JPH01307875A - Defect checking device for long-sized sheet - Google Patents

Abstract

PURPOSE:To improve the defect check precision of a long-sized sheet by providing calculating means of the centroid position in the scanning direction of a repeat pattern, a meandering extent calculating means, and a meandering correcting means. CONSTITUTION:An image sensor camera 1 continuously picks up an image in the direction orthogonal to the movement direction of the sheet and sends the video signal of the repeat pattern image on the sheet to an amplifier 2. An amplified signal (a) is compared with a preliminarily set threshold voltage Vth to obtain a binary signal (b). A meadering correcting circuit 4 corrects the binary signal (b) with the extent of meandering fed back from a centroid detecting circuit 5 and sends the result as a video signal (c) to a memory 6 and a defect discriminating circuit 7. The inputted corrected signal (c) is successively stored in the memory 6 and is periodically sent to the centroid detecting circuit 5. This circuit calculates the centroid of a specific pattern of the repeat pattern and sends the deviation from a learnt reference position to the meandering correcting circuit 4. The discriminating circuit 7 uses a reference mask pattern to mask the corrected signal (c) at the pattern repeat period, and it is discriminated whether a remining picture is defective or not, and the result is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a long sheet defect inspection apparatus for inspecting a sheet-like object to be inspected that is marked with a repeated pattern and is continuously sent out.

(Summary of the Invention) The present invention provides defect inspection that optically continuously detects defective parts using image data obtained by imaging a long sheet-like object on which a repetitive image pattern is formed using an image sensor camera. In the apparatus, the position of the center of gravity of the repeated image pattern on the object to be inspected is determined from the image data obtained by imaging, and the amount of meandering of the object to be inspected is determined by comparing that position with a reference position stored in advance. The image data is shifted and corrected for each scanning section according to the amount of meandering, and then sent to the defect inspection section to improve inspection accuracy.

(Prior art and its problems) In the inspection line for long sheets printed with repeated patterns and sent out, defects in the printed pattern, dirt and dust adhesion, defects in the sheet material itself, etc. are photographed using a CCD camera. Image data and repetitive patterns learned in advance are superimposed to remove the repetitive patterns in the image data obtained from the inspected object, so-called mask processing is performed, and defective parts are identified based on the remaining image data. A method was taken to detect it.

However, with these inspection devices, meandering occurs when the sheet material moves along a line, and even with a mechanical meandering correction device, it is impossible to eliminate meandering at the pixel level of image data. Met.

Therefore, when performing mask processing on the obtained image data, a method has been adopted in which the width of the mask image is increased in anticipation of the meandering amount in advance.

As a result, the uninspected area around the printed pattern to be masked is expanded in the horizontal direction, and defects occurring in the If and fj areas are overlooked. This was a major drawback of defect inspection equipment that adopted the mask processing method.

(Objective of the Invention) This invention has been proposed in view of the point mentioned in 1.The purpose of the invention is to minimize the uninspected area, reduce missed defects, and increase the cost of inspection. An object of the present invention is to provide a defect inspection device for long sheets.

(Structure and Effects of the Invention) In order to achieve the above object, the present invention allows a long sheet-like object to be inspected, which moves continuously in the longitudinal direction and has a repetitive image pattern formed on its surface, to be inspected in the moving direction. In a long sheet defect inspection device that optically detects defects in an inspected object based on image data obtained from an image sensor camera that scans and captures images in orthogonal directions,
Calculation means for calculating the center of gravity position of a predetermined pattern in the scanning direction in the repeated image pattern with the detected object from the image data; the center of gravity position of the predetermined pattern obtained from the calculation means;
a calculation means for calculating the amount of meandering of the object to be inspected by comparing and contrasting the position of the center of gravity of a reference pattern that has been learned in advance and corresponds to this pattern; and scanning the image data based on the amount of meandering obtained from this calculation means. The present invention is characterized by comprising a meandering correction means that corrects the meandering by shifting for each section and then sends the meandering correction means to the defect determining section.

This invention automatically calculates the amount of meandering and corrects the meandering at the data level, making it possible to set the width of the mask image to the minimum necessary, reducing the inspection area for defects. There are fewer oversights (this has the effect of increasing inspection accuracy).

(Description of Embodiment) FIG. 1 is a block diagram showing the electrical configuration of an embodiment according to the present invention.

In the figure, an image sensor camera 1 is composed of a CCD camera or the like, and is placed above a continuously moving long sheet. This camera 1 continuously scans and images the sheet in a direction perpendicular to the moving direction, and the video signal is sent to Amp 2 because it cannot apply a voltage corresponding to the degree of brightness of the repeated pattern image such as a printed mark formed on the sheet. Sent out.

Amp2 amplifies the input video signal and sends it to the binarization circuit 3 as video signal a shown in FIG.

The binarization circuit 3 compares the input video signal a with a preset threshold level vT, and
, I is set to 1 for the video signal a higher than I, and 0 for the video signal lower than that, and the binarized signal S shown in FIG. 2 is sent to the meandering correction circuit 4.

The meandering correction circuit 4 corrects the input binary signal S based on the amount of meandering fed back from the center of gravity detection circuit 5, which will be described later, and sends it as a corrected signal C to the memory 6 and the defect determination circuit 7.

The memory 6 sequentially stores the input corrected signal C, and at the same time sends the value to the center of gravity detection circuit 5 at regular intervals.

Based on the input corrected signal C, the center of gravity detection circuit 5
The center of gravity for a specific pattern within the repeating pattern is calculated, and the deviation from the reference center of gravity position written in advance through learning is calculated as the meandering amount and sent to the meandering correction circuit 4.

This meandering amount is simultaneously sent to an external meandering correction device (not shown).

The defect discrimination circuit 7 uses a standard mask pattern learned in advance for the input corrected signal C, and
Mask processing is performed at each pattern repetition period, and the remaining images are determined whether they are defects or not, and the results are output.

The operations of these parts are performed in real time as the sheet moves.

FIG. 3 is a schematic diagram showing the internal configuration of the meandering correction circuit 4.

The meandering boat setting circuit 41 sets a valid data range based on the input meandering amount and a preset effective field of view width, and sends it to the meandering boat memory 42.

The effective field of view width is the l obtained by the image sensor camera I.
This is the data length actually used for defect inspection among the scanned image data. Normally, the outer end of the entire field of view obtained by the image sensor camera l is unclear due to lens aberrations, etc., so what is actually used is the middle range excluding that part. This range is the effective visual field width, and by setting this effective visual field width with a margin, a sufficiently usable visual field can be provided on both sides.

The valid range of data sent to the meandering port memory 42 refers to a range of a predetermined length of image data selected for image processing such as defect determination within the entire field of view obtained by the camera 1.

The relationship between the overall field of view and the data mediation range is shown in the explanatory diagram of the meandering boat memory 42 shown in FIG.

The meandering boat memory 42 consists of a 4-bit RAM as shown in FIG. 4, and 1 is set in the corresponding position of the lowest effective bit string based on the input data valid range. At the same time, in the upper end focus row, 1 is set only for the last focus in the data effective range.

The correction processing circuit 43 refers to the meandering port memory 42 and
Only the data corresponding to the valid data range of the binary signal inputted for each scanning section is extracted and outputted as the corrected signal C.

The image sensor scan synchronization circuit 44 sends pulses synchronized with the scanning of the image sensor camera 1 to the address counter 45 .

The address counter 45 counts the input pulses and stores the sequentially obtained address data in the meandering boat memory 42.
Send to.

FIG. 5 is a diagram illustrating the operation of the center of gravity detection circuit 5. As shown in FIG.

In Figure a, a sheet S that is imaged by an image sensor camera l is printed with a constant pitch PT: a repeating pattern in the moving direction. In the repeating pattern of the embodiment, five ring-shaped marks M are arranged, one of which is used for detecting the amount of meandering.

The figure is an enlarged view of the rectangular portion Q that includes the mark M at the lower right of the section AB in the moving direction of the sheet S.

In Figure C, processing is performed to fill in the hollow part of the upper half of this mark, resulting in a semicircular shape. The number of pixels is also determined for the part.The horizontal center of gravity is calculated based on these white and black pixel counts.As shown in Figure d, this center of gravity is located from the reference center of the sheet S to the rectangular part Q. It is obtained by adding the obtained "area center of gravity" to the "lower limit" of the distance to the left end of the pixel data. Processing regarding these pixel data is performed by known algorithm processing.

The amount of meandering is determined by sequentially comparing the center of gravity positions obtained in this way at the positions A, BSC, D, . . . for each repeated pattern.

FIG. 6 is an explanatory diagram showing the correction of the binary signal in the correction processing circuit 43.

In the figure (a), a correction value signal C whose total length is equal to the 1f level section of the data effective range is obtained by taking in the manually inputted binary signal S in the normal data effective range in a state where no meandering occurs.

In the figure, since a rightward meander occurs in the binarized signal, the H level of the data valid range is shifted in the same direction as the meander. As a result, the meandering amount of the captured correction value signal C is corrected and becomes equal to that shown in FIG. a.

Figure C shows a case where a new leftward meandering occurs from the state shown in the figure, and a correction equal to the new meandering amount is added to the valid data range, so that the correction value signal C becomes normal as shown in the figure. shifted to the state.

These corrections sequentially shift the valid data range based on the lighting value of the meandering amount when meandering occurs, but the absolute value of the meandering amount is measured and the data valid range is adjusted based on that value. It is also possible to set the H level.

With this embodiment configured as described above, the center of gravity position of a predetermined pattern is detected from the binarized signal indicating the image data obtained from the image sensor camera l, and the meandering amount of the sheet is detected in the 14th order. , the meandering is corrected by shifting the binarized signal for each scanning section according to the amount of meandering.

As a result, even when multiple image sensor cameras installed in a defect inspection device are arranged in parallel to inspect a wider sheet, each image sensor camera
The process of synthesizing data from can be performed relatively easily.

Conventionally, in order to specify the lateral reference position of a moving sheet, meandering was detected by the edge of the sheet to be inspected, position detection marks were specially provided on the sheet for meandering detection, or other methods were used. However, this embodiment eliminates the need for such external triggers and increases the number of types of sheet materials that can be inspected.

Similarly, the binarized signal captured as image data is
Since it is corrected before being input to the defect discriminating circuit 7, there is no need for special correction processing within the defect discriminating circuit 7, and the structure of the defect discriminating circuit 7 becomes ffl-like, and the inspection processing speed is accordingly reduced. It gets faster.

Furthermore, since the meandering can be almost completely corrected, it becomes unnecessary to expand the mask pattern in the lateral direction used for defect discrimination, and the beam inspection area becomes smaller, improving the accuracy of defect inspection.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the electrical configuration of an embodiment according to the present invention, FIG. 2 is a signal waveform diagram showing the operation in the first answering section, and FIG. 3 is a block diagram showing the internal configuration of the meandering correction circuit 4. , FIG. 4 is a diagram showing the internal structure of the meandering boat memory 42, FIG. 5 is a diagram showing the process of determining the center of gravity from a repeating pattern, and FIG. 6 is a diagram showing a specific example of meandering correction. l... Image sensor camera 2... Amp 3... Binarization circuit 4... Meandering correction circuit 5... Center of gravity detection circuit 6 ...Memory 7...Defect determination circuit 41...Meandering boat setting circuit 42...
・Meandering boat memory 43...Correction processing circuit 44...Image sensor scan synchronization circuit 45
・・・・・・Address counter

Claims (1)

[Claims] 1. An image sensor camera that scans and images a long sheet-like object to be inspected that moves continuously in the longitudinal direction and has a repeated image pattern formed on its surface in a direction perpendicular to the direction of movement. Based on the image data obtained from
In a long sheet defect inspection apparatus that optically detects defects on an object to be inspected, a calculation means for calculating a center of gravity position in a scanning direction of a predetermined pattern in a repeated image pattern on an object to be inspected from the image data; the center of gravity position of the predetermined pattern obtained from the means;
a calculation means for calculating the amount of meandering of the object to be inspected by comparing and contrasting the position of the center of gravity of a reference pattern that has been learned in advance and corresponds to this pattern; and scanning the image data based on the amount of meandering obtained from the calculation means. A long sheet defect inspection device comprising: meandering correction means for correcting meandering by shifting for each section and then sending the meandering to a defect determining section.