Random pulse burst range-resolved doppler laser radar

• US 5,621,514 A
• Filed: 01/05/1995
• Issued: 04/15/1997
• Est. Priority Date: 01/05/1995
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Hughes Electronics Corporation (Rtx Corporation)
• Inventors: Minden, Monica L., Paranto, Joseph N., Liskow, Dean H. S.
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US08/369,023
• Time in Patent Office: 831 Days
• Field of Search: 356/5.09, 356/5.01, 356/28.5, 180/169
• US Class Current: 356/5.09
• CPC Class Codes: B60T 7/22 initiated by contact of vehicle, e.g. bumper, with an external object, e.g. another vehicle , or by means of contactless obstacle detectors mounted on the vehicle
• CPC Class Codes: G01P 3/36 Devices characterised by the use of optical means, e.g. using infrared, visible, or ultraviolet light G01P3/68 takes precedence; gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams G01C19/64
• CPC Class Codes: G01S 17/58 Velocity or trajectory determination systems; Sense-of-movement determination systems
• CPC Class Codes: G01S 17/931 of land vehicles
• CPC Class Codes: G01S 7/483 Details of pulse systems

Abstract

An laser radar system employing transmitted random and pseudo random optical pulse trains and signal processing that provides unambiguous range and Doppler velocity data. The system comprises a diode-pumped fiber laser local oscillator and an optical random pulse signal generator comprising a mode-locked fiber laser source for generating and transmitted randomly spaced optical pulses. A heterodyne output pulse monitor processes the local oscillator signals and samples the transmitted optical pulses. A heterodyne receiver detector processes the local oscillator signals and received optical pulses reflected from a target. An acoustic charge transport delay line provides a selectable signal delay for the signal provided by the heterodyne optical pulse monitor, and a mixer mixes signals provided by the heterodyne receiver detector and delay line and provides correlation output signals. A Doppler analyzer processes the correlation output signals from the mixer to provide frequency spectrum for each range bin, and an executive processor processes the frequency spectra from the Doppler analyzer to provide a range-resolved Doppler image on the display. The range-resolved Doppler output signals provided by the executive processor allow identification of a wideband weather signature and a narrow band target signature that are displayed on the display. The system employs a single waveform to provide the needed measurements, and eliminates trade-offs between range and velocity ambiguities. The present invention may be employed in vehicular collision avoidance radars and laser sensors, and in adaptive cruise control, robotic vision, and metrology-gauging applications.

Claims

1. A range resolved Doppler ladar system comprising:

a laser local oscillator for providing local oscillator signals;

an optical random pulse signal generator for generating and transmitting randomly spaced waveforms;

a heterodyne output pulse monitor coupled to the local oscillator and signal generator for sampling the transmitted waveforms;

a heterodyne receiver detector coupled to the local oscillator and reflected waveforms received from a target;

a selectable delay line coupled to the heterodyne output pulse monitor for providing a selectable signal delay;

a mixer coupled to the heterodyne receiver detector and to the selectable delay line for mixing signals received therefrom and for providing correlation output signals therefrom;

a Doppler analyzer coupled to the mixer output for processing the correlation signals to provide a frequency spectrum;

a display; and

an executive processor coupled to the Doppler analyzer and to the display for processing the frequency spectra received therefrom to form a range-resolved Doppler image, and for displaying the range-resolved Doppler image on the display.

2. The system of claim 1 wherein the laser local oscillator comprises a diode-pumped fiber laser local oscillator.

3. The system of claim 1 wherein the optical random pulse signal generator comprises a mode-locked fiber laser source.

4. The system of claim 1 wherein the delay line further comprises an acoustic charge transport device.

5. The system of claim 1 which further comprises:

an optical system coupled to the optical random pulse signal generator and to the heterodyne receiver detector for transmitting the optical pulses and for receiving the reflected optical pulses from the target.

6. The system of claim 1 wherein the frequency spectrum for each range bin provided by the executive processor corresponds to a weather signature and a narrow target signature that are displayed on the display.

7. A random-pulse-burst range-resolved Doppler ladar system for displaying a range-resolved Doppler image on a display, said system comprising:

a diode-pumped fiber laser local oscillator for providing local oscillator signals;

an optical random pulse signal generator comprising a mode-locked fiber laser source for generating and transmitting randomly spaced waveforms;

a heterodyne output pulse monitor coupled to the local oscillator and signal generator for sampling the transmitted waveforms;

a heterodyne receiver detector coupled to the local oscillator and reflected waveforms received from a target and for sampling the return waveform;

an acoustic charge transport delay line coupled to the heterodyne optical pulse monitor for providing a selectable signal delay;

a mixer coupled to the heterodyne receiver detector and to the acoustic charge transport delay line for mixing signals received therefrom and for providing correlation output signals therefrom;

a Doppler analyzer coupled to the mixer for processing the correlation output signals to provide frequency spectra; and

an executive processor coupled to the Doppler analyzer and to the display for processing the frequency spectra to form a range-resolved Doppler image, and for displaying the range-resolved Doppler image on the display.

8. The system of claim 7 which further comprises:

an optical system coupled to the optical random pulse signal generator and to the heterodyne receiver detector for transmitting the outgoing pulses and for receiving the reflected waveforms from the target.

9. The system of claim 7 wherein the frequency position signals for each range bin provided by the executive processor correspond to a wideband weather signature and a narrow band target signature that are displayed on the display.