Scanning measuring device with fiber network
A laser scanner or laser profiler for scanning of an object surface by measuring of distances to surface points comprising a light pulse source, a transmission unit, a receiving unit for receiving measurement light reflected from the object surfaces and for determining the respective distance to a surface point based on the received measurement light according to the principle of time-of-flight and a fiber network with a fiber based optical coupler being designed for transforming a respective light pulse into a series of spaced sub-pulses of different energies. The sub-pulses are digitally sampled, at least one of the sub-pulses having an energy yielding an electrical signal amplitude in the non-saturated range of the receiving unit is selected, and a respective distance is determined based on deducing a time-of-flight of the at least one selected sub-pulse.
1 . A laser scanner or laser profiler for measuring of object surfaces, the laser scanner or laser profiler comprising:
a control and processing unit,
a light pulse source for generation of light pulses as measurement light,
a support structure,
a transmission unit for emitting a respective light pulse into free space towards the object surfaces with a beam deflection unit for varying an alignment of an emission direction of the measurement light, wherein the beam deflection unit is rotatable about at least one axis relative to the support structure,
at least one position meter for measuring the alignment of the at least one axis,
a receiving unit for receiving measurement light reflected from the object surfaces, and
a scanning functionality, wherein, when the scanning functionality is carried out in an automatically controlled manner by the control and processing unit, there is scanning with:
rotating the beam deflection unit about the at least one axis,
measuring the respective distance to surface points based on the received measurement light according to the principle of time-of-flight, and measuring the respective alignment of the at least one axis, and
generating a point cloud based on the measured distances and alignments, wherein:
the laser scanner or laser profiler includes a fiber network with a fiber based optical coupler,
the fiber network includes at least one fiber delay line,
the fiber network is integrated in an EDFA or YDFA doped-fiber amplifier, providing at least part of the fiber delay line,
the fiber network is designed for transforming a respective light pulse into a series of separated sub-pulses of different energies, whereby the control and processing unit is configured:
to digitally sample the sub-pulses,
to select at least one of the sub-pulses having an energy yielding an electrical signal amplitude in the non-saturated range of the receiving unit, and
to determine said respective distance based on deducing a time-of-flight of the at least one selected sub-pulse.
2 . The laser scanner or laser profiler according to claim 1 , wherein the first fiber based optical coupler and the fiber delay line form a loop for recursive splitting of the light pulse.
3 . The laser scanner or laser profiler according to claim 1 , wherein the fiber delay line comprises a fiber switch for temporary interruption of the fiber delay line.
4 . The laser scanner or laser profiler according to claim 3 , wherein the fiber switch is triggerable in response to a received sub-pulse.
5 . The laser scanner or laser profiler according to claim 1 , wherein the doped-fiber amplifier is a multi-stage amplifier and the fiber delay line is provided by a single mode fiber of its first amplifier stage.
6 . The laser scanner or laser profiler according to claim 1 , wherein the transmission unit comprises the first fiber based optical coupler and the first fiber network.
7 . The laser scanner or laser profiler according to claim 1 , wherein the receiving unit comprises
a second fiber based optical coupler and a second fiber network for splitting off a fraction of the energy of a respective received sub-pulse and
a variable optical attenuator or a switch in the receiving unit controllable in response to the pulse fraction.
8 . The laser scanner or laser profiler according to claim 1 , wherein the time interval between two subsequent sub-pulses is
equal for all sub-pulses of the series and/or
longer than the time length of the light pulse and/or
at least twice the inverse of an electronic bandwidth of the receiving unit and/or
such that the series of sub-pulses is shorter than the time between two successive surface point measurements.
9 . The laser scanner or laser profiler according to claim 1 , wherein the first fiber network comprises only single mode fiber devices.
10 . A scanning method for generation of a point cloud by measuring object surfaces with a laser scanner or laser profiler, the method comprising:
determining distances to surface points by:
using light pulses as measurement light emitted towards the object surfaces into an emission direction variated by rotation about at least one axis,
receiving measurement light reflected from the object surfaces,
measuring the respective alignment of the at least one axis, and
measuring the respective distance to a surface point based on the received measurement light,
wherein determining the distances to the surface points further includes:
transforming a respective light pulse into a series of separated sub-pulses of different energies by a fiber based optical coupler and a fiber network, the fiber network:
including a fiber delay line, and
being integrated in an EDFA or YDFA doped-fiber amplifier,
providing at least part of the fiber delay line,
digitally sampling received sub-pulses,
selecting at least one of the sub-pulses having an energy yielding an electrical signal amplitude in the non-saturated range of a receiving unit, and
determining said respective distance based on deducing a time-of-flight of the at least one selected sub-pulse.
11 . The method according to claim 10 , wherein the series comprises at least a portion of successive sub-pulses of decreasing energies.
12 . The method according to claim 10 , wherein received sub-pulses of a respective light pulse are identifiable as originating of this same light pulse by their temporal spacing being well known.
13 . The method according to claim 11 , wherein received sub-pulses of a respective light pulse are identifiable as originating of this same light pulse by their temporal spacing being well known.
14 . A computer program, which is stored on a non-transitory machine-readable medium, for controlling and/or carrying out the method according to claim 10 , when the program is executed in a control and analysis unit of a laser scanner or laser profiler.
15 . A computer program, which is stored on a non-transitory machine-readable medium, for controlling and/or carrying out the method according to claim 13 , when the program is executed in a control and analysis unit of a laser scanner or laser profiler.