SIMULTANEOUS THREE-DIMENSIONAL GEOMETRY AND COLOR TEXTURE ACQUISITION USING SINGLE COLOR CAMERA

• US 20100207938A1
• Filed: 02/18/2009
• Published: 08/19/2010
• Est. Priority Date: 02/18/2009
• Status: Active Grant

• Current Assignee: Hangzhou Conformal & Digital Technology Limited Corporation
• Original Assignee: International Press Of Boston, Inc.
• Inventors: Zhang, Song, Gu, Xiangfeng, YAU, SHING-TUNG
• Granted Patent: US 8,861,833 B2
• Time in Patent Office: Days
• US Class Current: 345/419
• CPC Class Codes: G01B 11/2513 with several lines being projected in more than one direction, e.g. grids, patterns
• CPC Class Codes: G06T 1/0007 Image acquisition
• CPC Class Codes: G06T 7/521 from laser ranging, e.g. using interferometry; from the projection of structured light

Abstract

A system for simultaneous real-time three-dimensional geometry and color texture acquisition. The system includes a system processor for generating at least three phase shifted black and white fringe patterns with a phase shift of 2 π/3, a light projector adapted to project the fringe patterns onto an object, the projector being electrically connected with the system processor, and a color camera for capturing the fringe patterns to generate at least three raw fringe images. The fringe images are used to calculate a black and white texture image which is further converted to a color image by employing a demosaicing algorithm. The fringe images are also used to calculate a wrapped phase map that is further processed to generate a continuous unwrapped phase map by employing a phase unwrapping algorithm and the unwrapped phase map is converted to co-ordinates using calibrated system parameters for point-by-point three-dimensional shape measurement.

Claims

1. A system for simultaneous real-time three-dimensional geometry and color texture acquisition of an object, comprising:

a system processor for generating at least three phase shifted black and white fringe patterns by a three-step phase shifting algorithm;

a light projector adapted to project the at least three phase shifted black and white fringe patterns onto the object, the light projector being electrically connected with the system processor; and

a color camera for capturing the at least three phase shifted black and white fringe patterns reflected from the object to generate at least three raw fringe images;

wherein the raw fringe images acquired by the color camera are processed by the system processor for simultaneous real-time three-dimensional geometry and color texture acquisition.

2. The system of claim 1 wherein the light projector is a digital light processing (DLP) projector with a resolution of 1024×

768.

3. The system of claim 1 wherein the color camera is a CMOS digital camera featuring 1024×

768 resolution, eight bit image depth, USB 2.0 interface and 22 fps maximum speed under full resolution.

4. The system of claim 1 wherein the color camera has a single imaging sensor with a Bayer mosaic filter.

5. The system of claim 1 wherein the system processor employs graphics processing unit (GPU) to assist in processing of the fringe patterns.

6. A method for simultaneous real-time three-dimensional geometry and color texture acquisition, comprising the steps of:

generating at least three phase shifted black and white fringe patterns with a phase shift of 2π

/3 by a system processor utilizing a three step phase shifting algorithm and sending the fringe patterns to a light projector;

projecting the phase shifted fringe patterns onto an object by the light projector which is electrically connected with the system processor;

capturing the phase shifted fringe patterns reflected from the object by a color camera to generate at least three raw fringe images;

calculating a wrapped phase map using the raw fringe images;

processing the wrapped phase map to generate a continuous unwrapped phase map by employing a phase unwrapping algorithm and converting the continuous unwrapped phase map to co-ordinates using calibrated system parameters for point by point three-dimensional shape measurement;

producing a black and white texture image by using the raw fringe images; and

converting the black and white texture image to a color image by employing a demosaicing algorithm.

7. The method of claim 6 wherein the phase shifted black and white fringe patterns are generated with intensity values by the three step phase shifting algorithm, the intensity values as:

I₁(x,y)=I′

(x,y)+I″

(x,y)cos [ø

(x,y)−

2π

/3]

I₂(x,y)=I′

(x,y)+I″

(x,y)cos [ø

(x,y)]

I₃(x,y)=I′

(x,y)+I″

(x,y)cos [ø

(x,y)+2π

/3]

where I′

(x, y) is an average intensity of the fringe patterns, I″

(x, y) is an intensity modulation of the fringe patterns, ø

(x, y) is a phase of the fringe patterns.

8. The method of claim 6 wherein the color camera has a single imaging sensor with a Bayer mosaic filter.

9. The method of claim 6 wherein the Bayer mosaic filter is mounted on top of the imaging sensor pixel-by-pixel thereby allowing only one of three primary colors red, green, and blue to enter into one pixel of the image sensor to form the raw fringe images.

10. The method of claim 6 wherein the raw fringe images have a filter pattern of RGBG or GRGB that represents 50% green, 25% red, and 25% blue.

11. The method of claim 6 wherein the raw fringe images acquired by the single imaging sensor have a pixel-by-pixel grayscale value.

12. The method of claim 6 wherein the wrapped phase map is generated using the raw fringe images and a phase value solved from at least three intensity values of the black and white fringe patterns, the phase value as:

13. The method of claim 6 wherein the system is calibrated with a red and blue checkerboard for estimating intrinsic and extrinsic parameters of the system.

14. The method of claim 6 wherein the black and white texture image is generated using the raw fringe images and an intensity value solved from at least three intensity values of the black and white fringe patterns, the intensity value as:

15. The method of claim 6 wherein the black and white texture image can be converted to the color image using a demosaicing algorithm.