Methods and apparatus for optically determining the acceptability of products
First Claim
Patent Images
1. A method of determining whether or not a product has an acceptable appearance comprising the steps of:
- generating a plurality of reference images from reference products, the image generation for each reference product including the steps of acquiring a two-dimensional image of the product surface, subdividing the acquired image into a plurality of sub-areas, and assigning a value to each sub-area dependent on the optical characteristic of the sub-area;
deriving from the images acquired from the reference products a discriminant image;
setting a threshold level on the amount by which a dot product of the discriminant image and an actual product whose appearance is to be determined may deviate from a reference dot product of the discriminant image and an acceptable product image;
generating an image foe an actual product by repeating the steps for generating each reference image; and
comparing the dot product of the discriminant image and the acquired product image to the reference dot product;
whereby images of actual products whose dot product deviations from the reference dot product are greater than the threshold level are determined to have an unacceptable appearance.
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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.
29 Citations
48 Claims
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1. A method of determining whether or not a product has an acceptable appearance comprising the steps of:
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generating a plurality of reference images from reference products, the image generation for each reference product including the steps of acquiring a two-dimensional image of the product surface, subdividing the acquired image into a plurality of sub-areas, and assigning a value to each sub-area dependent on the optical characteristic of the sub-area; deriving from the images acquired from the reference products a discriminant image; setting a threshold level on the amount by which a dot product of the discriminant image and an actual product whose appearance is to be determined may deviate from a reference dot product of the discriminant image and an acceptable product image; generating an image foe an actual product by repeating the steps for generating each reference image; and comparing the dot product of the discriminant image and the acquired product image to the reference dot product;
whereby images of actual products whose dot product deviations from the reference dot product are greater than the threshold level are determined to have an unacceptable appearance. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. Apparatus for determining whether or not a product has an acceptable appearance, characterized by means for generating a plurality of reference images from reference products, the reference image generation means including means for acquiring a two-dimensional image of the reference product surface, and means for sub-dividing the acquired image into a plurality of sub-areas and for assigning to each sub-area a value dependent on the optical characteristic of the sub-area;
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means for deriving from the plurality of reference images a discriminant image; means for setting a threshold level on the amount by which a dot product of the discriminant image and an actual product whose appearance is to be determined may deviate from a reference dot product of the discriminant image and an acceptable product image; means for generating an image for an actual product, the actual product image generating means being operable to generate product images comparable with images generated by the reference product image generating mean; and means for comparing the dot product of the discriminant image and the acquired product image with the reference dot product;
whereby images of actual products whose dot product deviations from the reference dot product are greater than the threshold level are determined to have an unacceptable appearance. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17, 48)
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18. 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 output digital value proportional to an optical characteristic of the associated pixel, and (d) 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)-(d) 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 (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32)
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33. 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 output digital value proportional to an optical characteristic of the associated pixel, and (d) 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; 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)-(d) 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 redetermined nonzero constant value. - View Dependent Claims (34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47)
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Specification