LADAR sensor for landing, docking and approach
A system for landing or docking a mobile platform is enabled by a flash LADAR sensor having an adaptive controller with Automatic Gain Control (AGC). Range gating in the LADAR sensor penetrates through diffuse reflectors. The LADAR sensor adapted for landing/approach comprises a system controller, pulsed laser transmitter, transmit optics, receive optics, a focal plane array of detectors, a readout integrated circuit, camera support electronics and image processor, an image analysis and bias calculation processor, and a detector array bias control circuit. The system is capable of developing a complete 3-D scene from a single point of view.
1. A ladar sensor configured to mount on a vehicle comprising:
a pulsed laser transmitter defining an optical axis and configured to produce a pulsed laser light output beam in response to an initiation command;
a digital controller adapted to produce the initiation command and transmit the initiation command to said pulsed laser transmitter;
transmit optics adapted to illuminate a field of view of said ladar sensor;
receive optics sighted along the optical axis and adapted to collect and condition an optical signal consisting of pulsed laser light reflected from the field of view;
at least one optical detector disposed to intercept said collected and conditioned optical signal from said receive optics, said detector configured to convert said optical signal into an electrical signal and transmit the electrical signal through an electrical output;
a detector bias voltage control circuit adapted to supply a bias voltage to said detector;
at least one unit cell electrical circuit disposed on a readout integrated circuit, said unit cell electrical circuit having an input connected to an electrical output of said detector, said unit cell electrical circuit having an amplifier connected to amplify said electrical output signal, and said unit cell electrical circuit providing a pixel output;
at least one unit cell timing circuit, and said unit cell timing circuit connected to a unit cell pixel output, and said unit cell timing circuit initiated by a master start signal derived from the transmitted laser pulse, and said unit cell timing circuit having an output indicating the time of flight of said laser pulse;
a readout circuit adapted to read out the output of said unit cell electrical circuit and unit cell timing circuit; and
a mirror adapted to steer said laser light output beam in azimuth angle and in elevation angle.
2. The ladar sensor of claim 1 wherein said mirror is configured to steer said laser light output beam by angular deflection in azimuth angle and elevation angle.
3. The ladar sensor of claim 1 wherein a range gate signal selects optical return signals received after a range gate start time and for a period of time therefrom.
4. The ladar sensor of claim 1 wherein said detector is an avalanche photodiode.
5. The ladar sensor of claim 1 wherein said detector array is a PIN photodiode.
6. The ladar sensor of claim 1 wherein said digital controller analyzes earlier readout circuit outputs to produce a new control output.
7. The ladar sensor of claim 1 wherein said amplifier has a variable gain and a variable gain control input, and said digital controller control output is connected thereto, and is adapted to produce a variable gain in said amplifier.
8. The ladar sensor mounted on a vehicle of claim 1 wherein said vehicle is a surface vehicle.