JPH0629862B2 - Inspection equipment - Google Patents

Description

The present invention relates to an inspection device for inspecting an object to be inspected such as a paper sheet.

<< Summary of the Invention >> The inspection device according to the present invention uses a first low-pass filter for the high-frequency noise of a video signal obtained by pre-processing, for example, sampling and holding a raw video signal obtained by photographing an object to be inspected. At the time of removing, the ground composite component of the video signal is taken out by the second low-pass filter and removed from the output of the first low-pass filter.
Other signals included in the output of the low-pass filter, for example, a defect signal indicating a defect of the inspected object is emphasized, and this can be changed without changing the size and width of the defect signal indicating the defect of the defect signal. It is designed to be easily detected.

<Prior art> In the paper manufacturing industry, which is a division that handles sheet-like materials, the paper during the manufacturing process and the paper after manufacturing are applied to an inspection device,
The quality of the paper is constantly checked.

FIG. 3 is a block diagram showing an example of such an inspection device. The inspection apparatus 1 shown in this figure continuously inspects the quality of the paper 2 during the manufacturing process, and includes a light source 3 provided below the paper 2 stretched between the rollers 8a and 8b and the paper 2. An image sensor 4 which is provided above and photographs the paper 2 illuminated from the lower surface side by the light obtained by the light source 3, and FIG. 4 (A) obtained by the image sensor 4. ), The raw video signal S1 of the paper 2 as shown in FIG.
A preprocessing circuit 5 for creating a video signal S2 as shown in FIG.
When the video signal S2 output from the preprocessing circuit 5 is low-pass processed and high-pass processed and then level-discriminated, the video signal S2 includes a defect signal S3 indicating that the paper 2 has a scratch or the like. The fourth by extracting the signal S3
(E) and (F) the level discrimination circuit 6 for outputting the defect detection signal S6, and when the level discrimination circuit 6 outputs the defect detection signal S6, a warning lamp is turned on or paper 2 is made. The paper 2 is provided with a post-processing circuit 7 for supplying a control signal to a manufacturing apparatus and the like, and a discriminating circuit 9 for receiving the video signal S2 and performing various kinds of processing. It is configured to continuously check two qualities.

<< Problems to be Solved by the Invention >> By the way, in the conventional inspection apparatus 1, the pulse-shaped raw video signal S1 output from the image sensor 4 is supplied to the sampling and holding circuit (S / H circuit) 10 of the preprocessing circuit 5. Therefore, by sampling and holding, the raw video signal S1 is converted into a continuous video signal S2, and the raw video signal S1 is obtained.
The direct current component therein is removed and supplied to the level discriminating circuit 7, where the video signal S2 is level discriminated and when the video signal S2 includes a defect signal S3, it is detected. Therefore, there are the following problems.

(A) Video signal S2 supplied to the level discrimination circuit 6
4B, switching noise S4 (high-frequency noise) generated when sampling and holding processing is performed by the sampling and holding circuit 10 of the preprocessing circuit 5 and the paper 2 imaged by the image sensor 4 are shown in FIG. Is overlapped with the formation signal (low-frequency noise) S5 caused by unevenness of illumination of the light source 3, unevenness of illumination by the light source 3, and the like, so that the video signal S2 is generated by the low-pass filter 11 of the level discriminating circuit 6.
Is low-pass processed to obtain a signal S8 as shown in FIG.
If the high pass filter 12 does not perform the high pass processing after the setting, the level discriminator 13 outputs the video signal S
The defect signal S3 in 2 cannot be detected. And in this case,
Since the defect signal S3 becomes a positive-direction pulse or a negative-direction pulse depending on the defect state of the paper 2,
Usually, the level discriminator 13 has two discrimination levels V ₁ and V ₂
However, when the width of the defect signal S3 is wide, the signal S8 corresponding to the video signal S2 is subjected to high-pass processing, and when the low frequency component is cut, the defect signal S3 is generated. Since the signal S7 is differentiated and becomes a signal S7 as shown in FIG. 4 (D), the same defect detection as in the case where there are two defects from the level discriminator 13 as shown in FIGS. 4 (E) and (F). There is a problem that the signal S6 is output.

(B) Further, since the signal S7 output from the high-pass filter 12 has a differentiated waveform, the signal S7 is used as a gate to count the reference clock CK as shown in FIG. 4 (G). However, there is a problem that the size (width) of the defect signal S3 cannot be determined.

In view of the above circumstances, the present invention can make the number of defect signals S3 included in the video signal S2 correspond to the number of defect detection signals S6 output from the level discriminator 13, and by using the reference clock CK. It is an object of the present invention to provide an inspection device capable of discriminating the width (size) of the defect signal S3.

<< Means for Solving the Problems >> In order to solve the above problems, an inspection apparatus according to the present invention includes an image capturing unit that captures an image of an object to be inspected and outputs a video signal of the object to be inspected; A first low-pass filter for removing noise, a second low-pass filter for extracting a ground composite component from the video signal, and an arithmetic circuit for subtracting the output of the second low-pass filter from the output of the first low-pass filter. And a processing circuit for processing the output of the arithmetic circuit to detect a defect signal in the output of the first low-pass filter.

<< Embodiment >> FIG. 1 is a block diagram showing an embodiment of the inspection apparatus according to the present invention, and FIGS. 2A to 2G are waveform diagrams of this embodiment. The inspection device 25 shown in FIG.
A level discriminator that attenuates the formation signal in the video signal obtained by photographing the paper 27 conveyed in the direction of the arrow while being stretched on b and the switching noise during the sampling and holding processing, and then discriminates the level. The light source 28, the image sensor 29, the preprocessing circuit 30, the determination circuit 31, the level discrimination circuit 32, and the postprocessing circuit 33 are configured.

The light source 28 is composed of a lamp or the like arranged on the lower surface of the paper 27.
7 is illuminated from below.

An image sensor (imaging unit) 29 is provided above the paper 27 and is illuminated from the lower surface side by the light source 28 by a CCD (solid-state image sensor) or the like.
Is photographed and a pulsed raw video signal S10 as shown in FIG. 2 (A) is output, and this video signal S10 is supplied to the preprocessing circuit 30.

The preprocessing circuit 30 samples and holds the video signal S10 and converts it into a continuous video signal, and preamplifies, linearizes (linearly corrects) the video signal, or performs other preprocessing. The video signal S11 obtained by preprocessing here is supplied to the discrimination circuit 31 and the level discrimination circuit 32. That is, the light source 28, the image sensor 29, and the preprocessing circuit 30 constitute a photographing unit that photographs the inspection object 27 and outputs a video signal of the inspection object.

The discriminating circuit 31 is configured to generate various control signals from the video signal S11 and perform image processing. The processing result here is the manufacturing control device of the paper 27, the display device, etc. (Not shown).

When the video signal S11 includes the defect signal S12, the level determination circuit 32 detects the defect signal S12 and outputs the defect detection pulse train signal S17. The level detection circuit 32 includes a first low-pass filter 34, a second low-pass filter 35, and a level. And a discriminator 36. The second low-pass filter 35 includes a resistor 37 and a capacitor 38 for low-pass processing the video signal S11 at a cutoff frequency fc2, and an operational amplifier 39 for non-inverting amplifying the signal low-pass processed by the resistor 37 and the capacitor 38. If the pre-processing circuit 30 outputs a video signal S11 as shown in FIG. 2B, it is configured to include resistors 41 and 42 that determine the gain of the operational amplifier 39. The 2 low-pass filter 35 low-pass processes the video signal S11 to extract a formation signal S13 (see FIG. 2C) included in the video signal S11 and supplies it to the first low-pass filter 34. The first low-pass filter 34 includes resistors 43, 44, 45, 46, 47 and capacitors 48, 4
Cutoff frequency fc1 including 9, 50 and operational amplifier 51
(Fc1> fc2), which is a control source type low-pass filter, in which the preprocessing circuit 30 outputs a video signal S11 as shown in FIG.
If the low-pass filter 35 outputs a formation signal S13 as shown in FIG. 2 (C), the first low-pass filter 3
The switching noise S14, which is a high-frequency noise in the video signal S11, is removed by 4 and the formation signal S13, which is the ground composite component extracted from the second low-pass filter 35, is inverted and added to the switching noise S14.
The formation signal S13 therein is canceled, and the signal S14 (see FIG. 2 (D)) which is the result of this processing is supplied to the level discriminator 36. That is, the output of the operational amplifier 39 is connected to the resistor 47.
By making it the inverting input of the operational amplifier 51 via
An arithmetic circuit that subtracts the output of the second low-pass filter 35 from the output of the first low-pass filter 34 is configured. The level discriminator 36 outputs a gate open signal (“1” signal) S15 as shown in FIG. 2 (E) when the value of the signal S14 is higher than the first discrimination level V _1, the first comparator 53.
And the value of the signal S14 is the second discrimination level V ₂ (V ₂ <
Vn <V ₁ ; However, when Vn is a steady value of the signal S14 and usually lower than 0V, the gate open signal (“1”)
Signal) S16 and a second comparator 54 for passing a reference clock signal CK as shown in FIG. 2 (F) when the gate open signal S15 is output.
5 and an AND gate 56 that passes the reference clock signal CK when the gate open signal S16 is output. If the signal S14 includes the defect signal S12, Upon detecting this, the defect detection pulse train signal S17 shown in FIG. 2 (G) is output,
This is supplied to the post-processing circuit 33, and a control signal or the like is output from the post-processing circuit 33.

As described above, in this embodiment, the video signal S1 output from the preprocessing circuit 30 by the second low-pass filter 35.
1. The formation signal S13 superimposed on 1 is extracted, and the switching noise S14 in the video signal S11 is cut by the first low-pass filter 34, and the formation signal obtained by the second low-pass filter 35 from the cutting result. S13
Therefore, it is possible to accurately discriminate the level of only the defect signal S12 included in the raw video signal S10, and to count the number of reference clock signals CK included in the defect detection pulse train signal S17. The width (width) can also be known accurately.

<< Advantages of the Invention >> As described above, in the inspection apparatus according to the present invention, it is possible to accurately detect the defect of the inspection object from the image signal obtained by photographing the inspection object such as paper, and The size of the defect can also be known accurately.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of an inspection apparatus according to the present invention, FIGS. 2A to 2G are waveform diagrams for explaining the same embodiment, and FIG. 3 is a conventional inspection apparatus. Block diagrams showing an example, and FIGS. 4A to 4G are waveform diagrams for explaining the inspection apparatus shown in FIG. 3, respectively. 25 ... Inspecting device, 27 ... Inspected object (paper), 29 ... Imaging unit (image sensor), 34 ... First low-pass filter, 3
5 ... 2nd low-pass filter, 36 ... Processing circuit (level discriminator).

Claims (1)

[Claims] 1. A photographing unit for photographing an object to be inspected and outputting a video signal of the object to be inspected, a first low-pass filter for removing high-frequency noise from the image signal, and a ground composite component extracted from the image signal. A second low-pass filter, and the first
An arithmetic circuit that subtracts the output of the second low-pass filter from the output of the low-pass filter, and a processing circuit that processes the output of the arithmetic circuit and inspects a defect signal in the output of the first low-pass filter. Inspection device characterized by