Object detector

• US 6,487,303 B1
• Filed: 06/15/1999
• Issued: 11/26/2002
• Est. Priority Date: 11/06/1996
• Status: Expired due to Fees

• Current Assignee: Komatsu Ltd.
• Original Assignee: Komatsu Ltd.
• Inventors: Yoshimi, Osamu, Yamaguchi, Hiroyoshi, Shinbo, Tetsuya, Mizui, Seiichi
• Primary Examiner(s): Boudreau, Leo
• Assistant Examiner(s): AZARIAN, SEYED H
• Application Number:
  US09/284,619
• Time in Patent Office: 1,260 Days
• Field of Search: 382/103, 382/104, 382/224, 382/154, 382/291, 382/209, 382/276, 382/107, 382/108, 356/4.01, 356/5.01, 356/394, 348/169, 348/143, 348/147, 345/428, 345/419, 345/421, 345/422
• US Class Current: 382/103
• CPC Class Codes: G06T 7/74 involving reference images or patches

Abstract

In the device according to the present invention, it is possible readily to distinguish between a road of travel and an obstacle in an image, simply using a distance image, even in cases where such a distinction is difficult to make, for instance, when a moving body is inclined during travel or the road forms a slope.

Three-dimensional co-ordinate position data in a three-dimensional co-ordinate system is calculated for each pixel of the distance image, on the basis of two-dimensional co-ordinate position data for each pixel in the distance image and distance data from a reference position for each of the pixels, in such a manner that a three-dimensional distribution of pixels corresponding to a plane and an object to be detected is generated. Therefore, the object to be detected corresponding to groups of pixels having a prescribed height or more with respect to this plane can be distinguished readily from groups of pixels corresponding to the plane, on the basis of this three-dimensional distribution of pixels.

Claims

1. An object detector comprising distance image generating means for measuring a distance from a reference position to an object to be detected present on a plane and generating a distance image of the plane and the object to be detected, and detecting means for detecting the object on the plane by using the distance image generated by the distance image generating means, wherein the object detector comprises:

three-dimensional distribution generating means for calculating three-dimensional co-ordinate position data in a three-dimensional co-ordinates system, for each pixel of the distance image, on the basis of two-dimensional co-ordinate position data for each pixel of the distance image and distance data from the reference position for each of the pixels, dividing a two-dimensional distribution in a depth direction Y and a height direction Z at prescribed intervals and selecting bottom point data thereof, on the basis of the calculated three-dimensional co-ordinate position data for each pixel, determining the plane by planar approximation of the height indicated by the three-dimensional co-ordinate position data for the selected pixels, and generating a three-dimensional distribution of pixels corresponding to the object to be detected; and

wherein

the detecting means detects groups of pixels having a prescribed height or more with reference to the determined plane as the object to be detected.

2. The object detector according to claim 1, characterized in that the object to be detected on the plane is an obstacle on a surface of a road on which a moving body is travelling.

3. The object detector according to claim 1, characterized in that the distance image generating means generates the distance image by matching corresponding points of two images captured by two cameras, and when the three-dimensional distribution is generated by the three-dimensional generating means, pixels in the distance image obtained previously from the distance image generating means which show a matching error for the matching operation that is equal to or above a prescribed threshold value are regarded to be mismatched points and are removed.

4. The object detector according to claim 1, characterized in that when the three-dimensional distribution is generated by the three-dimensional distribution generating means, a relationship between a distance and number of pixels is determined for the distance image previously obtained from the distance image generating means, and pixels having a distance for which the number of pixels is below a prescribed threshold value are regarded to be mismatched points and are removed.

5. The object detector according to claim 1, characterized in that the distance image generating means generates the distance image of the object to be detected including a surface of the object, and when the three-dimensional distribution is generated by the three-dimensional distribution generating means, an edge distance image of the object to be detected representing only edges of the object is obtained by differential processing of the distance image previously obtained from the distance image generating means, and the three-dimensional distribution is generated by using the edge distance image.

6. The object detector according to claim 1, characterized in that the distance image generating means generates an edge distance image of the object to be detected representing only edges of the object, and the three-dimensional distribution generating means generates the three-dimensional distribution by using the edge distance image.

7. The object detector according to claim 1, characterized in that the three-dimensional distribution generating means selects, from all the pixels, those pixels having a height equal to or below a prescribed threshold value on the basis of the calculated three-dimensional co-ordinate position data for each pixel, and determines the plane by planar approximation of the height indicated by the three-dimensional co-ordinate position data for the selected pixels.

8. The object detector according to claim 1, characterized in that the three-dimensional distribution generating means selects, from all the pixels, those pixels having a height within a prescribed range, on the basis of the calculated three-dimensional co-ordinate position data for each pixel, and determines the plane by planar approximation of the height indicated by the three-dimensional co-ordinate position data for the selected pixels.

9. The object detector according to claim 1, characterized in that, on the basis of a three-dimensional distribution representing the three-dimensional distribution of each pixel, the detecting means determines a group of pixels corresponding to the plane, whilst also determining groups of pixels separated by a prescribed height or more from the plane thus determined as detected object candidate point groups, determining a relationship between distances from the reference position and numbers of pixels, with respect to these detected object candidate point groups, regarding pixels of a height for which the number of pixels is equal to or less than a prescribed threshold value as mismatched points and removing same, and detecting the object to be detected from the detected object candidate point groups from which the pixels at these mismatched points have been removed.

10. The object detector according to claim 1, characterized in that the three-dimensional distribution is a distribution of each pixel in a height direction, a width direction and a depth direction;

and the detecting means determines a group of pixels corresponding to the plane, whilst also determining groups of pixels separated by a prescribed height or more from the plane thus determined as detected object candidate point groups, determining a relationship between co-ordinate positions in the width direction and co-ordinate positions in the height direction and a relationship between co-ordinate positions in the depth direction and co-ordinate positions in the height direction, with respect to these detected object candidate point groups, and detecting that groups of pixels which exist continuously in the width direction or depth direction on the basis of these relationships are the object to be detected.

11. An object detector comprising distance image generating means for measuring a distance from a reference position to an object to be detected present on a plane and generating a distance image of the plane and the object to be detected, and detecting means for detecting the object on the plane by using the distance image generated by the distance image generating means, wherein the object detector comprises:

object detecting means for detecting groups of pixels separated by a prescribed height or more from the plane thus calculated as the object; and

three-dimensional distribution generating means for generating a three-dimensional distribution of pixels corresponding to the plane and the object to be detected by calculating three-dimensional co-ordinate position data in a three-dimensional co-ordinate system for groups of pixels, on the basis of two-dimensional co-ordinate position data for the groups of pixels corresponding to the object as detected by the object detecting means and the distance data from the reference position, dividing a two-dimensional distribution in a depth direction Y and a height direction Z at prescribed intervals and selecting bottom point data thereof, on the basis of the calculated three-dimensional co-ordinate position data for each pixel, and determining the plane by planar approximation of the height indicated by the three-dimensional co-ordinate position data for the selected pixels.

12. The object detector according to claim 11, characterized in that the object to be detected on the plane is an object on the surface of a road on which a moving body is travelling.