Chipping detection system and method

Claim 1

A chipping defect detection system for detecting a chipping defect produced at a boundary portion of an object, said object being formed of a regular shape having a boundary portion including a straight-line portion which is approximated by a straight line, comprising: image pickup means for sensing an image of the object and for providing an electrical image signal representing said image; image memory means for storing said electrical image signal as a two-dimensional image detected by said image pickup means; boundary coordinate detecting means for detecting boundary coordinates of said image; including boundary direction detecting means for successively detecting boundary directions along boundary points of said boundary portion by pattern-matching between an image portion of said two-dimensional image and a plurality of dictionary patterns which show tracing directions of individual boundary points of a reference pattern; said tracing directions indicating tracing direction changes of said reference pattern boundary points; said dictionary patterns being generated by a pattern generator; by successively tracing boundary directions detected by said boundary direction detecting means and storing detected boundary coordinates as a matrix in a boundary coordinate table; means for setting a constant boundary length equal to 2k of a chipping defect to be detected, said boundary length being defined in part by end points A and C, for detecting a chipping defect on said straight line or in a corner of said object through a single operation; means for reading out 2k+1 boundary coordinates from said boundary coordinate table; for variably selecting a variable intermediate point B; and for calculating one of a deviation D 11 , 12 of said point B from a straight line between points A and C, and a crossing angle Θ 11 , 12 for a straight line between points A and B and a straight line between points B and C, for each triangle of a total of (2k-1) triangles formed from possible points A, C and B, wherein l 1 is the distance from A to B, l 2 is the distance from C to B, and l 1 and l 2 are positive integers satisfying the relation l 1 +l 2 =2k, point B being selected to vary l 1 and l 2 ; first means for calculating a minimum value D p of said deviation D 11 , 12 when said reading-out means calculates the deviation D 11 , 12, and for calculating a value Θ p of said crossing angle Θ 11 , 12 when said reading-out means calculates the crossing angle Θ 11 , 12 for said 2k-1 triangles; second means for calculating a center point deviation D k when said reading-out means calculates the deviation D 11 , 12, and for calculating a center point angle Θ k when said reading-out means calculates the crossing angle Θ 11 , 12, for a point B satisfying the relation l 1 =l 2 =k; means for repeating the calculations performed by said first and second calculating means by reading out boundary coordinates from said boundary coordinate table; means for detecting a chipping defect size by obtaining differences of values calculated by said first and second calculating means from corresponding values of a reference object; and judgment means for judging presence or absence of a chipping defect on the basis of the chipping defect size detected by said chipping defect size detecting means.