Computer aided positioning system and method

• US 5,076,690 A
• Filed: 05/14/1990
• Issued: 12/31/1991
• Est. Priority Date: 05/14/1990
• Status: Expired due to Fees

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Spectra Physics LaserPlane Inc (Trimble Inc.)
• Inventors: Schouten, Johannes N. T. M., deVos, Leon B. C.
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US07/522,745
• Time in Patent Office: 596 Days
• Field of Search: 356/51, 356/152, 356/400, 350/6.5, 350/6.9, 235/467, 364/449
• US Class Current: 356/141.1
• CPC Class Codes: G01C 15/002 Active optical surveying means optical plumbing G01C15/105

Abstract

A position sensing system calculates the X-Y coordinates of a point using triangulation and determines the direction in which the point is moving. The triangulation calculation is based on the coordinates of at least three retroreflective elements spaced apart from each other around the periphery of a two-dimensional coordinate frame, and the measured angles between the lines projected radially outward from the point to each of the retroreflective elements. The accuracy of the measured angles is achieved by using a rotating member supported by dedicated hardware and controlled by software. The member rotates with a beam of light generated by a light transmitting and detecting device positionable at the point. The light transmitting and detecting device receives the beam of light reflected back from the retroreflective elements and generates an output signal in response thereto. A computer processes the output signals for use in calculating the X-Y position of the point and the orientation of the light transmitting and detecting device when it is positioned at the point.

Claims

1. A system for determining the position of a point in a two-dimensional coordinate frame of reference, the system comprising:

at least three stationary retroreflective elements spaced apart from one another and stationed at known coordinates in the two-dimensional coordinate frame, each of said retroreflective elements including identification means thereon for reflecting light back toward a light source, said reflected light from each of said elements including information generated by said identification means for uniquely identifying each of said elements;

light transmitting and detecting means, positionable at the point, for generating a rotating beam of light to illuminate said identification means on each of said stationary retroreflective elements during each rotation, and for detecting said reflected light from said identification means on each of said elements and generating an output signal in response thereto;

angle determining means for detecting the angular orientation of said reflected light when said reflected light is detected by said transmitting and detecting means; and

computer means for computing from said known coordinates of said retroreflective elements, the angular orientation of said reflected light detected by said angle determining means, and said output signal generated in response to said reflected light from said identification means on each of said elements, the coordinates of the position of the point in the two-dimensional coordinate frame of reference.

2. A system for determining the position of a point as claimed in claim 1 wherein said light transmitting and detecting means comprises:

means for generating a beam of light;

means for projecting said beam of light at a substantially constant rotating angular velocity toward said retroreflective elements;

means for receiving said beam of light reflected from said retroreflective elements corresponding to said illumination of each of said retroreflective elements during each rotation of said beam; and

azimuth means, responsive to reflection of said beam of light from said retroreflective elements, for continuously transmitting angle signals indicative of an azimuth angle at which said means for receiving said beam of light is positioned with respect to each of said retroreflective elements.

3. A system for determining the position of a point as claimed in claim 1 wherein said computer means are capable of determining an orientation of said light transmitting and detecting means when said light transmitting and detecting means are positioned at the point.

4. A system for determining the position of a point as claimed in claim 1 wherein said identification means on each of said at least three stationary retroreflective elements is a distinctive retroreflective bar code.

5. A system for determining the position of a point in a two-dimensional coordinate frame of reference, the system comprising:

at least three stationary retroreflective elements spaced apart from one another and stationed at known coordinates in the two-dimensional coordinate frame, each of said retroreflective elements including identification means thereon for reflecting light back toward a light source, said reflected light from each of said elements including information generated by said identification means for uniquely identifying each of said elements;

light transmitting and detecting means, positionable at the point, for generating a rotating beam of light to illuminate said identification means on each of said stationary retroreflective elements during each rotation, and for detecting said reflected light from said identification means on each of said elements and generating an output signal in response thereto, said light transmitting and detecting means including

a member rotating with said beam, said member having a periphery and further having a plurality of angularly positioned elements spaced around said periphery which divide a revolution of said member into a plurality of generally equal partial revolutions, and

a means for detecting movement of each of said elements past a predetermined point as said member rotates; and

computer means, responsive to said output signal generated in response to said reflected light from said identification means on each of said elements and said means for detecting movement of each of said elements past a predetermined point, for computing the coordinates of the position of the point in the two-dimensional coordinate frame of reference.

6. A system for determining the position of a point as claimed in claim 5 further comprising a calibrating system for calibrating said light transmitting and detecting means.

7. A system for determining the position of a point as claimed in claim 6 wherein said calibrating system comprises:

a device having an angularly positioned surface for arbitrarily positioning said light transmitting and detecting means, wherein said light transmitting and detecting means include said member rotating with said beam; and

means for measuring a distance between a first said angularly positioned element and an adjacent second said angularly positioned element.

8. A system for determining the position of a point as claimed in claim 5 wherein said plurality of angularly positioned elements comprise a plurality of apertures.

9. A system for determining the position of a point as claimed in claim 5 wherein said means for detecting movement of each of said elements comprises a light source paired with a photodetector element.

10. A system for determining the position of a point in a two-dimensional coordinate frame of reference, the system comprising:

at least three stationary retroreflective elements spaced apart from one another and stationed at known coordinates in the two-dimensional coordinate frame, each of said retroreflective elements including identification means thereon for reflecting light back toward a light source, said reflected light from each of said elements including information generated by said identification means for uniquely identifying each of said elements;

light transmitting and detecting means positionable at the point for generating a rotating beam of light to illuminate said identification means on each of said stationary retroreflective elements during each rotation and for receiving said reflected light from said identification means on each of said elements, said light transmitting and detecting means including

an optical member rotating with said beam, said member having a periphery and further having a plurality of apertures located at said periphery which divide a revolution of said member into a plurality of generally equal partial revolutions, and

a means for registering a time differential between each adjacent pair of said plurality of apertures as said member rotates; and

computer means, responsive to said output signal generated in response to said reflected light from said identification means on each of said elements and said means for registering a time differential between each pair of said plurality of apertures, for computing the coordinates of the position of the point in the two-dimensional coordinate frame of reference and for computing an orientation for said light transmitting and detecting means when said light transmitting and detecting means are positioned at said point.

11. A method for determining the position of a point in a two-dimensional coordinate frame of reference, the method comprising the steps of:

locating at least three stationary retroreflective elements spaced apart from one another and stationed at known coordinates in the two-dimensional coordinate frame, each of said retroreflective elements including identification means thereon for reflecting light back toward a light source, said reflected light from each of said elements including information generated by said identification means for uniquely identifying each of said elements;

transmitting a rotating beam of light in a plane to illuminate said identification means on each of said stationary retroreflective elements during each rotation of said beam of light;

measuring said rotation of said beam of light between successively illuminated retroreflective elements when said beam of light illuminates each of said retroreflective elements;

using said rotation of said beam of light to calculate angular measurments between each of said retroreflective elements; and

determining the position of the point based on said angular measurements, said information generated by said identification means for uniquely identifying each of said retroreflective elements, and said coordinates of said retroreflective elements.

12. A method for determining the position of a point as claimed in claim 11 wherein said step of tracking behavior of a rotation further includes the steps of:

mounting a member on a rotating shaft, said member having a periphery and further having a plurality of apertures located at said periphery which divide a revolution of said member into a plurality of generally equal partial revolutions; and

registering a time differential between each adjacent pair of said plurality of apertures as said member rotates.

13. A method for determining the position of a point as claimed in claim 11 wherein said step of determining the position of the point further includes the step of determining an orientation for said rotating beam of light when said rotating beam of light is positioned at the point.

14. A method for determining the position of a point as claimed in claim 12 further including the step of interpolating between corresponding angle measurements between said each adjacent pair of said plurality of apertures to determine exact angles between each of said adjacent pair of said plurality of apertures.

15. A system for determining the position of a point in a two-dimensional coordinate frame of reference, the system comprising:

at least three stationary retroreflective elements spaced apart from each other and stationed at known coordinates in the two-dimensional coordinate frame, said retroreflective elements capable of reflecting light back toward a light source;

light transmitting and detecting means, positionable at the point, for generating a rotating beam of light to illuminate each of said stationary retroreflective elements during each rotation, and for detecting said beam of light when it is reflected from said stationary retroreflective elements and generating an output signal in response thereto, said light transmitting and detecting means including

a member rotating with said beam, said member having a periphery and further having a plurality of angularly positioned elements spaced around said periphery which divide a revolution of said member into a plurality of generally equal partial revolutions, and

a means for detecting movement of each of said at least three retroreflective elements past a predetermined point as said member rotates;

a calibrating system for calibrating said light transmitting and detecting means, said calibrating system including

a device having an angularly positioned surface for arbitrarily positioning said light transmitting and detection means, wherein said light transmitting and detecting means include said member rotating with said beam; and

means for measuring a distance between a first said angularly positioned element and an adjacent second said angularly positioned element; and

computer means, responsive to said output signal and said means for detecting movement of each of said elements past a predetermined point, for computing the coordinates of the position of the point in the two-dimensional coordinate frame of reference.