Web inspection system

• US 6,750,466 B2
• Filed: 02/09/2001
• Issued: 06/15/2004
• Est. Priority Date: 02/09/2001
• Status: Active Grant

• Current Assignee: Wintriss Engineering Corporation
• Original Assignee: Wintriss Engineering Corporation
• Inventors: Becker, Robin D., Guha, Sujoy D., Kiraly, Chris M.
• Primary Examiner(s): Bruce, David V.
• Assistant Examiner(s): SONG, HOON K
• Application Number:
  US09/780,313
• Publication Number:
  US 20020109112A1
• Time in Patent Office: 1,222 Days
• Field of Search: 250/559.46, 250/559.4, 250/559.41, 250/559.42, 250/549.43, 250/559.44, 250/559.45, 356/430, 356/429, 356/237.1, 356/238.1, 356/238.2
• US Class Current: 250/559.46
• CPC Class Codes: G01N 2021/891 Edge discrimination, e.g. by signal filtering
• CPC Class Codes: G01N 21/89 in moving material, e.g. running paper or textiles G01N21/90, G01N21/91, G01N21/94 take precedence
• CPC Class Codes: G01N 21/8903 using a multiple detector array
• CPC Class Codes: G01N 21/8921 Streaks
• CPC Class Codes: G06T 2207/30124 Fabrics; Textile; Paper
• CPC Class Codes: G06T 7/0004 Industrial image inspection

Abstract

A web inspection system provides detection of web flaws along the machine direction and cross direction of a web. The detectable percent contrast between good web material and bad web material in one embodiment approaches noise level. The web inspection system utilizes a multiple of smart cameras connected to a host computer via an ethernet hub. Each smart camera includes a line scan camera for producing digital pixels, a means for lighting and pixel correction on a pixel by pixel basis, a web edge detector for monitoring the edges of a web, a multi-pipeline flaw detection pre-processor for detecting very small changes in the web material, a run length encoder for generating data regarding the location of each group of potential flaws in a cross direction, a 2D blob detector and analyzer for generating data regarding the location of block flaws along a machine direction, and an inspect/reject analysis for determining the actual flaw data from the potential flaw data. A low contrast web inspection system provides a balanced and distributed architecture that handles high defect rates, and that is easily integrated with an existing web manufacturing system.

Claims

1. A web inspection system for detecting a plurality of web flaws of a web, the web inspection system comprising:

a plurality of smart cameras for generating a digital pixel representation of a portion of the web, each smart camera for detecting the plurality of web flaws from the digital pixel representation and for generating output data comprising a digitized image of each flaw of the plurality of web flaws and for generating flaw location data for each flaw of the plurality of web flaws;

a host computer for controlling the web inspection system and for receiving and displaying the flaw image data and the flaw location data; and

an ethernet for connecting the plurality of smart cameras to the host computer, wherein the flaw image data and the flaw location data is transmitted over the ethernet from the plurality of smart cameras to the host computer, each smart camera of the plurality of smart cameras comprises;

a line scan camera for generating the digital pixel representation of a portion of the web;

a lighting uniformity and pixel sensitivity correction means for correcting each pixel of the digital pixel representation and for providing a corrected pixel representation;

a web edge detector for detecting at least one edge of the web;

a multi-pipeline pre-processor for filtering the corrected pixel representation, the multi-pipeline preprocessor generating a prioritized data stream of potential flaws;

a run length encoder for generating location data regarding a location of each group of the potential flaws in a cross direction;

a blob detector for generating block data regarding the location of blocks of the potential flaws along a machine direction; and

an inspect/reject analyzer for determining actual flaw data from the prioritized data stream of potential flaws.

2. The web inspection system of claim 1, wherein the multi-pipeline processor comprises:

a plurality of filters for averaging the corrected pixel representation over a distance of the web along a machine direction of the web;

a plurality of adaptive background subtraction channels connected to the plurality of filters, each adaptive background subtraction channel of the plurality of adaptive background subtraction channels producing a stream of subtracted pixel representations;

a plurality of thresholders, each thresholder of the plurality of thresholders connected to an output of an adaptive background subtraction channel of the plurality of adaptive background subtraction channels, each thresholder for grouping at least a portion of the stream of subtracted pixel representations and for producing a thresholder group output; and

a priority logic circuit for prioritizing the thresholder group output of each of the plurality of thresholders.

3. The web inspection system of claim 2, wherein the plurality of filters comprises:

a background filter;

a machine direction streak filter;

a cross direction streak filter; and

a small flaw filter.

4. The web inspection system of claim 2, wherein the plurality of thresholders comprises:

a single pixel flaw detector;

a uniformity detector;

a machine direction streak detector;

a cross direction streak detector; and

a small flaw detector.

5. The web inspection system of claim 1, wherein each smart camera of the plurality of smart cameras detects the plurality of web flaws from the digital pixel representation at a contrast approaching a signal noise level.

6. A method of low contrast web inspection of a web, the method comprising the steps of:

providing at least one smart camera for detecting at least one flaw on the web, wherein detecting the at least one flaw on the web comprises the steps of;

generating flaw image data of the at least one flaw, the flaw image data comprising an area of pixels having a length and a width;

generating flaw location data for locating the at least one flaw on the web; and

transmitting the flaw image data and flaw location data over an ethernet to a host computer; and

displaying the flaw image data and flaw location data on the host computer; and

wherein the step of generating the flaw image data and flaw location data comprises the steps of;

generating a pixel representation of the at least a portion of the web;

correcting the pixel representation for a lighting uniformity and a pixel sensitivity;

filtering the corrected pixel representation utilizing a plurality of filters;

grouping the filtered corrected pixel representations to generate a plurality of potential flaw data streams;

generating a prioritized data stream from the plurality of potential flaw data streams;

generating cross direction location data regarding a location of the prioritized data stream;

generating block data regarding the location of blocks of the prioritized data stream along a machine direction; and

generating the flaw image data from the prioritized data stream of potential flaws utilizing the cross direction location data and the block data.

7. A web inspection system for detecting a flaw of a plurality of possible flaws on a web, the web inspection system comprising:

at least one smart camera for generating a digitized video data stream of a flaw on a portion of the web, the at least one smart camera comprising;

a background filter for averaging the digitized video data stream over a first area of the web to generate an averaged background signal;

a machine direction streak filter for averaging the digitized video data stream over a distance of the web along a machine direction of the web to generate a filtered machine direction signal;

a cross direction streak filter for averaging the digitized video data stream over a distance of the web along a cross direction of the web to generate a filtered cross direction signal;

a first adaptive background subtraction channel for subtracting the averaged background signal from the filtered machine direction signal to generate a first pixel representation;

a second adaptive background subtraction channel for subtracting the averaged background signal from the filtered cross direction signal to generate a second pixel representation;

at least one multi-group thresholder for grouping the first and second pixel representations to generate at least two data streams of potential flaws; and

a priority logic circuit for prioritizing the at least two data streams of potential flaws to generate the digitized video data stream of the flaw.

8. The web inspection system of claim 7, wherein the at least one multi-group thresholder comprises:

a machine direction streak detector for detecting a narrow streak in the machine direction; and

a cross direction streak detector for detecting a narrow streak in the cross direction.

9. The web inspection system of claim 7, further comprising:

a small flaw filter for averaging the digitized video data stream over a second area of the web to generate an averaged small flaw signal; and

a third adaptive background subtraction channel for subtracting the averaged background signal from the average small flaw signal to generate a third pixel representation; and

a small flaw detector for detecting a small block flaw from the third pixel representation.

10. The web inspection system of claim 7, further comprising a single pixel adaptive background subtraction channel for subtracting the averaged background signal from the digitized video data stream, an output of the single pixel adaptive background subtraction channel coupled to a single pixel flaw detector having an output of single pixel flaws.

11. The web inspection system of claim 7, further comprising a uniformity detector having an input of the averaged background signal, the uniformity detector for outputting a block flaw signal.