Environment monitoring system

• US 6,445,809 B1
• Filed: 08/26/1999
• Issued: 09/03/2002
• Est. Priority Date: 08/27/1998
• Status: Expired due to Fees

• Current Assignee: Yazaki Corporation
• Original Assignee: Yazaki Corporation
• Inventors: Imai, Teruhisa, Ishikawa, Naoto, Sasaki, Kazuyuki, Nakajima, Masato
• Primary Examiner(s): Patel, Jayanti K.
• Application Number:
  US09/383,200
• Time in Patent Office: 1,104 Days
• Field of Search: 382/100, 382/103, 382/104, 382/107, 382/181, 382/199, 382/206, 382/216, 382/294, 382/295, 340/435, 340/461, 340/903, 340/941, 348/116, 348/148, 356/3.14, 701/200
• US Class Current: 382/104
• CPC Class Codes: B60R 1/00 Optical viewing arrangements; Real-time viewing arrangements for drivers or passengers using optical image capturing systems, e.g. cameras or video systems specially adapted for use in or on vehicles
• CPC Class Codes: G01S 11/12 using electromagnetic waves other than radio waves
• CPC Class Codes: G06T 7/269 using gradient-based methods
• CPC Class Codes: G06V 20/58 Recognition of moving objects or obstacles, e.g. vehicles or pedestrians; Recognition of traffic objects, e.g. traffic signs, traffic lights or roads
• CPC Class Codes: G06V 20/588 Recognition of the road, e.g. of lane markings; Recognition of the vehicle driving pattern in relation to the road

Abstract

In an environment monitoring system using an optical flow, an optical-flow detecting device detects the optical flow in the steps of reverse-projection converting the early image of two early and later images picked up by an image picked up, on the basis of a predetermined optical arrangement of the image pick-up means onto an x-z plane in parallel to a road surface in a real space to acquire a road surface image; computing a moving distance of one'"'"'s own vehicle in two timings on the basis of a time interval between two timings and speed information of one'"'"'s own vehicle; parallel-shifting the road surface image by the moving distance thus computed; projection-converting the road surface image after parallel-shifted to acquire an estimated image of the later image in timing; acquiring a differential image between the later image and its estimated image to extract a feature point; and searching a corresponding point of the feature point extracted. In this configuration, it is possible to prevent an object such as a paint which should not be detected on a road surface from being erroneously detected as another surrounding vehicle.

Claims

1. An environment monitoring system for monitoring a relative relation between one'"'"'s own vehicle and another surrounding vehicle comprising:

image pick-up means for picking up two early and later images which are located at a front, rear or diagonal-rear position from one'"'"'s own vehicle at two early and later timings and on the basis of the images thus picked-up, detecting white lines of one'"'"'s own vehicle lane on which one'"'"'s own vehicle runs;

monitoring region setting means for setting a monitoring region in one'"'"'s own vehicle lane or an adjacent lane on the basis of the white lines thus detected; and

optical-flow detecting means for detecting an optical flow generated from another surrounding vehicle within the monitoring region, wherein said optical-flow detecting means comprises;

means for reverse-projection converting said early image on the basis of a predetermined optical arrangement of said image pick-up means onto an x-z plane in parallel to a road surface in a real space to acquire a road surface image;

means for computing a moving distance of one'"'"'s own vehicle between the two timings on the basis of a time interval between said two timings and speed information of one'"'"'s own vehicle;

means for parallel-shifting the road surface image by the moving distance thus computed;

means for projection-converting the road surface image after parallel-shifted to acquire an estimated image of the later image in timing;

means for acquiring a differential image between the later image and its estimated image to extract a feature point; and

means for searching a corresponding point of the feature point extracted, thereby-detecting the optical flow.

2. An environment monitoring system according to claim 1, wherein said optical-flow detecting means further comprises:

means for, prior to projection-converting the road surface image, computing angles of the white lines in the vicinity of one'"'"'s own vehicle formed together with a z-axis on said road surface image parallel-shifted to acquire an average angle thereof; and

means for rotating said road surface by said average angle around an origin of said x-z coordinate.

3. An environment monitoring system according to claim 2, further comprising means for evaluating the degree of danger which decides dangerous when the average value 1 of the magnitudes of optical flows exceeds a prescribed value as regards the degree D of danger in a front, rear or diagonal-rear field of view expressed by $D=l=\left(1/N\right)\times$

∑

i=1N

 



li

(where li denotes the magnitude of the optical flow, and N denotes the number of generated optical flows).

4. An environment monitoring system according to claim 3, wherein said means for evaluating the degree of danger decides dangerous when the number N of said optical flows exceeds a prescribed value.

5. An environment monitoring system according to claim 1, further comprising means for evaluating the degree of danger which decides dangerous when the average value 1 of the magnitudes of optical flows exceeds a prescribed value as regards the degree D of danger in a front, rear or diagonal-rear field of view expressed by $D=l=\left(1/N\right)\times$

∑

i=1N

 



li

(where li denotes the magnitude of the optical flow, and N denotes the number of generated optical flows).

6. An environment monitoring system according to claim 3, wherein said means for evaluating the degree of danger decides dangerous when the number N of said optical flows exceeds a prescribed value.

7. A method for monitoring a relative relation between an own vehicle and another environmental vehicle comprising the steps of:

picking up two early and later images which are located at a front, rear and diagonal-rear position from an own vehicle at two early and later timings by an image pick-up means and on the basis of the images thus picked-up, detecting white lines of an own vehicle lane on which one'"'"'s own vehicle runs;

setting a monitoring region in one'"'"'s own vehicle lane or an adjacent lane on the basis of the white lines thus detected;

detecting an optical flow generated from another environmental vehicle within the monitoring region, wherein said step of detecting an optical flow comprises the steps of;

reverse-projection converting said early image on the basis of a predetermined optical arrangement of said image pick-up means onto an x-z plane in parallel to a road surface in a real space to acquire a road surface image;

computing a moving distance of one'"'"'s own vehicle in the two timings on the basis of a time interval between said two timings and speed information of one'"'"'s own vehicle;

parallel-shifting the road surface image by the moving distance thus computed;

projection-converting the road surface image after parallel-shifted to acquire an estimated image of the later image in timing;

acquiring a differential image between the later image and its estimated image to extract a feature point; and

searching a corresponding point of the feature point extracted, thereby detecting the optical flow.

8. A method according to claim 7, wherein said step of detecting an optical-flow further comprises:

prior to projection-converting the road surface image, computing angles of the white lines in the vicinity of one'"'"'s own vehicle formed together with a z-axis on said road surface image parallel-shifted to acquire an average angle thereof; and

rotating said road surface by said average angle around an origin of said x-z coordinate.