Three dimensional imaging method and device

• US 4,627,734 A
• Filed: 01/16/1986
• Issued: 12/09/1986
• Est. Priority Date: 06/30/1983
• Status: Expired due to Term

• Current Assignee: National Research Council Canada
• Original Assignee: Canadian Patents and Development Limited
• Inventors: Rioux, Marc
• Primary Examiner(s): Rosenberger, Ra
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/819,477
• Time in Patent Office: 327 Days
• Field of Search: 356/373, 356/375, 356/376, 356/1, 350/6.7-6.9
• US Class Current: 356/607
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures
• CPC Class Codes: G01C 11/00 Photogrammetry or videogrammetry, e.g. stereogrammetry; Photographic surveying
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/4817 relating to scanning

Abstract

A three dimensional imaging system operating in accordance with the known active triangulation method employs a laser beam that is projected onto an area of a surface the profile of which is to be examined. A beam reflected from such area is received in a position sensitive detector. With synchronised scanning of the projected and detected beams by a system of mirrors, the detected position in the detector remains unchanged when the surface under examination is a flat reference plane, changing only as a measure of the degree of deviation of each examined area from such reference plane in a direction Z. The system is characterised by this basic scanning being carried out in such a way that the beams are scanned in a direction X lying in the beam plane, i.e. the plane defined by the beams, and by a further simultaneous and synchronous scanning that takes place in a direction Y. The directions X, Y and Z are all mutually perpendicular. The system has the advantage over prior systems of enabling surface profiling by means of a device that is compact, has a large field of view and can be arranged to have extremely rapid operation, i.e. a small fraction of a second to record a full image. While this speed of operation enables the system to determine the three dimensional shape of moving articles it has the advantage that it is not dependent on movement of the article to achieve full scanning.

Claims

1. In a method of determining the profile of a surface relative to a reference plane, comprising projecting a beam of radiation to strike an area of the surface and detecting a beam reflected by such surface area, portions of the projected and detected beams that intersect at said area defining a beam plane that intersects the reference plane along a direction X;

the improvement comprising synchronously scanning said beam portions in the beam plane to move in the direction X the surface area at which said beam portions intersect, whereby each detected position of the detected beam in the direction X represents a deviation of a respective said area from the reference plane in a direction Z perpendicular to the reference plane.

2. The method of claim 1, including further synchronously scanning said projected and detected beam portions relative to the reference plane in a direction Y perpendicular to both the directions X and Z.

3. The method of claim 2, wherein said radiation is coherent light.

4. An imaging device for determining the profile of a surface relative to a reference plane, comprising

(a) a source of radiation mounted for projecting a beam onto an area of the surface,

(b) a position sensitive detector mounted for detecting a beam reflected by such surface area,

(c) portions of the projected and detected beams defining a beam plane that intersects the reference plane along a direction X, and

(d) primary means for synchronously scanning said beam portions in said beam plane to move the surface area at which said beam portions intersect in the direction X, whereby respective positions in said detector in the direction X at which the detected beam is received represent deviations of respective said areas from the reference plane in a direction Z perpendicular to said reference plane.

5. The device of claim 4 including

(e) further means for synchronously scanning said portions of the projected and detected beams relative to the reference plane in a direction Y perpendicular to both said directions X and Z.

6. The device of claim 4, wherein said radiation is of a type capable of being deflected by a mirror and said primary scanning means comprises a pair of mirror surfaces located for simultaneously deflecting respective said beams, and means for rotating said mirror surfaces in synchronism.

7. The device of claim 5, wherein said mirror surfaces are facets of a multifaceted mirror mounted for rotation about an axis extending in the direction Z.

8. The device of claim 5, wherein said further scanning means comprises a further mirror and means for mounting said further mirror for rotation relative to the reference plane about an axis extending in the direction X.

9. The device of claim 7, wherein said further scanning means comprises a further mirror and means for mounting said further mirror for rotation relative to the reference plane about an axis extending in the direction X.

10. The device of claim 5, wherein said further scanning means comprises means for rotating the primary scanning means relative to the reference plane about an axis extending in the direction X.

11. The device of claim 7, wherein said further scanning means comprises means for rotating the primary scanning means relative to the reference plane about an axis extending in the direction X.

12. The device of claim 5, wherein said further scanning means comprises means for rotating said surface relative to the reference plane about an axis extending in the direction X.

13. The device of claim 7, wherein said further scanning means comprises means for rotating said surface relative to the reference plane about an axis extending in the direction X.

14. The imaging device of claim 4, including additional means for deflecting the projected beam to correspond to a predetermined profile whereby the received position of the detected beam in the detector is unchanged when said surface exhibits such predetermined profile.

15. The imaging device of claim 4, including additional means for deflecting the projected beam in accordance with a predetermined program whereby the received position of the detected beam in the detector is compensated for distortion due to a wide field of view of at least one of the primary and further scanning means.

16. The imaging device of claim 4, including a second position sensitive detector mounted for detecting a second beam reflected from the projected beam by each surface area, the second detected beam being located on the opposite side of the protected beam from the first detected beam, said primary and further scanning means acting on the second detected beam in the same manner as on the first detected beam.

19. The device of claim 4, wherein said radiation is of a type capable of being deflected by a mirror and said primary scanning means comprises a thin, flat member having mirror surfaces on opposite major faces thereof respectively located for simultaneously deflecting respective said beams, and means for oscillating said member.

20. The device of claim 19, including further means for synchronously scanning said portions of the projected and detected beams relative to the reference plane in a direction Y perpendicular to both said directions X and Z.

17. An imaging device for determining the profile of a surface in a direction Z relative to a reference plane, comprising

(a) a laser for projecting a beam substantially in the direction Z,

(b) a position sensitive detector mounted for receiving a detected beam extending substantially in the direction Z,

(c) a pyramidal mirror rotatably mounted about an axis extending substantially in the direction Z and having facets in the paths of said beams for deflecting said paths substantially into a direction X perpendicular to the direction Z,

(d) flat mirrors located in the paths of the deflected beams for further deflecting said paths substantially into a direction Y perpendicular to both the directions X and Z,

(e) a further flat mirror located in the paths of the beams deflected substantially into the direction Y for still further deflecting said paths substantially into the direction Z for intersection at an area of the said surface at which the detected beam is reflected from the projected beam, such still further deflected portions of the beams defining a beam plane intersecting the reference plane along the direction X,

(f) means for rotating said pyramidal mirror for synchronously scanning said beams and hence scanning said intersection in the direction X whereby respective positions in the detector in the direction X at which the detected beam is received represent deviations of respective said areas from the reference plane in the direction Z, and

(g) means for rotating said further mirror about an axis extending in the direction X whereby to scan synchronously said still further deflected portions of the beams and hence said intersection in the direction Y.

18. An imaging device for determining the profile of a surface in a direction Z relative to a reference plane, comprising

(a) a laser for projecting a beam substantially in a direction X perpendicular to the direction Z,

(b) a position sensitive detector mounted for receiving a detected beam extending substantially in the direction X,

(c) a plurality of flat mirror surfaces each rotatably mounted about an axis extending in the direction Z and respectively located in the paths of said beams for deflecting said paths substantially into a direction Y perpendicular to both the directions X and Z,

(d) a further flat mirror located in the paths of the beams deflected substantially into the direction Y for further deflecting said paths substantially into the direction Z for intersection at an area of said surface at which the detected beam is reflected from the projected beam, such further deflected portions of the beams defining a beam plane intersecting the reference plane along the direction X,

(e) means for synchronously rotating said mirror surfaces for synchronously scanning said beams and hence scanning said intersection in the direction X, whereby respective positions in the detector in the direction X at which the detected beam is received represent deviations of respective said areas from the reference plane in the direction Z, and means for rotating said further mirror about an axis extending in the direction X whereby to scan synchronously said further deflected portions of the beams and hence said intersection in the direction Y.

21. An imaging device for determining the profile of a surface in a direction Z relative to a reference plane, comprising

(a) a thin, flat member having mirror surfaces on opposite major faces thereof,

(b) means for projecting a laser beam at one of said mirror surfaces,

(c) a position sensitivc detector mounted for receiving a detected beam from the other of said mirror surfaces,

(d) further mirror means located in the paths of beams deflected by said mirror surfaces for further deflecting said paths substantially into the direction Z for intersection at an area of the said surface at which the detected beam is reflected from the projected beam, portions of such further deflected beam paths defining a beam plane intersecting the reference plane alohg a direction X perpendicular to the direction Z, and

(e) means for oscillating said member and hence scanning said intersection in the direction X whereby respective positions in the detector in the direction X at which the detected beam is received represent deviations of respective said areas from the reference plane in the direction Z.

22. A device according to claim 21, wherein said further mirror means include means for synchronously scanning said portions of the beam paths relative to the reference plane in a direction Y perpendicular to both said directions X and Z.