Inspection method using unique templates and histogram analysis
First Claim
1. A method for inspecting products which may have defects or marks and move on a production line, with the use of a sensor and a processing unit with a memory, comprising:
- providing and saving in said memory a computer-generated artificial template image with a plurality of preselected gray levels;
creating a histogram vector of said template image;
creating a product image by sensing one of said products with said sensor,said product image comprising a multiplicity of pixels with intensity levels expressed as respective gray levels;
modifying said product image to produce a modified product image by increasing the value of said gray levels of said product image by adding a constant value to all of said respective gray levels of said product image so as to make said gray levels of said modified product image higher than said grey levels of said template; and
inspecting said product by superimposing said template image onto said modified product image, thereby creating a superposed image.
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Abstract
A technique for detecting defects in stationary products or in products moving on a production line (102, FIG. 12) by analyzing their images uses a matrix or line-scan camera (104, FIG. 12) for taking images of products (102). The product'"'"'s dimensions are measured with accuracy and the sizes and positions of their surface defects are determined. The technique is much faster and more accurate than current techniques and is based on an analysis of the histogram of the full image (C, FIG. 2). A carefully selected template image (A, FIG. 1) is created and saved in the memory of a computer (106, FIG. 12). The method also includes the steps of: creating and saving a histogram vector of the template image; loading look-up tables with a shifting and quantizing function for the image gray levels; saving a product image in memory to be superposed onto template image (FIG. 1); creating and saving a histogram vector of the result superposed image; analyzing the resulting histograms, i.e., finding discontinuations, changes the values of gray levels, appearance of new gray levels, etc. This results in the detection of product dimensions or surface defects and allows deciphering of product codes.
52 Citations
29 Claims
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1. A method for inspecting products which may have defects or marks and move on a production line, with the use of a sensor and a processing unit with a memory, comprising:
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providing and saving in said memory a computer-generated artificial template image with a plurality of preselected gray levels; creating a histogram vector of said template image; creating a product image by sensing one of said products with said sensor, said product image comprising a multiplicity of pixels with intensity levels expressed as respective gray levels; modifying said product image to produce a modified product image by increasing the value of said gray levels of said product image by adding a constant value to all of said respective gray levels of said product image so as to make said gray levels of said modified product image higher than said grey levels of said template; and inspecting said product by superimposing said template image onto said modified product image, thereby creating a superposed image. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. A method for inspecting products which may have defects or marks and move on a production line, with the use of a sensor and a processing unit with a memory, comprising:
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providing and saving in said memory a template image with a plurality of preselected gray levels; creating a histogram vector of said template image; creating a product image comprising a multiplicity of pixels with intensity levels expressed as respective gray levels; and modifying said product image to provide a modified product image by quantizing said gray levels of said product image, said quantizing being performed by converting said gray levels of said product image to a gray level which is higher than the highest one of said gray levels of said template; and inspecting said product by superimposing said template image onto said modified product image, thereby creating a superposed image. - View Dependent Claims (29)
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Specification