Ladar System with Dichroic Photodetector for Tracking the Targeting of a Scanning Ladar Transmitter
Disclosed herein are various embodiment of an adaptive ladar receiver and associated method whereby the active pixels in a photodetector array used for reception of ladar pulse returns can be adaptively controlled based at least in part on where the ladar pulses were targeted. Additional embodiments disclose improved imaging optics for use by the receiver and further adaptive control techniques for selecting which pixels of the photodetector array are used for sensing incident light.
1 . A ladar transmitter apparatus comprising:
a first light source configured to generate a plurality of ladar pulses for transmission to a plurality of range points in a field of view;
a second light source configured to generate a reference light at a different frequency than the ladar pulses;
a plurality of mirrors that are scanable to a plurality of scan positions to define a targeting for the ladar transmitter apparatus in the field of view, wherein the scanable mirrors are configured to receive and direct the generated ladar pulses and the generated reference light toward a plurality of targeted range points in the scan area; and
a dichroic photodetector that is optically downstream from the scanable mirrors, the dichroic photodetector configured to (1) pass the ladar pulses toward the range points, and (2) absorb and convert the reference light into a reference signal indicative of where the scanable mirrors are targeted when the ladar pulses are transmitted.
2 . The apparatus of claim 1 wherein the dichroic photodetector is housed in a casing, wherein at least a region of the casing is optically transmissive such that the ladar pulses pass through the optically transmissive casing region toward the range points.
3 . The apparatus of claim 1 wherein the ladar pulses and the reference light are aligned within an optical path from the mirrors to the dichroic photodetector.
4 . A method comprising:
transmitting a ladar pulse toward a targeted range point in a field of view via a plurality of scanning mirrors;
transmitting a reference light via the scanning mirrors when the ladar pulse is transmitted, wherein the reference light exhibit a different frequency than the ladar pulse;
a photodetector that is optically downstream from the scanning mirrors receiving the transmitted ladar pulse and the transmitted reference light;
the photodetector passing the received ladar pulse toward the targeted range point;
the photodetector absorbing the received reference light and converting the absorbed reference light into a tracking signal indicative of where the scanning mirrors was targeted when the ladar pulse was transmitted; and
repeating the transmitting steps, the receiving step, the passing step, and the absorbing and converting steps for a plurality of different targeted range points in the field of view.
5 . The method of claim 4 wherein the photodetector is housed in a casing, wherein at least a region of the casing is optically transmissive, the method further comprising the optically transmissive casing region (1) passing the transmitted ladar pulse and the transmitted reference light onto the photodetector, and (2) passing the received ladar pulse toward the targeted range point.
6 . The method of claim 4 further comprising:
aligning the ladar pulses and the reference light within an optical path from the scanning mirrors to the photodetector.
7 . The method of claim 4 wherein the transmitting and repeating step comprise transmitting the ladar pulses toward the targeted range points via compressive sensing.