JPH0627716B2 - Non-woven fabric defect detector - Google Patents

Description

TECHNICAL FIELD The present invention relates to an apparatus for detecting defects scattered in a sheet-like nonwoven fabric that is translucent and has a white background.

[Conventional technology]

Due to its thinness, defects such as stains, wrinkles, and holes that occur in the production of translucent non-woven fabrics are currently artificially detected in the inspection process. In other words, inspection workers can detect defects by visually inspecting the surface of a running sheet of non-woven fabric, and partially remove or mark the detected defects. I am taking measures. However, in such a conventional method, the fatigue of the inspection worker is large, and the detection field of view is also limited, and the uniformity of defect detection is poor, and the running speed of the nonwoven fabric must be limited to a low level. Since it had to be done, a lot of detection time was required.

Therefore, the present inventor illuminates the surface of the transparent non-woven fabric with a lighting device having a tungsten bulb as a light source in order to automate the defect detection, and a solid-state sensor camera having a solid-state image sensor for photoelectrically converting the reflected light. We have developed a defect detection method of the reflected light receiving type, which monitors the non-woven fabric by receiving light at, and processes the obtained signal with an electronic circuit to determine whether or not there is a defect. Further, as another method, by illuminating from the back surface of the translucent non-woven fabric with a lighting device using a tungsten bulb as a light source, and by receiving light with a solid-state sensor camera having a solid-state image sensor for photoelectrically converting the transmitted light of the non-woven fabric. We have developed a transmitted light receiving type defect detection method that monitors and processes the obtained signal with an electronic circuit to determine whether or not there is a defect.

[Problems to be solved by the invention]

However, since the translucent non-woven fabric has a structure in which countless short fibers such as polyester and rayon are bound together in a turbulent state, the formation density is unique. Therefore, the S / N ratio between the unevenness of the non-woven fabric and the defects such as stains scattered on the non-woven fabric is low. Therefore, in any of the above conventional defect detection, in the case of a clear defect such as a black defect in a white ground system, the defect determination circuit connected to the detector can accurately determine as a defect, With respect to defect stains having a low gray gradation such as light gray and brown, it is extremely difficult to discriminate by the discriminating circuit, and there is a problem that the detection accuracy is poor and it is not suitable for practical use.

[Means for solving problems]

The present invention is, while running, translucent and on one side of a white fabric type sheet-like nonwoven fabric, which is arranged with a separation distance of 50 mm or less from this one surface, and has the same gray scale as the gray gradation of the nonwoven fabric. A reflector of the furniture, a lighting device which is disposed on the other side of the non-woven fabric and uses a tungsten bulb as a light source, and a reflector which is disposed on the other side of the non-woven fabric and the light reflected on the one side of the non-woven fabric A solid-state sensor camera provided with a solid-state image sensor that receives the reflected light that has been transmitted through the non-woven fabric again and undergoes photoelectric conversion, and an infrared absorption filter provided in the incident optical path of the camera. .

[Action]

The defect detection apparatus of the present invention having the above-mentioned solving means is configured to reflect the illumination light transmitted through the non-woven fabric and transmit it to the non-woven fabric again by a reflector having a gray gray scale that is substantially the same as that of the white fabric non-woven fabric. As a result, apparent unevenness of the texture of the non-woven fabric seen from the solid-state sensor camera is eliminated, and the texture density is made uniform. Then, under the above conditions, the solid-state sensor camera simultaneously receives the reflected light from the nonwoven fabric. Moreover, the near-infrared wavelength range of the radiant energy, which is extremely strong in the illumination light from the lighting device using the tungsten bulb as the light source, substantially overlaps with the wavelength range in which the sensitivity characteristic of the solid-state image sensor of the solid-state sensor camera is the highest. Despite this, the wavelength light in the near-infrared region of the reflected light from the white fabric type non-woven fabric,
The infrared absorption filter can prevent the solid-state imaging device from receiving light, and can prevent the near-infrared wavelength light from causing noise. Furthermore, since the reflector does not come into contact with the running non-woven fabric, the reflector is not damaged by contact with the non-woven fabric and is not heated to accelerate discoloration, and is also charged with static electricity to promote dust adhesion. Without incident,
The predetermined reflection characteristics of the reflector can be maintained. Moreover, since the reflector is arranged with a separation distance of 50 mm or less with respect to the non-woven fabric, it is possible to secure a necessary and sufficient amount of incident light to the sensor camera of the reflected light reflected by the reflector and transmitted through the non-woven fabric again. Therefore, it is possible to prevent the formation density from becoming ununiform. In addition, the shadow of the nonwoven fabric reaching the reflecting surface of the reflector can be greatly attenuated, and even if the solid sensor camera receives a shadow that is thinned by this attenuation, it can be prevented from causing noise. Therefore, it is possible to obtain a signal having a high S / N ratio between the defect stain and the like and the texture of the non-woven fabric with the solid-state sensor camera, and improve the defect detection accuracy.

〔Example〕

The present invention is installed, for example, in a place where a test process is performed. In FIG. 1 to FIG. 3, reference numeral 1 denotes a translucent, white-textured sheet made of polyester, rayon or the like. The take-up reel 3 around which the non-woven fabric 2 is wound is taken up, 3 is a take-up reel for taking up the non-woven fabric 2 taken out from the take-up reel 1 and passed through the tension roller 4, and 5 are guide rollers. The take-up reel 3 is rotated by a drive device (not shown), and the power from this device is arbitrarily transmitted by an operator 7 operating an operation panel 6 provided near the take-up reel 3. It is designed to be used. Further, the operation panel 6 is provided with a reporting means 8 such as a buzzer or a voice phonograph which is operated in accordance with the defect detection described below.

A monitoring unit of the defect detection device is provided on a part of the traveling path of the nonwoven fabric 2. This monitoring unit is a lighting device 9
And a solid-state sensor camera 10, a reflector 11, and an infrared absorption filter 12.

A solid-state sensor camera 10, which uses a tungsten light source as a light source, is used as the lighting device 9. For example, a linear array line image sensor or an area array image sensor is provided in the camera body 10a as shown in FIG. The solid-state image pickup device 10b is provided as a photoelectric conversion device, and the image pickup lens unit 10 for forming an image on the device 10b is formed.
It is formed by attaching c to the body 10a. The lighting fixture 9 and the solid-state sensor camera 10 are respectively arranged on the front surface side of the nonwoven fabric 2, and the solid-state sensor camera receives the reflected light A projected from the lighting fixture 9 and reflected by the surface of the nonwoven fabric 2. 10 receives light.

The infrared absorption filter 12 has an IRA-20 or I
A filter such as RA-25 is used, which is provided in the incident light path to the solid-state sensor camera 10. In the present embodiment, the case where the lens unit 10c is attached not in the incident light path before reflection or transmission from the lighting fixture 9 to the nonwoven fabric 2 but in the incident light path after reflection or transmission from the nonwoven fabric 2 to the solid-state sensor camera 10. Is shown.

Further, the reflector 11 is longer than the width of the nonwoven fabric 2 and is arranged on the back surface side of the nonwoven fabric 2. The reflector 11 has a gray gradation of about the same as the gray gradation of the nonwoven fabric 2. Note that this embodiment is an example in which the background color of the non-woven fabric 2 is similar to that of the non-woven fabric 2, and the reflector 11 has a white coating that reflects and scatters incident light. Moreover, in this embodiment, the reflector 11 has a flat plate shape. Further, the reflector 11 is arranged in non-contact with the back surface of the non-woven fabric 2, that is, at a distance B within 50 mm from the non-woven fabric 2. The first reason is that the reflector 11 does not come into contact with the running non-woven fabric 2, so that the reflector 11 is prevented from being damaged by contact with the non-woven fabric 2 or being discolored due to heat. This is to prevent the adhesion of dust to the reflecting surface of the reflector 11 due to being charged with static electricity, so that the cause of noise does not occur in the reflector 11 itself and the predetermined reflection characteristic can be maintained. The second reason is that by arranging the reflectors 11 with a separation distance of 50 mm or less, the necessary and sufficient amount of incident light to the solid-state sensor camera 10 of the reflected light reflected by the reflectors 11 and transmitted through the nonwoven fabric 2 again. Is to prevent the formation density from being unbalanced and according to the result of the experiment, when the distance is 50 mm or more,
It was found that the apparent disappearance of the texture unevenness of the nonwoven fabric 2 as seen from the solid-state sensor camera 10 cannot be expected to have an effect suitable for practical use. Furthermore, the third reason is that the shadow of the nonwoven fabric 2 that reaches the reflecting surface of the reflecting plate 11 due to the illumination can be greatly attenuated, and the shadow thinned by this attenuation does not cause noise. And the reflector 11
Of the illumination light projected from the lighting fixture 9 reflects the light C transmitted through the non-woven fabric 2 and retransmits it to the non-woven fabric 2. The transmitted and reflected light is the solid-state sensor camera 1 described above.
0 receives light.

Further, reference numeral 13 in FIG. 3 is a defect discriminating circuit constituted by an electronic circuit, and the defect detecting device is constituted by including the circuit 13 and the monitoring section, and the circuit 13 includes a solid-state sensor camera. It is connected to 10 output terminals. One of the output terminals of the defect discriminating circuit 13 is connected to the operation panel 6, and when the defect is discriminated, the notification means 8 of the operation panel 6 is operated. Reference numeral 14 in the figure denotes a guide roller that guides the running of the nonwoven fabric 2 by preventing the nonwoven fabric from fluttering.

When the defect detecting device is operated in the above configuration, the surface of the running nonwoven fabric 2 is illuminated by turning on the lighting fixture 9, and a part of the surface is reflected by the surface of the nonwoven fabric 2. At the same time, since the non-woven fabric 2 has a light-transmitting property, a part of the illumination light passes through the non-woven fabric 2 and reaches the reflector 11, which is reflected by the reflector 11 to move the non-woven fabric 2 from the back surface side to the front side. Is transmitted again. Therefore, the non-woven fabric 2 is used for the reflector 11.
Solid-state sensor camera 1 arranged on the same side with the boundary
0 receives the reflected light A and the transmitted light C. By the way, since the reflector 11 has substantially the same gray gradation as the nonwoven fabric 2, the transmitted light C reflected by the reflector 11 is received by the solid-state image sensor 10b of the solid-state sensor camera 10 through the infrared absorption filter 12. By doing so, the apparent unevenness of the texture of the nonwoven fabric 2 viewed from the solid-state sensor camera 10 disappears, and the texture density is made uniform. Since the solid-state sensor camera 10 receives the reflected light A as described above under such a condition, the defect is emphasized with respect to the texture of the nonwoven fabric 2 after all. In other words, not only clear stains such as black stains scattered on the white non-woven fabric 2 but also defect stain colors such as light gray and brown with a low gray gradation degree have an S / N ratio with the texture of the nonwoven fabric 2. A high detection signal can be obtained by photoelectric conversion in the solid-state image sensor 10b.

Moreover, the luminaire 9 used in this device uses a tungsten bulb as a light source, but the wavelength characteristic of its radiant energy has very strong radiant energy in the near infrared region as shown in FIG. Sensor camera 1
Solid-state image sensor 10b made of an image sensor used for
As shown in Fig. 4, the sensitivity characteristic of is 800 than the visible range.
It has the highest sensitivity peak in the near infrared region near nm. When the strongest radiant energy of the luminaire 9 and the highest sensitivity peak of the solid-state image pickup device 10b are substantially overlapped with each other in this manner, when the solid-state image pickup device 10b receives light in the entire wavelength range of the tungsten bulb, The present inventor has confirmed that wavelengths in the near infrared region cause noise. Therefore, as described above, the infrared absorption filter 12 is provided in the incident optical path to the solid-state sensor camera 10. The characteristics of this filter 12 are shown in FIG. 6, the characteristics shown by the solid line in FIG. 6 are those of IRA-20, the characteristics shown by the dotted line are those of IRA-25, and the characteristics shown by the one-dot chain line are IRA-10. Therefore, the filter 12 can cut the harmful near-infrared wavelength that causes noise as described above, and the reflected light A and the transmitted reflected light C can be received by the solid-state imaging device 10b.

That is, while preventing noise generation based on the characteristics of the light source of the lighting fixture 9 and the solid-state image sensor 10b as described above, the formation density as described above can be averaged.
A remarkably high S / N ratio can be obtained, and the subsequent detection processing in the defect determination circuit 13 can be facilitated, defect overlooking can be prevented, and detection accuracy can be significantly improved.

Further, based on the above-described defect detection, the notification means 8 of the operation panel 6 is operated by the output from the defect determination circuit 13, and accordingly, the worker performs marking or cutting on the defective portion. Appropriate measures can be taken.

In addition, although the above-mentioned one embodiment is configured as described above, the color of the reflector 11 may be different from that of the non-woven fabric as long as the gray gradation is substantially the same.

Further, although the above-mentioned one embodiment shows the case where it is carried out in the inspection step, it may be carried out at the winding on the take-up reel in the manufacturing line. Then, in this case, the output from the defect discriminating circuit of the defect detecting device can be fed back to the manufacturing device side as an automatic control signal of the manufacturing line.

In addition, in carrying out the present invention, as long as it is within the scope of the invention, the positions of the lighting fixture, the solid-state sensor camera and its solid-state imaging device, the reflector, the infrared absorption filter, and the like with respect to the non-woven fabric, and specific members thereof It is needless to say that the structure, shape, material, etc. are not limited to the one embodiment described above and can be implemented in various modes.

〔The invention's effect〕

According to the present invention having the configuration described in the claims, the effect of uneven texture peculiar to the white fabric non-woven fabric is eliminated, and a solid-state image pickup device having a harmful wavelength causing noise is obtained. Can be prevented, and the scratches, discoloration, and adhesion of dust on the reflective surface of the reflector can be prevented.
Moreover, the influence of the shadow of the non-woven fabric can be reduced, and the S / N ratio can be significantly improved. As a result, not only clear defects with high gray gradation but also defects with low gray gradation such as light gray or brownish Can be accurately detected, and its accuracy is high.

[Brief description of drawings]

The drawings show one embodiment of the present invention, FIG. 1 is a partial side view, FIG. 2 is a side view of a solid-state sensor camera, FIG. 3 is a diagram schematically showing the entire configuration, and FIG. FIG. 5 is a diagram showing the spectral sensitivity characteristic of the solid-state image pickup device, FIG. 5 is a diagram showing the spectral characteristic of a tungsten electric bulb with a color temperature of 3000 K, and FIG. 6 is a diagram showing the spectral transmittance of various infrared absorption filters. 2 ... Nonwoven fabric, 9 ... Lighting equipment, 10 ... Solid-state sensor camera, 10b ... Solid-state image sensor, 11 ... Reflector, 12
...... Infrared absorption filter.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-56-22904 (JP, A) Jikkō 51-31899 (JP, Y2)

Claims (1)

[Claims] 1. A sheet-like non-woven fabric that is transparent and translucent while running, and is arranged on one side of the sheet-like non-woven fabric with a separation distance of 50 mm or less from the one face, and has a gray gradation substantially the same as the gray gradation of the non-woven fabric. A reflector having a gradation, a lighting device that is disposed on the other side of the non-woven fabric and uses a tungsten bulb as a light source, and a reflection device that is disposed on the other side of the non-woven fabric and the light reflected on the one side of the non-woven fabric Defective non-woven fabric including a solid-state sensor camera that has a fixed image sensor that receives the reflected light reflected by the body and transmitted through the non-woven fabric again, and performs photoelectric conversion, and an infrared absorption filter provided in the incident path of the camera. Detection device.