Directed registration of three-dimensional scan measurements using a sensor unit

Abstract

A laser scanner measures 3D coordinates from a first position and a second position and uses a sensor unit that includes at least an accelerometer and gyroscope to register the 3D coordinates, the registration based at least in part on comparison to a measured sensor displacement to a preferred displacement value.

What is claimed is: 
     
         1 . A laser scanner for optically scanning and measuring an object in an environment comprising:
 a measuring head configured to move from a first position to a second position by incremental steps;   a light emitter disposed within the measuring head,   a light receiver disposed within the measuring head,   a first angle measuring device disposed within the measuring head,   a second angle measuring device operably coupled to the measuring head,   a sensor unit disposed within the measuring head, the sensor unit including at least an accelerometer and a gyroscope; and   a control and evaluation unit disposed within the measuring head and operably coupled to the light emitter, the light receiver, the first angle measuring device, the second angle measuring device and the sensor unit, the control and evaluation unit being responsive to executable computer instructions when executed on a processor, the computer readable instructions comprising:   for each of a plurality of first object points:
 measuring a first angle with the first angle measuring device; 
 measuring a second angle with the second angle measuring device; 
 emitting with the light emitter an emission light beam; 
 reflecting the emission light beam from the object to produce a reception light beam; 
 receiving with the light receiver the reception light beam and obtaining a first electrical signal in response; 
 determining a distance based at least in part on the first electrical signal and on a speed of light in air; 
 determining a first three-dimensional (3D) coordinates of the first object points in a first instrument frame of reference, the 3D coordinates based at least in part on each of the first angle, the second angle, and the distance to the plurality of object points on the object; 
 determining a displacement value and a displacement tolerance; 
 recording an initial reading from the sensor unit; 
   for each incremental step:
 recording a current reading of the sensor unit; 
 determining a measured sensor displacement based at least in part on the current reading of the sensor unit and the initial reading of the sensor unit; and 
 movement of the measurement head at the second position when the measured sensor displacement is within the displacement tolerance of the displacement value. 
   
     
     
         2 . The laser scanner of  claim 1  wherein the computer readable instructions further comprise for each of a plurality of second object points:
 measuring the first angle with the first angle measuring device; 
 measuring the second angle with the second angle measuring device; 
 emitting with the light emitter the emission light beam; 
 reflecting the emission light beam from the object to produce the reception light beam; 
 receiving with the light receiver the reception light beam and obtaining the first electrical signal in response; 
 determining the distance based at least in part on the first electrical signal and on a speed of light in air; 
 determining a second 3D coordinates of the object in a second instrument frame of reference, the 3D coordinates based at least in part on the first angles, the second angles, and the distances to the plurality of object points on the object; 
 registering the first 3D coordinates and the second 3D coordinates into a common set of 3D coordinates in a common frame of reference based at least in part on the first 3D coordinates, the second 3D coordinates, and the measured sensor displacement; and 
 storing the common set of 3D coordinates. 
 
     
     
         3 . The laser scanner of  claim 1 , wherein the sensor unit further includes a magnetometer. 
     
     
         4 . The laser scanner of  claim 1 , wherein the sensor unit further includes a pressure sensor. 
     
     
         5 . The laser scanner of  claim 1 , the sensor unit further includes a GPS unit. 
     
     
         6 . The laser scanner of  claim 1 , wherein the accelerometer is a three-axis accelerometer. 
     
     
         7 . The laser scanner of  claim 1 , wherein the gyroscope is a three-axis gyroscope. 
     
     
         8 . The laser scanner of  claim 1 , wherein the accelerometer is a microelectromechanical system (MEMS) device and the gyroscope is a MEMS device. 
     
     
         9 . The laser scanner of  claim 1 , wherein the object includes a plurality of targets. 
     
     
         10 . The laser scanner of  claim 9 , wherein the targets are selected from the group consisting of spheres and checkerboards. 
     
     
         11 . The laser scanner of  claim 9 , wherein the targets are natural features. 
     
     
         12 . The laser scanner of  claim 11 , wherein the natural features are selected from the group consisting of edges, planes, and corners. 
     
     
         13 . The laser scanner of  claim 1 , wherein the displacement value is based at least in part on an expected overlap of regions scanned by the laser scanner from the first position and the second position. 
     
     
         14 . The laser scanner of  claim 1 , further comprising a trolley operably coupled to the measuring head to move the measuring head from the first position to the second position. 
     
     
         15 . The laser scanner of  claim 14 , further comprising a base coupled between the measuring head and the trolley, the measuring head being rotationally coupled to the base. 
     
     
         16 . The laser scanner of  claim 1 , wherein the computer readable instructions further comprise determining an impact during the movement of the measurement head from the first position to the second position 
     
     
         17 . The laser scanner of  claim 16 , wherein the computer readable instructions further comprise re-determining the first three-dimensional (3D) coordinates of the first object points in a first instrument frame of reference in response to determining the impact. 
     
     
         18 . The laser scanner of  claim 16 , wherein the computer readable instructions further comprise determining changes in a direction of movement in response to determining the impact. 
     
     
         19 . The laser scanner of  claim 16 , wherein the computer readable instructions further comprise determining a correlation between a first set of the first three-dimensional (3D) coordinates of the first object points determined before the impact and second set of the first three-dimensional (3D) coordinates of the first points determined after the impact. 
     
     
         20 . The laser scanner of  claim 19 , wherein the correlation is determined by a one-dimensional search in the angle of rotation.