Beam steering LADAR sensor
View Patent ↗A beam steering capability is proposed for a ladar sensor operating with limited laser transmit power, as may be typical of an airborne or automotive application. The ladar system also makes use of optical gain elements in the receiver which act to increase the signal to noise ratio at the receiver when the laser transmit power available is restricted by power, size, and/or cost limitations. In one embodiment, the calibration of each pixel in the ladar sensor is provided for by an electrical amplifier array with a number of pixel amplifiers. Each pixel amplifier may be individually calibrated to a mating detector element so as to eliminate the variations in dark current and gain between all pixels in the detector array. A number of new detector array designs are described which may lower cost and improve performance, and new low cost and high performance packaging for the detector array, amplifier array, and readout integrated circuit is introduced.
1. A ladar system comprising:
a first ladar sensor and a second ladar sensor;
said first ladar sensor having;
a laser transmitter with a pulsed laser light output transmitting light at a first wavelength through a diffusing optic adapted to illuminate a reflecting surface in a first field of view of said first ladar sensor,
a beam steering mechanism having a reflective face, and adapted to steer the laser light output in at least one axis across said first field of view,
a time zero reference output connected to said second ladar sensor through a cable, said time zero reference output adapted to signal the beginning of the pulsed laser light output,
said second ladar sensor having;
a second field of view overlapping said first field of view,
a time zero reference input connected to said cable,
a time zero reference circuit connected to said time zero reference input, and said time zero reference circuit having a time zero reference electrical output,
receiving optics adapted to collect and condition the pulsed laser light reflected from said reflecting surface,
a two dimensional array of light sensitive detectors positioned at a focal plane of said receiving optics, and each of said light sensitive detectors intercepting a pixellated portion of said pulsed laser light output reflected from said surface, and each light sensitive detector having an output producing an electrical response signal,
a detector bias circuit connected to a voltage distribution grid of said array of light sensitive detectors,
a readout integrated circuit with a clock circuit and a plurality of unit cell electrical circuits, and
each of said unit cell electrical circuits having an input connected to said clock circuit and to said time zero reference electrical output, and having an amplifier with an input connected to one of said light sensitive detector outputs, and each amplifier having an output, and a pulse detection circuit connected to said amplifier output, and said pulse detection circuit having a termination output, a counter connected to the time zero reference electrical output and to said clock circuit, said counter started counting by the time zero reference electrical output, and said counter connected to, and stopped counting by the termination output, and the counter having an output proportional to the distance to said surface.
2. The ladar system of claim 1 wherein said second ladar sensor is mounted to a vehicle.
3. The ladar system of claim 1 wherein said second ladar sensor has a voltage sampling circuit connected to the output of each of said amplifiers.
4. The ladar system of claim 1 wherein said cable is a fiber optic cable.
5. The ladar system of claim 1 wherein said cable has at least one electrical conductor.
6. The ladar system of claim 1 wherein said laser transmitter comprises at least one semiconductor laser.
7. The ladar system of claim 1 wherein said laser transmitter is a solid state laser.
8. The ladar system of claim 1 wherein said second ladar sensor is integrated into an assembly selected from the set of; a headlight, a turn signal, taillight, parking light, and brake light.