US 9,804,263 B2 · Ambiguity compensation in time-of-flight ranging

Abstract

Methods and apparatus are provided for measuring distance from an instrument origin to each of a plurality of points in an environment. Laser pulses are emitted along a measurement axis at successive displacements about the origin. The emission time of each pulse is time-shifted relative to a fixed rate. The time shift corresponds to an index of a repetitive sequential pattern. Received pulses are detected at respective arrival times. For each received pulse: a current apparent distance is determined, a measured delta distance is calculated, a range interval is assigned by comparing measured delta distance with an expected delta distance synchronized with the index of the latest emitted pulse, the current apparent distance is defined to be a true measured distance for any received pulse assigned to a first time interval, otherwise the current apparent distance is defined to be a false measured distance.

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Claims20

Dependent claims

A method of measuring distance from an instrument origin to each of a plurality of points in an environment, comprising:

a. emitting laser pulses along a measurement axis at successive displacements about the instrument origin, the emission time of each emitted laser pulse having a time shift relative to nominal fixed rate, where the time shift corresponds to an index of a repetitive sequential pattern,
b. detecting received pulses at respective arrival times,
c. for each received pulse,
i. determining a current apparent distance using the arrival time of the received pulse and the emission time of the latest emitted pulse,
ii. calculating a measured delta distance between the current apparent distance and a previous apparent distance,
iii. assigning a range interval by comparing the measured delta distance with at least one expected delta distance, where each expected delta distance is synchronized with the index of the repetitive sequential pattern of the latest emitted pulse,
iv. defining the current apparent distance to be a true measured distance for any received pulse assigned to a first range interval, and
v. defining the current apparent distance to be a false measured distance for any received pulse not assigned to the first range interval, and
d. storing the true measured distances.

6 more elements

Apparatus for measuring distance from an instrument origin to each of a plurality of points in an environment, comprising:

a. a laser source to emit laser pulses along a measurement axis at successive displacements about the instrument origin, the emission time of each emitted laser pulse having a time shift relative to nominal fixed rate, where the time shift corresponds to an index of a repetitive sequential pattern,
b. a reception unit to detect received pulses at respective arrival times,
c. at least one control unit operative, for each received pulse, to
i. determine a current apparent distance using the arrival time of the received pulse and the emission time of the latest emitted pulse,
ii. calculate a measured delta distance between the current apparent distance and a previous apparent distance,
iii. assign a range interval by comparing the measured delta distance with at least one expected delta distance, where each expected delta distance is synchronized with the index of the repetitive sequential pattern of the latest emitted pulse,
iv. define the current apparent distance to be a true measured distance for any received pulse assigned to a first range interval,
v. define the current apparent distance to be a false measured distance for any received pulse not assigned to the first range interval, and
d. a memory operative to store the true measured distances.

6 more elements

Dependencies are inferred from the claim text.

Description9,552 words

Summary885 words

#This application claims priority to French Patent Application No. FR 13/02082, filed Sep. 9, 2013, the contents of which are incorporated herein by reference in their entirety for all purposes.

#The present invention relates to the field of electronic distance measurement. More particularly, the present invention relates to methods and apparatus for compensating ambiguity in time-of-flight ranging.

#Ambiguity interval limitation is a classic issue for distance measurement techniques.

Brief description of the drawings42 figures

#These and other aspects and features of the present invention will be more readily understood from the embodiments described below with reference to the drawings, in which:

#FIG. 1 schematically illustrates a system for implementing a distance measurement scheme in accordance with some embodiments of the invention;

#FIG. 2 schematically illustrates elements of a system for implementing a distance measurement scheme in accordance with some embodiments of the invention;

Detailed description7,891 words

#FIG. 1 schematically illustrates a scanner system 100 for implementing a distance measurement scheme in accordance with some embodiments of the invention. System 100 includes a distance meter 105, one or more deflection units 110, and a system control unit 115. Distance meter 105 emits laser pulses along a path 120, which is deflected over a scan angle 125 by deflection unit/s 110. Distance meter 105 detects laser pulses returning from a scene or object 130 and determines a measured distance based on time of flight of each pulse. System control unit 115 and/or distance meter 105 can include one or more processors 135, 140 programmed to carry out functions described herein. System 100 can also have a communications link 145 to enable exchange of data with an external processor (not shown) programmed to carry out functions described herein.

#A scanner system used on a moving vehicle can have a single deflection unit 110 to scan the laser path 120 about a vehicle path. A stationary scanner system can have two deflection units 110, each scanning the laser path about one of two orthogonal axes.

#FIG. 2 schematically illustrates elements of a scanner system 200 for implementing a distance measurement scheme in accordance with some embodiments of the invention. System 200 includes a distance meter 205, a fast deflection unit 210 rotating a mirror 215 about a first axis 220, a slow deflection unit rotating mirror 215 about a second axis 230, and a system control unit 235. Distance meter 205 emits laser pulses along a path 240, which is deflected over a scan angle 245 by deflection units 210 and 225. Distance meter 205 detects laser pulses returning from a scene or object 250 and determines a measured distance based on time of flight of each pulse.

Facts

Application

14/445,895Filed 29 Jul 2014

Priority

FR 13 020829 Sep 2013

Published

US 2015/0070683 A112 Mar 2015

Granted

31 Oct 2017

Term ends

11 Mar 2036

Estimated · how

20 years from earliest known nonprovisional domestic filing plus recorded patent term adjustment, including 591 days of adjustment. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification3 codes

G01S 17/10
For measuring distance only: using transmission of interrupted, pulse-modulated waves
G01S 17/42
Systems determining position data of a target: simultaneous measurement of distance and other co-ordinates
G01S
Radio direction-finding

Timeline

9 Sep 2013Priority claimedFR 13 02082
29 Jul 2014Application filedUS 14/445,895
30 Sep 2014Assigned to Trimble ABassignment of assignor's interest
12 Mar 2015PublishedUS 2015/0070683 A1
31 Oct 2017GrantedUS 9,804,263 B2
12 Oct 2026TodayWithin its term
11 Mar 2036Term endsEstimated, includes 591 days of adjustment

Ambiguity compensation in time-of-flight ranging

Life of this patent

Ambiguity compensation in time-of-flight ranging

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims20

Description9,552 words

Classification3 codes

Life of this patent

Description9,552 words

Drawings