Method and apparatus for the contact-less measuring of objects

• US 4,660,970 A
• Filed: 10/15/1984
• Issued: 04/28/1987
• Est. Priority Date: 11/25/1983
• Status: Expired due to Fees

• Current Assignee: Carl-Zeiss-Stiftung
• Original Assignee: Carl-Zeiss-Stiftung
• Inventors: Ferrano, Gert
• Primary Examiner(s): Hix, L. T.
• Assistant Examiner(s): Rutledge, D.
• Application Number:
  US06/661,297
• Time in Patent Office: 925 Days
• Field of Search: 356/1, 356/4, 356/376, 356/394, 356/398, 356/375, 250/224
• US Class Current: 356/3.03
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures
• CPC Class Codes: G01B 11/26 for measuring angles or tapers; for testing the alignment of axes
• CPC Class Codes: G01S 17/48 Active triangulation systems, i.e. using the transmission and reflection of electromagnetic waves other than radio waves

Abstract

The invention concerns a method for the optical sensing of workpieces in accordance with the principle of triangulation in which a light spot is projected at an angle onto the object to be measured (13) and the distance from the object (13) is determined from the displacement of the image of the light spot as measured with a position-sensitive detector (10).

In addition, the shape or the area of the light spot is measured by means of an image analysis instrument (3) and the inclination of the surface of the object to the direction of observation is determined therefrom in order to increase the accuracy of the distance determination.

Claims

1. Apparatus for contactless measurement of distance to the surface of an object, said apparatus comprising:

(a) a light projector for producing a collimated bundle of light along a projection axis to a surface portion of the object, whereby to produce a single light spot on the surface of the object;

(b) an imaging optical system on an imaging optical axis which is inclined to the projection axis, for imaging the single light spot in an image plane;

(c) a position-sensitive detector at the image plane of said imaging optical system; and

(d) image-analysis means connected to process output signals of said detector for determining the lateral offset of the light-spot image with respect to a predetermined reference position of the imaged spot, said image-analysis means including means for area-evaluation of the imaged spot, whereby to determine local inclination of the object surface.

2. Apparatus according to claim 1, characterized by the fact that the detector is a television-tube camera or a two-dimensional CCD camera.

3. Apparatus according to claim 2, characterized by the fact that the projector and the imaging optical system and the camera are combined into a signal structural unit, with the projection axis intersecting the imaging optical axis, thereby defining a single geometric plane.

4. Apparatus according to claim 3, characterized by the fact that said structural unit can be displaced in several coordinate directions and is mounted for selective adjustment of angular orientation about at least one axis (16).

5. Apparatus according to claim 4, characterized by detents for defined setting of the adjusted angle of the structural unit.

6. Apparatus according to claim 3, in which said projector is one of only two like but angularly spaced projectors combined in said structural unit, with the projection axis of the second projector intersecting the imaging optical axis at the same point as the point of intersection by said first-mentioned projection axis, thereby defining a second geometric plane with the imaging-optical axis, said planes being mutually perpendicular.

7. Apparatus according to claim 6, including means for sequencing the operation of said projectors in timed interlace, said means having synchronizing connection to said imaging-analysis means.

8. The contactless method of using a position-sensitive detector to measure distance to the surface of an object, which method comprises:

(a) projecting a single collimated bundle of light along a projection axis to a surface portion of the object, thereby producing a light spot on the surface of the object, whereby the sectional area of the bundle is substantially independent of object distance;

(b) optically imaging the light spot at the position-sensitive detector on an imaging axis which is inclined with respect to the projection axis;

(c) determining distance to the object surface by measuring the lateral offset of the image of the light spot from a predetermined point at the position-sensitive detector;

(d) measuring the area of the image of the light spot; and

(e) determining the angle of inclination between said surface portion and the imaging axis by comparing the area of the lightspot image with a predetermined reference value.

9. The method of claim 8, in which the collimated bundle is of circular cross-section.

10. The method of claim 8, in which step (c) is performed by television-image analysis.