JPH06288712A - Edge detecting method - Google Patents

Abstract

PURPOSE:To provide an edge detecting method by which the edge position of an object can be specified easily even if the difference of a brightness level between the edge of the object and its surrounding is small. CONSTITUTION:Not only a simple difference between picture elements adjoining to each other but also a sum of brightness signal levels in a predetermined width (n pieces of picture elements) before and after each picture element are acquired and then, a difference is acquired between the sum of the brightness signal level on the front side and the sum of the brightness signal level on the rear side, and by considering a point where the value becomes the largest as the edge position of an object even if a difference in the brightness signal levels between the edge of the subject and its surrounding is small, the edge position of the object can be easily and accurately detected, and reliability on recognized shape and measured dimension of the object 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 detecting an edge of an object from a one-dimensional image taken by an image input device.

[0002]

2. Description of the Related Art Conventionally, in order to measure the shape, size, etc. of an object from a photographed image, a one-dimensional CCD camera has been used as an image input device, which is rocked to continuously photograph and process an image. Is disclosed, for example, in Japanese Patent Laid-Open No. 61-209305.

In such an apparatus, first, the edge of the object is detected from the brightness of the photographed image to recognize the shape, and the distance between the edges is calculated to obtain each dimension. For example, when the object is a red hot steel material that goes from the heating furnace to the rough rolling process, the difference in the output (brightness level) between adjacent pixels of the infrared image data captured by the image processing device is calculated from the initial coordinate to the final coordinate. Up to this point, the point at which this difference is the maximum is the start edge of the steel material, and the point at which this difference is the minimum (negative value) is the end edge.

However, when the temperature of the end of the steel material is low, there is a problem that it is difficult to specify the edge position because the temperature difference between the steel material and its surroundings is small and the emission luminance level at the edge portion rises gently. It was In particular, since the resolution of the captured image is increasing due to the recent development of CCD cameras, it is more difficult to specify the edge position only by looking at the difference in the brightness levels of the pixels adjacent to each other.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and its main purpose is to reduce the difference in brightness level between the edge of an object and its surroundings. However, it is to provide an edge detection method capable of easily specifying the edge position of an object.

[0006]

According to the present invention, such an object is a method for detecting an edge of a target object from a one-dimensional image including the target object, which is before and after each point along the scanning direction. The sum or integrated value of the luminance signal level of a predetermined width is obtained, and the difference between the sum or integrated value of the luminance signal level of the front side predetermined width and the sum or integrated value of the luminance signal level of the rear side predetermined width is obtained, and the difference is obtained. It is achieved by providing an edge detection method characterized in that the point at which is the maximum is the edge position of the object.

[0007]

As described above, after the sum of the luminance signal levels of a predetermined width (n pixels) before and after a certain pixel is obtained instead of the simple difference between adjacent pixels, the luminance signal level of the front side is calculated. The edge can be easily specified by obtaining the difference between the sum and the sum of the luminance signal levels on the rear side and setting the point having the maximum value as the edge position of the object.

At this time, if the difference between the brightness level of the object and the surrounding brightness level is large, n may be small. If the difference between the brightness levels is large, n may be increased according to the difference. The processing speed does not unnecessarily slow down.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a perspective view showing the configurations of an image input device and an image processing device to which the present invention is applied. A red-hot thick plate slab 2 is conveyed from the heating furnace to the rough rolling process on the conveyer conveyor 1 shown in FIG. 1. In order to obtain the dimensions of the thick plate slab 2, the thick plate slab 2 is slab. 2 is stopped at a predetermined position, and is photographed by a camera device 3 as an image input device arranged at a predetermined height above the transport roll 1, and the image signal of the thick plate slab 2 is sent to the image processing device 4. The image processing device 4 sends the image and performs image processing.

The camera device 3 is arranged, for example, at a height 21 m away from the thick plate slab 2 in a measuring chamber provided above the thick plate slab 2 in order to avoid the influence of heat from the thick plate slab 2. And a camera body 7 as an optical system member integrally attached to a drive motor 5 supported by a mount (not shown) and an oscillating plate 6 fixed to the drive shaft.
And the lens unit 8. The detection unit of the camera body 7 has a one-dimensional CC capable of measuring the range indicated by the solid line in the figure.
D is provided, and for the lens unit 8, for example, a zoom lens is used so that the initial adjustment can be easily performed at a long focus (for example, a focal length of 170 mm). Actually a one-dimensional CCD with 4096 pixels
Is used to set the resolution to 1.0 mm per pixel.

Then, the swing plate 6 is rotated by the drive motor 5, whereby the camera body 7 and the lens unit 8 are rotated.
Oscillates in the direction indicated by arrow A in the figure, and images of the slab 2 in the predetermined direction are input at predetermined pitches in the oscillating direction. At this time, the shooting image world becomes like an imaginary line. Although not shown, there is also a camera device in which the measuring direction and the swinging direction of the one-dimensional CCD are orthogonal to those shown in order to measure the length in the direction orthogonal to the scanning direction shown in FIG. It is provided.

In practice, a plurality of one-dimensional CCDs may be used in combination in order to secure the resolution, and the above areas may be divided and scanned by each CCD.

Next, the procedure for detecting the edge position of the thick plate slab 2 will be described.

In this embodiment, the number of pixels in the x direction is set to, for example, four.
096 pieces each, and the coordinates (x, y) are (0, 0)-(4
095, 499) (FIG. 2). The outline of the processing is as follows. With the y-direction coordinates in FIGS. 1 and 2 fixed, coordinates (0, Y) to coordinates (4095, Y), for a certain coordinates (X, Y), the coordinates (X , Y), the sum PF of the brightness levels of the n coordinates (predetermined width) on the front side in the x direction including
(X, Y) is obtained, and then x including the coordinates (X, Y)
The sum PR (X, Y) of the brightness levels of the n coordinates on the rear side in the direction is obtained, and the difference D between these PF (X, Y) and PR (X, Y) is calculated.
Find (X, Y). Similar processing is performed from the coordinate (0, Y) to the coordinate (4095, Y), and the maximum value of the absolute values of the difference D (X, Y) is the edge of the thick plate slab 2 at the y coordinate = Y. To judge. In addition, it is not necessary to actually perform the above process from the coordinates (0, Y) to the coordinates (4095, Y).

The processing procedure in this embodiment will be described below with reference to FIG.
This will be described with reference to the flowchart in FIG. First, when the image is captured in the image processing device 4 (step 1), first, the number of calculated pixels n to be described later is determined according to the average luminance level of the thick plate slab 2 (step 2).

Here, in this embodiment, when the average luminance level of the steel material is 70 or more (800 ° C. or more) of 256 floor length, the number of calculation pixels n is 4, and the average luminance level of the steel material is less than 70 (800 ° C.). N is 10. However, it goes without saying that the value of the number of calculated pixels n may actually be changed according to the color and environment of the steel material. Further, when performing scanning by CCD, a plurality of output amplifiers are often used, but the output value changes due to individual differences in each amplifier. For example, when two amplifiers are used, the amplifiers used are divided into odd-numbered pixels and even-numbered pixels, that is, the output value changes between odd-numbered pixels and even-numbered pixels. Therefore, by setting the number of calculation pixels n to the number of amplifiers or a multiple thereof, it is possible to eliminate the detection error due to the amplifiers, and it is possible to perform more accurate detection.

Next, the variable Y = 1 is set (step 3),
By shifting the value of X from the coordinates (0, Y) in the positive direction, the above PF (X, Y), PR (X, Y), D (X,
Y) is performed to obtain one edge (start edge) (step 4), then the value of X is shifted from (4095, Y) in the negative direction, and the above PF (X, Y), PR
The other edge (end edge) is obtained by performing processing for obtaining (X, Y) and D (X, Y). At this time, the start edge and the end edge are points where D (X, Y) becomes maximum.

As shown in FIG. 4, the maximum D (X,
The processing speed is improved by stopping the calculation at 200 pixels in the shift direction from Y). This 200 pixels is a changeable setting value. If this is shown by the formula,

[0020]

[Equation 1]

From the coordinates (0, Y) to the coordinates (409
The value of X is shifted in the positive direction in the (5, Y) direction, and one edge is obtained from the maximum value of D (X, Y) among them.

[0022]

[Equation 2]

The calculation of is performed by shifting the value of X from the coordinate (4095, Y) to the coordinate (0, Y) direction in the negative direction, and from the maximum value of D (X, Y) in the value, the other edge is calculated. Ask for. Next, the y coordinate is shifted by 1 (step 6), and the coordinates (0, Y + 1) to the coordinates (4095, Y +) are shifted.
The same processing is performed up to 1). In this way, y coordinate =
The above processing is repeated from 0 to 499 (step 4 to step 7) to obtain the edge of the thick plate slab 2 along the y direction.

When all the edges of the thick plate slab 2 along the y direction have been found, the X coordinate and the y coordinate are exchanged to find all the edges of the thick plate slab 2 along the X direction (steps 8 to 12), step 13 , 14 calculates the lengths of the thick plate slab 2 in the X and y directions, displays the results (step 15), stores the results, and ends the process.

In this embodiment, a CCD camera is used as the image input device to perform digital processing. However, a normal analog camera is used to replace the n pixels with a predetermined width and integrate the luminance signal. It goes without saying that it is also good.

[0026]

As described above, according to the edge detection method of the present invention, it is not a simple difference between pixels adjacent to each other, but a simple difference between pixels adjacent to each other. After obtaining the sum of the luminance signal levels of a predetermined width (n pixels), the difference between the sum of the front side luminance signal levels and the sum of the rear side luminance signal levels is obtained, and the point where the value is maximum is targeted. By setting the edge position of the object, the edge position of the object can be easily and reliably detected even if the difference in the luminance signal level between the edge of the object and its surroundings is small. , The reliability of each measurement dimension is improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing configurations of an image input device and an image processing device to which the present invention is applied.

2 is a plan view of the plank slab of FIG. 1. FIG.

FIG. 3 is a flowchart showing a procedure for detecting an edge of the thick plate slab of FIG.

FIG. 4 is an explanatory diagram showing calculation results.

[Explanation of symbols]

 1 Transport Roll 2 Thick Plate Slab 3 Camera Device 4 Image Processing Device 5 Drive Motor 6 Oscillating Plate 7 Camera Body 8 Lens Unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Fuminori Nakano 46-59 Nakahara, Tobata-ku, Kitakyushu City Nippon Steel Corporation Machinery & Plant Division

Claims (2)

[Claims] 1. A method for detecting an edge of an object from a one-dimensional image containing the object, wherein the sum or integrated value of brightness signal levels of a predetermined width before and after each point along the scanning direction is obtained and the front side is obtained. The difference between the sum or integrated value of the luminance signal level of a predetermined width and the sum or integrated value of the luminance signal level of the rear predetermined width is obtained, and the point where the difference is maximum is set as the edge position of the object. Characteristic edge detection method. 2. The edge detecting method according to claim 1, wherein the predetermined width is changed according to an average luminance signal level of the object.