Method and system for detection and synthetic aperture imaging of a target

A system for detection and synthetic aperture (SA) imaging of a target present in a scene from a platform in relative movement with respect to the scene along a travel path, the system comprising:

• a light source assembly for mounting on the platform and configured to generate a lidar search signal, an SA transmission signal, and a local oscillator (LO) signal;
• a transmitter-receiver assembly for mounting on the platform and configured to:
• in a target detection phase using lidar remote sensing, illuminate the scene with the lidar search signal along a search direction and with an angular field of illumination to search for the target in the scene, and receive a search return signal produced by reflection of the lidar search signal from the target to detect the presence of the target in the scene;
• and
• in an SA imaging phase using SA imaging and following the target detection phase, illuminate the scene with the SA transmission signal with an angular field of illumination narrower than the angular field of illumination of the lidar search signal used in the target detection phase, and receive an SA return signal produced by reflection of the SA transmission signal from the target;
• a detector assembly for mounting on the platform and configured to detect, in the target detection phase, the search return signal and detect, in the SA imaging phase, the SA return signal by mixing the SA return signal with the LO signal to generate SA signal data;
• and a control and processing unit operatively coupled to the light source assembly, the transmitter-receiver assembly, and the detector assembly, the control and processing unit being configured to:
• in the target detection phase, estimate, from the search return signal, a range and an angular location of the target;
• and
• in the SA imaging phase:
• control the light source assembly to generate the SA transmission signal and the LO signal with a time delay therebetween, the time delay being based on the range of the target estimated in the target detection phase using lidar remote sensing;
• control the transmitter-receiver assembly to illuminate the scene with the SA transmission signal along an imaging direction, the imaging direction being based on the angular location of the target estimated in the target detection phase using lidar remote sensing;
• receive the SA signal data from the detector assembly;
• and
• generate an SA image of the target from the SA signal data.

A non-transitory computer readable storage medium having stored thereon computer executable instructions for use with a system for detection and synthetic aperture (SA) imaging of a target present in a scene, the system being mounted on a platform in relative movement with respect to the scene and comprising a light source assembly, a transmitter-receiver assembly, and a detector assembly, wherein the computer executable instructions, when executed by a processor, cause the processor to:

• perform a target detection phase using lidar remote sensing, the target detection phase comprising steps of:
• controlling the light source assembly to generate a lidar search signal;
• controlling the transmitter-receiver assembly to illuminate the scene with the lidar search signal along a search direction and with an angular field of illumination to produce a search return signal by reflection of the lidar search signal from the target-to detect the presence of the target in the scene;
• and
• estimating, from the search return signal, a range and an angular location of the target;
• and
• perform, using SA imaging and following the target detection phase, an SA imaging phase, the SA imaging phase comprising steps of:
• controlling the light source assembly to generate an SA transmission signal and a local oscillator (LO) signal with a time delay therebetween, the time delay being based on the range of the target estimated in the target detection phase using lidar remote sensing;
• controlling the transmitter-receiver assembly to illuminate the scene with the SA transmission signal along an imaging direction and with an angular field of illumination narrower than the angular field of illumination of the lidar search signal used in the target detection phase to produce an SA return signal by reflection of the SA transmission signal from the target, the imaging direction being based on the angular location of the target estimated in the target detection phase using lidar remote sensing;
• receiving SA signal data from the detector assembly resulting from a mixing of the SA return signal received by the transmitter-receiver assembly with the LO signal;
• and generating an SA image of the target from the SA signal data.