Methods and apparatus for optically determining the acceptability of products
First Claim
1. The method of determining whether or not a surface of an object has substantially the same appearance as the corresponding surface of a plurality of training objects, said method comprising the steps of:
- for each training object, (a) forming a two-dimensional image of said surface, (b) subdividing said two-dimensional image into a plurality of pixels, (c) digitizing each of said pixels by associating with each pixel an initial digital value proportional to an optical characteristic of the associated pixel, (d) edge detecting said initial digital values by processing said initial digital values to produce output digital values such that initial digital values associated with pixels at or near substantial changes in initial digital value are relatively emphasized to produce the associated output digital values, while initial digital values associated with all other pixels are relatively de-emphasized to produce the associated output digital values, and (e) binarizing each of said output digital values by associating a first binary value with each of said output digital values which is on one side of a first predetermined threshold value and by associating a second binary value with each of said output digital values which is on the other side of said first predetermined threshold value;
associating a discriminant value with each of said pixels, each discriminant value being chosen so that, for each training object, the dot product of the discriminant values and the binary values is approximately a predetermined nonzero constant value;
repeating steps (a)-(e) for said object; and
comparing the dot product of said discriminant values and the binary values for said object to said predetermined nonzero constant value.
1 Assignment
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Accused Products
Abstract
The appearance of a product is determined to be acceptable or unacceptable by computing a discriminant function or image from a plurality of two-dimensional images of products of the kind to be inspected. A two-dimensional image of the product is then formed and processed using the discriminant image to produce an output value which can be compared to a predetermined value used in computing the discriminant image. If the output value deviates from the predetermined value by more than a predetermined amount, the product has been found to have an unacceptable appearance.
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Citations
34 Claims
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1. The method of determining whether or not a surface of an object has substantially the same appearance as the corresponding surface of a plurality of training objects, said method comprising the steps of:
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for each training object, (a) forming a two-dimensional image of said surface, (b) subdividing said two-dimensional image into a plurality of pixels, (c) digitizing each of said pixels by associating with each pixel an initial digital value proportional to an optical characteristic of the associated pixel, (d) edge detecting said initial digital values by processing said initial digital values to produce output digital values such that initial digital values associated with pixels at or near substantial changes in initial digital value are relatively emphasized to produce the associated output digital values, while initial digital values associated with all other pixels are relatively de-emphasized to produce the associated output digital values, and (e) binarizing each of said output digital values by associating a first binary value with each of said output digital values which is on one side of a first predetermined threshold value and by associating a second binary value with each of said output digital values which is on the other side of said first predetermined threshold value; associating a discriminant value with each of said pixels, each discriminant value being chosen so that, for each training object, the dot product of the discriminant values and the binary values is approximately a predetermined nonzero constant value; repeating steps (a)-(e) for said object; and comparing the dot product of said discriminant values and the binary values for said object to said predetermined nonzero constant value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. Apparatus for determining whether or not a surface of an object has substantially the same appearance as the corresponding surface of a plurality of training objects comprising:
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means for, for each training object, (a) forming a two-dimensional image of said surface, (b) subdividing said two-dimensional image into a plurality of pixels, (c) digitizing each of said pixels by associating with each pixel an initial digital value proportional to an optical characteristic of the associated pixel, (d) edge detecting said initial digital values by processing said initial digital values to produce output digital values such that initial digital values associated with pixels at or near substantial changes in initial digital value are relatively emphasized to produce the associated output digital values, while initial digital values associated with all other pixels are relatively de-emphasized to produce the associated output digital values, and (e) binarizing each of said output digital values by associating a first binary value with each of said output digital values which is on one side of a first predetermined threshold value and by associating a second binary value with each of said output digital values which is on the other side of said first predetermined threshold value; means for associating a discriminant value with each of said pixels, each discriminant value being chosen so that, for each training object, the dot product of the discriminant values and the binary values is approximately a predetermined non-zero constant value; means for repeating functions (a)-(e) with respect to said object; and means for comparing the dot product of said discriminant values and the binary values for said object to said predetermined nonzero constant value. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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31. The method of determining whether or not an image to be inspected has substantially the same appearance as a plurality of training images, said method comprising the steps of:
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digitizing each training image i to produce corresponding training image data I.sup.(i) ; converting said training image data to a plurality of orthogonal eigenimages given by the equation;
##EQU17## where n is the total number of training images and the transformation matrix B is orthogonal;computing a discriminant image F from a truncated linear combination of said eigenimages given by the equation;
##EQU18## where s is an integer less than n selected as a value which gives the minimum value for V(s) in the equation;
##EQU19## where ai is a nonzero constant for all good training images and zero for any bad training images, and where the values Cj are given by the equation;
##EQU20## where the eigenvalues γ
j are the diagonal elements of a matrix G given by the equation AB=BG, where A is the real, symmetric matrix given by the dot product of every possible training image pair, and the transformation matrix B, is such that BB+ =B+ B=1;digitizing said image to be inspected; forming the dot product of said discriminant image and said digitized image to be inspected; and comparing said dot product to a predetermined reference value. - View Dependent Claims (32, 33, 34)
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Specification