Apparatus for determining the distances of points on a surface from a reference axis

• US 4,937,445 A
• Filed: 09/23/1987
• Issued: 06/26/1990
• Est. Priority Date: 09/24/1986
• Status: Expired

• Current Assignee: Softac Systems Ltd. (BLGI, Inc.)
• Original Assignee: Softac Systems Ltd. (BLGI, Inc.)
• Inventors: Stewart, Donald, Leong, Kenneth
• Primary Examiner(s): Westin, Edward P.
• Application Number:
  US07/100,332
• Time in Patent Office: 1,007 Days
• Field of Search: 250/560, 250/561, 250/578, 250/237 G, 356/376, 356/377, 356/379, 356/381, 356/383, 356/384, 356/385, 358/107, 364/550, 364/556
• US Class Current: 250/237.00G
• CPC Class Codes: G01B 11/00 Measuring arrangements characterised by the use of optical techniques
• CPC Class Codes: G01B 11/2545 with one projection direction and several detection directions, e.g. stereo

Abstract

An apparatus for monitoring and determining the distances of points on a surface from a reference axis includes a light source, such as a laser, for projecting a main beam of light of relatively small diameter along an axis. A device, such as a diffraction grating, is provided for splitting the main beam of light into a plurality of discrete fractional beams of light. A further component, such as a diverging lens, angularly displaces the fractional beams relative to each other so the beams extend along a common plane towards a position for an object. Light reflected from the surface is projected onto a linear photodetector, the positions where the reflected fractional beams strike the linear photodetector being related to the distance from a reference axis to the points on the object where the fractional beams are reflected. Preferably there is a light gathering device such as a converging lens system for gathering the fractional light beams reflected off the object and for projecting real images thereof onto the photodetector.

Claims

1. An optical apparatus, comprising:

light projecting means for projecting a main beam of light of relatively small diameter along an axis;

beam splitting means positioned along the axis for splitting the beam into a plurality of discrete fractional beams of light;

means for angularly displacing the fractional beams relative to each other so the beams extend along a common plane towards a position for an object; and

photodetector array means having a plurality of pre-defined zones positioned to receive respective individual fractional beams after the fractional beams are reflected off the object.

2. An apparatus as claimed in claim 1 wherein said plurality of zones are adjacent each other.

3. An apparatus as claimed in claim 1 wherein said zones are arranged in a row on said sensor.

4. An apparatus as claimed in claim 1 wherein said zones are arranged contiguously on said sensor.

5. An apparatus for monitoring and determining the distances of points on a surface of a strip of material from a pre-determined reference axis, comprising:

means for projecting a stationary light beam of small diameter along an optical axis towards the surface;

means along the axis for dividing the stationary beam into a plurality of angularly spaced apart smaller beams directed towards the surface and extending along a common plane intersecting with the surface to produce a plurality of linearly spaced apart spots of light on the surface;

first means for gathering reflected light from the points on the surface and projecting real images of the spots onto a straight line along a first photodetector plane; and

first linear photodetector means having a plurality of pre-defined zones positioned along the line extending along the first photodetector plane to receive respective individual images of the spots, the first linear photodetector means providing a quantified signal output representing the positions of the images in respective zones along the line representing the positions on the strip surface where the spots of light occur relative to the reference axis.

6. An apparatus as claimed in claim 5, further comprising means for scanning the zones of the image sensor sequentially to detect the positions of the real images of the spots of light within each of the zones.

7. An apparatus as claimed in claim 6 wherein the zones have a plurality of cells and the means for scanning the zones of the image sensor comprises an electronic circuit for scanning the pixels in each zone until a center cell corresponding to the center of the real image of the spot within the zone is located.

8. An apparatus for monitoring and determining the distances of points on a surface of a strip of material from a predetermined reference axis, comprising:

means for projecting a stationary light beam of small diameter along an optical axis towards the surface;

means along the axis for dividing the stationary beam into a plurality of angularly spaced-apart smaller beams directed towards the surface and extending along a common plane intersecting with the surface to produce a plurality of linearly spaced apart spots of light on the surface;

first means for gathering reflected light from the points on the surface and projecting real images of the spots onto a straight line along a first photodetector plane;

first linear photodetector means for determining the positions of the real images of the spots along the line extending along the first photodetector plane, the first linear photodetector means including a linear charge coupled image sensor having a plurality of adjacent zones, each said zone being positioned to receive the real image of one of the spots of light, the first linear photodetector means providing a quantified signal output representing the positions of the images along the line representing the positions on the strip surface where the spots of light occur relative to the reference axis.

9. An apparatus as claimed in claim 8, wherein the means for projecting is a laser.

10. An apparatus as claimed in claim 8, wherein the means for dividing is a fibre grating.

11. An apparatus as claimed in claim 8, wherein the means for dividing is a diffraction grating.

12. An apparatus as claimed in claim 8, wherein the means for gathering is a converging lens system.

13. An apparatus as claimed in claim 8, further comprising second means for gathering reflected light from the spots on the surface and projecting real images of the spots onto a straight line along a second photodetector plane;

and

second linear photodetector means for determining the positions of the real images of the spots along the line extending along the second photodetector plane, the second linear photodetector means providing a quantified signal output representing the positions of the images along the second line representing the positions on the strip surface where the spots of light occur relative to the reference axis;

the first means for gathering and the first linear photodetector means being positioned to gather and detect smaller beams reflected to a first side of the stationary light beam and the second linear photodetector being positioned to gather and detect smaller beams reflected to a second side of the stationary light beam.

14. An apparatus as claimed in claim 8, further comprising means for scanning the zones of the image sensor sequentially to detect the positions of the real images of the spots of light within each of the zones.

15. An apparatus as claimed in claim 14, wherein the means for scanning the zones of the image sensor comprises an electronic circuit.

16. An optical apparatus comprising:

light projecting means for projecting a main beam of light of relatively small diameter along an axis;

beam splitting means positioned along the axis for splitting the beam into a plurality of discrete fractional beams of light;

means for angularly displacing the fractional beams relative to each other so the beams extend along a common plane towards a position for an object;

photodetector array means positioned to receive the fractional beams after the fractional beams are reflected off the object, the photodetector array means having a plurality of adjacent zones;

light gathering means for gathering the fractional beams of light reflected off the object and for projecting the real image of each fractional beam onto a different said zone; and

means for scanning each of the zones sequentially to determine the positions of each of the real images within each of the zones.

17. An apparatus as claimed in claim 16, wherein the beam splitting means is a fibre grating.

18. An apparatus as claimed in claim 16, wherein the beam splitting means is a diffraction grating.

19. An apparatus as claimed in claim 16, wherein the light gathering means is a lens system.

20. An apparatus as claimed in claim 16, wherein the photodetector array means comprises a linear charge coupled image sensor.