Maneuverless passive range estimation using monocular image sequences
First Claim
1. In a computerized system including a camera mounted on a moving vehicle, a method of predicting a collision between a foreign moving object and said moving vehicle, the method comprising the steps of:
- acquiring with said camera, consecutively in real time, a plurality of images of said foreign moving object;
detecting said foreign moving object within each of said plurality of images;
identifying two related feature points p1 and p2 on said detected foreign moving object within each of said plurality of images;
calculating ranges r1(t) and r2(t) to said identified feature points p1 and p2 on said detected foreign moving object based on changes in the positions of the feature points p1 and p2 in the sequential images; and
determining that a collision condition is imminent if at a time t*≥
tcurrent in the future if |ri(t*)|≤
Rsafe for i=1 or 2, t*−
tcurrent≥
0 and t*−
tcurrent≤
Tsafe where tcurrent is the time at which the ranges r1(t) and r2(t) to the feature points p1 and p2 are computed andwhere Tsafe and Rsafe define a safe time and a safe distance which allow for the moving vehicle or the foreign moving object to maneuver to avoid a collision.
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Abstract
A method to estimate range to a moving rigid body from a moving platform using a monocular camera. The method does not require the camera platform to maneuver in order to estimate range. The method relies on identification and tracking of certain principal features of the object. The method extracts a silhouette of an object from an obtained image and identifies two principal linear components of the silhouette. A normalized distance between the point of intersection of the two linear components and a centroid of the silhouette is computed, compared to a data set and used to determine a direction of movement of the object.
12 Citations
19 Claims
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1. In a computerized system including a camera mounted on a moving vehicle, a method of predicting a collision between a foreign moving object and said moving vehicle, the method comprising the steps of:
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acquiring with said camera, consecutively in real time, a plurality of images of said foreign moving object; detecting said foreign moving object within each of said plurality of images; identifying two related feature points p1 and p2 on said detected foreign moving object within each of said plurality of images; calculating ranges r1(t) and r2(t) to said identified feature points p1 and p2 on said detected foreign moving object based on changes in the positions of the feature points p1 and p2 in the sequential images; and determining that a collision condition is imminent if at a time t*≥
tcurrent in the future if |ri(t*)|≤
Rsafe for i=1 or 2, t*−
tcurrent≥
0 and t*−
tcurrent≤
Tsafewhere tcurrent is the time at which the ranges r1(t) and r2(t) to the feature points p1 and p2 are computed and where Tsafe and Rsafe define a safe time and a safe distance which allow for the moving vehicle or the foreign moving object to maneuver to avoid a collision. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. In a computerized system including a camera mounted on a moving vehicle, a method of predicting a collision between a foreign moving object and said moving vehicle, the method comprising the steps of
acquiring with said camera, consecutively in real time, a plurality of images of said foreign moving object; -
detecting said foreign moving object within each of said plurality of images; identifying two feature points p1 and p2 on said detected foreign moving object within each of said plurality of images; calculating ranges r1(t) and r2(t) to said identified feature points p1 and p2 on said detected foreign moving object based on changes in the positions of the feature points p1 and p2 in the sequential images; and determining that a collision condition is imminent if at a time t*≥
tcurrent in the future if |ri(t*)|≤
Rsafe for i=1 or 2, t*−
tcurrent≥
0 and t*−
tcurrent≤
Tsafewhere tcurrent is the time at which the ranges r1(t) and r2(t) to the feature points p1 and p2 are computed and where Tsafe and Rsafe define a safe time and a safe distance which allow for the moving vehicle or the foreign moving object to maneuver to avoid a collision; wherein; the two feature points p1 and p2 on said detected foreign moving object satisfy a predetermined geometric relationship with a velocity vector of said detected foreign moving object, said step of identifying said feature points p1 and p2 further comprising the step of determining pixel locations (i1, j1) and (i2, j2) of said feature points p1 and p2 within said image; and the calculating ranges step further includes recursively calculating the range of said detected foreign moving object based on changes in the positions of the feature points p1 and p2 in the sequential images and further based on said predetermined geometric relationship, said step of recursively calculating said range further comprising the step of converting said pixel locations to relative azimuth and elevation angles denoted by β
1, β
2, y1, y2,wherein the step of recursively calculating said range comprises recursively calculating said range where an angle α
is known and is equal to either 0 or π
/2 radians, and the following conditions are defined;(x1, y1, z1) and (x2, y2, z2) represent 3D locations of said feature points (i1, j1) and (i2, j2); [u, v, w] represents a 3D velocity vector of the object; angle α
is the angle between the vectors [u v w] and [x1−
x2 y1−
y2 z1−
z2]; anda determination of whether α
is equal to either 0 or π
/2 is made using an Extended Kalman Filter (EKF) where - View Dependent Claims (11, 12)
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13. In a computerized system including a camera mounted on a moving vehicle, a method of predicting a collision between a foreign moving object and said moving vehicle, the method comprising the steps of:
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acquiring with said camera, consecutively in real time, a plurality of images of said foreign moving object; detecting said foreign moving object within each of said plurality of images; identifying two feature points p1 and p2 on said detected foreign moving object within each of said plurality of images; calculating ranges r1(t) and r2(t) to said identified feature points p1 and p2 on said detected foreign moving object based on changes in the positions of the feature points p1 and p2 in the sequential images; and determining that a collision condition is imminent if at a time t*≥
tcurrent in the future if |ri(t*)|≤
Rsafe for i=1 or 2, t*−
tcurrent≥
0 and t*−
tcurrent≤
Tsafewhere tcurrent is the time at which the ranges r1(t) and r2(t) to the feature points p1 and p2 are computed and where Tsafe and Rsafe define a safe time and a safe distance which allow for the moving vehicle or the foreign moving object to maneuver to avoid a collision; wherein the two feature points p1 and p2 on said detected foreign moving object satisfy a predetermined geometric relationship with a velocity vector of said detected foreign moving object, said step of identifying said feature points p1 and p2 further comprising the step of determining pixel locations (i1, j1) and (i2, j2) of said feature points p1 and p2 within said image; and wherein the calculating the ranges step further includes recursively calculating the range of said detected foreign moving object based on changes in the positions of the feature points p1 and p2 in the sequential images and further based on said predetermined geometric relationship, wherein the step of recursively calculating said range comprises recursively calculating said range where an angle α
is known and is equal to either 0 or π
/2 radians, and the following conditions are defined;(x1, y1, z1) and (x2, y2, z2) represent 3D locations of said feature points (i1, j1) and (i2, j2); [u, v, w] represents a 3D velocity vector of the object; angle α
is the angle between the vectors [u v w] and [x1−
x2 y1−
y2 z1−
z2];said step of determining pixel locations (i1, j1) and (i2, j2) comprises extracting a silhouette of said moving object by image segmentation. - View Dependent Claims (14, 15, 16, 17)
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18. In a computerized system including a camera mounted on a moving vehicle, a method of predicting a collision between a foreign moving object and said moving vehicle, the method comprising the steps of:
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acquiring with said camera, consecutively in real time, a plurality of images of said foreign moving object; detecting said foreign moving object within each of said plurality of images; identifying two feature points p1 and p2 on said detected foreign moving object within each of said plurality of images; calculating ranges r1(t) and r2(t) to said identified feature points p1 and p2 on said detected foreign moving object based on changes in the positions of the feature points p1 and p2 in the sequential images; and determining that a collision condition is imminent if at a time t*≥
tcurrent in the future if |ri(t*)|≤
Rsafe for i=1 or 2, t*−
tcurrent≥
0 and t*−
tcurrent≤
Tsafewhere tcurrent is the time at which the ranges r1(t) and r2(t) to the feature points p1 and p2 are computed and where Tsafe and Rsafe define a safe time and a safe distance which allow for the moving vehicle or the foreign moving object to maneuver to avoid a collision; wherein the two feature points p1 and p2 are two robust feature points p1 and p2 on said detected foreign moving object, where p1 and p2 satisfy a predetermined geometric relationship with a velocity vector of said detected foreign moving object, said step of identifying said feature points p1 and p2 further comprising the step of determining pixel locations (i1, j1) and (i2, j2) of said robust feature points p1 and p2 within said image; and wherein the calculating the ranges step further includes recursively calculating the range of said object based on changes in the positions of the robust feature points p1 and p2 in the sequential images and further based on said predetermined geometric relationship, said step of recursively calculating said range further comprising the step of converting said pixel locations to relative azimuth and elevation angles denoted by β
1, β
2, y1, y2, andwherein said step of determining pixel locations (i1, j1) and (i2, j2) of said robust feature points p1 and p2 within said image comprises the steps of extracting a silhouette of said moving object comprising a plurality of pixels associated with said detected foreign moving object, fitting a straight line to the silhouette using a least squares method wherein said straight line defines a principal axis of said silhouette, projecting all silhouette points to the principal axis, calculating a truncated histogram of said silhouette points, and calculating a centroid and interquartile range (IQR) from said histogram, wherein said robust feature points p1 and p2 comprise two points having a distance of IQR away from the centroid along the principal axis. - View Dependent Claims (19)
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Specification