Self calibrating contour measuring system using fringe counting interferometers

• US 4,457,625 A
• Filed: 07/13/1981
• Issued: 07/03/1984
• Est. Priority Date: 07/13/1981
• Status: Expired due to Term

• Current Assignee: Goodrich Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: ITEQ Corporation
• Inventors: Watson, John T., Greenleaf, Allen H.
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): Koren, Matthew W.
• Application Number:
  US06/282,552
• Time in Patent Office: 1,086 Days
• Field of Search: 356/1, 356/4, 356/4.5, 356/5, 356/345, 356/358, 356/359, 356/360, 356/363, 356/375, 356/376, 356/377, 356/371
• US Class Current: 356/511
• CPC Class Codes: G01B 11/245 using a plurality of fixed, simultaneously operating transducers G01B11/2408 - G01B11/2425, G01B11/255 take precedence

Abstract

A measuring arrangement is disclosed for measuring the contour of a two or three dimensional surface in which a redundant configuration of distance measuring systems is positioned above the surface being measured. Each distance measuring system monitors distance measurements to a point proximate the surface as the measuring point is moved across the surface. The distance measurements are taken from a sufficient number of points on the surface such that a sufficient quantity of data is obtained to define the system geometry and also to define the position of each measurement point. The data is transformed by recognized mathematical techniques into the coordinate positions of all of the measured points on the surface.

In one embodiment for measuring the contour of a three dimensional surface, a tetrahedral arrangement of four distance measuring interferometers includes three interferometers positioned in a planar array above the measured surface and a fourth interferometer positioned at a central apex thereof. A retroreflector is placed adjacent to the measured surface to define the measuring point, and is selectively movable across the measured surface. A tetrahedral truss is positioned above the measured surface, and each interferometer has a beam steering head at one corner of the truss to aim the interferometer beam at the retroreflector during movements thereof. Each interferometer further includes a servo control system for controlling the beam steering head to maintain the interferometer beam aimed at the retroreflector.

Claims

1. A system for measuring the contour of a three dimensional surface, comprising an arrangement of at least four distance measuring systems positioned in a polyhedral configuration above a surface to be measured, with each measuring system providing distance measurements to a measuring point proximate the surface as the measuring point is moved across the contour of the surface, to provide a sufficient quantity of measurement data to define the system geometry and the contour of the three dimensional surface, each distance measuring system including a differential distance measuring system utilizing an interferometer, said polyhedral configuration including a tetrahedral configuration of three interferometers positioned in a planar array above the measured surface and a fourth interferometer positioned at a central apex of the tetrahedral configuration,

and further including a tetrahedral truss positioned above the measured surface, each interferometer having a beam steering head at one corner of the truss to aim an interferometer beam at the measuring point during movements thereof across the contour of the surface.

3. A system for measuring the contour of a three dimensional surface as claimed in claim 1 or 2, each interferometer including a servocontrol system controlling the beam steering head to aim an interferometer beam at the measured point during movements thereof across the contour of the surface.

2. A system for measuring the contour of a three dimensional surface, comprising an arrangement of at least four distance measuring systems positioned in a polyhedral configuration above a surface to be measured, with each measuring system providing distance measurements to a measuring point proximate the surface as the measuring point is moved across the contour of the surface, to provide a sufficient quantity of measurement data to define the system geometry and the contour of three dimensional surface, each distance measuring system including a differential distance measuring system utilizing an interferometer and each interferometer having a beam steering head for directing an interferometer beam at the measured point during movements thereof across the contour of the surface.

4. A system for measuring the contour of a two dimensional surface, comprising an arrangement of at least three distance measuring systems positioned in a polygonal configuration above a two dimensional surface the contour of which is being measured, with each measuring system providing distance measurements to a measuring point proximate the surface as the measuring point is moved along the contour thereof, to provide a sufficient quantity of measurement data to define the system geometry and the contour of the surface, each of said at least three distance measuring systems including a differential distance measuring system utilizing an interferometer, and including a retroreflector adjacent the surface defining the measuring point and being selectively movable across the contour of the surface, each interferometer having a beam steering head for directing an interferometer beam at the measured point during movements thereof across the surface.

5. A system for measuring the contour of a two dimensional surface, comprising an arrangement of at least three distance measuring systems positioned in a polygonal configuration above a two dimensional surface the contour of which is being measured, with each measuring system providing distance measurements to a measuring point proximate the surface as the measuring point is moved along the contour thereof, to provide a sufficient quantity of measurement data to define the system geometry and the contour of the surface, each of said at least three distance measuring systems including a differential distance measuring system utilizing an interferometer, and

including a retroreflector adjacent the surface defining the measuring point and being selectively movable across the contour of the surface, together with a single laser source for providing laser beams for all of the interferometers, each interferometer having a beam steering head for directing an interferometer beam at the measured point during movements thereof across the surface.

6. A system for measuring the contour of a two dimensional surface as claimed in claim 5, each interferometer including a servocontrol system controlling the beam steering head to aim an interferometer beam at the measured point during movements thereof across the surface.