Laser distance measuring module having polarization analysis

Patent metadata

Field	Value
Publication number	US-10754010-B2
Application number	US-201715820418-A
Country	US
Kind code	B2
Filing date	Nov 21, 2017
Priority date	Nov 22, 2016
Publication date	Aug 25, 2020
Grant date	Aug 25, 2020

Abstract

A distance measuring method and an electronic laser distance measuring module, for determining a distance to a target object, wherein the transmitted signal is emitted with selected polarization states by a transmitting unit of the laser distance measuring module. The transmitted signal is emitted and the received signal is acquired such that a polarization identifier of the polarization state of the transmitted signal adheres to the received signal and an evaluation of the received signal is derived based on the polarization identifier, to take into consideration multiple reflections during the processing of the received signal to determine the distance.

First claim

What is claimed is:

1. A method of measuring a distance to a target object, the method comprising:
emitting a transmitted signal in a defined polarization state;
receiving at least parts of the transmitted signal reflected on the target object as a received signal, wherein the transmitted signal is emitted and the received signal is acquired such that a polarization identifier of the defined polarization state of the transmitted signal adheres to the received signal, wherein the polarization identifier is selected as an indication as to whether the received signal originates from a single reflection or a multiple reflection of the transmitted signal;
wherein:
the transmitted signal is emitted as a transmitted signal sequence of individual partial signals, wherein the polarization state of individual partial signals is different,
a first partial signal of the transmitted signal is emitted in a defined first polarization state,
a second partial signal of the transmitted signal is emitted in a defined second polarization state,
at least a portion of the first partial signal reflected on the target object is acquired as a first received partial signal and at least a portion of the second partial signal reflected on the target object is acquired as a second received partial signal,
a first intensity of at least a part of the first received partial signal is measured,
a second intensity of at least a part of the second received partial signal is measured, and
based on the first intensity and the second intensity, a first comparison value is derived,

based on the first comparison value, deriving an evaluation of the received signal is derived; and
processing the received signal to derive the distance to the target object therefrom based on the evaluation of the received signal.

2. The ng method according to claim 1 , wherein the first and the second partial signals are emitted as completely linearly polarized radiation or circularly polarized radiation.

3. The method according to claim 1 , wherein the polarization state of individual partial signals is changed during the determination of the distance according to a defined chronological sequence.

4. The method according to claim 1 , wherein the received signal is analyzed by means of waveform digitization.

5. The method according to claim 1 , wherein:
the first partial signal of the transmitted signal is emitted as completely linearly polarized radiation or completely circularly polarized radiation, and
the second partial signal of the transmitted signal is emitted as completely polarized radiation having a polarization state orthogonal in relation to the first partial signal.

6. The method of claim 5 , wherein:
a third partial signal of the transmitted signal is emitted as completely linearly polarized radiation or completely circularly polarized radiation,
a fourth partial signal of the transmitted signal is emitted as completely polarized radiation having a polarization state orthogonal in relation to the third partial signal,
at least a portion of the third partial signal reflected on the target object is acquired as a third received partial signal and at least parts of the fourth partial signal reflected on the target object is acquired as a fourth received partial signal,
a third intensity of at least a part of the third received partial signal is measured using a first polarization analyzer,
a fourth intensity of at least a part of the fourth received partial signal is measured using a second polarization analyzer,
based on the third intensity and the fourth intensity, a second comparison value is derived, and
the second comparison value is taken into consideration for an evaluation of the third and/or fourth received partial signal.

7. The method of claim 5 , wherein the first or second comparison value are compared to a first or second threshold value, respectively, based on a set of defined scattering properties representative of at least one target object, based on at least one element of the following group:
a geometrical surface structure,
a surface porosity,
albedo properties,
reflection properties,
absorption properties,
and phase properties.

8. The method of claim 1 , wherein:
at least one polarization identifier of the transmitted signal is known,
at least one polarization identifier of the received signal is derived based on the at least one polarization identifier of the transmitted signal or the at least one polarization identifier of the received signal,
at least one evaluation parameter of the following group is derived:
a degree of polarization (DOP) of the received signal, an angle of polarization of the received signal,
a depolarization factor between transmitted signal and received signal,

wherein the at least one evaluation parameter is taken into consideration for the evaluation of the received signal during the processing of the received signal to determine the distance to the target object.

9. A distance measuring module for determining a distance to a target object, the distance measuring module comprising:
a transmitting unit for emitting a transmitted signal;
a receiving unit for receiving at least parts of the transmitted signal reflected on the target object as a received signal; and
a monitoring and control unit for processing the received signal to derive the distance to the target object therefrom,
wherein:
the transmitting unit and the receiving unit are configured such that:
the transmitted signal is emitted in a defined polarization state, and
the transmitted signal is emitted and the received signal is acquired such that a polarization identifier of the polarization state of the transmitted signal adheres to the received signal, wherein the polarization identifier is selected so that it is an indication for whether the received signal originates from a single reflection or a multiple reflection of the transmitted signal,

wherein the transmitted signal is emitted as a transmitted signal sequence of individual partial signals, wherein the polarization sttae of individual partial signals is different,
at least a portion of the first partial signal reflected on the target object is acquired as a first received partial signal and at least a portion of the second partial signal reflected on the target object is acquired as a second received partial signal,
a first intensity of at least a part of the first received partial signal is measured,
a second intensity of at least a part of the second received partial signal is measured,
based on the first intensity and the second intensity, a first comparison value is derived, and
an evaluation of the received signal is derived by the monitoring and control unit based on the first comparison value, and is taken into consideration during the processing of the received signal to determine the distance to the target object.

10. The distance measuring module of claim 9 , wherein the transmitting unit is configured such that the transmitted signal is emitted as a transmitted signal sequence of individual partial signals, wherein the polarization state of individual partial signals is changed in the scope of the determination of the distance according to a defined chronological sequence.

11. The distance measuring module according to claim 9 , wherein the monitoring and control unit is configured such that the received signal is analyzed by means of waveform digitization.

12. The distance measuring module according to claim 9 , wherein the distance measuring module is configured such that:
the first partial signal of the transmitted signal is emitted as completely linearly polarized radiation

Assignees

• Hexagon Technology Ct Gmbh

Inventors

• Hinderling Jürg
• Piok Thomas

Classifications

• G01S17/08 Primary

  for measuring distance only (indirect measurement G01S17/46; active triangulation systems G01S17/48) · CPC title

• G01S7/487

  Extracting wanted echo signals {, e.g. pulse detection} · CPC title

• G01S7/499

  using polarisation effects · CPC title

• G01S17/42

  Simultaneous measurement of distance and other co-ordinates (indirect measurement G01S17/46) · CPC title

• G01C3/02

  Details · CPC title