Method for Measuring Distances

• US 20120257186A1
• Filed: 09/23/2011
• Published: 10/11/2012
• Est. Priority Date: 04/07/2011
• Status: Active Grant

• Current Assignee: RIEGL Laser Measurement Systems GmbH
• Original Assignee: RIEGL Laser Measurement Systems GmbH
• Inventors: Ullrich, Andreas, Rieger, Peter
• Granted Patent: US 9,268,013 B2
• Time in Patent Office: Days
• US Class Current: 356/5.01
• CPC Class Codes: G01S 17/18 wherein range gates are used
• CPC Class Codes: G01S 7/487 Extracting wanted echo signals , e.g. pulse detection

Abstract

A method for measuring distances of targets by measuring the time of flight of pulses, in particular laser pulses, reflected on those targets, including the steps of; transmitting pulses having a pulse interval which varies according to a modulation signal as transmitted pulses, and concomitantly recording of reflected pulses as received pulses; determining a first series of distance measurement values from times of flight between transmitted pulses and those received pulses which are respectively received within a first time window following each transmitted pulse; determining at least a second series of distance measurement values from times of flight between transmitted pulses and those received pulses which are respectively received within a second time window following each transmitted pulse; and determining that series of distance measurement values which is least affected by the modulation signal as result of the distance measurement.

Claims

1. A method for measuring distances of targets by measuring the time of flight of pulses reflected on those targets, comprising the steps of:

transmitting pulses having a pulse interval which varies according to a modulation signal as transmitted pulses, and concomitantly recording of reflected pulses as received pulses;

determining a first series of distance measurement values from times of flight between transmitted pulses and those received pulses which are respectively received within a first time window following each transmitted pulse;

determining at least a second series of distance measurement values from times of flight between transmitted pulses and those received pulses which are respectively received within a second time window following each transmitted pulse; and

determining that series of distance measurement values which is least affected by the modulation signal as result of the distance measurement.

2. The method according to claim 1, wherein the first and second time windows are approximately equal in length to an average pulse interval of the transmitted pulses.

3. The method according to claim 1, wherein the first and second time windows are offset to one another by approximately an integer multiple of an average pulse interval of the transmitted pulses.

4. The method according to claim 1, wherein the modulation signal is a random signal.

5. The method according to claim 1, wherein the modulation signal is a pseudorandom signal.

6. The method according to claim 5, wherein the modulation signal is based on a Barker code.

7. The method according to claim 1, wherein the least affected series is determined by calculating signal energies of the series and selecting the series having the lowest signal energy.

8. The method according to claim 1, wherein the least affected series is determined by calculating autocorrelations of the series and selecting the series having the highest autocorrelation.

9. The method according to claim 1, wherein the least affected series is determined by calculating cross-correlations of the series with said modulation signal and selecting the series having the lowest cross-correlation.

10. The method according to claim 1, wherein the least affected series is determined by frequency-analyzing of the series and selecting the series having smallest high-frequency components.

11. The method according to claim 1, wherein the transmitted pulses are continuously directed to the same target.

12. The method according to claim 11, wherein the transmitted pulses are laser pulses.

13. The method according to claim 1 for laser scanning, wherein the transmitted pulses are laser pulses and are progressively directed to different targets.

14. A laser distance measuring apparatus configured to implement the method of claim 12.

15. A laser scanner configured to implement the method of claim 13.