JPH042869A - Method for inspecting fabric of continuous length - Google Patents

Abstract

PURPOSE:To accurately and quantitatively sense defects present in a material to be tested by illuminating a running material of continuous length with a pale fluorescent lamp, sensing the reflected light or transmitted light with a color sensor and using a G or B output in an RGB output thereof. CONSTITUTION:A material of continuous length to be tested such as a fiber structure such as a woven or knit fabric or nonwoven fabric or filmy material is run through a roller system and the central part of two feed rollers 2 is simultaneously illuminated with a pale fluorescent lamp. The reflected light is then sensed with a color linear sensor 4. A G output or B output in an RGB output from the above-mentioned color linear sensor 4 is passed through a shading correction circuit 5 and a gamma correction circuit 6 and then inputted to a discriminating and displaying part 7. Thereby, defects such as stain, crease, fouling, flaw, unevenness or pulled yarn present in the aforementioned material to be tested are sensed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fabric inspection method for detecting defects inherent in a long structure, for example, a fibrous structure such as a woven fabric, a knit, a nonwoven fabric, or a film-like object. More specifically, the present invention relates to a fabric inspection method for detecting defects caused by optical density modulation or defects that cause optical density modulation in the fiber structure or film-like material. More specifically,
Examples of defects targeted by the present invention include, but are not limited to, "stains,""wrinkles,""dirt," and "
Fading,” “Scratch,” “Protrusion,” “Blurred,” “Dia,” “Dent,” “Cloudy,” “Foreign object,” “Uneven color.”
Examples include ``Kissugeki,''``Pockmark,''``Crater,''``Tsuriito,'' and ``Weaving unevenness.''

(Prior Art) Conventionally, inspection of defects inherent in these fibrous structures or film-like materials has relied entirely on the visual or tactile sense of an expert.

Detection of the presence of a defect by a skilled person is not simply based on the results obtained by observing the object to be inspected from a certain direction. Although it is extremely difficult to quantify or even explain qualitatively, it is known that humans recognize events based on extremely multidimensional information. This also applies to defect detection, and the recognition of a defect is the result of observing the object to be inspected from many different angles.

For example, when inspecting an object to be inspected while continuously transporting it, humans may be able to recognize defects simply by looking at the image of the object at a certain moment, according to their sense of vision. Instead, defects are detected from the subtle movements of the image that continuously change from moment to moment due to vibrations caused by transportation, fluctuations in lighting, and other factors.

As mentioned above, the mechanism by which human senses detect defects is astonishing and even mysterious.

However, while humans have excellent judgment, recognition, and discrimination abilities, human visual and tactile inspection requires skill on the part of those conducting the inspection, and is not always efficient and accurate. That cannot be said. These problems are fatal when inspecting fibrous structures or film-like products that are produced in large quantities using a large number of production machines. Especially in fiber structures, even normal parts have extremely complex structures, and detecting defects is based on this complex structure, or in other words, "variations", as well as other disturbance noise, etc. The task is to extract particularly large deviations, taking into account the influence of However, even with the eyes of an experienced expert, it is virtually impossible to constantly inspect many fiber structures with a constant standard.

In recent years, COD sensors have become available at low cost as solid-state video devices to replace image pickup tubes, and with the development of signal processing technology and image processing technology, these sensory systems that have traditionally relied on human vision have become less expensive. Many attempts are being made to replace conventional inspections with machines.

However, as mentioned above, compared to humans who make comprehensive judgments, recognition, and identification based on multifaceted information, the information obtained when observing an object with a machine, such as an optical sensor, is , it is literally just the result of observing the object to be inspected from one side, and the amount of information obtained is extremely small.

With the current signal processing technology and computer image processing technology, it is not possible to automatically make advanced judgments such as defect detection in real time from such a small amount of information using a machine within a practical range and in real time. However, it is extremely difficult.

(Problems to be Solved by the Invention) In other words, in the conventional defect detection that relies on the visual or tactile sense of an expert, the person performing the inspection requires skill, and it is not always efficient and accurate. This cannot be said to be sufficient, and problems remain in terms of reproducibility, etc. In addition, as far as practical inspection equipment is concerned, there is still no one that can be used at a level that satisfies the needs of practical use, with regard to fabric inspection equipment that automatically performs defect detection mechanically in real time.

As a result, even though the efficiency and accuracy are not necessarily sufficient, and there are still problems with reproducibility, inspections still rely on the eyes of experts.
This is a real sign that it is being carried out.

In recent years, it has become possible to stabilize the quality of industrial products at a high level through thorough QCl, or quality control. I can't hide my surprise at how well quality control has been carried out.

In view of this situation, the present inventors have conducted extensive research, and as a result,
We have achieved the next invention related to a method for detecting wrinkles with good reproducibility and with a certain standard.

(Means for Solving the Problems) That is, the present invention provides a method for detecting defects inherent in a long structure by conveying the long structure continuously or intermittently. Illuminated with fluorescent lights,
A color sensor detects reflected light or transmitted light from the elongated structure due to the illumination, and defects are detected using the G output or B output of the RGB output of the color sensor. This is a method for inspecting structures.

The present invention illuminates the fibrous structure or film-like object in a part of a roller system that continuously conveys the fibrous structure or film-like object to be inspected. The objective is to detect defects by observing the optical density modulation due to inherent defects using a color sensor.

The present invention is first characterized by a method of illuminating a fibrous structure or a film-like object to be inspected. That is, as a means for illuminating the fiber structure or film-like object, a "blue-white fluorescent lamp", that is, a lighting device that emits a wavelength distribution particularly extending toward the short wavelength side is used.

Regarding the position where the illumination means is provided in the present invention,
Although not particularly limited, it is preferable to provide it in a direction perpendicular to the object to be inspected. However, this is not the case especially when the focus is on detecting a specific type of defect.
For example, it may be preferable that the center of the device for illuminating the fibrous structure or film is positioned at an angle of 0 to 15 degrees from the horizontal direction of the fibrous structure or film to be inspected. . Preferably, the illumination means in the present invention should be arranged so that illumination means from a plurality of directions can be switched or used in combination as necessary.

Another feature of the present invention is the means for optically observing fiber structures or film-like objects. That is, a color sensor is used as a means for optical observation, and furthermore, the G output or B output of the RGB output of the color sensor is used.

As a color sensor, color image pickup tube, color COD
, a color line sensor, etc. can be used.

In the present invention, in order to increase the ability to detect defects, it is also possible to use a method of detecting defects by applying a threshold after performing shading correction and γ (gamma) correction on the signal output of the sensor. In this case, a method may be used in which the γ (gamma) correction level and threshold level are set for each object to be inspected, depending on the color tone, surface appearance, etc. of the object to be inspected. In addition, by installing multiple sensors in the direction of fabric conveyance and calculating the "sum" of the signal portions corresponding to the same location on the inspected object detected by the multiple sensors, noise can be canceled out and defects detected. It is also possible to perform signal processing such as emphasizing signals caused by.

(Function) The defects that the present invention attempts to detect in the object to be inspected, that is, fiber structures such as woven fabrics, knits, nonwoven fabrics, or film-like objects, are defects caused by optical density modulation. , or a defect that results in a modulation of optical density.

Especially in fiber structures, these are ``particularly large deviations'' among the ``variations'' among objects that have extremely complex structures even in normal parts, in other words, Furthermore, it is necessary to take into account the influence of other disturbance noises, etc., and when considering automatic detection by a machine, some kind of filtering and enhancement are essential.

The "blue-white fluorescent lamp" used as the illumination means in the present invention has a color rendering effect that emphasizes the short wavelength side of object light, and as is well known from color sensors,
Although it is possible to obtain an image signal separated into RGB colors, the G output or B output in particular has a filter effect that is sensitive only to relatively short wavelengths.

The present invention is based on the discovery that, among the filtering and enhancement methods described above, an excellent defect detection effect is particularly achieved by a combination of these two methods.

EXAMPLES The present invention will be explained in more detail by way of Examples below, but the present invention is not limited thereto.

(Examples) Example 1 FIG. 1 is a schematic explanatory diagram showing a detection portion of a fabric inspection device used in the present invention. As shown in the figure, two feed rollers are installed as part of the roller system that continuously conveys the fibrous structure or film-like object to be inspected. This method illuminates the object, observes the fiber structure or film-like object using a color linear sensor, and detects defects.

A blue-white fluorescent lamp with a power consumption of 100 W is used for illumination, and the blue-white fluorescent lamp is provided at a position perpendicular to the center of the object to be inspected.

The roller width was 190 cm1, and the feeding speed of the fibrous structure or film material was variable between 0 and 75 m/min by controlling the drive motor of the conveying system with an inverter.

Among the outputs of the color linear sensor, the signal obtained from the B output is binarized by a predetermined threshold after passing through a shading correction circuit and a γ (gamma) correction circuit.
The presence or absence of defects is determined.

FIG. 2 is an example of a signal obtained from a normal part without defects when the object to be inspected is a plain fabric. You can see noise components unique to textiles.

Figure 3 shows a defect. In this case, this is an example of a signal obtained from a location where there is a "stain". Changes in the concentration of the inspected object due to defects are very clearly captured, and there is no problem in detecting defects even in the noise peculiar to textiles.

FIG. 4 shows the spectral spectrum of illumination light obtained from a blue-white fluorescent lamp, and FIG. 5 shows the spectral sensitivity curve of the color linear sensor. By comparing the spectral sensitivity curves of the spectral spectrum of a blue-white fluorescent lamp and the G output or B output of a color linear sensor, it can be seen that the combination of the two is an excellent method for filtering and enhancing defect signals.

Average conveyance speed 5 for plain cloth with a total length of 5000 m
Defects were detected separately at 0 m/min using this fabric inspection device and by a skilled inspector. The fabrics used in the tests are repeatedly and carefully inspected by multiple experienced inspectors, and defects are mapped out. Now, the defect detection rate of fabric inspection equipment is 97%, and the defect detection rate of skilled inspectors is 97%.
It was 2%. The position of the detected defect at least roughly matched the obtained defect map.

Example 2 Using the same device as Example 1, the G of the color linear sensor was
The following test was conducted in the same manner as in Example 1 using the output. The defect detection rate in this case was 98%.

Comparative Example Using the same device as in Example 1, R of the color linear sensor was
The following test was conducted in the same manner as in Example 1 using the output. The defect detection rate in this case was only 46%, and it was judged that it was not of practical use.

(Effects of the invention) According to the present invention, compared to human visual inspection, it does not require skill and is superior in terms of efficiency and accuracy, and it is also possible to quantitatively determine judgment criteria. .

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of a fabric inspection device according to the present invention. FIG. 2 is an example of a signal obtained from a defect-free portion in Example 1. FIG. 3 is an example of a signal obtained from a defective portion in the first embodiment. FIG. 4 is a spectrum of the blue-white fluorescent lamp used in Example 1. FIG. 5 is a spectral sensitivity curve of the color linear sensor used in Example 1. ■Fibre structure or film-like object ■Feed roller ■Blue-white fluorescent lamp ■Color linear sensor ■Shading correction circuit ■Gamma correction circuit ■Judgment and display section ■R output terminal ■G output terminal @lB output terminal Arrow: Stained part

Claims (1)

[Claims] (1) In a method for detecting defects inherent in a long structure by conveying the long structure continuously or intermittently, the long structure is illuminated with a blue-white fluorescent lamp, and the length of the long structure is illuminated by the illumination. Inspection of a long structure, characterized in that reflected light or transmitted light from the long structure is detected by a color sensor, and defects are detected using the G output or B output of the RGB output of the color sensor. Method.