the predetermined cell size, and thus a captured image of the symbol S that can be favorably binarized and decoded more reliably is obtained. .

  Further, when a shake is detected in the captured image, a mark 31 indicating that the shake has occurred is displayed on the upper right of the frame 21, so that the cause of the case where a suitable symbol S cannot be captured and read due to the shake is shown to the user. It is possible to notify clearly, and to alert the user to a shake such as a camera shake during imaging.

  Further, when it is determined that imaging is performed from an oblique direction, the shape of the frame 21 is displayed in a trapezoidal shape. Therefore, the cause of the case where imaging and reading of the symbol S suitable for imaging from the oblique direction cannot be performed is used. The user can be clearly notified, and the user can be alerted to the fact that the image is being taken from an oblique direction.

Note that the description in the present embodiment shows an example of the present invention, and the present invention is not limited to this.
For example, the number of pixels, the predetermined cell size, the luminance, the ratio of two sides, and other numerical values shown in the first and second embodiments are examples, and other numerical values may be set.

  The symbol S included in the subject illustrated in each embodiment is a two-dimensional barcode, but other symbols may be used. For example, a one-dimensional barcode may be used.

  The blur display and the oblique scan display may be performed by other methods. For example, an LED or the like for notification may be provided to the symbol reading device, and the LED may be caused to emit light or blink based on blur detection or oblique scan determination, or in different colors depending on the content of the decoding range frame determination process. You may make it light-emit. Also, notification by voice may be used.

  Although blur detection is performed by software processing based on the captured image, dedicated hardware may be used. Similarly, among the functions of the symbol reading apparatus, each configuration performed by software processing may be provided with a dedicated configuration for each function.

1 shows a main configuration of a symbol reading apparatus according to a first embodiment of the present invention. An example of a preview screen is shown. A conceptual diagram of symbol detection processing is shown. An example of the imaged symbol is shown. FIG. 4A shows a symbol with no blur or blur, and FIG. 4B shows a symbol with blur or blur. An example of the luminance distribution detected by the luminance detection process is shown. FIG. 5A shows the luminance distribution of a part of the symbol shown in FIG. 4A, and FIG. 5B shows the luminance distribution of a part of the symbol shown in FIG. 4B. An example of a preview screen before and after frame reduction is shown. FIG. 6A is before the frame is reduced, and FIG. 6B is after the frame is reduced. It is a flowchart which shows operation | movement of a symbol reader. It is a flowchart which shows the operation | movement of the binarization process shown to step S10 of FIG. It is a flowchart which shows the operation | movement of the decoding range frame determination process shown to FIG.7 S16. The main structure of the symbol reader by the 2nd Embodiment of this invention is shown. An example of the screen containing the display which shows that the blurring has arisen is shown. An example of the screen containing the display which shows that the imaging is performed from the diagonal direction is shown. An example of a preview screen before and after enlarging a frame is shown. FIG. 13A is before the frame is enlarged, and FIG. 13B is after the frame is enlarged. 4 is a flowchart showing an operation of the symbol reading device 2. It is a flowchart which shows the operation | movement of the decoding range frame determination process shown to step S16 of FIG. 16 is a flowchart showing an operation of an oblique scan detection process shown in step S54 of FIG.

Explanation of symbols

11 CPU
12 ROM
13 RAM
14 Camera 15 Input Device 16 Display Device 21 Frame S Symbol

Claims (7)

Imaging means for imaging a subject;
Display means for displaying an image captured by the imaging means;
A reading unit that sets a predetermined range of the captured image as a symbol reading region and reads a symbol from the predetermined range;
Frame display means for displaying a frame indicating the predetermined range on the display means;
First display control means for displaying the frame so as to reduce a range included in the frame when a cell width constituting the read symbol is larger than a predetermined cell width;
A symbol reading apparatus comprising: Imaging means for imaging a subject;
Display means for displaying an image captured by the imaging means;
A reading unit that sets a predetermined range of the captured image as a symbol reading region and reads a symbol from the predetermined range;
Frame display means for displaying a frame indicating the predetermined range on the display means;
A second display control means for displaying the frame so as to enlarge a range included in the frame when a cell width constituting the read symbol is smaller than a predetermined cell width;
A symbol reading apparatus comprising:   3. The symbol reading according to claim 1, further comprising: a third display control unit configured to display the frame in which a cell width of a symbol imaged so as to be within the frame is equal to or less than the predetermined cell width. apparatus. A shake detection means for detecting the occurrence of shake in the captured image;
A blur notification means for notifying a display indicating that a blur has occurred when the captured image has a blur;
4. The symbol reading apparatus according to claim 1, further comprising: An oblique imaging determination unit that determines that imaging by the imaging unit is performed in an oblique direction with respect to the subject when a ratio of lengths of two opposite sides of the four sides of the symbol is greater than a predetermined ratio;
An oblique imaging notification means for notifying that imaging from an oblique direction is performed when it is determined that imaging by the imaging means is performed from an oblique direction with respect to the subject. Item 5. The symbol reading device according to any one of Items 1 to 4. Computer
Imaging control means for controlling imaging of a subject by the imaging means;
Display control means for displaying an image captured by the imaging means on a display means;
A reading unit that sets a predetermined range of the captured image as a symbol reading region and reads a symbol from the predetermined range;
Frame display means for displaying a frame indicating the predetermined range on the display means;
First display control means for displaying the frame so as to reduce a range included in the frame when a cell width constituting the read symbol is larger than a predetermined cell width;
Program to function as. Computer
Imaging control means for controlling imaging of a subject by the imaging means;
Display control means for displaying an image captured by the imaging means on a display means;
A reading unit that sets a predetermined range of the captured image as a symbol reading region and reads a symbol from the predetermined range;
Frame display means for displaying a frame indicating the predetermined range on the display means;
A second display control means for displaying the frame so as to enlarge a range included in the frame when a cell width constituting the read symbol is smaller than a predetermined cell width;
Program to function as.

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