3-D imaging multiple target laser radar

• US 6,414,746 B1
• Filed: 11/24/1999
• Issued: 07/02/2002
• Est. Priority Date: 11/24/1999
• Status: Expired due to Term

• Current Assignee: Continental Autonomous Mobility US LLC (Continental AG)
• Original Assignee: Advanced Scientific Concepts, Inc.
• Inventors: Bailey, Howard W., Stettner, Roger
• Primary Examiner(s): Hellner, Mark
• Application Number:
  US09/449,091
• Time in Patent Office: 951 Days
• Field of Search: 356/4.01, 250/332
• US Class Current: 356/4.01
• CPC Class Codes: G01S 17/894 3D imaging with simultaneous measurement of time-of-flight at a 2D array of receiver pixels, e.g. time-of-flight cameras or flash lidar
• CPC Class Codes: G01S 7/4816 of receivers alone
• CPC Class Codes: G01S 7/4863 Detector arrays, e.g. charge-transfer gates

Abstract

A three dimensional imaging device is presented which uses a single pulse from a pulsed light source to detect objects which are obscured by camouflage, fog or smoke but otherwise enveloped by a light-transmitting medium. The device simultaneously operates in two modes, light reflected from the nearest object is processed to form a three-dimensional image by an array of pixels. This first image is based upon the light-pulse transit time recorded in each pixel. Each pixel also contains a high-speed analog memory that sequentially stores reflected signals at a repeated time interval. The first reflection acts as a time base that controls when the analog memory begins or ends the storage sequence. The first return could be from a camouflage net and the amplitudes of the return signals, after the first return, would then be from objects behind the net. Computer processing these amplitudes reveals the three-dimensional nature of the obscured objects.

The device consists of the pulsed light source, optics for collecting the reflected light, a sensor for detecting the light and converting it to electrical data, drive and output electronics for timing and signal conditioning of data generated by the sensors and a computer for processing the sensor data and converting it to a three dimensional image. The sensor collects and processes the light data in a unique manner, first converting it to electricity by a number of alternate detector technologies and then using integrated circuit chips which consist of a two dimensional array of electronic pixels also called unit cells. The two dimensional array defines two dimensions of the image. Stored within each unit cells is data associated with the third dimension, ranges of targets, and amplitudes of target reflections. This data is read out of the integrated circuit chip in the time interval between laser pulses to a processing computer. The processing computer corrects the data and, by means of computer algorithms specific to the device, converts the data to a three-dimensional image of one or more targets. This image may be viewed or processed electronically to isolate targets.

Claims

1. A device for imaging one or more three dimensional objects immersed in a light conducting medium comprising:

a pulsed light source;

means for transmitting light from said pulsed light source into said medium;

optics for collecting light from said medium during the time for light to transit from said pulsed light source, reflect from said objects and be collected by said optics;

a sensor means for detecting said collected light, said sensor means comprising

means for converting said collected light into electrical charge,

chip means comprising

multiplexing and chip output electronics,

a plurality of collection or detection means for collecting or detecting the electrical charge from said conversion means,

a plurality of unit cell processing electronics including memory units for storing data related to a first return transit time for a reflected laser pulse from a target pixel, and additional memory units for storing data related to the amplitude of laser pulse reflections from one or plurality of targets, including control circuitry by which the sampling time intervals of said memory units for storing data related to the amplitude of laser pulse reflections is independently controlled, from unit cell to unit cell and including output amplifier electronics adapted to provide signals to said multiplexing and chip output electronics,

drive electronics for providing voltages and for providing timing for said unit cell processing electronics, output amplifier electronics and said multiplexing and chip output electronics, and

output electronics for conditioning the signals from said memory units for data processing;

a computer for processing data from said output electronics.

2. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1 wherein said unit cell processing electronics, multiplexing and chip output electronics, and drive and output electronics is adapted to read out said data in real time between pulses from said light source.

3. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1 wherein said memory units for storing data related to a first return transit time are digital counters.

4. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1 wherein said memory units for storing data related to a first return transit time are capacitors.

5. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1 wherein said memory units for storing data related to a first return transit time are digital counters and capacitors.

6. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1 wherein the said data related to the first return transit time is obtained by means of disconnection from a ramp voltage.

7. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1 wherein the said data related to the first return transit time is obtained by means of disconnection from a series of clock pulses.

8. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1 wherein the said unit cell processing electronics contains a Schmitt Trigger and Memory means.

9. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 6 wherein the said disconnection from a ramp voltage is caused by Schmitt Trigger and Memory means.

10. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 7 wherein the said disconnection from a series of clock pulses is caused by Schmitt Trigger and Memory means.

11. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 6 wherein the value of the said ramp voltage at disconnection is stored on a analog memory unit.

12. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 11 wherein the said analog memory unit is a capacitor.

13. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 7 wherein the number of said clock pulses at disconnection is stored on a digital memory unit.

14. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 13 wherein the said digital memory unit is a pulse counter.

15. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1 wherein said conversion means is a solid state detector array.

16. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 15 wherein the said solid state detector array is an array of avalanche photodiodes.

17. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 15 wherein the said solid state detector array is a Mercury-Cadmium-Telluride detector array.

18. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 15 wherein the said solid state detector array is a Indium-Gallium-Arsenide detector array.

19. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 15 wherein the said solid state detector array is a silicon detector array.

20. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1 wherein said conversion means is a photocathode.

21. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1 wherein said conversion means and said chip means are contained in a vacuum tube.

22. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1 wherein said conversion means and said chip means are contained in a vacuum tube with an electron amplifier between them.

23. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 22 wherein said electron amplifier is a microchannel plate.

24. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 22 wherein said vacuum tube is situated in a magnetic field parallel to the tube axis.

25. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1 wherein said collection or detection means is an anode.

26. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1 wherein said collection or detection means is a diode.

27. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1 wherein said collection or detection means is a diode, a plurality of which are organized into one chip which are electrically and individually connected, by connection means, to the said unit cell processing electronics, a plurality of which are organized into a separate chip.

28. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1 wherein said collection or detection means is a anode, a plurality of which are organized into one chip which are electrically and individually connected, by connection means, to the said unit cell processing electronics, a plurality of which are organized into a separate chip.

29. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 27 wherein said connection means are conducting bumps.

30. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1 wherein said collection or detection means is included in the said unit cell processing electronics.

31. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1 wherein the said unit cell processing electronics includes transimpedance amplifier means.

32. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1 wherein the said unit cell processing electronics includes amplifier means.

33. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1 wherein the said unit cell processing electronics includes filtering means.

34. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1 wherein the said unit cell processing electronics includes Peak Detector and Storage electronics.

35. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 34 wherein the said Peak Detector and Storage electronics obtains the peak of the reflected laser light pulse.

36. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 35 wherein the said peak of the reflected laser light pulse is stored on a capacitor.

37. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 35 wherein the said Peak Detector and Storage electronics obtains and stores a time sequence of reflected laser light amplitude signals including the peak of the reflected laser light pulse.

38. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 37 wherein the said time sequence of reflected laser amplitude signals including the peak of the reflected light signal are stored by charging a plurality of capacitors that are sequenced in time.

39. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 38 wherein the said charging of a plurality of capacitors is sequenced in time by a shift register.

40. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1 wherein the said unit cell electronics includes means for terminating the information storage of said memory units after a time interval.

41. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1 wherein the said unit cell processing electronics contains buffers between the said memory units for storing data related to a first return transit time and the said additional memory units for storing data related to reflections from one or a plurality of targets.

42. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1 wherein the said additional memory units for storing data related to reflections from one or a plurality of targets are capacitors.

43. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 42 wherein the said capacitors are sequentially charged.

44. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1 wherein the said unit cell electronics or the said drive electronics includes means for initiating the information storage of said memory units after a time interval and for terminating the information storage after a separate time interval.

45. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1, wherein said unit cell processing electronics includes switching means to turn amplifiers off during the laser interpulse period.

93. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 8 wherein the disconnection from a ramp voltage is caused by the said Schmitt Trigger and Memory means.

94. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 8 wherein the disconnection from a series of clock pulses is caused by the said Schmitt Trigger and Memory means.

95. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 28 wherein said connection means are conducting bumps.

96. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 38 wherein the said unit cell electronics includes means for terminating the charging of said capacitors after a time interval.

97. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 42 wherein the said unit cell electronics includes means for initiating the charging of said capacitors after a time interval and for terminating the charging after a separate time interval.

103. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 22 wherein said electron amplifier is a diode array electrically connected to the readout array and impact ionization in the diode array is the amplification means.

104. The device for imaging one or more three dimensional objects immersed in a light conduction medium of claim 1 wherein the said unit cell and processing electronics includes digital storage means for obtaining the transit time to the target and includes means to store a time sequence of reflected laser light amplitude signals not including the peak of the reflected laser light pulse.

46. A sensor means for detecting collected light, said sensor means comprising

means for converting collected light into electrical charge,

chip means comprising

multiplexing and chip output electronics,

a plurality of collection or detection means for collecting or detecting the electrical charge from said conversion means,

a plurality of unit cell processing electronics including memory units for storing data related to a first return transit time for a reflected laser pulse from a target pixel, and additional memory units for storing data related to the amplitude of laser pulse reflections from one or plurality of targets, including control circuitry by which the sampling time intervals of said memory units for storing data related to the amplitude of laser pulse reflections are independently controlled, from unit cell to unit cell and including output amplifier electronics adapted to provide signals to said multiplexing and chip output electronics,

drive electronics for providing voltages and for providing timing for said unit cell processing electronics, output amplifier electronics and said multiplexing and chip output electronics, and

output electronics for conditioning the signals from said memory units for data processing;

a computer for processing data from said output electronics.

47. The sensor means for detecting collected light of claim 46 wherein said unit cell processing electronics, multiplexing and chip output electronics, and drive and output electronics is adapted to read out said data in real time between pulses from said light source.

48. The sensor means for detecting collected light of claim 46 wherein said memory units for storing data related to a first return transit time are digital counters.

49. The device detecting collected light of claim 46 wherein said memory units for storing data related to a first return transit time are capacitors.

50. The sensor means for imaging one or more three dimensional objects immersed in a light conduction medium of claim 46 wherein said memory units for storing data related to a first return transit time are digital counters and capacitors.

51. The sensor means for detecting collected light of claim 46 wherein the said data related to the first return transit time is obtained by means of disconnection from a ramp voltage.

52. The sensor means for detecting collected light of claim 46 wherein the said data related to the first return transit time is obtained by means of disconnection from a series of clock pulses.

53. The sensor means for detecting collected light of claim 46 wherein the said unit cell processing electronics contains a Schmitt Trigger and Memory means.

54. The sensor means for detecting collected light of claim 51 wherein the said disconnection from a ramp voltage is caused by Schmitt Trigger and Memory means.

55. The sensor means for detecting collected light of claim 52 wherein the said disconnection from a series of clock pulses is caused by Schmitt Trigger and Memory means.

56. The sensor means for detecting collected light of claim 51 wherein the value of the said ramp voltage at disconnection is stored on an analog memory unit.

57. The sensor means for detecting collected light of claim 56 wherein the said analog memory unit is a capacitor.

58. The sensor means for detecting collected light of claim 52 wherein the number of said clock pulses at disconnection is stored on a digital memory unit.

59. The sensor means for detecting collected light of claim 58 wherein the said digital memory unit is a pulse counter.

60. The sensor means for detecting collected light of claim 46 wherein said conversion means is a solid state detector array.

61. The sensor means for detecting collected light of claim 60 wherein the said solid state detector array is an array of avalanche photodiodes.

62. The sensor means for detecting collected light of claim 60 wherein the said solid state detector array is a Mercury-Cadmium-Telluride detector array.

63. The sensor means for detecting collected light of claim 60 wherein the said solid state detector array is an Indium-Gallium-Arsenide detector array.

64. The sensor means for detecting collected light of claim 60 wherein the said solid state detector array is a silicon detector array.

65. The sensor means for detecting collected light of claim 46 wherein said conversion means is a photocathode.

66. The sensor means for detecting collected light of claim 46 wherein said conversion means and said chip means are contained in a vacuum tube.

67. The sensor means for detecting collected light of claim 46 wherein said conversion means and said chip means are contained in a vacuum tube with an electron amplifier between them.

68. The sensor means for detecting collected light of claim 67 wherein said electron amplifier is a microchannel plate.

69. The sensor means for detecting collected light of claim 67 wherein said vacuum tube is situated in a magnetic field parallel to the tube axis.

70. The sensor means for detecting collected light of claim 46 wherein said collection or detection means is an anode.

71. The sensor means for detecting collected light of claim 46 wherein said collection or detection means is a diode.

72. The sensor means for detecting collected light of claim 46 wherein said collection or detection means is a diode, a plurality of which are organized into one chip which are electrically and individually connected, by connection means, to the said unit cell processing electronics, a plurality of which are organized into a separate chip.

73. The sensor means for detecting collected light of claim 46 wherein said collection or detection means is a anode, a plurality of which are organized into one chip which are electrically and individually connected, by connection means, to the said unit cell processing electronics, a plurality of which are organized into a separate chip.

74. The sensor means for detecting collected light of claim 72 wherein said connection means are conducting bumps.

75. The sensor means for detecting collected light of claim 46 wherein said collection or detection means is included in the said unit cell processing electronics.

76. The sensor means for detecting collected light of claim 46 wherein the said unit cell processing electronics includes transimpedance amplifier means.

77. The sensor means for detecting collected light of claim 46 wherein the said unit cell processing electronics includes amplifier means.

78. The sensor means for detecting collected light of claim 46 wherein the said unit cell processing electronics includes filtering means.

79. The sensor means for detecting collected light of claim 46 wherein the said unit cell processing electronics includes Peak Detector and Storage electronics.

80. The sensor means for detecting collected light of claim 79 wherein the said Peak Detector and Storage electronics obtains the peak of the reflected laser light pulse.

81. The sensor means for detecting collected light of claim 80 wherein the said peak of the reflected laser light pulse is stored on a capacitor.

82. The sensor means for detecting collected light of claim 80 wherein the said Peak Detector and Storage electronics obtains and stores a time sequence of reflected laser light amplitude signals including the peak of the reflected laser light pulse.

83. The sensor means for detecting collected light of claim 81 wherein the said time sequence of reflected laser amplitude signals including the peak of the reflected light signal are stored by charging a plurality of capacitors that are sequenced in time.

84. The sensor means for detecting collected light of claim 82 wherein the said charging of a plurality of capacitors is sequenced in time by a shift register.

85. The sensor means for detecting collected light of claim 46 wherein the said unit cell electronics includes means for terminating the information storage of said memory units after a time interval.

86. The sensor means for detecting collected light of claim 46 wherein the said unit cell processing electronics contains buffers between the said memory units for storing data related to a first return transit time and the said additional memory units for storing data related to reflections from one or a plurality of targets.

87. The sensor means for detecting collected light of claim 46 wherein the said additional memory units for storing data related to reflections from one or a plurality of targets are capacitors.

88. The sensor means for detecting collected light of claim 86 wherein the said capacitors are sequentially charged.

89. The sensor means for detecting collected light of claim 46 wherein the said unit cell electronics includes means for initiating the information storage of said memory units after a time interval and for terminating the information storage after a separate time interval.

90. The sensor means for detecting collected light of claim 46, wherein said unit cell processing electronics includes switching means to turn amplifiers off during the laser interpulse period.

92. A method for imaging one or more three dimensional objects obscured by reflective or absorptive material but otherwise immersed in a light conducting medium of claim 90 wherein the electrical signals correspond to a time sequence of the amplitudes of the reflected light.

98. The sensor means for detecting collected light of claim 53 wherein disconnection from a ramp voltage is caused by the said Schmitt Trigger and Memory means.

99. The sensor means for detecting collected light of claim 53 wherein disconnection from a series of clock pulses is caused by the said Schmitt Trigger and Memory means.

100. The sensor means for detecting collected light of claim 73 wherein said connection means are conducting bumps.

101. The sensor means for detecting collected light of claim 83 wherein the said unit cell electronics includes means for terminating the charging of said capacitors after a time interval.

102. The sensor means for detecting collected light of claim 87 wherein the said unit cell electronics includes means for initiating the charging of said capacitors after a time interval and for terminating the charging after a separate time interval.

105. The sensor means for detecting collected light of claim 67 wherein said electron amplifier is a diode array electrically connected to the readout array and impact ionization in the diode array is the amplification means.

106. The sensor means for detecting collected light of claim 46 wherein the said unit cell and processing electronics includes digital storage means for obtaining the transit time to the target and includes means to store a time sequence of reflected laser light amplitude signals not including the peak of the reflected laser light pulse.

91. A method for imaging one or more three dimensional objects obscured by reflective or absorptive material but otherwise immersed in a light conducting medium comprising the steps of:

generating a series of pulses of light;

transmitting said light into said medium to the source of obscuration;

collecting light from said source of obscuration during the time of transmission and reflection of light from said source of obsuration;

detecting said collected light

providing timing control from said detected light

providing electrical signals from a plurality of positions on the objects beyond the source of obscuration with a single light pulse,

storing said electrical signals on a plurality of unit cells corresponding to the said plurality of positions on said objects,

providing signals from said storage means,

converting the signals stored on said storage means to a three-dimensional image of the objects.