Automatic visual inspection system
First Claim
1. A process for producing a binary map of an object having edges comprising:
- (a) sampling the object to obtain grey level values at discrete sampling points for producing a digital grey scale image of the object with a given resolution; and
(b) processing the grey scale image to produce a digital map of the object having a resolution greater than said given resolution, such that the location of an edge of the object in the higher resolution map is related by a scale factor to the location of the corresponding edge in the object independently of the relative location of said edge with respect to the locations of said discrete sampling points.
1 Assignment
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Accused Products
Abstract
A binary map of an object having edges is produced by first producing a digital grey scale image of the object with a given resolution, and processing the grey scale image to produce a binary map of the object at a resolution greater than said given resolution. Processing of the grey scale image includes the step of convolving the 2-dimensional digital grey scale image with a filter function related to the second derivative of a Gaussian function forming a 2-dimensional convolved image having signed values. The location of an edge in the object is achieved by finding zero crossings between adjacent oppositely signed values. Preferably, the zero crossings are achieved by an interpolation process that produces a binary bit map of the object at a resolution greater than the resolution of the grey scale image. The nature of the Gaussian function whose second derivative is used in the convolution with the grey scale image, namely its standard deviation, is empirically selected in accordance with system noise and the pattern of the traces on the printed circuit board such that the resulting bit map conforms as closely as desired to the lines on the printed circuit board.
36 Citations
98 Claims
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1. A process for producing a binary map of an object having edges comprising:
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(a) sampling the object to obtain grey level values at discrete sampling points for producing a digital grey scale image of the object with a given resolution; and
(b) processing the grey scale image to produce a digital map of the object having a resolution greater than said given resolution, such that the location of an edge of the object in the higher resolution map is related by a scale factor to the location of the corresponding edge in the object independently of the relative location of said edge with respect to the locations of said discrete sampling points. - View Dependent Claims (2, 3, 4, 21)
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5. A process for producing a binary map of a printed inspecting an electrical circuit board having conductive traces on a surface of a substrate, the processing comprising:
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a) linearly displacing the printed electrical circuit board in a direction perpendicular relative to a linear array of photosensitive detectors, each of which produces an output that is functionally related to the brightness of the field an elemental area of the electrical circuit viewed by the detector, each elemental area being associated with a measured data point and each said measured data point being mutually spaced apart generally by a predetermined sampling distance;
b) applying the output of the detectors to a memory having cells for storing, in the cells thereof, a two-dimensional digital grey gray scale image of the printed electrical circuit board , said image having a predetermined pixels size corresponding to said measured data points;
a) convolving the stored image with a two-dimensional, Laplacian of a Gaussian function for producing a convolved digital image having a signed value for each cell of said memory;
d c) interpolating between adjacent values of opposite sign for obtaining from said two dimensional digital gray scale image a binary bit map of said printed electrical circuit board with a pixel size , said map formed of digital map elements, wherein at least some non-adjacent digital map elements represent portions of the electrical circuit that are separated by a distance that is smaller than said predetermined size sampling distance; and
e) storing said binary bit map in a memoryd) employing said map to detect defects in said electrical circuit. - View Dependent Claims (6, 7, 8)
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9. Apparatus for producing a binary map of an object having edges comprising:
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(a) means for mounting said object so that it is linearly displaceable;
(b) a light source for illuminating said object;
(c) a digital memory;
(d) an electro-optical system responsive to displacement of said object for sampling the light therefrom at discrete sampling points for producing a grey scale image of the object with a given resolution;
(e) means for storing said grey scale image in said memory; and
(f) processing means for converting the image in said memory into a binary map of said object having a resolution greater than said given resolution, said processing means being constructed and arranged to cause the location of edges of the object in the higher resolution map to be related by a scale factor to the location of the corresponding edges in the object independently of the relative locations of the edges of the object with respect to said discrete sampling points. - View Dependent Claims (10, 11)
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12. A process for reducing sensitivity to focusing errors in the binary map of an object having edges comprising:
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(a) producing a digital grey scale image of an object by sampling at discrete sampling points, said last mentioned image having a given resolution; and
(b) processing the grey scale image to produce a binary map of the object at a resolution greater than said given resolution, such that the location of edges of the object in the higher resolution map is independent of the location of edges of the object relative to the sampling points.
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13. A process for increasing the amount of light in a camera producing a binary map of an object having edges comprising:
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(a) producing a digital grey scale image of the object by sampling at discrete sampling points, said last mentioned image having a given resolution; and
(b) processing said grey scale image to produce a binary map of the object at a resolution greater than said given resolution, such that the location of edges of the object in the higher resolution map is independent of the location of the edges relative to the sampling points.
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14. Apparatus for producing a binary map of an object having edges comprising:
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(a) means for mounting said object so that it is linearly displaceable;
(b) a light source for illuminating said object;
(c) a digital memory;
(d) an electro-optical system responsive to displacement of said object for sampling the light therefrom at discrete sampling points for producing a grey scale image of the object with a given resolution;
(e) means for storing said grey scale image in said memory; and
(f) processing means for converting the image in said memory into a binary map of said object having a resolution greater than said given resolution, said processing means being constructed and arranged to cause the location of edges of the object in the higher resolution map to be related by a scale factor to the location of the corresponding edges in the object independently of the relative locations of the edges of the object with respect to said discrete sampling points;
(g) wherein said electro-optical system is constructed and arranged to produce a stream of data representative of a scanned two-dimensional grey-scale image of the object, and said processing means includes a plurality of convolver modules, and means for applying said stream serially to said modules which are constructed and arranged to produce a two-dimensional convolution of the grey-scale image. - View Dependent Claims (15, 16, 17, 18, 19)
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20. A convolver module for convolving an input stream of data comprising:
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a) delay means for delaying said input stream and producing a delayed stream;
b) an adder for adding the input stream to the delayed stream and producing an added stream;
c) a shift register to which the added stream is applied for producing a shifted stream; and
d) means for combining the shifted stream with the added stream and producing an output stream representative of a two-dimensional convolution of the input stream with a boxcar function.
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22. A process for producing a binary map of an object having edges comprising:
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a) scanning the object to produce a digital grey scale image of the object with a given resolution, said grey scale image having pixels of predetermined size; and
b) processing the grey scale image to produce a digital map of the object having a resolution greater than said given resolution such that the location of edges in the grey scale image digital map are substantially independent of the relationship between the edges of the object and the direction of scanning. - View Dependent Claims (30, 31, 32, 33, 34)
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23. Apparatus for producing a binary map of an object having edges comprising:
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(a) means for mounting said object so that it is linearly displaceable;
(b) a light source for illuminating said object;
(c) a digital memory;
(d) an electro-optical system responsive to displacement of said object for converting the light therefrom to a grey scale image of the object with a given resolution;
(e) processing means for converting the image in said memory into a binary map of said object having a resolution greater than a given resolution, and having pixels of a predetermined size; and
(f) said processing means being constructed and arranged to cause the relationship between the edges of the pixel of the grey scale image to be independent of the actual edges of the object.
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24. Apparatus for detecting an edge of an object comprising:
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(a) scan means to scan the object along a scan line that intersects said edge for obtaining a plurality of grey scale level values at discrete sampling points; and
(b) processing means to process said values for locating the intersection of said scan line with said edge such that the location of said intersection at or intermediate said sampling points is generally independent of the relationship between said sampling points and said edge. - View Dependent Claims (25, 26, 27, 28, 29)
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35. A method for detecting an edge of an object comprising the steps of:
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(a) scanning the object along a scan line that intersects said edge for obtaining a plurality of grey scale level values at discrete sampling points; and
(b) processing the values of the scan line for locating the intersection of said scan line with said edge such that the location of said intersection at or intermediate said sampling points is generally independent of the relationship between said sampling points and said edge. - View Dependent Claims (36, 37, 38, 39, 40)
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41. A process for producing a binary map of an object having edges comprising:
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(a) scanning the object in a given direction to obtain grey level values at discrete sampling points for producing a digital grey scale image of the object with a given resolution; and
(b) processing the grey scale image to produce a digital map of the object having a resolution greater than said given resolution, such that the location of an edge of the object in the higher resolution map is independent of the relative location of said edge with respect to the locations of said discrete sampling points, and of the direction of scanning. - View Dependent Claims (42, 43, 44)
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45. A process for producing a binary map of an object having edges, the process comprising:
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a) displacing the object relative to a linear array of photosensitive detectors each of which produces an output that is functionally related to the brightness of the field viewed by the detector;
b) applying the output of the detectors to a memory for storing, in the cells thereof, a two-dimensional digital grey scale image of the object, said image having a predetermined pixel size;
c) convolving the stored image with a filter function that approximates the second derivative of a Gaussian function for producing a convolved digital image having a signed value for each cell of said memory;
d) interpolating between adjacent values of opposite sign for obtaining a binary bit map of said object with a pixel size smaller than said predetermined size; and
e) storing said binary bit map in a memory. - View Dependent Claims (46, 47, 48, 49)
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50. Apparatus for producing a binary map of an object having edges comprising:
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(a) means for scanning the object in a given direction to obtain grey level values at discrete sampling points for producing a digital grey scale image of the object with a given resolution; and
(b) means for processing the grey scale image to produce a digital map of the object having a resolution greater than said given resolution, such that the location of an edge of the object in the higher resolution map is independent of the relative location of said edge with respect to the locations of said discrete sampling points, and of the direction of scanning. - View Dependent Claims (51, 52, 53, 64, 65)
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54. Apparatus for producing a binary map of inspecting an object having edges comprising:
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a) a linear array of photosensitive detectors each of which produces an output that is functionally related to the brightness of the field a corresponding elemental area on the object viewed by the detector, wherein said elemental areas are a predetermined elemental area size;
b) means for relatively displacing the object and the array;
c) means for applying the output of the detectors to a memory for storing, in the cells thereof, a two-dimensional digital grey gray scale image of the object, said image comprising pixels having a predetermined pixel size;
d) means for convolving the stored image with a filter function that approximates the second derivative of a Gaussian function for producing a convolved digital image having a signed value for each cell of said memory; d) interpolating between adjacent values of opposite sign circuitry for obtaining a binary bit map of said object with a pixel size from said two dimensional digital gray scale image, said map being formed of digital map elements, wherein each digital map element is associated with a corresponding portion of said electrical circuit and at least some non-adjacent portions are separated by a distance that is smaller than said predetermined elemental area size; and
e) a memory for storing said binary bit map processing circuitry employing said map to detect defects in said electrical circuit. - View Dependent Claims (55)
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56. Apparatus for producing a binary map of an object having edges comprising:
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a) a light source for illuminating said object;
b) an electro-optical system for sampling light from said object;
c) means for effecting relative movement between said object and said system;
d) means responsive to said relative movement for sampling light from discrete sampling points on the object and producing a grey scale image of the object with a given resolution;
e) means for storing said grey scale image in a digital memory; and
f) processing means for converting the image in said memory into a binary map of said object having a resolution greater than said given resolution, said processing means being constructed and arranged to cause the location of the edges of the object in the higher resolution map to be related by a scale factor to the location of the corresponding edges in the object independently of the relative locations of the edges of the object with respect to said discrete sampling points;
g) wherein said electro-optical system produces a stream of data representative of a scanned two-dimensional grey-scale image of said object, and said processing means includes a convolver, and means for applying said stream serially to said convolver which is responsive to produce a two-dimensional convolution of the grey-scale image. - View Dependent Claims (57, 58)
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59. A process for producing a binary map of an object having edges, the process comprising:
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a) effecting relative displacement between said object and a linear array of photosensitive detectors, each of which produces an output that is functionally related to the brightness of the field viewed by the detector;
b) applying the output of the detectors to a memory having cells for storing, in the cells thereof, a two-dimensional digital grey scale image of the printed circuit board, said image having a predetermined pixel size;
c) convolving the stored image with a filter function that approximates the second derivative of a Gaussian function for producing a convolved digital image having a signed value for each cell of said memory;
d) interpolating between adjacent values of opposite sign for obtaining a binary bit map of said object with a pixel size smaller than said predetermined size; and
e) storing said binary bit map in a memory. - View Dependent Claims (60, 61, 62, 63)
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66. A process for producing a binary map of an object having edges comprising:
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(a) sampling the object to obtain grey level values at discrete sampling points for producing a digital grey scale image of the object with a given resolution;
(b) convolving the grey scale image with a filter function to produce a digital map of the object having a resolution greater than said given resolution; and
(c) selecting the filter function such that edges in the digital map corresponding to edges in the object are substantially independent of the location of the sampling points relative to the edges in the object.
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67. Apparatus for producing a binary map of an object having edges comprising:
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(a) means for mounting said object so that it is linearly displaceable;
(b) a light source for illuminating said object;
(c) a digital memory;
(d) an electro-optical system responsive to displacement of said object for sampling the light therefrom at discrete sampling points for producing a grey scale image of the object with a given resolution;
(e) means for storing said grey scale image in said memory; and
(f) means for convolving the image in said memory with a filter function to produce a binary map of said object having a resolution greater than said given resolution, said filter function causing edges in the binary map corresponding to edges in the object to be substantially independent of the location of the sample points relative to the edges in the object.
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68. A process for producing a map of a surface of an electrical circuit comprising:
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forming a two-dimensional grey scale image of a surface of an electrical circuit from data elements acquired by an array of detectors displaced with respect to the surface, wherein ones of said detectors each view corresponding ones of first elemental areas on said surface;
modifying at least some data elements of said two-dimensional grey scale image to provide a plurality of modified data elements; and
forming a map of said electrical circuit from digital map elements that are formed by interpolating between selected modified data elements, wherein said digital map elements correspond to second elemental areas on said surface of the electrical surface that are smaller than said first elemental areas. - View Dependent Claims (69, 70, 71, 72, 73, 74, 75, 76, 77, 78)
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79. A process for analyzing conducting and non-conducting regions on a surface of an electrical circuit comprising:
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forming a two dimensional grey scale image of a surface of an electrical circuit, said image having pixels, wherein each pixel corresponds to one of a plurality of elemental areas of a first size on the surface;
processing said two dimensional grey scale image to form a map of said surface, said map including digital map elements representing second elemental areas on the surface, said second elemental areas being smaller than said first elemental areas; and
thenemploying said map to detect defects in said electrical circuit. - View Dependent Claims (80, 81, 82)
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83. A method for automated optical inspection of an electrical circuit, comprising:
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producing a digital grey scale image of the electrical circuit with a given gray scale image spatial resolution, said given gray scale image spatial resolution being related to the size of the first elemental areas of said electrical circuit viewed by ones of pixels in an optical detector;
processing the grey scale image to produce a digital map of the electrical circuit, said digital map having a digital map spatial resolution which is greater than said given gray scale image spatial resolution; and
analyzing the digital map to detect defects in said electrical circuit. - View Dependent Claims (84, 85, 86, 87, 88, 89, 90, 91, 92, 93)
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94. A method for manufacturing an electrical circuit, comprising:
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(a) depositing at least one conductive member on a surface of an electrical circuit substrate;
(b) sampling the substrate to obtain grey level values at discrete sampling points for producing a digital grey scale image of the substrate with a given resolution;
(c) processing the grey scale image to produce a digital map of the substrate having a resolution greater than said given resolution, such that the location of an edge on the substrate in the higher resolution map is related by a scale factor to the location of the corresponding edge on the object independently of the relative location of said edge with respect to the locations of said discrete sampling points; and
(d) analyzing said digital map to detect defects in said electrical circuit substrate.
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95. A method for manufacturing an electrical circuit, comprising:
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(a) depositing at least one conductive member on a surface of an electrical circuit substrate;
(b) displacing the electrical circuit substrate relative to a linear array of photosensitive detectors, each of which produces an output that is functionally related to the brightness of an elemental area of the electrical circuit substrate viewed by the detector, each elemental area being associated with a measured data point and each said measured data point being mutually spaced apart generally by a predetermined sampling distance;
(c) applying the output of the detectors to a memory having cells for storing, in the cells thereof, a two dimensional digital grey scale image of the electrical circuit substrate, said image having pixels corresponding to said measured data points;
(d) obtaining from said two dimensional digital grey scale image a map of said electrical circuit substrate, said map formed of digital map elements, wherein at least some non-adjacent digital map elements represent portions of the electrical circuit that are separated by a distance that is smaller than said predetermined sampling distance; and
(e) employing said map to detect defects in said electrical circuit.
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96. A method for manufacturing an electrical circuit, comprising:
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depositing at least one conductive member on a surface of an electrical circuit substrate;
forming a two-dimensional grey scale image of said surface from data elements acquired by an array of detectors displaced with respect to the surface, wherein ones of said detectors each view corresponding ones of first elemental areas on said surface;
modifying at least some data elements of said two-dimensional grey scale image to provide a plurality of modified data elements;
forming a map of said electrical circuit from digital map elements that are formed by interpolating between selected modified data elements, wherein said digital map elements correspond to second elemental areas on said surface of the electrical circuit that are smaller than said first elemental areas; and
analyzing said map to detect defects in said electrical circuit substrate.
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97. A method for manufacturing an electrical circuit, comprising:
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depositing at least one conductive member on a surface of an electrical circuit substrate;
forming a two-dimensional grey scale image of said surface, said image having pixels, wherein each pixel corresponds to one of a plurality of elemental areas of a first size on the surface;
processing said two dimensional grey scale image to form a map of said surface, said map including digital map elements representing second elemental areas on the surface, said second elemental areas being smaller than said first elemental areas; and
thenemploying said map to detect defects in said electrical circuit.
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98. A method for manufacturing an electrical circuit, comprising:
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depositing at least one conductive member on a surface of an electrical circuit substrate;
producing a digital grey scale image of said surface with a given grey scale image spatial resolution, said given grey scale image spatial resolution being related to the size of first elemental areas of said surface viewed by ones of pixels in an optical detector;
processing the grey scale image to produce a digital map of the surface, said digital map having a digital map spatial resolution which is greater than said given grey scale image spatial resolution; and
analyzing the digital map to detect defects in said electrical circuit.
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Specification