Object detection and characterization using a LIDAR-based sensor
Systems, apparatuses, and methods for identifying and tracking objects (e.g., debris, particles, space vehicles, etc.) using one or more light detection and ranging (LIDAR)-based sensors are disclosed. Such systems, apparatuses, and methods may be particularly beneficial for detecting millimeter scale and/or sub-millimeter scale objects. Such systems, apparatuses, and methods may be used for detection of objects in space, in the atmosphere, or in the ocean, for example.
1. A light detection and ranging (LIDAR)-based system, comprising:
at least one laser configured to transmit a beam comprising light pulses at a predetermined wavelength and pulse repetition rate;
at least one light-sensitive receiver configured to:
receive light from the beam of light pulses after being reflected off of an object, reemitted after absorption by the object, or both, and
generate a voltage or a current from the received light; and
a computing system configured to receive the generated voltage or current from the at least one light-sensitive receiver and determine, for the object, a location, a distance, a velocity, a change in velocity, a size, a rotation, material properties, or any combination thereof, from the voltage or current received from the at least one light-sensitive receiver, wherein
the pulse repetition rate is set such that the object will be contacted by pulses at least twice when traveling through the volumetric distribution of laser energy at a maximum relative orbital velocity, the beam optimized for surface area.
2. The LIDAR-based system of claim 1 , wherein the at least one laser and the at least one light-sensitive receiver are located on a same vehicle.
3. The LIDAR-based system of claim 1 , wherein the at least one laser and the at least one light-sensitive receiver are located on different vehicles.
4. The LIDAR-based system of claim 1 , wherein the computing system is configured to determine a distance d to the object via:
d
=
t
*
c
2
where c is the speed of light and t is a time between transmission of the beam by the at least one laser and detection of the reflected and/or reemitted light from the object by the at least one light-sensitive receiver.
5. The LIDAR-based system of claim 4 , wherein the object location is determined by using a current location of the LIDAR-based system as a starting point for a vector of length din a direction of the object, an endpoint of which gives the object location.
6. The LIDAR-based system of claim 1 , wherein the object velocity Vis calculated based on measured return signal arrival times as follows:
R
0
=
1
2
c
(
t
r
0
-
t
′
)
R
1
=
1
2
c
(
t
r
1
-
(
t
′
+
τ
)
)
V
=
(
R
1
-
R
0
)
τ
where t r0 and t r1 are receive times of two laser pulses, t′ is a transmit time of a first laser pulse of the two laser pulses, τ is a time delay between the two laser pulses, R 0 and R 1 are ranges at the times t r0 and t r1 , and c is the speed of light.
7. The LIDAR-based system of claim 1 , wherein the object size is determined by measuring a count of photons scattered from a same location during a period of time and relating the count to a physical cross section of the object.
8. The LIDAR-based system of claim 1 , wherein the rotation of the object is determined by:
comparing a wavelength and frequency of light received by the at least one light-sensitive receiver to a wavelength and frequency of the beam transmitted by the at least one laser;
determining whether the received light is Doppler-shifted towards blue, red, or both; and
calculating a rotation rate of the object based on a degree of Doppler shift towards blue, red, or both.
9. The LIDAR-based system of claim 1 , wherein the material properties of the object are determined by measuring a reflectivity R of laser light returning from the object at multiple wavelengths given by:
R
=
(
ε
1
/
2
-
1
)
2
(
ε
1
/
2
+
1
)
2
where ε is a dielectric constant of a material.
10. The LIDAR-based system of claim 1 , wherein an intensity distribution within the shape comprises a Gaussian or flat-top shape.
11. The LIDAR-based system of claim 1 , wherein the at least one light-sensitive receiver comprises a telescope.
12. The LIDAR-based system of claim 1 , wherein the at least one light-sensitive receiver comprises a lens and a photodetector, the lens configured to focus the received light onto the photodetector.
13. The LIDAR-based system of claim 12 , wherein a diameter of the beam matches a field of view (FOV) of the photodetector.
14. The LIDAR-based system of claim 1 , wherein the system comprises a plurality of vehicles that are interconnected.
15. The LIDAR-based system of claim 14 , wherein the plurality of vehicles comprise two or more LIDAR vehicles and at least one framework vehicle connecting the two or more LIDAR vehicles.
16. The LIDAR-based system of claim 15 , wherein each LIDAR vehicle comprises:
a laser of the at least one laser that emits a beam at a unique laser wavelength; and
a light-sensitive receiver of the at least one light-sensitive receiver that is sensitive to the unique wavelength of the laser, wherein
the unique laser wavelength of the beam and the sensitivity of the receiver to the unique wavelength constitute a unique channel for the respective LIDAR vehicle.
17. The LIDAR-based system of claim 16 , wherein each LIDAR vehicle transmits a rotating beam of pulsed laser light within a plane that is different than those defined by rotating beams of other LIDAR vehicles in the system.
18. The LIDAR-based system of claim 17 , wherein
the transmitted rotating beams from the LIDAR vehicles provide a return signal after reflecting off of the object and/or being reemitted by the object, and
the computing system is configured to plot the return signal for each channel as a function of time to calculate the location more precisely.
19. The LIDAR-based system of claim 1 , wherein the computing system is configured to determine velocimetry of the object using two-pulse excitation, the two-pulse excitation comprising:
transmitting two laser pulses, by the at least one laser, that are separated from one another by a fixed optical delay;
collecting signal returns from the transmitted two laser pulses, by the at least one detector;
measuring arrival times of each signal return, by the computing system; and
calculating a range and object motion velocity based on this measurement, by the computing system.
20. The LIDAR-based system of claim 1 , wherein the system comprises:
a laser source vehicle comprising the at least one laser; and
a detector vehicle comprising the at least one light-sensitive receiver, the at least one light-sensitive receiver comprising a telescope with a polarizer, wherein
the detector vehicle has a relative velocity with respect to the laser source vehicle,
the laser source vehicle communicates a direction of the at least one laser and when a respective beam of light from the at least one laser will be transmitted, and
the computing system, based on the voltage or current produced by the received light after passing through the telescope and polarizer and interacting with the light-sensitive receiver, is configured to determine an angle from an observation direction vector and a laser direction vector.
21. The LIDAR-based system of claim 1 , wherein a Mie scattering model is used to derive the size of debris.
22. The LIDAR-based system of claim 1 , wherein multiple lasers are used, each of the multiple lasers configured to transmit a different respective wavelength.
23. A computer-implemented method, comprising:
receiving a generated voltage or current from a light-sensitive receiver, by a computing system, the voltage or the current generated due to a fan beam with a pulse repetition rate set such that an object will be contacted by pulses at least twice when traveling through a volumetric distribution of laser energy of the fan beam at a maximum relative orbital velocity, the fan beam optimized for surface area; and
determining, for an object, a location, a distance, a velocity, a change in velocity, a size, a rotation, material properties, or any combination thereof, from the voltage or current received from the light-sensitive receiver.
24. The computer-implemented method of claim 23 , wherein the computing system is configured to determine a distance d to the object via:
d
=
t
*
c
2
where c is the speed of light and t is a time transmission of the beam by the at least one laser and detection of the reflected and/or reemitted light from the object by the at least one light-sensitive receiver.
25. The computer-implemented method of claim 24 , wherein the object location is determined by using a current location of the LIDAR-based system as a starting point for a vector of length din a direction of the object, an endpoint of which gives the object location.
26. The computer-implemented method of claim 23 , wherein the object velocity Vis calculated based on measured return signal arrival times as follows:
R
0
=
1
2
c
(
t
r
0
-
t
′
)
R
1
=
1
2
c
(
t
r
1
-
(
t
′
+
τ
)
)
V
=
(
R
1
-
R
0
)
τ
where t r0 and t r1 are receive times of two laser pulses, t′ is a transmit time of a first laser pulse of the two laser pulses, τ is a time delay between the two laser pulses, R 0 and R 1 are ranges at the times t r0 and t r1 , and c is the speed of light.
27. The computer-implemented method of claim 23 , wherein the object size is determined by measuring a count of photons scattered from a same location during a period of time and relating the count to a physical cross section of the object.
28. The computer-implemented method of claim 23 , wherein the object rotation is determined by determining a red shift or blue shift of an edge of the object moving toward the sensor and an edge of the object moving away from the of the object using a Doppler equation.
29. The computer-implemented method of claim 23 , wherein the material properties of the object are determined by measuring a reflectivity R of laser light returning from the object at multiple wavelengths given by:
R
=
(
ε
1
/
2
-
1
)
2
(
ε
1
/
2
+
1
)
2
where ε is a dielectric constant of a material.
30. A light detection and ranging (LIDAR)-based system, comprising:
a laser source vehicle comprising at least one laser, the at least one laser configured to transmit a beam comprising light pulses at a predetermined wavelength and pulse repetition rate;
a detector vehicle comprising at least one light-sensitive receiver, a telescope, and a polarizer, the at least one light-sensitive receiver configured to:
receive light from the beam of light pulses after being reflected off of an object, reemitted after absorption by the object, or both, and
generate a voltage or a current from the received light; and
a computing system configured to receive the generated voltage or current from the at least one light-sensitive receiver and determine, for the object, a location, a distance, a velocity, a change in velocity, a size, a rotation, material properties, or any combination thereof, from the voltage or current received from the at least one light-sensitive receiver, wherein
the detector vehicle has a relative velocity with respect to the laser source vehicle,
the laser source vehicle communicates a direction of the at least one laser and when a respective beam of light from the at least one laser will be transmitted, and
the computing system, based on the voltage or current produced by the received light after passing through the telescope and polarizer and interacting with the light-sensitive receiver, is configured to determine an angle from an observation direction vector and a laser direction vector.
31. The LIDAR-based system of claim 30 , wherein the computing system is located on the detector vehicle.
32. The LIDAR-based system of claim 30 , wherein the computing system is configured to determine a distance d to the object via:
d
=
t
*
c
2
where c is the speed of light and t is a time between transmission of the beam by the at least one laser and detection of the reflected and/or reemitted light from the object by the at least one light-sensitive receiver.
33. The LIDAR-based system of claim 32 , wherein the object location is determined by using a current location of the LIDAR-based system as a starting point for a vector of length din a direction of the object, an endpoint of which gives the object location.
34. The LIDAR-based system of claim 30 , wherein the object velocity Vis calculated based on measured return signal arrival times as follows:
R
0
=
1
2
c
(
t
r
0
-
t
′
)
R
1
=
1
2
c
(
t
r
1
-
(
t
′
+
τ
)
)
V
=
(
R
1
-
R
0
)
τ
where t r0 and t r1 are receive times of two laser pulses, t′ is a transmit time of a first laser pulse of the two laser pulses, τ is a time delay between the two laser pulses, R 0 and R 1 are ranges at the times t r0 and t r1 , and c is the speed of light.
35. The LIDAR-based system of claim 30 , wherein the object size is determined by measuring a count of photons scattered from a same location during a period of time and relating the count to a physical cross section of the object.
36. The LIDAR-based system of claim 30 , wherein the rotation of the object is determined by:
comparing a wavelength and frequency of the light received by the at least one light-sensitive receiver to a wavelength and frequency of the beam transmitted by the at least one laser;
determining whether the received light is Doppler-shifted towards blue, red, or both; and
calculating a rotation rate of the object based on a degree of Doppler shift towards blue, red, or both.
37. The LIDAR-based system of claim 30 , wherein the material properties of the object are determined by measuring a reflectivity R of laser light returning from the object at multiple wavelengths given by:
R
=
(
ε
1
/
2
-
1
)
2
(
ε
1
/
2
+
1
)
2
where ε is a dielectric constant of a material.
38. The LIDAR-based system of claim 30 , wherein the computing system is configured to determine velocimetry of the object using two-pulse excitation, the two-pulse excitation comprising:
transmitting two laser pulses, by the at least one laser, that are separated from one another by a fixed optical delay;
collecting signal returns from the transmitted two laser pulses, by the at least one detector;
measuring arrival times of each signal return, by the computing system; and
calculating a range and object motion velocity based on this measurement, by the computing system.
39. The LIDAR-based system of claim 30 , wherein a Mie scattering model is used to derive the size of debris.
40. A light detection and ranging (LIDAR)-based system, comprising:
a plurality of LIDAR vehicles; and
at least one framework vehicle connecting the plurality of LIDAR vehicles, wherein
each of the plurality of LIDAR vehicles comprises:
a laser configured to transmit a beam comprising light pulses at a predetermined wavelength and pulse repetition rate,
a light-sensitive receiver configured to:
receive light from the beam of light pulses after being reflected off of an object, reemitted after absorption by the object, or both, and
generate a voltage or a current from the received light, and
a computing system configured to receive the generated voltage or current from the light-sensitive receivers of the plurality of LIDAR vehicles and determine object location, distance, velocity, change in velocity, size, rotation, material properties, or any combination thereof, from the voltage or current received from the light-sensitive receivers, wherein
the pulse repetition rate is set such that the object will be contacted by pulses at least twice when traveling through the volumetric distribution of laser energy at a maximum relative orbital velocity, the beam optimized for surface area.
41. The LIDAR-based system of claim 40 , wherein the laser of each LIDAR vehicle emits a beam at a unique laser wavelength and the light-sensitive receiver of each LIDAR vehicle is sensitive to the unique wavelength of the laser of that LIDAR vehicle, constituting a unique channel for the respective LIDAR vehicle.
42. The LIDAR-based system of claim 40 , wherein each LIDAR vehicle transmits a rotating beam of pulsed laser light within a plane that is different than those defined by rotating beams of other LIDAR vehicles in the system.
43. The LIDAR-based system of claim 42 , wherein
the transmitted rotating beams from the LIDAR vehicles provide a return signal after reflecting off of the object and/or being reemitted by the object, and
the computing system is configured to plot the return signal for each channel as a function of time to calculate the location more precisely.