JP5104557B2 - Optical information reader - Google Patents

Description

  The present invention relates to an optical information reader.

In an optical information reader that reads an information code such as a bar code or a two-dimensional code, the reflected light from the information code is captured, and an image of the information code is formed on the image sensor by an imaging lens. In general, the image data of the obtained information code is decoded. As an apparatus for optically reading an information code, for example, a device as disclosed in Patent Document 1 is provided.
Japanese Patent Application Laid-Open No. 5-94561

  By the way, in the optical information reading device, the information code is not always imaged with an appropriate size, and if the information code is imaged with a relatively small size with respect to the imaging means, There is a problem in that the pixels are not properly allocated and reading cannot be performed satisfactorily.

  For example, Patent Document 1 discloses a technique related to such a problem. The technique of Patent Document 1 is provided with a zoom lens and a zoom controller capable of zooming in and out on a reflected light path so that the size of an information code displayed on an image sensor (image sensor) can be changed. It is configured. In this configuration, the captured information code is decoded, and if the number of errors exceeds the correction capability, the zoom lens is controlled to enlarge the zoom and the decoding process is repeated.

  However, since the technique of Patent Document 1 alternately performs expansion and decoding of an information code and repeats the process by trial and error, it is unclear whether the image is clearly difficult to decode or whether it can be decoded. It is necessary to perform a series of decoding processes even for a simple image. Therefore, an increase in processing time is unavoidable, and there is a concern that the reading efficiency is lowered.

  The present invention has been made in order to solve the above-described problem, and even when an information code is imaged in a small size, the decoding process can be appropriately performed, and the time required for the decoding process can be reduced. An object of the present invention is to provide an optical information reader that can be reduced as much as possible.

In order to achieve the above object, the invention of claim 1 is directed to an image pickup means having an image pickup element comprising a plurality of pixels, an image forming means for forming an image of reflected light from an information code on the image pickup means, and the image pickup element. Obtaining pixel data corresponding to each pixel based on a signal from the generation unit, generating image data of the information code, and enlargement for performing image enlargement processing on the image data generated by the generation unit An optical information reading apparatus comprising: processing means; feature portion detection means for detecting a predetermined feature portion arranged in a code area of the image data and configured by a plurality of cells; and the feature portion detection means Based on the image of the predetermined feature portion detected by the plurality of pieces of pixel data constituting the image of the predetermined feature portion, the pixel allocation degree for each cell of the predetermined feature portion is determined. An allocation degree detection means for issuing, and the enlargement processing means determines an enlargement ratio according to the pixel assignment degree detected by the assignment degree detection means, and based on the determined enlargement ratio, The image enlargement process is performed on image data, and the predetermined feature portion is determined for each code type of the information code, and the predetermined feature portion includes a specified number of cells and a specified number of cells. The allocation degree detecting means includes an image of the predetermined feature portion detected by the feature portion detecting means and a plurality of pixel data constituting the image of the predetermined feature portion. Based on this, a pixel allocation degree calculation process according to the code type specified by the predetermined feature portion is performed, and the information code captured by the imaging unit is further converted to a one-dimensional code. Determination means for determining whether the information code is a one-dimensional code or not when the information code is determined as a one-dimensional code by the determination means. An interpolation process is performed, and when the information code is determined to be a two-dimensional code, a two-dimensional linear interpolation process is performed .

According to a second aspect of the present invention, in the optical information reading device according to the first aspect, when the information code is a bar code, the characteristic portion detection unit has a light bar and a dark bar at a predetermined width ratio. A line-up portion is detected as the predetermined feature portion, and the allocation degree detection unit is configured to detect the pixel allocation for the unit width of the barcode based on the width ratio and a plurality of pixel data constituting the predetermined feature portion. It is characterized by detecting the degree.

According to a third aspect of the present invention, in the optical information reading device according to the first or second aspect, when the information code is a QR code, the characteristic portion detection unit displays a position detection pattern of the QR code. The allocation degree detection means detects the predetermined feature portion, and the allocation degree detection means determines the pixel allocation degree for one cell of the position detection pattern based on the image of the position detection pattern and a plurality of pixel data constituting the position detection pattern. Is detected.

According to the first aspect of the present invention, a predetermined feature portion arranged in a code area of image data and composed of a plurality of cells is detected, and the detected image of the predetermined feature portion and a plurality of images constituting the predetermined feature portion are formed. The pixel allocation degree for each cell of the predetermined feature portion is detected based on the pixel data. According to this configuration, it is possible to quickly and appropriately grasp how many pixels are assigned to each cell by analyzing a predetermined feature portion.
Further, in the first aspect of the present invention, the enlargement ratio is determined according to the detected degree of pixel allocation, and image enlargement processing is performed on the image data based on the determined enlargement ratio. In this way, it is not necessary to repeat the process by trial and error in order to obtain a reasonable enlargement ratio, and an appropriate enlargement ratio corresponding to the degree of pixel allocation can be quickly acquired. It is possible to perform the operation properly and satisfactorily.

Further, a portion constituted by a prescribed number of cells and a prescribed shape is set as a predetermined feature portion, and a predetermined feature portion is determined for each code type of the information code. The information code has a specified number of cells and a part configured with a specified shape. If this part is used as a predetermined feature, how many pixels are allocated to each cell. Can be calculated with high accuracy without using complicated processing. Furthermore, since the pixel allocation degree calculation process corresponding to the code type specified by the predetermined feature portion is performed, and the image enlargement process corresponding to the specified code type is performed, each method is suitable for each code type. The degree of pixel allocation can be calculated, and an optimum enlargement process can be performed for each code type.

Further, as image enlargement processing , enlargement processing using a linear interpolation method is performed. When the linear interpolation method is used in this way, the image quality after the enlargement process can be made relatively good while shortening the processing time.

Also, it is determined whether the information code captured by the imaging means is a one-dimensional code or a two-dimensional code. If it is determined that the information code is a one-dimensional code, a one-dimensional linear interpolation process is performed as an image enlargement process, When the code is determined to be a two-dimensional code, a two-dimensional linear interpolation process is performed. For each of the one-dimensional code and the two-dimensional code, appropriate interpolation processing can be performed at a necessary level, and the efficiency of the enlargement processing can be improved.

According to the second aspect of the present invention, when the information code is a bar code, a portion where the light color bar and the dark color bar are arranged at a predetermined width ratio is detected as the predetermined characteristic portion. In this way, when the barcode is to be read, the predetermined characteristic portion can be detected easily and quickly based on the width ratio. Further, the pixel allocation degree with respect to the unit width of the barcode is detected based on the width ratio and a plurality of pixel data constituting the predetermined feature portion. In this way, it is possible to easily and accurately grasp the degree of pixel allocation for the obtained barcode image.

In the invention of claim 3 , when the information code is a QR code, the position detection pattern of the QR code is detected as a predetermined feature portion, an image of the position detection pattern, a plurality of pixel data constituting the position detection pattern, Based on the above, the pixel allocation degree for one cell of the position detection pattern is detected. In this way, it is possible to easily and accurately grasp the degree of pixel allocation for each cell of the QR code. In particular, the position detection pattern is a portion to be detected at an early stage during the reading of the QR code, since it is essential part in order to grasp the position of the QR code, the pixel detection of such a position detection pattern If it is also used for grasping the allocation degree, the pixel allocation degree for each cell can be detected very quickly and efficiently, and the image enlargement process and the decoding process can be accelerated.

[First Embodiment]
Hereinafter, an optical information reader 20 according to a first embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the information code reader 20 mainly includes an optical system such as an illumination light source 21, a light receiving sensor 23, a filter 25, and an imaging lens 27, a memory 35, a control circuit 40, an operation switch 42, and a liquid crystal display. A microcomputer (hereinafter referred to as “microcomputer”) system such as the device 46 and a power system such as a power switch 41 and a battery 49 are configured. These are mounted on a printed wiring board (not shown) or housed in a housing (not shown).

  The optical system includes an illumination light source 21, a light receiving sensor 23, a filter 25, an imaging lens 27, and the like. The illumination light source 21 functions as an illumination light source capable of emitting illumination light Lf, and includes, for example, a red LED and a diffusion lens, a condensing lens, and the like provided on the emission side of the LED. In the present embodiment, illumination light sources 21 are provided on both sides of the light receiving sensor 23, and configured to irradiate the illumination light Lf toward the reading object R through a reading port of a housing (not shown). . The reading object R corresponds to a display medium such as a packaging container, packaging paper, or a label, for example, and a barcode or a two-dimensional code is printed on the surface as the information code C, for example.

  The light receiving sensor 23 is configured to receive the reflected light Lr irradiated and reflected on the reading object R or the information code C. For example, the light receiving sensor 23 is an area in which light receiving elements such as C-MOS and CCD are arranged two-dimensionally. A sensor corresponds to this. The light receiving surface 23a of the light receiving sensor 23 is positioned so as to be externally visible through the reading port from the outside of the housing. The light receiving sensor 23 can receive incident light incident through the imaging lens 27 on the light receiving surface 23a. It is mounted on a printed wiring board (not shown). The light receiving sensor 23 corresponds to an example of an “imaging unit”, and the light receiving element (not shown) constituting the light receiving sensor 23 corresponds to an example of an imaging element.

  The filter 25 is an optical low-pass filter that allows passage of light that is less than or equal to the wavelength of the reflected light Lr, and that can block passage of light that exceeds the wavelength, and is provided between the reading port of the housing and the imaging lens 27. Is provided. Thereby, unnecessary light exceeding the wavelength equivalent of the reflected light Lr is prevented from entering the light receiving sensor 23.

  The imaging lens 27 functions as an imaging optical system capable of condensing incident light incident from the outside via a reading port and forming an image on the light receiving surface 23a of the light receiving sensor 23. And a plurality of lenses housed in the lens barrel. In the present embodiment, the illumination light Lf emitted from the illumination light source 21 is reflected by the information code C and is incident on the reading port, and the imaging lens 27 condenses the reflected light Lr. As a result, the code image of the information code C is formed on the light receiving surface 23a of the light receiving sensor 23. The imaging lens 27 corresponds to an example of “imaging unit”.

  Next, a configuration outline of the microcomputer system will be described. 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, an operation switch 42, an LED 43, a buzzer 44, a liquid crystal display device 46, and a communication interface 48. Etc. As the name suggests, this microcomputer system is composed mainly of a control circuit 40 and a memory 35 that can function as a microcomputer (information processing device). The microcomputer system captures an image signal of an information code C imaged by the optical system described above. It can perform signal processing in terms of hardware and software. The control circuit 40 also performs control related to the entire system of the information code reader 20.

  After each light receiving signal (analog signal) output from each light receiving pixel (each element of the light receiving element constituting the light receiving sensor 23) of the light receiving sensor 23 is input to the amplifier circuit 31 and amplified by a predetermined gain, The signal is input to the A / D conversion circuit 33 and converted from an analog signal to a digital signal. These digitized light reception signals are stored in the image data storage area in the memory 35 as image data (image information). The synchronization signal generation circuit 38 is configured to generate a synchronization signal for the light receiving sensor 23 and the address generation circuit 36. 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 received light signal stored in the memory 35 can be generated.

  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 image data storage area, the RAM of the memory 35 is configured to be able to secure a work area and a reading condition table that are used by the control circuit 40 in each processing such as arithmetic operation and logical operation. . 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 piece of hardware such as the illumination light source 21 and the light receiving sensor 23.

  The control circuit 40 is a microcomputer capable of controlling the entire information code reader 20 and includes a CPU, a system bus, an input / output interface, and the like. The control circuit 40 can constitute an information processing apparatus together with the memory 35 and has an information processing function. The control circuit 40 is configured to be connectable to various input / output devices (peripheral devices) via a built-in input / output interface. In this embodiment, the control circuit 40 includes a power switch 41, an operation switch 42, an LED 43, a buzzer. 44, a liquid crystal display device 46, a communication interface 48, and the like are connected. Note that the communication interface 48 is an interface for communicating with an external device, and FIG. 1 illustrates a host computer HST as an example of the external device. With this configuration, for example, monitoring and management of the power switch 41 and the operation switch 42, turning on / off the LED 43, turning on / off the buzzer 44 capable of generating a beep sound and an alarm sound, and the liquid crystal display device 46 The control circuit 40 can control screen display, communication operation of the communication interface 48, and the like.

  The power supply system includes a power switch 41, a battery 49, and the like, and supply / cutoff of the drive voltage from the battery 49 is controlled by turning on / off the power switch 41 managed by the control circuit 40. The battery 49 is a secondary battery that can generate a predetermined DC voltage, and corresponds to, for example, a lithium ion battery. In addition, a configuration in which power is separately supplied from the outside without using the battery 49 is also possible. In this case, the battery 49 is not necessary.

Next, the information code reading process will be described.
In the information code reader 20 illustrated in FIG. 1, for example, the information code reading process is performed according to the flow shown in FIG. 2. This reading process is started, for example, with a predetermined operation on the operation switch 42 as a trigger. When the process is started, an image acquisition process is first performed (S1). In this image acquisition process, the reflected light from the information code C is received by the light receiving sensor 23, and image data based on the signal output from each light receiving pixel of the light receiving sensor 23 is stored in the memory 35.
In the present embodiment, the memory 35 and the control circuit 40 correspond to an example of “generating means”, and acquire pixel data corresponding to each light receiving pixel based on a signal from each light receiving pixel of the light receiving sensor 23 to obtain information. It functions to generate code C image data.

  After the image acquisition process of S1, a labeling process is performed (S2). This process is a process of extracting a code area from the image data acquired in S1, and here, the code area is extracted by a known method. Then, feature detection processing is performed on the extracted code area (S3). In the present embodiment, a predetermined feature portion composed of a plurality of cells is determined for each code type of the information code, and in S3, processing is performed so as to detect the predetermined feature portion.

  Specifically, a part configured with a specified number of cells and a specified shape is determined as a predetermined feature part. For example, for two-dimensional codes such as a QR code, a maxi code, and a data matrix code, Each type-specific position detection pattern is used as a predetermined feature portion. In addition, the one-dimensional code also has a predetermined feature portion that is configured with a specified number of cells and a specified shape. For example, in a barcode, a light color bar and a dark color bar are determined regardless of data contents. A portion arranged at a predetermined ratio (for example, a start code or a stop code for a barcode of CODE 39) is a predetermined characteristic portion. In the process of S3, one of the predetermined characteristic portions determined for each code type is detected in the code area specified in S2.

Thereafter, it is determined whether or not the information code C included in the image data obtained in S1 is a two-dimensional code (S4). Since the predetermined feature portion of the information code has already been detected in the feature detection process of S3, the code type of the obtained information code C can be specified by this predetermined feature portion, and based on this specified code type, S4 The determination process is performed. For example, if a position detection pattern peculiar to a QR code is detected as a predetermined feature portion in S3, the obtained information code is a two-dimensional code, so the process proceeds to Yes in S4. Alternatively, if the start code of the CODE 39 is detected as a predetermined characteristic portion in S3, the obtained information code is a one-dimensional code, so that the process proceeds to No in S4.
In the present embodiment, the control circuit 40 corresponds to an example of “characteristic part detection means”.

  If the information code C included in the image data obtained in S1 is a two-dimensional code, the process proceeds to Yes in S4, and an allocation degree calculation process is performed based on the predetermined feature portion detected in S3 (S5). ). In the present embodiment, the control circuit 40 corresponds to an example of an “allocation degree detection unit”, and includes the detected image of the predetermined feature portion and a plurality of pixel data constituting the image of the predetermined feature portion. Based on this, it functions to detect the degree of pixel allocation for each cell of the predetermined feature portion.

  In the allocation degree calculation process of S5, a code specified by the predetermined feature part based on the image of the predetermined feature part detected by the feature detection process of S3 and a plurality of pixel data constituting the image of the predetermined feature part A pixel allocation degree corresponding to the type is calculated. For example, the image acquired in S1 is a QR code image as shown in FIG. 4A, and the predetermined characteristic portion detected in S3 is a QR code position detection pattern FP as shown in FIG. 4B. In such a case, the pixel allocation degree for one cell of the position detection pattern FP is detected based on the image of the position detection pattern FP and a plurality of pixel data constituting the position detection pattern FP.

  To calculate the degree of pixel allocation per cell, first, as shown in FIG. 4B, one pixel line that obtains a specific ratio in the position detection pattern FP detected as a characteristic portion is determined, and The number of pixels in the position detection pattern area is calculated. That is, in the QR code, the ratio between the dark color area and the light color area is defined to be 1: 1: 3: 1: 1 in a line crossing a predetermined position of the position detection pattern FP. A line L1 in which the ratio of the area to the light color area is 1: 1: 3: 1: 1 is specified, and both end positions P1, P2 of the position detection pattern FP are specified in the line L1, and both end positions P1 are specified. , P2 is calculated. Since the number of pixels Sx is the number of pixels for 7 cells, a value obtained by dividing Sx by 7 (that is, Sx / 7) is calculated as the number of pixels X per cell.

  Then, it is determined whether or not the number of pixels X per cell obtained in S5 is equal to or less than a predetermined threshold value X2 (S6). The threshold value X2 is a threshold value that is a criterion for determining whether or not to perform image enlargement processing. When the number of pixels X per cell exceeds X2, it can be determined that the number of assigned pixels is sufficient. In S6, the process proceeds to No, and the decoding process of S12 is performed without performing the image enlargement process (interpolation process). On the other hand, if the number of pixels X per cell is less than or equal to X2, the number of allocated pixels is insufficient, the process proceeds to Yes in S6, and the two-dimensional interpolation process in S7 is performed.

As described above, in the present embodiment, after determining whether the information code C imaged by the imaging means is a one-dimensional code or a two-dimensional code (S4), image enlargement processing is performed, and the information code When C is determined to be a two-dimensional code, a two-dimensional interpolation process (specifically, a two-dimensional linear interpolation process (FIG. 3A)) is performed as an image enlargement process, and the information code C is one-dimensional. When the code is determined, one-dimensional interpolation processing (specifically, one-dimensional linear interpolation processing (FIG. 3B)) is performed as the image enlargement processing.
In the present embodiment, the control circuit 40 corresponds to an example of “determination means”.

  The two-dimensional interpolation process of S7 is performed according to the flow as shown in FIG. In this process, first, it is determined whether or not the number of pixels X per cell is equal to or less than a threshold value X1 (S71). This threshold value X1 is a reference threshold value for determining the enlargement ratio. When the number of pixels X per cell is equal to or less than the threshold value X1, the process proceeds to Yes in S71, and two-dimensional linear interpolation is performed at a fourfold enlargement ratio. Process. When the number of pixels X per cell exceeds the threshold value X1 (that is, when X1 <X ≦ X2), the process proceeds to No in S71, and two-dimensional linear interpolation processing is performed at a double enlargement ratio. . Two-dimensional linear interpolation processing is known in the field of image processing, and it is also known that linear interpolation processing according to the magnification to be set can be performed in the two-dimensional linear interpolation processing. As shown in FIG. 6A, an intermediate position between adjacent original pixels vertically, horizontally, and diagonally is defined as an interpolation position. As shown in FIGS. There is an example in which interpolation data is generated by linear interpolation using the original pixel of a point.

  For example, FIG. 6B to FIG. 6D and FIG. 7 conceptually explain the two-dimensional linear interpolation processing in the case of a double enlargement ratio. In FIG. An intermediate position between the original pixel data “150” in the m2 column and the original pixel data “50” in the n2 row and the m3 column is set as an interpolation position, and the data “100” at the interpolation position is used as the surrounding four original pixel data. (N1 row, m2 column original pixel data “150”, n1 row, m3 column original pixel data “50”, n2 row, m2 column original pixel data “150”, n2 row, m3 column original pixel data “150” 50 ") by linear interpolation. The same applies to FIGS. 6C and 6D. In FIG. 6C, the intermediate pixel data “150” in the n1 row and m2 column and the original pixel data “50” in the n2 row and m3 column are intermediate. The position is set as an interpolation position, and the data “100” of this interpolation position is converted into the original pixel data of the surrounding four points (original pixel data “150” in the n1 row and m2 column, original pixel data “50” in the n1 row and m3 column). , N2 row, m2 column original pixel data “150”, n2 row, m3 column original pixel data “50”). When interpolation data is generated at an intermediate position between vertically, horizontally, and diagonally adjacent pixels by such a method, interpolation data as shown in FIG. 7 is generated around one original pixel. It is generated between all original pixels. In addition, with respect to the enlargement ratio of 4 times, the point that two interpolation data are generated between each pixel and the point where the generation position of the interpolation data is slightly different from that when the interpolation data is doubled (that is, the original pixel as in the case of 2 times) However, there is a difference in that, for example, two interpolation data are generated at positions obtained by dividing the original pixel into three equal parts, etc. The point of performing linear interpolation using is the same.

  In the present embodiment, the control circuit 40 corresponds to an example of an “enlargement processing unit”, and the image enlargement process (more specifically, the code type specified by the predetermined feature portion is applied to the image data generated in S1. It functions to perform the corresponding image enlargement process). In addition, as in S71 to S73, the “enlargement processing unit” determines an enlargement rate according to the detected pixel allocation degree, and performs image enlargement processing (for image data based on the determined enlargement rate). S72, S73).

  On the other hand, if it is determined in S4 of FIG. 2 that the code is not a two-dimensional code, the process proceeds to No in S4, and it is determined whether or not the information code C obtained in S1 is a one-dimensional code. If it cannot be determined that the code is a one-dimensional code, the process proceeds to No in S8, and the processes after S1 are repeated. If it can be determined that the code is a one-dimensional code in S8, the process proceeds to Yes in S8, and an allocation degree calculation process is performed based on the predetermined feature portion detected in S3 (S9). Also in the allocation degree calculation process of S9, the code type specified by the predetermined feature part based on the image of the predetermined feature part detected by the feature detection process of S3 and the plurality of pixels constituting the image of the predetermined feature part The pixel allocation degree corresponding to is calculated.

  Specifically, as described above, since the portion where the light color bar and the dark color bar are arranged at a predetermined width ratio is detected as the predetermined feature portion, the width ratio and a plurality of pixel data constituting the predetermined feature portion are detected. Based on the above, the pixel allocation degree with respect to the unit width of the barcode is detected. That is, in the barcode as shown in FIG. 5, one module corresponding to the minimum width (unit width) is set as one cell, and the pixel allocation degree per one module is calculated as follows.

  In calculating the pixel allocation degree per unit width, first, as shown in FIG. 5B, a line L2 of pixels crossing the area detected as the predetermined feature portion, and both end positions P11 of the predetermined feature portion in the line L2. , P12 is specified, and the number of pixels Sy arranged between the both end positions P11, P12 is calculated. For example, the predetermined characteristic portion of CODE 39 is a portion where dark bars and light bars are arranged in a ratio of 1: 2: 1: 1: 2: 1: 2: 1: 1, and is for 12 modules (for 12 cells). It corresponds to. Therefore, a value obtained by dividing the number of pixels Sy between P11 and P12 by 12 (ie, Sy / 12) is calculated as the number of pixels Y per cell. The pixel line L2 may be set by arbitrarily extracting a pixel row in the horizontal direction across the barcode in the image data obtained in S1 (that is, data in which pixel data is arranged in a matrix). For example, in the code area extracted in S2, a column of pixels parallel to the bar arrangement direction (that is, a column of pixels orthogonal to the longitudinal direction of each bar) may be extracted and used.

  Then, it is determined whether or not the number of pixels Y per cell (ie, per module) obtained in S9 is equal to or less than a predetermined threshold Y2 (S10). The threshold value Y2 is a threshold value that is a criterion for determining whether or not to perform image enlargement processing. When the number of pixels Y per cell exceeds Y2, it can be determined that the number of assigned pixels is sufficient. The process proceeds to No in S10, and the decoding process of S12 is performed without performing the image enlargement process (interpolation process). On the other hand, if the number of pixels Y per cell is Y2 or less, the number of allocated pixels is insufficient, the process proceeds to Yes in S10, and one-dimensional interpolation processing in S11 is performed.

  The one-dimensional interpolation processing in S11 is performed in the flow as shown in FIG. In this process, first, it is determined whether or not the number of pixels Y per cell is equal to or less than the threshold Y1 (S111). This threshold value Y1 is a reference threshold value for determining the enlargement ratio. When the number of pixels Y per cell (per module) is equal to or less than the threshold value Y1, the process proceeds to Yes in S111, and the enlargement ratio is 4 times. 1-dimensional linear interpolation is performed. On the other hand, when the number of pixels Y per cell exceeds the threshold Y1 (that is, when Y1 <Y ≦ Y2), the process proceeds to No in S111, and one-dimensional linear interpolation processing is performed at a double enlargement ratio. It becomes. As described above, also in the barcode, the enlargement ratio is determined according to the pixel assignment degree calculated in the assignment degree calculation process (S9), and the image enlargement process is performed on the image data based on the determined enlargement ratio. It is carried out.

  One-dimensional linear interpolation processing is also known in the field of image processing, and it is well known that linear interpolation processing according to magnification can be performed in the one-dimensional linear interpolation processing. Use this. For example, with respect to the original image as shown in FIG. 8A, as shown in FIG. 8B, an intermediate position between the original pixels adjacent to the left and right is determined as the interpolation position, and linear interpolation processing is performed. Note that FIG. 8B shows only interpolation between some pixels in the case of a double magnification, but the same applies to other pixels. Also in the case of 4 times, there is a difference that two interpolation data are arranged between each pixel (for example, two interpolation data are arranged at positions where the original pixels are divided into three equal parts), but a known one-dimensional linear The point of generating the interpolation data using the interpolation process is the same as in the case of double.

According to the configuration of the present embodiment, for example, the following effects can be obtained.
The information code reader 20 of the present embodiment detects a predetermined feature portion that is arranged in the code area of the image data and includes a plurality of cells, and detects the detected image of the predetermined feature portion and the image of the predetermined feature portion. Based on the plurality of pieces of pixel data constituting the pixel data, the pixel allocation degree for each cell of the predetermined feature portion is detected. According to this configuration, it is possible to quickly and appropriately grasp how many pixels are assigned to each cell by analyzing a predetermined feature portion.
Further, an enlargement ratio is determined according to the detected pixel allocation degree, and image enlargement processing is performed on the image data based on the determined enlargement ratio. In this way, it is not necessary to repeat the process by trial and error in order to obtain a reasonable enlargement ratio, and an appropriate enlargement ratio corresponding to the degree of pixel allocation can be quickly acquired. It is possible to perform the operation properly and satisfactorily.

  Further, a portion constituted by a prescribed number of cells and a prescribed shape is set as a predetermined feature portion, and a predetermined feature portion is determined for each code type of the information code. The information code has a specified number of cells and a part configured with a specified shape. If this part is used as a predetermined feature, how many pixels are allocated to each cell. Can be calculated with high accuracy without using complicated processing. Furthermore, since the pixel allocation degree calculation process corresponding to the code type specified by the predetermined feature portion is performed, and the image enlargement process corresponding to the specified code type is performed, each method is suitable for each code type. The degree of pixel allocation can be calculated, and an optimum enlargement process can be performed for each code type.

  Further, as image enlargement processing, enlargement processing using a linear interpolation method is performed. When the linear interpolation method is used in this way, the image quality after the enlargement process can be made relatively good while shortening the processing time.

  Also, it is determined whether the information code captured by the imaging means is a one-dimensional code or a two-dimensional code. If it is determined that the information code is a one-dimensional code, a one-dimensional linear interpolation process is performed as an image enlargement process, When the code is determined to be a two-dimensional code, a two-dimensional linear interpolation process is performed. In this way, appropriate interpolation processing can be performed at a necessary level for each of the one-dimensional code and the two-dimensional code, and the efficiency of the enlargement processing can be improved.

  Further, when the information code is a bar code as shown in FIG. 5, a portion where the light color bar and the dark color bar are arranged at a predetermined width ratio is detected as a predetermined feature portion. In this way, when the barcode is to be read, the predetermined characteristic portion can be detected easily and quickly based on the width ratio. Further, the pixel allocation degree with respect to the unit width of the barcode is detected based on the width ratio and a plurality of pixel data constituting the predetermined feature portion. In this way, it is possible to easily and accurately grasp the degree of pixel allocation for the obtained barcode image.

  Further, when the information code is a QR code as shown in FIG. 4, the position detection pattern of the QR code is detected as a predetermined feature portion, an image of the position detection pattern, a plurality of pixel data constituting the position detection pattern, Based on the above, the pixel allocation degree for one cell of the position detection pattern is detected. In this way, it is possible to easily and accurately grasp the degree of pixel allocation for each cell of the QR code. In particular, the position detection pattern is a part that is detected early when reading the QR code, and is an indispensable part for grasping the position of the QR code. If it is also used for grasping the degree, the pixel assignment degree for each cell can be detected very quickly and efficiently, and the image enlargement process and the decoding process can be accelerated.

[Other Embodiments]
The present invention is not limited to the embodiments described with reference to the above description and drawings .

FIG. 1 is a block diagram schematically illustrating an electrical configuration of an information code reader according to the first embodiment of the present invention. FIG. 2 is a flowchart illustrating a reading process performed by the information code reader of FIG. 3A is a flowchart illustrating a two-dimensional interpolation process in the reading process of FIG. 2, and FIG. 3B is a flowchart illustrating a one-dimensional interpolation process in the reading process of FIG. FIG. 4A is an explanatory diagram illustrating an example of image data of a QR code, and FIG. 4B is an explanatory diagram illustrating a predetermined feature portion in the QR code. FIG. 5A is an explanatory diagram illustrating an example of barcode image data, and FIG. 5B is an explanatory diagram illustrating a predetermined feature portion of the barcode. FIG. 6 is an explanatory diagram illustrating an example of generating interpolation data using a two-dimensional linear interpolation method. FIG. 7 is an explanatory diagram for generating interpolation data by two-dimensional linear interpolation, and is a diagram for explaining an example of generating interpolation data around a specific original pixel. FIG. 8 is an explanatory diagram for generating interpolation data by one-dimensional linear interpolation.

Explanation of symbols

20. Information code reader (optical information reader)
23. Light receiving sensor (imaging means)
27. Imaging lens (imaging means)
40... Control circuit (generation means, enlargement processing means, feature portion detection means, allocation degree detection means)

Claims (3)

An imaging means comprising an imaging device comprising a plurality of pixels;
Imaging means for imaging the reflected light from the information code on the imaging means;
Generation means for acquiring pixel data corresponding to each pixel based on a signal from the image sensor and generating image data of the information code;
An enlargement processing unit that performs an image enlargement process on the image data generated by the generation unit;
An optical information reader comprising:
Feature portion detection means for detecting a predetermined feature portion arranged in a code region of the image data and configured by a plurality of cells;
Based on the image of the predetermined feature portion detected by the feature portion detection means and a plurality of pixel data constituting the image of the predetermined feature portion, a pixel allocation degree for each cell of the predetermined feature portion is detected. An allocation degree detection means;
With
The enlargement processing means determines an enlargement ratio according to the pixel assignment degree detected by the assignment degree detection means, and performs the image enlargement process on the image data based on the determined enlargement ratio. Made up of
The predetermined characteristic portion is determined for each code type of the information code,
The predetermined feature portion is a portion configured with a prescribed number of cells and a prescribed shape,
The allocation degree detecting unit is specified by the predetermined feature portion based on the image of the predetermined feature portion detected by the feature portion detecting unit and a plurality of pixel data constituting the image of the predetermined feature portion. The pixel allocation degree calculation process according to the code type
Furthermore, it comprises a judging means for judging whether the information code imaged by the imaging means is a one-dimensional code or a two-dimensional code,
The enlargement processing means performs a one-dimensional linear interpolation process as the image enlargement process when the information code is determined as a one-dimensional code by the determination means, and when the information code is determined as a two-dimensional code. Is a two-dimensional linear interpolation process, an optical information reader.   When the information code is a bar code, the feature portion detection means detects a portion where a light bar and a dark bar are arranged at a predetermined width ratio as the predetermined feature portion,
  2. The allocation degree detection unit detects the pixel allocation degree with respect to a unit width of the barcode based on the width ratio and a plurality of pixel data constituting the predetermined feature portion. 2. The optical information reading apparatus according to 1.   When the information code is a QR code, the characteristic part detection unit detects a position detection pattern of the QR code as the predetermined characteristic part,
  The allocation degree detection means detects a pixel allocation degree for one cell of the position detection pattern based on an image of the position detection pattern and a plurality of pixel data constituting the position detection pattern. The optical information reading device according to claim 1 or 2.

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