Angle calibration in light detection and ranging system

Abstract

Techniques, systems, and devices relating to conducting calibration of LIDAR systems are disclosed. In one exemplary aspect, a light detection and ranging (LIDAR) device is disclosed. The device comprises a light beam emitter operable to emit a light beam; a prism set positioned in an optical path of the light beam to refract the light beam onto a surface of a surrounding object; a light detector to detect light reflected by the surface of the surrounding object; a controller configured to estimate the surface of the surrounding object based on the detected light. The controller is operable to (1) determine a relative bias in the prism set, and (2) cause, based on the relative bias in the prism set, a compensation for an estimation error in the controller's estimation of the surface of the surrounding object.

1 - 48 . (canceled) 
     
     
         49 . A light detection and ranging (LIDAR) device, comprising:
 a light beam emitter operable to emit a light beam;   a prism set positioned in an optical path of the light beam to refract the light beam onto a surface of a surrounding object;   a motor coupled to one or more prisms in the prism set, operable to rotate at a rotational speed and cause said one or more prisms in the prism set to rotate;   an encoding device coupled to the motor, operable to generate a pulse signal in response to angular movement of the motor during a plurality of time intervals; and   a controller in communication with the encoding device, operable to (1) determine a rotational speed of the motor based on the pulse signal, (2) determine an angular position of the motor based on the rotational speed, and (3) determine, using the angular position of the motor, an angular position of the prism set to facilitate an estimation of the surface of the surrounding object.   
     
     
         50 . The device of  claim 49 , wherein the encoding device is a conductive rotary encoder. 
     
     
         51 . The device of  claim 49 , wherein the encoding device is an optical rotary encoder. 
     
     
         52 . The device of  claim 51 , wherein the optical rotary encoder comprises:
 a circular plate including a plurality of holes distributed unevenly along a perimeter of the circular plate, and   two identical optical sensors positioned side by side at a periphery location of the circular plate.   
     
     
         53 . The device of  claim 49 , wherein the controller determines the rotational speed of the motor by evaluating an average amount of angular movement of the motor during the plurality of time intervals. 
     
     
         54 . The device of  claim 49 , wherein the controller determines the rotational speed of the motor by evaluating a weighted amount of angular movement of the motor, wherein an angular movement in each of the plurality of time intervals is given a different weight that is inversely proportional to time. 
     
     
         55 . The device of  claim 49 , wherein the controller determines the rotational speed of the motor using a predetermined analytical model of the rotational speed of the motor. 
     
     
         56 . A calibration system for a light detection and ranging (LIDAR) device, comprising:
 a memory that stores instructions, and   a processor in communication with the memory and operable to execute the instructions to implement a method of calibrating a prism set of the LIDAR device, wherein the prism set directs an outgoing light beam onto a surface of a surrounding object, the method comprising:
 obtaining a pulse signal corresponding to an amount of angular movement of a motor during a plurality of time intervals, wherein the motor is coupled to one or more prisms in the prism set to cause said one or more prisms in the prism set to rotate, 
 determining a rotational speed of the motor based on the pulse signal and the amount of angular movement, 
 determining an angular position of the motor based on the rotational speed, 
 determining, using the angular position of the motor, an angular position of the prism set, and 
 computing a direction of the outgoing light beam based on the angular position of the prism set. 
   
     
     
         57 . The system of  claim 56 , wherein the determining of the rotational speed of the motor includes evaluating an average amount of angular movement of the motor during the plurality of time intervals. 
     
     
         58 . The system of  claim 56 , wherein the determining of the rotational speed of the motor includes evaluating a weighted amount of angular movement of the motor, wherein an angular movement in each of the plurality of time intervals is given a different weight that is inversely proportional to time. 
     
     
         59 . The system of  claim 56 , wherein the determining of the rotational speed of the motor includes using a predetermined analytical model of the rotational speed of the motor. 
     
     
         60 . The system of  claim 56 , wherein the pulse signal is obtained from an encoding device coupled to the motor. 
     
     
         61 . The system of  claim 60 , wherein the encoding device is a conductive rotary encoder. 
     
     
         62 . The system of  claim 60 , wherein the encoding device is an optical rotary encoder. 
     
     
         63 . A method of calibrating a light detection and ranging (LIDAR) device, comprising:
 obtaining a pulse signal corresponding to an angular movement of a motor during a plurality of time intervals, wherein the prism set directs an outgoing light beam onto a surface of a surrounding object and the motor is coupled to one or more prisms in the prism set to cause said one or more prisms in the prism set to rotate;   determining a rotational speed of the motor based on the pulse signal and the angular movement;   determining an angular position of the motor based on the rotational speed;   determining, using the angular position of the motor, an angular position of the prism set; and   computing a direction of the outgoing light beam based on the angular position of the prism set.   
     
     
         64 . The method of  claim 63 , wherein determining of the rotational speed of the motor includes evaluating an average amount of angular movement of the motor during the plurality of time intervals. 
     
     
         65 . The method of  claim 63 , wherein the determining of the rotational speed of the motor includes evaluating a weighted amount of angular movement of the motor, wherein an angular movement in each of the plurality of time intervals is given a different weight that is inversely proportional to time. 
     
     
         66 . The method of  claim 63 , wherein the determining of the rotational speed of the motor includes using a predetermined analytical model of the rotational speed of the motor. 
     
     
         67 . The method of  claim 63 , wherein the pulse signal is obtained from an encoding device coupled to the motor. 
     
     
         68 . The method of  claim 67 , wherein the encoding device is a conductive rotary encoder or an optical rotary encoder.