Measurement system for determining six degrees of freedom of an object

• US 20060222314A1
• Filed: 03/27/2006
• Published: 10/05/2006
• Est. Priority Date: 03/29/2005
• Status: Active Grant

• Current Assignee: Leica Geosystems AG (Hexagon AB)
• Original Assignee: Leica Geosystems AG (Hexagon AB)
• Inventors: Dold, Jurgen, Zumbrunn, Roland, Markendorf, Albert, Loser, Raimund
• Granted Patent: US 7,312,862 B2
• Time in Patent Office: Days
• US Class Current: 385/147
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/66 Tracking systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 5/163 Determination of attitude using inertial means G01C9/00; control of attitude G05D1/49

Abstract

A measurement system for determining six degrees of freedom (α, β, d, φ, χ, ψ) of a reflector (2) or of an object (3) on which the reflector is arranged, comprises an angle- and distance measurement apparatus (1), e.g. a laser tracker, operating with a laser beam as a measurement beam (4). The reflector (2) is designed for a parallel reflection of the measurement beam (4) and has an apical opening or surface (6), in a manner such that a part of the measurement beam (4) directed onto the reflector (2), passes through the apical opening or surface (6), and is incident on a light-sensitive surface (7) arranged behind the reflector apex. Five degrees of freedom (α, β, d, φ, χ) of the reflector (2) or the object (3) are computed from measurement data produced by the angle- and distance measurement apparatus (1) and by the light-sensitive surface (7).

Claims

1. A measurement system for determining six degrees of freedom (α

, β

, d, φ

, χ

, ψ

) of a reflector (2) or of an object (3) on which the reflector (2) is arranged, said measurement system comprising;

an angle and distance measurement apparatus (1) emitting a laser beam as a measurement beam (4), the reflector (2) being designed for a parallel reflection of the measurement beam (4) and comprising an apical opening or surface (6);

a light-sensitive surface (7) arranged behind the reflector apex in a manner such that a part of the measurement beam (4) directed onto the reflector (2) passes through the apical opening or surface (6) of the reflector (2) and is incident on the surface (6), which is light sensitive;

an optically detectable addition element (10) which is stationary relative to the reflector (2) and is detected from the angle and distance measurement apparatus (1), or is stationary relative to the angle and distance measurement apparatus (1) and is detected from the object (3), the optically detectable addition element (10) defining a direction (21) or a line which does not lie on a reflector axis (A) nor on the measurement beam (4); and

a computer (8) being equipped for computing five degrees of freedom (α

, β

, d, φ

, χ

) of the reflector (2) or the object (3), from the measurement data produced by the angle and distance measurement apparatus (1) and by the light-sensitive surface (7) and for computing the sixth degree of freedom (ψ

) of the reflector (2) or the object (3) from measurement data obtained by the detection of the addition element (10).

2. A measurement system according to claim 1, wherein the optically detectable addition element (10) is arranged on the object (3), wherein a camera (15) for detecting the addition element is arranged on the angle and distance measurement apparatus (1), and wherein the computer (8) is equipped for computing the sixth degree of freedom from images (20) of the addition element (10) recorded by the camera (15).

3. A measurement system according to claim 2, wherein the addition element (10) comprises two light points (12, 13) or is a light point arrangement which can be reduced to a direction (21) or to a line, or has a two-dimensional shape which can be reduced to a direction (21) or a line.

4. A measurement system according to claim 3, wherein one of the two light points (13, 14) is the reflector (2).

5. A measurement system according to claim 1, wherein the optically detectable addition element (10) is arranged on the angle and distance measurement apparatus (1), wherein the addition element is detectable by the light-sensitive surface (7) arranged behind the reflector apex, and wherein the computer (8) is equipped for computing the sixth degree of freedom (ψ

) from coordinates of image points produced by the addition element (10) and the measurement beam (4), said coordinates being determined by the light-sensitive surface.

6. A measurement system according to claim 5, wherein the optically detectable addition element is a light source (30) which beams in a vertical plane in which the measurement beam (4) lies.

7. A measurement system according to claim 1, wherein the optically detectable addition element (10) is arranged on the angle and distance measurement apparatus (1), wherein an additional detection means (11) is provided on the object (3) for the detection of the addition element (10), and wherein the computer (8) is equipped for computing the sixth degree of freedom (ψ

) from measurement data of the additional detection means (11).

8. A measurement system according to claim 7, wherein the addition element (10) is a light source (30) throwing a light line (42) onto the object, and wherein the additional detection means (11) is a ring sensor (40) with an annular row of light-sensitive elements (41).

9. A measurement system according to claim 1, wherein the angle and distance measurement apparatus (1) is a laser tracker.

10. A measurement system according to claim 1, wherein the object (3) is a touch tool or a movable laser scanner and that the computer (8) is equipped for computing the position of a touch point of the touch tool or of a scan point of the laser scanner from the computed six degrees of freedom (α

, β

, d, φ

, χ

, ψ

) of the touch tool or laser scanner.