JP6222127B2 - Stamped character reader - Google Patents

Description

  The present invention relates to a stamped character reading device that reads a stamped character stamped on a stamped surface of a steel material, and is particularly suitable for reading a stamped character stamped on a stamped surface of a steel material in a hot process of a steel mill.

  In the case of reading the engraved characters engraved on the engraved surface of the steel in this way, conventionally, for example, the engraved surface is imaged with a commercially available digital camera, the image is displayed on the monitor, and the inspector reads the engraved characters. . In order to automate this, for example, the stamped character is illuminated from a plurality of directions to extract the shadow of the stamped character, and the image is processed to extract the character. Furthermore, in Patent Document 1 below, in order to check the quality of the uneven marking character stamped on the marking surface, the three-dimensional data of the marking surface is obtained using a laser distance meter, and the shape of the marking surface is calculated to obtain the marking. The level difference between the marking surface of the characters is calculated, and the quality check of the concavo-convex marking characters is performed from the level difference.

Japanese Patent No. 5036637

However, it is difficult for any conventional automatic reading device for reading stamped characters to read stamped characters stamped on the marking surface of red hot steel material of 600 ° C. or higher in the hot process of a steel mill, for example. For example, when trying to extract the character by image processing the shadow of the stamped character, because the stamped surface of the steel material has an inclination, a curved surface, and unevenness, the lighting conditions and imaging conditions are not stable, the character part and other The contrast with the part cannot be obtained and the characters cannot be read stably. In addition, when acquiring the three-dimensional distance data of the marking surface using a laser distance meter as in Patent Document 1, generally, red laser light is used for the laser distance meter, and the laser distance by this red laser light is used. The total cannot stably acquire the three-dimensional distance data of the marking surface of the red-hot steel material. Therefore, it is difficult to read a stamped character of red hot steel material of 600 ° C. or higher with a conventional automatic stamped character reader.
The present invention has been made paying attention to the above problems, and an object of the present invention is to provide a stamped character reader capable of reading a stamped character stamped on a stamped surface of a red hot steel material at 600 ° C. or higher. It is what.

  In order to solve the above-mentioned problem, according to one aspect of the present invention, there is provided a stamped character reading device that reads a stamped character that is stamped on a stamped surface of a steel material in a red hot state of 600 ° C. or higher and that is recessed from the stamped surface, A 3D distance information acquisition unit that acquires 3D distance information on the marking surface from the laser distance meter with a specified area resolution using a laser distance meter with a laser beam having a wavelength shorter than green, and 3D distance information on the acquired marking surface A stamped surface state calculation unit that calculates a surface state including a undulation state in the height direction of the stamped surface as surface state three-dimensional distance information of the stamped surface, and based on the calculated surface state three-dimensional distance information of the stamped surface Compared with the three-dimensional distance information of the acquired marking surface, the area with the distance greater than or equal to the threshold is identified as a recessed area, and the character is stamped from the identified existence area of the recessed area. Extract a group Compared with the pre-stored character, the stamp character extraction unit, the stamp character extraction unit that extracts the stamp character from the continuity of the recessed region in the extracted stamp character group, and the extracted stamp character There is provided a stamped character reader including a stamped character recognition unit for recognizing a stamped character.

  Thus, in the marking character reading device of the present invention, the three-dimensional distance information of the marking surface from the laser distance meter is obtained with a laser range finder using a laser beam having a wavelength shorter than that of green, and the obtained marking is obtained. The surface state including the undulation state in the height direction of the marking surface is calculated from the three-dimensional distance information of the surface as the surface state three-dimensional distance information of the marking surface, and the calculated surface state three-dimensional distance information of the marking surface is used as a reference. Compare the 3D distance information of the engraved surface with the acquired threshold to identify the area where the distance is equal to or greater than the threshold as a recessed area, and extract and extract a stamped character group from the area where the identified recessed area exists In the stamped character group, the stamped character was cut out from the continuity of the recessed area, and the cut stamped character was compared with the prestored character to recognize the stamped character, thereby causing a red heat of 600 ° C. or more. Stamped surface of steel It can be read.

It is a schematic block diagram which shows one Embodiment of the stamped character reader of this invention. It is a flowchart of the arithmetic processing for the stamp character reading performed with the arithmetic processing apparatus shown in FIG. It is a longitudinal cross-sectional view of the marking surface and marking character of steel materials. It is explanatory drawing of the three-dimensional distance map of the steel material marking surface acquired with the laser distance meter of FIG. It is explanatory drawing of the three-dimensional distance map of the marking surface state calculated by carrying out noise removal-smoothing by the moving average of the three-dimensional distance map of the steel material marking surface of FIG. It is explanatory drawing of the comparison with the threshold value on the basis of the three-dimensional distance map of the marking surface state of FIG. 5, and the three-dimensional distance map of a steel material marking surface. It is explanatory drawing of the mesh with a dent identified from the comparison result of FIG. It is explanatory drawing of the three-dimensional distance map which removed the data with big variation from the three-dimensional distance map of the steel material marking surface of FIG. It is explanatory drawing of the three-dimensional distance map of the marking surface state calculated by smoothing the three-dimensional distance map of the steel marking surface of FIG. 8 by the weighted least square method. It is explanatory drawing of the comparison with the threshold value on the basis of the three-dimensional distance map of the marking surface state of FIG. 9, and the three-dimensional distance map of a steel material marking surface. It is explanatory drawing of the mesh with a dent identified from the comparison result of FIG. It is explanatory drawing which shows the example from which the threshold value on the basis of the three-dimensional distance map of a marking surface state and the comparison of the three-dimensional distance map of a steel material marking surface differs. It is explanatory drawing of the mesh with a dent specified from the comparison result of FIG. It is explanatory drawing of the stamp character group extracted from the mesh with a dent. It is explanatory drawing of the character cut out from the stamp character group.

  The following embodiments exemplify apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention is the material, shape, structure, arrangement, etc. of components. Is not specified as follows. The technical idea of the present invention can be variously modified within the technical scope defined by the claims described in the claims.

  Hereinafter, an embodiment of a stamped character reader according to the present invention will be described with reference to the drawings. FIG. 1 is a front view showing a schematic configuration of the engraved character reading device of this embodiment, which is arranged at an entry side portion of a hot rolling process of a steel mill. The steel material (slab) S fed to the hot rolling process is long in the right direction in FIG. 1, and the left end surface of the figure is a marking surface F, and the marking surface F is recessed from the marking surface F. Is imprinted. In this embodiment, the marking surface F of the steel material S is scanned with the laser distance meter 1, and the three-dimensional distance data of the marking surface F including the marking characters is acquired as, for example, a three-dimensional distance map (three-dimensional information).

  As the laser distance meter 1 of this embodiment, a laser distance meter using laser light having a wavelength shorter than that of green is used. The steel material S fed to the hot rolling process is red hot at a temperature of 600 ° C. or higher. If a general red laser beam is used, the marking surface of the steel material S is generated by the red wavelength component from the steel material S. F three-dimensional distance data cannot be acquired properly. Therefore, in the laser rangefinder 1 of this embodiment, laser light having a wavelength shorter than that of green is used so that the three-dimensional distance data can be acquired even on the marking surface F of the red hot steel material S. For the green wavelength, for example, the wavelength 546.1 nm specified by the International Commission on Illumination is applied. Therefore, for example, blue or violet laser light having a shorter wavelength is used as the laser light of the laser rangefinder 1 of this embodiment.

  The laser rangefinder 1 deflects the laser beam into a fan shape by, for example, swinging the laser head, and detects two-dimensional, that is, the position information of the laser beam deflection direction and its reflection direction as distance data from the laser rangefinder. It is a two-dimensional laser rangefinder. In this embodiment, the deflection direction of the laser beam by the two-dimensional laser distance meter 1 is set in the vertical direction in FIG. 1, that is, the direction parallel to the paper surface, and the laser distance meter 1 is perpendicular to the paper surface by the moving device 2. By moving (scanning), the three-dimensional distance data of the marking surface F of the steel material S is detected to obtain a three-dimensional distance map. That is, the marking surface F of the steel material S is a three-dimensional distance map in which the position data in the height direction of the marking surface F is superimposed on the two-dimensional position data of the surface parallel to the marking surface F. The state is represented. Therefore, the acquired three-dimensional distance map represents the surface state of the marking surface F of the steel material S. For example, an existing linear guide device or the like is applied to the moving device 2 of the laser distance meter 1, whereby the laser distance meter 1 can be smoothly moved in the direction perpendicular to the paper surface of FIG. In this embodiment, by scanning the two-dimensional laser distance meter 1, the surface state of the marking surface F of the steel material S can be detected with a resolution of 0.3 mm mesh, for example.

Laser beam deflection by the laser distance meter 1 and movement of the laser distance meter 1 by the moving device 2 are controlled by the laser distance meter control device 3, and the three-dimensional distance of the marking surface F of the steel S detected by the laser distance meter 1. The data is converted into a three-dimensional distance map by the laser distance meter controller 3. The laser distance meter control device 3 deflects the laser light of the laser distance meter 1 in the direction parallel to the paper surface of FIG. 1 as described above, and the laser distance meter 1 itself is set in the initial position in the direction perpendicular to the paper surface of FIG. The three-dimensional distance data acquired during this period is converted into a three-dimensional distance map of the marking surface F of the steel material S. The laser distance meter 1 and the laser distance meter control device 3 are controlled by a higher-order arithmetic processing device 4, and the arithmetic processing device 4 reads the engraved characters. The arithmetic processing unit 4 has an advanced arithmetic processing function constituted by a computer system or the like. That is, the stamped character reading device of this embodiment is constructed by arithmetic processing executed in the arithmetic processing device 4. Further, in this arithmetic processing unit 4, imprinted character information on the marking surface F of the steel S fed to the hot rolling process is input from a higher-level arithmetic processing unit (not shown).
FIG. 2 is a flowchart showing the arithmetic processing for marking reading executed by the arithmetic processing device 4. This calculation process is started, for example, by inputting an engraved character reading command by an operator. First, in step S1, the two-dimensional laser distance meter 1 is scanned, and the steel material S is scanned with a prescribed resolution, that is, 0.3 mm mesh (region). A three-dimensional distance map of the marking surface F is created.

  Next, the process proceeds to step S2, in which noise is removed from the acquired three-dimensional distance map of the marking surface F, and the surface state of the marking surface F is calculated from the three-dimensional distance map from which noise has been removed. In this embodiment, since the engraved character is recessed from the engraving surface F, the convex portion protruding from the engraving surface F is only noise from the engraved character to be read. As will be described later, the marking surface F has a scale (floating scale) generated in the steel material manufacturing process as a convex portion in addition to the inclination, the curved surface, and the unevenness as the surface state. Therefore, in the three-dimensional distance map of the marking surface F, a convex portion (a portion having a small distance from the laser rangefinder 1) protruding from the marking surface F by a specified value or more is removed as noise. Then, the surface state of the marking surface F is calculated from the three-dimensional distance map from which noise has been removed in this way. The calculation of the surface state of the marking surface F includes smoothing by a moving average (smoothing filter) and curved surface regression analysis by a least square method, as will be described later.

Next, the process proceeds to step S3, and a mesh whose depth in the three-dimensional distance map of the marking surface F is greater than or equal to the threshold is specified as a concave mesh by threshold determination according to the calculated surface state of the marking surface F.
Next, the process proceeds to step S4, and a stamped character group is extracted from the identified existence area of the mesh with dents.
Next, the process proceeds to step S5, where a stamped character is cut out from the continuity (including discontinuity) of the concave mesh in the extracted stamped character group. In this embodiment, it is assumed that engraved characters exist in a region where the mesh with dents is continuous in the vertical, horizontal, and diagonal directions of the marking surface F, and when the adjacent mesh with dents is 3 mesh or more apart, It is determined that it is a stamped character.
Next, the process proceeds to step S6, where the cut stamped character is recognized as a character by model matching (pattern matching) with a character stored in advance.
Next, the process proceeds to step S7, where the recognized character is collated with the character from the higher-order processing unit, and then the process returns.

  According to this calculation process, the two-dimensional laser rangefinder 1 is scanned to create a three-dimensional distance map of the marking surface F of the steel material S with a specified mesh, and then from the acquired three-dimensional distance map of the marking surface F. The surface state of the marking surface F is calculated from the three-dimensional distance map from which the convex noise is removed and the noise is removed. Thereby, the inclination state, curved surface state, and uneven state of the marking surface F itself are detected. Then, a threshold corresponding to the calculated surface state of the marking surface F is compared with a three-dimensional distance map of the marking surface F, and a mesh whose distance from the laser rangefinder 1 is equal to or greater than the threshold is specified as a concave mesh. This concave mesh is a mesh that is highly likely to be a stamped character. Then, a stamped character group is extracted from the identified existence region of the recessed mesh, and the stamped character is extracted from the extracted stamped character group based on the continuity of the recessed mesh, and the extracted stamped character is stored in advance. It is recognized as a character by model matching (pattern matching). For example, when engraved characters are close to each other, it is difficult to recognize each engraved character, but if it is determined that the engraved character is independent in a portion where the concave mesh is discontinuous, the engraved character is cut out. It is possible to recognize the extracted stamped character by comparing it with model matching. Finally, the recognized character is collated with the character input from the host arithmetic processing unit. If the collation result is not appropriate, for example, the operator is notified of this.

  For example, when the surface state of the marking surface F in the actual steel material S is as shown in FIG. 3, the floating scale C peeled off from the marking surface F has a distance from the laser distance meter 1 as the marking surface F. Therefore, it is a noise when reading engraved characters that are recessed from the engraving surface F. By removing the convex noise, a remarkable convex change from the surface state of the marking surface F can be removed. Consider a case in which, for example, the two-dimensional distance map of the marking surface F in the laser beam deflection direction is as shown in FIG. That is, the three-dimensional distance map of the marking surface F may be considered that the two-dimensional distance map of the marking surface F as shown in FIG. 4 is connected in the direction perpendicular to the drawing sheet. In this three-dimensional distance map, it is considered that there is a dent of a stamped character in a portion where the distance from the laser rangefinder 1 is larger than the other portion by a certain amount or more. In addition, it is considered that a portion where the distance from the laser rangefinder 1 is smaller than the other portion by a specified value or more is convex noise such as a floating scale C.

  Therefore, FIG. 5 shows a smoothed three-dimensional distance map by moving average after removing the convex noise of FIG. For the smoothing by the moving average, for example, a weighted moving average can be used as well known. By smoothing the three-dimensional distance map in this way, the surface state of the marking surface F including the undulation state in the height direction of the marking surface F, that is, the tilt state, the curved surface state, and the uneven state can be detected. it can. A two-dot chain line in FIG. 6 is obtained by adding a prescribed threshold value based on the three-dimensional distance map of the surface state of the marking surface F. This threshold value is compared with the three-dimensional distance map of the marking surface F in FIG. Therefore, as shown in FIG. 7, a mesh whose distance is equal to or greater than a threshold is specified as a concave mesh.

  For detecting the surface state of the marking surface, regression surface analysis by the least square method can be used. For example, FIG. 8 is obtained by removing, as noise, distance data having a larger variation than the other parts of the three-dimensional distance map of FIG. The dent of the engraved character is also considered to be a part of noise when viewed from the original state of the engraving surface F. FIG. 9 shows a surface state obtained by performing regression analysis on the curved surface (curved in the drawing) of the three-dimensional distance map from which the noise is removed by the least square method. In that case, for example, when the least square method is used in which the weight is increased for a mesh having a high data density and the weight is set to a small value for a mesh having a low data density, the reliability of the surface state of the engraved surface F subjected to regression analysis is increased. . The two-dot chain line in FIG. 10 is obtained by adding a prescribed threshold value based on the three-dimensional distance map of the surface state of the marking surface F. Then, this threshold value is compared with the three-dimensional distance map of the marking surface F in FIG. 4, and as shown in FIG. 11, an area where the distance from the laser distance meter 1 is equal to or larger than the threshold value, that is, a mesh is specified as a concave mesh.

  As a method for comparing the three-dimensional distance map of the marking surface F with the threshold value, as a method other than the method described above, the distance data as the surface state of the marking surface F is subtracted from the acquired three-dimensional distance map, and the marking as shown by the solid line in FIG. It is also possible to acquire a three-dimensional distance map of the uneven state with respect to the surface state of the surface F and compare the threshold value with the three-dimensional distance map of the uneven state with respect to the surface state of the marking surface F. And thereby, as shown in FIG. 13, the mesh whose distance from the laser rangefinder 1 is more than a threshold value can be specified as a concave mesh.

  When the concave mesh is specified in this way, a matrix of the concave mesh D and the non-recessed mesh (non-dent mesh) M is formed as shown in FIG. In this matrix, since the region where the concave mesh D exists is considered to be a stamped character group, the stamped character group is extracted. In the extracted engraved character group, the engraved character D exists in a region where the concave mesh D is continuous in the vertical, horizontal, and diagonal directions, and the imprinted character is independent in the non-continuous region of the concave mesh D. Therefore, as shown in FIG. 15, a stamped character is cut out from the independent mesh area with dents, and the character is recognized by a well-known model matching (pattern matching) method.

  As described above, in the marking character reading device of this embodiment, the three-dimensional distance map of the marking surface F from the laser distance meter 1 with the prescribed mesh resolution is obtained by the laser distance meter 1 using a laser beam having a wavelength shorter than green. Obtained in the information obtaining step S1. Then, from the acquired three-dimensional distance map of the marking surface F, a surface state including the undulation state in the height direction of the marking surface F is calculated as a surface state three-dimensional distance map of the marking surface F in the marking surface state calculation step S2. . Using the calculated surface state three-dimensional distance map of the marking surface F as a reference, the obtained three-dimensional distance map of the marking surface F is compared with a threshold value, and a mesh having a distance equal to or greater than the threshold value is defined as a concave mesh. It specifies with specific step S3. When the concave mesh is specified in this way, a stamped character group is extracted from the existence region of the concave mesh in the stamped character group extraction step S4, and the continuity of the concave region in the extracted stamped character group ( A stamped character is cut out in a stamped character cutout step S5, and the cutout character is compared with a previously stored character to recognize the stamped character in a stamped character recognition step S7. Thereby, the marking character of the marking surface of the red hot steel material of 600 ° C. or higher can also be read.

  In addition, in the marking surface state calculation step S2, the convex portion of the marking surface is removed as noise from the acquired three-dimensional distance map of the marking surface prior to calculation of the surface state including the undulation state in the height direction of the marking surface. By doing so, it becomes possible to remove noise unnecessary for reading a stamped character such as a floating scale and to properly calculate the surface state of the stamped surface, and as a result, it is possible to improve the reading accuracy of the stamped character. .

Further, in the stamp character collation step S7, the recognized stamp character is compared with the stamp character information acquired from the host processor, thereby avoiding erroneous feeding of the steel material S to the hot rolling process, for example. It becomes possible.
It goes without saying that the present invention includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention-specific matters described in the appropriate claims from the above description.

1 Laser rangefinder (two-dimensional laser rangefinder)
2 Moving device 3 Laser distance meter control device 4 Arithmetic processing device S Steel (slab)
F Stamp surface L Stamp character C Floating scale

Claims (3)

A stamped character reader that reads a stamped character that is stamped on a stamped surface of a steel material in a red hot state of 600 ° C. or higher and that is recessed from the stamped surface,
A three-dimensional distance information acquisition unit for acquiring three-dimensional distance information of the marking surface from the laser distance meter with a specified area resolution by a laser distance meter with a laser beam having a wavelength shorter than green;
A marking surface state calculation unit for calculating a surface state including a undulation state in the height direction of the marking surface from the acquired three-dimensional distance information of the marking surface, as surface state three-dimensional distance information of the marking surface;
Comparing a threshold value based on the calculated surface state three-dimensional distance information of the marking surface with the acquired three-dimensional distance information of the marking surface, a region having a distance greater than or equal to the threshold value is specified as a concave region. An area identification unit;
A stamped character group extraction unit that extracts a stamped character group from the region of presence of the identified recessed area;
Of the extracted stamped character group, a stamped character cutout unit that cuts out a stamped character from the continuity of the recessed region,
A stamped character reader comprising a stamped character recognition unit that recognizes a stamped character by comparing the cut stamped character with a previously stored character.   Prior to calculating the surface state including the undulation state in the height direction of the marking surface, the marking surface state calculation unit determines the convex portion of the marking surface as noise from the acquired three-dimensional distance information of the marking surface. The stamp character reading device according to claim 1, wherein the stamp character reading device is removed. The stamp character according to claim 1, further comprising a stamp character collating unit that compares the stamp character recognized by the stamp character recognition unit with stamp character information acquired from a higher-order processor. Reader.

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