Traffic congestion measuring method and apparatus and image processing method and apparatus

  • US 5,999,635 A
  • Filed: 07/10/1998
  • Issued: 12/07/1999
  • Est. Priority Date: 01/12/1996
  • Status: Expired due to Term
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First Claim
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1. A traffic congestion measuring method of measuring a state of traffic congestion on the basis of a motion picture which represents a road and vehicles coming and going on said road and is formed by a series of images taken by a video camera, comprising the steps of:

  • (a) setting a plurality of sample lines in said motion picture, each of said sample lines being formed by a plurality of sample points aligned on a line perpendicular to a direction in which said road extends, and each of said sample points having a brightness level;

    (b) forming a criterion brightness image, in which no vehicle is expected to be present, taken by said video camera;

    (c) calculating a difference image indicative of a difference in brightness between one of said series of images taken at a predetermined time and said criterion brightness image by calculating brightness difference values each indicative of a difference in brightness between each of the sample points in the image taken at said predetermined time and each of the sample points in said criterion brightness image corresponding in position to each other;

    (d) detecting, as difference sample lines, the sample lines which are situated in the image taken at said predetermined time and each of which has a brightness level having a difference larger than a predetermined level from each of the sample lines in said criterion brightness image, on the basis of the brightness difference values of the sample points in said difference image;

    (e) spatially differentiating said difference image to calculate differentiation values respectively belonging to the sample points in said difference image;

    (f) detecting, as edge sample lines, the sample lines which are situated in the image taken at said predetermined time and each of which has a brightness level having a difference larger than a predetermined level from one of two sample lines in the direct neighborhood of each of the sample lines, on the basis of the differentiation values of the sample points in said spatially differentiated difference image;

    (g) detecting, as presence sample lines on each of which the vehicle is expected to be present, the difference sample lines detected in said step (d) and the edge sample lines detected in said step (f); and

    (h) measuring the state of traffic congestion on the basis of said presence sample lines.

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