Method and apparatus for determining the coordinates of an object

• US 6,369,879 B1
• Filed: 05/04/2001
• Issued: 04/09/2002
• Est. Priority Date: 10/24/2000
• Status: Expired due to Fees

• Current Assignee: Los Alamos National Security LLC (Government of the United States of America)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Pedersen, Paul S.
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): ANDREA, BRIAN K
• Application Number:
  US09/851,188
• Time in Patent Office: 340 Days
• Field of Search: 356/3-1-, 356/141.1
• US Class Current: 356/3.01
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures

Abstract

A simplified method and related apparatus are described for determining the location of points on the surface of an object by varying, in accordance with a unique sequence, the intensity of each illuminated pixel directed to the object surface, and detecting at known detector pixel locations the intensity sequence of reflected illumination from the surface of the object whereby the identity and location of the originating illuminated pixel can be determined. The coordinates of points on the surface of the object are then determined by conventional triangulation methods.

Claims

1. An apparatus for determining the coordinates of points on the surface of an object, comprising:

(a) a modulated light source having pixels whose light intensity output may be individually modulated, wherein the light source is directed toward the object;

(b) an image detector having a plurality of pixels for registering light reflected from the surface of the object and outputting a light intensity value from each pixel; and

(c) means for determining the coordinates of points on the surface of the object wherefrom pixels of light are reflected from the surface of the object, wherein the determination is responsive to the relative location of pixels registered on the imaging detector such that a sequence of intensity values detected by pixels of the image detector are correlated with a unique signature of light intensity values transmitted by pixels of the light source from which the location of the associated point of reflection from the surface of the object is determined by triangulation from known locations of the image detector pixels and light source pixels.

2. The apparatus as recited in claim 1, wherein the coordinate determining means comprises a computer system configured for controlling the modulated light source and that receives pixel intensity information from the image detector such that a correlation is made relating a sequence of modulated light intensity patterns with received light intensity patterns to determine object coordinates.

3. An apparatus for determining the coordinates of points on the surface of an object by sensing reflected illumination intensities, comprising:

(a) means for emitting an illuminating beam toward an object, the beam having an area defined by a plurality of pixels;

(b) means for modulating the intensity of individual pixels forming the illuminating beam;

(c) means for detecting the illumination intensity of the illuminating beam which has been reflected from points on the surface of the object; and

(d) means for correlating the position of each pixel at the point of modulation with the position of detected pixel illumination intensities from a unique signature of each one of the plurality of pixels forming the illuminating beam, from which the coordinates of the object may be resolved by triangulation.

4. The apparatus as recited in claim 3, wherein the emitting means comprises a high-intensity illumination source.

5. The apparatus as recited in claim 3, wherein the modulating means comprises a transmissive LCD array having pixels whose transmissivity may be varied.

6. The apparatus as recited in claim 3, wherein the detecting means comprises a CCD camera.

7. The apparatus as recited in claim 3, wherein the resolving means comprises a computer system configured for controlling the intensity of the illuminating pixels and receiving pixel intensity information from the detecting means, and further configured for determining the coordinates of the object by triangulation.

8. An apparatus for determining the coordinates of points on the surface of an illuminated object by sensing the intensity of reflected illumination, comprising:

(a) a source of illumination having a plurality of pixels whose intensity I_n may be individually modulated Q times in a sequence that uniquely identifies each one of the plurality of pixels;

(b) an image sensor positioned to receive at a plurality of known locations the source of illumination as it reflects from the object; and

(c) a computer processor coupled to the intensity modulator and the image sensor, the computer processor correlating sequences of intensity values received at image sensor locations with sequences of intensity values from the source of illumination from which the coordinates of object points may then be determined by triangulation.

9. The apparatus as recited in claim 8, wherein pixel intensities are modulated a minimum of Q times, where Q=ceiling(log_N(P)), P is the number of pixels of the source of illumination and N is number of intensity levels.

10. The apparatus as recited in claim 8, wherein the intensity of the pixels may be modulated by passing a beam of illumination through an intensity modulator, such as an LCD, which is capable of selectively transmitting all or a portion of the wavelength constituents of the illumination.

11. The apparatus as recited in claim 9, wherein the sequence of intensities I_n, specified for a point P(x₀,y₀) at which each pixel u_i (0≦

i≦

P−

1) is intensity modulated according to a unique signature (d_i,0,d_i,1, . . . ,d<sub>i,Q−

1</sub>), where d_i,k is selected from the set {0,1, . . . ,N−

1}.

12. The apparatus as recited in claim 11, wherein the intensity modulation transmits C colors and each color can be transmitted at L intensity levels so that N=CL.

13. A method for determining the coordinates of points on an object surface, comprising:

projecting a light from an optical intensity modulator onto an object whose coordinates are to be determined, wherein optical intensity is modulated to create a signature of light intensity patterns that uniquely identifies each pixel forming the optical intensity modulator;

receiving the light which has been reflected from the object onto discrete locations of an imaging device; and

determining the coordinates on the object, wherein the determination correlates the discrete locations on the imaging device with specific ones of the intensity modulator pixels from the detected signature from specific intensity modulator pixels, wherefrom the coordinates of points on the object surface are then determined by triangulation.

14. A method of obtaining object coordinates by sensing reflected illumination, comprising:

illuminating an object with a beam of electromagnetic radiation having a plurality of pixels located at a point of intensity modulation whose intensity is individually modulated in a sequence that provides a unique signature for each pixel;

registering the location and intensity of the electromagnetic radiation reflected from the object at a sensor in response to the intensity sequence from each of the modulated pixels;

determining the position for each pixel at the point of intensity modulation from intensity sequences registered at the discrete locations on the sensor; and

determining object coordinates from the discrete sensor locations and correlated pixels at the point of intensity modulation by geometric triangulation.

15. The method as recited in claim 14, wherein the intensity modulation generates a sequence of intensities I_n, specified for a point P(x₀,y₀) at which each pixel u_i (0≦

i≦

P−

1) is intensity modulated according to a unique signature (d_i,0,d_i,1, . . . ,d<sub>i,Q−

1</sub>), where d_i,k is selected from the set {0,1, . . . ,N−

1}.