Automatic system and method for inspecting hole quality

A method of inspecting one or more round openings in an object wherein each said opening is of the same nominal size, said method comprising the steps of:

• forming a two dimensional representation of at least a portion of the object, said representation including a two-dimensional array of rows and columns of uniformly spaced apart pixels of a size substantially smaller than said openings with each pixel having a first digital value to indicate the presence of an opening at the spatial position of that pixel, or a second digital value to indicate the absence of an opening thereat, said array of pixels representing each opening as a connected group of pixels having said first value surrounded by pixels having said second value, with the boundary therebetween representing the perimeter of said opening;
• storing said representation in a pixel memory;
• scanning said pixel memory by accessing clusters of pixels therein one cluster at a time and summing the values of the pixels in each cluster as that cluster is accessed, said scanning step beginning at one corner of said array of pixels and proceeding to advance in the direction of the rows of pixels, each said cluster being composed of portions of several adjacent rows and columns of pixels arranged in a symmetrical pattern;
• setting a smoothness defect flag in a chord memory array whenever an accessed cluster is positioned such that the center of said cluster is located at a boundary of one of said openings and the number of pixels within said cluster having said first value is a predetermined relationship to the number of pixels within said cluster having said second value;
• and
• reporting a smoothness defect for an opening if any smoothness defect flags are set for that opening.

Inspection apparatus for inspecting the area, diameter, and surface smoothness of nominally round openings in an object comprising:

• carriage means for supporting the object to be inspected and for simultaneously moving such object along an inspection path;
• illumination means for illuminating portions of said object as it is moved along said path;
• optical means for focusing an image of said object at a focal plane;
• photosensitive detector means disposed at said focal plane at right angles to said inspection path for generating sensor signals corresponding to said image of said object incident thereon;
• signal processing means for processing said sensor signals to inspect said openings, said signal processing means including memory means for storing said sensor signals, smoothness checking means for constructing a digital representation of portions of said object from said sensor signals and for measuring the radius of curvature of said openings, and for comparing said measured radius of curvature to an inspection standard, diameter checking means for measuring the diameters of said openings from said digital representation and for comparing said measured diameters to an inspection standard, area checking means for measuring the area of said openings from said digital representation and for comparing said measured areas to an inspection standard.