JPH05101222A - Method and device for reading character - Google Patents

Abstract

PURPOSE:To provide a method and a device for reading characters which can read the character strings printed on a subject like the steel stock, etc., regardless of the temperature measured on the printed surface of the subject. CONSTITUTION:The character strings printed on a subject are photographed and only these character strings are binarized and extracted out of the photographed image. In this case, the threshold level of binarization is decided by the temperature of the subject. Thus the light/darkness can be properly decided when the video signals of the character strings are printed on a subject having the unfixed temperatures. Therefore it is possible to automatically deal with the difference of heating states (temperatures) and to accurately read the character strings. As a result, the character recognizing performance is improved and any resident operator is not required to read the characters painted mechanically on the end face, etc., of the steel stock. Then the working efficiency is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reading characters printed on a target object such as an end surface of a steel material by a paint spray type printer, and particularly to a target object whose surface temperature is indefinite. The present invention relates to an apparatus and a reading method for suitably reading a written character.

[0002]

2. Description of the Related Art Conventionally, a character string printed on the surface of an object is photographed by a camera, the character string portion of the image is binarized and extracted, and each character is discriminated from the binary data. There is a character reading device that reads the contents of a character string. As an example of such a device, JP-A-2-15348
In JP-A-8, by enclosing the front and rear of a printed character string with specific marks so that the start, end, length, extension direction, etc. of the character string can be easily recognized, the versatility and reliability of character reading are improved. A character reading device having improved property is disclosed.

On the other hand, at the entrance of a heating furnace for heating a steel material, whether the conveyed steel material is a steel object to be heated or not is a character such as a serial number printed on the surface of the steel material. I was judging from the line. At this time, the surface temperature of the steel material is relatively high, and there is a temperature difference depending on the type of steel material.

[0004]

Although it is preferable to use the character reading device as described above to judge the character string, the brightness of the printing surface generally changes depending on the temperature even if the image is taken under the same conditions. It is known that the optimal threshold level for binarizing a character string differs depending on the type of character string. Therefore, the character string printed on the surface of an object whose temperature is indefinite only by the character reading device described above. Since it is sometimes difficult to binarize the above, in the case of steel material, the operator must always read and judge the paint character string printed on the steel material, which tends to lower the work efficiency.

An object of the present invention is to solve the above problems and to provide a character reading device and a reading method capable of reading a character string printed on an object such as steel regardless of the temperature of the printing surface. There is.

[0006]

According to the present invention, the above-mentioned object is to provide a camera for photographing a character printed on an object whose surface temperature is indefinite, and a character portion from an image photographed by the camera. A character reading device having a processing device for extracting the binary data and discriminating the character by a predetermined algorithm, the device having a temperature sensor for measuring a surface temperature of the object, wherein the image is processed by the processing device. Character reading device for determining a threshold level of binarization when extracting a character portion as binary data from a character reading device and printing on an object whose surface temperature state is indefinite In a character reading method in which a captured character is photographed, the character portion is extracted as binary data from the photographed image, and the character is discriminated by a predetermined algorithm. Is achieved by providing a character reading method is characterized by determining in accordance with the binarization threshold levels in extracting as data on the surface temperature of the object.

[0007]

As described above, when the character string printed on the object is photographed and only the character string is binarized and extracted from the photographed image, the threshold level of the binarization depends on the temperature of the object. The determination of brightness is optimized when the video signal of the character string printed on the object whose temperature is indefinite is binarized. Further, by moving the camera and the illumination means to appropriate positions when shooting the character string printed on the target object, the shooting conditions can be kept constant.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram of the character reading device.
The industrial camera 1 is a steel material 2 that is transported by a crane or the like.
Is disposed at a position facing the end surface 2a of the. This industrial camera 1 has traversers 3, 4, so that it can move in three axial directions of an X axis (left and right), a Y axis (front and back), and a Z axis (up and down).
It is supported by 5. Further, the industrial camera 1 is additionally provided with a radiation thermometer 6 for measuring the surface temperature of the end surface 2a of the steel material 2. A lighting device 7 is provided between the industrial camera 1 and the steel material 2 in the Y-axis direction, that is, near the steel material 2.
It is supported by a traverser 8 so as to be movable in a separating direction. Further, an industrial camera 9 for detecting the position of the end surface 2a of the steel material 2 in the Y-axis direction is fixed above the steel material 2.

On the end surface 2a of the steel material 2, a character string 10 consisting of 7 matrix characters each having 5 dots in the horizontal direction and 7 dots in the vertical direction is printed in advance by a paint spraying type printing device. The character string 10 has substantially the same number of digits, character spacing, character shape, character printing direction, and character size, but the thickness and shade of the character differ depending on the maintenance status of the paint device. .. The printing position of each character is not always constant from the left, right, upper and lower ends of the steel material, but differs depending on the type of steel material.

On the other hand, both cameras 1 and 9 are connected to an image processing device 11 for analyzing the image signal thereof, and the video signal is binarized based on an algorithm described later to measure the position of the end face of the steel material printed and read the character. To do. The image processing apparatus 11 is connected to the computer 13.
The computer 13 controls the traverse controller 14 that drives the traversers 3, 4, 5, 8 to the image processing apparatus 1
1 to indicate the moving positions of the industrial camera 1 and the lighting device 7 based on the image data, exchange data with the process control computer 15, take in a temperature signal from the radiation thermometer 6, etc. It is controlled comprehensively.

FIG. 2 is an internal block diagram of the image processing apparatus 11 for executing the image processing algorithm. The industrial camera 1 and the industrial camera 9 are connected to the signal switching unit 17 connected to the binarization circuit 18, and the image data thereof are selectively sent to the binarization circuit 18 depending on the processing purpose. ing. The video data sent to the binarization circuit 18 is converted into binarized data, and is sent to the CPU 1 via the internal bus B.
9 and is processed according to the program stored in the program memory 20. The processing result is displayed on the display device 21 and sent to the computer 13 via the input / output interface 22.

Next, the operating procedure of the character reading apparatus in this embodiment will be described with reference to the flow charts of FIGS. 3 and 4.

First, when the steel material 2 is conveyed in step 1, the process proceeds to step 2, and the radiation thermometer 6 measures the surface temperature of the end surface 2a of the steel material 2. Then, in step 3, the threshold level for binarization in the steel material 2 is determined.

Here, the threshold level for binarization, which is optimum for emphasizing only characters, is different depending on the temperature of the steel material even if other photographing conditions such as illumination are the same. FIG. 5 shows the relationship between the optimum threshold level for binarization and the steel material temperature. In FIG. 4, the horizontal axis represents the threshold level for binarization of the binarization circuit 18 in FIG. 2, and 256 levels of level can be set. The higher the threshold level for binarization, the higher the illuminance of the video signal. Is binarized with a high value. Therefore, the radiation thermometer 6 measures the surface temperature of the steel material 2, the computer 13 determines the binarization level corresponding to the steel material temperature, and sets it to the binarization circuit 18 of the image processing apparatus 11.

Steps 4 to 10 in FIG. 3 are a flow for determining the positions of the industrial camera 1 and the illuminating device 7 with respect to the end surface 2a of the steel material 2.

Here, the steel material 2 is conveyed to the measurement position by a crane or the like, but the steel material 2 is conveyed by human operation.
The transport position of is not always constant. Also, the printing position of the character string 10 is not always constant from the left, right, upper and lower edges of the end surface 2a of the steel material 2, and if the installation position of the industrial camera 1 is fixed, the character string 10 may not enter the shooting field. To do. Therefore, as shown in FIG. 6, it is necessary to move the position of the industrial camera 1 so that the character printing position of the steel material 4 is included in the shooting image field of the industrial camera 1. Also industrial camera 1
By moving to a position where the width of the character string 10 occupying the shooting image field is as large as possible, the information amount of the character data in the measurement image field increases, and the accuracy in measuring the characteristics of the character improves.

First, in step 4, the end face 2a of the steel material 2 is photographed by the industrial camera 1, the image signal is taken into the image processing device 11, and in step 5, the character string 10 on the end face 2a.
Only the character string is extracted by performing the binarization process so that only the character string is extracted. Then, in the step, as shown in FIG. 7, the character string 1 in the photographing field 24 of the industrial camera 1
0 from the Z-axis direction, that is, the brightness level distribution in the vertical direction,
U19 determines the upper end (Z1) and the lower end (Z2) of the character string 10, determines the left end (X1) and the right end (X2) from the brightness level distribution in the X-axis direction, that is, the horizontal direction, and further determines the character string 10 The center (X3, Z3) of a certain area is calculated.

In the next step 6, Y of the industrial camera 1 is set.
In order to determine the axial direction, that is, the front-back direction position, the steel material 2 is photographed by the industrial camera 9 from above the end surface 2a of the steel material 2.
The video signal is taken into the image processing device 11 and binarized to extract only the image of the steel material 2 in the photographing field 25 of the industrial camera 9 as shown in FIG.
The CPU 19 determines the Y coordinate (Y1) of the steel material end portion from the brightness level distribution in the axial direction.

Next, in step 7, the computer 13
From the coordinates X3, Y1, Z3 and the current position of the industrial camera 1, the position of the industrial camera 1 in which the image width of the character string 10 occupying the shooting field 24 of the industrial camera 1 becomes as large as possible. Optimal coordinates as (X3, Y1-
β, Z3) is determined. Where β is the computer 13
The optimum distance between the industrial camera 9 and the steel material 2 calculated by In step 8, the optimum coordinates (X3, Y1-β, Z of the industrial camera 1 obtained as described above are calculated.
3) Based on the data, the computer 13 drives the traversers 3, 4, 5 via the traverser controller 14 to move the industrial camera 1 to a position where the character string 10 can be captured in the optimum shooting image field.

On the other hand, the illuminating device 7 is for illuminating the end face 2a of the steel material 2 and making the character string 10 painted on the end face 2a stand out. As shown in FIG. The end surface 2a of the steel material 2 is illuminated from diagonally below. At that time, the illumination device 7 needs to be arranged at a position where the end face 2a has the optimum illuminance for photographing. When this illumination position is too far from the end face 2a (A), the upper part of the end face 2a becomes bright, and when the video signal captured by the industrial camera 1 is binarized, the character string 10 Noise is generated at the upper end except for. On the contrary, when the illumination position is too close to the end face 2a (B), the lower part of the end face 2a becomes bright, so that the end face 2a can be converted when the video signal captured by the industrial camera 1 is binarized. Noise is generated at the lower end portion other than the character string 10.

Therefore, step 9 in the flow of FIG.
At step 10, the computer 13 uses the Y coordinate (Y1) of the end of the steel material to find the optimum position (Y1-α) of the lighting device 7. Based on this data, the computer 13 sends the data through the traverser controller 14. The traverser 8 is driven to move the lighting device 7 to the optimum lighting position (Y1-α). Then, in step 11, the characters on the end surface 2a of the steel material 2 are read by the flow (FIG. 4) based on the character reading algorithm described below.

Next, the algorithm for determining the character string and the character position for each character from the binarized signal, reading the character for each character, and determining the read result is shown in FIG. explain.

First, in step 21, the character string 10 consisting of 7 characters is extracted from the initial image field (FIG. 10) after the binarization process.
The position (circumscribing rectangle coordinates) of is detected and the initial window is set. This initial window has the upper left coordinates (X,
Y), the horizontal width of the window is L, and the vertical width is M. Here, the coordinate unit of the initial image field is the number of image processing pixels, the upper left of the image field is (0, 0), and the lower right is (299, 29).
9). If the initial image field includes bright points (white points) other than the character string 10, it is determined to be noise.

Next, in steps 22 to 27, the width L of the initial window is corrected. That is, the character string 10 is composed of seven numbers expressed by a matrix of 5 dots horizontally and 7 dots vertically. If all of the numbers have the same width, the X coordinate of each character can be determined by dividing the width L of the character string obtained in step 21 into seven parts, as shown in FIGS. 11 (a), 11 (b) and 11 (c). As shown in, the width of the character “1” is shorter than that of other characters.
If one or both of the left and right ends of is 1,
When the horizontal width L of the initial window becomes shorter than the original horizontal width of the character string 10 and is divided into seven equal parts, an error occurs in the X coordinate of each character. Therefore, when one or both of the left end and the right end of the character string 10 is "1", the width L of the initial window is corrected to prevent the occurrence of this error.

In step 22, only the character at the left end is extracted from the initial window and discriminated. To judge one character, set multiple judgment windows for each character and measure the width, height, and area of the binarized data in that window.
Determine. An example using 20 determination windows will be specifically described with reference to FIGS. 12
As shown in (a) to (e), 20 discrimination windows (W0 to W19) that make it easy to capture the features of each numeral are laid between the left end and a reference width of one character, and the width of each discrimination window
By comparing the vertical width and area with the judgment table of each number (0-9) set in advance for each judgment window, and accumulating the correct numbers, the character (number) with the highest result is displayed at the left end. Recognize as a character. Further, in order to deal with the change in the thickness and shade of the character due to the printing failure, the binarized data is written in the bright point non-inversion mode (the character is white and the background is black (a), (c), (e)). The point inversion mode (characters are black, background is white (b), (d)) is switched to measure the width, height and area of the discrimination window.

In the determination of the leftmost character, the determination in step 22 is performed from the position on the left side of, for example, 30% (actually any amount may be used) from the initial window obtained in step 21, and each determination window (W0-W0). W19) is shifted to the right one pixel at a time, and the same judgment is performed 16 times (actually, it may be any number of times), and the character (number) with the highest legal result is set as the leftmost character. , That position is the leftmost position.

Then, in step 23, it is judged whether or not the leftmost character is "1". If the leftmost character is "1", the character width of the leftmost character is narrower than the original character width. Therefore, as shown in FIG. 11A, the left end position is corrected to the left by the set value XL pixels (step 2).
4).

Next, in step 25, the rightmost character is determined in the same manner as above. That is, the above 20 judgment windows are applied between the right edge of the initial window and the reference width for one character, and the width, height, and area of each judgment window are compared with the above-mentioned judgment table, and the correct numbers are added. Recognizes that the character (number) with the highest result is the leftmost character. Also, in the judgment of the rightmost character,
30% from the initial window calculated in step 21
The determination in step 25 is performed from the position on the right side, and the same determination is performed 1 while shifting each determination window to the left by one pixel.
The character (number) having the highest result of accumulating the legal number 6 times is set as the rightmost character, and that position is set as the rightmost position.

Then, in step 26, it is judged whether or not the rightmost character is "1". If the rightmost character is "1", the character width of the rightmost character is narrower than the original character width. Therefore, as shown in FIG. 11B, the right end position is corrected to the right by the set value XR pixels (step 2).
7). Therefore, for example, when the characters on both the left and right ends are both "1", the left and right widths from the initial window are corrected by XL and XR as shown in FIG. 11C.

In the next step 28, the above step 21
~ The width of the character string 10 is obtained from the left end and right end positions of the character string 10 determined in step 27, and all character positions are determined by dividing the width into seven parts, which are already obtained in step 22 and step 25. The remaining second to sixth characters from the left excluding the left and right ends are determined.

Then, in step 29, the image processing apparatus 1
The character determination result is displayed on the display device 21 of No. 1. If the character having the highest legal number in the judgment window does not exist alone, the judgment is not possible and the character is displayed as "?", And the process proceeds to step 30.

In step 30, the determination result is transmitted from the image processing apparatus 11 to the computer 13, and the computer 1
Reference numeral 3 collates the judgment result with the print character data from the process control computer 15, and if there is no corresponding data, judges that there is an abnormality and outputs an alarm signal to the outside. As described above, the computer 13 finally collates the character determination result with the print character data, so that the reliability of the apparatus can be improved.

In addition to the letters, this device uses an alphabet,
Even a character string in which katakana and symbols are mixed can be read as long as its character shape, character spacing, printing direction, and character digit number are known in advance.

[0035]

As described in detail above, according to the character reading device and the reading method of the present invention, a character string printed on an object is photographed and only the character string is binarized from the photographed image. By determining the threshold level of the binarization according to the temperature of the object at the time of extraction, it is possible to determine whether the video signal of the character string printed on the object having an indefinite temperature is binarized. Since it is optimized, it automatically responds to the difference in heating state (temperature), it is possible to read the character string accurately, the distinguishability in character recognition is improved, and it is possible to machine on the end surface of steel materials. Work efficiency is improved because a resident operator for reading characters painted on the formula is unnecessary. From the above, the effect of the present invention is great.

[Brief description of drawings]

FIG. 1 is a device configuration diagram illustrating an embodiment of a character reading device according to the present invention.

FIG. 2 is a configuration diagram of an image processing apparatus for executing an image processing algorithm.

FIG. 3 is a processing flow for determining a threshold level for binarizing an image captured by an industrial camera and adjusting the positions of the industrial camera 1 and an illumination device.

FIG. 4 is a processing flow of a character reading algorithm.

FIG. 5 is a graph showing a correspondence between a steel material temperature and an optimum threshold level for binarization.

FIG. 6 is an explanatory perspective view showing a relationship between characters and a shooting field.

FIG. 7 is a diagram showing luminance levels projected in the X-axis and Z-axis directions for explaining a method of detecting the position of a character string on the end surface of a steel material.

FIG. 8 is a diagram showing luminance levels projected in the X-axis and Y-axis directions for explaining a method of detecting the position of a character string on the end surface of a steel material.

FIG. 9 is a schematic side view showing a positional relationship between an industrial camera and a lighting device with respect to a steel material.

FIG. 10 is a front view showing an initial window circumscribing a character string to be discriminated.

FIG. 11A is an explanatory diagram showing the width correction amount of the initial window when the left end of the character string to be discriminated is “1”;
(B) is an explanatory view showing the width correction amount of the initial window when the right end of the character string to be discriminated is "1", and (c) is the initial window when the left and right ends of the character string to be discriminated are "1". It is explanatory drawing which shows the horizontal correction amount of.

FIG. 12 (a), (b), (c), (d), (e).
FIG. 4 is an explanatory diagram showing a setting position of a discrimination window for one character of a character string to be discriminated.

[Explanation of symbols]

 1 Industrial Camera 2 Steel 2a End Face 3, 4, 5 Traverser 6 Radiation Thermometer 7 Lighting Device 8 Traverser 9 Industrial Camera 10 Character String 11 Image Processing Device 13 Computer 14 Traverse Controller 15 Process Control Computer 17 Signal Switching Unit 18 2 Quantization circuit 19 CPU 20 Program memory 21 Display device 22 Input / output interface 24, 25 Shooting field of industrial camera

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiko Miyazaki 46-59 Nakahara, Tobata-ku, Kitakyushu City Nippon Steel Plant Design Co., Ltd. (72) Inventor Masaharu Ono No. 1 Tobata-cho, Kitakyushu Steel Works Yawata Works (72) Inventor Tatsumasa Satomi 1-1, Hibahata-cho, Tobata-ku, Kitakyushu City Nippon Steel Co., Ltd. Yawata Works

Claims (3)

[Claims] 1. A camera for photographing a character printed on an object whose surface temperature state is indefinite, a character portion is extracted as binary data from an image photographed by the camera, and the character is extracted by a predetermined algorithm. A character reading device having a processing device for determining, which has a temperature sensor for measuring a surface temperature of the object, and is a binary value when the processing device extracts a character portion from the image as binary data. A character reading device, wherein a threshold level of conversion is determined according to a surface temperature of the object. 2. A measuring means for measuring a distance between the character printing surface and a camera for photographing the printing surface and a distance between the character printing surface and an illuminating means for the printing surface, and a measurement result of the measuring means. 2. The character reading device according to claim 1, further comprising a conveying unit that moves the camera and the illuminating unit to an optimum photographing position with respect to the print surface based on the above. 3. A character printed on an object whose surface temperature is indefinite is photographed, and a character portion is photographed from the photographed image.
In the character reading method for extracting the character data from the image as binary data, the threshold level of binarization is used as the surface temperature of the object. A method for reading characters, which is determined according to the method.