JP2012194853A - Optical information reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical information reader capable of suitably correcting deviation of a two-dimensional code imaged using a rolling shutter system.SOLUTION: One side to be taken in first among four sides constituting an outer edge of an outer shape of a detected code area is determined as a reference side Lo. The code area is corrected by predicting an area occupying the code area as to a cell area adjoining a cell area of a row adjoining the upper reference side Lo based upon the cell area and then estimating which of a black cell and a white cell the cell area corresponds to from the predicted area, and then estimating an area occupying the code area based upon a cell area adjoining a cell area of another row from the side of the reference side and then estimating which of a black cell and a white cell the cell area corresponds to from the predicted area in order from a cell area of a row close to the reference side Lo.

Description

  The present invention relates to an optical information reading apparatus that decodes a two-dimensional code imaged using a rolling shutter system.

  2. Description of the Related Art Conventionally, a CMOS sensor (CMOS image sensor) employing a rolling shutter system is known as means for imaging an information code such as a two-dimensional code that is a reading target in an optical information reader. As a feature of this CMOS sensor, it is possible to randomly access pixel signals, and it is easy to reduce the pixel pitch with high speed and low power consumption compared with other imaging means (light receiving means) such as a CCD sensor. In addition to being advantageous for downsizing and increasing the number of pixels, there is a merit of low price.

  As a technique related to an optical information reading apparatus that decodes an information code picked up using a light receiving means (imaging means) employing a rolling shutter system such as a CMOS sensor, an imaging apparatus shown in Patent Document 1 below is known. It has been. This imaging apparatus is a distance between a moving subject obtained from a motion detection unit and an arbitrarily fixed reference row for correcting image distortion in a captured image captured by a CMOS sensor employing a rolling shutter system. Then, by controlling the horizontal position of the moving subject for each row by the amount of motion vector obtained from the motion detection means, the image distortion due to the different exposure time for each row is corrected.

Japanese Patent Application No. 2009-141717

  By the way, in the reading apparatus configured as disclosed in Patent Document 1, in order to correct image shift (image distortion), since images of several past frames are always stored, image data is stored. There is a problem that not only the necessary storage capacity is increased, but also the processing time is increased because the vector amount is calculated over the above several frames. In particular, these problems become more pronounced as the resolution of the captured image increases. In addition, since the relative speed change between the reading device and the information code to be read is not taken into account, there is a problem that the accuracy of correction is lowered when the reading device and the information code do not move relatively at a constant speed. is there.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain a two-dimensional code captured using a rolling shutter system without considering a plurality of past image information. An object of the present invention is to provide an optical information reading apparatus capable of suitably correcting a deviation.

  In order to achieve the above object, in the optical information reading device according to claim 1, a rectangular two-dimensional code formed by two-dimensionally arranging a plurality of rectangular dark cells and light cells. An optical information reading apparatus for optically reading light received from a light receiving means configured to two-dimensionally arrange light receiving elements capable of receiving reflected light from the two-dimensional code, and output from the light receiving means Corresponding to the two-dimensional code among the image information, a fetching means for fetching image information by a rolling shutter system, a decoding means capable of decoding the two-dimensional code included in the image information fetched by the fetching means The outer shape of the code area is detected for a code area that is composed of a plurality of cell areas corresponding to either the dark cell or the light cell. Out of the four sides constituting the outer edge of the outer shape detected by the detecting means and the detecting means, when the one side that is first taken in by the taking-in means is used as the reference side, the cell region in the row adjacent to the reference side For the cell area adjacent to this cell area from the side opposite to the reference side, the area occupied in the code area is predicted, and the cell area is determined as either the dark cell or the light cell from the predicted area. And predicting the area occupied by the code area with reference to the adjacent cell area from the reference side for the cell area of the other row, and the cell area is darkened from the predicted area. An area correction unit that corrects the code area by estimating in order from a cell area in a row close to the reference side, which corresponds to a cell or a light-colored cell; Decoding means includes a two-dimensional code included in the image information, wherein the decoding for any of the two-dimensional code which the code region has been corrected by said area correcting means.

  According to a second aspect of the present invention, in the optical information reading device according to the first aspect, when the length of the cell region in the column direction orthogonal to the reference side is a column direction length, the row adjacent to the reference side Cell length correcting means for correcting the column direction length of the cell area of another row so as to be equal to the column direction length of the cell area, and the decoding means is included in the image information. One of the dimension code and the two-dimensional code in which the length in the column direction is corrected by the cell length correcting unit and the code area is corrected by the area correcting unit is decoded.

  According to a third aspect of the present invention, in the optical information reading apparatus according to the first or second aspect, the area correction unit is configured to select a cell area to be corrected from lines passing through the four corners of the adjacent cell area from the reference side. A region that the cell region occupies in the code region is predicted based on a region surrounded by two lines along the column direction orthogonal to the reference side, and the cell region is darkened from the predicted region. It is estimated and correct | amended whether it corresponds to a cell and the said bright color cell.

  According to a fourth aspect of the present invention, in the optical information reading apparatus according to any one of the first to third aspects, the ratio of the area corresponding to the dark cell to the predicted area and the light cell When the difference from the ratio occupied by the corresponding area is smaller than a predetermined threshold, the correction for the code area including the cell area is invalidated.

  According to a fifth aspect of the present invention, in the optical information reading device according to any one of the first to fourth aspects, the light receiving means is a CMOS sensor.

  In the first aspect of the invention, of the four sides constituting the outer edge of the outer shape of the code area detected by the detecting means, one side that is first taken into the taking means is set as the reference side. Then, the area correction means predicts the area occupied in the code area with respect to the cell area adjacent to the cell area from the side opposite to the reference side with reference to the cell area of the row adjacent to the reference side. From this, it is estimated whether the cell area corresponds to a dark cell or a light cell, and for the cell areas of other rows, the area occupied by the code area is predicted based on the adjacent cell area from the reference side. From the predicted area, the code area is corrected by estimating in order from the cell area in the row close to the reference side whether the cell area corresponds to a dark cell or a light cell. Then, either the two-dimensional code included in the image information or the two-dimensional code whose code area has been corrected by the area correction unit is decoded by the decoding unit.

When the rolling shutter method is adopted, the difference between the light reception timing and the image information captured later with respect to the image information captured earlier by the capturing unit is that the cell region in the row farther from the reference side. As a result, the influence of image shift increases.
In the present invention, the cell area to be corrected is estimated and corrected based on the area occupied in the code area predicted with reference to the adjacent cell area from the reference side, so that the relative relationship between the apparatus and the two-dimensional code is corrected. Since the change in speed is taken into account, the shift amount is corrected so as to approach the cell region on the reference side, so that the influence of the shift can be reduced even in a cell region in a row away from the reference side.
Therefore, it is possible to suitably correct the deviation of the two-dimensional code imaged using the rolling shutter method without considering a plurality of past image information.

  In the invention of claim 2, the cell length correction means corrects the column direction lengths of the cell regions of other rows so as to be equal to the column direction length of the cell region of the row adjacent to the reference side. Then, either the two-dimensional code included in the image information or the two-dimensional code whose length in the column direction is corrected by the cell length correcting unit and whose code area is corrected by the region correcting unit is decoded by the decoding unit. Made.

  As a result, each cell area constituting the code area is corrected by the area correction unit after the cell length correction unit corrects all the cell lengths to be equal, so that the shape of the cell area is the original cell. Since it becomes closer to the shape, the probability of successful decoding can be improved.

  According to a third aspect of the present invention, an area surrounded by two lines along the column direction among the lines passing through the four corners of the adjacent cell area from the reference side is selected by the area correction unit. As a reference, an area occupied by the cell area in the code area is predicted, and the cell area corresponding to the dark cell or the light cell is estimated and corrected from the predicted area.

  Of the lines passing through the four corners of the cell area adjacent from the reference side, the area surrounded by the two lines along the column direction is an area in which the shift amount of the cell area adjacent from the reference side is more reflected. Therefore, the shift amount is corrected so as to approach the cell region on the reference side side, and the influence of the shift can be reliably reduced.

  In the invention of claim 4, the predicted area is estimated when the difference between the ratio of the area corresponding to the dark cell and the ratio of the area corresponding to the light cell is smaller than a predetermined threshold, that is, the predicted area. If it is difficult to determine whether the corresponding area corresponds to a dark cell or a light cell, correction for the code area including the cell area is invalidated.

  If the above correction is performed until it is difficult to determine whether the predicted area corresponds to a dark cell or a light cell, there is a high possibility that decoding will fail due to incorrect correction. Therefore, in such a case, by making the correction invalid, it is possible to eliminate a decoding failure due to an erroneous correction.

  In the invention of claim 5, since the light receiving means is a CMOS sensor, compared with other light receiving means such as a CCD sensor, the pixel pitch can be easily reduced with high speed reading and low power consumption. Not only is it superior in terms of pixelization, but it also has the advantage of low price.

1 is a block diagram illustrating an electrical configuration of an optical information reading device according to a first embodiment. It is explanatory drawing which illustrates the light-receiving surface of the light receiving sensor comprised by arranging a some light receiving element in the two-dimensional form of m row n column. It is explanatory drawing for demonstrating the shift | offset | difference of the captured image imaged with the rolling shutter system. It is a flowchart which illustrates the flow of the reading process implemented in a control circuit. FIG. 5 is an explanatory diagram for explaining correction of a column direction length in the cell length correction process of FIG. 4. FIG. 5 is an explanatory diagram for explaining cell area correction in the area correction processing of FIG. 4; It is a flowchart which illustrates the flow of the reading process implemented in the control circuit of the 1st modification concerning this embodiment.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of an optical information reading device according to the invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an electrical configuration of an optical information reading apparatus 10 according to the present embodiment. FIG. 2 is an explanatory diagram illustrating a light receiving surface 28a of a light receiving sensor 28 configured by arranging a plurality of light receiving elements in a two-dimensional array of m rows and n columns.

  As shown in FIG. 1, an optical information reader 10 optically reads an information code attached to an article, for example, a one-dimensional code such as a bar code or a two-dimensional code such as a QR code (registered trademark). It is configured as. The optical information reading apparatus 10 is configured such that a circuit unit 20 is accommodated in an outer case 11, and the circuit unit 20 mainly includes an illumination light source 21, a light receiving sensor 28, an imaging lens 27, and the like. And a microcomputer (hereinafter referred to as “microcomputer”) system such as a memory 35, a control circuit 40, and a trigger switch 42.

  The optical system is divided into a light projecting optical system and a light receiving optical system. The illumination light source 21 constituting the light projecting optical system functions as an illumination light source capable of emitting the illumination light Lf, and includes, for example, a red LED and a lens provided on the emission side of the LED. In addition, in FIG. 1, the example which irradiates the illumination light Lf toward the target object R to which the information code Q was attached | subjected is shown notionally.

  The light receiving optical system includes a light receiving sensor 28, an imaging lens 27, a reflecting mirror (not shown), and the like. The light receiving sensor 28 is configured to receive the reflected light Lr irradiated and reflected by the information code Q and the like. In this embodiment, as shown in FIG. 2, the light receiving surface 28a includes a plurality of light receiving elements. A CMOS sensor (CMOS image sensor) configured in a two-dimensional array of m rows and n columns corresponds to this. The light receiving sensor 28 is mounted on a printed wiring board (not shown) so as to be able to receive incident light incident through the imaging lens 27. The light receiving sensor 28 may correspond to “light receiving means” recited in the claims.

  The imaging lens 27 functions as an imaging optical system capable of condensing incident light incident from the outside through the reading port 13 and forming an image on the light receiving surface 28a of the light receiving sensor 28. In the present embodiment, after the illumination light Lf emitted from the illumination light source 21 is reflected by the information code Q, the reflected light Lr is collected by the imaging lens 27 and a code image is formed on the light receiving surface 28 a of the light receiving sensor 28. The image is formed.

  The microcomputer system includes an amplification circuit 31, an A / D conversion circuit 33, a memory 35, an address generation circuit 36, a synchronization signal generation circuit 38, a control circuit 40, a trigger switch 42, a light emitting unit 43, a buzzer 44, a vibrator 45, and a liquid crystal display. 46, a communication interface 48, and the like.

  The image signal (analog signal) output from the light receiving sensor 28 of the optical system is amplified by a predetermined gain by being input to the amplifier circuit 31, and then input from the analog signal when input to the A / D conversion circuit 33. Converted into a digital signal. When the digitized image signal, that is, image data (image information) is generated and input to the memory 35, it is stored in a predetermined code image information storage area. The synchronization signal generation circuit 38 is configured to generate a synchronization signal for the light receiving sensor 28 and the address generation circuit 36, and the address generation circuit 36 is based on the synchronization signal supplied from the synchronization signal generation circuit 38. Thus, the storage address of the image data stored in the memory 35 can be generated.

  In particular, in the present embodiment, since a CMOS sensor is employed as the light receiving sensor 28, the light receiving surface 28a is not a method (global shutter method) in which all pixels (m rows and n columns) are exposed at once and taken in all. This is a system (rolling shutter system) in which one row of the two-dimensional array constituting the above is sequentially exposed from the top and sequentially fetched for each row. For this reason, in the code image information storage area of the memory 35, the first row 1st column to m column → the second row 1st column to m column → the third row of the two-dimensional array constituting the light receiving surface 28a. Each of the image data is accumulated in the order of 1st column to mth column →... → (n-1) th row 1st column to mth column → nth row 1st column to mth column (see FIG. 2).

  The memory 35 is a semiconductor memory device, and corresponds to, for example, a RAM (DRAM, SRAM, etc.) or a ROM (EPROM, EEPROM, etc.). In addition to the above-described code image information storage area, the RAM of the memory 35 is configured to be able to secure a work area and a reading condition table used by the control circuit 40 in each processing such as arithmetic operation and logical operation. Yes. The ROM stores in advance a predetermined program that can execute a reading process and the like that will be described later, and a system program that can control each hardware such as the illumination light source 21 and the light receiving sensor 28.

  The control circuit 40 is configured by a microcomputer capable of controlling the entire optical information reading apparatus 10, has a CPU, a system bus, an input / output interface, and the like, and has an information processing function. Is configured. In the present embodiment, a trigger switch 42, a light emitting unit 43, a buzzer 44, a vibrator 45, a liquid crystal display 46, a communication interface 48, and the like are connected to the control circuit 40.

  As a result, the control circuit 40 can, for example, turn on / off the light emitting unit 43 that functions as an indicator for notifying information on monitoring and management of the trigger switch 42 and reading of the information code Q, and a buzzer that can generate a beep sound and an alarm sound. Communication that enables ON / OFF of ringing 44, drive control of the vibrator 45 capable of generating vibration that can be transmitted to the user of the optical information reader 10, display control of the liquid crystal display 46, and serial communication with an external device Communication control of the interface 48 is enabled.

  By configuring the optical information reader 10 in this way, for example, when the power switch is turned on and a predetermined self-diagnosis process or the like is normally completed and the information code Q can be read, the illumination light Lf The input of the trigger switch 42 instructing light emission is received. As a result, when the operator presses the trigger switch 42 to turn it on, the control circuit 40 outputs a light emission signal to the illumination light source 21 based on the synchronization signal. Is emitted to emit illumination light Lf.

  When the illumination light Lf is irradiated on the information code Q and the reflected light Lr enters the imaging lens 27 through the reading port 13, the information code is applied to the light receiving surface 28 a of the light receiving sensor 28 by the imaging lens 27. An image of Q, that is, a code image is formed, and each image can be exposed to each light receiving element of the light receiving sensor 28. Then, each light receiving element constituting the light receiving surface 28a is exposed, and a signal corresponding to the amount of light received from each light receiving element is sequentially taken into the code image information storage area of the memory 35 by the rolling shutter method, and as described above. Characters encoded as information code Q by binarizing image data in an area corresponding to information code Q (hereinafter referred to as code area) composed of the captured signal, and then performing a predetermined decoding process Data etc. will be deciphered. The decrypted contents can be displayed on the liquid crystal display 46 or output to a host computer or the like (not shown) via the communication interface 48. The control circuit 40 corresponds to an example of “decoding means” recited in the claims.

FIG. 3 is an explanatory diagram for explaining a shift of a captured image captured by the rolling shutter method. FIG. 3A illustrates a captured image in the case of relative movement in the row direction, and FIG. ) Shows a captured image in the case of relative movement in the column direction, and FIG. 3C shows a captured image in the case of relative movement in the row direction and the column direction.
By the way, for example, in order to read a plurality of information codes Q displayed on the object R, the operator performs a flow reading that images each information code Q while moving the reading port 13 with respect to the object R. There is a case. In this case, since the apparatus main body and the information code Q are relatively moved, the image data taken into the code image information storage area is likely to be shifted, and the decoding process for the information code Q may fail. Get higher.

  In particular, when a square two-dimensional code in which a plurality of square black cells and white cells are arranged two-dimensionally, such as a QR code, is scanned and imaged, for example, in the row direction with respect to the QR code When the image is scanned and scanned in the horizontal direction (FIG. 3), the first row and the second row are taken in the code image information storage area in order, so that as shown in FIG. The image is picked up with a different amount of shift. On the other hand, when the QR code is scanned and scanned in the column direction (vertical direction in FIG. 3), the cell length in the column direction is different in each row as illustrated in FIG. 3B. An image is taken. In addition, in the case of scanning and imaging so that the arrangement direction of each cell in the QR code and the row direction and the column direction of the image data including the QR code are different, the row direction is exemplified as shown in FIG. In addition, the images are shifted in the column direction.

  Therefore, in the optical information reading apparatus 10 according to the present embodiment, an image is picked up in a state where the two-dimensional code is scanned by an operator and the apparatus main body and the two-dimensional code are relatively moved by a reading process described below. In the case of (light reception), it is possible to correct the deviation of the two-dimensional code.

  Hereinafter, the reading process executed by the control circuit 40 of the optical information reading apparatus 10 will be described with reference to FIG. FIG. 4 is a flowchart illustrating the flow of reading processing performed in the control circuit 40.

  When the optical information reader 10 is in a power-on state and is in a reading state in which an information code can be read, first, in step S101, an imaging process is performed, and from the illumination light source 21 according to the operation of the trigger switch 42 by the operator. The illumination light Lf is irradiated toward the object R on which the QR code Q is displayed. As shown in FIG. 1, the reflected light Lr reflected by the object R is received by the light receiving surface 28a of the light receiving sensor 28, and a signal corresponding to the amount of light received from each light receiving element is stored in a rolling shutter system. The code information is stored in the code image information storage area 35 as image information. Note that the control circuit 40 that executes step S101 may correspond to an example of the “capture unit” recited in the claims.

  Next, in step S103, an outer shape detection process is performed. In this process, the code area corresponding to the QR code Q is extracted from the image information captured in the code image information storage area of the memory 35, so that the outer shape of the code area is detected. Note that the code area is configured such that a plurality of cell areas corresponding to either black cells or white cells are adjacent to each other. Note that the control circuit 40 that executes step S103 may correspond to an example of the “detection unit” recited in the claims.

  Subsequently, in step S105, it is determined whether or not the detected outer shape is a square shape. Here, if the outer shape detected in step S103 is a square shape, it is determined that there is no deviation in the captured QR code Q and it is determined Yes in step S105, and each correction process described below is performed. Without decoding, the decoding process is performed in step S117. In this decoding process, the signal in the code area is binarized to specify whether each cell area corresponds to a black cell or a white cell, and is encoded as a QR code Q by a known decoding method. Character data etc. are decoded. Note that the control circuit 40 that executes step S117 may correspond to an example of a “decoding unit” recited in the claims.

  On the other hand, when the outer shape detected in step S103 is not square (No in S105), a reference edge setting process is performed in step S107. In this process, among the four sides constituting the outer edge of the outer shape detected in step S103, one side that is first taken into the code image information storage area of the memory 35 is set as the reference side Lo (see FIG. 3 and the like). .

  Subsequently, in step S109, it is determined whether or not the lengths of the cell regions in the column direction orthogonal to the reference side Lo (hereinafter referred to as column direction length Y) are equal in each row. Here, as illustrated in FIG. 5A, when the column direction length Y is different in each row, it is determined No in step S109.

  In step S111, a length correction process in the column direction is performed. In this process, the column direction length Y of the cell region in another row is corrected based on the column direction length of the cell region adjacent to the reference side Lo.

  This correction will be specifically described with reference to FIG. FIG. 5 is an explanatory diagram for specifically explaining the correction of the column direction length Y in the cell length correction processing of FIG. 4, and FIG. 5 (A) is a partial cell area in the code area before correction. FIG. 5B shows the column direction length Y of a part of the cell regions in the corrected code region.

  As illustrated in FIG. 5A, the column direction length (Y1 in FIG. 5) of the cell region adjacent to the reference side Lo and the column direction lengths of cell regions in other rows (Y2 to Y4 in FIG. 5). ) Is different, it is determined No in step S109. Then, by the correction process in step S111, as illustrated in FIG. 5B, the column direction lengths Y2 to Y4 of the cell regions in other rows are the column direction lengths of the cell regions adjacent to the reference side Lo. Is corrected to be equal to Y1. Note that the control circuit 40 that executes step S111 may correspond to an example of the “cell length correction unit” recited in the claims.

  Next, in step S113, of the four sides constituting the outer edge of the outer shape detected in step S103, sides connected to both ends of the reference side Lo (hereinafter referred to as side sides L1 and L2) are linear or not. Is determined. This is because when the relative speed between the apparatus main body and the QR code Q is changing, the shift amount in each row is non-uniform, and the side sides L1 and L2 are not linear. For this reason, when the side sides L1 and L2 are not linear (No in S113), it is assumed that a relative speed change has occurred between the apparatus main body and the QR code Q. A region correction process is performed in order to suppress the influence of the speed change and to equalize the shift amount in each row.

  In this correction processing, with respect to the cell area of the row adjacent to the reference side Lo, the cell area adjacent to the cell area from the side opposite to the reference side is predicted to occupy the area occupied by the code area, and the predicted area Estimate whether the cell area corresponds to a black cell or a white cell, and predict the area occupied by the code area with respect to the cell area of the other row from the reference side, with reference to the adjacent cell area. The code region is corrected by estimating in order from the cell region in the row close to the reference side Lo whether the cell region corresponds to the black cell or the white cell from the region thus formed.

  The correction process will be specifically described with reference to FIG. FIG. 6 is an explanatory diagram for explaining cell area correction in the area correction processing of FIG. 4, and FIG. 6A shows partial cell areas adjacent to each other in the column direction in the code area before correction. 6B shows correction for the cell region in the second row in FIG. 6A, and FIG. 6C shows correction for the cell region in the third row in FIG. 6A.

  When both sides L1 and L2 of the code area are not linear, one cell area adjacent to the reference side Lo (reference P1 in FIG. 6) and a part of the cell area in the same column as this cell area (reference numeral in FIG. 6) When P2 to P4) are extracted, as illustrated in FIG. 6A, at least a part of the sides along the column direction in the cell regions P1 to P4 have different shapes. In FIG. 6, for convenience, the sides along the column direction in the cell regions P1 to P4 are linearly illustrated, but each side may be formed to have a curved portion.

Hereinafter, the correction process will be described using the cell regions P1 to P4.
In the correction process, first, based on the cell region P1 in the row adjacent to the reference side Lo, a region occupied in the code region is predicted for the cell region P2 adjacent to the cell region from the side opposite to the reference side. Specifically, of the four corners of the kth cell region, when the corners on the reference side are denoted by Cka and Ckb, and the corners on the opposite reference side are denoted by Ckc and Ckd, the four corners of the cell region P1 Assuming two lines passing through the corners C1a to C1d along the column direction, that is, a straight line L1a passing through the corners C1a and C1c and a straight line L1b passing through the corners C1b and C1d, the two straight lines L1a, Points where L1b intersects with straight lines passing through the corners C2c and C2d of the cell region P2 are defined as C2e and C2f (see FIG. 6B).

  Here, an area surrounded by C2a, C2b, C2e, and C2f (hereinafter referred to as a prediction area) is a cell area when the relative speed change between the apparatus main body and the QR code Q when the cell area P1 is imaged becomes equal. Corresponds to P2. For this reason, the ratio of the area corresponding to the black cell and the ratio of the area corresponding to the white cell are obtained for the prediction area based on the prediction area, and the black area as illustrated in FIG. 6B is obtained. When the ratio of the area occupied by the area corresponding to the cell is larger than the ratio of the area occupied by the area corresponding to the white cell, it is estimated that the cell area P2 is an area corresponding to the black cell.

  Next, based on the cell region P2, a region occupied in the code region is predicted for the cell region P3 adjacent to the cell region from the side opposite to the reference side. Specifically, of the lines passing through the four corners C2a to C2d of the cell region P2, two lines along the column direction, that is, a straight line L2a passing through the corners C2a and C2c and a straight line passing through the corners C2b and C2d. Assume L2b, and let C3e and C3f be points where these straight lines L2a and L2b intersect with straight lines passing through the corners C3c and C3d of the cell region P3 (see FIG. 6C). Then, with reference to the prediction area surrounded by C3a, C3b, C3e, and C3f, the ratio of the area corresponding to the black cell and the ratio of the area corresponding to the white cell are obtained for the prediction area. In the case where the ratio of the area occupied by the area corresponding to the white cell is larger than the ratio of the area occupied by the area corresponding to the black cell, the cell area P3 is an area corresponding to the white cell. Presumed.

  Subsequently, the cell area P4 is similarly estimated based on the cell area P3, and the area occupied in the code area is predicted with respect to the cell areas of other rows from the reference side side with reference to the adjacent cell areas. From the predicted area, it is estimated in order from the cell area of the row close to the reference side Lo whether the cell area corresponds to a black cell or a white cell. Then, by performing such estimation for each column, each cell region is estimated, and a code region composed of these cell regions is corrected. Note that the control circuit 40 that executes step S115 may correspond to an example of the “region correction unit” recited in the claims.

  In this way, the code area in which each cell area is estimated in step S115 is decoded in step S117, and character data encoded as QR code Q is decoded. If the column-direction lengths Y are equal in each row, it is determined Yes in step S109, and the processes in and after step S113 are performed without performing the correction process in step S111. Further, when the both sides L1 and L2 of the outer shape detected in step S103 are linear, it is determined Yes in step S113, and after step S117 without performing the correction process in step S115. Is processed.

  As described above, in the optical information reading apparatus 10 according to the present embodiment, one of the four sides constituting the outer edge of the detected outer shape of the code area is set as the reference side Lo. Then, based on the cell area of the row adjacent to the reference side Lo, the cell area adjacent to the cell area from the side opposite to the reference side is predicted to occupy the code area, and the cell area is determined from the predicted area. This is estimated by estimating whether the cell corresponds to a black cell or a white cell, and for the cell region of the other row, the region occupied by the code region is predicted from the reference side from the adjacent cell region The code area is corrected by estimating in order from the cell area in the row close to the reference side Lo whether the cell area corresponds to a black cell or a white cell from the area. Then, either the QR code Q included in the image information or the QR code Q whose code area is corrected as described above is decoded.

In the present invention, since the correction target cell area is estimated and corrected based on the area occupied in the code area predicted with reference to the adjacent cell area from the reference side, the relative relationship between the apparatus main body and the QR code Q is corrected. Therefore, the shift amount is corrected so as to approach the cell region on the reference side, so that the influence of the shift can be reduced even in a cell region in a row far from the reference side Lo. .
Therefore, it is possible to suitably correct the shift of the QR code Q (two-dimensional code) imaged using the rolling shutter method without considering a plurality of past image information.

  Further, the column direction lengths (Y2) of the cell regions in the other rows are corrected so as to be equal to the column direction length (Y1) of the cell region in the row adjacent to the reference side Lo. Then, decoding is performed on either the QR code Q included in the image information or the QR code Q whose length Y in the column direction is corrected in step S111 and whose code area is corrected in step S115.

  As a result, each cell area constituting the code area is corrected in step S115 after all the column direction lengths Y are corrected in step S111, so that the shape of the cell area is the original cell. Since it becomes closer to the shape, the probability of successful decoding can be improved. Furthermore, the prediction accuracy of the predicted region is improved, and the correction accuracy of the shift of the QR code Q (two-dimensional code) in step S115 can be improved.

  In particular, in step S115, for the cell area to be corrected, an area surrounded by using two lines (L1a, L1b, etc.) along the column direction out of lines passing through the four corners of the adjacent cell area from the reference side is used as a reference. In addition, the area occupied by the cell area in the code area is predicted, and from the predicted area, the cell area corresponds to a black cell or a white cell and is corrected.

  Of the lines passing through the four corners of the cell area adjacent from the reference side, the area surrounded by the two lines along the column direction is an area in which the shift amount of the cell area adjacent from the reference side is more reflected. Therefore, the shift amount is corrected so as to approach the cell region on the reference side side, and the shift amount is made uniform, so that the influence of the shift can be reliably reduced.

  In addition, since a CMOS sensor is employed as the light receiving sensor 28, compared with other light receiving sensors (light receiving means), for example, a CCD sensor, the pixel pitch can be easily reduced with high speed reading and low power consumption. In addition to being superior to increasing the number of pixels, it is possible to achieve the advantage of low price.

FIG. 7 is a flowchart illustrating the flow of the reading process performed in the control circuit 40 of the first modification example according to this embodiment.
As a first modification according to the present embodiment, when the decoding process fails, the processes after step S103 may be performed.

  Specifically, as shown in the flowchart of FIG. 7, the code area of the image information captured in the code image information storage area of the memory 35 after the image capturing process in step S <b> 101 is performed in step S <b> 119. Then, when the same decoding process as in step S117 is performed and this decoding process fails (No in S121), the process from step S103 can be performed. In this case, the determination process in step S105 described above is abolished.

  As a result, only when the decoding process fails, the correction process in step S111 or step S115 is performed, so that the load related to the reading process of the control circuit 40 can be reduced and the processing time can be shortened.

  When there is a low possibility that the apparatus main body and the two-dimensional code are relatively moved in the column direction, correction is performed in the reading process shown in the flowchart of FIG. 4 or the reading process shown in the flowchart of FIG. Regarding the processing, the processing in steps S109 and S111 may be omitted, and only the processing in steps S113 and S115 may be performed. Further, in the reading process shown in the flowchart of FIG. 4 and the reading process shown in the flowchart of FIG. 7 according to the reading work situation, the process in steps S109 and S111 is eliminated with respect to the correction process. May be implemented only.

  Further, as a second modified example according to the present embodiment, in the region correction processing in step S115, the ratio of the region corresponding to the black cell to the predicted region (for example, the region surrounded by C2a, C2b, C2e, and C2f) and white When the difference from the ratio occupied by the area corresponding to the cell is smaller than a predetermined threshold, that is, when it is difficult to determine whether the prediction area corresponds to a black cell or a white cell, this cell area The correction for the code area including the above may be invalidated.

  Here, the predetermined threshold value is set to, for example, about 60 to 80% according to the reading work environment, and the area corresponding to the black cell accounts for 75% and the area corresponding to the white cell occupies. When the ratio becomes the remaining 25%, the difference between the two becomes smaller than the predetermined threshold value, and the correction for the code area including the cell area is invalidated.

  In this way, if the above correction is performed until it is difficult to determine whether the prediction region corresponds to a black cell or a white cell, there is a high possibility that decoding will fail due to incorrect correction. Therefore, in such a case, by making the correction invalid, it is possible to eliminate a decoding failure due to an erroneous correction.

In addition, this invention is not limited to the said embodiment, You may actualize as follows.
(1) As the light receiving sensor 28, a light receiving means for taking in an image signal by a rolling shutter system can be employed instead of the CMOS sensor. Even when such a light receiving means is employed, the above-described deviation of the two-dimensional code can be suitably corrected.

(2) The correction target of the present invention is not limited to the square QR code Q in which a plurality of square black cells and white cells are two-dimensionally arranged, but also rectangular black cells (dark cells) and white cells. A rectangular two-dimensional code in which a plurality of (light color cells) are two-dimensionally arranged may be a correction target of the present invention. In this case, in the above-described reading process, the correction process in step S111 or step S115 is performed in consideration of the rectangular column-direction length and row-direction length.

(3) In the area correction processing in step S115, with respect to the cell area to be corrected, the area surrounded by using the two lines along the column direction among the lines passing through the four corners of the adjacent cell area from the reference side is used as a reference. The prediction region is not limited to prediction, and the prediction region may be predicted based on the characteristics of cell regions adjacent from the reference side, for example, the shape of four sides.

DESCRIPTION OF SYMBOLS 10 ... Optical information reader 28 ... Light receiving sensor (light receiving means)
35 ... Memory 40 ... Control circuit (capture means, decode means, detection means, area correction means, cell length correction means)
Lo ... Reference side

Claims (5)

An optical information reader for optically reading a rectangular two-dimensional code formed by two-dimensionally arranging a rectangular dark color cell and a light color cell,
A light receiving means configured by two-dimensionally arranging light receiving elements capable of receiving reflected light from the two-dimensional code;
Capture means for capturing image information output from the light receiving means by a rolling shutter system;
Decoding means capable of decoding the two-dimensional code included in the image information captured by the capturing means;
A code area corresponding to the two-dimensional code in the image information, and a plurality of cell areas corresponding to either the dark color cell or the light color cell are configured adjacent to each other. Detecting means for detecting an outer shape;
When one side that is first captured by the capturing unit among the four sides that constitute the outer edge of the outer shape detected by the detecting unit is used as a reference side, with reference to the cell region in a row adjacent to the reference side, With respect to a cell area adjacent to the cell area from the side opposite to the reference side, an area occupied in the code area is predicted, and whether the cell area corresponds to the dark cell or the light cell from the predicted area. In addition, for the cell regions in other rows, the region occupying the code region is predicted based on the cell region adjacent from the reference side, and the cell region is determined to be the dark cell and the bright cell from the predicted region. An area correction unit that corrects the code area by estimating which color cell corresponds to the cell area in a row close to the reference side.
With
The optical information reading apparatus characterized in that the decoding means decodes either a two-dimensional code included in the image information or a two-dimensional code in which the code area is corrected by the area correction means. When the length of the cell region in the column direction orthogonal to the reference side is the column direction length, the length of the other row is equal to the column direction length of the cell region of the row adjacent to the reference side. Cell length correction means for correcting the column direction length of the cell region,
The decoding means includes any one of a two-dimensional code included in the image information and a two-dimensional code in which the length in the column direction is corrected by the cell length correcting means and the code area is corrected by the area correcting means. The optical information reading device according to claim 1, wherein the optical information reading device is decoded. The area correction means includes
With respect to the cell region to be corrected, the cell region is based on the region surrounded by two lines along the column direction orthogonal to the reference side among the lines passing through the four corners of the adjacent cell region from the reference side. The area occupied in the code area is predicted, and from this predicted area, it is estimated by correcting whether the cell area corresponds to the dark color cell or the light color cell. The optical information reading device described.   When the difference between the ratio of the area corresponding to the dark cell and the ratio of the area corresponding to the light cell is smaller than a predetermined threshold for the predicted area, the cell area includes the cell area. The optical information reading apparatus according to claim 1, wherein correction for the code area is invalidated.   The optical information reading apparatus according to claim 1, wherein the light receiving unit is a CMOS sensor.

Images