Flaw detection apparatus

• US 5,850,468 A
• Filed: 01/16/1998
• Issued: 12/15/1998
• Est. Priority Date: 04/11/1995
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Kobayashi, Akira, Yokoyama, Haruhiko
• Primary Examiner(s): Au, Amelia
• Assistant Examiner(s): Patel, Jayanti K.
• Application Number:
  US09/008,211
• Time in Patent Office: 333 Days
• Field of Search: 382/108, 382/141, 382/225, 382/288, 348/128, 356/237
• US Class Current: 382/149
• CPC Class Codes: G06T 2207/30164 Workpiece; Machine component
• CPC Class Codes: G06T 7/0006 using a design-rule based approach
• CPC Class Codes: G06T 7/62 of area, perimeter, diameter or volume
• CPC Class Codes: G06T 7/66 of image moments or centre of gravity

Abstract

A flaw detection apparatus detects a flaw formed on an object'"'"'s surface based on a digital image data indicative of said object'"'"'s surface as a group of plural pixels utilizing the image processing technique. An image processor is provided for detecting a direction in which each of group extends to combine a plurality of groups extending in substantially the same direction. The image processor further produces a flaw signal indicating sizes of thus combined groups.

Claims

1. A flaw detection apparatus for detecting a flaw formed on a surface of an object based on a plurality of first digital image data representing said surface as a plurality of first groups of plural pixels, each pixel of each first group being adjacent to each other, said apparatus comprising:

first direction detection means for detecting a direction in which each first group extends based on the axis quadratic moment of each of said first groups by;

a)first calculating the axis quadratic moment of each of said first groups, then

b) assigning a value for the major axis angle of each of said first groups;

first cluster means for combining said first groups that are disconnected and extend in directions different from each other less than a first predetermined degree based on the respective detected axis quadratic moment of each of said first groups and based on said major axis angle of each of said first groups; and

first flaw signal producing means for producing a first flaw signal indicating sizes of said combined groups based on an area of said combined first groups and a rectangular circumscribing area of said combined first groups.

2. A flaw detection apparatus as claimed in claim 1, wherein said first flaw signal producing means comprises:

first flaw coefficient determining means for calculating the area of said combined first groups to determine a first flaw coefficient; and

second flaw coefficient determining means for calculating the rectangular circumscribing area of said combined first groups to determine a second flaw coefficient.

3. A flaw detection apparatus as claimed in claim 2, further comprising reference flaw signal means for providing a reference flaw signal indicative of a flaw range of said first and second flaw coefficients for the detection of the flaw.

4. A flaw detection apparatus as claimed in claim 3, wherein said reference flaw signal means comprises:

digital image signal producing means for producing a second digital image signal indicative of a second flaw on the surface of the object represented as a plurality of second groups of plural pixels;

second direction detection means for detecting a direction in which each second group extends;

second cluster means for combining said second groups extending in directions different from each other less than a second predetermined degree;

third flaw coefficient determining means for calculating an area of said combined second groups to determine a third flaw coefficient;

fourth flaw coefficient determining means for calculating an area of rectangular region circumscribing said combined second groups to determine a fourth flaw coefficient; and

evaluation means for evaluating the distribution of said third and fourth flaw coefficients to determine a second flaw range.

5. A flaw detection apparatus for detecting a flaw formed on a surface of an object based on a digital image data indicative of said surface as a plurality of groups of plural pixels adjacent to each other, said apparatus comprising:

minor axis quadratic moment determining means for obtaining a minor axis quadratic moment of a combination of two of said groups that are disconnected by calculating one minor axis quadratic moment of a combined two groups;

comparator means for comparing said determined minor axis quadratic moment with a predetermined minor axis quadratic moment; and

cluster means for combining said two groups when said determined minor axis quadratic moment is less than said predetermined minor axis quadratic moment.