초록 ▼

A synthetic aperture ladar system using a mode locked laser transmitter. The inventive system (12) includes a mode locked laser transmitter (22), a receiver (40) adapted to detect signals transmitted by said laser (22) and reflected by an object (32) and a signal processor (50) for analyzing the sig

A synthetic aperture ladar system using a mode locked laser transmitter. The inventive system (12) includes a mode locked laser transmitter (22), a receiver (40) adapted to detect signals transmitted by said laser (22) and reflected by an object (32) and a signal processor (50) for analyzing the signals. The laser (22) is particularly novel as a synthetic aperture ladar transmitter inasmuch as it includes a mode locking mechanism (180). The mode locking mechanism (180) causes the laser to output energy at all modes within the gain profile in phase with one another. The result is a series of coherent pulses which may be used for synthetic aperture ladar applications. In a particular embodiment, the present teachings are implemented in a multifunctional laser which, in its operational mode, outputs a mode locked beam for synthetic aperture ladar. In the illustrative embodiment, the laser is an erbium or erbium, ytterbium-doped, fiber pumped laser and the mode locking mechanism is a passive quantum well absorber crystal or an active acoustic crystal mounted in the laser cavity. In any event, the return signals are received and processed to extract range and cross-range imaging information. To this end, the signal processor (50) includes a range de-multiplexer (206) for organizing the return signals into range bins. For each range bin, the signal processor (50) applies a Fast Fourier Transform (210) and centroid detection algorithm (212) to extract a signal representing Doppler frequencies for each range bin. In addition, the signal processor (50) may also extract a signal representing intensity for each range bin.

대표청구항 ▼

1. A synthetic aperture ladar system comprising:a mode locked laser transmitter; a receiver adapted to detect signals transmitted by the laser and reflected by an object; means for moving the laser transmitter and receiver, wherein the direction of motion forms a large angle with the direction of th

1. A synthetic aperture ladar system comprising:a mode locked laser transmitter; a receiver adapted to detect signals transmitted by the laser and reflected by an object; means for moving the laser transmitter and receiver, wherein the direction of motion forms a large angle with the direction of the transmitted laser beam; and means for processing the detected signals to increase cross-range resolution. 2. The invention of claim 1 wherein the laser transmitter includes a laser and means for mode locking the output thereof.3. The invention of claim 2 wherein the laser is an erbium-doped crystal laser.4. The invention of claim 3 wherein the laser is an erbium, ytterbium-doped laser.5. The invention of claim 3 further including means for pumping the laser via an optical fiber.6. The invention of claim 2 wherein the means for mode locking includes a quantum well absorber.7. The invention of claim 2 wherein the means for mode locking includes an acoustic crystal.8. The invention of claim 1 wherein the means for processing includes a range de-multiplexer for organizing the signals into range bins.9. The invention of claim 8 wherein the means for processing further includes means for extracting a signal representing Doppler frequencies detected for each range bin.10. The invention of claim 9 wherein said means for extracting Doppler frequencies includes means for computing a frequency spectrum associated with each range bin.11. The invention of claim 10 wherein said means for computing a frequency spectrum includes a Fast Fourier Transform.12. The invention of claim 10 wherein said means for extracting Doppler frequencies further includes means for detecting centroids of said frequency spectrums.13. The invention of claim 9 wherein the means for processing further includes means for extracting a signal representing intensity of the signal detected for each range bin.14. The invention of claim 1 further including a local oscillator for generating a reference beam.15. The invention of claim 14 wherein said receiver combines said reflected signal with said reference beam.