Apparatus and method for measuring queue length of vehicles

• US 20030190058A1
• Filed: 03/24/2003
• Published: 10/09/2003
• Est. Priority Date: 04/04/2002
• Status: Abandoned Application

• Current Assignee: LG Industrial Systems Co., Ltd (LG Corporation)
• Original Assignee: LG Industrial Systems Co., Ltd (LG Corporation)
• Inventors: Choi, Sung Hoon, Jun, Joon Suk
• Application Number:
  US10/393,937
• Publication Number:
  US 20030190058A1
• Time in Patent Office: Days
• US Class Current: 382/104
• CPC Class Codes: G06T 7/60 Analysis of geometric attributes
• CPC Class Codes: G06T 7/74 involving reference images or patches
• CPC Class Codes: G06V 10/255 Detecting or recognising potential candidate objects based on visual cues, e.g. shapes
• CPC Class Codes: G08G 1/04 using optical or ultrasonic detectors

Abstract

In an apparatus and a method for measuring a queue length of vehicles, by installing a camera toward a direction same with a proceeding direction of vehicles on the road, photographing images of the road at the rear of vehicles and measuring a queue length of vehicles, it is possible to measure a queue length of vehicles accurately. The apparatus includes a camera for photographing the rear of vehicles on the road; an image converter for converting analog image signals corresponding to images photographed by the camera into digital image signals; and a control unit for extracting characteristics of vehicles from the converted digital images, calculating positions of vehicles on the road on the basis of the extracted characteristics and calculating a queue length of vehicles on the road on the basis of the calculated positions of vehicles.

Claims

1. An apparatus for measuring a queue length of vehicles, comprising:

a camera for acquiring the rear image of vehicles on the road;

an image converter for converting analog image signals corresponding to images acquired by the camera into digital image signals; and

a control unit for extracting characteristics of vehicles from the converted digital images, calculating positions of vehicles on the road on the basis of the extracted characteristics and calculating a queue length of vehicles on the road on the basis of the calculated positions of vehicles.

2. The apparatus of claim 1, wherein the control unit determines whether vehicles on the road are in a stopped state on the basis of the extracted characteristics and position trace thereof, calculates a distance from the stopped vehicles to a reference position of the road when the vehicles on the road are in the stopped state and outputs the calculated value as a queue length of the vehicles.

3. The apparatus of claim 1, wherein the control unit includes:

a preprocessing unit for removing noise of the converted digital images;

a characteristics extracting unit for extracting characteristics of vehicles from the noise-removed images by window units;

a characteristics tracing unit for setting a search region on the basis of positions of the extracted characteristics and recognizing characteristics not less than a predetermined threshold value in the set search region as vehicles; and

a queue length measuring unit for determining whether vehicles on the road are in a stopped state on the basis of positions of characteristics recognized as vehicles, calculating a distance from positions of characteristics of the stopped vehicles to a reference position of a traffic lane on the road and outputting the calculated distance value as a queue length value of the vehicles.

4. The apparatus of claim 3, wherein the characteristics include edge elements of a vertical line, a horizontal line and a diagonal line.

5. The apparatus of claim 3, wherein the preprocessing unit removes noise by filtering the converted digital images sequentially in the vertical and horizontal axes.

6. The apparatus of claim 3, wherein the characteristics extracting unit extracts a horizontal axis difference image (G_x), a vertical axis difference image (G_y) and calculates a characteristics value (WFV) corresponding to characteristics of a certain window unit by using the extracted difference images (G_x)(G_y).

7. The apparatus of claim 6, wherein the characteristics value (WFV) is calculated by following equation

8. The apparatus of claim 3, wherein the characteristics tracing unit sets positions of characteristics extracted from the characteristics extracting unit as a reference template;

predicts positions of the extracted characteristics on a next digital image;

determines the predicted position part as a search region, calculates a correlation coefficient between the search region determined by window units and the reference template;

performs template-matching of a window having a maximum correlation coefficient value among the calculated correlation coefficient values; and

selects the matched window as new characteristics.

9. The apparatus of claim 8, wherein the correlation coefficient (γ

) is calculated by following equation

10. The apparatus of claim 8, wherein the queue length measuring unit checks grouping of characteristics selected from the characteristics tracing unit according to position relations therebetween;

determines the characteristics as vehicles when the selected characteristics form groups;

determines the groups of the characteristics as stopped vehicles when the position trace of the characteristics determined as vehicles is smaller than a predetermined size for predetermined frames;

calculates a maximum and a minimum positions of the characteristics of the stopped vehicles in the horizontal and vertical axes;

calculates a distance from the center mark of the maximum and minimum positions to a reference position on a traffic lane of the road; and

outputs the calculated distance value as a queue length value of the vehicles.

11. The apparatus of claim 1, wherein the control unit includes;

a preprocessing unit for removing noise by performing Gauss-filtering about digital images converted in the image grabber in the horizontal and vertical axes directions and outputting noise-removed images;

a characteristics extracting unit for respectively extracting a difference image in the horizontal axis and the vertical axis from the images outputted from the preprocessing unit and extracting characteristics of vehicles from the extracted difference images by window units;

a characteristics tracing unit for setting characteristics positions extracted from the characteristics extracting unit as a reference template, predicting the characteristics positions on a next frame stored in the memory, determining the predicted positions part as a search region, calculating a correlation coefficient between the determined search region and the reference template by window units, template-matching a window having a maximum correlation coefficient value among the calculated correlation coefficient values and selecting the template-matched window as new characteristics; and

a queue length measuring unit for recognizing the characteristics as vehicles when the characteristics selected from the characteristics tracing unit form groups, determining the characteristics forming the groups as stopped vehicles when position trace of the characteristics recognized as the vehicles is smaller than a size predetermined for predetermined frames, calculating a maximum and a minimum positions of the characteristics of the stopped vehicles in the horizontal and vertical axes, calculating a distance from the center mark of the maximum and minimum positions to a reference line on a traffic lane of the road; and

outputting the calculated distance value as a queue length value of the vehicles.

12. A method for measuring a queue length of vehicles, comprising:

photographing the rear of vehicles on the road;

removing noise from the photographed images;

extracting characteristics of vehicles from the noise-removed images and tracing the extracted characteristics; and

determining the characteristics as stopped vehicles when moving trace of the characteristics is smaller than a predetermined size and calculating a distance from a position of the characteristics of the stopped vehicle to a reference position of a traffic lane on the road.

13. The method of claim 12, wherein the tracing step includes the sub-steps of:

calculating a difference image of the noise-removed image in the horizontal and vertical axes and extracting characteristics from the calculated difference images;

comparing whether the extracted characteristics value is greater than a predetermined threshold value;

lining characteristics values greater than the predetermined threshold value in order of size; and

selecting characteristics values not coincided with previously selected characteristics values from the lined characteristics values in order of great value as the predetermined number.

14. The method of claim 13, wherein a characteristics value (WFV) is calculated by following equation

15. The method of claim 12, wherein the characteristics tracing step includes the sub-steps of:

calculating a difference image of the noise-removed image in the horizontal and vertical axes and extracting characteristics of vehicles from the calculated difference image by predetermined window units; and

determining a search region on the basis of positions of the extracted characteristics and determining characteristics not less than a predetermined threshold value in the search region as vehicles.

16. The method of claim 12, wherein the characteristics tracing step includes the sub-steps of:

setting positions of characteristics extracted from the image as a reference template;

predicting positions of the extracted characteristics on a next image and determining positions of the predicted characteristics as a search region;

calculating a correlation coefficient between a window in the search region and the reference template; and

selecting a window showing a maximum correlation coefficient value among the calculated correlation coefficient values as new characteristics.

17. The method of claim 16, wherein the correlation coefficient (γ

) is calculated by following equation

18. The apparatus of claim 17, wherein the distance calculating step includes the sub-steps of:

recognizing vehicles on the basis of positions of the selected characteristics;

determining the recognized characteristics (vehicles) as stopped vehicles when position trace of the characteristics recognized as vehicles is smaller than a predetermined size for predetermined frames;

calculating a maximum and a minimum positions of the characteristics of the stopped vehicles in the horizontal and vertical axes; and

calculating a distance from the center mark of the maximum and minimum positions to a reference position in a traffic lane on the road as a queue length of the vehicles.