Computer aided three dimensional positioning sensing system and method

• US 5,137,354 A
• Filed: 08/01/1991
• Issued: 08/11/1992
• Est. Priority Date: 07/18/1990
• Status: Expired due to Fees

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Spectra-Physics Incorporated (MKS Instruments Incorporated)
• Inventors: deVos, Leon B. C., Schouten, Johannes N. Th. M.
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US07/740,649
• Time in Patent Office: 376 Days
• Field of Search: 356/1, 356/152, 356/400, 235/467, 364/449
• US Class Current: 356/141.3
• CPC Class Codes: G01C 15/002 Active optical surveying means optical plumbing G01C15/105
• CPC Class Codes: G01S 17/87 Combinations of systems using electromagnetic waves other than radio waves

Abstract

A position sensing system calculates the X-Y-Z coordinates of a point in space using triangulation and determines the orientation of an object located at that point. The triangulation calculation is based on the coordinates of at least three retroreflective elements spaced apart from each other 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-Z coordinates 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 space, the system comprising:

at least three stationary retroreflective elements spaced apart from each other and stationed at known coordinates, 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 said stationary retroreflective elements during rotation and for receiving said beam of light reflected from said stationary retroreflective elements when said beam illuminates said retroreflective 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,

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

a means for registering a tilt position of one or more reflecting mirrors positioned at said light transmitting and detecting means, and

a means for calculating a zenith angle of said beam based on said mirror position; and

computer means, responsive to said output signal and said means for detecting movement of each of said at least three stationary retroreflective elements past a predetermined point, for computing the coordinates of the position of the point in space and for computing an orientation for said light transmitting and detecting means when said light transmitting and detecting means are positioned at said point.

2. A system for determining the position of a point in space, the system comprising:

at least three stationary retroreflective elements spaced apart from each other and stationed at known coordinates, 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 said stationary retroreflective elements during 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

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 p2 azimuth and zenith means, responsive to reflection of said beam of light from said retroreflective elements, for continuously transmitting angle signals indicative of an azimuth and zenith angle at which said means for receiving said beam of light is positioned with respect to each of said retroreflective elements; and

computer means responsive to said output signal for computing from said known coordinates of said retroreflective elements and from the angular orientation of said beam when said beam illuminates said retroreflective elements, the coordinates of the position of the point in space.

3. A system for determining the position of a point in space, the system comprising:

at least three stationary retroreflective elements spaced apart from each other and stationed at known coordinates, 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 said stationary retroreflective elements during 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 stationary 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 detecting means, wherein said light transmitting and detecting means include said member rotating with said beam,

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

means for registering a tilt position of one or more reflecting mirrors positioned at said light transmitting and detecting means, and

means for calculating a zenith angle of said beam based on said mirror position; 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 space.

4. A method for determining the position of a point in space, the method comprising the steps of:

locating at least three stationary retroreflective elements spaced apart from each other and stationed at known coordinates, said retroreflective elements capable of reflecting light back toward a light source;

transmitting a rotating beam of light to illuminate said stationary retroreflective elements during rotation;

measuring an angular position of said retroreflective elements with respect to a known reference;

tracking scan behavior, said step of tracking scan behavior including 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,

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

registering a tilt position of one or more reflecting mirrors positioned at the point in space, and calculating a zenith angle of said beam based on said mirror position;

using said scan behavior to calculate angular measurements; and

determining the position of the point based on said angular measurements and said coordinates of said retroreflective elements.

5. A system for determining the X-Y-Z position coordinates of a point in three dimensional space, said system comprising:

first, second and third stationary retroreflective elements spaced apart from one another and positioned at known coordinates in said three dimensional space, each of said first and second retroreflective elements including reflector means for reflecting a beam of light back toward a light source, and said third retroreflective element including indicating means for reflecting light back toward said light source for uniquely identifying said third retroreflective element and for providing an indication of the position at which said beam of light impinges upon said third retroreflective element;

light transmitting and detecting means, located at said point, for generating a beam of light rotated at a zenith angle from vertical to illuminate said reflector means on each of said first and second retroreflective elements and said indicating means on said third retroreflective element;

said light transmitting and detecting means further detecting light reflected from said reflector means on each of said first and second retroreflective elements and from said indicating means on said third retroreflective element, generating output signals indicative of said reflected light from said reflector means on each of said first and second retroreflective elements and from said indicating means on said third retroreflective element, and generating angle signals indicative of said zenith angle from vertical of said rotating beam of light; and

means for computing the X-Y-Z coordinates of said point in said three dimensional space from said known coordinates of said retroreflective elements, said output signals indicative of said reflected light from said reflector means on each of said first and second retroreflective elements and from said indicating means on said third retroreflective element and said angle signals indicative of said zenith angle from vertical of said rotating beam of light.

6. A system for determining the position of a point as claimed in claim 5 wherein said computing 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.

7. A system for determining the X-Y-Z position coordinates of a point in three dimensional space as set forth in claim 5, wherein said reflector means on each of said first and second retroreflective elements comprises indicating means for reflecting light back toward said light source for uniquely identifying each of said first and second retroreflective elements and for providing an indication of the position at which said beam of light impinges upon each of said first and second retroreflective elements.

8. A system for determining the X-Y-Z position coordinates of a point as claimed in claim 7 wherein said indicator means on each of said first, second and third retroreflective elements comprises a distinctive combination of a retroreflective slant target and a retroreflective bar code.

9. A system for determining the X-Y-Z position coordinates of a point in three dimensional space as set forth in claim 5, wherein said light transmitting and detecting means includes means for varying said zenith angle from vertical of said rotating beam of light.

10. A method for determining the X-Y-Z position coordinates of a point in three dimensional space, said method comprising:

providing first, second and third stationary retroreflective elements spaced apart from one another and stationed at known coordinates in said three dimensional space, each of said first and second retroreflective elements including reflector means for reflecting a beam of light back toward a light source, and said third retroreflective element including indicating means for reflecting light back toward said light source for uniquely identifying said third retroreflective element and for providing an indication of the position at which said beam of light impinges upon said third retroreflective element;

projecting from said point a beam of light rotated at a zenith angle from vertical to illuminate said reflector means on each of said first and second retroreflective elements and said indicating means on said third retroreflective element;

detecting at said point light reflected from said reflector means on each of said first and second retroreflective elements and from said indicating means on said third retroreflective element;

generating output signals indicative of said detected reflected light from said reflector means on each of said first and second retroreflective elements and from said indicating means on said third retroreflective element;

generating angle signals indicative of said zenith angle from vertical of said rotating beam of light; and

determining the X-Y-Z coordinates of said point in said three dimensional space from said known coordinates of said retroreflective elements, said output signals indicative of said reflected light from said reflector means on each of said first and second retroreflective elements and from said indicating means on said third retroreflective element and said angle signals indicative of said zenith angle from vertical of said rotating beam of light.

11. A method for determining the X-Y-Z position coordinates of a point in three dimensional space as set forth in claim 10, wherein said reflector means on each of said first and second retroreflective elements comprises indicating means for reflecting light back toward said light source for uniquely identifying each of said first and second retroreflective elements and for providing an indication of the position at which said beam of light strikes upon each of said first and second retroreflective elements.