JP4853214B2 - Optical information reader - Google Patents

Description

The present invention relates to an optical information reader that reads optical information such as a barcode or QR code (registered trademark) printed or pasted on a product or the like.

2. Description of the Related Art There is known an optical information reading device that attaches a substrate such as paper printed with optical information such as a barcode or QR code to an article or document, optically reads the article, and identifies the article. The optical information reading apparatus illuminates the optical information to which the reading port is directed from the light irradiation means such as the LED inside the case, and guides the light reflected from the optical information by the illumination from the reading port to the inside of the case. An image is read using a CCD or the like, and the information represented by the optical information is decoded from the brightness distribution. Here, Patent Document 1 discloses a symbol reading device that includes two light receiving sensors and can efficiently simultaneously read two types of codes having different sizes.
JP-A-11-312213

However, in the case of optical information such as direct marking, there are a large number of uneven codes because it is directly engraved on metal, etc.In particular, in dot marking, as shown in FIG. A phenomenon occurs in which the center of the cell is whitened, which is a cause of hindering reading.

As an effective means of reading a two-dimensional code consisting of a white cell in the center, it is possible to reduce the influence of unevenness and noise by performing image processing using an averaging filter and intentionally blurring the image. . However, the averaging filter requires an enormous processing time when the image size is large and the range to be averaged is wide.

In Patent Document 1, by providing two light receiving sensors, two types of codes having different sizes can be efficiently read at the same time. However, it cannot cope with dot marking.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an optical information reader capable of quickly reading a direct marking.

In order to achieve the above object, the invention of claim 1 includes a plurality of light receiving sensors 23A and 23B for imaging an information code,
A decoding device 40 for decoding an information code from an image captured by the light receiving sensor;
The plurality of light receiving sensors 23A and 23B are set so as to shift a focal position so that a readable distance is continuous,
In-focus position determining means (S100) for determining whether or not the focal lengths of the images of the respective light receiving sensors are in alignment;
A setting unit 12 for setting which of the image of the light receiving sensor with the focal length and the image of the light receiving sensor with the focal length not selected is selected,
The in-focus position determination means obtains a high frequency component of the image of each light receiving sensor, determines that an image having a high frequency component is in focus, and
When the setting means is set so as to select an image of the light receiving sensor with the correct focal length (S18: Yes), the light receiving sensor with the correct focal length among the images of the plurality of light receiving sensors. The image is selected and decoded (S20), and when it is set to select the image of the light receiving sensor whose focal length does not match (S18: No), the image of the plurality of light receiving sensors is selected. A technical feature is that an image of a light receiving sensor whose focal length is not matched is selected and decoded (S22).

According to the first aspect of the present invention, when a normal two-dimensional code is read, an image of a light receiving sensor having a suitable focal length is set to be selected. Then, it is determined whether or not the focal length is correct, and an image with the correct focal length is selected and decoded. Thereby, a normal two-dimensional code can be read quickly without matching the distance between the optical information reader and the two-dimensional code.

On the other hand, when reading the direct marking, by setting to select the image of the light receiving sensor that does not match the focal length, the focal length is matched among the images of multiple light receiving sensors whose focal positions are shifted. Whether or not the image is out of focus is selected and decoded. Thereby, the direct marking can be quickly read without performing the averaging filter process.

According to the first aspect of the present invention , since the high frequency component of the image of each light receiving sensor is obtained and it is determined that the image having a high high frequency component is in focus, the image of which light receiving sensor is in focus is appropriately determined. it can.

According to claim 2 , in order to determine a high frequency component from the sum of squares of differences between adjacent pixels of the image of each light receiving sensor and to determine that an image having a high frequency component is in focus, the focal length in any light receiving sensor image Can be properly determined.

[First embodiment]
Hereinafter, a first embodiment in which an optical information reading device of the present invention is applied to an optical information reading device for a direct marking QR code and a printed QR code will be described with reference to the drawings. First, an outline of the configuration of the optical information reading apparatus 10 according to the first embodiment will be described with reference to FIGS. FIG. 1 is a partial longitudinal sectional view showing an outline of the configuration of a housing and the like of an optical information reader, FIG. 2 is a view taken along an arrow A of the optical system in the optical information reader shown in FIG. FIG. 2 is a block diagram illustrating a schematic configuration of a circuit unit of the optical information reading device.

As shown in FIG. 1, the optical information reading apparatus 10 that reads the QR code Q mainly includes a housing 11 that has a vertically long, substantially rectangular box shape. The housing 11 is a molded part made of a synthetic resin such as ABS resin, and has a reading port 11a on one end side thereof. The reading port 11a is an opening through which incident light incident on the two first light receiving sensors 23A and the second light receiving sensor 23B shown in FIG. 2 can be introduced. As shown in FIG. 1, a secondary battery 49 is accommodated on the other end side of the housing 11. An opening to which the liquid crystal display 46 can be attached is also formed on the surface side of the housing 11 so that the user of the optical information reader 10 can visually grasp the display contents displayed on the liquid crystal display 46. It is. A circuit unit 20 described later is accommodated in the housing 11. In FIG. 1, printed wiring boards 15 and 16 constituting the circuit unit 20 are shown.

As shown in FIG. 3, the circuit unit 20 mainly includes an optical system such as a pair of red light emitting diodes 21 and a condenser lens 52, a first light receiving sensor 23A, a second light receiving sensor 23B, and imaging lenses 27A and 27B. , A memory 35, a control circuit 40, operation switches 12 and 14, a liquid crystal display 46, and other microcomputer (hereinafter referred to as “microcomputer”) systems, which are mounted or housed on the above-described printed wiring boards 15 and 16. 11 is built in.

An outline of the configuration of the microcomputer system will be described. The microcomputer system includes amplification circuits 31A, 31B, A / D conversion circuits 33A, 33B, memory 35, address generation circuits 36A, 36B, synchronization signal generation circuits 38A, 38B, control circuit 40, operation switches 12, 14, LED 43, buzzer. 44, a liquid crystal display 46, a communication interface 48, and the like. 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). Image signals such as code images captured by the above-described optical system are obtained. 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 optical information reading apparatus 10.

The first light receiving sensor 23A and the second light receiving sensor 23B of the optical system are two-dimensional light receiving sensors of the same type. Image signals (analog signals) output from the first light receiving sensor 23A and the second light receiving sensor 23B are input to the amplifier circuits 31A and 31B and amplified. The image signals output from the amplifier circuit 31A and the amplifier circuit 31B are input to the A / D conversion circuits 33A and 33B and converted from analog signals to digital signals. The digitized image signal, that is, image data (image information) is input to the memory 35 and stored. The synchronization signal generation circuits 38A and 38B are configured to be able to generate synchronization signals for the first light reception sensor 23A, the second light reception sensor 23B, and the address generation circuits 36A and 36B. The address generation circuits 36A and 36B The storage address of the image data stored in the memory 35 can be generated based on the synchronization signal supplied from the synchronization signal generation circuits 38A and 38B.

The control circuit 40 is a microcomputer capable of controlling the entire optical information reader 10 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 the case of the first embodiment, the power switch 41 and the operation switches 12 and 14 are connected. LED 43, buzzer 44, liquid crystal display 46, communication interface 48, etc. are connected. Here, the operation switch 12 is configured to switch between reading a normal printed QR code and reading a direct marking QR code.

The red light emitting diode 21 constituting the optical system functions as a light irradiator capable of irradiating the illumination light Lf, and is condensed by a condenser lens 52 that is a combination of a diffusion lens and a convex lens. In the first embodiment, red light emitting diodes 21 are provided on both sides of the first light receiving sensor 23 </ b> A and the second light receiving sensor 23 </ b> B, and illumination light is directed toward the reading object R through the reading port 11 a of the housing 11. Lf can be irradiated. Note that a QR code Q as an information code is affixed to the reading object R.

The first light receiving sensor 23A and the second light receiving sensor 23B are configured to be able to receive the reflected light Lr irradiated and reflected by the reading object R or the QR code Q via the imaging lenses 27A and 27B. , A two-dimensional image sensor composed of a solid-state image sensor such as a C-MOS or CCD.

The imaging lenses 27A and 27B collect the incident light incident from the outside through the reading port 11a and can form an image on the light receiving surfaces 23a of the first light receiving sensor 23A and the second light receiving sensor 23B. The system functions as a system, and includes, for example, a lens barrel and a plurality of condensing lenses housed in the lens barrel.

As shown in FIG. 4, by the imaging lens 27A, the first light receiving sensor 23A is configured to be focused in a range of a distance d1 centered on a relatively close QR code Qa. On the other hand, by the imaging lens 27B, the second light receiving sensor 23B is configured to be focused in a range of a distance d2 with the QR code Qb at a relatively far distance as the center. Here, since the distance d1 and the distance d2 are set so as to partially overlap (intermediate distance), the optical information reading device 10 is configured to be able to read the optical information with a continuous focal length.

Here, the printed QR code is configured to use an image picked up by the first light receiving sensor 23A or the second light receiving sensor 23B in which the focal length is in accordance with the setting of the operation switch 12. In the first light receiving sensor 23A, a captured image when the focal length is in focus (that is, within the range of the distance d1) is indicated as QR code QaA, and a captured image that is farther than the focal length is indicated as QR code QbA. The QR code QbA whose focal length does not match is blurred. On the other hand, in the second light receiving sensor 23B, the captured image when the focal length is in focus (that is, the range of the distance d2) is indicated as QR code QbB, and the captured image when closer to the focal length is indicated as QR code QaB. Show. The QR code QaB whose focal length does not match is blurred. As will be described later, the optical information reader 10 determines which focal length of the first light receiving sensor 23A and the second light receiving sensor 23B is correct, and performs a decoding process using an image with the correct focal length. .

On the other hand, the QR code composed of direct marking is configured to use an image picked up by the first light receiving sensor 23A or the second light receiving sensor 23B whose focal length does not match with the setting of the operation switch 12. In the first light receiving sensor 23A, the captured image when the focal distance is in the correct range (that is, the range of the distance d1) is indicated as QR code DaA, and the captured image when the focal distance is farther is indicated as QR code DbA. On the other hand, in the second light receiving sensor 23B, the captured image when the focal length is in focus (that is, the range of the distance d2) is indicated as QR code DbB, and the captured image when closer to the focal length is QR code DaB. As shown.

Here, the captured image (QR code DaA) of the direct marking QR code when the focal length captured by the first light receiving sensor 23A is matched is enlarged and shown in FIG. A captured image (QR code DaB) when the focal length is not matched is enlarged and shown in FIG. In the QR code DaA having the same focal length, the central portion of the cell C is blank, and in order to perform decoding using this image, it is necessary to perform processing for blackening the central portion by the averaging filter processing. . On the other hand, if the blurred QR code DbB is used, it is possible to perform the decoding as it is without performing the averaging filter process. Therefore, as will be described later, the optical information reading device 10 determines which focal length of the first light receiving sensor 23A and the second light receiving sensor 23B is out, and decodes using the image with the out of focal length. Process.

Next, the principle of determining whether or not the focal length is correct will be described with reference to FIG.
FIG. 6A is a waveform diagram showing an image signal in which the focal length is not correct, and FIG. 6B is a waveform diagram showing an image signal in which the focal length is correct. As shown in FIG. 6A, when the focal length is not correct, the waveform is dull and does not contain much harmonic components. On the other hand, when the focal length is correct as shown in FIG. 6B, the waveform becomes sharp and includes harmonic components. For this reason, in 1st Embodiment, it is judged whether the focal distance is suitable by whether a harmonic component is high.

ここで^2 は、二乗を表している。 Next, the calculation principle of the harmonic component will be described with reference to FIG.
In the first embodiment, a high frequency component is obtained from the sum of squares of differences between adjacent pixels of the image of the light receiving sensor using the following equation.

Where ^ 2 represents the square.

In the first embodiment, in order to reduce the influence of noise, an average value of arbitrary pixels (where Y1 to Yn are average values of the outputs (256-graded digital values) of pixels in one vertical column (or This calculation is performed for each of the outputs of the first light receiving sensor 23A and the second light receiving sensor 23B, and it is determined that the larger the value of the result X is, the better the focal length is. .

Next, reading processing in the optical information reading apparatus according to the first embodiment will be described with reference to the flowcharts of FIGS. 8 to 10 showing the processing.
First, the first light receiving sensor 23A and the second light receiving sensor 23B are simultaneously exposed (S12), and the images of the first light receiving sensor 23A and the second light receiving sensor 23B are simultaneously captured (S14). Then, it is determined which of the first light receiving sensor 23A and the second light receiving sensor 23B is in focus (focused position determination: S100).

This in-focus position determination process will be described with reference to FIG. 9 showing a subroutine of the process.
First, the harmonic component of the image on the first light receiving sensor 23A (sensor A) side is calculated (S102). This calculation process will be described with reference to the subroutine of FIG. As described above with reference to FIG. 7, any pixel in the image is set as a reference pixel (S202). Here, one vertical column (Y1) composed of an arbitrary number of pixels shown in FIG. Next, the difference between the reference pixel Y1 and the right adjacent pixel Y2 is calculated (Y1-Y2: S204). The difference is squared and added as a total value (+ (Y1-Y2) ^ 2: S206). The reference pixel is shifted to the right by one pixel, and the reference pixel is set to Y2 (S208). Next, it is determined whether or not the processing in the arbitrarily specified range has been completed (S210). However, since the processing has not been completed (S210: No), the processing returns to S204 (+ (Y2−Y3) ^ 2). When the processing of the arbitrarily specified range is completed, that is, when the processing is completed up to the pixel shown in FIG. 7E (S210), the total value is set as the harmonic component of the first light receiving sensor 23A (S212). ).

In the same process, the harmonic component of the image on the second light receiving sensor 23B (sensor B) side is calculated (S104 in FIG. 9). And it is judged whether the harmonic component by the side of the 1st light reception sensor 23A calculated | required by S102 is larger than the harmonic component by the side of the 2nd light reception sensor 23B calculated | required by S104 (S106). If the harmonic component on the first light receiving sensor 23A side is larger than the harmonic component on the second light receiving sensor 23B side (S106: Yes), the image on the first light receiving sensor 23A side is in focus. The subroutine is terminated with the image as the image, the image on the second light receiving sensor 23B side as the image whose focal length is not correct (S108). On the other hand, when the harmonic component on the first light receiving sensor 23A side is smaller than the harmonic component on the second light receiving sensor 23B side (S106: No), the image on the first light receiving sensor 23A side is in focus. And the second light receiving sensor 23B side image is regarded as an image with a suitable focal length, and the processing of the subroutine ends (S110).

Returning to the description in FIG. Subsequent to the in-focus position determination process of S100 described above, parameters are analyzed (S16). Here, it is determined whether the operation switch 12 is set to read a normal printed QR code or a direct marking QR code (S18). Here, when the normal printed QR code is set to be read (S18: Yes), the above S100 indicating which focal length of the first light receiving sensor 23A or the second light receiving sensor 23B is suitable. Based on the result of the determination in step S20, the decoding process is performed using the image on the side with the focal length (S20). On the other hand, when it is set to read the QR code of direct marking (S18: No), based on the determination result of which focal length of the first light receiving sensor 23A or the second light receiving sensor 23B is correct, Decoding processing is performed using the image on the side where the focal length is not matched (S22).

In the optical information reading device of the first embodiment, when reading a normal two-dimensional code, the focal length is in the image of the first light receiving sensor 23A and the second light receiving sensor 23B whose focal positions are shifted. Select the side image and decode it. Thereby, a normal two-dimensional code can be read quickly without matching the distance between the optical information reader and the two-dimensional code. On the other hand, when reading direct marking, an image on the side where the focal length is not suitable is selected and decoded. Thereby, the direct marking can be quickly read without performing the averaging filter process.

In the embodiment described above, an example in which two light receiving sensors are used has been described. Of course, it is possible to use three or more light receiving sensors.

1 is a cross-sectional view of an optical information reading device according to a first embodiment of the present invention. It is an A arrow directional view of the optical system in the optical information reader shown in FIG. It is a block diagram which shows the circuit structure of the optical information reader shown in FIG. It is explanatory drawing which shows the difference in the focal distance of a 1st light receiving sensor and a 2nd light receiving sensor. 5A is an enlarged view of a captured image of direct marking when the focal length is correct, and FIG. 5B is an enlarged view of an image of direct marking when the focal length is not correct. FIG. FIG. 6A is a waveform diagram showing an image signal in which the focal length is not correct, and FIG. 6B is a waveform diagram showing an image signal in which the focal length is correct. It is explanatory drawing which shows the principle which calculates the harmonic component of an image signal. It is a flowchart which shows the reading process by the optical information reader of 1st Embodiment. It is a flowchart which shows the subroutine of the focusing position discrimination | determination process in FIG. 10 is a flowchart showing a subroutine of harmonic component calculation processing in FIG. 9.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical information reader 12 Operation switch 23A 1st light receiving sensor 23B 2nd light receiving sensor 27A, 27B Imaging lens 40 Control circuit

Claims (2)

A plurality of light receiving sensors for imaging the information code;
A decoding device that decodes an information code from an image captured by the light receiving sensor, and an optical information reading device comprising:
The plurality of light receiving sensors are set so as to shift a focal position so that a readable distance is continuous,
In-focus position determination means for determining whether or not the focal lengths of the images of the respective light receiving sensors match,
A setting means for setting which one of the image of the light receiving sensor having the focal length and the image of the light receiving sensor not having the focal length selected is selected,
The in-focus position determination means obtains a high frequency component of the image of each light receiving sensor, determines that an image having a high frequency component is in focus, and
When the setting unit is set to select an image of the light receiving sensor with the focal length in place, the image of the light receiving sensor with the focal length out of the images of the plurality of light receiving sensors is selected. If the image is set to select the image of the light receiving sensor that does not match the focal length, select the image of the light receiving sensor that does not match the focal length from the images of the plurality of light receiving sensors. The optical information reader is characterized by performing decoding. The optical information reading apparatus according to claim 1 , wherein the in-focus position determination unit obtains the high-frequency component from a sum of squares of differences between adjacent pixels.

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