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Real-time apparatus for detecting surface defects on objects

  • US 5,274,713 A
  • Filed: 09/23/1991
  • Issued: 12/28/1993
  • Est. Priority Date: 09/23/1991
  • Status: Expired due to Term
First Claim
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1. A real-time apparatus for detecting surface defects on an object under test (OUT) comprising:

  • a high-frequency (at least 25 KHz) linear light source for generating a linear light to be focused on the surface of a moving OUT;

    a linear charge coupled device (CCD) camera for scanning the moving OUT line-by-line and generating a corresponding image signal;

    a driving circuit for controlling said linear CCD camera to couple said image signal generated thereby to an image-signal processing circuit;

    said image-signal processing circuit coupling with said image signal from said linear CCD camera, compensating said image signal to a compensated signal, digitalizing said compensated signal to a train of digital signals, and determining which said digitalized signals are a HIGH or a LOW signal according to a predetermined gray-scale value;

    a combination of said HIGH and LOW signals constituting binary image data in the form of a train of binary pulses;

    an image-storing circuit connected to said image-signal processing circuit for storing said binary image data;

    a defect-detecting unit connected to said image-storing circuit for detecting whether an area unit is a valid defect, a small defect, or defectless, wherein said valid defect is defined by meeting at least one of a plurality of predetermined defect patterns, said small defect represents defects not meeting said predetermined defect patterns, and said defectless represents no defect at all; and

    a defect-detecting statistic unit being connected to said image-data storing means for calculating a total amount of defects, and an area and location of each defect by a well-known connectivity analyzation process.

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