JPS63254588A - Marked character reader - Google Patents

Abstract

PURPOSE:To prevent read accuracy from deteriorating by scanning a marked surface with a light cutting image, generating two-dimensional distance distribution data to the marked surface from the result of the scanning, and recognizing the distance difference between a marked character part and the marked surface from the two-dimensional distance distribution data and reading characteristics. CONSTITUTION:Slit light SI is projected on the marked surface 12 at right angles to the array of marked characters and linear distance data on a light cut part is generated from the light cutting image SV of the light cut part cut with the slit light SI. Then the two-dimensional distance distribution data on the marked surface 12 is generated from the scanning position of scanning of the light cutting image SV in the array direction of the characters and linear distance distribution data. Then the generated two-dimensional distance distribution data is converted into a light-shade image signal, from which the distance difference between the marked character part 14 and marked surface 12 is recognized to read the characters. Consequently, the characters marked in the marked surface 12 are accurately read even if there are various factors which deteriorate the read accuracy on the marked surface 12 on an object to be read.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a stamped character reading device, and particularly to a stamped character reading device suitable for automatically reading characters stamped on a metal surface.

[Conventional technology]

BACKGROUND ART Conventionally, in order to manage the sorting of metal products, characters are engraved on the surface of the metal products and management is performed according to the engraved characters. In this case, in order to ensure quick and reliable management, an automatic reading device that automatically reads the stamped characters is usually used. In such an automatic reading device, there is a difference in the amount of reflected light from the part with characters engraved (engraved character part) and the part not engraved on the surface on which characters are engraved (engraved surface) of the fully curved surface. A lighting device is used to project light so that the engraved characters appear, and a television camera is used to image the engraved surface including the illuminated engraved characters.
A character recognition device recognizes and reads the engraved characters from the image signal of the television camera.

[Problems to be solved by the invention]

However, in the conventional automatic reading device, the illumination device projects light so that there is a difference in the reflected light multiplier between the engraved part and the non-engraved part on the engraved surface, but this will be explained below. As such, there is a problem in that sufficient reading accuracy may not be obtained depending on the condition of the stamped surface including the stamped characters. In other words, when characters are engraved on the gas-cut surface of a metal product, the engraved surface is rough and has large irregularities, so it is difficult to see a difference in the amount of reflected light, which means that the signal-to-noise ratio is (S/N") decreases, making it impossible to obtain sufficient reading accuracy.Also, paint may be partially applied to the engraved surface,
If rust occurs, the S/N ratio will further decrease, making it impossible to obtain sufficient reading accuracy. In connection with the present invention, various techniques have been proposed in which markings are applied to steel materials using paint and the markings are automatically read in order to manage products such as steel materials (Japanese Unexamined Patent Application Publication No. 1986-1999). 73473, Japanese Patent Application Publication No. 58-182785, Japanese Utility Model Application No. 61-185158). These techniques can similarly read characters marked by engraving, but
It was not possible to sufficiently compensate for the decrease in reading accuracy due to the decrease in S/N, and this technique did not solve the above problem. Furthermore, JP-A-55-154435 describes a method for automatically evaluating indentations during hardness tests of materials.
In this evaluation method, since the evaluation is performed based on the brightness and darkness of the image of the indentation, the same problem as the above-mentioned problem arises in that the reading accuracy decreases.

[Purpose of the invention]

An object of the present invention is to provide an engraved character reading device that can accurately read characters engraved on an engraved surface of an object to be read even if there are various factors that reduce reading accuracy on the engraved surface of the object to be read. The purpose is 1. Ru.

[Means to solve the problem]

The present invention provides an engraved character reading device that includes means for projecting slit light in a direction perpendicular to the direction in which the characters are arranged on a surface of an object to be read on which characters are engraved, and a means for projecting slit light in a direction perpendicular to the direction in which the characters are arranged; a light cutting means for capturing a light cutting image of the light cutting section to create an image signal; a means for scanning the light cutting means in the direction in which the characters are arranged; a means for detecting a scanning position of the light cutting means; A means for creating one-dimensional distance distribution data of the light cutting portion from the created image signal, and a two-dimensional distance of the surface on which the character is engraved from the detected scanning position and the created one-dimensional distance distribution data. The above object has been achieved by comprising means for creating distribution data, means for converting the created two-dimensional distance distribution data into a grayscale image signal, and means for reading the characters from the converted grayscale image signal. It is something.

[Effect]

In the present invention, unlike conventional reading devices, an illumination device is used to create a difference in illuminance between the engraved character portion and the unengraved portion on the engraved surface of the object to be read, and the engraved character is read from the illuminance difference. Instead, the engraved surface is scanned with a light cut image, two-dimensional distance distribution data from the scanning result to the engraved surface is created, and the distance difference between the engraved character part and the engraved surface is recognized from the two-dimensional distance distribution data. to read the characters. That is, a slit light is projected onto the engraved surface in a direction perpendicular to the direction in which the engraved characters are lined up, and one-dimensional distance data of the light cut section is created from a light cut image of the light cut section cut by the slit light. Then, two-dimensional distance distribution data of the engraving surface is created based on the scanning position obtained by scanning the optically sectioned image in the direction in which the characters are lined up and the -dimensional distance distribution data, and the created two-dimensional distance distribution data is converted into a grayscale image signal. The character is read by recognizing the distance difference between the engraved character part and the engraved surface from the converted grayscale image signal. Therefore, there are various factors that reduce the reading viscosity on the engraved surface of the object to be read. For example, the engraved surface is rough and has large irregularities, or the engraved surface is partially coated with paint. Even if the S/N decreases due to
Characters stamped on the stamp surface can be read with high accuracy. Therefore, since reading errors are eliminated, the sorting of products with stamped characters can be managed reliably.

【Example】

Embodiments of the engraved character reading device according to the present invention will be described in detail below. FIG. 1 is a perspective view, including a partial block diagram, showing the overall configuration of the embodiment and its arrangement with respect to the stamping surface. In the embodiment, in order to read the engraved characters 14 on the engraved surface 12 of the reading object 10, a slit light (symbol SI A slit light source 16 for projecting a light beam (indicated by ); a camera 18 for capturing an image of a light cut section 8I (indicated by symbol Sv) of a light cut section cut by the slit light; and a video signal captured and outputted. Distance calculation device 2 that calculates and creates one-dimensional distance distribution data of the optical cutting section from
0, a scanner 22 for scanning the marking surface 12 with the light cut image Sv by moving the slit light source 16 and camera 18 in the direction of character arrangement, and scanning of the light cut image Sv from the position of the scanner 22. A scanning position detector 24 for detecting a position, and a distance image data processing device 26 for creating two-dimensional distance distribution data of the stamp surface 12 from the created one-dimensional distance distribution data and the detected scanning position. , a video signal converter 28 that converts the created two-dimensional distance distribution data into a video signal as a normal grayscale image signal, and a character HF! that reads the stamped character from the converted video signal. A device 30 is mainly provided. The scanner 22 is screwed with a pedestal 22A to which the slit light source 16 and camera 18 are fixed and movable in the direction in which the characters are lined up. A ball screw 22B for moving in the alignment direction (arrow claw direction in the figure) and the ball screw 2
A scanner drive source 22C for rotationally driving the scanner 2B is provided. The effects of the embodiment will be explained below. The slit light S2 projected from the slit light source 16 is projected in a direction close to perpendicular to the marking surface 12 and perpendicular to the direction in which the characters are arranged. The camera 18 captures a light-cut image SV of the light-cut portion on the marking surface cut by the slit light. The video signal captured and output from the camera 18 is input to the distance calculation device 22, and the distance calculation device 22
calculates one-dimensional distance distribution data of the optical section from the input video signal. When the camera 18 is taking an image as described above, the scanner 2
The second mount 22A is moved in the direction in which the engraved characters are lined up to change the projection position of the slit light Sl, and the engraved characters are scanned by the optically sectioned image Sv. At the same time, the scanning position detector 24 detects the position signal of the optical cutting section. Next, the one-dimensional distance distribution data calculated by the distance calculation device 20 and the detected position signal are input to the distance image data processing device 26 to create two-dimensional distance distribution data. 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. The character recognition device 30 performs various types of image processing on the video signal, such as noise removal, to improve the S/N ratio, and further reads the stamped characters using a character recognition method based on pattern matching. When performing the pattern matching, a character is selected from among the registered character patterns by selecting the one closest to the detected pattern, that is, the engraved character pattern of the video signal. In the embodiment described above, the slit light SI was projected onto the marking surface 12 at a substantially right angle. However, since the slit light Sl only needs to be able to detect the depth of the engraved character 14, either the projection angle of the slit light Sl or the viewing angle of the camera 18 should be oblique.
Or even if both sides are diagonal, the engraved characters 14
The slit light source 16 and camera 18 can be placed at appropriate positions in consideration of the detection conditions as long as the depth can be detected. Further, in the embodiment, as shown in FIG. 1, a mount 22A for scanning the light source 16 and the camera 18;
Although the scanner 22 is illustrated as having a ball screw 22B and a scanner drive source 22C, the light source 16 and camera 18
The means for scanning the characters in the direction in which the characters are arranged is not limited to the scanner having the above-mentioned configuration, and scanning means having other configurations may be used. [Effects of the Invention 1] As explained above, according to the present invention, even if there are various factors that reduce the degree of read rust on the stamped surface of an object to be read, characters stamped on the stamped surface can be accurately read. The excellent effect of being able to read is 1q.

[Brief explanation of drawings]

FIG. 1 is a perspective view, including a partial block diagram, schematically showing the configuration of an engraved character reading device according to the present invention. 1o... object to be read, 12... engraved surface, 14... engraved characters, 16... slit light source, SI... slit light, SV... light cut image, 18... camera, 20...Distance calculation device, 22...Scanner, 24...Scanning position detector, 26...Distance image data processing device, 28...Video signal converter, 30...Character recognition device.

Claims (1)

[Claims] (1) A means for projecting slit light in a direction perpendicular to the direction in which the characters are arranged on the surface of the object to be read on which characters are engraved, and a light-cut image of the light-cut section cut by the projected slit light. a light cutting means for imaging and creating an image signal; a means for scanning the light cutting means in the direction in which the characters are arranged; a means for detecting the scanning position of the light cutting means; and a means for detecting the scanning position of the light cutting means; means for creating one-dimensional distance distribution data of the optical cutting section; means for creating two-dimensional distance distribution data of the surface on which the characters are engraved from the detected scanning position and the created one-dimensional distance distribution data; An engraved character reading device comprising: a means for converting created two-dimensional distance distribution data into a grayscale image signal; and a means for reading the character from the converted grayscale image signal.