Systems and methods for illuminating objects for vision systems

• US 4,706,168 A
• Filed: 11/15/1985
• Issued: 11/10/1987
• Est. Priority Date: 11/15/1985
• Status: Expired due to Term

• Current Assignee: GSI Lumonics Corporation (Novanta Inc.)
• Original Assignee: View Engineering, Inc. (Quality Vision International, Inc.)
• Inventors: Weisner, Ralph M.
• Primary Examiner(s): Feinberg, Craig R.
• Assistant Examiner(s): Okonsky, David A.
• Application Number:
  US06/798,632
• Time in Patent Office: 725 Days
• Field of Search: 356/1, 356/376, 362/5, 362/18, 362/32, 362/33, 362/84, 362/216, 362/284, 362/283, 362/302, 362/303, 362/304, 362/285, 362/289, 362/419, 362/277
• US Class Current: 362/18
• CPC Class Codes: G01B 11/00 Measuring arrangements characterised by the use of optical techniques

Abstract

An illumination system, particularly suitable for use with automatic vision systems employing an image sensing device or system, illuminates an object under analysis with the cone of light that may cover 360° or only an arc segment about a part of the object under analysis. Light from a ring source is directed toward a curved parabolic surface on a light collector ring that substantially collimates the light and fans it out radially out toward a toroidal reflector surface on an encompassing ring, the relative position of which determines the angle of incidence of a cone of light formed to fall in the region of the object, so as to illuminate particular features with optimal efficiency. To change the angle of incidence while maintaining focus, a differential drive mechanism moves the parabolic collector ring and the toroidal angle generator ring in differential fashion concurrently.

Claims

1. A system for illuminating a target object with focused light at varying angles of incidence relative to an optical axis and comprising:

a ring light source concentric with the optical axis and providing a hollow cylinder of light directed toward the object;

a first ring reflector having an outer surface of parabolic cross section in a path of the cylinder of light and reflecting the light into an outwardly disbursing pattern;

a second ring reflector having an inner surface of curved cross section disposed about the first ring reflector and concentric therewith in a path of the pattern reflected from the first ring reflector; and

means for varying the spacing of the first and second ring reflector from the object, including means for moving the second ring reflector differentially relative to the first.

2. The invention as set forth in claim 1 above, wherein the ring light source comprises a ring of fiber optic elements arranged in arc segments, and the system further includes means for separately energizing the arc segments of the ring.

3. The invention as set forth in claim 1 above, wherein the means for varying the spacing of the ring reflectors from the object comprises a pair of spaced apart racks having opposed teeth of different pitches, intercoupled gears disposed between the racks and engaging the teeth thereof, and motor means for driving the gears to provide differential movement of the racks, each rack being coupled to a different ring reflector.

4. The invention as set forth in claim 1 above, wherein the system further comprises an image camera directed along the optical axis and toward the object, and concentric with the rig light source and ring reflectors.

5. A method of examining an object with a vision system having an optical axis to enhance automatic recognition of distinctive features to be measured or identified automatically comprising the steps of:

illuminating an object with a conical sheath of light concentric with the axis of the vision system and focused on a selected point relative to the object to be analyzed; and

changing an angle of incidence of the conical sheath of light while maintaining it in focus at the selected point.

6. A method as set forth in claim 5 above, further comprising the steps of changing a selected region of the object to be analyzed, and concurrently changing the angle of incidence and a focal position of the conical sheath of light for best illumination.

7. An illumination system for use with a viewing system for inspecting, measuring or recording an image of an object at an optical axis, comprising:

means providing a hollow cylindrical illuminating light pattern concentric with the optical axis and directed toward the object;

a first ring element having a curved reflecting surface concentric with the optical axis and reflecting the cylindrical light in a first direction, a second ring element having a curved reflecting surface in a path of the light reflected from the first curved reflecting surface and reflecting the light into a conical illumination pattern; and

means coupled to move the first and second ring elements along the optical axis with differential motion.

8. The invention as set forth in claim 7 above, wherein the reflecting surface of the first ring element has a paraboloidal curvature and the reflecting surface of the second ring element has a substantially circular curvature.

9. The invention as set forth in claim 8 above, wherein the means for moving the first and second ring elements along the optical axis comprises means for moving the second ring element at a rate which is greater than the movement of the first element, whereby the light reflected from the reflecting surface of the second ring element varies in angle of incidence but the focal point of the conical illumination pattern remains the same.

10. The invention as set forth in claim 9 above, wherein the means providing a light pattern comprises a plurality of optical fibers arranged in a circular pattern concentric with the optical axis and having their ends along parallel lines.

11. The invention as set forth in claim 9 above, wherein the reflecting surface of the first ring element is at a smaller diameter than the reflecting surface of the second ring element and wherein the means for moving the ring elements comprises a pair of parallel racks having facing teeth of different pitches and drive gear means disposed between the racks and engaging the teeth, and drive motor means coupled to the drive gear means.

12. A light system for providing light at variable angles of incidence on an object to be viewed at a focal plane along a viewing axis perpendicular to the viewing axis, comprising:

a first body in the form of a surface of revolution concentric with the viewing axis and having an outer reflecting flange on a side opposite the focal plane, the reflecting flange defining a first reflecting surface that is parabolic in cross section;

means disposed about the first body and providing a circular light source concentric with and directed onto the first reflecting surface, the light from the source diverging within a beam angle and the focal point of the first reflecting surface being selected to collimate light from the source;

a second body in the form of a surface of revolution concentric with the viewing axis and having an inner reflecting flange on a side facing the focal plane, the reflecting flange defining a second reflecting surface that approximates a circular arc in cross section and reflects light inwardly toward the viewing axis;

means coupled to the first and second bodies for moving such bodies along the viewing axis in a selected displacement ratio such that the light reflected from the second surface focuses at the focal plane.

13. A system as set forth in claim 12 above, wherein the first reflecting surface forms an outwardly directed sheet of light and the second reflecting surface is disposed outside the first reflecting surface.

14. A system as set forth in claim 13 above, wherein the light source comprises a plurality of optical fibers having fiber ends disposed in parallel to define a cylinder concentric about and parallel to the viewing axis.

15. A system as set forth in claim 14 above, wherein the light source further comprises means for energizing sets of the optical fibers to provide illumination of the object from different directions as well as from all directions about the object.

16. A vision system comprising:

a stable base having a horizontal upper surface;

a stable bridge spanning the upper surface in an X axis direction and overlying a viewing zone on the base;

platform means on the upper surface of the base for receiving an object to be viewed, the platform means including Y axis drive means for providing horizontal movement in the Y direction;

X axis carriage means mounted on the bridge and including X axis drive means for providing horizontal movement in the X direction;

Z axis carriage means mounted on the X axis carriage means and including drive means for providing vertical movement;

electronic camera means, including magnification means, mounted on the Z axis carriage means and oriented along an optical axis to view the viewing zone;

illuminator means disposed concentrically about the electronic camera means and the optical axis for providing a cone of light on the object to be viewed, the illuminator means comprising a pair of ring reflectors; and

illuminator drive means mounted on the Z axis carriage means and coupled to the illuminator means for moving the ring reflectors in a selected displacement ratio to maintain the cone of light in focus at different angles of incidence.

17. The invention as set forth in claim 16 above, wherein the system includes processor means coupled to control the X axis drive, Y axis drive, Z axis drive and illuminator drive means in a selected sequence of positions to focus the camera means on selected positions on the object and to concurrently illuminate the object with light at preferred angles of incidence.

18. The invention as set forth in claim 17 above, wherein the illuminator means comprises light source means providing a concentric light pattern about the viewing axis, and wherein the ring reflectors comprise a first, inner, reflector ring having a parabolic reflecting surface and a second, outer reflector ring having a generally circular reflecting surface, the parabolic reflecting surface collecting and collimating light from the concentric light pattern and the circular reflecting surface and its displacement along the optical axis relative to the parabolic reflecting surface establishing the angle of incidence of light directed toward the object.