JPH0221245A - Inspecting device for mesh-like object - Google Patents

Abstract

PURPOSE:To detect a mass defect and an omission defect by generating an abnormality signal when a photoelectric signal received exceeds a specified level to report the existence of a defect when the abnormality signal is generated continuously beyond a specified range. CONSTITUTION:A mesh-like object 32 being transferred vertically is irradiated with a laser light 31 making a scanning from the right to left from a scanner 30. An output signal of a light receiver 34 arranged behind the mesh-like object 32 is supplied to a binary-coding circuit 37 through a filter circuit 36 and the signal exceeding a threshold is made to correspond to '1' and that therebelow to '0' with a binary coding circuit 37. A detection signal from a photo detector 33 for the laser light 31 by which a first scanning is started is supplied to a inspection range setting circuit 39. An AND circuit 41 receives an output signal of the binary-coding circuit 37 through the inspection range setting circuit 39 and a NOT circuit 38 to output a defect candidate signal to a range discriminator circuit 48 thereby enabling detection of a mass defect and a omission defect.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a net-like object inspection device, and more particularly to a net-like object inspection device that is an improved flying spot type surface inspection device using laser light. be.

[Prior Art] As a conventional flying spot type surface inspection device, for example, there is one disclosed in Japanese Patent Application Laid-Open No. 60-209150. In FIG. 4, which shows such a surface inspection apparatus, a scanner 1O having a built-in laser oscillator emits laser light 11 while scanning from right to left. By this scanning, the laser beam 11 draws a scanning line 14a on the object 14 to be inspected.

- The first laser beam 11 of the scan is received by the photodetector 12 and photoelectrically converted. The light receiver 13 is disposed behind the object to be inspected 14 that is being moved in the direction of the arrow X, and receives the laser beam 11 that has passed through the object to be inspected 14 and photoelectrically converts it.

The filter circuit 16 passes only those in a specific frequency range of the photoelectric signals from the photoreceiver 13 and emphasizes defective signals. The binarization circuit 17 gives "1" only to input signals exceeding a preset threshold voltage, and gives "0" to other input signals to digitize them. The inspection width setting circuit 18 uses the signal from the photodetector 12 to
An effective inspection range is determined by excluding the first and last parts of the scanning of the laser beam 11, and "1" is output while within the effective inspection range, and "O" is output during other periods. . The AND circuit 19 outputs a defect detection signal (corresponding to "1") only during the period when the output signals of the binarization circuit 17 and the inspection width setting circuit 18 are both "rl".

FIG. 5 shows the output waveforms from each of the above circuits. (A) of the figure shows the output from the light receiver 13, and if there is a defective part in the object to be inspected, an abnormality signal S as shown appears.

Since the filter circuit 16 only passes high frequency components,
The DC component of the photoreceiver output is cut, and only the rising portion, falling portion, and abnormal signal portion where the photoreceiver output changes rapidly as shown in (B) are extracted and output as a pulse signal. This pulse signal is binarized by a binarization circuit 17 to which a threshold value of a certain level is given, and the binarized output shown in FIG. 2(C) is obtained.

As shown in FIG. 5(D), the output signal from the photodetector 12 generates a pulsed start signal just before the laser beam 11 is irradiated onto the object 14 to be inspected. The test width setting circuit 18 has a clock function, and becomes high level (corresponding to "I") when time k has elapsed from the time when the start pulse was supplied, which means
This will continue until the end of the period. When time 2 elapses, the output signal becomes low level (corresponding to "0").

This operation continues periodically.

Therefore, the AND circuit 19 can correctly output a defect detection signal (corresponding to output signal "1") only for noise indicating the presence of a defect in the effective inspection range.

[Problem to be solved by the invention]

However, the surface inspection device as described above has no problem when the object 14 to be inspected is a flat paper or film, but cannot be used for mesh-like objects such as wire mesh, nets, and coarse nonwoven fabric.

For example, when detecting holes 22, which are holes formed in a synthetic resin net 21, as shown in FIG. In FIG. 6, which shows the waveforms of various parts of the processing circuit when the scanning line 21a is at the illustrated position, (A), which shows seven output signals from the photodetector 13, shows the concave portion corresponding to the "katamari" defect and the " It has a trapezoidal part corresponding to a "dropout" defect. The other parts are periodic parts that repeat periodic scattering caused by a normal mesh, attenuation corresponding to transmission, and elongation. In (B) showing the output signal of the filter circuit 17, the threshold value is set high so as not to output the periodic part, and the four parts and the trapezoid part disappear because the frequency is too low. Therefore, in (F) showing the defect detection signal based on this, a signal indicating the existence of a "catalytic" defect or a "missing" defect is not included.

This is because the above method does not cause defects or defects.
This indicates that the defect is undetectable.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned problems.
An object of the present invention is to provide a net-like object inspection device that can detect defects.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a binarization means that outputs an abnormal signal when the photoelectric signal from the light receiving means exceeds a predetermined level, and a normal signal when the photoelectric signal is lower than the predetermined level; The net-like material inspection apparatus is provided with a discriminating means that notifies the existence of a defective portion when the defective portion continues to occur.

Alternatively, an inverting means for inverting the output signal of the binarizing means may be provided, and when the abnormal signal outputted from the inverting means continues for a predetermined width or more, the presence of a defective portion may be notified.

[Effect]

In a binarization circuit configured to receive laser light transmitted through a net-like material, the threshold value is set to a level at which large-amplitude noise corresponding to the mesh is sufficiently caught. As a result, the binarization circuit normally outputs a large number of periodic output signals. For example, if a "missing" defect exists, the output signal will continue to exceed the set value, so this can be detected and a defect detection signal can be issued.

In addition, when an inverting means is provided, the output signal of the binarizing means is inverted as normal signal→abnormal signal, abnormal signal→normal signal, and then supplied to the discriminating means. By detecting that the above has been reached, it is also possible to detect a "catalytic" defect.

Embodiments of the present invention will be described below with reference to the drawings.

〔Example〕

In FIG. 1, which schematically shows the apparatus for inspecting a net-like object according to the present invention, a laser beam 31 is irradiated from a scanning device 30 while scanning from right to left to a net-like object 32 that is being transported in the vertical direction. As a result, the tip of the laser beam 31 draws a scanning line 32a on the net-like object 32.The tip of the laser beam 31 draws a scanning line 32a on the net-like object 32. The detector 33 performs photoelectric conversion.A light receiver 34 is disposed behind the mesh 32, and receives the laser beam 31 and performs photoelectric conversion.

The output signal of the light receiver 34 is supplied to a binarization circuit 37 via a filter circuit 36. In the binarization circuit 37, a value exceeding the threshold value is associated with "1", and a value less than the threshold value is associated with "0". Since this is the same as the conventional example described above, the details will be omitted.

The output signal of the binarization circuit 37 is inverted in a NOT circuit 38. The output signal of the photodetector 33 is sent to the inspection width setting circuit 3.
9.

AND circuit 41 includes inspection width setting circuit 39 and N.

A defect candidate signal (corresponding to the output signal "1") is output only when both output signals from the T circuit 38 are "1".

The reference clock generation circuit 42 is “1” at high level.
A reference pulse, which is a periodic pulse signal, is output. AND circuit 43 is a reference pulse.

receiving the defect candidate signal and the output from the comparator 44;
When all the inputs are "1", "1" is output, and in other cases, "0" is output. The counter 46 counts the number of reference pulses supplied via the AND circuit 43 when the defect candidate signal is "1". When the supply of the reference pulse is interrupted for a predetermined period, the count number is reset to 0,
When the reference pulse is supplied again, counting starts from O.

The comparator 44 compares this count number with a comparison value set in advance by the digital switch 47.

When the count number is smaller than the comparison value, comparator 4
4 supplies the signal "1" to the AND circuit 43, and when the count number reaches the comparison value, the signal "0" is supplied to the AND circuit 43.
” and outputs a defect detection signal. Reference clock generation circuit 42. AND circuit 43. Counter 46.
A width discrimination circuit 48 is composed of the comparator 44 and the digital switch 47.

Hereinafter, the operation of this embodiment configured as described above will be explained.

FIG. 2 shows the output waveforms from each of the above circuits. FIG. 3A shows the output from the light receiver 34. Abnormal signal A with a concave portion indicates the presence of a “‘katamaru’” defect, and abnormal signal B with a trapezoidal convex portion indicates the presence of a “missing” defect.
This indicates the existence of a major defect. Since the filter circuit 36 passes only high frequency components, the abnormal signals A and B are cut, and only the normal signal is extracted as shown in (B). In the binarization circuit 37, a signal exceeding a predetermined threshold value is set to "1".
, and other parts are mapped with "0" (
It outputs an output signal like C,). This output signal is NOT
is supplied to circuit 38. In the NOT circuit 38, the input signal "
1” → output signal “0”, input signal “0” → output signal “1”
” and outputs the output shown in (C2).

The output signal from the inspection width setting circuit 39 rises after a predetermined period of time has elapsed from the time when the photoelectric signal is supplied from the photodetector 33, and then falls after a predetermined period of time, resulting in the waveform shown in (E). This output signal has also been binarized, with the high level portion after rising being "1" and the low level portions before rising and after falling being "0". This output signal is generated periodically according to the scanning of the laser beam 31.

The output signal of the AND circuit 41 (referred to as defect candidate signal) is
Both the outputs of the inspection width setting circuit 39 and the NOT circuit 38 are "
1”, it becomes “1” as shown in (F).

The defect candidate signal of "1" continues while the abnormal signal A or B is occurring. During this period, the number of reference pulses counted by the counter 46 is the comparison value n (digital switch 47
The comparator 44 issues a defect detection signal as shown in (G). This makes it possible to detect "knock-off" defects and "missing" defects.

Note that although the width discrimination circuit 48 is absolutely necessary, there is no limitation on the configuration as long as it performs the same function as that enclosed by the broken line in FIG. Furthermore, the same principle can be used without providing a filter circuit.

(Effects of the Invention) As described above, the present invention includes a binarization means that outputs an abnormal signal when the photoelectric signal from the light receiving means exceeds a predetermined level, and a normal signal when the photoelectric signal is below that level, and Since a discriminating means is provided which notifies the existence of a defective portion when the defect continues to occur, the existence of a "missing" defect can be detected.

Further, when an inverting means for inverting the output signal of the binarizing means and a determining means for notifying the existence of a defective part when the abnormal signal outputted from the inverting means continues for a predetermined width or more, Since the normal signal output from the binarization means can be detected as an abnormal signal by the discriminating means, the presence of a "catalytic defect" can be detected.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram schematically showing a net-like object inspection apparatus according to the present invention. FIG. 2 is an explanatory diagram showing waveforms at various parts of the processing circuit of the embodiment shown in FIG. 1. Figure 3 shows the “katamari” present in the net-like object to be inspected.
``Defects and blank holes'' is a schematic diagram showing major defects. FIG. 4 is an explanatory diagram showing an outline of a conventional surface inspection device. FIG. 5 is an explanatory diagram showing waveforms at various parts of the conventional processing circuit shown in FIG. 4. FIG. 6 is an action explanatory diagram showing waveforms at various parts when a net-like object is inspected using the surface inspection apparatus of FIG. 4. 39 ・ 41° 42 ・ 44 ・ 48 ・ Inspection width setting circuit 3...AND circuit reference clock generation circuit comparator width discrimination circuit. 30 ・ 32 ・ 2a 33 ・ 34 ・ 36 ・ 37 ・ 38 ・ ・Scanner・Mesh・・Scanning line・Photodetector・Photoreceiver・Filter circuit・Binarization circuit・NOT circuit ha2lusntX'(response)

Claims (2)

[Claims] (1) In an apparatus for inspecting a net-like object by scanning the net-like object in its width direction while irradiating the object with laser light, and receiving the laser beam transmitted through the net-like object by a light-receiving means, a photoelectric signal from the light-receiving means is provided. binarization means that outputs an abnormal signal when the signal exceeds a predetermined level, and a normal signal when the signal is lower than the predetermined level; and a discriminating means that notifies the existence of a defective part when the abnormal signal continues to occur over a predetermined width. A net-like object inspection device characterized by being provided with. (2) The net-like object inspection apparatus according to claim 1, further comprising an inverting means for inverting the output signal of the binarizing means.