Automatic system and method for inspecting hole quality
First Claim
1. A method for inspecting the perimeter smoothness of a nominally round opening in an object comprising the steps of:
- forming a two dimensional representation of the opening, said representation including two dimensional array of uniformly spaced pixels of a size substantially smaller than the size of said opening with each pixel having a range of digital values which indicate the presence, partial presence, or absence of said opening at the spatial position represented by that pixel, said array of pixels representing said opening as a connected group of pixels having first values at one end of said range surrounded by pixels having second values at the other end of the range, with the boundary therebetween representing the perimeter of said opening; and
examining the values of the pixels in one or more clusters surrounding said opening, each said cluster being composed of a group of several adjacent pixels arranged in a pattern with its center at said boundary, and determining that said perimeter is smooth at the location of a particular cluster if the number of pixels within said cluster having said first value is close to the number of pixels within said cluster having said second value, and wherein said perimeter is not smooth at said location if the number of pixels within said cluster having said first value is greatly disproportionate to the number of pixels within said cluster having said second value.
1 Assignment
0 Petitions
Accused Products
Abstract
An automatic inspection system for inspecting holes in a mask including carriage means 30, illumination means 44, optical means 48, photosensitive detector means 46, and signal processing means 56. The mask 34 to be inspected is positioned by the carriage means in a horizontal plane. The optical means projects a focused image of a portion of the mask onto the photosensitive detector means. Photodiodes in the detector means are responsive to light from the illumination means that is transmitted through the holes in the mask. The signal processing means scans the outputs of the photodiodes and stores in memory a digital representation of the mask. The signal processing means performs inspection measurements and comparison tests. A smoothness checker circuit 240 measures the local radius of curvature of each hole at several places and compares the measurements to predetermined curvature limits to detect nicks and sharp protrusion defects. An area check circuit 246 measures the area of the hole and compares it to predetermined area limits. A diameter check circuit 244 measures the diameter of the hole in two dimensions and compares it to predetermined diameter limits. If either the hole area or the hole diameter is outside their respective limits, a hole size defect is indicated. Means are also provided for locating completely blocked, mispositioned or unintended holes by comparing detected information to a data base.
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Citations
28 Claims
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1. A method for inspecting the perimeter smoothness of a nominally round opening in an object comprising the steps of:
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forming a two dimensional representation of the opening, said representation including two dimensional array of uniformly spaced pixels of a size substantially smaller than the size of said opening with each pixel having a range of digital values which indicate the presence, partial presence, or absence of said opening at the spatial position represented by that pixel, said array of pixels representing said opening as a connected group of pixels having first values at one end of said range surrounded by pixels having second values at the other end of the range, with the boundary therebetween representing the perimeter of said opening; and examining the values of the pixels in one or more clusters surrounding said opening, each said cluster being composed of a group of several adjacent pixels arranged in a pattern with its center at said boundary, and determining that said perimeter is smooth at the location of a particular cluster if the number of pixels within said cluster having said first value is close to the number of pixels within said cluster having said second value, and wherein said perimeter is not smooth at said location if the number of pixels within said cluster having said first value is greatly disproportionate to the number of pixels within said cluster having said second value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. 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:
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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. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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27. Inspection apparatus for inspecting the area, diameter, and surface smoothness of nominally round openings in an object comprising:
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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. - View Dependent Claims (28)
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Specification