Distance measurement instrument

Patent metadata

Field	Value
Publication number	US-10816646-B2
Application number	US-201715623944-A
Country	US
Kind code	B2
Filing date	Jun 15, 2017
Priority date	Dec 22, 2014
Publication date	Oct 27, 2020
Grant date	Oct 27, 2020

Abstract

A distance measurement instrument and a method of operating a distance measurement instrument are disclosed. According to some embodiments, a transmit light signal is transmitted by a transmitter unit along a transmit path at an emission time and a return light signal is received by a receiver unit at a receive time along a receive path. The return light signal is converted to a return electrical signal. At least one of the transmit path and the receive path is deflected by a deflection module at a deflection angle relative to an optical axis of the instrument. A time-dependent attenuation function is selected based on information relative to the deflection angle and attenuation is applied by an attenuator to at least one of the return light signal and the return electrical signal according to the selected time-dependent function. A measured distance may be determined by a processor unit based on at least the emission time and the receive time.

First claim

The invention claimed is:

1. A distance measurement instrument, comprising:
a transmitter unit configured to emit a transmit light signal toward a target along a transmit path at an emission time;
a receiver unit configured to receive at a receive time a return light signal along a receive path and to convert the return light signal to a return electrical signal;
at least one deflection module configured to deflect at least one of the transmit path and the receive path with a deflection angle relative to an optical axis of the instrument;
at least one attenuator configured to apply an attenuation to at least one of the return light signal and the return electrical signal according to a time-dependent function selected based on information relative to the deflection angle; and
a processor unit configured to determine a measured distance to the target based on at least the emission time and the receive time;
wherein a set of time-dependent attenuation functions are based on an optical arrangement and type of said at least one deflection module, and wherein for a certain orientation or displacement of said at least one deflection module, the at least one attenuator is configured to apply the attenuation according to the time-dependent function out of the set of time-dependent attenuation functions.

2. The instrument according to claim 1 , wherein the deflection module comprises at least one deflection element mounted for rotational motion and/or translational displacement such that at least one of the transmit path and the receive path is deflected with rotation and/or translational displacement of the deflection element.

3. The instrument according to claim 2 , further comprising a sensor operative to detect an angle of rotation of the deflection element and/or a displacement sensor operative to detect a translational displacement of the deflection element, wherein the information relative to the deflection angle is the detected angle of rotation and/or the detected translational displacement.

4. The instrument according to claim 2 , wherein the information relative to the deflection angle includes a starting position of the deflection element relative to the instrument optical axis and at least one of a rotation speed, a translation speed, and a displacement profile of the deflection element.

5. The instrument according to claim 2 , further comprising a deflection lens, wherein optical displacement due to the deflection element is converted to optical deflection, to produce angular deflection of the transmit path and/or the receive path across the instrument optical axis.

6. The instrument according to claim 2 , wherein the deflection element comprises at least one of a prism, a multi-faceted mirror, and a disk having a scalloped curving mirrored surface.

7. The instrument according to claim 1 , wherein the time-dependent attenuation function includes a maximum of attenuation at a critical time elapsed since the emission time of said transmit light signal.

8. The instrument according to claim 7 , wherein the critical time is dependent on at least one geometrical parameter of an optical subsystem with which the return light signal is received at the receiver unit.

9. The instrument according to claim 1 , further comprising a front lens having an optical path along the instrument optical axis, wherein the deflection module is located optically between the front lens and at least one of the transmitter unit and the receiver unit.

10. The instrument according to claim 1 , wherein the measurement instrument is further configured to regulate the attenuation of said attenuator for a travelling transmit light signal, as time passes, from a time event related to the emission of the travelling transmit light signal until reception of the return light signal corresponding to said travelling transmit light signal or until emission of a subsequent transmit light signal or until a time period elapsed since said time event exceeds a threshold.

11. A method of operating a measurement instrument, comprising:
transmitting a transmit light signal along a transmit path at an emission time;
receiving at a receive time a return light signal along a receive path;
deflecting, with at least one deflection module, at least one of the transmit path and the receive path at a deflection angle relative to an optical axis of the instrument;
converting the return light signal to a return electrical signal;
selecting a time-dependent attenuation function based on information relative to the deflection angle;
applying an attenuation to at least one of the return light signal and the return electrical signal according to the selected time-dependent attenuation function; and
determining a measured distance based on at least the emission time and the receive time;
wherein a set of time-dependent attenuation functions are based on an optical arrangement and type of said at least one deflection module, and wherein for a certain orientation or displacement of said at least one deflection module, the time-dependent attenuation function is selected out of the set of time-dependent attenuation functions.

12. The method according to claim 11 , further comprising detecting an angle of rotation and/or a translational displacement of a deflection element arranged to deflect said at least one of the transmit path and the receive path, wherein the information relative to the deflection angle includes the detected angle of rotation and/or the detected translational displacement.

13. The method according to claim 11 , wherein the information relative to the deflection angle includes a starting position of a deflection element arranged to deflect said at least one of the transmit path and the receive path relative to the instrument optical axis and at least one of a rotation speed, a translation speed, and a displacement profile of said deflection element.

14. The method according to claim 11 , wherein the time-dependent attenuation function includes a maximum of attenuation at a critical time elapsed since the emission time of said transmit light signal.

15. The method according to claim 14 , wherein the critical time is dependent on at least one geometrical parameter of an optical subsystem with which the return light signal is received.

16. The instrument according to claim 1 , further comprising a center unit having the instrument optical axis as optical axis and wherein said at least one deflection module, said transmitter unit, and said receiver unit are arranged within the center unit.

17. The instrument according to claim 16 , wherein the center unit is arranged to be mounted on an alidade for rotation about a first axis and the alidade is mounted on a base for rotation about a second axis intersecting the first axis.

18. The instrument according to claim 1 , wherein the time-dependent function to be used is selected depending on the orientation, position and/or configuration of the deflection module in the distance measurement instrument.

Assignees

• Trimble Ab

Inventors

• Lekås Johan
• Svanholm Set
• Kosakowski Alex Slawomir

Classifications

• G01S7/489

  Gain of receiver varied automatically during pulse-recurrence period · CPC title

• G01S17/42 Primary

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

• G01S17/10

  using transmission of interrupted, pulse-modulated waves (determination of distance by phase measurements G01S17/32) · CPC title

• G01S7/4865

  Time delay measurement, e.g. time-of-flight measurement, time of arrival measurement or determining the exact position of a peak (peak detection in noise, signal conditioning G01S7/487) · CPC title

• G01S7/4817 Primary

  relating to scanning · CPC title