JPH0777501A - Red rust area detection method for steel plate - Google Patents

Abstract

PURPOSE:To provide a method for detecting the read rust area of a test piece in the corrosion test, e.g. salt water spray test or cycle corrosion test, for a steel plate or a surface treated steel plate. CONSTITUTION:The method for detecting the red rust area on a steel plate comprises a color TV camera 3 for picking the surface image of a steel plate 2 having red rust areas, a specific color extraction unit 5 for receiving a color image signal from the color TV camera 3 to produce a binary image signal comprising a white color signal representative of the color inherent to the red rust and a black color signal representative of other colors, a frame memory 6 for temporarily storing a digital binary image signal comprising [1] representative of white part and [0] representative of black part obtained by subjecting the binary image signal to A/D conversion, and a unit for counting the number of pixels only in the white [1] part in the frame memory 6 and conducting an operation; {the number of pixels in the white [1] part}/(the number of pixels in the white part [1]+ the number of pixels in the block part [0]}X100.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corrosion evaluation of a steel plate or a surface-treated steel plate, and provides a method for detecting a red rust area of a test piece subjected to a corrosion test, for example.

[0002]

2. Description of the Related Art In recent years, market demand for corrosion resistance of products has increased for steel sheets for automobiles, home appliances and building materials, and research and development of new products in response to this has been actively conducted. Therefore, the weight of the corrosion resistance evaluation of steel sheets in development research is extremely high.

The corrosion resistance of a steel sheet is evaluated by measuring the area of rust generated on a test piece that has been subjected to a corrosion test such as an exposure test and an accelerated test, which depends on the manual work of a skilled person. Therefore, an automatic identification method based on color has been conventionally studied.

As a conventional device for automatically identifying a color, for example, Japanese Patent Laid-Open No. 62-291522 and Japanese Patent Laid-Open No. 6-291522.
The thing disclosed by the 3-200027 publication is known. In these conventional devices, a color TV camera to an R
By extracting three signals separated into (red), G (green) and B (blue) and processing these signals by a complicated digital processing circuit, the color of the imaging target can be identified with high accuracy. There is. However, in the case of identifying a color based on each signal of RGB three colors, at least three circuits for comparing the signal levels are required, and the circuit configuration becomes complicated. Moreover, when three systems of comparison circuits are provided, it is necessary to adjust the threshold values of the three sets of circuits, and therefore, in order to adjust those threshold values to a specific substance, the threshold value adjustment operation is performed. Need a specialist with special knowledge and experience.

[0005]

SUMMARY OF THE INVENTION The present invention is intended to realize that anyone can automatically, easily, and accurately detect the red rust generation area of a steel sheet having red rust.

[0006]

In order to solve the above problems, the present invention provides a color television camera for photographing a steel plate surface having red rust on the surface, and a unique color possessed by red rust upon receiving a color video signal from the color television camera. An intrinsic color extraction device that uses white and the other colors as black to obtain a binary image signal, and a digital conversion of the binary image signal by analog / digital conversion, where the white part is [1] and the black part is [0] digital. While calculating the number of pixels only in the image memory that is temporarily recorded as a binary image signal and the white [1] portion in the image memory, {the number of pixels in the portion that becomes 1 / (1 The present invention has led to the invention of a method for detecting the area ratio of red rusted portion of a steel sheet, which comprises: an arithmetic unit for performing the following calculation:

[0007]

[Function] The inventors have found that the color (hue) of red rust generated on the steel sheet.
However, paying attention to the fact that it is in a relatively narrow specific hue range,
In order to automatically identify this specific hue, a method of identifying only red rust by photographing the object to be detected using a color imaging means such as a color television camera and detecting the hue from the obtained video signal. Proposed. Therefore, based on this, in the present invention, a color image pickup means for outputting information of a color image obtained by picking up a steel plate having red rust on the surface as a signal of NTSC standard format, and a signal outputted by the color image pickup means are RGB signals. An NTSC-> RGB decoder, an intrinsic color extraction device for extracting the intrinsic hue of red rust from the RGB signals and binarizing it, and a frame memory for temporarily taking in the binarized image signal as a digital image signal, and 2. Calculate only the number of pixels corresponding to the red rust part in the binarized image, take the ratio with the number of pixels corresponding to the entire steel plate,
An area ratio calculation device for calculating the red rust area ratio is provided.

The video equipment used in Japan and the United States is NTS.
The C standard is often adopted, and a sync signal, a luminance signal (Y signal) and a chroma signal are superimposed on an NTSC standard video signal that is standardly output from a color television camera. The chroma signal is composed of an I signal and a Q signal that are amplitude-modulated by subcarriers of the same frequency (about 3.58 MHz) whose phases are different from each other by 90 degrees. The I signal is a color difference signal in the red-blue-green axial direction, and the Q signal is a color difference signal in the yellow-green-violet axial direction which is orthogonal thereto, and the hue of the image is represented by the two color difference signals I and Q. ing.

Therefore, in the present invention, the I signal and the Q signal are extracted from the NTSC signal, and their level ratio (Q / Q
I) is calculated and this ratio is compared with predetermined upper and lower levels to identify whether it is within the upper and lower levels. Since the level ratio Q / I corresponds to the hue of the image, by setting the upper limit level and the lower limit level so that they substantially match the hue of the substance to be detected, a binary signal indicating the presence or absence of the substance to be detected can be obtained. can get. In this case, the unique color of red rust is white, and the other colors are black, and the binary image signal is used. A new video signal is obtained by synthesizing the binary signal and the sync signal separated in advance. If this video signal is applied as it is to the input terminal of, for example, a monitor TV, a video in which the presence or absence of the substance to be detected is binary-valued can be seen on the two-dimensional image. By referring to this image, that is, the red rust extracted image, and comparing it with the substance actually photographed, it is possible to immediately know whether the recognition result is correct,
The upper limit level and the lower limit level are the desired substances (red rust)
It is extremely easy to adjust so that only one is recognized. Further, the binarized image signal is converted from analog to digital and the white portion (red rust portion) is set to [1] and the black portion (portion other than red rust) is set to [0]. The area of the red rust portion can be calculated.

[0010]

EXAMPLE FIG. 1 shows the structure of a red rust area ratio detecting device for steel sheets. The surface of the steel plate 2 having red rust on the surface illuminated by the lighting device 1 is imaged by the color television camera 3. The output video signal of the color television camera 3 is set to

As described in the above section, by separating the I and Q signals from the macro signal of the NTSC image signal to calculate Q / I and binarizing the target color setting value of 4 as a threshold value. A digital image is stored in the frame memory 6 as a binary image signal (white [1] for the red rust part and black [0] for the other part) in which only the unique hue of rust is extracted by the unique color extraction device 5 for extracting the unique color. The extracted image is displayed on the monitor 8 while being temporarily stored as a signal. The value stored in the frame memory 6 is read by the personal computer 7, the number of pixels of only the portion marked with [1] is calculated, and the ratio to the number of pixels corresponding to the entire steel plate is taken to obtain red rust in the steel plate. Calculate the area ratio occupied by. The calculated result is printed and recorded by the printer 9. A program for automatically performing these operations is read from the disk storage device 10 and executed.

[0011]

According to this method, since the unique color having red rust is identified as the hue, it is not affected by the change in brightness due to the unevenness of the illumination, etc. It is possible to identify. The present invention as described above, anyone can automatically, easily, accurately measure the red rust occurrence area of the steel sheet after the corrosion test,
It has a great effect on rapid development research.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a red rust portion area ratio detection apparatus for a steel plate which is an embodiment of the present invention.

[Explanation of symbols]

 1 Lighting Device 2 Steel Plate 3 Color TV Camera 4 Binarization Processing Device 5 Unique Color Extraction Device 6 Frame Memory 7 Personal Computer 8 Monitor 9 Printer 10 Storage Device

Claims (1)

[Claims] 1. A color television camera for photographing the surface of a steel plate having red rust on the surface, and a binarized image in which the color unique to red rust is white and the other colors are black when receiving a color video signal from the color television camera. An intrinsic color extraction device for use as a signal, and 2
An image memory that temporarily converts the binarized image signal into a digital binarized image signal having a white part [1] and a black part [0] by analog / digital conversion, and a white [1] in the image memory. ] And an arithmetic unit for calculating the number of pixels of only the portion where [1] / (the number of pixels of 1 / (the number of pixels that have become 1 + the number of pixels that have become 0)) × 100 The method for detecting the area ratio of red rusted portion of a steel sheet is then performed.