Distance measuring device

Patent metadata

Field	Value
Publication number	US-9519052-B2
Application number	US-201615045730-A
Country	US
Kind code	B2
Filing date	Feb 17, 2016
Priority date	Jun 26, 2009
Publication date	Dec 13, 2016
Grant date	Dec 13, 2016

Abstract

An optical device is disclosed that may be employed in distance measuring devices. In at least one embodiment, the optical device includes a control unit that is adapted to cause at least one control signal generator unit to generate at least one control signal according to a predetermined temporal function on the basis of an elapsed time from a predetermined point in time. On the basis of the generated at least one control signal, at least one parameter of a receiver unit may be adjusted during the travel time of the optical pulse, wherein the at least one parameter affects the dynamic range of the receiver unit. In this way, the dynamic range of the receiver unit may be increased. A method is further disclosed for operating such an optical device, along with a distance measuring device including such an optical device and a surveying instrument including such a distance measuring device.

First claim

The invention claimed is:

1. An optical device including:
an optical radiation source configured to emit optical pulses;
a receiver configured to receive reflected optical pulses;
a time-measuring unit configured to generate an elapsed time from a point in time related to emission of an optical pulse from the optical radiation source;
at least one control signal generator unit configured to generate at least one control signal according to a temporal function on a basis of the elapsed time; and
a control unit configured to adjust at least one parameter of said receiver affecting the dynamic range of said receiver based on the generated at least one control signal,
wherein the temporal function is configured such that the temporal function at least partly includes a shape that is determined on a basis of parameters of an optical system of the optical device.

2. The optical device of claim 1 , wherein the optical system is an optical system configured to collimate the emitted optical pulses into a beam.

3. The optical device of claim 1 , wherein the optical system includes at least one of one or more lens elements, prisms, wave guides and mirror elements.

4. The optical device of claim 1 , wherein the control unit is configured to adjust said at least one parameter during a travel time of an optical pulse from the optical device to a target and back.

5. The optical device of claim 1 , wherein the control unit is configured to adjust said at least one parameter until another pulse is emitted from the optical radiation source.

6. The optical device of claim 1 , wherein the receiver includes a photodetector unit configured to generate electrical return signals from said reflected optical pulses, said at least one parameter including the optical responsivity of the photodetector unit.

7. The optical device of claim 1 , wherein said receiver further comprises at least one of:
a variable attenuator unit configured to attenuate electrical return signals generated from said reflected optical pulses by a photodetector unit, and
a variable optical attenuator unit configured to attenuate said reflected optical pulses, wherein said at least one parameter includes the attenuation of at least one of said variable attenuator unit and the attenuation of said variable optical attenuator unit.

8. The optical device of claim 1 , wherein said point in time is a point in time when the optical pulse is emitted, or wherein said point in time is a point in time when an optical reference pulse is received at the receiver, said optical reference pulse being emitted concurrently with or in connection to emission of the optical pulse from the optical radiation source.

9. The optical device of claim 1 , wherein the receiver includes a variable gain amplifier unit configured to amplify electrical return signals generated from said reflected optical pulses by a photodetector unit, wherein said at least one parameter includes the gain of said variable gain amplifier unit.

10. The optical device of claim 1 , wherein said control unit is further configured to, if the elapsed time exceeds a maximum elapsed time, reset said time-measuring unit.

11. The optical device of claim 10 , wherein the maximum elapsed time is set on the basis of the maximum measurable travelling time of the at least one optical pulse from the point in time.

12. The optical device of claim 1 , wherein the temporal function at least partly includes a shape matching or approximating at least one of an estimated function of the received optical power versus the elapsed time for said optical pulse and an inverse of said estimated function.

13. The optical device of claim 1 , wherein the temporal function at least partly includes a shape matching or approximating at least one of an estimated function of the received optical power versus the elapsed time for an optical pulse reflected from a target having a substantially constant albedo, and an inverse of said estimated function.

14. The optical device of claim 1 , wherein the temporal function at least partly includes a shape according to a step function, a polynomial function, a linear function, a quadratic function, a rectangular function, an exponentially decaying function, or any combination thereof.

15. The optical device of claim 1 , wherein the control signal generator unit comprises a memory unit configured to store data, and the control signal generator unit is configured to generate control signals by retrieving control signal values previously stored in the memory unit.

16. The optical device of claim 1 , wherein the control unit is configured to set said at least one parameter of said receiver to a first value at the instant the optical pulse is emitted from the optical radiation source or after the optical pulse has been emitted from the optical radiation source and then, adjust said at least one parameter temporarily to other values as a function of time.

17. The optical device of claim 1 , wherein the control unit is configured to set an attenuation or an amplification of said receiver to a high value or a low value, respectively, at the instant an optical pulse is emitted from the optical radiation source and then, immediately after the optical pulse has been emitted, as the elapsed time increases, decrease or increase, respectively, the attenuation or amplification, respectively, temporarily on the basis of the generated at least one control signal until another pulse is emitted from the optical radiation source.

18. A distance measuring device including:
an optical device; and
a processor configured to determine a distance to a target from said distance measuring device on the basis of a comparison between a transmitted optical pulse and a received optical pulse;
wherein said optical device includes:
an optical radiation source configured to emit optical pulses;
a receiver configured to receive reflected optical pulses;
a time-measuring unit configured to generate an elapsed time from a point in time related to emission of an optical pulse from the optical radiation source;
at least one control signal generator unit configured to generate at least one control signal according to a temporal function on a basis of the elapsed time; and
a control unit configured to adjust at least one parameter of said receiver affecting the dynamic range of said receiver based on the generated at least one control signal,
wherein the temporal function is configured such that the temporal function at least partly includes a shape that is determined on a basis of parameters of an optical system of the optical device.

19. The distance measuring device of claim 18 , wherein the optical system is an optical system configured to collimate the emitted optical pulses into a beam.

20. The distance measuring device of claim 18 , wherein the optical system includes at least one of one or more lens elements, prisms, wave guides and mirror elements.

Assignees

• Trimble Ab

Inventors

• Gusev Yuri P

Classifications

• G01S17/10

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

• G01C15/002

  Active optical surveying means (optical plumbing G01C15/105) · CPC title

• G01S7/489 Primary

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

• G01C3/08

  Use of electric radiation detectors · CPC title

• G01S7/4865 Primary

  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