JPH0434678A - Marking character reader - Google Patents

Abstract

PURPOSE:To convert a picture to a character only with minimum information required for character read by picking up the image of a one-dimensional picture, which has partially variable density because of the distortion of slit light due to ruggedness of a marking character on a marking face, by a one- dimensional image sensor and converting the picture to the character based on its picture information. CONSTITUTION:The image of a marking character irradiated part 4b is picked up as a one-dimensional picture by a line sensor (one-dimensional image sensor) 5 to obtain picture information which has partial variable density corresponding to ruggedness of a marking character 1b on a marking face 1a. The marking face 1a is moved by a moving stage 7 and is mechanically scanned to successively obtain one-dimensional picture information, and this information is inputted to a picture processing device 8. This device 8 smooths the inputted one- dimensional picture to obtain a reference picture indicating the shading and binarizes the inputted picture based on this reference picture to convert the picture to a character. Thus, the picture is converted to the character only with minimum information required for character read to increase the processing speed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a stamped character reading device for automatically reading and recognizing stamped characters on a metal plate used, for example, for product recognition.

[Prior Art] In general, engraved characters are used to identify products for which printed characters or bar codes cannot be used due to the material or customs. For example, a metal plate (metal tag) attached to a wire coil as an identification tag has engraved characters indicating the size, steel type, etc. Products are managed according to the engraved characters, but in recent years, with the rationalization of logistics, there has been an increasing need for devices that can automatically read the engraved characters in order to perform this management quickly and reliably. .

Unlike printed characters, engraved characters have extremely poor contrast, and the biggest challenge for highly reliable recognition is high-precision characterization. Conventionally, engraved character reading devices, such as A method using a light cutting method as shown in FIG. 3 has been proposed (see Japanese Patent Laid-Open No. 63-254588).

In the apparatus shown in FIG. 3, a slit light source 16. Camera 18, distance calculation device 20
．． Scanner 22. Scanning position detector 24. A distance image data processing device 26, a video signal converter 289, and a character recognition device 30 are provided.

Here, the slit light source 16 is for irradiating the slit light SI onto the marking surface 12, and the camera 18 is for capturing a light section image Sv of the light section cut by the slit light SI. The distance calculation device 20 calculates one-dimensional distance distribution data of the light cutting section based on the video signal from the camera 18, and the scanner 22 moves the slit light source 16 and camera 18 in the direction of arrow A ( The scanning position detector 24 is for detecting the scanning position of the optically sectioned image Sv from the position of the scanner 22. Based on the one-dimensional distance distribution data from the distance calculation device 20 and the scanning position from the scanner 22, the distance image data processing device 26 calculates
It is for creating two-dimensional distance distribution data of the stamp surface 12, and the video signal converter 28 is for converting the two-dimensional distance distribution data from the distance image data processing bag [26] into a video signal as a normal grayscale image signal. The character recognition device 30 reads the stamped characters 14 based on the video signal from the video signal converter 28.

With the above-described configuration, the slit light SI from the slit light source 16 is emitted in a direction perpendicular to the direction in which each character 14 is arranged. A light cut image Sv of the light cut portion on the marking surface 12 cut by the slit light SI is captured by the camera 18 and converted into a video signal.

Then, based on the obtained video signal, the distance calculation device 2
0 calculates one-dimensional distance distribution data of the optical cutting section.

When the camera 18 is taking an image as described above, the slit light source 16 and the camera 18 are moved in the direction of the arrow A by the scanner 22, and by changing the irradiation position of the slit light S, the slit light source 16 and the camera 18 are moved on the marking surface 12. The characters 14 are scanned with the optically sectioned image Sv. At this time, the scanning position detector 24 outputs a position signal of the optical cutting section.

Next, the one-dimensional distance distribution data calculated by the distance calculation device 120 and the position signal from the scanning position detector 24 are input to the distance image data processing device 26, and based on these data, two-dimensional distance distribution data is generated. The created two-dimensional distance distribution data is converted into a video signal as a normal grayscale signal by a video signal converter 28. Thereby, the distance difference between the stamped surface 12 and the stamped characters 14 can be recognized.

The converted video signal is then input to the character recognition device 30. This character recognition device 30 performs various image processing, such as noise removal, on the video signal from the video signal converter 28 to improve the S/N ratio, and also uses a character recognition method using pattern matching as a basic method. Read the stamped character 14 with .

[Problems to be Solved by the Invention] However, since the conventional engraved character reading device as described above uses the camera 18, which is a two-dimensional sensor,
In addition to the large number of pixels, the entire distance distribution on the stamping surface 12 is calculated, and information that is ultimately unnecessary (distance of the stamping surface 12) is also captured, so the reading speed is considerably slow and the data is It is also necessary to increase the memory capacity to store the information.

Furthermore, a distance calculation device [20] and a scanning position detector 24 for detecting the scanning position are required, which causes problems such as the device becoming complicated and expensive.

The present invention aims to solve such problems,
To provide a simple and inexpensive engraved character reading device which has a high processing speed and requires a small memory capacity by imaging only the minimum information necessary for character reading and converting it into characters.

[Means for Solving the Problems] In order to achieve the above object, the engraved character reading device of the present invention includes: (1) a light source that irradiates a slit light narrower than the minimum width of the characters to the engraved surface on which characters are engraved; , ■ A one-dimensional image sensor having a field of view parallel to the longitudinal direction of the slit light on the marking surface at or near the irradiation position of the slit light;
A condenser lens that focuses the reflected light of the slit light from the marking surface on a one-dimensional image sensor; ■ A moving means for relatively moving the light source, the one-dimensional image sensor, and the marking surface; ■ Movement by the moving means. The present invention is characterized by comprising an image processing means for performing image processing on image information sequentially obtained from a one-dimensional image sensor and reading characters.

[Function] In the above-described engraved character reading device of the present invention, slit light is irradiated from the light source to the engraved surface, and the reflected light is focused and imaged on the one-dimensional image sensor. Then, this one-dimensional image sensor images a portion parallel to the longitudinal direction of the slit light on the marking surface at or near the irradiation position of the slit light. The captured one-dimensional image includes
Partial shading occurs due to distortion of the slit light due to the unevenness of the engraved characters on the engraved surface.

Such one-dimensional images are sequentially captured while moving the light source, the one-dimensional image sensor, and the marking surface relative to each other using the moving means, and the image processing means changes the shading (imaging information) of the one-dimensional image. Based on this, image processing is performed to read the characters on the stamped surface.

[Embodiments of the Invention] Hereinafter, an engraved character reading device as an embodiment of the present invention will be explained with reference to the drawings. FIG. 1 is a perspective view including a partial block diagram showing its configuration, and FIG. 2 is a perspective view showing the line. FIG. 7 is a plan view showing another example of the sensor field of view.

In Fig. 1, 1 is a metal plate, 1a is a stamped surface on this metal plate 1, 1b is a stamped character ('A' in this example) stamped on this stamped surface 1a, and 2 is for the stamped surface 1a. A laser light source for irradiating a slit light 4 narrower than the minimum width of the engraved character 1b from an oblique direction, 3 a cylindrical lens for making the laser light from the laser light source 2 into a slit shape, 4A a metal of the slit light 4 plate 1
In the slit light irradiation section shown above, this slit light irradiation section 4A includes an engraving surface irradiation section 4a that irradiates the engraving surface la other than the engraving character 1b, and a slit light 4 that is distorted due to the unevenness of the engraving character 1b, causing the engraving. There is an engraved character irradiation section 4b that irradiates the characters 1b.

Further, reference numeral 5 denotes an in-sensor field of view 5 parallel to the longitudinal direction of the slit light 4 on the marking surface la near the irradiation position of the slit light 4.
In this embodiment, as shown in FIG.
It is set to capture an image of the engraved character irradiating section 4b, including the engraved character irradiating section 4b, slightly shifted from a.

Furthermore, 6 is a condenser lens for imaging the slit light irradiation part 4A in the field of view 5A on the line sensor 5, and 7 is a laser light source 2 and a line sensor 5 on which the metal plate 1 is mounted.
A moving stage (moving means) for moving the slit light 4 in a direction perpendicular to the longitudinal direction; 8 is a moving stage 7;
The image processing device 8 performs image processing on the imaging information from the line sensor 5 that is sequentially obtained as the line sensor 5 moves, and converts the stamped characters 1b into characters. The engraved character 1b is carved by extracting the frequency signal and binarizing the difference signal between the output signal and the low frequency signal. Reference numeral 9 denotes a character recognition device that receives information converted into characters about the stamped character 1b from the image processing device 8 and performs character recognition using a technique such as template matching.

With the above configuration, the slit light 4 obtained by slitting the light from the laser light source 2 with the cylindrical lens 3 is obliquely irradiated onto the marking surface 18 on the metal plate 1. Then, while the line sensor 5 images the field of view 5A near the irradiation position, the moving stage 7 moves the metal plate 1 in the longitudinal direction of the slit light 4 while keeping the relative position of the line sensor 5 and the slit light 4 fixed. Move it in the orthogonal direction.

At this time, on the stamping surface 1a, the slit light irradiating section 4A of the slit light 4 is distorted by the unevenness of the stamping character 1b. It will be out of alignment.

In this embodiment, the line sensor 5 images the engraved character irradiation part 4b as a one-dimensional image, and obtains imaged information having partial shading corresponding to the unevenness of the engraved character 1b on the engraved surface 1a.

Then, it is moved by the moving stage 7 to mechanically scan the marking surface 1a, and one-dimensional image information as described above is sequentially obtained and input to the image processing device 8.

The image processing device 8 smoothes the input one-dimensional image to obtain a reference image representing shading, and then binarizes the input image based on this reference image as described above. As a result, character images are converted into characters, and the obtained character images are input to the character recognition device 9.

The character recognition device 9 stores in advance templates of all the characters that can be stamped as the stamped character 1b, and by pattern matching the stored data and the character image from the image processing device 8, the stamped character 1b is created. Which character is recognized?

In this way, according to the engraved character reading device of this embodiment, by using the line sensor 5, the number of pixels is reduced compared to a camera or the like, and the imaging time can be significantly shortened. In addition, since characterization is performed using the minimum information necessary for character reading, which is the imaging information of the engraved character irradiation unit 4b of the slit light irradiation unit 4A, the processing speed can be extremely fast, and the required memory is In addition to being able to significantly reduce the capacity, there is no need for conventional distance calculation devices or scanning position detection means, so the device can be configured simply and at low cost.

In addition, in this embodiment, the slit light irradiation section 4 within the field of view 5A
Since the light A is imaged on the line sensor 5 by the condensing lens 6, there is a large amount of reflected light that can be detected by the line sensor 5, and a clear image can be obtained.

In the above embodiment, the metal plate 1 is moved by the moving stage 7 to perform scanning, but while the relative positions of the line sensor 5 and the slit light 4 (laser light source 2) are fixed, these line sensors 5 Alternatively, scanning may be performed by moving the slit light 4 with respect to the metal plate 1.

Further, in the above embodiment, the field of view 5A of the line sensor 5 is
Although it was set near the irradiation position of the slit light 4 so as to include the engraved character irradiation part 4b of the slit light irradiation part 4A, the second
As shown in the figure, one image information is obtained by setting the field of view 5B of the line sensor 5 at the irradiation position of the slit light 4 on the marking surface 1a so as to include the marking surface irradiating section 4a of the slit light irradiating section 4A. In this case as well, the same effects as in the above embodiment can be obtained.

[Effects of the Invention] As detailed above, according to the engraved character reading device of the present invention, a one-dimensional image in which partial shading occurs due to distortion of the slit light due to the unevenness of the engraved characters on the engraved surface can be converted into a one-dimensional image. Since the system is configured to capture an image using a sensor and transcribe it into text based on the image information, it is possible to transcribe the text using only the minimum amount of information necessary for character reading, which can significantly shorten the imaging time and character recognition processing time. This has the advantage that the device can be constructed compactly and at low cost with a small memory capacity.

[Brief explanation of the drawing]

Figures 1 and 2 show an engraved character reading device as an embodiment of the present invention. Figure 1 is a perspective view including a partial block diagram showing its configuration, and Figure 2 is a view of the field of view of the line sensor. FIG. 3 is a plan view showing another example, and FIG. 3 is a perspective view including a partial block diagram showing the configuration of a conventional stamped character reading device. In the figure, 1-metal plate, 1a-engraved surface, 1b-
Engraved character, 2-Laser light source, 3-Cylindrical lens, 4-Slit light, 4A-Slit light irradiation section, 4a-Engraved surface irradiation section, 4b-Engraved character irradiation section, 5-Line sensor (one-dimensional image sensor)- 5A, 5B - line sensor field of view, 6 - condensing lens, 7 - moving stage (moving means)
, 8-Image processing device, character recognition device.

Claims (1)

[Scope of Claims] A light source that irradiates a slit light beam narrower than the minimum width of the character onto a engraved surface on which characters are engraved; a one-dimensional image sensor having a field of view parallel to the longitudinal direction of the image sensor; a condenser lens that focuses reflected light from the marking surface of the slit light onto the one-dimensional image sensor; and the light source and the one-dimensional image sensor. and an image processing means that performs image processing on image information from the one-dimensional image sensor sequentially obtained as the moving means moves and reads the characters. An engraved character reading device characterized by being equipped with.