System and method for automatic optical inspection
First Claim
1. An optical inspection system for detecting faults at potential hole sites of a wire scribed circuit board having a plurality of wires scribed on a substrate, comprising:
- a video camera for receiving images of desired hole sites on said wire scribed circuit board, said video camera converting each image to electrical video signals;
an image storage memory for storing color element values indicative of the chromaticity of a plurality of pixels derived from said electrical video signals;
a panel feature detector receiving said color element values of a pixel to be analyzed from said image storage memory, providing a wire indication when said color element values of said pixel correspond to a wire feature;
a pixel retrieve controller providing command signals to said image storage memory to transmit to said panel feature detector color element values corresponding to predetermined pixels associated with a hole site to be analyzed; and
an open detector circuit receiving said wire indication from said panel feature detector corresponding to said predetermined pixels associated with said hole site, said open detector determining whether an open circuit could occur when said hole site is drilled;
wherein said pixel retrieve controller further comprises an open scan table associated with a hole site having a plurality of corresponding scan lines said open scan table for each said scan line storing boundary values for an open circuit region, where said boundary values are used to derive said command signals.
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Abstract
An optical inspection system for inspecting faults on circuit boards like printed circuit boards and wire scribed circuit boards is disclosed. A video camera for receiving desired images of hole sites on a wire circuit board is provided. The camera converts each image to electrical video signals. A frame grabber converts electrical video signals to a plurality of pixels and stores information representing color element values contained in each of the pixels. A panel feature detector receives the color element values of the pixel that has to be analyzed and provides a wire indication when the color element value of the pixel corresponds to the wire feature. A fault detector circuit receives the wire indication from the panel feature detector corresponding to predetermined pixels associated with the hole site for determining faults on the circuit board.
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Citations
40 Claims
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1. An optical inspection system for detecting faults at potential hole sites of a wire scribed circuit board having a plurality of wires scribed on a substrate, comprising:
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a video camera for receiving images of desired hole sites on said wire scribed circuit board, said video camera converting each image to electrical video signals; an image storage memory for storing color element values indicative of the chromaticity of a plurality of pixels derived from said electrical video signals; a panel feature detector receiving said color element values of a pixel to be analyzed from said image storage memory, providing a wire indication when said color element values of said pixel correspond to a wire feature; a pixel retrieve controller providing command signals to said image storage memory to transmit to said panel feature detector color element values corresponding to predetermined pixels associated with a hole site to be analyzed; and an open detector circuit receiving said wire indication from said panel feature detector corresponding to said predetermined pixels associated with said hole site, said open detector determining whether an open circuit could occur when said hole site is drilled; wherein said pixel retrieve controller further comprises an open scan table associated with a hole site having a plurality of corresponding scan lines said open scan table for each said scan line storing boundary values for an open circuit region, where said boundary values are used to derive said command signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An optical inspection system for detecting faults at potential hole sites of a wire scribed circuit board having a plurality of wires scribed on a substrate, comprising:
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a video camera for receiving images of desired hole sites on said wire scribed circuit board, said video camera converting each image to electrical video signals; an image storage memory for storing color element values indicative of a chromaticity of a plurality of pixels derived from said electrical video signals; a panel feature detector receiving said color element values of a pixel to be analyzed from said image storage memory, providing a wire indication when said color element values of said pixel correspond to a wire feature; a pixel retrieve controller providing command signals to said image storage memory to transmit to said panel feature detector color element values corresponding to predetermined pixels associated with a hole site to be analyzed; and a short detector circuit receiving said wire indication from said panel feature detector corresponding to said predetermined pixels associated with said hole site, said short detector circuit determining whether a short circuit could occur when said hole site is drilled; wherein said pixel retrieve controller further comprises a short scan table associated with a hole site having a plurality of corresponding scan lines said short scan table for each said scan line storing boundary values for a short circuit region, where said boundary values are used to derive said command signals. - View Dependent Claims (13, 14)
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15. An optical inspection system for detecting faults at potential hole sites of a wire scribed circuit board having a plurality of wires scribed on a substrate, comprising:
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a video camera for receiving images of desired hole sites on said wire scribed circuit board, said video camera converting each image to electrical video signals; an image storage memory for storing color element values indicative of a chromaticity of a plurality of pixels derived from said electrical video signals; a panel feature detector receiving said color element values of a pixel to be analyzed from said image storage memory, providing a wire indication when said color element values of said pixel correspond to a wire feature; a pixel retrieve controller providing command signals to said image storage memory to transmit to said panel feature detector color element values corresponding to predetermined pixels associated with a hole site to be analyzed; and a short detector circuit receiving said wire indication from said panel feature detector corresponding to said predetermined pixels associated with said hole site, said short detector circuit determining whether a short circuit could occur when said hole site is drilled; wherein said predetermined pixels correspond to an annular short circuit region superimposed on said hole site and said short detector circuit further comprises; a bin histogram having a plurality of bins dividing said annular short circuit region into equal parts, each bin having a corresponding bin number, said bin histogram storing the number of detected wire pixels associated with each bin number; a digital filter for processing data stored in said bin histogram for identifying the peak occurrences of said detected wire pixels; and an analyzer for determining whether the ratio of the number of wire pixels detected in the highest two peak occurrences over the total number of pixels in said bin histogram is above a predetermined threshold.
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16. An optical inspection system for detecting faults at hole sites of a wire scribed circuit board having a plurality of wires scribed on a substrate, comprising:
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a video camera for receiving images of desired hole sites on said wire scribed circuit board, said video camera converting each image to electrical video signals; an image storage memory for storing color element values indicative of the chromaticity of a plurality of pixels derived from said electrical video signals; a panel feature detector receiving said color element values of a pixel to be analyzed from said image storage memory, providing a wire indication when said color element values of said pixel correspond to a wire feature; a pixel retrieve controller providing command signals to said image storage memory to transmit to said panel feature detector color element values corresponding to predetermined pixels associated with a hole site to be analyzed; a fault detector circuit receiving said wire indication from said panel feature detector corresponding to said predetermined pixels associated with said hole site, said fault detector determining whether a fault is present at said hole site; and a registration analyzer that aligns said wire scribed circuit board with respect to a desired location comprising; a row profile buffer receiving said wire pixel indication from said panel feature detector; a column profile buffer receiving said wire pixel indication from said panel feature detector; a cluster identifier for recognizing significant wire pixel peak occurrences in said row and column profile buffers; a cluster analyzer for determining the x-y coordinates of the center of said wire pixel peak occurrences corresponding to data in said row profile buffer and said column profile buffer; and a compensator for comparing the desired location of said center and actual location of said center determined by said cluster analyzer and computing a transformation matrix so that errors arising from an improper alignment of said wire scribed circuit board can be compensated.
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17. An optical inspection system for detecting faults at hole sites of a wire scribed circuit board having a plurality of wires scribed on a substrate, comprising:
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a video camera for receiving images of desired hole sites on said wire scribed circuit board, said video camera converting each image to electrical video signals; an image storage memory for storing color element values indicative of the chromaticity of a plurality of pixels derived from said electrical video signals; a panel feature detector receiving said color element values of a pixel to be analyzed from said image storage memory, providing a wire indication when said color element values of said pixel correspond to a wire feature; a pixel retrieve controller providing command signals to said image storage memory to transmit to said panel feature detector color element values corresponding to predetermined pixels associated with a hole site to be analyzed; a fault detector circuit receiving said wire indication from said panel feature detector corresponding to said predetermined pixels associated with said hole site, said fault detector determining whether a fault is present at said hole site; and wherein said panel feature detector further comprises; a wire look up table representing a three dimensional RGB space said wire look up table addressed by a number corresponding to the magnitude of color element values of a pixel provided by said image storage memory, where the data corresponding to said address is set to "1" when said color element values of said pixel correspond to a wire pixel, where the data has been stored during a previous training mode; a substrate look up table representing a three dimensional RGB space addressed by a number corresponding to the magnitude of color element values of a pixel provided by said image storage memory, where the data corresponding to said address is set to "1" when said color element values of said pixel correspond to a substrate pixel, where the data has been stored during a previous training mode; and an inhibitor for setting an addressed bit in said wire look up table back to zero whenever the same color element values of a pixel have set an addressed bit in both wire and substrate lookup tables to "1". - View Dependent Claims (18)
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19. An optical inspection system for differentiating wires from substrate in a wire scribed circuit board having a plurality of wires scribed on said substrate, comprising:
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a video camera for receiving desired images on said wire scribed circuit board, said video camera converting each image to electrical video signals; conversion means for converting said electrical video signals into a plurality of scan lines having a plurality of pixels; a memory means for storing information representing RGB color element values contained in each of said pixels of said image; means for sampling regions on said wire scribed circuit board during a training mode; a wire look up table for representing points in RGB space corresponding to wire features and a substrate look up table for representing points in RGB space corresponding to substrate features, where the contents of said wire look up table are determined from samples of wire regions obtained by said sampling means, and the contents of said substrate look up table are determined from samples of substrate regions obtained by said sampling means. - View Dependent Claims (20, 21, 22)
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23. A method for detecting faults at hole sites of a plurality of wire scribed circuit boards each having a plurality of wires scribed on a substrate, comprising the steps of:
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receiving desired images from each wire scribed circuit board; converting each one of said desired images to a plurality of pixels; deriving color element values indicative of chromaticity corresponding to each pixel of said desired images; displaying said desired images from said wire scribed circuit board; providing a training mode for a sample wire scribed circuit board by, sampling wire regions of said circuit board for retrieving color element values associated with wire; sampling substrate regions of said circuit board for retrieving color element values associated with substrate; tinting, to a first color, all pixels in said displayed image having color element values corresponding to said retrieved color element values associated with wire; and tinting, to a second color, all pixels in said displayed image having color element values corresponding to said retrieved color element values associated with substrate. - View Dependent Claims (24, 25)
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26. A method for detecting faults at hole sites of a plurality of wire scribed circuit boards each having a plurality of wires scribed on a substrate, comprising the steps of:
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receiving desired images from each wire scribed circuit board; converting each one of said desired images to a plurality of pixels; deriving hue values corresponding to each pixel of said desired images; displaying said desired images from said wire scribed circuit board; providing a training mode for a sample wire scribed circuit board by, setting two hue thresholds so that all pixels in said displayed image having hue values in a range between said two hue thresholds are associated with wire pixels and all other pixels are associated with substrate pixels.
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27. An optical inspection system for detecting faults at desired inspection sites of a printed circuit board having a plurality of conductor traces disposed on a substrate, comprising:
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a video camera for receiving images of said desired inspection sites on said printed circuit board, said video camera converting each image to electrical video signals; an image storage memory for storing information representing color element values indicative of the chromaticity of a plurality of pixels derived from said electrical video signals; a panel feature detector receiving said color element values of a pixel to be analyzed from said image storage memory, providing a conductor trace indication when said color element values of said pixel correspond to a conductor trace; a pixel retrieve controller providing command signals to said image storage memory to transmit to said panel feature detector color element values corresponding to predetermined pixels associated with said desired inspection site to be analyzed; a fault detector circuit receiving said conductor trace indication from said panel feature detector corresponding to said predetermined pixels associated with said desired inspection site, said fault detector determining whether a fault is present at said desired inspection site; and wherein said panel feature detector is provided with a training mode where conductor trace regions are sampled for establishing color element values associated with conductor trace and substrate regions are sampled for establishing color element values associated with substrate. - View Dependent Claims (28, 29, 30, 31, 32, 33, 35, 36)
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34. An optical inspection system for detecting faults at desired inspection sites of a printed circuit board having a plurality of conductor traces disposed on a substrate, comprising:
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a video camera for receiving images of said desired inspection sites on said printed circuit board, said video camera converting each image to electrical video signals; an image storage memory for storing information representing color element values indicative of the chromaticity of a plurality of pixels derived from said electrical video signals; a panel feature detector receiving said color element values of a pixel to be analyzed from said image storage memory, providing a conductor trace indication when said color element values of said pixel correspond to a conductor trace; a pixel retrieve controller providing command signals to said image storage memory to transmit to said panel feature detector color element values corresponding to predetermined pixels associated with said desired inspection site to be analyzed; a fault detector circuit receiving said conductor trace indication from said panel feature detector corresponding to said predetermined pixels associated with said desired inspection site, said fault detector determining whether a fault is present at said desired inspection site; and wherein said panel feature detector further comprises; an RGB to hue extractor receiving the RGB values corresponding to each pixel being analyzed and providing a hue component corresponding to said pixel being analyzed; and a threshold adjuster having a first and a second hue parameter defining a range of hue values such that said pixel being analyzed is attributed to a trace pixel when the value of said hue component corresponding to said pixel being analyzed is within said range of hue values.
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37. A method for detecting shorts at potential hole sites of a wire scribed circuit board having a plurality of wires scribed on a substrate, comprising the steps of:
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receiving desired images from said wire scribed circuit board; converting said desired images to a plurality of pixels; retrieving from said plurality of pixels those pixels located within boundaries of an annular short circuit reticle superimposed on a hole site; analyzing said retrieved pixels so as to provide wire indications indicating whether said pixels correspond to wires scribed on said substrate; dividing said annular short circuit reticle into equal parts each said equal part encompassing a plurality of said retrieved pixels and associated with a bin; assigning to each bin a bin value indicative of the number of said wire indications occurring within said bin'"'"'s associated equal part; and processing said bin values to identify clusters for determining whether a short circuit could occur when said hole site is drilled. - View Dependent Claims (38, 39, 40)
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Specification