Ladar Transmission with Dynamic Scan Pattern Control

Abstract

Various embodiments are disclosed for improved scanning ladar transmission, including but not limited to an example embodiment where feedback control is used to finely control mirror scan positions.

What is claimed is: 
     
         1 . A system for dynamic ladar scan control, the system comprising:
 a beam scanner comprising a first mirror and a second mirror;   a beam scanner controller; and   a feedback system;   wherein the first mirror is scanable to a plurality of first mirror scan angles in response to a first control signal to define where the beam scanner is targeted along a first axis in a field of view;   wherein the second mirror is scanable to a plurality of second mirror scan angles in response to a second control signal to define where the beam scanner is targeted along a second axis in the field of view, wherein the combination of the first and second mirror scan angles defines a plurality of targetable range points in the field of view for the beam scanner;   wherein the beam scanner controller drives scanning of the first and second mirrors by generating the first and second control signals, and wherein the beam scanner controller dynamically generates the second control signal based on shot list data that identifies a plurality of range points within the field of view for targeting with ladar pulse shots to be transmitted into the field of view via reflections from the first and second mirrors so that (1) the dynamically generated second control signal varies as a function of the identified range points from the shot list data to drive the scanning of the second mirror in a point-to-point mode and (2) the beam scanner dynamically targets the identified range points on a shot-by-shot basis; and   wherein the feedback system tracks the first and/or second mirror scan angles and produces an adjustment signal based on the tracked first and/or second mirror scan angles, the adjustment signal for adjusting the first and/or second control signal to controllably fine tune where the beam scanner is targeted.   
     
     
         2 . The system of  claim 1  further comprising:
 a processor that selects range points for targeting with ladar pulse shots based on an analysis of scene data that represents the field of view, wherein the shot list data comprises data that represents the selected range points. 
 
     
     
         3 . The system of  claim 2  wherein the processor translates a list of the selected range points into a shot list that comprises an ordered list of the selected range points for targeting with the ladar pulse shots, wherein the shot list defines the shot list data. 
     
     
         4 . The system of  claim 3  wherein the second control signal drives the scanning of the second mirror to exhibit a scan pattern that varies as a function of the ordered range points from the shot list. 
     
     
         5 . The system of  claim 3  wherein the shot list controls both the scanning of the second mirror and a timing for firing commands provided to a laser source so that the ladar pulse shots target the selected range points. 
     
     
         6 . The system of  claim 3  wherein the processor translates the list of the selected range points into the shot list by re-ordering a plurality of the selected range points into a sequence for the shot list based on a plurality of rules that define operational constraints with respect to (1) timings for the scanning of the first and second mirrors and (2) time needed between successive ladar pulse shots. 
     
     
         7 . The system of  claim 2  wherein the scene data comprises a frame that represents the field of view, and wherein the processor selects the range points for targeting with ladar pulse shots based on the analysis of the scene data so that the shot list data defines a higher concentration of selected range points for targeting with ladar pulse shots in a first portion of the frame than in a second portion of the frame. 
     
     
         8 . The system of  claim 7  wherein the processor performs corner detection on the scene data to identify a corner feature exhibited within the scene data, and wherein the first frame portion includes the identified corner feature. 
     
     
         9 . The system of  claim 7  wherein the processor performs edge detection on the scene data to identify an edge feature exhibited within the scene data, and wherein the first frame portion includes the identified edge feature. 
     
     
         10 . The system of  claim 7  wherein the processor performs contrast analysis on the scene data to identify a high contrast area exhibited within the scene data, and wherein the first frame portion includes the identified high contrast area. 
     
     
         11 . The system of  claim 6  wherein the high contrast area corresponds to a road boundary area. 
     
     
         12 . The system of  claim 6  wherein the high contrast area corresponds to a horizon area. 
     
     
         13 . The system of  claim 2  wherein the processor applies a range point down selection algorithm to the scene data to select a subset of the targetable range points for targeting with ladar pulse shots. 
     
     
         14 . The system of  claim 2  wherein the processor is part of the beam scanner controller. 
     
     
         15 . The system of  claim 2  further comprising:
 a camera that generates a frame image, and wherein the scene data comprises the frame image. 
 
     
     
         16 . The system of  claim 2  further comprising:
 a laser source that generates the ladar pulse shots for transmission into the field of view via the first and second mirrors. 
 
     
     
         17 . The system of  claim 16  wherein the beam scanner controller provides firing commands to the laser source based on the shot list data so that the generated ladar pulses are transmitted toward the targeted range points as ladar pulse shots via the first and second mirrors. 
     
     
         18 . The system of  claim 1  wherein the first and second mirrors comprise MEMS mirrors. 
     
     
         19 . The system of  claim 1  wherein the controller uses a clock signal having a frequency in a range of 50-100 MHz as a source for the first control signal. 
     
     
         20 . The system of  claim 1  wherein the feedback system tracks the first and second mirror scan angles and produces first and second adjustment signals based on the tracked first and second mirror scan angles for adjusting the first and second control signals respectively to controllably fine tune where the beam scanner is targeted. 
     
     
         21 . The system of  claim 1  wherein the feedback system tracks the first mirror scan angles and produces the adjustment signal based on the tracked first mirror scan angles for adjusting the first control signal to controllably fine tune where the beam scanner is targeted. 
     
     
         22 . The system of  claim 1  wherein the feedback system tracks the second mirror scan angles and produces the adjustment signal based on the tracked second mirror scan angles for adjusting the second control signal to controllably fine tune where the beam scanner is targeted. 
     
     
         23 . The system of  claim 1  wherein the second mirror is optically downstream from the first mirror, wherein the first mirror is optically downstream from a laser source, wherein the first mirror serves as a fast axis mirror, and wherein the second mirror serves as a slow axis mirror. 
     
     
         24 . The system of  claim 1  wherein the second control signal defines a dynamic scan pattern for the beam scanner that includes interline skips. 
     
     
         25 . The system of  claim 1  wherein the second control signal defines a dynamic scan pattern for the beam scanner that includes interline detours. 
     
     
         26 . The system of  claim 1  wherein the first control signal comprises a sinusoidal signal that drives the first mirror in a resonant mode. 
     
     
         27 . The system of  claim 1  wherein the feedback system comprises a closed loop feedback system. 
     
     
         28 . The system of  claim 27  wherein the closed loop feedback system comprises a closed loop optical feedback system. 
     
     
         29 . The system of  claim 1  wherein the beam scanner controller comprises a field programmable gate array (FPGA). 
     
     
         30 . The system of  claim 1  wherein the first axis is orthogonal to the second axis. 
     
     
         31 . A ladar transmitter comprising:
 a first mirror that is scanable to a plurality of first mirror scan angles in response to a first control signal to define where the ladar transmitter is targeted along a first axis in a field of view;   a second mirror that is scanable to a plurality of second mirror scan angles in response to a second control signal to define where the ladar transmitter is targeted along a second axis in the field of view, wherein the combination of the first and second mirror scan angles defines a plurality of targetable range points in the field of view for the ladar transmitter;   a processor that (1) analyzes scene data representative of the field of view including contrast analysis of the scene data, (2) identifies an area of high contrast in the field of view based on the contrast analysis, and (3) generates a shot list based on the analyzed scene data, wherein the shot list identifies a subset of the targetable range points for targeting with ladar pulse shots, and wherein the identified range points are spatially distributed across the field of view in a manner that exhibits a relatively higher concentration of identified range points in the identified high contrast area than in another area of the field of view; and   a controller that drives scanning of the first and second mirrors by generating the first and second control signals, and wherein the controller dynamically generates the second control signal based on the shot list so that (1) the dynamically generated second control signal varies as a function of the identified range points from the shot list to drive the scanning of the second mirror in a point-to-point mode and (2) the ladar transmitter dynamically targets the identified range points with ladar pulse shots on a shot-by-shot basis.   
     
     
         32 . The ladar transmitter of  claim 31  wherein the contrast analysis comprises edge detection. 
     
     
         33 . The ladar transmitter of  claim 31  wherein the contrast analysis comprises corner detection. 
     
     
         34 . The ladar transmitter of  claim 31  wherein the high contrast area corresponds to a road boundary area. 
     
     
         35 . The ladar transmitter of  claim 31  wherein the high contrast area corresponds to a horizon area. 
     
     
         36 . The ladar transmitter of  claim 31  further comprising:
 a laser source that generates the ladar pulse shots for transmission into the field of view via the first and second mirrors; and 
 wherein the controller generates firing commands for the laser source based on the shot list. 
 
     
     
         37 . The ladar transmitter of  claim 36  wherein the processor (1) generates a list of the identified range points based on the analyzed scene data and (2) translates the list of identified range points into the shot list by defining an order for targeting the identified range points with ladar pulse shots based on a plurality of rules that reflect operational constraints with respect to (i) timings for the scanning of the first and second mirrors and (ii) time needed between successive ladar pulse shots. 
     
     
         38 . The ladar transmitter of  claim 36  wherein the first mirror is optically downstream from the laser source, and wherein the second mirror is optically downstream from the first mirror. 
     
     
         39 . The ladar transmitter of  claim 38  wherein the first control signal comprises a sinusoidal signal that drives the first mirror in a resonant mode. 
     
     
         40 . The ladar transmitter of  claim 31  wherein the processor comprises a field programmable gate array (FPGA). 
     
     
         41 . The ladar transmitter of  claim 31  wherein the controller comprises a beam scanner controller and a system controller. 
     
     
         42 . The ladar transmitter of  claim 41  wherein the processor is part of the system controller. 
     
     
         43 . A ladar transmitter comprising:
 a first mirror that is scanable to a plurality of first mirror scan angles in response to a first control signal to define where the ladar transmitter is targeted along a first axis in a field of view;   a second mirror that is scanable to a plurality of second mirror scan angles in response to a second control signal to define where the ladar transmitter is targeted along a second axis in the field of view, wherein the combination of the first and second mirror scan angles defines a plurality of targetable range points in the field of view for the ladar transmitter;   a processor that (1) analyzes scene data representative of the field of view, (2) identifies a subset of the targetable range points based on the analyzed scene data, the identified subset serving as a list of range points for targeting with ladar pulse shots, and (3) translates the list of range points into a shot list that re-orders the range points of the identified subset into a sequence of ladar pulse shots based on a plurality of operational constraints, wherein the operational constraints include a limit regarding how much time a laser source needs between ladar pulse shots; and   a controller that drives scanning of the first and second mirrors by generating the first and second control signals, and wherein the controller dynamically generates the second control signal based on the shot list so that (1) the dynamically generated second control signal varies as a function of the range points corresponding to the sequence to drive the scanning of the second mirror in a point-to-point mode and (2) the ladar transmitter dynamically targets the range points of the identified subset with ladar pulse shots on a shot-by-shot basis in accordance with the sequence.   
     
     
         44 . The ladar transmitter of  claim 43  further comprising:
 a laser source that generates the ladar pulse shots for transmission into the field of view via the first and second mirrors; and 
 wherein the controller generates firing commands for the laser source based on the shot list and in coordination with the first and second control signals so that the ladar transmitter transmits the ladar pulse shots toward the range points of the identified subset in accordance with the sequence. 
 
     
     
         45 . The ladar transmitter of  claim 44  wherein the laser source includes a fiber laser. 
     
     
         46 . The ladar transmitter of  claim 43  wherein the first mirror is optically downstream from the laser source, and wherein the second mirror is optically downstream from the first mirror. 
     
     
         47 . The ladar transmitter of  claim 43  wherein the first control signal comprises a sinusoidal signal that drives the first mirror in a resonant mode. 
     
     
         48 . The ladar transmitter of  claim 43  wherein the controller comprises a beam scanner controller and a system controller. 
     
     
         49 . The ladar transmitter of  claim 48  wherein the processor is part of the system controller. 
     
     
         50 . The ladar transmitter of  claim 43  wherein the second control signal defines a dynamic scan pattern for the beam scanner that includes interline skips. 
     
     
         51 . The ladar transmitter of  claim 43  wherein the second control signal defines a dynamic scan pattern for the beam scanner that includes interline detours.