Method and optical receiver with easy setup means for use in position measurement systems

• US 6,630,993 B1
• Filed: 03/21/2000
• Issued: 10/07/2003
• Est. Priority Date: 03/22/1999
• Status: Expired due to Term

• Current Assignee: 7D Kinematic Metrology Inc.
• Original Assignee: Arc Second, Inc. (Nikon Corporation)
• Inventors: Dornbusch, Andrew, Gaff, Doug, Wain, Frey, Sobel, Michael J., Hedges, Thomas M., Pendleton, Edmund S., Casteel, Scott C.
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US09/532,099
• Time in Patent Office: 1,295 Days
• Field of Search: 356/141.1, 356/141.4, 356/141.5, 356/152.1, 702/150-153
• US Class Current: 356/141.4
• CPC Class Codes: G01C 15/002 Active optical surveying means optical plumbing G01C15/105
• CPC Class Codes: G01S 1/54 Narrow-beam systems producing at a receiver a pulse-type envelope signal of the carrier wave of the beam, the timing of which is dependent upon the angle between the direction of the receiver from the beacon and a reference direction from the beacon; Overlapping broad beam systems defining a narrow zone and producing at a receiver a pulse-type envelope signal of the carrier wave of the beam, the timing of which is dependent upon the angle between the direction of the receiver from the beacon and a reference direction from the beacon
• CPC Class Codes: G01S 5/16 using electromagnetic waves other than radio waves
• CPC Class Codes: G06Q 10/08 Logistics, e.g. warehousing, loading or distribution; Inventory or stock management

Abstract

Positions can be precisely and accurately fixed instantaneously within a three-dimensional workspace. A system of two or more transmitters each continuously sweep the workspace with two fanned laser beams which are preferably about 90 degrees apart on the rotational axis of the transmitter. A receiving instrument includes, preferably, two light detectors which detect the time at which each fanned laser beam is incident thereon. The light detectors also detect a synchronization pulse from each transmitter that is emitted once per revolution. Beams from different transmitters are differentiated by different rotational speeds and, therefore, different beam incidence cycles. Because three intersecting planes uniquely define a point in three-dimensional space, by detecting at least three of the fan beams from the transmitters, the receiving instrument can calculate its position in the workspace. A Quick Calc setup procedure allows the use to define a desired coordinate system within the workspace.

Claims

1. An improved position optical detector apparatus utilizable in a measurement system for generating x-y-z data within a measurement field including a plurality of rotatably supported optical transmitters with each transmitter spaced apart from the others in the measurement field and being operatively related through a reference frame within the measurement field to define an intersection between vectors for each transmitter with each transmitter including laser means to generate two rotating substantially planar beams and a strobe means for periodically generating a strobe pulse for each transmitter at a predetermined point in the rotation of each transmitter, said apparatus comprising

a user-movable receiving instrument comprising:

at least one light detector for generating an electric signal each time one of the beams or optical strobe pulses illuminates that light detector as it is positioned within said measurement field;

memory means storing calibration data uniquely defining predetermined angular parameters of said beams; and

means for calculating the x-y-z data corresponding to the position of said detector within said measurement field using said calibration data and said electric signals from said light detector indicative of said times at which one of the beams or optical strobe pulses illuminates that detector.

2. The improved apparatus of claim 1, wherein said user-movable receiving instrument further comprises a user interface for receiving an input of said calibration data.

3. The improved apparatus of claim 1, wherein said user-movable receiving instrument further comprises a serial port for receiving a transmission of said calibration data.

4. The improved apparatus of claim 3, wherein said serial port is an optical port.

5. The improved apparatus of claim 3, wherein said serial port is a cable port.

6. The improved apparatus of claim 1, wherein said user-movable receiving instrument further comprises a port for coupling said instrument with one of said optical transmitters so that said calibration data can be transmitted from a memory unit in said optical transmitter to said memory means of said user-moveable receiving instrument.

7. The improved apparatus of claim 6, wherein said serial port is an optical port.

8. The improved apparatus of claim 1, wherein said stored calibration data uniquely defines an angular separation between said fan beams, a tilt angle for each of said fan beams measured from vertical and a rotational velocity for each of said transmitters.

9. The improved apparatus of claim 1, wherein said strobe pulse defines a zero reference for the rotation of that transmitter.

10. The improved apparatus of claim 8, wherein said rotational velocity calibration data is unique for each transmitter in the system and the velocity calibration data for each transmitter enables said position measurement apparatus to differentiate between transmitters operational within said measurement field.

11. The improved apparatus of claim 1, additionally including high speed timer means for making differential timing measurements between the electrical signals generated by each of said at least one light detector.

12. The improved apparatus of claim 11, additionally including means responsive to said differential timing measurements for calculating for each revolution of one of said transmitters angular data between said optical strobe pulse and the laser beams respectively.

13. The improved apparatus of claim 1, further comprising:

a plurality of tracker means for accumulating sequential incoming electric signals from each of said light detectors; and

synchronization means for associating each of said incoming electrical signals with one of said tracker means.

14. The improved apparatus of claim 13, further comprising pulse track reconciling means for associating a set of three related electric signals as being from a single transmitter of said system within a single transmit period.

15. The improved apparatus of claim 13, further comprising multi-path pulse tracking means for determining whether some of said electric signals from said light detector are caused by light from said transmitters which is reflected before striking said light detector rather than a direct line-of-sight beam from one of said transmitters striking said light detector.

16. The improved apparatus of claim 1, wherein said means for calculating said x-y-z position data comprises a matrix calculation means wherein the matrix notation for said calculation can be represented as follows:

17. The improved apparatus of claim 16, wherein the matrix may alternatively be solved utilizing a least squares reduction mathematical technique.

18. The improved apparatus of claim 16, wherein the matrix may be solved utilizing a single value decomposition mathematical technique.

19. An improved method of implementing an optical detector apparatus utilizable in a measurement system for generating x-y-z data within a measurement field including a plurality of rotatably supported optical transmitters with each transmitter spaced apart from the others in the measurement field and being operatively related through a reference frame within the measurement field to define an intersection between vectors for each transmitter with each transmitter including laser means to generate two rotating substantially fan shaped beams and a strobe means for generating a strobe pulse for each transmitter at a predetermined point in the rotation of each transmitter, said method comprising:

storing calibration data in a memory means on said receiving instrument, said calibration data comprising predetermined angular parameters of said beams;

positioning a user-movable receiving instrument at a location for which position data will be generated;

generating an electric signal with at least one light detector on said receiving instrument at said location, said generating an electric signal being performed each time one of the fan beams or optical strobe illuminates that light detector; and

calculating the x-y-z data corresponding to the position of said detector within said measurement field using said calibration data stored in said memory means of said receiving instrument and said electric signals from said light detector indicative of said times at which one of the fan beams or optical strobe illuminates that detector.

20. The improved method of claim 19, further comprising inputting said calibration data to said user-movable receiving instrument with a user interface.

21. The improved method of claim 19, further comprising transmitting said calibration data into said user-movable receiving instrument through a serial port of said instrument.

22. The improved method of claim 21, wherein said serial port is an optical port.

23. The improved method of claim 21, wherein said serial port is a cable port.

24. The improved method of claim 19, further comprising:

interfacing said instrument with one of said optical transmitters; and

transmitting said calibration data from a memory unit in said optical transmitter to said memory means of said user-movable receiving instrument.

25. The improved method of claim 24, wherein said interfacing comprises optically interfacing said receiving instrument and said optical transmitter.

26. The improved method of claim 19, wherein said stored calibration data uniquely defines an angular separation between said fan beams, a tilt angle for each of said fan beams measured from vertical and a rotational velocity for each of said transmitters.

27. The improved method of claim 19, wherein said strobe pulse defines a zero reference for the rotation of that transmitter.

28. The improved method of claim 26, wherein said rotational velocity calibration data is unique for each transmitter in the system;

and said method further comprising differentiating light pulses as originating with a particular transmitter in said measurement field based on said velocity calibration data.

29. The improved method of claim 19, further comprising making differential timing measurements between the electrical signals generated by each of said at least one light detector.

30. The improved method of claim 29, further comprising calculating for each revolution of one of said transmitters angular data between said optical strobe pulse and the laser fan beams respectively based on said differential timing measurements.

31. The improved method of claim 19, further comprising tracking optical signals from said transmitters received by said receiving instrument by accumulating sequential incoming electric signals from each light detector and associating each of said incoming electrical signals with one of a plurality of tracker means.

32. The improved method of claim 31, further comprising associating a set of three related electric signals as being from a single transmitter of said system within a single transmit period.

33. The improved method of claim 19, further comprising determining whether some of said electric signals from said light detector are caused by light from said transmitters which is reflected before striking said light detector rather than a direct line-of-sight beam from one of said transmitters striking said light detector.

34. The improved method of claim 19, wherein said step of calculating said x-y-z position data comprises performing a matrix calculation wherein the matrix notation for said calculation can be represented as follows:

 

A<sub>2n×

3</sub>{right arrow over (P)}<sub>3×

1</sub>={right arrow over (b)}<sub>2n×

1</sub>

wherein the subscripts indicate dimensions of the matrix and the x-y-z detector position in the user reference can be calculated by solving the above equation for P.

35. The improved method of claim 34, wherein the matrix may alternatively be solved utilizing a least squares reduction mathematical technique.

36. The improved method of claim 34, wherein the matrix may be solved utilizing a single value decomposition mathematical technique.

37. A method of quickly defining a reference frame in a position measurement system for generating x-y-z data within a measurement field including a plurality of rotatably supported optical transmitters with each transmitter spaced apart from the others in the measurement field and being operatively related through a reference frame within the measurement field to define an intersection between vectors for each transmitter with each transmitter including laser means to generate two rotating substantially fan shaped beams and a strobe means for generating a strobe pulse for each transmitter at a predetermined point in the rotation of each transmitter, said method comprising:

positioning a user-movable receiving instrument at three or more random, undefined locations within said measurement field;

recording data from light detectors on said receiving instrument at each of said locations, said light detectors generating said data in response to illumination by said fan beams and said strobe pulses from said transmitters;

calculating data about a position of said receiving instrument relative to said transmitters based on said recorded data;

calculating data about positions of said transmitters relative to each other based on said data about the position of the receiving instrument at said three or more locations relative to said transmitters; and

establishing a coordinate system for said measurement system based on said data.

38. The method of claim 37, wherein said establishing a coordinate system further comprises arbitrarily designating one of said transmitters as being located at an origin of said coordinate system.

39. The method of claim 38, wherein said establishing a coordinate system further comprises calculating position information for other transmitters in said measurement field relative to said transmitter designated as being at said origin of said coordinate system.

40. The method of claim 39, wherein said establishing a coordinate system further comprises generating two guesses for the value of a solution defining the positions and orientations of all transmitters in said measurement field and using Newton-Raphson iterations to test said guesses.

41. The method of claim 40, wherein two guesses are made based on the following three assumptions:

(a) all transmitters are leveled in an x-y plane of said coordinate system and are at the same height on a z axis of said coordinate system;

(b) Said receiving instrument is vertically oriented at each of said locations where data is collected; and

(c) a center of said receiving instrument is in said x-y plane.

42. The method of claim 40, further comprising comparing solutions produced by testing both of said guesses to minimize error.

43. The method of claim 37, further comprising mapping said coordinate system into a final coordinate system specified by a user.

44. The method of claim 38, wherein said establishing a coordinate system is accomplished with arbitrary scale.