Imaging lidar system
First Claim
1. A method of detecting and imaging an object enveloped by a backscattering medium which is at least partially transmitting to light including the steps of:
- selectively generating short pulses of light;
projecting said short pulses of light toward the backscattering medium and at an object enveloped by the medium;
detecting said pulses of light reflected back from said object after a time delay corresponding to the round-trip propagation time of said light pulses to and from said object; and
converting said detected pulses of light to a video image of said object;
wherein said step of detecting said reflected pulses of light further comprises the steps of;
detecting a first image of the object against the backscattered light from the backscattering medium;
detecting a second image of the shadow of the object against the backscattered light from the backscattering medium; and
subtracting the first image from the second image to improve detectability and imaging of the object.
1 Assignment
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Accused Products
Abstract
A novel system for remote detection and imaging of underwater objects is presented. In accordance with the present invention, a laser is used to generate short pulses of light with pulse widths on the order of nanoseconds. The laser light is expanded by optics and projected down towards the surface of the water and to an object. Intensified CCD (charge coupled device) cameras (preferably two) are electronically shuttered after the time delay corresponding to the round trip propagation time and from to the object. This timing eliminates light scattered by the water from in front of and behind the object. As a result, the veiling luminance of the water is greatly attenuated and faint target signatures can be seen. The resulting gated images (displayed on a CRT) have sufficient spatial resolution to classify and/or identify the object. The imaging lidar system of the present invention takes advantage of the fact that all opaque targets will cast a shadow. The exposure of the two cameras in the system are timed such that one camera gives an image of the object against the backscattered light from the water while the other camera gives an image of the shadow of the object against the backscattered light. These two images are then subtracted to improve the detectability of the object.
121 Citations
40 Claims
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1. A method of detecting and imaging an object enveloped by a backscattering medium which is at least partially transmitting to light including the steps of:
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selectively generating short pulses of light; projecting said short pulses of light toward the backscattering medium and at an object enveloped by the medium; detecting said pulses of light reflected back from said object after a time delay corresponding to the round-trip propagation time of said light pulses to and from said object; and converting said detected pulses of light to a video image of said object; wherein said step of detecting said reflected pulses of light further comprises the steps of; detecting a first image of the object against the backscattered light from the backscattering medium; detecting a second image of the shadow of the object against the backscattered light from the backscattering medium; and subtracting the first image from the second image to improve detectability and imaging of the object. - View Dependent Claims (2, 3, 4, 6, 7, 8, 9, 10, 13, 14, 15)
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5. The method of claim I including:
colorizing the subtracted image to assist in identification of the object.
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11. The method of claim I wherein:
said backscattering medium is water and wherein said pulses of light are projected toward a surface of the water. - View Dependent Claims (12)
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16. An apparatus for detecting and imaging an object enveloped by a backscattering medium which is at least partially transmitting to light comprising:
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generating means for selectively generating short pulses of light; projecting means for projecting said short pulses of light toward the backscattering medium and at an object enveloped by the medium; detecting means for detecting said pulses of light reflected back from said object after a time delay corresponding to the round-trip propagation time of said light pulses to and from said object; and converting means for converting said detected pulses of light to a video image of said object; wherein said detecting means further comprises; first detecting means for detecting a first image of the object against the backscattered light from the backscattering medium; second detecting means for detecting a second image of the shadow of the object against the backscattered light from the backscattering medium; and means for subtracting the first image from the second image to improve detectability and imaging of the object. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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31. A method of detecting and imaging an object enveloped by a backscattering medium which is at least partially transmitting to light including the steps of:
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selectively generating short pulses of light; projecting said short pulses of light toward the backscattering medium and at an object enveloped by the medium; detecting said pulses of light reflected back from said object after a time delay corresponding to the round-trip propagation time of said light pulses to and from said object wherein glint detection means is used to detect the leading edge of light reflected back from said object; and converting said detected pulses of light to a video image of said object. - View Dependent Claims (32, 33)
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34. A method of detecting and imaging an object enveloped by a backscattering medium which is at least partially transmitting to light including the steps of:
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selectively generating short pulses of light; projecting said short pulses of light toward the backscattering medium and at an object enveloped by the medium; detecting said pulses of light reflected back from said object using at least one camera means after a time delay corresponding to the round-trip propagation time of said light pulses to and from said object; gating said camera means on one pulse after the leading edge of the reflected light is detected; converting said detected pulses of light to a video image of said object.
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35. A method of detecting and imaging from an airborne platform an object enveloped by water including the steps of:
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selectively generating short pulses of light from an airborne platform; projecting said short pulses of light toward the water and at an object enveloped by the water; detecting said pulses of light reflected back from said object after a time delay corresponding to the round-trip propagation time of said light pulses to and from said object; and converting said detected pulses of light to a video image of said object. - View Dependent Claims (37, 38)
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36. An apparatus for detecting and imaging an object enveloped by a backscattering medium which is at least partially transmitting to light comprising:
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generating means for selectively generating short pulses of light; projecting means for projecting said short pulses of light toward the backscattering medium and at an object enveloped by the medium; detecting means for detecting said pulses of light reflected back from said object after a time delay corresponding to the round-trip propagation time of said light pulses to and from said object; glint detection means for detecting the leading edge of light reflected back from said object; and converting means for converting said detected pulses of light to a video image of said object.
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39. An apparatus for detecting and imaging an object enveloped by a backscattering medium which is at least partially transmitting to light comprising:
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generating means for selectively generating short pulses of light; projecting means for projecting said short pulses of light toward the backscattering medium and at an object enveloped by the medium; at least one camera means for detecting said pulses of light reflected back from said object after a time delay corresponding to the round-trip propagation time of said light pulses to and from said object; gating means for gating said camera means on one pulse after the leading edge of the reflected light is detected; and converting means for converting said detected pulses of light to a video image of said object.
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40. An apparatus for detecting and imaging an object enveloped by water comprising:
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generating means for selectively generating short pulses of light; projecting means for projecting said short pulses of light toward the water and at an object enveloped by the water; detecting means for detecting said pulses of light reflected back from said object after a time delay corresponding to the round-trip propagation time of said light pulses to and from said object, said generating means, projecting means and detecting means all being positioned on an airborne platform; and converting means for converting said detected pulses of light to a video image of said object.
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Specification