LADAR SENSOR FOR A DENSE ENVIRONMENT

US 20160003946A1
Filed: 07/03/2014
Published: 01/07/2016
Est. Priority Date: 07/03/2014
Status: Active Grant

First Claim

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1. A ladar system comprising:

a first ladar sensor and a second ladar sensor;

said first ladar sensor havinga laser transmitter with a pulsed laser light output transmitting light at a first wavelength through a diffusing optic for illuminating a scene in a field of view of said first ladar sensor,a time zero reference circuit having a time zero reference output, said time zero reference output adapted to signal the beginning of the pulsed laser light transmission,receiving optics for collecting and conditioning the pulsed laser light reflected from said scene in the field of view,a receive filter which receives light at said first wavelength and transmits light at said first wavelength and blocks light at a second wavelength,a two dimensional array of light sensitive detectors positioned at a focal plane of said receiving optics, and receiving light filtered through said receive filter at said first wavelength, and each of said light sensitive detectors with an output producing an electrical response signal from a reflected portion of said pulsed laser light output,a detector bias circuit connected to a voltage distribution grid of said array of light sensitive detectors,a readout integrated circuit with a clock circuit and a plurality of unit cell electrical circuits, each of said unit cell electrical circuits having an input connected to said clock circuit and another input connected to one of said light sensitive detector outputs, each unit cell electrical circuit having an electrical response signal amplifier,a range measuring circuit connected to the output of each of said electrical response signal amplifiers, said range measuring circuit further connected to the time zero reference output, and adapted to produce a range measurement for each light sensitive detector based on the number of clock cycles occurring between the time zero reference output and the time of arrival of the electrical response signal,said second ladar sensor havinga laser transmitter with a pulsed laser light output transmitting light at a second wavelength through a diffusing optic for illuminating a scene in a field of view of said second ladar sensor,a time zero reference circuit having a time zero reference output, said time zero reference output adapted to signal the beginning of the pulsed laser light transmission,receiving optics for collecting and conditioning the pulsed laser light reflected from said scene in the field of view,a receive filter which receives light at said second wavelength and transmits light at said second wavelength and blocks light at said first wavelength,a two dimensional array of light sensitive detectors positioned at a focal plane of said receiving optics, and receiving light filtered through said receive filter at said second wavelength, and each of said light sensitive detectors with an output producing an electrical response signal from a reflected portion of said pulsed laser light output,a detector bias circuit connected to a voltage distribution grid of said array of light sensitive detectors,a readout integrated circuit with a clock circuit and a plurality of unit cell electrical circuits, each of said unit cell electrical circuits having an input connected to said clock circuit and another input connected to one of said light sensitive detector outputs, each unit cell electrical circuit having an electrical response signal amplifier,a range measuring circuit connected to the output of each of said electrical response signal amplifiers, said range measuring circuit further connected to the time zero reference output, and adapted to produce a range measurement for each light sensitive detector based on the number of clock cycles occurring between the time zero reference output and the time of arrival of the electrical response signal.

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Abstract

A multi-ladar sensor system is proposed for operating in dense environments where many ladar sensors are transmitting and receiving burst mode light in the same space, as may be typical of an automotive application. The system makes use of several techniques to reduce mutual interference between independently operating ladar sensors. In one embodiment, the individual ladar sensors are each assigned a wavelength of operation, and an optical receive filter for blocking the light transmitted at other wavelengths, an example of wavelength division multiplexing (WDM). Each ladar sensor, or platform, may also be assigned a pulse width selected from a list, and may use a pulse width discriminator circuit to separate pulses of interest from the clutter of other transmitters. Higher level coding, involving pulse sequences and code sequence correlation, may be implemented in a system of code division multiplexing, CDM. A digital processor optimized to execute mathematical operations is described which has a hardware implemented floating point divider, allowing for real time processing of received ladar pulses, and sequences of pulses.

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40 Claims

1. A ladar system comprising:
- a first ladar sensor and a second ladar sensor;
  
  said first ladar sensor havinga laser transmitter with a pulsed laser light output transmitting light at a first wavelength through a diffusing optic for illuminating a scene in a field of view of said first ladar sensor,a time zero reference circuit having a time zero reference output, said time zero reference output adapted to signal the beginning of the pulsed laser light transmission,receiving optics for collecting and conditioning the pulsed laser light reflected from said scene in the field of view,a receive filter which receives light at said first wavelength and transmits light at said first wavelength and blocks light at a second wavelength,a two dimensional array of light sensitive detectors positioned at a focal plane of said receiving optics, and receiving light filtered through said receive filter at said first wavelength, and each of said light sensitive detectors with an output producing an electrical response signal from a reflected portion of said pulsed laser light output,a detector bias circuit connected to a voltage distribution grid of said array of light sensitive detectors,a readout integrated circuit with a clock circuit and a plurality of unit cell electrical circuits, each of said unit cell electrical circuits having an input connected to said clock circuit and another input connected to one of said light sensitive detector outputs, each unit cell electrical circuit having an electrical response signal amplifier,a range measuring circuit connected to the output of each of said electrical response signal amplifiers, said range measuring circuit further connected to the time zero reference output, and adapted to produce a range measurement for each light sensitive detector based on the number of clock cycles occurring between the time zero reference output and the time of arrival of the electrical response signal,said second ladar sensor havinga laser transmitter with a pulsed laser light output transmitting light at a second wavelength through a diffusing optic for illuminating a scene in a field of view of said second ladar sensor,a time zero reference circuit having a time zero reference output, said time zero reference output adapted to signal the beginning of the pulsed laser light transmission,receiving optics for collecting and conditioning the pulsed laser light reflected from said scene in the field of view,a receive filter which receives light at said second wavelength and transmits light at said second wavelength and blocks light at said first wavelength,a two dimensional array of light sensitive detectors positioned at a focal plane of said receiving optics, and receiving light filtered through said receive filter at said second wavelength, and each of said light sensitive detectors with an output producing an electrical response signal from a reflected portion of said pulsed laser light output,a detector bias circuit connected to a voltage distribution grid of said array of light sensitive detectors,a readout integrated circuit with a clock circuit and a plurality of unit cell electrical circuits, each of said unit cell electrical circuits having an input connected to said clock circuit and another input connected to one of said light sensitive detector outputs, each unit cell electrical circuit having an electrical response signal amplifier,a range measuring circuit connected to the output of each of said electrical response signal amplifiers, said range measuring circuit further connected to the time zero reference output, and adapted to produce a range measurement for each light sensitive detector based on the number of clock cycles occurring between the time zero reference output and the time of arrival of the electrical response signal.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
- - 2. The ladar system of claim 1 wherein said first ladar sensor is mounted to a vehicle.
  - 3. The ladar system of claim 1 wherein said first ladar sensor has a voltage sampling circuit connected to the output of each of said electrical response signal amplifiers.
  - 4. The ladar system of claim 3 wherein said first ladar sensor has an analog to digital converter connected to each of said voltage sampling circuits, and said analog to digital converter is adapted to produce a set of digitized analog samples.
  - 5. The ladar system of claim 4 wherein said first ladar sensor has a digital processor connected to an output of said analog to digital converter, said digital processor adapted to execute signal processing operations on said digitized analog samples.
  - 6. The ladar system of claim 5 wherein said digital processor has a floating point hardware divide circuit.
  - 7. The ladar system of claim 5 wherein said digital processor executes an algorithm on the digitized analog samples selected from the set of;
    - a Fourier transform, convolution, integration, differentiation, pulse width discrimination, code sequence correlation, finite impulse response filtering, infinite impulse response filtering, phase measurement, and curve fitting using the least squares method.
  - 8. The ladar system of claim 1 wherein said laser transmitter of the first ladar sensor comprises an electrically pumped semiconductor laser formed in a semiconducting gain medium with at least one element selected from the set of indium, gallium, arsenic, phosphorus.
  - 9. The ladar system of claim 1 wherein the laser transmitter of the first ladar sensor comprises an optically pumped solid state laser formed in a gain medium selected from the set of yttrium aluminum garnet, erbium doped glass, neodymium doped yttrium aluminum garnet, and erbium doped yttrium aluminum garnet.
  - 10. The ladar system of claim 1 wherein said first ladar sensor has the two dimensional array of light sensitive detectors mounted directly to the readout integrated circuit.
  - 11. The ladar system of claim 2 wherein said first ladar sensor is integrated into an assembly selected from the set of;
    - a turn signal, taillight, parking light, mirror assembly, and brake light.
  - 12. The ladar system of claim 2 wherein said vehicle further has at least one two dimensional imaging camera sighted to have a field of view overlapping the field of view of the first ladar sensor, and said vehicle further having a digital processor adapted to merge the data from said first ladar sensor with data from said two dimensional imaging camera.
  - 13. The ladar system of claim 8 wherein said laser transmitter is an array of semiconductor lasers modulated by a current controlled by at least one transistor.
  - 14. The ladar system of claim 2 wherein said vehicle also has a duplex radio link and radio antenna adapted to receive radio transmissions.
  - 15. The ladar system of claim 1 wherein said electrical response signal amplifiers each have a storage capacitor and programming circuitry adapted to provide a programmable reference voltage to an amplifier input.
  - 16. The ladar system of claim 1 wherein said electrical response signal amplifiers each have a storage capacitor and programming circuitry adapted to provide a programmable feedback control voltage to an amplifier feedback circuit.

17. A ladar system comprising:
- a first ladar sensor and a second ladar sensor;
  
  said first ladar sensor havinga semiconductor laser transmitter with a pulsed laser light output transmitting light with a first pulse width through a diffusing optic for illuminating a scene in a field of view of said first ladar sensor,a time zero reference circuit having a time zero reference output, said time zero reference output adapted to signal the beginning of the pulsed laser light transmission,receiving optics for collecting and conditioning the pulsed laser light reflected from said scene in the field of view,a two dimensional array of light sensitive detectors positioned at a focal plane of said receiving optics, and each of said light sensitive detectors with an output producing an electrical pulse from a reflected portion of said pulsed laser light output,a detector bias circuit connected to a voltage distribution grid of said array of light sensitive detectors,a readout integrated circuit with a clock circuit and a plurality of unit cell electrical circuits, each of said unit cell electrical circuits having an input connected to said clock circuit and another input connected to one of said light sensitive detector outputs, each unit cell electrical circuit having an electrical pulse amplifier adapted to amplify the electrical pulses,a pulse width discriminator adapted to receive electrical pulses from each unit cell, and to pass through valid electrical pulses of said first pulse width, and to block pulses of other pulse widths,a range measuring circuit adapted to measure range for each unit cell based on the number of clock cycles between the time zero reference pulse, and the time of arrival of said valid electrical pulses,said second ladar sensor havinga semiconductor laser transmitter with a pulsed laser light output transmitting light with a second pulse width through a diffusing optic for illuminating a scene in a field of view of said second ladar sensor,a time zero reference circuit having a time zero reference output, said time zero reference output adapted to signal the beginning of the pulsed laser light transmission, receiving optics for collecting and conditioning the pulsed laser light reflected from said scene in the field of view,a two dimensional array of light sensitive detectors positioned at a focal plane of said receiving optics, and each of said light sensitive detectors with an output producing an electrical pulse from a reflected portion of said pulsed laser light output,a detector bias circuit connected to a voltage distribution grid of said array of light sensitive detectors,a readout integrated circuit with a clock circuit and a plurality of unit cell electrical circuits, each of said unit cell electrical circuits having an input connected to said clock circuit and another input connected to one of said light sensitive detector outputs, each unit cell electrical circuit having an electrical pulse amplifier adapted to amplify the electrical pulses,a pulse width discriminator adapted to receive electrical pulses from each unit cell, and to pass through valid electrical pulses of said second pulse width, and to block pulses of other pulse widths,a range measuring circuit adapted to measure range for each unit cell based on the number of clock cycles between the time zero reference pulse, and the time of arrival of said valid electrical pulses.
- View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
- - 18. The ladar system of claim 17 wherein said first ladar sensor is mounted to a vehicle.
  - 19. The ladar system of claim 17 wherein said first ladar sensor has a voltage sampling circuit connected to the output of each of said electrical response signal amplifiers.
  - 20. The ladar system of claim 19 wherein said first ladar sensor has an analog to digital converter connected to each of said voltage sampling circuits, and said analog to digital converter adapted to produce a set of digitized analog samples.
  - 21. The ladar system of claim 20 wherein said first ladar sensor has a digital processor connected to an output of said analog to digital converter, said digital processor adapted to execute signal processing operations on said digitized analog samples.
  - 22. The ladar system of claim 21 wherein said digital processor has a floating point hardware divide circuit.
  - 23. The ladar system of claim 21 wherein said digital processor executes an algorithm on the digitized analog samples selected from the set of;
    - a Fourier transform, convolution, integration, differentiation, pulse width discrimination, code sequence correlation, finite impulse response filtering, infinite impulse response filtering, phase measurement, and curve fitting using the least squares method.
  - 24. The ladar system of claim 17 wherein said first ladar sensor has a laser transmitter comprising an electrically pumped semiconductor laser formed in a semiconducting gain medium with at least one element selected from the set of indium, gallium, arsenic, phosphorus.
  - 25. The ladar system of claim 17 wherein said first ladar sensor has the two dimensional array of light sensitive detectors mounted directly to the readout integrated circuit.
  - 26. The ladar system of claim 18 wherein said first ladar sensor is integrated into an assembly selected from the set of;
    - a turn signal, taillight, parking light, mirror assembly, and brake light.
  - 27. The ladar system of claim 18 wherein said vehicle further has at least one two dimensional imaging camera sighted to have a field of view overlapping the field of view of the first ladar sensor, and said vehicle further having a digital processor adapted to merge the data from said first ladar sensor with data from said two dimensional imaging camera.
  - 28. The ladar system of claim 17 wherein said laser transmitter is an array of semiconductor lasers modulated by a current controlled by at least one transistor.
  - 29. The ladar system of claim 18 wherein said vehicle also has a duplex radio link and radio antenna adapted to receive radio transmissions.

30. A ladar system comprising:
- a first ladar sensor and a second ladar sensor;
  
  said first ladar sensor havinga semiconductor laser transmitter with a laser light output transmitting a first coded sequence of light pulses through a diffusing optic for illuminating a scene in a field of view of said first ladar sensor,a time zero reference circuit having a time zero reference output, said time zero reference output adapted to signal the beginning of the transmission of the first coded sequence of light pulses,receiving optics for collecting and conditioning the coded sequence of light pulses reflected from said scene in the field of view,a two dimensional array of light sensitive detectors positioned at a focal plane of said receiving optics, and each of said light sensitive detectors converting the reflected portion of said first coded sequence of light pulses into a first coded sequence of electrical pulses,a detector bias circuit connected to a voltage distribution grid of said array of light sensitive detectors,a readout integrated circuit with a clock circuit and a plurality of unit cell electrical circuits, each of said unit cell electrical circuits having an input connected to said clock circuit and another input connected to one of said light sensitive detector outputs, each unit cell electrical circuit having an electrical pulse amplifier adapted to amplify the first coded sequence of electrical pulses,a code sequence correlator adapted to receive electrical signals from each unit cell, and to detect and validate said first coded sequence of electrical pulses, and to reject other electrical signals,a range measuring circuit adapted to measure a range for each unit cell, based on the number of clock cycles between the time zero reference pulse, and the time of arrival of said first coded sequence of electrical pulses,said second ladar sensor havinga semiconductor laser transmitter with a laser light output transmitting a second coded sequence of light pulses through a diffusing optic for illuminating a scene in a field of view of said second ladar sensor,a time zero reference circuit having a time zero reference output, said time zero reference output adapted to signal the beginning of the transmission of the second coded sequence of light pulses,receiving optics for collecting and conditioning the coded sequence of light pulses reflected from said scene in the field of view,a two dimensional array of light sensitive detectors positioned at a focal plane of said receiving optics, and each of said light sensitive detectors converting the reflected portion of said second coded sequence of light pulses into a second coded sequence of electrical pulses,a detector bias circuit connected to a voltage distribution grid of said array of light sensitive detectors,a readout integrated circuit with a clock circuit and a plurality of unit cell electrical circuits, each of said unit cell electrical circuits having an input connected to said clock circuit and another input connected to one of said light sensitive detector outputs, each unit cell electrical circuit having an electrical pulse amplifier adapted to amplify the second coded sequence of electrical pulses,a code sequence correlator adapted to receive electrical signals from each unit cell, and to detect and validate said second coded sequence of electrical pulses, and to reject other electrical signals,a range measuring circuit adapted to measure a range for each unit cell, based on the number of clock cycles between the time zero reference pulse, and the time of arrival of said second coded sequence of electrical pulses.
- View Dependent Claims (31, 32, 33, 34, 35, 36, 37, 38, 39)
- - 31. The ladar system of claim 30 wherein said first ladar sensor is mounted to a vehicle.
  - 32. The ladar system of claim 31 wherein said first coded sequence of light pulses indicates vehicle specific information.
  - 33. The ladar system of claim 30 wherein said first ladar sensor has a voltage sampling circuit connected to the output of each of said electrical pulse amplifiers.
  - 34. The ladar system of claim 33 wherein said first ladar sensor has an analog to digital converter connected to each of said voltage sampling circuits, and said analog to digital converter adapted to produce a set of digitized analog samples.
  - 35. The ladar system of claim 34 wherein said first ladar sensor has a digital processor connected to an output of said analog to digital converter, said digital processor adapted to execute signal processing operations on said digitized analog samples.
  - 36. The ladar system of claim 30 wherein said first ladar sensor has a laser transmitter comprising an electrically pumped semiconductor laser formed in a semiconducting gain medium with at least one element selected from the set of indium, gallium, arsenic, phosphorus.
  - 37. The ladar system of claim 31 wherein said first ladar sensor is integrated into an assembly selected from the set of;
    - a turn signal, taillight, parking light, mirror assembly, and brake light.
  - 38. The ladar system of claim 31 wherein said vehicle further has at least one two dimensional imaging camera sighted to have a field of view overlapping the field of view of the first ladar sensor, and said vehicle further having a digital processor adapted to merge the data from said first ladar sensor with data from said two dimensional imaging camera.
  - 39. The ladar system of claim 31 wherein said vehicle also has a duplex radio link and radio antenna adapted to receive radio transmissions.

40. A ladar sensor comprising:
- a semiconductor laser transmitter with a laser light output transmitting a modulated burst of light through a diffusing optic for illuminating a scene in a field of view of said ladar sensor,a time zero reference circuit having a time zero reference output, said time zero reference output adapted to signal the beginning of the transmission of said modulated burst of light,receiving optics for collecting and conditioning the modulated burst of light reflected from said scene in the field of view,a two dimensional array of light sensitive detectors positioned at a focal plane of said receiving optics, and each of said light sensitive detectors converting the reflected portion of said modulated burst of light into a modulated electrical burst,a detector bias circuit connected to a voltage distribution grid of said array of light sensitive detectors,a readout integrated circuit with a clock circuit and a plurality of unit cell electrical circuits, each of said unit cell electrical circuits having an input connected to said clock circuit and another input connected to one of said light sensitive detector outputs, each unit cell electrical circuit having an electrical amplifier adapted to amplify the modulated electrical burst,voltage sampling circuit connected to the output of each of said electrical amplifiers, and adapted to produce a set of analog samples of said modulated electrical burst,an analog to digital converter connected to each of said voltage sampling circuits, and said analog to digital converter adapted to produce a set of digitized analog samples for each unit cella digital processor with a hardware implemented floating point divide unit adapted to execute a mathematical algorithm on said digitized analog samples for each unit cell, and to thereby demodulate said modulated electrical burst from each unit cell,and said digital processor also adapted to measure a range for each unit cell, based on the number of clock cycles between the time zero reference output, and the time of arrival of said modulated electrical burst.

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Current Assignee
Continental Autonomous Mobility US LLC (Continental AG)
Original Assignee
Advanced Scientific Concepts, Inc.
Inventors
Gilliland, Patrick, Bailey, Howard, Stettner, Roger, Kataria, Nitin

Granted Patent

US 9,575,184 B2
Time in Patent Office

Days
Field of Search
US Class Current

1/1
CPC Class Codes

G01S 17/10   using transmission of inter...

G01S 17/87   Combinations of systems usi...

G01S 17/894   3D imaging with simultaneou...

G01S 17/931   of land vehicles

G01S 7/4816   of receivers alone

G01S 7/484   Transmitters

G01S 7/486   Receivers

G01S 7/4863   Detector arrays, e.g. charg...

LADAR SENSOR FOR A DENSE ENVIRONMENT

First Claim

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Abstract

298 Citations

40 Claims

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LADAR SENSOR FOR A DENSE ENVIRONMENT

First Claim

4 Assignments

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0 Petitions

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Accused Products

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Abstract

298 Citations

40 Claims

Specification

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Solutions

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