JP2009205228A - Code reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a code reader capable of very precisely reading a code even when reflection characteristics of light on the surface of a reading object with the code formed thereon. <P>SOLUTION: The code reader for reading a code marked on the surface of an object to be read includes: a case having a reading opening part; a first light source means for irradiating a two-dimensional area including the code with illumination light from an epi-illumination direction via the reading opening part; a second light source means for irradiating the two-dimensional area with illumination light from an oblique direction via the reading opening part; an imaging means for receiving first light source reflected light reflected by the illumination light of the first light source means from the two-dimensional area and second light source reflected light reflected by the illumination light in the second light source means from the two-dimensional area; an image processing part for generating an image for reading codes by differentially processing an image of the first light source reflected light and an image of the second light source reflected light; and a decoding means for reproducing predetermined data corresponding to codes based on the image for reading codes. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a code reader that optically reads a two-dimensional code or the like formed on the surface of an object. More specifically, the imaging means and the image processing means are improved so that the code can be read with high accuracy. The present invention relates to a code reader.

  In recent years, in order to recognize management information of products and parts in a short time, one-dimensional or two-dimensional codes in which information such as product and part numbers, product names, and prices are symbolized by black and white striped patterns have been widely used. Yes. These code patterns are represented by marks having different reflectivities. For example, in a one-dimensional code, a series of numbers and letters are represented by a combination of line width ratios, and numbers and names of products and parts. Various information such as price has been replaced with the above numbers and letters.

  For example, a code represented by a barcode is read by a reading device called a barcode reader. This barcode reader is a device that shines light on a barcode, receives light returned from white and black stripes with different reflectivities, and decodes them into original numbers based on the intensity pattern of the reflected light. is there. This type of code reading apparatus includes a hand-held type in which an operator holds the apparatus in his hand and a stationary type tap that allows a product with a bar code to pass through the reading window. In general, the former type uses a light emitting diode as a light source, and the latter type uses a laser beam as a light source.

  Among these, hand-held (handy type) code readers are frequently used in supermarkets, department stores, convenience stores and the like as point-of-sale information management (POS) systems. FIG. 12 is a perspective view showing an example of a general handy type barcode reader. In the figure, the main body 101 of the barcode reader 100 has a substantially rectangular parallelepiped shape with a transverse section having an “L” shape. A code reading unit 102 is provided at the tip of one end of the main body 101, and commands such as registration, deletion, display, and guidance of read code data are input to the upper surface of the other end of the main body 101. A display unit 104 including a numeric keypad 103 and a liquid crystal panel for displaying predetermined items is provided.

  When using the code reader 100, the user holds the other end of the main body 101 with one hand, presses the reading unit 102 against the code to be read, and a trigger button provided on the side surface of the main body 101 Press 105. Then, since the code is read via the reading unit 102, the user presses a predetermined numeric key 103 to input a command for registering and displaying the code data.

  Conventionally, this type of handy-type code reader has been intended for one-dimensional codes and two-dimensional codes encoded in a pattern such as black and white. However, in recent years, in the field of handling industrial products and the like, devices for reading a two-dimensional code or a one-dimensional code directly marked on the surface of an object such as metal, ceramics, and a polymer compound have been developed.

  Currently, the direct part marking (DPMI) technique includes dot peening and laser markers. Among these, the dot peen is marked by denting the surface of the product, so that it has a feature that it is excellent in durability and forms a print that does not disappear. For example, it is used for product management such as an engine block.

JP 2000-298698 A

  Conventionally, in a code reader used to read a code that is directly dot-marked on a glossy surface such as metal, an image is obtained by irradiating oblique illumination light as means for irradiating a code that is a reading object. And means for irradiating with coaxial epi-illumination light and imaging. Among these, in the image generated by the former imaging means, a bright code portion (dot portion) is projected on a dark background, while in the image generated by the latter imaging means, a dark code portion is projected on a light background. It has become.

  If the light reflection characteristics of the metal to be read are uniform, any imaging means may be adopted depending on the characteristics, but in practice, various kinds of metals having different light reflection characteristics may be used. It is necessary to read the code marked on the surface. For this reason, in the conventional code reader, when the proper conditions of each imaging means are not met, scratches on the surface, cutting traces such as hairlines, cast skin, and uneven surface areas such as plating are dots on the captured image. As a result, the image quality deteriorates and the code cannot be read accurately.

  Accordingly, the present invention has been made in view of the above circumstances, and the object of the present invention is to read a code with high accuracy even when the reflection characteristics of light on the surface of the reading object on which the code is formed are different. An object of the present invention is to provide a code reader that can be configured and used easily.

  An object of the present invention is to provide a code reading apparatus for optically reading a code marked on the surface of a reading object, a housing having a reading opening, and a two-dimensional area including the code through the reading opening. First light source means for irradiating illumination light from the incident direction, second light source means for irradiating illumination light from the oblique direction to the two-dimensional area through the reading opening, and illumination light from the first light source means Imaging means for receiving the first light source reflected light reflected from the two-dimensional area and the second light source reflected light reflected from the two-dimensional area by the illumination light of the second light source means through the reading aperture; An image processing unit that generates a code reading image by performing a difference process between the image of the first light source reflected light and the image of the second light source reflected light, and a predetermined corresponding to the code based on the code reading image De By and a decoder means for reproducing data is achieved.

  Further, the object is that the imaging means is a color camera, the illumination light of the first light source means and the illumination light of the second light source means are light of different colors, and the color camera is the first camera. By imaging the reflected light of the illumination light simultaneously irradiated from the light source means and the second light source means, and the image processing unit separates the captured image of the color camera based on the color component of the illumination light This is effectively achieved by generating an image of the first light source reflected light and an image of the second light source reflected light.

  Further, the above object is effectively achieved by the fact that the color of illumination light of the first light source means and the second light source means is any one of red, green, and blue.

  Further, the object is to provide an optical filter that allows only the wavelength component of the illumination light of the first illuminating means to pass between the first illuminating means and the reading opening, and the optical filter is at least the imaging device. This is achieved effectively by having a hole at the location where it intersects the field of view of the means.

  Further, the above object is effectively achieved by arranging the image processing unit in the housing.

  According to the code reading device of the present invention, an image captured by irradiating illumination light on the code to be read from the incident direction, and an image captured by irradiating the illumination light from the oblique direction on the code. Difference processing is performed to generate a code reading image. As a result, a code reading image from which noise on the glossy surface of the reading object is removed is generated, and stable and highly accurate code reading can be executed.

  Further, the image pickup means is a color camera, and the first light source means (the incident light direction) and the second light source means (the oblique direction) are illuminated with different colors of illumination light while simultaneously irradiating from the incident and oblique directions. Then, by separating the captured image based on the color component of the illumination light, an image for each illumination direction can be obtained. As a result, since only one imaging operation is required for one code, the imaging time can be greatly shortened, and it is possible to perform reading that is resistant to blurring of the subject due to movement of the code and camera shake due to movement of the reading device. .

  Further, an optical filter that allows only the wavelength component of the illumination light of the first light source means to pass is provided between the first light source means and the reading opening, and a hole is formed in the center of the optical filter that intersects the field of view of the imaging means. Set up. Thereby, it is possible to prevent the generation of a false image caused by part of the illumination light emitted from the second light source means being reflected by the reading target and then being reflected again by the first light source means.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Each embodiment described below is a handy type code reading device that reads a dot-like code provided by direct part marking (DPMI: Direct Part Marking Identification) on the surface of a reading object made of metal or the like. The present invention is applied.

[First Embodiment]
FIG. 1 is a cross-sectional view schematically showing a basic configuration of a code reading apparatus according to an embodiment of the present invention according to the first embodiment of the present invention. In FIG. 1, a code reading device 1 has a housing 2 having an L-shaped cross section that can be operated by a user with one hand, and a reading opening 2a is formed at one end of the housing 2. The trigger button 3 for image capture is provided at the bent portion. The code 5 marked on the surface of the reading object (metal plate or the like) 4 is optically read by the code reading device 1 through the reading opening 2a.

  The code reading device 1 includes an incident light source (first light source) 6 that irradiates illumination light 6L from an incident direction to a two-dimensional area including the code 5 via a reading opening 2a, and a reading opening. An oblique light source (second light source) 7 that irradiates illumination light 7L from the oblique direction to the two-dimensional area via 2a, and an imaging unit 8 that receives reflected light of the illumination light irradiated to the two-dimensional area; An image processing unit 9 for processing an image captured by the imaging unit 8.

  The image pickup unit 8 is a CCD type or MOS type color camera, and has a lens 8a for focusing the picked-up image on the color camera, and is arranged above a substantially central portion of the reading opening 2a. The two long dotted lines extending downward from the imaging unit 8 indicate the outer edge of the visual field 8V of the imaging unit 8, and the visual field 8V is set to be slightly smaller than the reading opening 2a. ing. Further, it is preferable that the camera optical axis of the image pickup unit 8 is tilted by about 10 ° with respect to the incident direction, whereby the reflection of the ghost image of the light receiving unit can be removed from the visual field 8V.

  The epi-illumination light source 6 and the oblique light source 7 are composed of a high-intensity LED array or the like, and both emit light of different colors. In particular, the color used for the illumination lights 6L and 7L is preferably one of the three primary colors (red, green, and blue). In the present embodiment, the oblique light source 7 uses an LED that emits red light. On the other hand, an LED that emits green illumination light is used as the incident light source 6. The oblique light source 7 preferably has an incident angle of the illumination light 7L (an angle formed between the surface of the cord 5 and the incident light beam) of 35 to 55 °, and particularly preferably 45 °.

  In the code reading device 1 having such a configuration, the trigger button 3 is pulled in a state where the reading opening 2a of the housing 2 is brought close to the surface of the reading object 4 on which the code 5 is marked in a substantially parallel manner. Thus, the illumination light 6L and 7L are irradiated from the incident light source 6 and the oblique light source 7 to the reading object 4 through the reading opening 2a, and the reflected light from the reading object 4 passes through the reading opening 2a. The image is received by the imaging unit 8 and an image of a two-dimensional area including the code 5 is captured.

  FIG. 2 is an explanatory diagram showing an optical path of oblique illumination light, and FIG. 3 is an image of a reading target imaged using the oblique illumination light. As shown in FIG. 2, among the oblique illumination light 7 </ b> L emitted from the oblique light source 7, the light reflected by the code 5 in which the dot-shaped recess is formed is received by the imaging unit 8, while the code 5 The light reflected by the surface of the reading object 4 in the vicinity of is not received by the imaging unit 8. Accordingly, in the image obtained by capturing the reflected light of the oblique illumination light 7L, as shown in FIG. 3, the code 5 is generally white and the surface of the reading object 4 around the code 5 is black. However, scratches such as cutting marks formed on the surface of the reading object 4 also appear white, and the clarity of the rectangular cord 5 is lowered as a whole.

  FIG. 4 is an explanatory diagram showing an optical path of the epi-illumination light, and FIG. 5 is an image of the reading target imaged using the epi-illumination light. As shown in FIG. 4, of the incident illumination light 6 </ b> L emitted from the incident light source 6, the light reflected by the surface of the reading object 4 around the code 5 is received by the imaging unit 8. The reflected light is not received by the imaging unit 8. Therefore, in the image capturing the reflected light of the epi-illumination light 6L, as shown in FIG. 5, the code 5 is roughly black and the surface of the reading object 4 around the code 5 is white. However, scratches such as cutting marks formed on the surface of the reading object 4 also appear dark, and the sharpness of the upper side portion of the rectangular cord 5 is particularly low.

FIG. 6 is a block diagram showing an image processing flow of the code reading apparatus according to the present embodiment.
In the figure, a reading object 4 including a code (mark) 5 irradiated with oblique illumination light 7L and epi-illumination light 6L is picked up by a color camera (image pickup unit) 8, and the picked-up image is stored in the housing 2. Is sent to the image processing unit 9 provided in FIG.

  In the image processing unit 9, first, a captured image captured by the color camera 8 is separated based on color components, and an image by color (R (red light) image, G (green light) image, B (blue light) image). ) Is generated. In the present embodiment, the image shown in FIG. 3 is an image A (R image) generated based on the reflected light of the oblique illumination light 7L (red light emission), and the image shown in FIG. It is the image B (G image) produced | generated based on the reflected light of epi-illumination light 6L (green light emission).

Next, the image A and the image B generated based on the color components of the illumination lights 6L and 7L are subjected to differential processing based on the following [Equation 1] to generate a decoded image for reading the code 5.
[Formula 1]
C = (A * Offs_A) − (B * Offs_B)
IF C> 255 THEN C = 255
IF C <0 THEN C = 0
Here, “A” is a pixel value (0 to 255) in the image A at a predetermined position, and “Offs_A” is an offset value (0.1 to 2.0) depending on the setting of the imaging unit 8. . “B” is a pixel value (0 to 255) in the image B at the same position, and “Offs_B” is an offset value (0.1 to 2.0) depending on the setting. Further, “C” is a pixel value obtained as a result of the difference processing.

  The decoded image generated by the image processing unit 9 is output to a decoding unit (not shown) that reproduces data recorded in the code 5 based on the image data, and predetermined data corresponding to the code 5 is reproduced. The

  FIG. 7 is a decoded image generated by performing a differential process on the two images A and B. Comparing this decoded image with the color-by-color images in FIGS. 3 and 5, in the decoded image in FIG. 7, scratches such as cutting marks formed on the surface of the reading object 4 also disappear, and the code 5 becomes clearer. You can see that it is displayed.

  In the present embodiment, the oblique illumination light 7L emits red light and the epi-illumination light 6L emits green light. However, the present invention is not limited to this, and the oblique illumination light 7L and the epi-illumination light are used. As long as the illumination light of a color different from that of the light 6L is used, any emission color and combination may be used.

  As described above, in the code reading device 1 according to the present embodiment, the image 5 based on the reflected light of the incident illumination light 6L and the reflection of the oblique illumination light 7L are reflected on the code 5 formed on the surface of the reading object 4. An image A based on light is generated, and the two images A and B are differentially processed to generate a decoded image with high definition. Thereby, the noise on the glossy surface of the reading object 4 in the decoded image is removed, and stable and highly accurate code reading can be executed.

  In the code reading apparatus 1 according to the present embodiment, the imaging unit 8 is a color camera, and the incident light source 6 and the oblique light source 7 use different colors of illumination light, and the light sources 6 and 7 are simultaneously emitted. Images are captured as they are, and the captured images are separated based on the color components of the illumination light to generate images A and B for each illumination direction. As a result, the number of times of imaging for one code 5 can be reduced to one, so that the imaging time is greatly shortened and reading that is resistant to blurring of the subject accompanying movement of the code 5 and camera shake accompanying movement of the code reader 1 is executed. can do.

  FIG. 8 is a block diagram showing a modification of the image processing flow of the code reading apparatus according to the present embodiment. In this modified example, when the trigger button 3 is pulled, one of the epi-illumination light source 6 and the oblique light source 7 is activated, and the image of the reading object 4 is picked up by the image pickup unit 8, and then one of the light sources is stopped. Then, the other light source is activated, and an image of the reading object 4 is picked up by the image pickup unit 8. The two captured images A and B are sent to the image processing unit 9. In the image processing unit 9, the captured image A and the captured image B are subjected to differential processing based on the above-described [Equation 1] to generate a decoded image for reading the code 5.

  With the above-described configuration, in this modified example, a decoded image with high definition can be obtained as well as the first embodiment described above, and monochrome imaging is adopted, for example, without being limited to color imaging. Therefore, the cost of the component parts can be reduced.

[Second Embodiment]
FIG. 9 is a cross-sectional view of an essential part schematically showing a basic configuration of a code reading apparatus according to the second embodiment of the present invention. In the figure, the same members as those in the first embodiment described above are denoted by the same reference numerals, and the description thereof is omitted.

  The code reader 1 ′ according to the present embodiment is different from the first embodiment described above in that the optical filter 10 is disposed between the incident light source 6 and the reading opening 2a. . The optical filter 10 is configured to allow only the incident illumination light 6L to pass therethrough, and a hole 10a is formed in the center thereof. The hole 10 a is provided so that the imaging unit 8 can capture the oblique illumination light 7 </ b> L reflected by the cord 5. Therefore, the hole 10a is formed at least at a portion of the optical filter 10 that intersects the visual field 8V of the imaging unit 8.

  FIG. 10 is a mirror image captured by providing the optical filter 10 between the incident light source 6 and the reading opening 2a, and FIG. 11 is a mirror image captured without the optical filter 10. In FIG. is there. Comparing these figures, it can be seen that the image of FIG. 11 has more light spots than the image of FIG. That is, this result means that a false image generated by re-reflecting the incident light source 6 after being partially reflected by the reading object 7L is cut by the optical filter 10. ing.

  In the code reading device 1 ′ according to the present embodiment having the above-described configuration, the same effect as that of the first embodiment described above can be obtained, and between the incident light source 6 and the reading opening 2a, By providing the optical filter 10 that allows the incident illumination light 6L to pass therethrough, it is possible to prevent the generation of a false image caused by the oblique illumination light 7L being reflected again by the incident light source 6. As a result, the occurrence of erroneous code recognition due to false images can be reduced, and more accurate code reading can be performed.

  As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to this, In the range which does not deviate from the meaning, it can change suitably.

It is sectional drawing which shows schematically the basic composition of the code reader which concerns on 1st Embodiment of this invention. It is explanatory drawing which shows the optical path of oblique illumination light. It is the image of the reading target imaged using the oblique illumination light. It is explanatory drawing which shows the optical path of epi-illumination light. It is the image of the reading target imaged using epi-illumination light. It is a block diagram which shows the image processing flow of the code reader which concerns on 1st Embodiment. It is an image of a reading object subjected to image processing. It is a block diagram which shows the modification of the image processing flow of the code reader which concerns on 1st Embodiment. It is principal part sectional drawing which shows roughly the basic composition of the code reader which concerns on 2nd Embodiment of this invention. It is the image of the mirror surface imaged by providing an optical filter between the incident light source and the reading opening. It is the image of the mirror surface imaged without providing an optical filter between an epi-illumination light source and a reading opening part. It is a perspective view which shows an example of a general handy type barcode reader.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Code reader 2 Case 2a Reading opening 4 Reading object (metal plate)
5 code (direct marking)
6 Epi-illumination light source (first light source)
6L Epi-illumination light 7 Oblique light source (second light source)
7L Oblique illumination light 8 Imaging unit 8V Field of view 9 Image processing unit 10 Optical filter 10a Hole

Claims (5)

A code reader for optically reading a code marked on the surface of a reading object,
A housing having a reading opening;
First light source means for irradiating illumination light from the incident direction to the two-dimensional area including the code through the reading opening;
Second light source means for irradiating illumination light from the oblique direction to the two-dimensional area through the reading opening;
The first light source means reflects the first light source reflected light from the two-dimensional area, and the second light source reflected light from the second light source means reflects from the two-dimensional area through the reading opening. Imaging means for receiving light via,
An image processing unit that generates a code reading image by performing a difference process between the image of the first light source reflected light and the image of the second light source reflected light;
A code reading apparatus comprising: decoder means for reproducing predetermined data corresponding to the code based on the code reading image. The imaging means is a color camera, and the illumination light of the first light source means and the illumination light of the second light source means are light of different colors.
The color camera picks up the reflected light of the illumination light simultaneously irradiated from the first light source means and the second light source means; and
The image processing unit generates an image of the first light source reflected light and an image of the second light source reflected light by separating a captured image of the color camera based on a color component of the illumination light. The code reader according to 1.   The code reading apparatus according to claim 2, wherein the color of illumination light of the first light source means and the second light source means is any one of red, green, and blue. An optical filter that allows only a wavelength component of illumination light of the first illumination means to pass between the first illumination means and the reading opening; and
4. The code reading device according to claim 2, wherein the optical filter has a hole at least at a location where the optical filter intersects the visual field of the imaging unit. The code reading device according to claim 1, wherein the image processing unit is disposed in the housing.