DEVICE AND METHOD FOR THE DETERMINATION OF DISTANCE BY MEANS OF LIGHT PULSES

• US 20100066995A1
• Filed: 02/29/2008
• Published: 03/18/2010
• Est. Priority Date: 03/02/2007
• Status: Active Grant

• Current Assignee: Trimble Germany GmbH (Trimble Inc.)
• Original Assignee: TopoSys Topographische Systemdaten GmbH
• Inventors: Rindle, Peter
• Granted Patent: US 8,212,998 B2
• Time in Patent Office: Days
• US Class Current: 356/5.30
• CPC Class Codes: G01S 17/18 wherein range gates are used
• CPC Class Codes: G01S 7/4817 relating to scanning
• CPC Class Codes: G01S 7/4818 using optical fibres
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating

Abstract

A device (1) for the determination of distance by means of light pulses is disclosed. The device (1) comprises a light source (2) for emitting light pulses with a specified frequency, a detector (8) for receiving the light pulses emitted and reflected by the light source, and a controller (4) which is in communication with the light source (2) and the detector (8) and which can control said light source and detector by means of signals. The device (1) further comprises at least two timers (Z1, Z2, Z3) which are connected to the controller (4) and the detector (8). Said controller (4) is designed in such a way that when a light pulse is emitted by the light source (2), the controller (4) generates a start signal which triggers the time measurement by each one of the at least two timers, in order, and beginning again from the start. The detector (8) is designed in such a way that upon receiving a reflected light pulse, said detector (8) generates a stop signal which is forwarded to the at least two timers (Z1, Z2, Z3) and which stops the time measurement by the timer of the at least two timers, to which at that instant a measuring window is assigned by the controller (4). The device can preferably be designed as a fiber-optic scanner. In addition, a method for the determination of distance by means of light pulses is disclosed.

Claims

1-12. -12. (canceled)

13. Apparatus for measuring distance by means of light pulses, comprising:

a light source for the emission of a train of light pulses,

a detector for receiving light pulses emitted by the light source and reflected from targets,

at least two timers, and

a controller in communication with and adapted to control the light source and the detector and the at least two timers,

wherein the controller is adapted to generate a start signal for each emitted light pulse received by the detector, each start signal triggering a time measurement by one of the at least two timers during a measurement window temporarily assigned to said one of the at least two timers, the timers being triggered by successive emitted light pulses in a repetitive sequence, and

wherein the controller is adapted to generate a stop signal when a reflected light pulse is received by the detector during the measurement window, the stop signal serving to stop a time measurement by said one of the at least two timers to which the measurement window is assigned,

whereby the at least two timers are capable of measuring the travel time of respective light pulses which are simultaneously in transit.

14. Apparatus according to claim 13, wherein the controller is adapted to temporarily assign a respective measurement window to one of the at least two timers in a repetitive sequence in a triggering order of the at least two timers, without temporal overlap between the measurement windows.

15. Apparatus according to claim 13, wherein the controller is adapted to temporarily assign measurement windows to the at least two timers such that the measurement window assigned to a second one of the at least two timers starts at a point in time when a measurement window assigned to a first one of the at least two timers ends, so that each light pulse received by the detector falls within a measurement window.

16. Apparatus according to claim 13, wherein the controller is adapted to temporarily assign measurement windows to the at least two timers such that a time period between successive triggerings of time measurement by one of the at least two timers is a whole number multiple of a time period between the triggerings of time measurement by a successive timer of the at least two timers.

17. Apparatus according to claim 13, wherein the controller is adapted to temporarily assign measurement windows to the at least two timers such that a buffer period is provided between successive measurement windows.

18. Apparatus according to claim 13, further comprising

a transmission unit in which light pulses emitted by the light source are guided via a first rotating mirror which is tilted toward its rotation axis onto circularly-arranged input ends of glass fibers of a first glass fiber array,

a reception unit in which light pulses received at input ends of glass fibers of a second glass fiber array having circularly-arranged output ends are guided onto the detector via a second rotating mirror which is tilted toward its rotation axis, and

a motor to drive the first rotating mirror and the second rotating mirror,

wherein the controller is in communication with and is adapted to control the transmission unit and the reception unit and the motor.

19. Apparatus according to claim 17, wherein the light source comprises one of:

a light emitting diode, a glass fiber-coupled light emitting diode, a modulated continuous-wave (CW) laser diode, and a continuous-wave (CW) laser.

20. Apparatus according to claim 17, wherein each of the first glass fiber array and the second glass fiber array comprises 128 or 300 glass fibers.

21. Apparatus according to claim 17, wherein the motor comprises one of a high-speed direct-current motor and a high-speed synchronous motor.

22. Apparatus according to claim 17, wherein the first glass fiber array and the second glass fiber array have a common reference fiber useful for calibration purposes.

18-1. Apparatus according to claim 17, wherein the output ends of the fibers of the first glass fiber array are arranged in a rectilinear transmission row in the focal plane of a first lens, and the input ends of the glass fibers of the second glass fiber array are arranged in a rectilinear reception row in the focal plane of a second lens.

23. A method for measuring distance by means of light pulses, comprising:

generating a start signal upon emission of each of a plurality of light pulses from a light source,

using each start signal to trigger a time measurement during a respective measurement window temporarily assigned to one of at least two timers, such that the timers are triggered by successive emitted light pulses in a repetitive sequence,

generating a stop signal upon reception of each of a plurality of reflected light pulses at a detector,

using each stop signal to stop a time measurement occurring during a corresponding time measurement window,

whereby the at least two timers are capable of measuring the travel time of respective light pulses which are simultaneously in transit.

24. The method of claim 23, wherein measurement windows are assigned to avoid temporal overlap between successive measurement windows.

25. The method of claim 23, wherein measurement windows are assigned such that each measurement window starts at a point in time when prior measurement window ends, so that each received light pulse falls within a measurement window.

26. The method of claim 23, wherein measurement window are assigned such that a time period between successive triggerings of time measurement by one of the at least two timers is a whole number multiple of a time period between the triggerings of time measurement by a successive timer of the at least two timers.