EP0422415A2
Expired / Lapsed
EP
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Imaging lidar method and apparatus
Assignee: Kaman Aerospace Corp
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Filing: 1990-09-18
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Granted: —
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Expires: 2010-09-18
Abstract
Abstract A novel timing control method is utilized in conjunction with an imaging lidar system of the type disclosed in U.S. Patent 4,862,257. This novel timing control is employed in applications wherein the lidar system is mounted on an airborne platform. The timing control method of this invention completely eliminates the glint detector with associated signal conditioner used in the system of U.S. Patent 4,862,257, and instead, relies upon a signal derived from the aircraft altimeter to continually provide platform altitude status. Since the entire system is under the control of a computer, the altimeter signal can be interpreted and used to adjust total delay so as to automatically track changing platform altitude. It is now possible to initiate all timing from the occurence of the laser "lamp fire" signal. The total delay to camera "gate on" is now the "lamp-to-laser" delay, plus round trip platform altitude delay (computed from the altimeter signal), plus desired water depth delay, less system delays.
Inventors
- 👤 Bobby Lee Ulich
- 👤 William P. Elkins
- 👤 Lonnie K. Calmes
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-01 16:53
CPC Classifications
G; G01; G01S; G01S17/00; G01S17/88; G01S17/89; G01S17/02; G01S17/06; G01S17/08; G01S17/10; G01S17/18
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
142 words
A method of detecting and imaging from an airborne platform an object enveloped by a backscattering medium which is at least partially transmitting to light, the airborne platform having altimeter means associated therewith, including the steps of: monitoring the altitude of the airborne platform in response to input from the altimeter means; selectively generating short pulses of light from the airborne platform; projecting said short pulses of light toward the backscattering medium and at an object enveloped by the backscattering medium; detecting said pulses of light reflected back from said object after a selected time delay corresponding to the round-trip propagation time of said light pulses to and from said object; calculating said selected time delay based on input data which includes the altitude of the airborne platform; and converting said detected pulses of light to a video image of said object.
Claim 2
Independent Claim
142 words
A method of detecting and imaging from an airborne platform an object enveloped by a backscattering medium which is at least partially transmitting to light, the airborne platform having altimeter means associated therewith, including the steps of: monitoring the altitude of the airborne platform in response to input from the altimeter means; selectively generating short pulses of light from the airborne platform; projecting said short pulses of light toward the backscattering medium and at an object enveloped by the backscattering medium; detecting said pulses of light reflected back from said object after a selected time delay corresponding to the round-trip propagation time of said light pulses to and from said object; calculating said selected time delay based on input data which includes the altitude of the airborne platform; and converting said detected pulses of light to a video image of said object.
Claim 3
Dependent Claim
33 words
A method as claimed in claim 1 wherein the backscattering medium comprises water and wherein: said time delay calculation is also dependent on the water depth between the water surface and said object.
Claim 4
Dependent Claim
38 words
A method as claimed in claim 2 wherein said video image is made at a selected detection depth and wherein: said detection depth is adjusted for each pulse under computer control to scan a preset range of depths.
Claim 5
Dependent Claim
40 words
A method as claimed in claim 2 wherein said light is generated by a lases wherein: the target depth variation visible in a single image generated from a single laser pulse is adjusted by a computer on a pulse-to-pulse basis.
Claim 6
Dependent Claim
104 words
A method as claimed in claim 1 wherein said light is generated by a laser, said light is detected by at least one camera and said selected time delay is dependent on a delay generator and wherein the backscattering medium comprises water and wherein said selected time delay is calculated by the following: (Delay 1 + Delay 2) - (Delay 3 + Delay 4) wherein: Delay 1 = round trip delay time for light propagation from the laser to the surface of the water; Delay 2 = water depth delay; Delay 3 = delay generator propagation delay; and Delay 4 = camera propagation delay.
Claim 7
Dependent Claim
43 words
A method as claimed in claim 5 wherein delay 1 is calculated by: Delay 1 = (2) (n air ) (A/c) where: n air = index of refraction of air; A = altitude reading from altimeter means; C = vacuum speed of light.
Claim 8
Dependent Claim
53 words
A method as claimed in claim 5 wherein delay 2 is calculated by Delay 2 = (2) (n water )(D/c) where: n air = index of refraction of the water; D = depth of water from upper edge of water to submerged volume to be imaged; and C = vacuum speed of light.
Claim 9
Independent Claim
141 words
An apparatus for detecting and imaging from an airborne platform an object enveloped by a backscattering medium which is at least partially transmitting to light comprising: monitoring means for monitoring the altitude of the airborne platform; generating means for selectively generating short pulses of light from the airborne platform; projecting means for projecting said short pulses of light toward the backscattering medium and at an object enveloped by the backscattering medium; detecting means for detecting said pulses of light reflected back from said object after a selected time delay corresponding to the round-trip propagation time of said light pulses to and from said object; calculating means for calculating said selected time delay based on input data which includes the altitude of the airborne platform; and converting means for converting said detected pulses of light to a video image of said object.
Claim 10
Independent Claim
141 words
An apparatus for detecting and imaging from an airborne platform an object enveloped by a backscattering medium which is at least partially transmitting to light comprising: monitoring means for monitoring the altitude of the airborne platform; generating means for selectively generating short pulses of light from the airborne platform; projecting means for projecting said short pulses of light toward the backscattering medium and at an object enveloped by the backscattering medium; detecting means for detecting said pulses of light reflected back from said object after a selected time delay corresponding to the round-trip propagation time of said light pulses to and from said object; calculating means for calculating said selected time delay based on input data which includes the altitude of the airborne platform; and converting means for converting said detected pulses of light to a video image of said object.
Claim 11
Dependent Claim
34 words
An apparatus as claimed in claim 8 wherein the backscattering medium comprises water and including: means for adjusting said detection depth for each pulse under computer control to scan a preset range of depths.
Claim 12
Dependent Claim
48 words
An apparatus as claimed in claim 8 wherein said light is generated by a laser and wherein the backscattering medium comprises water and wherein: the target depth variation visible in a single image generated from a single laser pulse is adjusted by a computer on a pulse-to-pulse basis.
References Cited (Backward Citations)
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