Vision metrology system

• US 4,825,394 A
• Filed: 05/07/1985
• Issued: 04/25/1989
• Est. Priority Date: 05/07/1985
• Status: Expired due to Fees

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: General Dynamics Corporation
• Inventors: Foster, H. Dell, Beamish, Jerald K.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/731,916
• Time in Patent Office: 1,449 Days
• Field of Search: 364/559, 364/560, 364/571, 364/525, 354/400-409, 354/286, 354/288, 350/359-363, 350/423, 350/424, 356/237, 356/388, 356/389, 356/390, 356/379, 356/384, 356/147
• US Class Current: 356/147
• CPC Class Codes: B25J 9/1697 Vision controlled systems
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates
• CPC Class Codes: G01B 21/04 by measuring coordinates of points
• CPC Class Codes: G05B 19/25 for continuous-path control
• CPC Class Codes: G05B 2219/39008 Fixed camera detects reference pattern held by end effector
• CPC Class Codes: G05B 2219/39013 Locate movable manipulator relative to object, compare to stored gridpoints
• CPC Class Codes: G05B 2219/39057 Hand eye calibration, eye, camera on hand, end effector

Abstract

The system has one or more vision units each of which has a head with a primary prism, a primary objective lens, and zoom optics including a plurality of lenses which form an optical path through which the image of an object may pass onto an area array sensor. Also provided is a reseau plate having a plurality of reseaus formed in a given pattern and a light source for projecting the image of the reseaus through the optical path onto the sensor for use for correcting in real time, optical distortion of the image of the object passing through the optical path including the lenses of the zoom optics. The unit is capable of movement about two perpendicular axis. Servo control devices operated by a computer are employed for automatically adjusting the focus, aperture, magnification, axial position of the reseau plate in consonance with the focus adjustment, and movement of the head about its two axes. The system also contains a central control processing head and a manual controller for the vision units.

Claims

1. A vision head for a vision metrology

system, comprising:

a primary prism,

a primary objective lens,

zoom optics means comprising a plurality of lenses

a sensor,

said primary prism, primary objective lens, and said zoom optics means comprising an optical path through which an image of an object may pass onto said sensor,

said primary prism comprising structure positioned to allow light to pass therethrough by way of a first path which coincides with said optical path and by way of a second path having an initial portion which is different from said first path and which intercepts said first path and then merges with said first path,

a reseau pattern means having a plurality of reseaus formed in a given pattern,

light means for projecting an image of said reseaus through said primary prism onto said sensor by way of said second path for use for correcting in real-time, optical distortion of the image of the object passing through said plurality of lenses of said zoom optics means.

2. The vision head of claim 1, comprising:

reseau optical lens means, and

means for directing light, passing through said reseau pattern means, to said reseau optical lens means for passage therethrough to said primary prism and then to said sensor by way of primary objective lens and said zoom optics means.

3. The vision head of claim 2, comprising:

a laser for projecting a primary beam of light,

a beam splitter for dividing said primary beam of light into a pointer beam and into a range-finder beam,

a reflecting surface in said primary prism,

said optical path having an optical axis,

said pointer beam being reflected by said beam splitter to said reflecting surface,

said reflecting surface being positioned to reflect said pointer beam forward and cocident with the optical axis of said optical path,

optical means for directing said range-finder beam in a direction to intercept said pointer beam at a given distance forward of said primary prism,

a shutter for controlling said pointer beam, and

a shutter for controlling said range-finder beam.

4. The vision head of claim 1, comprising:

a laser for projecting a primary beam of light,

a beam splitter for dividing said primary beam of light into a pointer beam and into a range-finder beam,

a reflecting surface in said primary prism,

said optical path having an optical axis,

said pointer beam being reflected by said beam splitter to said reflecting surface,

said reflecting surface being positioned to reflect said pointer beam forward an coincident with the optical axis of said optical path,

optical means for directing said range-finder beam in a direction to intercept said pointer beam at a given distance forward of said primary prism,

a shutter for controlling said pointer beam, and

a shutter for controlling said range-finder beam.

5. The vision head of claim 1, comprising:

said primary objective lens being adjustable in position along said optical path relative to said sensor,

primary objective lens adjusting means for adjusting the position of said primary objective lens along said optical path relative to said sensor,

said plurality of lenses of said zoom optics means having an adjustable magnification,

zoom optics adjusting means for adjusting the magnification of said plurality of lenses of said zoom optics means,

said reseau pattern means being adjustable in position along said initial portion of said second path,

reseau pattern adjusting means for adjusting the position of said reseau pattern means along said initial portion of said second path corresponding with the adjustment of said primary objective lens along said optical path,

aperture means located in said optical path for allowing light to pass along said optical path to said sensor,

said aperture means having an aperture with an adjustable size for controlling the passage of light therethrough, and

aperture adjusting means for controlling said aperture means for adjusting the size of said aperture.

6. A vision unit, including the vision head of claim 5, and comprising:

mount means for mounting said vision head for movement about a first axis and a second axis perpendicular to said first axis,

first head position adjusting means coupled to said mount means for controlling movement of said vision head about said first axis, and

second head position adjusting means coupled to said mount means for controlling movement of said vision head about said second axis.

7. The vision head of claim 5, comprising:

a programmable computer means, and

control means responsive to said programmable computer means for controlling said primary objective lens adjusting means, said zoom optics adjusting means, said reseau pattern adjusting means, and said aperture adjusting means.

8. A vision unit, including the vision head of claim 1, and comprising:

mount means for mounting said vision head for movement about a first axis and a second axis perpendicular to said first axis,

first head position adjusting means coupled to said mount means for controlling movement of said vision head about said first axis, and

second head position adjusting means coupled to said mount means for controlling movement of said vision head about said second axis.

9. The vision unit of claim 8, comprising:

a programmable computer means, and

control means responsive to said programmable computer means for controlling said first and second head position adjusting means.

10. The vision unit of claim 8, comprising:

an optically collimated reference mark on said mount means for allowing precise measurements along said first and second head position axes.

11. The vision unit of claim 8, comprising:

an azimuth servo system and an elevation servo system for controlling movement of said vision head about said first and second axes respectively,

said azimuth servo system comprising;

an azimuth servo motor for rotating said vision head about said first axis,

a control means for producing an azimuth position control signal representative of a desired angular position of said vision head relative to said first axis,

an azimuth low-resolution control counter responsive to said azimuth position control signal for producing an azimuth low-resolution output representative of the desired angular position of said vision head relative to said first axis,

azimuth encoder means for converting the actual angular position of said vision head relative to said first axis to an actual azimuth position signal,

means for transforming said actual azimuth position signal into an azimuth low-resolution feedback signal and an azimuth high-resolution feedback signal,

an azimuth low-resolution feedback counter responsive to said azimuth low-resolution feedback signal for producing an azimuth low-resolution output representative of the actual angular position of said vision head relative to said first axis,

an azimuth control feedback error register for comparing the output of said azimuth lowresolution control counter and the output of said azimuth low-resolution feedback counter for producing an azimuth low-resolution position error output,

an azimuth high-resolution counter responsive to said azimuth high-resolution feedback signal for producing an azimuth high-resolution output representative of the actual angular position of said vision head relative to said first axis,

an azimuth error encoder multiplexer for combining said azimuth low-resolution position error output and the output of said azimuth high-resolution counter to produce an azimuth position error signal,

means for applying said azimuth position error signal to said azimuth servo motor for causing rotation of said vision head about said first axis so as to minimize said azimuth position error signal,

said elevation servo system comprising;

an elevation servo motor for rotating said vision head about said second axis,

an elevation low-resolution control counter responsive to said elevation position control signal for producing an elevation low-resolution output representative of the desired angular position of said vision head relative to said second axis,

elevation encoder means for converting the actual angular position of said vision head relative to said second axis to an actual elevation position signal,

means for transforming said actual elevation position signal into an elevation low-resolution feedback signal and an elevation high-resolution feedback signal,

an elevation low-resolution feedback counter responsive to said elevation low-resolution feedback signal for producing an elevation low-resolution output representative of the actual angular position of said vision head relative to said second axis,

an elevation control feedback error register for comparing the output of said elevation low-resolution control counter and the output of said elevation low-resolution feedback counter for producing an elevation low-resolution position error output,

an elevation high-resolution counter responsive to said elevation high-resolution feedback signal for producing an elevation high-resolution output representative of the actual angular position of said vision head relative to said second axis,

an elevation error encoder multiplexer for combining said elevation low-resolution position error output and the output of said elevation high-resolution counter to produce an elevation position error signal, and

means for applying said elevation position error signal to said elevation servo motor for causing rotation of said vision head about said second axis so as to minimize said elevation position error signal.

12. The vision unit of claim 8, comprising:

said primary objective lens being adjustable in position along said optical path relative to said sensor,

primary objective lens adjusting means for adjusting the position of said primary objective lens along said optical path relative to said sensor,

said plurality of lenses of said zoom optics means having an adjustable magnification,

zoom optics adjusting means for adjusting the magnification of said plurality of lenses of said zoom optics means,

said reseau pattern means being adjustable in position along said initial portion of said second path,

reseau pattern adjusting means for adjusting the position of said reseau pattern means along said initial portion of said second path corresponding with the adjustment of said primary objective lens along said optical path,

aperture means located in said optical path for allowing light to pass along said optical path to said sensor,

said aperture means having an aperture with an adjustable size for controlling the passage of light therethrough,

aperture adjusting means for controlling said aperture means for adjusting the size of said aperture,

a programmable computer means, and

control means responsive to said programmable computer means for controlling said primary objective lens adjusting means, said zoom optics adjusting means, said reseau pattern adjusting means, said aperture adjusting means, and said first and second head position adjusting means.

13. The vision head of claim 1 comprising:

means for storing known coordinates of said reseaus of said predetermined pattern, as they exist prior to passage thereof through said primary prism, and

computer means for determining;

(a) the coordinates of the image reseaus detected by said sensor,

(b) the coordinates of the image of points of interest of the object detected by said sensor,

(c) the distortion-corrected image coordinates of the imaged object points of interest from their detected sensor coordinates by employing coordinates of the imaged reseaus detected by said sensor and said known coordinates of said reseaus.

14. The vision head of claim 1, wherein said plurality of reseaus in said given pattern comprises:

a plurality of reseaus in each of a plurality of radial lines extending outward in a plane from a central point.

15. The vision head of claim 14, wherein:

said reseaus in each line increase in size outward from said central point.

16. The vision head of claim 1, wherein:

the image of the reseaus, upon passage to said sensor, has an axis between said primary prism and said sensor which is the same as said optical axis of said optical path,

the image of the object, upon passage through said optical path to said sensor, has an axis which is the same as said optical axis of said optical path.

17. The vision head of claim 16, wherein:

said sensor comprises an area array sensor having a plurality of pixels in rows and columns.

18. The vision head of claim 1, wherein:

said sensor comprises an area array sensor having a plurality of pixels in rows and columns.

33. The vision head of claim 1, wherein:

said primary objective lens and said zoom optics means are located along said optical path between said primary prism and said sensor.

34. The vision head of claim 33, wherein:

said zoom optics means is located along said optical path between said primary objective lens and said sensor.

35. The vision head of claim 33, wherein:

said sensor comprises an area array sensor having a plurality of pixels in rows and columns.

19. A vision unit, comprising:

a vision head,

said vision head comprising;

a prism,

a primary objective lens,

zoom optics means comprising a plurality of lenses,

a sensor,

said prism, primary objective lens, and said zoom optics means comprising an optical path through which the image of an object may pass onto said sensor,

said primary objective lens and said zoom optics means being located along said optical path between said prism and said sensor,

a reseau pattern means having a plurality of reseaus formed in a given pattern, and

light means for projecting an image of said reseaus to said prism and then through said optical path onto said sensor for use for correcting in real-time, optical distortion of the image of the object passing through said plurality of lenses of said zoom optics means.

mount means for mounting said vision head at a position where two perpendicular axes intersect each other,

said mount means mounting said vision head for rotational movement about each of said two axes at the intersection of said two axes,

a first position adjusting means coupled to said mount means for controlling movement of said vision head about one of said axes,

a second position adjusting means coupled to said mount means for controlling movement of said vision head about the other of said axes, and

control means coupled to first and second position adjusting means for automatically controlling movement of said vision head about said two perpendicular axes.

20. The vision unit of claim 19, wherein:

said vision head comprises aperture means having an aperture for allowing the passage of light therethrough,

said aperture having a size which is adjustable.

21. The vision unit of claim 20, wherein:

said primary objective lens is adjustable in position along said optical path relative to said sensor,

primary objective lens adjusting means for adjusting the position of said primary objective lens along said optical path relative to said sensor.

22. The vision unit of claim 21, wherein:

said plurality of lenses of said zoom optics means have a variable magnification,

means for continuously varying the magnification of said plurality of lenses of said zoom optics means.

23. The vision unit of claim 20, wherein:

said plurality of lenses of said zoom optics means have a variable magnification,

means for continuously varying the magnification of said plurality of lenses of said zoom optics means.

24. The vision unit of claim 19, comprising:

an azimuth servo system and an elevation servo system for controlling movement of said vision head about said first and second axes respectively,

said azimuth servo system comprising;

an azimuth servo motor for rotating said vision head about said first axis,

a control means for producing an azimuth position control signal representative of a desired angular position of said vision head relative to said first axis,

an azimuth low-resolution control counter responsive to said azimuth position control signal for producing an azimuth low-resolution output representative of the desired angular position of said vision head relative to said first axis,

azimuth encoder means for converting the actual angular position of said vision head relative to said first axis to an actual azimuth position signal,

means for transforming said actual azimuth position signal into an azimuth low-resolution feedback signal and an azimuth high-resolution feedback signal,

an azimuth low-resolution feedback counter responsive to said azimuth low-resolution feedback signal for producing an azimuth low-resolution output representative of the actual angular position of said vision head relative to said first axis,

an azimuth control feedback error register for comparing the output of said azimuth low-resolution control counter and the output of said azimuth low-resolution feedback counter for producing an azimuth low-resolution position error output,

an azimuth high-resolution counter responsive to said azimuth high-resolution feedback signal for producing an azimuth high-resolution output representative of the actual angular position of said vision head relative to said first axis,

an azimuth error encoder multiplexer for combining said azimuth low-resolution position error output and the output of said azimuth high resolution counter to produce an azimuth position error signal,

means for applying said azimuth position error signal to said azimuth servo motor for causing rotation of said vision head about said first axis so as to minimize said azimuth position error signal,

said elevation servo system comprising;

an elevation servo motor for rotating said vision head about said second axis,

an elevation low-resolution control counter responsive to said elevation position control signal for producing an elevation low-resolution output representative of the desired angular position of said vision head relative to said second axis,

elevation encoder means for converting the actual angular position of said vision head relative to said second axis to an actual elevation position signal,

means for transforming said actual elevation position signal into an elevation low-resolution feedback signal and an elevation high-resolution feedback signal,

an elevation low-resolution feedback counter responsive to said elevation low-resolution feedback signal for producing an elevation low-resolution output representative of the actual angular position of said vision head relative to said second axis,

an elevation control feedback error register for comparing the output of said elevation low-resolution control counter and the output of said elevation low-resolution feedback counter for producing an elevation low-resolution position error output,

an elevation high-resolution counter responsive to said elevation high-resolution feedback signal for producing an elevation high-resolution output representative of the actual angular position of said vision head relative to said second axis,

an elevation error encoder multiplexer for combining said elevation low-resolution position error output and the output of said elevation high-resolution counter to produce an elevation position error signal, and

means for applying said elevation position error signal to said elevation servo motor for causing rotation of said vision head about said second axis so as to minimize said elevation position error signal.

25. In an optical system comprising a primary prism, a primary objective lens, zoom optics means comprising a plurality of lenses, an area array sensor, light means, and a reseau pattern means comprising a two-dimensional pattern of reseaus wherein said primary prism, said primary objective lens, and said zoom optics means comprise an optical path through which an image of an object may pass onto said sensor, said primary prism comprising structure positioned to allow light to pass therethrough by way of a first path which coincides with said optical path and by way of a second path having an initial portion which is different from said first path and which intercepts said first path and then merges with said first path, said light means and said reseau pattern means being located such that said light means, when actuated, projects an image of said predetermined pattern of said reseaus through said primary prism by way of said second path, a process of obtaining information for correcting in real-time, optical distortion of the image of the object passing through said plurality of lenses of said zoom optics means comprising the steps of:

projecting the image of an object onto said sensor through said optical path and hence through said first path by way of said primary prism, said primary objective lens, and said plurality of said lenses of said zoom optics means, and

actuating said light means to project the image of said predetermined two-dimensional pattern of said reseaus through said second path onto said sensor by way of said primary prism, said primary objective lens, and said plurality of said lenses of said zoom optics means for use for correcting for said distortion.

26. The process of claim 25, wherein:

said predetermined two-dimensional pattern of said reseaus comprises;

a plurality of reseaus in each of a plurality of radial lines extending outward in a plane from a central axis.

27. The process of claim 26, wherein:

said reseaus in each line increase in size outward from said central axis.

28. In an optical system comprising a primary prism, a primary objective lens, zoom optics means comprising a plurality of lenses, and an area array sensor wherein said primary prism, said primary objective lens, and said zoom optic means comprise an optical path through which an image of an object may pass onto said sensor, a process of correcting in real-time, optical distortion of the image of the object passing through said plurality of lenses of said zoom optics means, comprising the steps of:

projecting the image of an object onto said sensor by way of said primary prism, said primary objective lens, and said plurality of said lenses of said zoom optics means,

projecting an image of a predetermined two-dimensional pattern of reseaus onto said sensor by way of said primary prism, said primary objective lens, and said plurality of said lenses of said zoom optics means,

said reseaus of said predetermined pattern, prior to passing through said primary prism, having known coordinates,

determining the coordinates of the image of the reseaus detected by said sensor,

determining the coordinates of the image of points of interest of the object detected by said sensor,

determining distortion-corrected image coordinates of the imaged object points of interest from their detected sensor coordinates by employing coordinates of the imaged reseaus detected by said sensor and said known coordinates of said reseaus.

29. The process of claim 28, wherein:

said predetermined two-dimensional pattern of said reseaus comprises;

a plurality of reseaus in each of a plurality of radial lines extending outward in a plane from a central axis.

30. The process of claim 29, wherein:

said reseaus in each line increase in size outward from said central axis.

31. A measuring system, comprising:

a vision head,

said vision head comprising;

a primary prism,

a primary objective lens,

zoom optics means comprising a plurality lenses, and

an area array sensor,

said primary prism, said primary objective lens, and said zoom optics means comprising a primary optical path through which an image of an object may pass onto said sensor,

a reseau pattern means having a plurality of reseaus formed in a given pattern,

light means for projecting an image of said reseaus through said primary optical path onto said sensor for use for correcting in real-time, optical distortion of the image of the object passing through said plurality of lenses of said zoom optics means,

said primary objective lens being adjustable in position along said primary optical path relative to said sensor,

primary objective lens adjusting means for adjusting the position of said primary objective lens along said primary optical path relative to said sensor,

said plurality of lenses of said zoom optics means having an adjustable magnification,

zoom optics adjusting means for adjusting the magnification of said plurality of lenses of said zoom optics means,

said light means and said reseau pattern means being located such that said light means, when actuated, projects the image of said reseaus along a secondary optical path to said primary prism and then through said primary prism and through said primary optical path onto said sensor,

said reseau pattern means being adjustable in position along said secondary optical path,

reseau pattern adjusting means for adjusting the position of said reseau pattern means along said secondary optical path corresponding with the adjustment of said primary objective lens along said primary optical path,

aperture means located in said primary optical path for allowing light to pass along said primary optical path to said sensor,

said aperture means having an aperture with an adjustable size for controlling the passage of light therethrough,

aperture adjusting means for adjusting the size of said aperture,

mount means for mounting said vision head for movement about a first axis and a second axis perpendicular to said first axis,

first head orientation adjusting means coupled to said mount means for controlling movement of said vision head about said first axis,

second head orientation adjusting means coupled to said mount means for controlling movement of said vision head about said second axis,

an optically collimated reference mark on said mount means for allowing precise measurements along said first and second head position axes,

a programmable computer means, and control means responsive to said programmable computer means for controlling each of said primary objective lens adjusting means, said zoom optics adjusting means, said reseau pattern adjusting means, said aperture adjusting means, and said first and second head orientation adjusting means.

32. A servo system for controlling movement of a device about an axis, comprising:

a servo motor for rotating said device about said axis,

a control means for producing a position control signal representative of a desired angular position of said device relative to said axis,

a low-resolution control counter responsive to said position control signal for producing a low-resolution output representative of the desired angular position of said device relative to said axis,

encoder means for converting the actual angular position of said device relative to said axis to an actual position signal,

means for transforming said actual position signal into a low-resolution feedback signal and a high-resolution feedback signal,

a low-resolution feedback counter responsive to said low-resolution feedback signal for producing a low-resolution output representative of the actual angular position of said device relative to said axis,

a control feedback error register for comparing the output of said low-resolution control counter and the output of said low-resolution feedback counter for producing a low-resolution position error output,

a high-resolution counter responsive to said high-resolution feedback signal for producing a high-resolution output representative of the actual angular position of said device relative to said axis,

an error encoder multiplexer for combining said low-resolution position error output and the output of said high-resolution counter to produce a position error signal, and

means for applying said position error signal to said servo motor for causing rotation of said device about said axis so as to minimize said position error signal.