Abstract:
A surface inspection system including, a detection circuit for detecting an image of a surface fault in a runing sheet material, a fault area judgement circuit connected to the detection circuit for receiving the image and for determining a fault area including a cluster fault composed of the same type of fault parts, and a recognition circuit connected to the detection circuit for receiving the image, connected to the fault area judgement circuit for receiving the fault area, and for recognizing a type and a grade of the cluster fault included in the fault area.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a surface inspection system, and more particularly to a surface inspection system which detects surface faults in a running sheet material. 
     2. Description of the Related Art 
     As a prior art surface inspection system, there is, for example, a system such as that shown in FIG. 5. This system is composed of a detector 3 as a detection means which detects an image of a surface fault 2 on a running sheet material 1, a line synchronizing signal generator 5 connected to a roller 4 for detecting the running of sheet material 1, a dividing circuit 6 which divides the surface to be inspected of sheet material 1 into divided surfaces of a specified size in the width direction and length direction without any relation to the position of faults, and a recognition circuit 7 which judges the types and grades of faults contained in each divided surface. 
     In this way, this surface inspection system is designed automatically to inspect the surface of sheet material 1. FIG. 6 shows an example of faults on the surface of sheet material 1 and an example of the composition of divided surfaces on the surface of sheet material 1. In FIG. 6, A is a group of linear faults distributed in the length direction of sheet material 1, B is a group of dot-shaped faults, C is an intermittent narrow linear fault, and D is an isolated dot-shaped fault. Also, L 1 , L 2 , L 3 , L 4  and L 5  are dividing lines in the length direction and D 1 , D 2  and D 3  are dividing lines in the width direction, and the surface of sheet material 1 is divided into multiple divided surfaces by these dividing lines. 
     The prior art surface inspection system described above is disclosed in Japanese Patent Publication (Kokoku), No. Sho. 61-47362 published on Oct. 18, 1986. 
     In the prior art surface inspection system, the surface subject to inspection of the sheet material was divided into divided surfaces of a specified size, and the types and grades of the faults were judged for every fault contained in each of those divided surfaces. However, as shown in the examples in FIG. 6, most of the surface faults of the sheet material should be judged as a single fault composed of a group of several faults. The shapes of the faults are generally complex, and the positions of the faults are indeterminate. As the surface subject to inspection of the sheet material is divided into divided surfaces with a specified size in the width direction and the length direction, it happens that faults such as faults A, B and C, straddle multiple divided surfaces. Thus, there is a problem that it is difficult to correctly judge the types and grades of the these faults. 
     SUMMARY OF THE INVENTION 
     Accordingly, one object of this invention is to provide a surface inspection system which can correctly recognize at high speed in real time the type and grade of each fault, even in cases when there are various shapes of surface faults on the sheet material and those surface faults are composed of multiple parts. 
     These and other objects of this invention can be achieved by providing a surface inspection system including, a detection circuit for detecting an image of a surface fault in a running sheet material, a fault area judgement circuit connected to the detection circuit for receiving the image and for determining a fault area including a cluster fault composed of the same type of fault parts, and a recognition circuit connected to the detection circuit for receiving the image, connected to the fault area judgement circuit for receiving the fault area, and for recognizing a type and a grade of the cluster fault included in the fault area. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
     FIG. 1 is a block diagram showing the composition of a surface inspection system according to an embodiment of this invention; 
     FIGS. 2a-2c are diagrams to illustrate the fault area determination processing method by fault area judgement circuit 20 in FIG. 1; 
     FIG. 3 is a diagram to illustrate the fault area determination operation of excision circuit 23 by the projection method; 
     FIG. 4 is a circuit diagram of one example of excision circuit 23; 
     FIG. 5 is a block diagram of a prior art surface inspection system; and 
     FIG. 6 is a diagram to illustrate the operation of the prior art shown in FIG. 5. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, the embodiments of this invention will be described below. 
     FIG. 1 is a block diagram showing the composition of a surface inspection system according to an embodiment of this invention. In FIG. 1, 10 is an image memory which stores images of specified areas of sheet material 1 detected by detector 3. A fault area judgement circuit 20 as the fault area judgement means is provided with a binary imaging circuit 21 which makes binary images from the output images of detector 3, a grouping judgement circuit 22 which judges faults composed of multiple parts as clusters from these binary image patterns, and a segmentation circuit 23 which determines the fault areas by judging the separations of fault areas judged as clusters. 30 is a recognition circuit as the recognition means which recognizes the types and grades of the faults contained in the determined fault areas almost the same as prior art recognition circuit 7 does. The design is that, when a fault area is determined by fault area judgement circuit 20, an image of the specified area is outputted to recognition circuit 30 from image memory 10. Image memory 10 also stores a fresh detected image from detector 3. 
     Next, the fault area determination operation by fault area judgement circuit 20 is described using FIG. 2. Binary imaging circuit 21 obtains a binary image by discriminating the input image at an appropriate judgement level (FIG. 2(a)). Grouping judgement circuit 22 judges the &#34;clustering&#34; of the parts which compose each fault by executing an expansion processing or an enlargement processing on that binary image pattern. Specifically, it links a fault to a neighbouring fault by expanding (enlarging) that fault up to a specified area around the fault point. By this means, faults A, B, C and D in FIG. 2(b) become cluster faults composed of the areas surrounded by the dotted lines. Segmentation circuit 23 determines each fault area by judging the separation of the cluster faults judged by grouping judgement circuit 22. It performs, for instance, a labelling process as that determination process. This is, the judging of the connectivity of each pixel which composes the fault and assigning a label to each fault area. This discrimination method is comparatively lengthy because the processing is complex. As opposed to this, as an alternative processing method, it is possible to adopt the projection method which determines the fault areas from projections in the running direction and the width direction of sheet material 1. This method is comparatively simple and speedy. 
     This projection method is described below. In FIG. 3, A, B, C and D are cluster faults judged by grouping judgement circuit 22. FIG. 4 is a circuit diagram of one example of segmentation circuit 23. In FIG. 4, a shift register 31 is provided with a plurality of memories 31M of the number corresponding to the number of the pixels of running sheet material 1 in the width direction. Shift register 31 receives an output S of grouping judgement circuit 22 through a logic OR circuit 39 and stores &#34;1&#34; (fault signal) in memories 31M corresponding to pixels included in the cluster fault. The output of shift register 31 is fed back to an input of logic OR circuit 39. Logical sum (OR) of output S of grouping judgement circuit 22 and the output of shift register 31 is inputted to shift register 31. Thus, shift register 31 accumulates &#34;1&#34; (fault signal) in memories 31M for each scanning. Shift register 31 repeats this memory operation every time of scanning thereby to obtain a projection Px of the cluster fault in the width direction. A flip-flop 35 also receives output S of grouping judgement circuit 22, and stores &#34;1&#34; when the scanning is executed on the cluster fault. Thus, flip-flop 35 outputs a projection Py of the cluster fault in the running direction of sheet material 1. 
     A first counter 32 counts the number of pixels in the width direction from the end portion of running sheet material 1 as a starting point, when the scanning is started. Next, at a cut-line (falling point) of projection Py in the running direction, for example at a time T1, projection Px1 in the width direction is read out. The values of first counter 32 at the rising and falling points of projection Px1, such as values X11, X12, X13 and X14 are stored in a first memory 34 through a first gate circuit 33. 
     A second counter 36 counts the number of pixels in the running direction from the tip portion of running sheet material 1 as a starting point. At rising and falling points of projection Py in the running direction, the values of projection Py, for example Y11 and Y12, are stored in a second memory 38 through a second gate circuit 37. 
     Thus, the fault area for the cluster fault is determined. As cluster fault A, for example, it is located in a fault area Sa between addresses X11 and X12 in the width direction and between addresses Y11 and Y12 in the running direction. Cluster fault B is located in a fault area Sb between addresses X13 and X14 in the width direction and between addresses Y11 and Y12 in the running direction. 
     Based on projection Px2 at a time T2, which is a next cut-line of projection Py and rising and falling points of projection Py in the running direction, fault areas Sc and Sb are determined for cluster faults C and D, respectively. 
     As described above, fault areas Sa, Sb, Sc and Sd which respectively surround cluster faults A, B, C and D can be obtained from these running direction and width direction projections Py and Px in segmentation circuit 23. 
     When using this embodiment as stated above, even if a single fault is divided into several parts and, moreover, each part has a complex shape, the judgement of a cluster fault by the expansion processing or the like, and the separation of cluster faults by projection method, are executed. By this means, the fault area is determined by a simple process and almost as speedily as in real time. Furthermore, the types and grades of the fault contained in that fault area can be recognized. 
     As described above, the surface inspection system according to this invention is provided with a detection device which detects an image of a surface fault in a running sheet material, a fault area judgement device which determines a fault area including a cluster fault composed of the same type of fault points by judging the fault distribution state from the surface fault images which have been detected, and a recognition device which recognizes the type and grade of the cluster fault contained in the fault area which have been determined. 
     Therefore, in a case when there are surface faults with various configurations on the sheet material and those surface faults are composed of multiple fault parts, the types and grades of the faults can be correctly and speedily recognized. 
     Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.