Data processing: vehicles – navigation – and relative location – Relative location – Collision avoidance
Reexamination Certificate
1999-06-08
2001-06-12
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Relative location
Collision avoidance
C701S028000, C701S117000
Reexamination Certificate
active
06246961
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a collision alarm method and apparatus for vehicles, and more particularly, to a collision alarm method and apparatus for vehicles in which diagonally rearward photographs or forward photographs of a vehicle, such as an automobile, are taken with a photographing device such as a small, on-board CCD camera, and based on the images photographed the possibility of collision with another vehicle approaching from the diagonally rearward direction or traveling ahead is detected and alarmed to the driver by means of an alarm sound or the like.
2. Description of the Related Art
If, for example, during traveling on a superhighway the driver of a vehicle changes lanes without noticing another vehicle approaching in the adjoining lane to which he switches at a higher speed from the diagonally backward direction, a severe accident may be caused.
Further, if the driver of a vehicle suddenly brakes without noticing another vehicle approaching him from the backward direction in the same lane at a higher speed, it is likely that the another vehicle bumps into the rear of the driver's vehicle. It is thus necessary for the driver to notice vehicles around him. Likewise, if the driver of a vehicle swiftly approaches another vehicle traveling ahead of him and the another vehicle suddenly brakes, the driver may bump into the rear of the another vehicle. It is thus also necessary for the driver to recognize vehicles running ahead.
To cope with this problem, a method is proposed in Japanese Patent Applications Unexamined Publications Nos. 6-107096 and 7-50769 according to which optical flow is used to detect the approach to another vehicle running ahead and the approach of another vehicle from the diagonally backward direction and give an alarm in case of danger of collision.
In these conventional techniques, optical flow is obtained by processing two images obtained by photographing at different times the front view or the diagonal rear view of a vehicle with an on-board video camera, and by making use of a property of the optical flow, the degree of possibility of collision with another, approaching vehicle is judged. In other words, the property is used that the length of optical flow derived from the approaching vehicle becomes greater as the vehicle approaches at higher speed and the approaching vehicle comes closer to the vehicle with the on-board video camera. The approaching speed of and the distance to the approaching vehicle cannot be independently calculated from the optical flow.
In the above-mentioned conventional techniques, to obtain optical flow, as shown in
FIG. 9
, points A and B of variant brightness on the approaching vehicle in the two photographed images (A in the previously taken image and B in the later taken image) are selected as points to notice, and correlation windows WA and WB are set around the respective points A and B to process the pixels inside the correlation windows and extract the optical flow.
With the conventional techniques, however, there is a drawback in that the correlation window around the noticeable point cannot be made large in size if its processing time is taken into consideration, and if made with a size of 7 pixels×7 pixels, accuracy in detecting corresponding points in the two images photographed at different times will be lowered. Besides, if a large number of points of variant brightness exist on the approaching vehicle, the points to notice correspondingly increase, resulting in a longer time required for the processing.
Incidentally, it takes time before the driver, on being alarmed of a possible collision, takes action to correct his driving and avoid the collision. It is thus desirable that such an alarm be generated prior to the time required for completion of the action to avoid the possible collision.
SUMMARY OF THE INVENTION
This invention overcomes the above drawbacks and an object of this invention is to provide a collision alarm method and apparatus for vehicles which detect the danger of collision at high speed and give a timely alarm so as to enable action to be securely taken to avoid collision.
In order to attain the object, according to an aspect of this invention, there is provided a method of alarming of collision for vehicles, which comprises the steps of: photographing from a first vehicle to obtain two images of an environment at different times, the environment including a second vehicle; detecting in a previously-obtained one of the two images a first horizontal or vertical noticeable edge derived from the second vehicle; detecting in a subsequently-obtained one of the two images a second noticeable edge derived from the second vehicle, which corresponds to the first noticeable edge, with a correlation window set around the first and second noticeable edge; detecting an optical flow from the first and second noticeable edge; calculating a time of possible collision with the second vehicle based on the optical flow detected; and judging and alarming of danger of the possible collision with the second vehicle on the calculated time of the possible danger.
In the above collision alarm method, because the horizontal or vertical noticeable edge, which is extracted from two images taken at different times, is used to detect optical flow, the correlation window can be made large in size, and a reduction is made in the number of optical flows to be detected.
Advantageously, the two images are obtained by photographing a diagonal backward view of the first vehicle.
Owing to the above, danger of collision with the second vehicle approaching from the diagonal backward direction can be alarmed of based on the calculated time of possible collision.
Advantageously, the two images are obtained by photographing a forward view of the first vehicle.
Advantageously, the two images have a plurality of the corresponding noticeable edges derived from two or more of the second vehicles, and the step of calculating a time of possible collision comprises calculating the time of possible collision based on the optical flow detected from each of the corresponding noticeable edges derived from the second vehicles, and getting together the corresponding noticeable edges in groups according to the times of possible collisions, each of the groups of the corresponding noticeable edges being derived from one or another of the second vehicles, and the step of judging and alarming of danger comprises judging and alarming of the danger of the possible collision with the one or another of the second vehicles.
Owing to the above, a plurality of approaching vehicles can be separately detected, assuming that the noticeable edges having the same collision time are derived from the same vehicle, and an alarm of danger of collision can be made for each vehicle.
Advantageously, in the above the two images are obtained by photographing a diagonal backward view of the first vehicle.
Advantageously, the time interval for obtaining the two images is varied in compliance with a size of the first and second noticeable edge on the two images.
Advantageously, the two images have a plurality of the corresponding noticeable edges derived from two or more of the second vehicles, and the step of calculating a time of possible collision comprises getting together the corresponding noticeable edges in groups according to positions and components of a direction of y-coordinate of optical flows detected on the two images from the corresponding noticeable edges, each of the groups of the corresponding noticeable edges being derived from one or another of the second vehicles, and calculating the time of possible collision based on the optical flow or flows detected for each of the groups of the corresponding noticeable edges, and the step of judging and alarming of danger comprises judging and alarming of the danger of the possible collision with the one or another of the second vehicles.
According to another aspect of this invention, there is provided an apparatus for alarming of collision f
Ishikawa Naoto
Miyaoka Hirosada
Nakajima Masato
Sasaki Kazuyuki
Armstrong, Westerman Hattori, McLeland & Naughton
Cuchlinski Jr. William A.
Donnelly Arthur D.
Yazaki -Corporation
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