William L Ruff

US Patent:

58778519, Mar 2, 1999

Filed:

Sep 24, 1997

Appl. No.:

8/937150

Inventors:

Barry Stann - Silver Spring MD
William C. Ruff - Baltimore MD
Zoltan G. Sztankay - Rockville MD

Assignee:

The United States of America as represented by the Secretary of the Army - Washington DC

International Classification:

G01C 308
H04N 718

US Classification:

356 509

Abstract:

A laser transmitter is amplitude modulated with a chirp signal to illumin an entire scene or field of view. A mixing process occurs in the received light path using an electro-optic light modulator positioned just in front of the focal plane detector array. The detector array detects and integrates the mixed light signal over some field of view. Numerous image frames are recorded periodically in the time over the FM period. The Fourier transform taken over time for a pixel establishes the range to the target in that pixel. Performing the Fourier transform for all pixels yields a three-dimensional image of objects in the field of view. Such an arrangement yields a scannerless ladar possessing high range resolution with no range ambiguities.

US Patent:

56085141, Mar 4, 1997

Filed:

Apr 19, 1995

Appl. No.:

8/424949

Inventors:

Barry L. Stann - Silver Spring MD
William C. Ruff - Baltimore MD
Zoltan G. Sztankay - Rockville MD

Assignee:

The United States of America as represented by the Secretary of the Army - Washington DC

International Classification:

G01C 308
G01S 1308

US Classification:

356 509

Abstract:

In a high range resolution ladar, a chirp signal waveform is propagated as a divergent laser light waveform and the target reflected return is collected and converted to a current proportional to power. An undelayed chirp signal is added in a mixer to the return current and then low pass filtered to recover a mixed intermediate frequency (IF) signal having a frequency proportional to the target range. Periodically, the light circuit is interrupted and the chirp signal is processed through the mixer and low pass filter without a target return current and this output, the mixer self-clutter, is stored. This stored self-clutter signal is subsequently subtracted from the mixed IF signal on a chirp by chirp basis to cancel the self-clutter produced by the mixer. The subtracted signal is then frequency analyzed to determine target range.