Car sensing method and car sensing apparatus

• US 6,625,300 B1
• Filed: 10/06/1999
• Issued: 09/23/2003
• Est. Priority Date: 10/09/1998
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Kyo, Sholin
• Primary Examiner(s): Patel, Jayanti K.
• Assistant Examiner(s): Tabatabai, Abolfazl
• Application Number:
  US09/413,438
• Time in Patent Office: 1,448 Days
• Field of Search: 382/104, 382/106, 382/190, 382/199, 382/291, 701/200, 701/201, 701/207, 701/209, 701/1, 701/3, 701/19, 701/20, 701/21, 701/45, 701/91, 701/93, 701/96, 701/117, 340/438, 340/525, 340/440, 180/907, 180/172, 180/197, 180/282, 180/283, 180/290, 246/83, 246/90, 246/126, 246/166
• US Class Current: 382/104
• CPC Class Codes: G06V 10/44 Local feature extraction by analysis of parts of the pattern, e.g. by detecting edges, contours, loops, corners, strokes or intersections; Connectivity analysis, e.g. of connected components
• CPC Class Codes: G07C 5/0891 Video recorder in combination with video camera
• CPC Class Codes: G08G 1/04 using optical or ultrasonic detectors

Abstract

Disclosed are a car sensing method and a car sensing apparatus, which are cable of sensing a car surely in spite of an image with poor contrast.

Image inputting means photographs a rear portion of another car running ahead of a car mounting a car sensing apparatus, for example, and generates image data. Edge line segment extraction means extracts horizontal and vertical edge line segments included in an image based on the image data. Line segment pair extracting means extracts a pair of vertical edge line segments among the extracted vertical edge line segments, a horizontal distance and a vertical distance between the vertical edge line segments forming the pair satisfying a reference condition relating to a car width and a car height. Line segment pair evaluation value calculating means selects horizontal edge line segments existing, in the horizontal direction, between the vertical edge line segments among the horizontal edge line segments for each pair of vertical edge line segments. Based on the number, positions and lengths of the selected horizontal line segments, the line segment pair evaluation value calculating means calculates an evaluation value relating to a possibility that the vertical edge line segments forming the pair are line segments expressing both side end portions. Decision means compares the evaluation value with a reference value, and decides whether or not the vertical edge line segments forming the pair are line segments expressing the both side end portion of the car.

Claims

1. A method for sensing a car, comprising

capturing an image of an object and generating image data of the object;

extracting horizontal edge line segments and vertical edge line segments based on said image data generated in said image inputting step;

extracting a pair of vertical edge line segments among said vertical edge line segments extracted in said edge line segment extracting step, said pair of vertical edge line segments having horizontal and vertical distances between the vertical edge line segments forming the pair which satisfy reference conditions relating to a car height and a car width;

selecting horizontal edge line segments existing between said pair of vertical edge line segments in a horizontal direction among said horizontal edge line segments extracted in said edge line segment extracting step for each vertical edge line segment extracted in said line segment pair extracting step, and based on the number of selected horizontal edge line segments, positions of the selected horizontal edge line segments and lengths of the selected edge line segments, calculating an evaluation value relating to a possibility that said pair of vertical edge line segments may be line segments expressing both side end portions of the car; and

comparing a reference value with the evaluation value calculated, in said line segment pair evaluation value calculating step and deciding whether or not said pair of vertical edge line segments are line segments expressing the both side end portions of the car.

2. The car sensing method according to claim 1, wherein said edge line segment extracting step extracts said edge horizontal edge segments and said vertical edge segments by performing an edge filter processing, a binarization processing and a labeling processing for said image data generated in said image inputting step.

3. The car sensing method according to claim 1, wherein said line segment pair extracting step further includes:

calculating, for each pair of vertical edge line segments, a position of a center of gravity in a vertical direction of said pair of vertical edge line segments, a horizontal distance between said pair of vertical edge line segments, and a vertical distance between said pair of vertical edge line segments;

obtaining the maximum and minimum values of a width of a car which the car can actually assume and the maximum value of a height thereof, based on an image angle at the time when in said image inputting step the object is photographed, as well as on said position of the center of gravity calculated in said position information acquiring step, and

wherein said vertical edge line segment pair is extracted under reference conditions, said conditions including that the horizontal distance between said vertical edge line segments calculated in said position information acquiring step is smaller than the maximum value of said car width obtained in said limit dimension acquiring step, the horizontal distance between said vertical edge line segments calculated in said position information acquiring step is larger than the minimum value of the car width obtained in said limit dimension acquiring step, and the vertical distance between said vertical edge line segments calculated in said position information acquiring step is smaller than the maximum value of the car height obtained in said limit dimension acquiring step.

4. The car sensing method according to claim 1, wherein the line segment pair evaluation value calculating step includes calculating attribution degrees of said selected horizontal edge line segments to said vertical edge line segment pair, and, in the attribution degree calculating step, wherein as the position of the center of gravity of said horizontal edge line segments gets closer to the position of the center of gravity of said vertical edge line segment pair, and the length of said horizontal edge line segment gets larger, a higher attribution degree is given to said horizontal edge line segment, and wherein in the line segment pair evaluation value calculating step, the attribution degrees calculated in said attribution degree calculating step are added up for all of said horizontal edge line segments selected, and the value obtained by the addition is used as said evaluation value.

5. The car sensing method according to claim 1, wherein in said image inputting step, said car is photographed from the rear of said car.

6. A car sensing apparatus comprising:

image inputting means for capturing an image of an object and generating image data of the object;

edge line segment extracting means for extracting horizontal edge line segments and vertical edge line segments which are included in an image by said image data, based on said image data generated by said image inputting means;

line segment pair extracting means for extracting a pair of vertical edge line segments among said vertical edge line segments extracted by said edge line segment extractor, a horizontal distance and a vertical distance between the vertical edge line segments forming the pair satisfying reference conditions relating to a car height and a car width;

line segment pair evaluation value calculating means for selecting horizontal edge line segments existing between said vertical edge line segment pair in a horizontal direction, among said horizontal edge line segments extracted by said edge line segment extracting means, for each pair of vertical edge line segments extracted by said line segment pair extracting means, and, based on the number of the selected horizontal edge line segments, positions of the horizontal edge line segments and lengths of the horizontal edge line segments, calculating an evaluation value relating to a possibility that said pair of vertical edge line segments may be line segments expressing both side end portions of the car; and

decision means for comparing a reference value with said evaluation value calculated by said line segment pair evaluation value calculating means and deciding whether or not the vertical edge line segments forming the pair are line segments expressing the both side end portions of said car.

7. The car sensing apparatus according to claim 6, wherein said edge line segment extracting means performs an edge filter processing, a binarization processing and a labeling processing for said image data generated by said image inputting means, thus extracting said horizontal and vertical edge line segments.

8. The car sensing apparatus according to claim 6,

wherein said line segment pair extracting means includes:

position information acquiring means for calculating a position of the center of gravity, in the vertical direction, of the two vertical edge line segments forming said pair, a horizontal distance between the vertical edge line segments and a vertical distance between the vertical edge line segments, for each pair of vertical edge line segments; and

limit dimension acquiring means for obtaining the maximum and minimum values of a width of a car which the car can actually assume, and the maximum value of a height thereof, based on an image angle at the time when said image inputting means photographs the object as well as on the position of the center of gravity calculated by said position information acquiring means, and

wherein said line segment pair extracting means extracts said vertical edge line segment pair under said reference conditions that the horizontal distance between said vertical edge line segments calculated by said position information acquiring means is smaller than the maximum value of said car width obtained by said limit dimension acquiring means, the horizontal distance between said vertical edge line segments calculated by said position information acquiring means is larger than the minimum value of said car width obtained by said limit dimension acquiring means, and the vertical distance between said vertical edge line segments calculated by said position information acquiring means is smaller than the maximum value of said car height obtained by said limit dimension acquiring means.

9. The car sensing apparatus according to claim 6,

wherein said line segment pair evaluation value calculating means includes attribution degree calculating means for calculating attribution degrees of said selected horizontal edge line segments to said vertical edge line segment pair,

said attribution degree calculating means gives a higher attribution degree to the horizontal edge line segment as the position of the center of gravity of said horizontal edge line segments is closer to the position of the center of gravity of said vertical edge line segment pair and the length of said horizontal edge line segment is larger, and

said line segment pair evaluation value calculating means adds up the attribution degrees calculated by said attribution degree calculating means for all of said horizontal edge line segments selected, and the value obtained by the addition is used as said evaluation value.

10. The car sensing apparatus according to claim 6, wherein said image inputting means photographs said car from the rear thereof.

11. A car sensing apparatus comprising:

an image inputting device that captures an image of an object and generates image data of the object;

an edge line segment extractor that extracts horizontal edge line segments and vertical edge line segments which are included in an image by said image data, based on said image data generated by said image inputting device;

a line segment pair extractor that extracts a pair of vertical edge line segments among said vertical edge line segments extracted by said edge line segment extractor, a horizontal distance and a vertical distance between the vertical edge line segments forming the pair satisfying reference conditions relating to a car height and a car width;

a line segment pair evaluation value calculator that calculates horizontal edge line segments existing between said vertical edge line segment pair in a horizontal direction, among said horizontal edge line segments extracted by said edge line segment extractor, for each pair of vertical edge line segments extracted by said line segment pair extractor, and, based on the number of the selected horizontal edge line segments, positions of the horizontal edge line segments and lengths of the horizontal edge line segments, calculating an evaluation value relating to a possibility that said pair of vertical edge line segments may be line segments expressing both side end portions of the car; and

decision means for comparing a reference value with said evaluation value calculated by said line segment pair evaluation value calculator and deciding whether or not the vertical edge line segments forming the pair are line segments expressing the both side end portions of said car.

12. The car sensing apparatus according to claim 11, wherein said edge line segment extractor performs an edge filter processing, a binarization processing and a labeling processing for said image data generated by said image inputting device, thus extracting said horizontal and vertical edge line segments.

13. The car sensing apparatus according to claim 11,

wherein said line segment pair extractor includes:

a position information calculator that calculates a position of the center of gravity, in the vertical direction, of the two vertical edge line segments forming said pair, a horizontal distance between the vertical edge line segments and a vertical distance between the vertical edge line segments, for each pair of vertical edge line segments; and

a limit dimension calculator that obtains the maximum and minimum values of a width of a car which the car can actually assume, and the maximum value of a height thereof based on an image angle at the time when said image inputting means photographs the object as well as on the position of the center of gravity calculated by said position information calculator, and

wherein said line segment pair extractor extracts said vertical edge line segment pair under said reference conditions, said reference conditions including that the horizontal distance between said vertical edge line segments calculated by said position information calculator is smaller than the maximum value of said car width obtained by said limit dimension calculator, the horizontal distance between said vertical edge line segments calculated by said position information calculator is larger than the minimum value of said car width obtained by said limit dimension calculator, and the vertical distance between said vertical edge line segments calculated by said position information calculator is smaller than the maximum value of said car height obtained by said limit dimension calculator.

14. (The car sensing apparatus according to claim 11,

wherein said line segment pair evaluation value calculator includes an attribution degree calculator that calculates attribution degrees of said selected horizontal edge line segments to said vertical edge line segment pair, said attribution degree calculator giving a higher attribution degree to the horizontal edge line segment as the position of the center of gravity of said horizontal edge line segments gets closer to the position of the center of gravity of said vertical edge line segment pair and the length of said horizontal edge line segment gets larger, and

said line segment pair evaluation value calculator adding up the attribution degrees calculated by said attribution degree calculator for all of said horizontal edge line segments selected, and the value obtained by the addition is used as said evaluation value.

15. The car sensing apparatus according to claim 11, wherein said image device photographs said car from the rear thereof.