Efficient orientation of a lidar system in a vehicle

Abstract

A lidar system operates in a vehicle and includes a light source configured to emit light, a scanner configured to direct the emitted light so as to scan a field of regard of the lidar system in accordance with a scan pattern, and a receiver configured to detect the light scattered by one or more remote targets. The scanner includes a rotatable polygon mirror configured to scan the FOR along a horizontal dimension, a polygon mirror axis about which the polygon mirror rotates, and a y-scan mirror pivotable along an axis orthogonal to the polygon mirror axis and configured to scan the FOR along a vertical dimension. The polygon mirror has multiple reflective surfaces being angularly offset from one another. The polygon mirror axis is disposed on a plane substantially parallel to a plane along which the vehicle moves.

What is claimed is: 
     
         1 . A lidar system operating in a vehicle, the lidar system comprising:
 a light source configured to emit light;   a scanner configured to direct the emitted light to scan a field of regard (FOR) of the lidar system in accordance with a scan pattern, the scanner including:
 a rotatable polygon mirror configured to scan the FOR along a horizontal dimension, the polygon mirror having a plurality of reflective surfaces being angularly offset from one another, 
 a polygon mirror axis about which the polygon mirror rotates, the polygon mirror axis disposed on a plane substantially parallel to a plane along which the vehicle moves, 
 a y-scan mirror pivotable along an axis orthogonal to the polygon mirror axis and configured to scan the FOR along a vertical dimension; and 
   a receiver configured to detect the light scattered by one or more remote targets.   
     
     
         2 . The lidar system of  claim 1 , wherein the polygon mirror axis is in line with a current orientation of the vehicle. 
     
     
         3 . The lidar system of  claim 1 , wherein the polygon mirror axis is in line with a longitudinal axis of the vehicle. 
     
     
         4 . The lidar system of  claim 3 , wherein displacement of the polygon mirror when the vehicle accelerates or decelerates quickly is limited to only the longitudinal axis of the vehicle, to thereby reduce misalignment of scan lines in the horizontal dimension. 
     
     
         5 . The lidar system of  1 , wherein:
 the polygon mirror includes a block having a first wall and a second wall,   the plurality of reflective surfaces are angularly offset from one another along a periphery of the block, and   the axis about which the polygon mirror rotates corresponds to an axle extending into the block through at least one of the first and second walls.   
     
     
         6 . The lidar system of  claim 1 , wherein:
 the light source is configured to generate a first beam of light and a second beam of light directed at two different reflective surfaces of the rotatable polygon mirror,   the scanner scans the first beam of light and the second beam of light to define a first field of regard and a second field of regard, respectively, the first and second fields of regard in combination defining the field of regard of the lidar system, and   the first field of regard and a second field of regard include an overlap region aligned with a forward orientation of the vehicle.   
     
     
         7 . The lidar system of  claim 1 , wherein the lidar system is disposed on a roof of the vehicle. 
     
     
         8 . The lidar system of  claim 7 , further comprising:
 a housing enclosing at least the scanner and the receiver, wherein the housing is embedded in the roof so that a first portion of the housing projects above a surface of the roof and a second portion of the housing is below the surface of the roof inside the vehicle.   
     
     
         9 . The lidar system of  claim 1 , further comprising a controller configured to control motion of at least the y-scan mirror to modify the scan pattern. 
     
     
         10 . A method in a lidar system for scanning a field of regard, the method comprising:
 emitting light using a light source;   directing the emitted light to scan a field of regard (FOR) of the lidar system in accordance with a scan pattern, including:
 rotating a polygon mirror having a plurality of reflective surfaces about a polygon mirror axis to scan the FOR along a horizontal dimension, wherein the polygon mirror axis is disposed on a plane substantially parallel to plane along which the vehicle moves, and 
 pivoting a y-scan mirror along an axis orthogonal to the polygon mirror axis to scan the FOR along a vertical dimension; and 
   detecting the light scattered by one or more remote targets.   
     
     
         11 . The method of  claim 10 , wherein the polygon mirror axis is in line with at least one of (i) a current orientation of the vehicle and (ii) a longitudinal axis of the vehicle. 
     
     
         12 . The method of  claim 10 , wherein displacement of the polygon mirror when the vehicle accelerates or decelerates quickly is limited to only a longitudinal axis of the vehicle, to thereby reduce misalignment of scan lines in the horizontal dimension. 
     
     
         13 . The method of  claim 10 , wherein emitting the light includes generating a first beam of light and a second beam of light directed at two different reflective surfaces of the rotatable polygon mirror, the method further comprising:
 scanning the first beam of light and the second beam of light to define a first field of regard and a second field of regard, respectively, the first and second fields of regard in combination defining the field of regard of the lidar system, wherein the first field of regard and a second field of regard include an overlap region aligned with a forward orientation of the vehicle.   
     
     
         14 . The method of  claim 10 , further comprising:
 controlling motion of at least the y-scan mirror to modify the scan pattern.   
     
     
         15 . A vehicle comprising:
 a body having a longitudinal axis; and   a lidar system including a set of one or more sensor units, each sensor unit including:
 a light source configured to emit light, 
 a receiver configured to detect the light scattered by one or more remote targets, and 
 a scanner configured to direct the emitted light to scan a field of regard (FOR) of the lidar system in accordance with a scan pattern, the scanner including:
 a rotatable polygon mirror configured to scan the FOR along a horizontal dimension, the polygon mirror having a plurality of reflective surfaces being angularly offset from one another, and 
 a y-scan mirror pivotable along an axis orthogonal to the polygon mirror axis and configured to scan the FOR along a vertical dimension; 
 
   wherein the rotatable polygon mirror of at least one of the sensor units rotates about a polygon mirror axis disposed on a plane substantially parallel to a plane along which the vehicle moves.   
     
     
         16 . The vehicle of  claim 15 , wherein:
 the polygon mirror axis is in line with a longitudinal axis of the vehicle; and   displacement of the polygon mirror when the vehicle accelerates or decelerates quickly is limited to only the longitudinal axis of the vehicle, to thereby reduce misalignment of scan lines in the horizontal dimension.   
     
     
         17 . The vehicle of  claim 15 , wherein the lidar system includes two sensor units, with both polygon mirror axis disposed on the plane substantially parallel to the plane along which the vehicle moves and in line with a longitudinal axis of the vehicle, and wherein a first one of the sensor unit has a forward orientation with respect to a front of the vehicle, and a second one of the sensor unit has a backward orientation with respect to the front of the vehicle. 
     
     
         18 . The vehicle of  claim 15 , wherein:
 the light source is configured to generate a first beam of light and a second beam of light directed at two different reflective surfaces of the rotatable polygon mirror,   the scanner scans the first beam of light and the second beam of light to define a first field of regard and a second field of regard, respectively, the first and second fields of regard in combination defining the field of regard of the lidar system, and   the first field of regard and a second field of regard include an overlap region aligned with a forward orientation of the vehicle.   
     
     
         19 . The vehicle of  claim 15 , wherein the at least one of the sensor units is disposed on a roof of the vehicle. 
     
     
         20 . The vehicle of  claim 15 , the at least one sensor unit comprising:
 a housing enclosing at least the scanner and the receiver, wherein the housing is embedded in the roof so that a first portion of the housing projects above a surface of the roof and a second portion of the housing is below the surface of the roof inside the vehicle.