Scanning device with point-to-point focusing
Method and opto-electronic measuring device for measuring of an object's surface with a measuring rate of at least one thousand object points per second. Using a high-speed autofocus optical module comprising at least one variable focal length lens or reconfigurable optical phase plate having a response time of under 1 ms, situated in an emitting beam path, there is a real-time focus adaption of the measurement beam within a single object point measurement period.
1. An opto-electronic measuring device for point cloud acquisition by scanning measuring of an object's surface with a measuring rate of at least one thousand object points per second comprising:
a base and a targeting unit defining a target axis for targeting the object to be measured, the targeting unit being rotatable in relation to the base,
a light source for generation of a measurement beam, an exit aperture for emitting the measurement beam as a free beam in direction of the target axis towards a point on the object's surface to be measured and with an internal emitting measurement beam path,
wherein a high-speed autofocus optical module, situated in the internal emitting measurement beam path, the high-speed autofocus optical module being designed for a real-time measurement focus adaption within a single object point measurement period and comprising at least one variable focal length lens or reconfigurable optical phase plate having a response time of under 10 μs.
2. The opto-electronic measuring device according to claim 1 , wherein the real-time focus adaption is an individual adaption of measurement beam focus for a respective object point.
3. The opto-electronic measuring device according to claim 2 , wherein the high-speed autofocus optical module comprises at least one collimation lens whereas the variable focal length lens or the reconfigurable optical phase plate is located between the collimation lens and the near field of the light source.
4. The opto-electronic measuring device according to claim 1 , wherein the high-speed autofocus optical module comprises at least one collimation lens whereas the variable focal length lens or the reconfigurable optical phase plate is located between the collimation lens and the near field of the light source.
5. The opto-electronic measuring device according to claim 1 , wherein the focal power range of the high-speed autofocus optical module is adapted to a predefined maximal measurement range of the device in such a way that by variation of the focal length said real-time focus adaption is enabled throughout the whole measurement range.
6. The opto-electronic measuring device according to claim 5 , wherein the whole measurement range includes the close range down to 1 m from the exit aperture of the device or the measurement range being between 1 m and 20 m or 1 m and 1000 m.
7. The opto-electronic measuring device according to claim 1 , wherein the variable focal length lens or the reconfigurable optical phase plate has a focal power range of at least from 0 m-1 up to 10 m-1 or from −6 m-1 up to 6 m-1 or −3 m-1 up to 10 m-1.
8. The opto-electronic measuring device according to claim 1 , wherein the diameter of the measurement beam at the exit aperture is at least 6 mm.
9. The opto-electronic measuring device according to claim 1 , wherein the ratio of the diameter of the measurement beam at the exit aperture to the diameter of the measurement beam at the aperture of the variable focal length lens or the reconfigurable optical phase plate is at least 2:1.
10. The opto-electronic measuring device according to claim 1 , wherein the diameter of the variable focal length lens or the reconfigurable optical phase plate is 6 mm; at most.
11. The opto-electronic measuring device according to claim 1 , wherein the variable focal length lens comprises a deformable body confined within two optical surfaces deformable by at least one piezo-electric element actuator mechanically coupled to the deformable body in order to change the lens' focal length by an axial symmetrical bending or deformation.
12. The opto-electronic measuring device according to claim 1 , wherein a receiver high-speed autofocus module designed for real-time focus adaption for received light to a receiving detector optics of the opto-electronic measuring device in operation synchronous to the high-speed autofocus optical module.
13. A method for three dimensional opto-electronic light based scanning of an object's surface, for a laser scanner or laser tracker, with measuring object points with a measurement rate of at least one thousand object points per second using a measurement beam emitted into free space in direction of a target axis towards an object point to be measured, wherein automatic real-time measurement focus adapting within a single object point measurement period, with a frequency of at least 100 kHz.
14. The method according to claim 13 , wherein the real-time focus adapting is based on a distance to a respective object point, the distance being measured with the measurement beam:
as a separate preceding probe measurement of a respective object point directly before the measuring of the object point or
within the measuring of a respective object point.
15. The method according to claim 14 , wherein the real-time focus adapting is based on a distance to a respective object point, the distance being determined:
as a predictive value based on previous distance or focus trend and/or
from a preknown digital surface model of the object.
16. A computer program product comprising program code, which is stored on a machine-readable medium, and having computer-executable instructions for performing, when run on an opto-electronic measuring device, the method according to claim 14 .
17. The method according to claim 13 , wherein the real-time focus adapting is based on a distance to a respective object point, the distance being determined:
as a predictive value based on previous distance or focus trend and/or
from a preknown digital surface model of the object.
18. The method according to claim 17 , wherein the object point is measured using a sequence of radiation pulses and the distance is determined using a number of first pulses of the sequence.
19. The method according to claim 17 , wherein measuring object points with at least two different foci of the measurement beam, wherein for each focus setting a distance to the object point is deduced.
20. The method according to claim 13 , wherein measuring object points with at least two different foci of the measurement beam, wherein for each focus setting a distance to the object point is deduced.
21. A computer program product comprising program code, which is stored on a machine-readable medium, and having computer-executable instructions for performing, when run on an opto-electronic measuring device, the method according to claim 20 .
22. A computer program product comprising program code, which is stored on a machine-readable medium, and having computer-executable instructions for performing, when run on an opto-electronic measuring device, the method according to claim 13 .
23. The opto-electronic measuring device according to claim 13 , wherein the receiver autofocus unit is controlled dependent on the object distance in such a way that only for object distances shorter than the radiometric limiting distance said real-time focusing adaption for received light is active.