Collision avoidance system

Claim 2

The system of claim 1 further comprising first vehicle warning means for issuing a collision warning in the event that said predicted separation is below a preset minimum value.

Claim 3

The system of claim 2 further comprising vehicle control means (18) for implementing collision avoidance maneuvers in response to said collision warning.

Claim 4

The system of claim 1 wherein said rangefinder scanner means further comprises a transmission channel for transmitting a ranging pulse and a receiving channel for scanning at least one range interval subsequent to transmission of said ranging pulse in order to detect said ranging pulse reflected from said target vehicle.

Claim 5

The system of claim 4 wherein said rangefinder scanner means determines target range based upon the elapsed time between transmission of said ranging pulse and detection of said reflected pulse.

Claim 6

The system of claim 5 wherein said receiving channel further comprises framing mirror means (28), primary mirror means (30), strip mirror means (32), rotating scanning disc means (34) having a plurality of scanning disc reflectors (46), collection optic means (36) and detector means (40).

Claim 7

The system of claim 6 wherein said framing mirror means (28) oscillates to conduct a linear scan of a scene, said primary mirror means (30) focusing said linear scan at said strip mirror means (32), said scanning disc reflectors (46) scanning said linear image received from said strip mirror means (32) pixel by pixel and transmitting said pixel image to said collection optic means (36), said collection optic means focusing said pixel image onto said detector means (40).

Claim 8

The system of claim 7 wherein said collection optic means (36) further comprises a collection mirror and a relay mirror (38).

Claim 9

The system of claim 7 wherein said detector means (40) comprise a linear detector array (40).

Claim 10

The system of claim 9 wherein said transmission channel further comprises radiation source means (42) for transmitting a pulse of radiation toward a pixel in the scene to be scanned.

Claim 11

The system of claim 10 wherein said transmission channel further comprises a pulsed radiation source (42) and transmission mirror means (44), said pulsed radiation source (42) transmitting a pulse of light toward said transmission mirror means (44), said transmission mirror means (44) transmitting said pulse toward at least a portion of at least one of said rotating scanning disc reflectors (46), said pulse being reflected by said scanning disc reflector (46), strip mirror means, primary mirror means and framing mirror means toward a pixel in the scene to be scanned.

Claim 12

The system of claim 11 wherein said rangefinder scanner means queries said detector means for at least one range interval subsequent to transmission of said pulse in order to detect a reflected pulse.

Claim 13

The system of claim 12 wherein said rangefinder canner means determines the range of a target based upon (i) the optical displacement between zero at the time of transmission of said pulse and detection of said reflected pulse, and (ii) the rate of rotation of said rotating scanning disc means.

Claim 14

The system of claim 13 wherein said rangefinder scanner means determines azimuth and elevation angle of a target based upon the position of the pixel in the scene.

Claim 15

The system of claim 14 wherein said processor determines the predicted separation distance between said first vehicle and the target at the time of intercept, W p , as follows: where W o = the separation of sad first vehicle and target at the instant the range and angle data were taken; W̊ = the rate of change of the separation between the vehicles; = the rate of change of W; and t i = the time to intercept.

Claim 16

The system of claim 12 wherein said rangefinder scanner means queries said detector for at least two range intervals subsequent to transmission of said pulse prior to transmission of the next pulse.

Claim 17

The system of claim 12 where said rangefinder scanner means determines range R from: D = π 45 f s ωrpm R x 10⁻⁸ meters where D = the displacement distance along the detector array between transmission of said pulse and detection of said reflected pulse; f s = the receiving channel focal length; and ω rpm = angular rate rotation of said scanning disc.

Claim 18

The system of claim 11 wherein said rangefinder scanner means operates at a frame rate of approximately 60 Hertz.

Claim 19

The system of claim 11 wherein said rangefinder scanner means has a field of view in one direction of at least about 60°.

Claim 20

The system of claim 11 wherein said rangefinder scanner means has a field of view in one direction of at least about 6°.

Claim 21

The collision avoidance system of claim 1 further comprising retroreflection means associated with said target.

Claim 22

The collision avoidance system of claim 21 wherein said retroreflection means comprises at least one cube corner reflector (48).

Claim 23

The collision avoidance system of claim 1 further comprising detector thresholding means for eliminating spurious responses.

Claim 24

The collision avoidance system of claim 1 further comprising equalization means for substantially equalizing detector response irrespective of target distance.

Claim 25

A rangefinder scanner (12) comprising framing mirror means (28); primary mirror means (30); strip mirror means (32); rotating scanning disc means (34) having a plurality of concave reflectors (46) disposed in an arc on one side thereof; collection optic means (36); and detector means (40), said framing mirror means (28) conducting a linear scan of a scene in a first direction and directing said linear scan toward said primary mirror means (30), said primary mirror means (30) focusing said linear scan onto said strip mirror means (32), said concave reflectors (46) scanning said linear image received from said strip mirror means (32) pixel by pixel in a second direction, and directing said image to said collection optic means (36) which focuses said image onto said detector means (40); pulse transmission means (42) for transmitting a pulse of light toward a pixel in the scene to be scanned; range determination means for determining the range of a target in the scene based upon the time elapsed between transmission of said pulse and detection of a pulse reflected from the target.

Claim 26

The rangefinder scanner of claim 25 wherein said detector means further comprises a linear detector array (40).

Claim 27

The rangefinder scanner of claim 26 wherein said range determination means determines range based upon the optical displacement along said array between time zero at transmission of said pulse and detection of said reflected pulse, and the rate of rotation of said scanning disc.

Claim 28

The rangefinder scanner of claim 27 wherein said detector array (40) is queried for at least one range interval subsequent to transmission of said pulse.

Claim 29

The rangefinder scanner of claim 28 wherein the detector is queried for at least two range intervals subsequent to transmission of said pulse.

Claim 30

The rangefinder scanner of claim 29 wherein said framing mirror means (28) and said rotating scanning disc (34) define a staggered overscan scanning pattern.

Claim 31

The rangefinder scanner of claim 30 wherein every other scanning disc reflector (46) is shifted by a distance equal to one pixel in order to optically perform said staggered overscan.

Claim 32

The rangefinder scanner of claim 25 wherein said primary mirror means (30), scanning disc reflector (46) and collection optic means (36) have a relatively long focal length as compared to their package size.

Claim 33

The rangefinder scanner of claim 32 wherein said focal length is on the order of about 0.75 m and the package size is 15000 cubic meters, approximately.

Claim 34

The rangefinder scanner of claim 25 further comprising retroreflector means associated with a target to be ranged.

Claim 35

The rangefinder scanner of claim 34 wherein said retroreflector means comprises at least one cube corner reflector (48).

Claim 36

The rangefinder scanner of claim 30 further comprising threshold means for rejecting detector signals below a predetermined value.

Claim 37

A rangefinder method comprising the steps of - providing a rangefinder scanner having transmission means for transmitting a light pulse toward a pixel in a scene and receiving channel means for receiving and detecting said pulse reflected from a target, said receiving channel means including rotating scanning disc means and detector means; - activating said transmission means to emit a light pulse toward a pixel in the scene; - querying said detector means for at least one range interval subsequent to transmission of said pulse to detect said pulse reflected from a target in the scene; and - determining the range of the target based upon the elapsed time between transmission of said pulse and detection of said reflected pulse.

Claim 38

The rangefinder method of claim 37 further comprising the step of determining said elapsed time based upon the speed of rotation of said rotating scanning disc means.

Claim 39

A collision avoidance method comprising - providing a rangefinder scanner associated with a vehicle for scanning a scene, said rangefinder scanner including framing mirror means, primary mirror means, strip mirror means, rotating scanning disc means having a plurality of concave reflectors disposed thereon, collection optic means, detector means and light pulse transmission means, said framing mirror means conducting a linear scan of a scene in a first direction, said primary mirror means focusing said linear scan onto said strip mirror means, said concave scanning disc reflectors scanning said linear image received from said strip mirror means in a second direction, said collection optic means focusing said scanned image onto said detector means; - transmitting a pulse of light toward a pixel of the scene; - querying said detector means for at least one range interval subsequent to transmission of said pulse in order to detect said light pulse reflected from a target in the scene; - determining the optical displacement between the time zero transmission of said pulse and detection of said reflected light pulse; - determining the range of the target based upon said optical displacement and the speed of rotation of said scanning disc means; - determining the angle of the target based upon the position of the ranged pixel in the scene; - determining from said range and angle data the separation distance and predicted separation distance at the time of intercept of said vehicle and said target; - emitting a collision warning in the event that the predicted separation distance is blow a predetermined minimum value.

Claim 40

The method of claim 39 further comprising the step of effecting collision avoidance maneuvers in response to said collision warning.

Claim 41

The method of claim 39 wherein said step of determining the range of the target further comprises determining the range, R, from the equation: D = π 45 f s ωrpm R x 10⁻⁸ meters where D = the displacement distance along the detector array between transmission of said pulse and detection of said reflected pulse; f s = the receiving channel focal length; and ω rpm = angular rate rotation of said scanning disc.

Claim 42

The method of claim 39 further comprising conducting multiple ranging scans of the scene.

Claim 43

The method of claim 39 wherein said step of determining predicted separation distance comprises solving the equation where W o = the separation of sad first vehicle and target at the instant the range and angle data were taken; W̊ = the rate of change of the separation between the vehicles; = the rate of change of W; and t i = the time to intercept.

Claim 44

The method of claim 39 wherein said step of determining the range of the target further comprises conducting a staggered overscan of the scene.

Claim 45

The method of claim 39 further comprising the step of providing retroreflector means associated with a target.

Claim 46

A collision avoidance system associated with a subject vehicle for detecting and tracking at least one target and predicting the separation distance between the subject vehicle and each target at the time of intercept, the system operating under all variety of road geometries, vehicle speeds and traffic fields encountered in ordinary driving situations, the system comprising - rangefinder scanner means mounted to the subject vehicle for determining the range and angle of each target, said rangefinder scanner having a high pixel rate, a relatively wide field of view and high spatial resolution; - processor means for tracking target range and angle, calculating target velocity and acceleration, and predicting the separation distance of said target and the subject vehicle at the time of intercept, said processor means emitting a collision warning in the event that said predicted separation distance is less than a predetermined value.

Claim 47

The system of claim 46 wherein said pixel range rate is approximately 300.000 Hertz.

Claim 48

The system of claim 46 wherein said rangefinder scanner means has a spatial resolution on the order of about 0.25° x 0.25°.

Claim 49

The system of claim 46 wherein said rangefinder scanner means has a frame rate of about 60 Hertz.

Claim 50

The system of claim 46 wherein said rangefinder scanner means has a field of view of about 60° x 6°.

Claim 51

The system of claim 46 further comprising retroreflector means associated with said target.