JP2861338B2 - Optical inspection equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION << Industrial application field >> The present invention relates to an optical inspection apparatus using an imaging means,
In particular, the present invention relates to an optical inspection apparatus that performs a defect inspection of a sheet-like inspection object such as a paper, a metal plate, a plastic film, and a cloth, and a finish condition inspection such as a formation inspection.

<< Conventional Technology >> In the paper manufacturing process, there are two types of inspection: defect inspection to check for defects such as holes and dirt, and formation inspection to check the degree of paper fiber entanglement and dispersion. As an inspection device for performing this type of inspection, an imaging device such as a CCD camera (CCD image sensor) is used, and an image of the paper surface is captured by a fixed imaging device while the roll paper before cutting is running.
There is known a configuration in which the inspection is performed optically by signal processing of the video signal. This type of inspection apparatus is disclosed in, for example, JP-A-2-82144 and JP-A-2-90047.

<< Problems to be Solved by the Invention >> In the above-described paper defect inspection, planar two-dimensional image data is not necessary, and a direction transverse to the paper traveling direction is not necessary.
That is, it is only necessary to obtain video data as linear one-dimensional image data along the width direction of the paper. However, in order to inspect for defects such as holes and dirt over the entire area of the paper, It is necessary to take an image of the paper surface over the entire area and continuously without any gap in the paper traveling direction. Therefore, in the defect inspection, the imaging device may be a linear imaging device such as a linear CCD camera that continuously captures a running paper as a one-dimensional image over the entire width direction.

On the other hand, in the paper formation inspection as described above, the paper surface is not necessarily in a direction transverse to the paper running direction, that is, over the entire area in the width direction of the paper, and continuously in the running direction of the paper without any gap. Although it is not necessary to take images, however, video data for obtaining planar two-dimensional image data as a still image is necessary. Therefore, in the formation inspection, such as an area CCD camera with a shutter is used. An area imaging device with a shutter or a strobe lighting device and an area imaging device are required, and the device becomes large-scale.

Further, in the formation inspection, when video data including image data of a defective portion is taken in, data for the formation inspection becomes erroneous based on the image data of the defect image.
For example, in the watermark formation inspection, when the grayscale signal is binarized at an appropriate discrimination level and the grayscale is displayed as a graph of the area ratio, or when the density is displayed as a histogram,
Even if the watermark formation is the same, the display results will be different as shown in FIGS. 6 and 7.

In FIGS. 6 and 7, (a) shows a static two-dimensional image with a predetermined area of paper, (b) shows how to binarize a grayscale signal at an appropriate discrimination level, and (c) () Shows a graph display example in which the density ratio is binarized at an appropriate discrimination level, and (d) shows a display example in which the density is displayed in a histogram.

For this reason, conventionally, it was necessary to perform the formation inspection while confirming the presence / absence of a defect by using a screen display as shown in FIGS. 6 (a) and 7 (a).

The present invention provides a finishing condition inspection that requires video data as planar two-dimensional still image data, such as a paper formation inspection, by using an area imaging device with a shutter such as an area CCD camera with a shutter, or a strobe. Without the need for an illumination device and an area imager, the image data of a linear imager, such as a linear CCD camera, is used for inspection, and defect inspection is also performed from this image data. It is an object of the present invention to provide an optical inspection device that automatically performs continuous collection.

<< Means for Solving the Problems >> According to the present invention, the object as described above is to provide a linear imaging unit that captures a moving inspection object as a one-dimensional image in a width direction, and a video signal from the linear imaging unit. A defect detection unit that performs binarization at a predetermined discrimination level and performs defect detection, and a memory that sequentially stores video signals from the linear imaging unit and clears memory contents when a defect is detected by the defect detection unit. Image processing means for sequentially taking out video signals stored in the memory and performing two-dimensional image data processing for a finish condition inspection from a collection of the video signals. Is done.

<< Operation >> According to the configuration as described above, the video signal obtained by imaging the inspection object as a one-dimensional image in the width direction by the linear imaging means is binarized at a predetermined discrimination level by the defect detection means. Defect detection is performed by the binarized binary signal, and video signals obtained by the linear imaging unit capturing the inspection object as a one-dimensional image in the width direction are sequentially stored in a memory. As a result, a video signal necessary for creating a two-dimensional image for one frame is obtained, and planar two-dimensional image data as a still image is obtained from this, and a finish condition inspection such as a paper formation inspection can be performed. Done. When the defect detection is performed, the contents of the memory are cleared, and the image processing for the formation check and the display thereof are prevented from being performed by the data including the video data of the defect image.

<< Example >> Hereinafter, the present invention will be described in detail with reference to the accompanying drawings with reference to examples.

FIG. 1 shows an embodiment of the overall configuration of an optical inspection apparatus according to the present invention. The optical inspection apparatus according to the present invention has a linear CCD camera 10 as linear imaging means.
The linear CCD camera 10 captures an image of the paper surface without gaps over the entire width of the paper P to be inspected and continuously in the running direction of the paper P running at a predetermined constant speed. To this end, a plurality of papers P are fixedly arranged above the paper P at predetermined intervals in the width direction of the paper P. Below the paper P, a linear CCD
A slit-shaped light source means 12 extending across the entire area of the paper P in the width direction facing the camera 10 is fixedly arranged.

The linear CCD camera 10 is provided with the irradiating light applied to the paper P from the light source means 12 as transmitted light transmitted through the paper P, and continuously captures a light image due to a change in the light amount as a one-dimensional image in the width direction of the paper P. Then, a video signal (see FIG. 3 (a)) obtained by photoelectric conversion is converted into a defect discrimination processing unit as shown in FIG.
20 and the formation monitor processing unit 30.

The defect discrimination processing unit 20, the formation monitoring processing unit 30, and the display 40 such as a CRT are provided in the control equipment console box 14 as shown in FIG.

Next, the defect determination processing section 20 and the formation monitoring processing section 30 will be described with reference to FIG. The defect determination processing unit 20 includes a discrimination unit 22, a size determination unit 24, and a defect detection output interface unit 26.

The discrimination unit 22 receives a video signal (the third signal) from the linear CCD camera 10.
(See FIG. 3 (a)), which is shown in FIG. 3 (b) with a discrimination level for detecting a hole defect and a discrimination level for detecting a dirt defect. As shown in (c) and (d), the image data is binarized and output to the size determination unit 24.

FIG. 3 (c) shows a hole defect signal, and FIG. 3 (d)
Indicates a stain defect signal.

The size discriminating unit 24 is based on the sensitivity (threshold) in the width direction determined by the video frequency clock and the sensitivity (threshold) in the length direction (running direction) determined by the travel distance pulse of the paper P. The high-level duration of the perforated defect signal or the dirt defect signal is monitored, and if this is equal to or greater than a predetermined threshold, a defect detection signal is output to the interface unit 26 as a coincidence output. I have.

The formation monitor processing unit 30 includes an A / D converter 32 and a memory 34.
And an image processing unit 36.

The A / D converter 32 is provided with a video signal obtained by the linear CCD camera 10 capturing the paper P as a one-dimensional image in the width direction from the linear CCD camera 10 and has a multi-gradation weight. The digital signals are converted into digital signals, and the digital signals are sequentially output to the memory 34.

The memory 34 fetches a digital signal having weights of multiple gradations unless a defect detection signal is given from the defect determination processing section 20 and sequentially stores the digital signal for every predetermined frame for each frame. When a defect detection signal is given from the processing unit 20, the current memory contents for one frame are cleared by delete. Thus, only formation data as a two-dimensional image that does not include a defect image is collected and stored in the memory 34.

The image processing unit 36 sequentially receives one frame of digital signals having multi-tone weights stored in the memory 34 by receiving a data creation signal from the outside, and obtains a planar image as a still image from the collection of the digital signals. And performs image processing necessary for the formation inspection of the paper P, such as contour enhancement processing, shading enhancement processing, frequency analysis processing, and other feature amount extraction processing. The display signal is output to a display 40 such as a CRT. The image processing required for the formation inspection of the paper P may be performed in substantially the same manner as described in JP-A-2-82144.

The display unit 40 is provided with a pixel display signal for one frame from the image processing unit 36, and in accordance with the image display signal, displays a two-dimensional shading image of a formation, a three-dimensional density distribution image display, and the like. Image display of the feature amount is performed for formation inspection.

The image display signal output from the image processing unit 36 may be given to the printer 42 and the memory 44 in addition to the display unit 40.In this case, information for formation inspection is printed by the printer 43, and the information is printed on the memory 43. 44 will be saved.

With the configuration described above, the paper P is captured as a one-dimensional image in the width direction by the linear CCD camera 10, and the video signal obtained thereby is binarized by the discrimination unit 22 at a predetermined discrimination level. Defect detection is performed by the converted binary signal.

The video signal is converted into a digital signal having a multi-gradation weight by the A / D converter 32, and the digital signal is sequentially stored in the memory 34 unless the digital signal includes defect image data. A video signal required for creating a two-dimensional still image for a frame is obtained. As a result, only the surface information that does not include the defect image of the paper P is displayed on the display 40, so that the formation inspection of the paper P is always appropriately performed.

FIG. 4 shows a time chart of signal processing when there is no defect, and FIG. 5 shows a time chart of signal processing when there is a defect. In both figures, (a) shows a video signal, (B) shows a data creation signal, (c) shows one data accumulation period of the memory 34, (d) a memory reset signal composed of a defect detection signal given to the memory 34, and (e) a memory 34
3 shows data transfer to the image processing unit 36.

From this time chart, if the video signal includes data of a defective image, the data accumulation in the memory 34 is released,
It will be understood that the accumulation of new data is started again and the accumulated data including the data of the defective image is discarded, and this is not transferred to the image processing section 36.

Note that, in the above-described embodiment, the transmitted light type inspection apparatus has been described.
The present invention is not limited to this, and is also applied to a reflection light type inspection apparatus, and is an optical device that performs a defect inspection and a finish condition inspection of a sheet-like inspection object such as a metal plate, a plastic film, and a cloth other than paper. It is also applied as a type inspection device.

<< Effects of the Invention >> As is clear from the above description, according to the optical inspection apparatus of the present invention, an object to be inspected such as paper is imaged as a one-dimensional image in the width direction by linear imaging means such as a linear CCD camera. The video signal obtained by the above is binarized at a predetermined discrimination level by the defect detection unit, defect detection is performed by the binarized binary signal, and the linear imaging unit moves the inspection object in the width direction. By sequentially storing video signals obtained by capturing as a one-dimensional image in a memory, a video signal necessary for creating a two-dimensional still image for one frame is obtained. Planar two-dimensional still image data is obtained, so that a finishing condition inspection that requires video data as planar two-dimensional still image data, such as a paper formation inspection, has a shutter. This can be performed without the need for an area imaging device with a shutter such as an area CCD camera, or dedicated imaging means such as a strobe lighting device and an area imaging device. Further, when the defect detection is performed, the contents of the memory are automatically cleared, and the image processing for the formation inspection and the display thereof are prevented from being performed by the data including the video data of the defect image. As a result, data processing for proper formation inspection and continuous data collection can be automatically performed.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of the entire configuration of an optical inspection apparatus according to the present invention, and FIG. 2 is a block diagram of a defect discrimination processing section and a formation monitoring processing section used in the optical inspection apparatus according to the present invention. FIGS. 3 (a) to 3 (d) are signal waveform diagrams in the optical inspection apparatus according to the present invention, and FIGS. 4 (a) to 4 (d).
(E) is a time chart of signal processing when there is no defect,
FIGS. 5 (a) to 5 (e) are time charts of signal processing when there is a defect, and FIGS. 6 (a) to (d) are explanations showing image processing procedures for formation inspection when there is no defect. FIGS. 7 (a) to 7 (d) are explanatory diagrams showing image processing procedures for formation inspection when there is a defect. 10 Linear CCD camera 12 Light source means 14 Control device console box 20 Defect discrimination processing unit 22 Discrimination unit 24 Discrimination unit 26 Defect detection output interface unit 30 Formation monitoring processing Section 32 A / D converter 34 Memory 36 Image processing section Display 42 Printer 44 Memory

Claims (1)

(57) [Claims] 1. A linear imaging means for capturing an image of a traveling inspection object as a one-dimensional image in a width direction, and a defect detection for binarizing a video signal from the linear imaging means at a predetermined discrimination level to detect a defect. Means for sequentially storing video signals from the linear imaging means, and for clearing the contents of the memory when a defect is detected by the defect detection means; and sequentially collecting the video signals stored in the memory. An image processing means for performing two-dimensional image data processing for a more finished condition inspection.